Device and method for laser beam machining
Abstract
[Task] To provide a laser processing apparatus capable of precisely cutting an object to be machined without melting or cracking off the planned cutting line on the surface of the object to be machined.
Solution.The peak power density of the laser light source 101 that emits pulsed laser light with a pulse width of 1 μs or less, the power adjusting unit 401 that adjusts the magnitude of the power of the pulsed laser light, and the focusing point P of the pulsed laser light is 1 × 10.8(W / cm2) The lens selection mechanism 403 including a plurality of condensing lenses that condense the pulsed laser light as described above, and the condensing point P of the pulsed laser light condensed by the condensing lens are inside the object 1 to be processed. The Z-axis stage 113 is provided, and the X (Y) -axis stage 109 (111) that relatively moves the condensing point P along the planned cutting line 5 of the object 1 to be processed is provided. The numerical apertures of the optical systems including the focusing lenses 105a to 105c are different. By adjusting the numerical aperture and the magnitude of the power of the pulsed laser beam, the dimensions of the modified spot formed inside the workpiece 1 are controlled. Dimensions are displayed before laser machining.
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17 claims: 12 independent, 5 dependent
- 1【特許請求の範囲】 【請求項1】 パルス幅が1μs以下のパルスレーザ光を出射するレーザ光源と、 パルスレーザ光のパワー大きさの入力に基づいて前記レーザ光源から出射されるパルスレーザ光のパワーの大きさを調節するパワー調節手段と、 前記レーザ光源から出射されたパルスレーザ光の集光点のピークパワー密度が1×10 8 (W/cm 2 )以上になるようにパルスレーザ光を集光する集光手段と、 前記集光手段により集光されたパルスレーザ光の集光点を加工対象物の内部に合わせる手段と、 前記加工対象物の切断予定ラインに沿ってパルスレーザ光の集光点を相対的に移動させる移動手段と、 を備え、 前記内部に集光点を合わせて1パルスのパルスレーザ光を前記加工対象物に照射することにより、前記内部に1つの改質スポットが形成され、 前記パワー調節手段により調節されるパルスレーザ光のパワーの大きさと改質スポットの寸法との相関関係を予め記憶した相関関係記憶手段と、 前記入力されたパルスレーザ光のパワーの大きさに基づいて、この大きさのパワーで形成される改質スポットの寸法を前記相関関係記憶手段から選択する寸法選択手段と、 前記寸法選択手段により選択された改質スポットの寸法を表示する寸法表示手段と、 を備える、レーザ加工装置。
- 2【請求項2】 パルス幅が1μs以下のパルスレーザ光を出射するレーザ光源と、 前記レーザ光源から出射されたパルスレーザ光の集光点のピークパワー密度が1×10 8 (W/cm 2 )以上になるようにパルスレーザ光を集光する集光用レンズと、 開口数の大きさの入力に基づいて前記集光用レンズを含む光学系の開口数の大きさを調節する開口数調節手段と、 前記集光用レンズにより集光されたパルスレーザ光の集光点を加工対象物の内部に合わせる手段と、 前記加工対象物の切断予定ラインに沿ってパルスレーザ光の集光点を相対的に移動させる移動手段と、 を備え、 前記内部に集光点を合わせて1パルスのパルスレーザ光を前記加工対象物に照射することにより、前記内部に1つの改質スポットが形成され、 前記開口数調節手段により調節される開口数の大きさと改質スポットの寸法との相関関係を予め記憶した相関関係記憶手段と、 前記入力された開口数の大きさに基づいて、この大きさの開口数で形成される改質スポットの寸法を前記相関関係記憶手段から選択する寸法選択手段と、 前記寸法選択手段により選択された改質スポットの寸法を表示する寸法表示手段と、 を備える、レーザ加工装置。
- 3【請求項3】 パルス幅が1μs以下のパルスレーザ光を出射するレーザ光源と、 前記レーザ光源から出射されたパルスレーザ光の集光点のピークパワー密度が1×10 8 (W/cm 2 )以上になるようにパルスレーザ光を集光する集光用レンズを複数含みかつ前記複数の集光用レンズを選択可能なレンズ選択手段と、 を備え、 前記複数の集光用レンズを含む光学系はそれぞれ開口数が異なり、 前記レンズ選択手段で選択された集光用レンズにより集光されたパルスレーザ光の集光点を加工対象物の内部に合わせる手段と、 前記加工対象物の切断予定ラインに沿ってパルスレーザ光の集光点を相対的に移動させる移動手段と、 を備え、 前記内部に集光点を合わせて1パルスのパルスレーザ光を前記加工対象物に照射することにより、前記内部に1つの改質スポットが形成され、 前記複数の集光用レンズを含む光学系の開口数の大きさと改質スポットの寸法との相関関係を予め記憶した相関関係記憶手段と、 選択された前記集光用レンズを含む光学系の開口数の大きさに基づいて、この大きさの開口数で形成される改質スポットの寸法を前記相関関係記憶手段から選択する寸法選択手段と、 前記寸法選択手段により選択された改質スポットの寸法を表示する寸法表示手段と、 を備える、レーザ加工装置。
- 4【請求項4】 パルス幅が1μs以下のパルスレーザ光を出射するレーザ光源と、 パルスレーザ光のパワー大きさの入力に基づいて前記レーザ光源から出射されるパルスレーザ光のパワーの大きさを調節するパワー調節手段と、 前記レーザ光源から出射されたパルスレーザ光の集光点のピークパワー密度が1×10 8 (W/cm 2 )以上になるようにパルスレーザ光を集光する集光用レンズと、 開口数の大きさの入力に基づいて前記集光用レンズを含む光学系の開口数の大きさを調節する開口数調節手段と、 前記集光用レンズにより集光されたパルスレーザ光の集光点を加工対象物の内部に合わせる手段と、 前記加工対象物の切断予定ラインに沿ってパルスレーザ光の集光点を相対的に移動させる移動手段と、 を備え、 前記内部に集光点を合わせて1パルスのパルスレーザ光を前記加工対象物に照射することにより、前記内部に1つの改質スポットが形成され、 前記パワー調節手段により調節されるパルスレーザ光のパワーの大きさ及び前記開口数調節手段により調節される開口数の大きさの組と改質スポットの寸法との相関関係を予め記憶した相関関係記憶手段と、 前記入力されたパルスレーザ光のパワーの大きさに及び前記入力された開口数の大きさに基づいてこれらの大きさで形成される改質スポットの寸法を前記相関関係記憶手段から選択する寸法選択手段と、 前記寸法選択手段により選択された改質スポットの寸法を表示する寸法表示手段と、 を備える、レーザ加工装置。
- 5【請求項5】 パルス幅が1μs以下のパルスレーザ光を出射するレーザ光源と、 パルスレーザ光のパワー大きさの入力に基づいて前記レーザ光源から出射されるパルスレーザ光のパワーの大きさを調節するパワー調節手段と、 前記レーザ光源から出射されたパルスレーザ光の集光点のピークパワー密度が1×10 8 (W/cm 2 )以上になるようにパルスレーザ光を集光する集光用レンズを複数含みかつ前記複数の集光用レンズを選択可能なレンズ選択手段と、 を備え、 前記複数の集光用レンズを含む光学系はそれぞれ開口数が異なり、 前記レンズ選択手段で選択された前記集光用レンズにより集光されたパルスレーザ光の集光点を加工対象物の内部に合わせる手段と、 前記加工対象物の切断予定ラインに沿ってパルスレーザ光の集光点を相対的に移動させる移動手段と、 を備え、 前記内部に集光点を合わせて1パルスのパルスレーザ光を前記加工対象物に照射することにより、前記内部に1つの改質スポットが形成され、 前記パワー調節手段により調節されるパルスレーザ光のパワーの大きさ及び前記複数の集光用レンズを含む光学系の開口数の大きさの組と改質スポットの寸法との相関関係を予め記憶した相関関係記憶手段と、 前記入力されたパルスレーザ光のパワーの大きさに及び選択された前記集光用レンズを含む光学系の開口数の大きさに基づいて、これらの大きさで形成される改質スポットの寸法を前記相関関係記憶手段から選択する寸法選択手段と、 前記寸法選択手段により選択された改質スポットの寸法を表示する寸法表示手段と、 を備える、レーザ加工装置。
- 6【請求項6】 前記寸法選択手段で選択された寸法の改質スポットの画像を作成する画像作成手段と、 前記画像作成手段により作成された画像を表示する画像表示手段と、 を備える、請求項1~5のいずれかに記載のレーザ加工装置。
- 7【請求項7】 パルス幅が1μs以下のパルスレーザ光を出射するレーザ光源と、 前記レーザ光源から出射されるパルスレーザ光のパワーの大きさを調節するパワー調節手段と、 前記レーザ光源から出射されたパルスレーザ光の集光点のピークパワー密度が1×10 8 (W/cm 2 )以上になるようにパルスレーザ光を集光する集光手段と、 前記集光手段により集光されたパルスレーザ光の集光点を加工対象物の内部に合わせる手段と、 前記加工対象物の切断予定ラインに沿ってパルスレーザ光の集光点を相対的に移動させる移動手段と、 を備え、 前記内部に集光点を合わせて1パルスのパルスレーザ光を前記加工対象物に照射することにより、前記内部に1つの改質スポットが形成され、 前記パワー調節手段により調節されるパルスレーザ光のパワーの大きさと改質スポットの寸法との相関関係を予め記憶した相関関係記憶手段と、 改質スポットの寸法の入力に基づいて、この寸法に形成できるパルスレーザ光のパワーの大きさを前記相関関係記憶手段から選択するパワー選択手段と、 を備え、 前記パワー調節手段は、前記パワー選択手段により選択されたパワーの大きさとなるように前記レーザ光源から出射されるパルスレーザ光のパワーの大きさを調節する、レーザ加工装置。
- 8【請求項8】 パルス幅が1μs以下のパルスレーザ光を出射するレーザ光源と、 前記レーザ光源から出射されたパルスレーザ光の集光点のピークパワー密度が1×10 8 (W/cm 2 )以上になるようにパルスレーザ光を集光する集光用レンズと、 前記集光用レンズを含む光学系の開口数の大きさを調節する開口数調節手段と、 前記集光用レンズにより集光されたパルスレーザ光の集光点を加工対象物の内部に合わせる手段と、 前記加工対象物の切断予定ラインに沿ってパルスレーザ光の集光点を相対的に移動させる移動手段と、 を備え、 前記内部に集光点を合わせて1パルスのパルスレーザ光を前記加工対象物に照射することにより、前記内部に1つの改質スポットが形成され、 前記開口数調節手段により調節される開口数の大きさと改質スポットの寸法との相関関係を予め記憶した相関関係記憶手段と、 改質スポットの寸法の入力に基づいて、この寸法に形成できる開口数の大きさを前記相関関係記憶手段から選択する開口数選択手段と、 を備え、 前記開口数調節手段は、前記開口数選択手段により選択された開口数の大きさとなるように前記集光用レンズを含む光学系の開口数の大きさを調節する、レーザ加工装置。
- 9【請求項9】 パルス幅が1μs以下のパルスレーザ光を出射するレーザ光源と、 前記レーザ光源から出射されたパルスレーザ光の集光点のピークパワー密度が1×10 8 (W/cm 2 )以上になるようにパルスレーザ光を集光する集光用レンズを複数含みかつ前記複数の集光用レンズを選択可能なレンズ選択手段と、 を備え、 前記複数の集光用レンズを含む光学系はそれぞれ開口数が異なり、 前記レンズ選択手段で選択された前記集光用レンズにより集光されたパルスレーザ光の集光点を加工対象物の内部に合わせる手段と、 前記加工対象物の切断予定ラインに沿ってパルスレーザ光の集光点を相対的に移動させる移動手段と、 を備え、 前記内部に集光点を合わせて1パルスのパルスレーザ光を前記加工対象物に照射することにより、前記内部に1つの改質スポットが形成され、 前記複数の集光用レンズの開口数の大きさと改質スポットの寸法との相関関係を予め記憶した相関関係記憶手段と、 改質スポットの寸法の入力に基づいて、この寸法に形成できる開口数の大きさを前記相関関係記憶手段から選択する開口数選択手段と、 を備え、 前記レンズ選択手段は、前記開口数選択手段により選択された開口数の大きさとなるように前記複数の集光用レンズの選択をする、レーザ加工装置。
- 10【請求項10】 パルス幅が1μs以下のパルスレーザ光を出射するレーザ光源と、 前記レーザ光源から出射されるパルスレーザ光のパワーの大きさを調節するパワー調節手段と、 前記レーザ光源から出射されたパルスレーザ光の集光点のピークパワー密度が1×10 8 (W/cm 2 )以上になるようにパルスレーザ光を集光する集光用レンズと、 前記集光用レンズを含む光学系の開口数の大きさを調節する開口数調節手段と、 前記集光用レンズにより集光されたパルスレーザ光の集光点を加工対象物の内部に合わせる手段と、 前記加工対象物の切断予定ラインに沿ってパルスレーザ光の集光点を相対的に移動させる移動手段と、 を備え、 前記内部に集光点を合わせて1パルスのパルスレーザ光を前記加工対象物に照射することにより、前記内部に1つの改質スポットが形成され、 前記パワー調節手段により調節されるパルスレーザ光のパワーの大きさ及び前記開口数調節手段により調節される開口数の大きさの組と改質スポットの寸法との相関関係を予め記憶した相関関係記憶手段と、 改質スポットの寸法の入力に基づいて、この寸法に形成できるパワー及び開口数の大きさの組を前記相関関係記憶手段から選択する組選択手段と、 を備え、 前記パワー調節手段及び前記開口数調節手段は、前記組選択手段により選択されたパワー及び開口数の大きさとなるように前記レーザ光源から出射されるパルスレーザ光のパワーの大きさ及び前記集光用レンズを含む光学系の開口数の大きさを調節する、レーザ加工装置。
- 11【請求項11】 パルス幅が1μs以下のパルスレーザ光を出射するレーザ光源と、 前記レーザ光源から出射されるパルスレーザ光のパワーの大きさを調節するパワー調節手段と、 前記レーザ光源から出射されたパルスレーザ光の集光点のピークパワー密度が1×10 8 (W/cm 2 )以上になるようにパルスレーザ光を集光する集光用レンズを複数含みかつ前記複数の集光用レンズを選択可能なレンズ選択手段と、 を備え、 前記複数の集光用レンズを含む光学系はそれぞれ開口数が異なり、 前記レンズ選択手段で選択された前記集光用レンズにより集光されたパルスレーザ光の集光点を加工対象物の内部に合わせる手段と、 前記加工対象物の切断予定ラインに沿ってパルスレーザ光の集光点を相対的に移動させる移動手段と、 を備え、 前記内部に集光点を合わせて1パルスのパルスレーザ光を前記加工対象物に照射することにより、前記内部に1つの改質スポットが形成され、 前記パワー調節手段により調節されるパルスレーザ光のパワーの大きさ及び前記複数の集光用レンズの開口数の大きさの組と改質スポットの寸法との相関関係を予め記憶した相関関係記憶手段と、 改質スポットの寸法の入力に基づいて、この寸法に形成できるパワー及び開口数の大きさの組を前記相関関係記憶手段から選択する組選択手段と、 を備え、 前記パワー調節手段及び前記レンズ選択手段は、前記組選択手段により選択されたパワー及び開口数の大きさとなるように前記レーザ光源から出射されるパルスレーザ光のパワーの大きさの調節及び前記複数の集光用レンズの選択をする、レーザ加工装置。
- 12【請求項12】 前記パワー選択手段により選択されたパワーの大きさを表示する表示手段を備える、請求項7記載のレーザ加工装置。
- 13【請求項13】 前記開口数選択手段により選択された開口数の大きさを表示する表示手段を備える、請求項8又は9記載のレーザ加工装置。
- 14【請求項14】 前記組選択手段により選択された組のパワーの大きさ及び開口数の大きさを表示する表示手段を備える、請求項10又は11記載のレーザ加工装置。
- 15【請求項15】 前記切断予定ラインに沿って前記加工対象物の前記内部に形成された複数の前記改質スポットにより改質領域が規定され、 前記改質領域は、前記内部においてクラックが発生した領域であるクラック領域、前記内部において溶融処理した領域である溶融処理領域及び前記内部において屈折率が変化した領域である屈折率変化領域のうち少なくともいずれか一つを含む、請求項1~14のいずれかに記載のレーザ加工装置。
- 16【請求項16】 パルスレーザ光の集光点を加工対象物の内部に合わせて、前記加工対象物にパルスレーザ光を照射することにより、前記加工対象物の切断予定ラインに沿って前記加工対象物の内部に多光子吸収による改質領域を形成する第1工程と、 パルスレーザ光のパワーを前記第1工程より大きく又は小さくなるように調節し、かつパルスレーザ光の集光点を前記加工対象物の内部に合わせて、前記加工対象物にパルスレーザ光を照射することにより、前記加工対象物の他の切断予定ラインに沿って前記加工対象物の内部に多光子吸収による他の改質領域を形成する第2工程と、 を備える、レーザ加工方法。
- 17【請求項17】 パルスレーザ光の集光点を加工対象物の内部に合わせて、前記加工対象物にパルスレーザ光を照射することにより、前記加工対象物の切断予定ラインに沿って前記加工対象物の内部に多光子吸収による改質領域を形成する第1工程と、 パルスレーザ光を集光する集光用レンズを含む光学系の開口数を前記第1工程より大きく又は小さくなるように調節し、かつパルスレーザ光の集光点を前記加工対象物の内部に合わせて、前記加工対象物にパルスレーザ光を照射することにより、前記加工対象物の他の切断予定ラインに沿って前記加工対象物の内部に多光子吸収による他の改質領域を形成する第2工程と、 を備える、レーザ加工方法。
Independent claims17
337 paragraphs in 1 section, as filed
Description: TECHNICAL FIELD [Detailed description of the invention]
【0001】
[Technical field to which the invention belongs]
The present invention relates to a laser processing apparatus and a laser processing method used for cutting an object to be processed such as a semiconductor material substrate, a piezoelectric material substrate, and a glass substrate.
【0002】
[Conventional technology]
Cutting is one of the laser applications, and the general cutting by laser is as follows. For example, a portion to be cut of an object to be processed such as a semiconductor wafer or a glass substrate is irradiated with laser light having a wavelength absorbed by the object to be processed, and the portion to be cut by absorption of the laser beam is directed from the front surface to the back surface of the object to be processed. The heating and melting are allowed to proceed to cut the object to be processed. However, in this method, the periphery of the region to be cut on the surface of the object to be processed is also melted. Therefore, when the object to be processed is a semiconductor wafer, among the semiconductor elements formed on the surface of the semiconductor wafer, the semiconductor elements located around the region may be melted.
【0003】
[Problems to be Solved by the Invention]
As a method for preventing the surface of the object to be processed from melting, for example, there is a laser cutting method disclosed in JP-A-2000-219528 and JP-A-2000-15467. In the cutting methods of these publications, the cut portion of the work target is heated by a laser beam and the work target is cooled to generate a thermal shock at the cut portion of the work target to generate the work target. Disconnect.
【0004】
However, in the cutting methods of these publications, if the thermal shock generated on the object to be processed is large, the surface of the object to be processed may not be cracked off the planned cutting line or to a portion not irradiated with the laser. The necessary cracks may occur. Therefore, precision cutting cannot be performed by these cutting methods. In particular, when the object to be processed is a semiconductor wafer, a glass substrate on which a liquid crystal display device is formed, or a glass substrate on which an electrode pattern is formed, the semiconductor chip, the liquid crystal display device, and the electrode pattern may be damaged by this unnecessary cracking. is there. Further, since the average input energy is large in these cutting methods, the thermal damage given to the semiconductor chip or the like is also large.
【0005】
An object of the present invention is to provide a laser processing apparatus and a laser processing method that do not generate unnecessary cracks on the surface of an object to be processed and the surface of the object is not melted.
【0006】
[Means for solving problems]
The laser processing apparatus according to the present invention has a laser light source that emits a pulsed laser beam having a pulse width of 1 μs or less, and a large power of the pulsed laser beam emitted from the laser light source based on an input of the power magnitude of the pulsed laser beam. The peak power density of the power adjusting means for adjusting the pressure and the focusing point of the pulsed laser light emitted from the laser light source is 1 × 10.<sup>8</sup>(W / cm<sup>2</sup>) A means for condensing the pulsed laser light so as to be as described above, a means for aligning the condensing point of the pulsed laser light collected by the condensing means with the inside of the object to be processed, and a plan for cutting the object to be processed. A moving means for relatively moving the focusing point of the pulsed laser light along the line is provided, and the focusing point is aligned with the inside of the object to be processed to irradiate the object to be processed with 1-pulse pulsed laser light. A correlation storage means that stores in advance the correlation between the magnitude of the power of the pulsed laser beam adjusted by the power adjusting means and the dimensions of the modified spots is formed inside the object to be processed. A dimension selection means for selecting the dimension of the reforming spot formed by the power of this magnitude based on the magnitude of the power of the input pulsed laser light from the correlation storage means, and a modification selected by the dimension selection means. It is characterized by comprising a dimension display means for displaying the dimensions of a spot.
【0007】
According to the laser processing apparatus according to the present invention, the focusing point of the pulsed laser light is aligned with the inside of the object to be processed, and the peak power density at the focusing point is 1 × 10.<sup>8</sup>(W / cm<sup>2</sup>) Or more and the pulse width is 1 μs or less, the pulsed laser beam can be applied to the object to be processed. Therefore, when a pulsed laser beam is applied to a machined object using the laser processing apparatus according to the present invention, a phenomenon called multiphoton absorption occurs inside the machined object, and a modified region is formed inside the machined object. Will be done. If there is some starting point at the cutting point of the work object, the work object can be cut with a relatively small force. Therefore, the workpiece processed by the laser processing apparatus according to the present invention can be cut by splitting or cracking along the planned cutting line starting from the modified region. Therefore, since the object to be processed can be cut with a relatively small force, the object to be processed can be cut without causing unnecessary cracks off the planned cutting line on the surface of the object to be processed.
【0008】
Further, according to the laser processing apparatus according to the present invention, a modified region is formed by locally generating multiphoton absorption inside the object to be processed. Therefore, since the laser beam is hardly absorbed on the surface of the object to be processed, the surface of the object to be processed does not melt. The focusing point is a point where the laser beam is focused. The line to be cut may be a line actually drawn on the surface or inside of the object to be processed, or may be a virtual line. The above can also be said for the laser processing apparatus and the laser processing method described below.
【0009】
Further, according to the present inventor, it has been found that when the power of the pulsed laser light is reduced, the reforming spot can be controlled to be small, and when the power of the pulsed laser light is increased, the reforming spot can be controlled to be large. The reforming spot is a reforming portion formed by a 1-pulse pulsed laser beam, and becomes a reforming region when the reforming spots are gathered. Controlling the dimensions of the modified spot affects the cutting of the workpiece. That is, if the modified spot is too large, the accuracy of cutting along the planned cutting line of the workpiece and the flatness of the cut surface deteriorate. On the other hand, if the modified spot is extremely small with respect to a work object having a large thickness, it becomes difficult to cut the work object. According to the laser processing apparatus according to the present invention, the dimensions of the modified spot can be controlled by adjusting the magnitude of the power of the pulsed laser beam.
【0010】
Further, the laser processing apparatus according to the present invention includes a correlation storage means that stores in advance the correlation between the magnitude of the power of the pulsed laser light and the size of the modified spot. Based on the magnitude of the power of the input pulsed laser light, the dimensions of the modified spot formed by this magnitude of power are selected from the correlation storage means, and the dimensions of the selected modified spot are displayed. .. Therefore, the dimensions of the modified spot formed by the magnitude of the power of the pulsed laser beam input to the laser processing apparatus can be known before the laser processing.
【0011】
The laser processing apparatus according to the present invention has a laser light source that emits a pulsed laser beam having a pulse width of 1 μs or less and a peak power density of 1 × 10 at a focusing point of the pulsed laser beam emitted from the laser light source.<sup>8</sup>(W / cm<sup>2</sup>) A numerical aperture adjusting means for adjusting the numerical aperture of the optical system including the focusing lens and the numerical aperture based on the input of the numerical aperture. A means for aligning the focusing point of the pulsed laser light focused by the focusing lens with the inside of the object to be processed, and a relative focusing point of the pulsed laser light along the planned cutting line of the object to be processed. A moving means for moving is provided, and one modified spot is formed inside the work object by irradiating the work object with a 1-pulse pulsed laser beam by aligning a focusing point inside the work object. , Correlation storage means that stores the correlation between the numerical aperture of the numerical aperture adjusted by the numerical aperture adjusting means and the dimension of the modified spot in advance, and the numerical aperture of this size based on the input numerical aperture. It is characterized by including a dimension selecting means for selecting the dimension of the modified spot formed in the above from the correlation storage means, and a dimension display means for displaying the dimension of the modified spot selected by the dimension selecting means.
【0012】
According to the present inventor, it has been found that when the numerical aperture of the optical system including the condensing lens is increased, the modified spot can be controlled to be small, and when the numerical aperture is decreased, the modified spot can be controlled to be large. Therefore, according to the laser processing apparatus according to the present invention, the dimensions of the modified spot can be controlled by adjusting the numerical aperture of the optical system including the condensing lens.
【0013】
Further, the laser processing apparatus according to the present invention includes a correlation storage means that stores in advance the correlation between the numerical aperture and the size of the modified spot. Based on the numerical aperture of the input number of openings, the dimension of the modified spot formed by the numerical aperture of this size is selected from the correlation storage means, and the dimension of the selected modified spot is displayed. Therefore, the dimensions of the modified spots formed by the size of the numerical aperture input to the laser machining apparatus can be known before the laser machining.
【0014】
The laser processing apparatus according to the present invention has a laser light source that emits a pulsed laser beam having a pulse width of 1 μs or less and a peak power density of 1 × 10 at a focusing point of the pulsed laser beam emitted from the laser light source.<sup>8</sup>(W / cm<sup>2</sup>) It is provided with a lens selection means that includes a plurality of condensing lenses that condense the pulsed laser light and can select a plurality of condensing lenses, and each optical system including the plurality of condensing lenses is provided. A means for aligning the focusing point of the pulsed laser light focused by the focusing lens selected by the lens selection means with a different number of openings to the inside of the object to be processed, and a pulse along the planned cutting line of the object to be processed. It is equipped with a moving means that relatively moves the focusing point of the laser light, and by aligning the focusing point inside the object to be processed and irradiating the object with 1-pulse pulsed laser light, the inside of the object to be processed One modified spot is formed in the light, and a correlation storage means that stores in advance the correlation between the size of the number of apertures of the optical system including a plurality of focusing lenses and the size of the modified spot and the selected focusing lens. The size of the modified spot formed by the number of openings of this size is selected from the correlation storage means based on the size of the number of openings of the optical system including the optical system, and the dimension selection means is selected. It is characterized by comprising a dimension display means for displaying the dimensions of the modified spot.
【0015】
According to the laser processing apparatus according to the present invention, the dimensions of the modified spot can be controlled. In addition, the dimensions of the modified spots formed by the numerical aperture of the optical system including the selected condensing lens can be known before laser machining.
【0016】
The laser processing apparatus according to the present invention has a laser light source that emits a pulsed laser beam having a pulse width of 1 μs or less, and a large power of the pulsed laser beam emitted from the laser light source based on an input of the power magnitude of the pulsed laser beam. The peak power density of the power adjusting means for adjusting the pressure and the focusing point of the pulsed laser light emitted from the laser light source is 1 × 10.<sup>8</sup>(W / cm<sup>2</sup>) A condensing lens that condenses the pulsed laser light so as to be as described above, and an aperture number adjusting means for adjusting the size of the number of apertures of the optical system including the condensing lens based on the input of the size of the aperture number. A means for aligning the focusing point of the pulsed laser light focused by the focusing lens with the inside of the object to be processed, and a relative focusing point of the pulsed laser light along the planned cutting line of the object to be processed It is equipped with a moving means to move, and one modified spot is formed inside the work object by irradiating the work object with 1-pulse pulsed laser light by aligning the condensing point inside the work object. Correlation storage means that stores in advance the correlation between the power magnitude of the pulsed laser light adjusted by the power adjusting means and the size of the apertures adjusted by the aperture number adjusting means and the dimensions of the modified spot. , A dimension selection means for selecting from correlation storage means the dimensions of the modified spots formed by these magnitudes based on the magnitude of the power of the input pulsed laser light and the magnitude of the input apertures. , A dimension display means for displaying the dimensions of the modified spot selected by the dimension selection means.
【0017】
According to the laser processing apparatus according to the present invention, since the power adjustment and the numerical aperture adjustment can be combined, it is possible to increase the types of sizes in which the dimensions of the modified spot can be controlled. Further, for the same reason as the laser processing apparatus according to the present invention, the dimensions of the modified spot can be known before laser processing.
【0018】
The laser processing apparatus according to the present invention has a laser light source that emits a pulsed laser beam having a pulse width of 1 μs or less, and a large power of the pulsed laser beam emitted from the laser light source based on an input of the power magnitude of the pulsed laser beam. The peak power density of the power adjusting means for adjusting the pressure and the focusing point of the pulsed laser light emitted from the laser light source is 1 × 10.<sup>8</sup>(W / cm<sup>2</sup>) It is provided with a lens selection means that includes a plurality of condensing lenses that condense the pulsed laser light and can select a plurality of condensing lenses, and each optical system including the plurality of condensing lenses is provided. A means for aligning the focusing point of the pulsed laser light focused by the focusing lens selected by the lens selection means with a different number of openings to the inside of the object to be processed, and a pulse along the planned cutting line of the object to be processed. It is equipped with a moving means that relatively moves the focusing point of the laser light, and by aligning the focusing point inside the object to be processed and irradiating the object to be processed with 1-pulse pulsed laser light, the object to be processed is processed. One modified spot is formed inside, and a set of the magnitude of the power of the pulsed laser light adjusted by the power adjusting means and the magnitude of the number of openings of the optical system including a plurality of condensing lenses and the modified spot. These are based on the correlation storage means in which the correlation with the dimensions is stored in advance, the magnitude of the power of the input pulsed laser light, and the magnitude of the number of openings of the optical system including the selected condensing lens. It is characterized by including a dimension selection means for selecting the dimensions of the modified spot formed by the size from the correlation storage means, and a dimension display means for displaying the dimensions of the modified spot selected by the dimension selection means. To do.
【0019】
According to the laser processing apparatus according to the present invention, for the same reason as the laser processing apparatus according to the present invention, it is possible to increase the types of sizes in which the dimensions of the modified spot can be controlled, and the dimensions of the modified spot can be adjusted. It can be known before laser processing.
【0020】
The laser processing apparatus described above includes an image creating means for creating an image of a modified spot having a dimension selected by the dimension selecting means, and an image displaying means for displaying an image created by the image creating means. can do. According to this, the modified spot to be formed can be visually grasped before laser machining.
【0021】
The laser processing apparatus according to the present invention comprises a laser light source that emits a pulsed laser beam having a pulse width of 1 μs or less, a power adjusting means for adjusting the magnitude of the power of the pulsed laser beam emitted from the laser light source, and a laser light source. The peak power density of the focused point of the emitted pulsed laser light is 1 × 10.<sup>8</sup>(W / cm<sup>2</sup>) A means for condensing the pulsed laser light so as to be as described above, a means for aligning the condensing point of the pulsed laser light condensed by the condensing means with the inside of the object to be processed, and a plan for cutting the object to be processed. It is equipped with a moving means that relatively moves the focusing point of the pulsed laser light along the line, and by aligning the focusing point inside the object to be processed and irradiating the object to be processed with 1-pulse pulsed laser light. One modified spot is formed inside the object to be processed, and the correlation storage means that stores in advance the correlation between the magnitude of the power of the pulsed laser light adjusted by the power adjusting means and the dimensions of the modified spot is modified. It is equipped with a power selection means for selecting the magnitude of the power of the pulsed laser light that can be formed in this dimension based on the input of the size of the quality spot from the correlation storage means, and the power adjusting means is the power selected by the power selection means. It is characterized in that the magnitude of the power of the pulsed laser light emitted from the laser light source is adjusted so as to have a magnitude.
【0022】
The laser processing apparatus according to the present invention includes a correlation storage means that stores in advance the correlation between the magnitude of the power of the pulsed laser light and the size of the modified spot. The magnitude of the power of the pulsed laser beam that can be formed in this dimension based on the input of the dimension of the modified spot is selected from the correlation storage means. The power adjusting means adjusts the magnitude of the power of the pulsed laser light emitted from the laser light source so as to have the magnitude of the power selected by the power selecting means. Therefore, it is possible to form a modified spot having a desired size.
【0023】
The laser processing apparatus according to the present invention has a laser light source that emits a pulsed laser beam having a pulse width of 1 μs or less and a peak power density of 1 × 10 at a focusing point of the pulsed laser beam emitted from the laser light source.<sup>8</sup>(W / cm<sup>2</sup>) The numerical aperture adjusting means for adjusting the numerical aperture of the optical system including the condensing lens and the condensing lens for condensing the pulsed laser light so as to be as described above, and the condensing lens. It is provided with a means for aligning the focusing point of the pulsed laser light with the inside of the object to be processed and a moving means for relatively moving the focusing point of the pulsed laser light along the planned cutting line of the object to be processed. By aligning the focusing point inside the object and irradiating the object to be processed with 1-pulse pulsed laser light, one modified spot is formed inside the object to be processed, and the numerical aperture is adjusted by the numerical aperture adjusting means. The numerical aperture that can be formed in this dimension is selected from the correlation storage means that stores the correlation between the size of the modification spot and the dimension of the modification spot in advance and the numerical aperture that can be formed in this dimension based on the input of the dimension of the modification spot. A numerical aperture selection means is provided, and the numerical aperture adjusting means adjusts the numerical aperture of the optical system including the condensing lens so as to have the numerical aperture selected by the numerical aperture selecting means. And.
【0024】
The laser processing apparatus according to the present invention includes a correlation storage means that stores in advance the correlation between the numerical aperture and the size of the modified spot. The magnitude of the numerical aperture that can be formed in this dimension is selected from the correlation storage means based on the input of the dimension of the modified spot. The numerical aperture adjusting means adjusts the numerical aperture of the optical system including the condensing lens so as to have the numerical aperture of the numerical aperture selected by the numerical aperture selecting means. Therefore, it is possible to form a modified spot having a desired size.
【0025】
The laser processing apparatus according to the present invention has a laser light source that emits a pulsed laser beam having a pulse width of 1 μs or less and a peak power density of 1 × 10 at a focusing point of the pulsed laser beam emitted from the laser light source.<sup>8</sup>(W / cm<sup>2</sup>) A lens selection means that includes a plurality of condensing lenses that condense the pulsed laser light and can select a plurality of condensing lenses, and each optical system including the plurality of condensing lenses is provided. A means for aligning the focusing point of the pulsed laser light focused by the focusing lens selected by the lens selection means with a different number of openings to the inside of the object to be processed, and a pulse along the planned cutting line of the object to be processed. It is equipped with a moving means that relatively moves the focusing point of the laser light, and by aligning the focusing point inside the object to be processed and irradiating the object with 1-pulse pulsed laser light, the inside of the object to be processed One modified spot is formed in, and the correlation between the size of the number of apertures of a plurality of condensing lenses and the dimension of the modified spot is stored in advance. Based on the correlation storage means and the input of the dimension of the modified spot. It is provided with an opening number selecting means for selecting the size of the number of openings that can be formed in the dimension of the lever from the correlation storage means, and the lens selecting means is a collection of a plurality of apertures so as to be the size of the number of openings selected by the opening number selecting means. It is characterized by selecting an optical lens.
【0026】
According to the laser processing apparatus according to the present invention, the magnitude of the numerical aperture that can be formed in this dimension is selected from the correlation storage means based on the input of the dimension of the modified spot. The lens selection means selects a plurality of focusing lenses so as to have the size of the numerical aperture selected by the numerical aperture selection means. Therefore, it is possible to form a modified spot having a desired size.
【0027】
The laser processing apparatus according to the present invention comprises a laser light source that emits a pulsed laser beam having a pulse width of 1 μs or less, a power adjusting means for adjusting the magnitude of the power of the pulsed laser beam emitted from the laser light source, and a laser light source. The peak power density of the focused point of the emitted pulsed laser light is 1 × 10.<sup>8</sup>(W / cm<sup>2</sup>) Condensing with a condensing lens that condenses the pulsed laser light so as to be as described above, an aperture number adjusting means for adjusting the size of the number of apertures of the optical system including the condensing lens, and a condensing lens. It is provided with a means for aligning the condensing point of the pulsed laser light with the inside of the object to be processed and a moving means for relatively moving the condensing point of the pulsed laser light along the planned cutting line of the object to be processed. By aligning the focusing point inside the object and irradiating the object to be processed with 1-pulse pulsed laser light, one modified spot is formed inside the object to be processed, and the pulsed laser light adjusted by the power adjusting means. Based on the correlation storage means that stores in advance the correlation between the set of the size of the number of openings adjusted by the power magnitude and the number of openings adjusting means and the dimensions of the modified spot, and the input of the dimensions of the modified spot. It is provided with a set selection means for selecting a set of power and number of openings that can be formed in the dimensions of the lever from the correlation storage means, and the power adjusting means and the number of openings adjusting means are the power and the number of openings selected by the set selection means. It is characterized in that the magnitude of the power of the pulsed laser light emitted from the laser light source and the magnitude of the number of openings of the optical system including the condensing lens are adjusted so as to have the magnitude of.
【0028】
According to the laser processing apparatus according to the present invention, a combination of the magnitude of power and the magnitude of numerical aperture that can be formed in this dimension is selected from the correlation storage means based on the input of the dimension of the modified spot. Then, the magnitude of the power of the pulsed laser light emitted from the laser light source and the magnitude of the numerical aperture of the optical system including the condensing lens so as to be the magnitude of the selected power and the numerical aperture of the aperture, respectively. To adjust. Therefore, it is possible to form a modified spot having a desired size. Further, since the magnitude of the power and the numerical aperture are combined, it is possible to increase the types of sizes in which the dimensions of the reforming spot can be controlled.
【0029】
The laser processing apparatus according to the present invention includes a laser light source that emits a pulsed laser beam having a pulse width of 1 μs or less, a power adjusting means for adjusting the magnitude of the power of the pulsed laser beam emitted from the laser light source, and a laser light source. The peak power density of the focusing point of the pulsed laser light emitted from is 1 × 10.<sup>8</sup>(W / cm<sup>2</sup>) A lens selection means that includes a plurality of condensing lenses that condense the pulsed laser light and can select a plurality of condensing lenses, and each optical system including the plurality of condensing lenses is provided. A means for aligning the focusing point of the pulsed laser light focused by the focusing lens selected by the lens selection means with a different number of openings to the inside of the object to be processed, and a pulse along the planned cutting line of the object to be processed. It is equipped with a moving means that relatively moves the focusing point of the laser light, and by aligning the focusing point inside the object to be processed and irradiating the object with 1-pulse pulsed laser light, the inside of the object to be processed Correlation between the magnitude of the power of the pulsed laser light adjusted by the power adjusting means and the magnitude of the number of apertures of the plurality of condensing lenses and the size of the modified spot. A power storage means for selecting a set of power and the size of the number of openings that can be formed in this dimension based on the input of the size of the modified spot from the correlation storage means. The adjusting means and the lens selecting means adjust the power of the pulsed laser light emitted from the laser light source and select a plurality of condensing lenses so that the power and the number of apertures are selected by the set selecting means. It is characterized by doing.
【0030】
According to the laser processing apparatus according to the present invention, a combination of the magnitude of power and the magnitude of numerical aperture that can be formed in this dimension is selected from the correlation storage means based on the input of the dimension of the modified spot. The magnitude of the power of the pulsed laser light emitted from the laser light source is adjusted and a plurality of focusing lenses are selected so as to have the magnitude of the selected power and the numerical aperture. Therefore, it is possible to form a modified spot having a desired size. Further, since the magnitude of the power and the numerical aperture are combined, it is possible to increase the types of sizes in which the dimensions of the reforming spot can be controlled.
【0031】
In the laser processing apparatus according to the present invention, a display means for displaying the magnitude of the power selected by the power selection means, a display means for displaying the magnitude of the numerical aperture selected by the numerical aperture selection means, and a set selection means for selection. A display means for displaying the magnitude of the power and the numerical aperture of the set can be provided. According to this, it is possible to know the power and the numerical aperture when the laser processing apparatus operates based on the input of the dimensions of the modified spot.
【0032】
In the laser processing apparatus according to the present invention, a plurality of reforming spots can be formed inside the object to be processed along the planned cutting line. These modification spots define the modification area. The modified region is a crack region where cracks are generated inside the work target, a melt treatment region which is a melt-treated region inside the work target, and a region where the refractive index changes inside the work target. It includes at least one of the refractive index change regions.
【0033】
As an aspect of the power adjusting means, for example, there is an aspect including at least one of an ND filter and a polarizing filter. Further, there is also an embodiment in which the laser light source includes an excitation laser and the laser processing apparatus includes a drive current control means for controlling the drive current of the excitation laser. With these, the magnitude of the power of the pulsed laser light can be adjusted. Further, as an aspect of the numerical aperture adjusting means, for example, there is an aspect including at least one of a beam expander and an iris diaphragm.
【0034】
In the laser processing method according to the present invention, the focusing point of the pulsed laser light is aligned with the inside of the object to be processed, and the object to be processed is irradiated with the pulsed laser light to process along the planned cutting line of the object to be processed. The first step of forming a modified region by multiphoton absorption inside the object, the power of the pulsed laser light is adjusted to be larger or smaller than that of the first step, and the focusing point of the pulsed laser light is processed. By irradiating the object to be processed with a pulsed laser beam according to the inside of the object, another modified region due to multiphoton absorption is formed inside the object to be processed along the other scheduled cutting lines of the object to be processed. It is characterized by having a second step.
【0035】
Further, in the laser processing method according to the present invention, the focusing point of the pulsed laser light is aligned with the inside of the processed object, and the processed object is irradiated with the pulsed laser light, so that the processed object is along the planned cutting line of the processed object. The number of openings of the optical system including the first step of forming a modified region by multiphoton absorption inside the object to be processed and the condensing lens that collects the pulsed laser light should be larger or smaller than that of the first step. By adjusting the light concentration to the inside of the object to be processed and irradiating the object to be processed with pulsed laser light, the object to be processed is processed along the other scheduled cutting lines of the object to be processed. It is characterized by including a second step of forming another modified region by absorption of multiple photons inside the light.
【0036】
According to these laser processing methods according to the present invention, for example, when there is a direction in which cutting is easy and a direction in which cutting is difficult due to the crystal orientation of the object to be processed, a modified region formed in the direction in which cutting is easy. The size of the modified spots constituting the above is reduced, and the dimensions of the modified spots constituting the other modified regions formed in the direction in which cutting is difficult are increased. As a result, a flat cut surface can be obtained in a direction in which cutting is easy, and cutting is possible even in a direction in which cutting is difficult.
【0037】
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The laser processing method and the laser processing apparatus according to the present embodiment form a modified region by absorbing multiple photons. Multiphoton absorption is a phenomenon that occurs when the intensity of laser light is extremely high. First, multiphoton absorption will be briefly described.
【0038】
Material absorption bandgap E<sub>G</sub>When the photon energy hν is smaller than that, it becomes optically transparent. Therefore, the condition for absorption in the material is hν> E<sub>G</sub>Is. However, even if it is optically transparent, if the intensity of the laser beam is made very large, nhν> E<sub>G</sub>Absorption occurs in the material under the condition of (n = 2,3,4, ...). This phenomenon is called multiphoton absorption. In the case of a pulse wave, the intensity of the laser beam is the peak power density (W / cm) of the focusing point of the laser beam.<sup>2</sup>), For example, the peak power density is 1 × 10.<sup>8</sup>(W / cm<sup>2</sup>) Multiphoton absorption occurs under the above conditions. The peak power density is obtained by (energy per pulse of laser light at the focusing point) ÷ (beam spot cross-sectional area of laser light × pulse width). In the case of continuous waves, the intensity of the laser beam is the electric field intensity (W / cm) at the focusing point of the laser beam.<sup>2</sup>).
【0039】
The principle of laser processing according to the present embodiment utilizing such multiphoton absorption will be described with reference to FIGS. 1 to 6. FIG. 1 is a plan view of the machining object 1 during laser machining, FIG. 2 is a cross-sectional view of the machining object 1 shown in FIG. 1 along the line II-II, and FIG. 3 is a machining target after laser machining. It is a plan view of the object 1, FIG. 4 is a cross-sectional view of the workpiece 1 shown in FIG. 3 along the IV-IV line, and FIG. 5 is a cross section of the workpiece 1 shown in FIG. 3 along the VV line. FIG. 6 is a plan view of the cut object 1 to be machined.
【0040】
As shown in FIGS. 1 and 2, the surface 3 of the object to be processed 1 has a line 5 to be cut. The line 5 to be cut is a virtual line extending in a straight line. In the laser processing according to the present embodiment, the processing target 1 is formed by irradiating the processing target 1 with the laser beam L by aligning the condensing point P inside the processing target 1 under the condition that multiphoton absorption occurs. The focusing point is a point where the laser beam L is focused.
【0041】
By moving the laser beam L relatively along the planned cutting line 5 (that is, along the direction of arrow A), the focusing point P is moved along the planned cutting line 5. As a result, as shown in FIGS. 3 to 5, the modified region 7 is formed only inside the workpiece 1 along the planned cutting line 5. In the laser machining method according to the present embodiment, the machining target 1 does not generate heat by absorbing the laser beam L to form the modified region 7. The modified region 7 is formed by transmitting the laser beam L through the object to be processed 1 and generating multiphoton absorption inside the object 1 to be processed. Therefore, since the laser beam L is hardly absorbed by the surface 3 of the object to be processed 1, the surface 3 of the object to be processed 1 is not melted.
【0042】
In cutting the object to be processed 1, if there is a starting point at the cutting point, the object 1 to be processed is cracked from the starting point, so that the object 1 to be processed can be cut with a relatively small force as shown in FIG. Therefore, the machining object 1 can be cut without causing unnecessary cracks on the surface 3 of the machining object 1.
【0043】
There are two possible ways to cut the object to be processed starting from the modified region. One is a case where an artificial force is applied to the object to be processed after the modified area is formed, so that the object to be processed is cracked and the object to be processed is cut from the modified area as a starting point. This is, for example, cutting when the thickness of the object to be processed is large. When an artificial force is applied, for example, thermal stress is generated by applying bending stress or shear stress to the workpiece along the planned cutting line of the workpiece, or by giving a temperature difference to the workpiece. To let them do it. The other is the case where the modified region is formed to spontaneously crack in the cross-sectional direction (thickness direction) of the workpiece starting from the modified region, and as a result, the workpiece is cut. Is. For example, when the thickness of the object to be processed is small, even one modified region is possible, and when the thickness of the object to be processed is large, it is possible to form a plurality of modified regions in the thickness direction. .. Even in the case of this natural cracking, the crack does not advance to the surface on the portion where the modified region is not formed at the cutting portion, and only the surface on the portion where the modified portion is formed can be cut. Since it can be done, it is possible to control the cutting well. In recent years, the thickness of semiconductor wafers such as silicon wafers has tended to decrease, so such a cutting method with good controllability is very effective.
【0044】
By the way, as the modified region formed by multiphoton absorption in this embodiment, there are the following (1) to (3).
【0045】
(1) When the modified region is a crack region containing one or more cracks Laser light is processed into objects (for example, glass and LiTaO)<sub>3</sub>The electric field strength at the condensing point is 1 × 10 by aligning the condensing point inside the (piezoelectric material consisting of).<sup>8</sup>(W / cm<sup>2</sup>) Or more and the pulse width is 1 μs or less. The magnitude of this pulse width is a condition in which a crack region can be formed only inside the object to be processed without causing extra damage to the surface of the object to be processed while causing multiphoton absorption. As a result, a phenomenon called optical damage due to multiphoton absorption occurs inside the object to be processed. This optical damage induces thermal strain inside the work piece, which forms a crack region inside the work piece. The upper limit of the electric field strength is, for example, 1 × 10.<sup>12</sup>(W / cm<sup>2</sup>). The pulse width is preferably 1 ns to 200 ns, for example. The formation of crack regions by multiphoton absorption is described in, for example, "Inside the glass substrate by solid-state laser harmonics" on pages 23 to 28 of the 45th Laser Thermal Processing Workshop Proceedings (December 1998). It is described in "Marking".
【0046】
The present inventor experimentally determined the relationship between the electric field strength and the size of cracks. The experimental conditions are as follows.
【0047】
(A) Object to be processed: Pyrex glass (thickness 700 μm) (B) Laser Light source: Semiconductor laser excitation Nd: YAG laser Wavelength: 1064nm Laser light spot cross-sectional area: 3.14 × 10<sup>-8</sup>cm<sup>2</sup>Oscillation form: Q-switched pulse Repeat frequency: 100kHz Pulse width: 30ns Output: Output <1mJ / pulse Laser light quality: TEM<sub>00</sub>Polarization characteristics: Linearly polarized light (C) Condensing lens Transmittance to laser wavelength: 60 percent (D) Movement speed of the mounting table on which the object to be processed is placed: 100 mm / sec The laser light quality is TEM.<sub>00</sub>Means that the light collecting property is high and the light can be collected up to the wavelength of the laser beam.
【0048】
FIG. 7 is a graph showing the results of the above experiment. The horizontal axis is the peak power density, and since the laser light is a pulsed laser light, the electric field strength is represented by the peak power density. The vertical axis shows the size of the crack portion (crack spot) formed inside the workpiece by the 1-pulse laser beam. Crack spots gather to form a crack area. The size of the crack spot is the size of the portion having the maximum length in the shape of the crack spot. The data indicated by the black circles in the graph is when the magnification of the condensing lens (C) is 100 times and the numerical aperture (NA) is 0.80. On the other hand, the data indicated by white circles in the graph is when the magnification of the condensing lens (C) is 50 times and the numerical aperture (NA) is 0.55. Peak power density is 10<sup>11</sup>(W / cm<sup>2</sup>It can be seen that crack spots are generated inside the object to be processed from the degree of), and the crack spots also increase as the peak power density increases.
【0049】
Next, in the laser machining according to the present embodiment, the mechanism of cutting the workpiece by forming the crack region will be described with reference to FIGS. 8 to 11. As shown in FIG. 8, under the condition that multiphoton absorption occurs, the condensing point P is aligned with the inside of the work target 1, the laser light L is irradiated to the work target 1, and the crack region inside along the planned cutting line. Form 9. The crack region 9 is a region containing one or a plurality of cracks. As shown in FIG. 9, the crack grows further starting from the crack region 9, and as shown in FIG. 10, the crack reaches the front surface 3 and the back surface 21 of the workpiece 1, and as shown in FIG. 11, the workpiece 1 The object 1 to be processed is cut by cracking. The cracks that reach the front and back surfaces of the object to be processed may grow naturally, or may grow when a force is applied to the object to be processed.
【0050】
(2) When the modified region is a melt processing region By aligning the condensing point inside the object to be processed (for example, a semiconductor material such as silicon) with laser light, the electric field strength at the condensing point is 1 × 10.<sup>8</sup>(W / cm<sup>2</sup>) Or more and the pulse width is 1 μs or less. As a result, the inside of the object to be processed is locally heated by multiphoton absorption. By this heating, a melt processing region is formed inside the object to be processed. The melting treatment region means at least one of a region once melted and then resolidified, a region in a molten state, and a region in a state of being resolidified from melting. Further, the melt processing region can be said to be a region where the phase has changed or a region where the crystal structure has changed. Further, the melt-treated region can be said to be a region in which one structure is changed to another in a single crystal structure, an amorphous structure, or a polycrystalline structure. That is, for example, it means a region changed from a single crystal structure to an amorphous structure, a region changed from a single crystal structure to a polycrystalline structure, and a region changed from a single crystal structure to a structure including an amorphous structure and a polycrystalline structure. To do. When the object to be processed has a silicon single crystal structure, the melt processing region is, for example, an amorphous silicon structure. The upper limit of the electric field strength is, for example, 1 × 10.<sup>12</sup>(W / cm<sup>2</sup>). The pulse width is preferably 1 ns to 200 ns, for example.
【0051】
The present inventor has experimentally confirmed that a melt processing region is formed inside the silicon wafer. The experimental conditions are as follows.
【0052】
(A) Object to be processed: Silicon wafer (thickness 350 μm, outer diameter 4 inches) (B) Laser Light source: Semiconductor laser excitation Nd: YAG laser Wavelength: 1064nm Laser light spot cross-sectional area: 3.14 × 10<sup>-8</sup>cm<sup>2</sup>Oscillation form: Q-switched pulse Repeat frequency: 100kHz Pulse width: 30ns Output: 20 μJ / pulse Laser light quality: TEM<sub>00</sub>Polarization characteristics: Linearly polarized light (C) Condensing lens Magnification: 50x NA: 0.55 Transmittance to laser wavelength: 60 percent (D) Movement speed of the mounting table on which the object to be processed is placed: 100 mm / sec FIG. 12 is a diagram showing a photograph of a cross section of a part of a silicon wafer cut by laser processing under the above conditions. A melt processing region 13 is formed inside the silicon wafer 11. The size of the melt-treated region formed under the above conditions in the thickness direction is about 100 μm.
【0053】
It will be described that the melt processing region 13 is formed by multiphoton absorption. FIG. 13 is a graph showing the relationship between the wavelength of the laser beam and the transmittance inside the silicon substrate. However, the reflective components on the front surface side and the back surface side of the silicon substrate are removed, and the transmittance is shown only inside. The above relationship was shown for each of the thickness t of the silicon substrate of 50 μm, 100 μm, 200 μm, 500 μm, and 1000 μm.
【0054】
For example, at 1064 nm, which is the wavelength of the Nd: YAG laser, when the thickness of the silicon substrate is 500 μm or less, it can be seen that 80% or more of the laser light is transmitted inside the silicon substrate. Since the thickness of the silicon wafer 11 shown in FIG. 12 is 350 μm, the melt processing region by multiphoton absorption is formed near the center of the silicon wafer, that is, at a portion of 175 μm from the surface. In this case, the transmittance is 90% or more with reference to a silicon wafer having a thickness of 200 μm, so that the laser beam is hardly absorbed inside the silicon wafer 11 and most of it is transmitted. This does not mean that the laser beam is absorbed inside the silicon wafer 11 and the melt processing region is formed inside the silicon wafer 11 (that is, the melt treatment region is formed by normal heating by the laser light), but melts. It means that the treated area was formed by multiphoton absorption. The formation of the melt processing region by multiphoton absorption is described in, for example, "Evaluation of silicon processing characteristics by picosecond pulse laser" on pages 72 to 73 of the outline of the lecture at the National Conference of the Welding Society, Vol. Are listed.
【0055】
The silicon wafer is cracked in the cross-sectional direction starting from the melting process region, and the cracks reach the front surface and the back surface of the silicon wafer, resulting in cutting. These cracks that reach the front and back surfaces of the silicon wafer may grow naturally, or may grow when a force is applied to the object to be processed. The cracks naturally grow from the melted region to the front and back surfaces of the silicon wafer when the cracks grow from the region once melted and then resolidified, or when the cracks grow from the melted region. And at least one of the cases where the crack grows from the region in the state of being resolidified from melting. In either case, as shown in FIG. 12, a melt processing region is formed only inside the cut surface after cutting. When the melt processing region is formed inside the object to be processed, it is difficult for unnecessary cracks that deviate from the planned cutting line to occur at the time of cutting, so that the cutting control becomes easy.
【0056】
(3) When the modified region is the refractive index change region The laser beam is aligned with the condensing point inside the object to be processed (for example, glass), and the electric field strength at the condensing point is 1 × 10.<sup>8</sup>(W / cm<sup>2</sup>) Or more and the pulse width is 1ns or less. When the pulse width is extremely shortened and multiphoton absorption is caused inside the work object, the energy due to the multi photon absorption is not converted into thermal energy, and the ionic valence changes and crystallizes inside the work object. Alternatively, a permanent structural change such as polarization orientation is induced to form a refractive index change region. The upper limit of the electric field strength is, for example, 1 × 10.<sup>12</sup>(W / cm<sup>2</sup>). Pulse width is preferably eg 1ns or less, 1 ps or less more preferred. The formation of the refractive index change region by multiphoton absorption is described, for example, in "Proceedings of the 42nd Laser Thermal Processing Study Group (November 1997)" on pages 105 to 111, "Inside the glass by femtosecond laser irradiation. Photoinduced structure formation .
【0057】
As described above, according to the present embodiment, the modified region is formed by multiphoton absorption. Then, in this embodiment, the size of the modified spot is controlled by adjusting the magnitude of the power of the pulsed laser light and the magnitude of the numerical aperture of the optical system including the condensing lens. The reforming spot is a reforming portion formed by a one-pulse shot of pulsed laser light (that is, one-pulse laser irradiation), and becomes a reforming region when the reforming spots are gathered. The necessity of dimensional control of the modified spot will be described by taking a crack spot as an example.
【0058】
If the crack spot is too large, the accuracy of cutting the object to be machined along the planned cutting line is lowered, and the flatness of the cut surface is deteriorated. This will be described with reference to FIGS. 14 to 19. FIG. 14 is a plan view of the object to be machined 1 when the crack spot is formed relatively large by using the laser machining method according to the present embodiment. FIG. 15 is a cross-sectional view taken along the XV-XV on the scheduled cutting line 5 of FIG. 16th, 17th, and 18th are cross-sectional views taken along the XVI-XVI, XVII-XVII, and XVIII-XVIII orthogonal to the planned cutting line 5 of FIG. 14, respectively. As can be seen from these figures, if the crack spot 90 is too large, the size variation of the crack spot 90 also becomes large. Therefore, as shown in FIG. 19, the accuracy of cutting the machining object 1 along the scheduled cutting line 5 deteriorates. Further, since the unevenness of the cut surface 43 of the object 1 to be processed becomes large, the flatness of the cut surface 43 deteriorates. On the other hand, as shown in FIG. 20, when the crack spot 90 is formed relatively small (for example, 20 μm or less) by using the laser processing method according to the present embodiment, the crack spot 90 can be uniformly formed and the crack spot 90 can be formed. It is possible to suppress the spread in the direction deviated from the direction of the planned cutting line. Therefore, as shown in FIG. 21, it is possible to improve the cutting accuracy of the machining object 1 along the scheduled cutting line 5 and the flatness of the cut surface 43.
【0059】
If the crack spot is too large in this way, it is not possible to perform precise cutting along the planned cutting line or cutting to obtain a flat cut surface. However, if the crack spot is extremely small with respect to the object to be processed having a large thickness, it becomes difficult to cut the object to be processed.
【0060】
It will be described that the size of the crack spot can be controlled according to the present embodiment. As shown in FIG. 7, when the peak power density is the same, the size of the crack spot when the magnification of the condensing lens is 100 and NA is 0.8 is the size of the crack when the magnification of the condensing lens is 50 and NA is 0.55. It is smaller than the size of the spot. Since the peak power density is proportional to the energy per pulse of the laser light, that is, the power of the pulsed laser light as explained earlier, the same peak power density means the same power of the laser light. As described above, when the power of the laser beam is the same and the beam spot cross-sectional area is the same, the size of the crack spot can be controlled to be small (large) when the numerical aperture of the condensing lens is large (small).
【0061】
Further, even if the numerical aperture of the condensing lens is the same, the size of the crack spot can be controlled to be small by reducing the power of the laser beam (peak power density), and the size of the crack spot can be controlled to be large by increasing the power of the laser light.
【0062】
Therefore, as can be seen from the graph shown in FIG. 7, the size of the crack spot can be controlled to be small by increasing the numerical aperture of the condensing lens and reducing the power of the laser beam. On the contrary, the size of the crack spot can be largely controlled by reducing the numerical aperture of the condensing lens and increasing the power of the laser beam.
【0063】
The dimensional control of the crack spot will be further described with reference to the drawings. The example shown in FIG. 22 is a cross-sectional view of the workpiece 1 in which the pulsed laser beam L is focused inside using a focusing lens having a predetermined numerical aperture. The region 41 is a region where the electric field strength is equal to or higher than the threshold value that causes multiphoton absorption by this laser irradiation. FIG. 23 is a cross-sectional view of the crack spot 90 formed due to the absorption of multiple photons by the irradiation of the laser beam L. On the other hand, the example shown in FIG. 24 is a cross-sectional view of the workpiece 1 in which the pulsed laser beam L is focused inside using a focusing lens having a numerical aperture larger than that shown in FIG. 22. FIG. 25 is a cross-sectional view of the crack spot 90 formed due to the absorption of multiple photons by the irradiation of the laser beam L. The height h of the crack spot 90 depends on the dimension in the thickness direction of the workpiece 1 in the region 41, and the width w of the crack spot 90 is the dimension in the direction orthogonal to the thickness direction of the workpiece 1 in the region 41. Dependent. That is, if these dimensions of the region 41 are reduced, the height h and width w of the crack spot 90 can be reduced, and if these dimensions are increased, the height h and width w of the crack spot 90 can be increased. As is clear from a comparison between FIGS. 23 and 25, when the power of the laser beam is the same, the numerical aperture of the condensing lens is increased (smaller) to increase (decrease) the numerical aperture of the crack spot 90 so that the height h and width w of the crack spot 90 Can be controlled small (large).
【0064】
Further, the example shown in FIG. 26 is a cross-sectional view of the workpiece 1 in which the pulsed laser beam L having a power smaller than that shown in FIG. 22 is focused inside. In the example shown in FIG. 26, since the power of the laser beam is reduced, the area of the region 41 is smaller than that of the region 41 shown in FIG. FIG. 27 is a cross-sectional view of the crack spot 90 formed due to the absorption of multiple photons by the irradiation of the laser beam L. As is clear from the comparison between FIGS. 23 and 27, when the numerical aperture of the condensing lens is the same, if the power of the laser beam is reduced (larger), the height h and width w of the crack spot 90 are reduced (larger). ) Can be controlled.
【0065】
Further, the example shown in FIG. 28 is a cross-sectional view of the workpiece 1 in which the pulsed laser beam L having a power smaller than that shown in FIG. 24 is focused inside. FIG. 29 is a cross-sectional view of the crack spot 90 formed due to the absorption of multiple photons by the irradiation of the laser beam L. As can be seen from the comparison between FIGS. 23 and 29, when the numerical aperture of the condensing lens is increased (smaller) and the power of the laser beam is reduced (larger), the height h and width w of the crack spot 90 are increased. Can be controlled small (large).
【0066】
By the way, the reason why the region 41 indicating the region showing the electric field strength equal to or higher than the threshold value of the electric field strength in which the crack spot can be formed is limited to the condensing point P and its vicinity is as follows. Since the present embodiment uses a laser light source having high beam quality, the laser light can be highly focused and can be focused up to the wavelength of the laser light. Therefore, since the beam profile of this laser beam has a Gaussian distribution, the electric field intensity has the strongest distribution at the center of the beam, and the intensity decreases as the distance from the center increases. Even in the process in which this laser beam is actually focused by the focusing lens, it is basically focused in the state of Gaussian distribution. Therefore, the region 41 is limited to the focusing point P and its vicinity.
【0067】
As described above, according to the present embodiment, the size of the crack spot can be controlled. The size of the crack spot is determined in consideration of the requirement for the degree of precise cutting, the requirement for the degree of flatness on the cut surface, and the size of the thickness of the object to be machined. Further, the size of the crack spot can be determined in consideration of the material of the object to be processed. According to the present embodiment, since the dimensions of the modified spot can be controlled, by reducing the modified spot for a work target having a relatively small thickness, it is possible to precisely cut along the planned cutting line, and It is possible to cut with good flatness of the cut surface. Further, by enlarging the modified spot, it is possible to cut even a relatively large object to be processed.
【0068】
Further, for example, due to the crystal orientation of the object to be processed, the object to be processed may have a direction in which cutting is easy and a direction in which cutting is difficult. In cutting such an object to be processed, for example, as shown in FIGS. 20 and 21, the size of the crack spot 90 formed in the direction in which cutting is easy is reduced. On the other hand, as shown in FIGS. 21 and 30, when the direction of the planned cutting line orthogonal to the planned cutting line 5 is a direction in which cutting is difficult, the size of the crack spot 90 formed in this direction is increased. As a result, a flat cut surface can be obtained in a direction in which cutting is easy, and cutting is possible even in a direction in which cutting is difficult.
【0069】
The fact that the dimensions of the modified spot can be controlled has been described in the case of the crack spot, but the same can be said for the melt-treated spot and the refractive index change spot. The power of the pulsed laser light can be expressed by, for example, the energy per pulse (J) or the average output (W) which is the value obtained by multiplying the energy per pulse by the frequency of the laser light.
【0070】
Next, a specific example of this embodiment will be described.
【0071】
[First Example] The laser processing apparatus according to the first example of the present embodiment will be described. FIG. 31 is a schematic configuration diagram of this laser processing apparatus 400. The laser processing apparatus 400 is emitted from the laser light source 101 that generates the laser light L, the laser light source control unit 102 that controls the laser light source 101 in order to adjust the power and pulse width of the laser light L, and the laser light source 101. It is provided with a power adjusting unit 401 for adjusting the power of the laser beam L.
【0072】
The power adjusting unit 401 is, for example, a plurality of ND (neutral density) filters and a mechanism for moving each ND filter to a position perpendicular to the optical axis of the laser beam L or moving it out of the optical path of the laser beam L. And. The ND filter is a filter that reduces the intensity of light without changing the relative spectral distribution of energy. Multiple ND filters have different dimming rates. The power adjusting unit 401 adjusts the power of the laser beam L emitted from the laser light source 101 by any one of the plurality of ND filters or a combination thereof. The dimming rate of the plurality of ND filters is the same, and the power adjusting unit 401 emits light from the laser light source 101 by changing the number of ND filters that are moved to a position perpendicular to the optical axis of the laser beam L. The power of the laser beam L can also be adjusted.
【0073】
The power adjusting unit 401 includes a polarizing filter arranged perpendicular to the optical axis of the linearly polarized laser beam L, a mechanism for rotating the polarizing filter around the optical axis of the laser beam L by a desired angle, and the like. It may be provided with. The power adjusting unit 401 adjusts the power of the laser beam L emitted from the laser light source 101 by rotating the polarizing filter by a desired angle around the optical axis.
【0074】
The power of the laser beam L emitted from the laser light source 101 can also be adjusted by controlling the drive current of the excitation semiconductor laser of the laser light source 101 with the laser light source control unit 102, which is an example of the drive current control means. it can. Therefore, the power of the laser beam L can be adjusted by at least one of the power adjusting unit 401 and the laser light source control unit 102. If the size of the modified region can be set to a desired value only by adjusting the power of the laser beam L by the laser light source control unit 102, the power adjustment unit 401 is unnecessary. The power adjustment described above is performed by the operator of the laser processing apparatus inputting the magnitude of power to the overall control unit 127, which will be described later, using a keyboard or the like.
【0075】
The laser processing apparatus 400 further includes a dichroic mirror 103 and a dichroic mirror 103 arranged so that the laser light L whose power is adjusted by the power adjusting unit 401 is incident and the direction of the optical axis of the laser light L is changed by 90 °. It includes a lens selection mechanism 403 including a plurality of condensing lenses that collect the reflected laser light L, and a lens selection mechanism control unit 405 that controls the lens selection mechanism 403.
【0076】
The lens selection mechanism 403 includes condensing lenses 105a, 105b, and 105c, and a support plate 407 that supports them. The numerical aperture of the optical system including the condensing lens 105a, the numerical aperture of the optical system including the condensing lens 105b, and the numerical aperture of the optical system including the condensing lens 105c are different. The lens selection mechanism 403 rotates the support plate 407 based on the signal from the lens selection mechanism control unit 405 to obtain a desired focusing lens from the focusing lenses 105a, 105b, and 105c of the laser beam L. Place it on the optical axis. That is, the lens selection mechanism 403 is a revolver type.
【0077】
The number of condensing lenses attached to the lens selection mechanism 403 is not limited to three, and may be any other number. The operator of the laser processing apparatus inputs an instruction to select the numerical aperture or one of the focusing lenses 105a, 105b, and 105c to the overall control unit 127, which will be described later, using a keyboard or the like. The focusing lens is selected, that is, the numerical aperture is selected.
【0078】
The laser processing apparatus 400 further mounts a processing object 1 among the condensing lenses 105a to 105c, which is irradiated with the laser light L condensed by the condensing lens arranged on the optical axis of the laser light L. The mounting table 107 to be mounted, the X-axis stage 109 for moving the mounting table 107 in the X-axis direction, and the Y-axis stage 111 for moving the mounting table 107 in the Y-axis direction orthogonal to the X-axis direction. A Z-axis stage 113 for moving the pedestal 107 in the Z-axis direction orthogonal to the X-axis and Y-axis directions, and a stage control unit 115 for controlling the movement of these three stages 109, 111, 113 are provided.
【0079】
Since the Z-axis direction is orthogonal to the surface 3 of the object 1 to be processed, it is the direction of the depth of focus of the laser beam L incident on the object 1 to be processed. Therefore, by moving the Z-axis stage 113 in the Z-axis direction, the condensing point P of the laser beam L can be aligned with the inside of the object 1 to be processed. Further, the movement of the focusing point P in the X (Y) axis direction is performed by moving the workpiece 1 in the X (Y) axis direction by the X (Y) axis stage 109 (111). The X (Y) axis stage 109 (111) is an example of a means of transportation.
【0080】
The laser light source 101 is an Nd: YAG laser that generates pulsed laser light. Other lasers that can be used for the laser light source 101, Nd: YVO<sub>4</sub>There are lasers, Nd: YLF lasers and titanium sapphire lasers. When forming crack regions and melt processing regions, Nd: YAG laser, Nd: YVO<sub>4</sub>It is preferable to use a laser or Nd: YLF laser. When forming a refractive index change region, it is preferable to use a titanium sapphire laser.
【0081】
In the first example, pulsed laser light is used for processing the object 1 to be processed, but continuous wave laser light may be used as long as it can cause multiphoton absorption. The condensing lenses 105a to 105c are examples of condensing means. The Z-axis stage 113 is an example of a means for aligning the focusing point of the laser beam with the inside of the object to be processed. By moving the focusing lenses 105a to 105c in the Z-axis direction, the focusing point of the laser beam can be aligned with the inside of the object to be processed.
【0082】
The laser processing apparatus 400 further includes an observation light source 117 that generates visible light to illuminate the processing object 1 mounted on the mounting table 107 with visible light, and the same light as the dichroic mirror 103 and the focusing lens 105. It includes a beam splitter 119 for visible light arranged on the axis. A dichroic mirror 103 is arranged between the beam splitter 119 and the focusing lens 105. The beam splitter 119 has a function of reflecting about half of visible light and transmitting the other half, and is arranged so as to change the direction of the optical axis of visible light by 90 °. Approximately half of the visible light generated from the observation light source 117 is reflected by the beam splitter 119, and this reflected visible light passes through the dichroic mirror 103 and the condensing lens 105, and the line 5 to be cut of the object 1 to be processed, etc. Illuminate surface 3 including.
【0083】
The laser processing apparatus 400 further includes a beam splitter 119, a dichroic mirror 103, and an image pickup element 121 and an imaging lens 123 arranged on the same optical axis as the focusing lens 105. As the image sensor 121, for example, there is a CCD (charge-coupled device) camera. The reflected light of visible light that illuminates the surface 3 including the line 5 to be cut passes through the focusing lens 105, the dichroic mirror 103, and the beam splitter 119, is imaged by the imaging lens 123, and is imaged by the imaging element 121. It becomes the imaging data.
【0084】
The laser processing apparatus 400 further includes an imaging data processing unit 125 into which imaging data output from the imaging element 121 is input, an overall control unit 127 that controls the entire laser processing apparatus 400, and a monitor 129. The image pickup data processing unit 125 calculates the focus data for focusing the visible light generated by the observation light source 117 on the surface 3 based on the image pickup data. Based on this focus data, the stage control unit 115 moves and controls the Z-axis stage 113 so that the visible light is focused on the surface 3. Therefore, the image pickup data processing unit 125 functions as an autofocus unit. Further, the image pickup data processing unit 125 calculates image data such as an enlarged image of the surface 3 based on the image pickup data. This image data is sent to the overall control unit 127, various processes are performed by the overall control unit, and the image data is sent to the monitor 129. As a result, an enlarged image or the like is displayed on the monitor 129.
【0085】
Data from the stage control unit 115, image data from the imaging data processing unit 125, and the like are input to the overall control unit 127, and the laser light source control unit 102, the observation light source 117, and the stage control unit are also based on these data. By controlling 115, the entire laser processing apparatus 400 is controlled. Therefore, the overall control unit 127 functions as a computer unit. Further, the overall control unit 127 is electrically connected to the power adjustment unit 401. FIG. 31 omits this illustration. When the magnitude of the power is input to the overall control unit 127, the overall control unit 127 controls the power adjustment unit 401, whereby the power is adjusted.
【0086】
FIG. 32 is a block diagram showing a part of an example of the overall control unit 127. The overall control unit 127 includes a dimension selection unit 411, a correlation storage unit 413, and an image creation unit 415. In the dimension selection unit 411, the operator of the laser processing apparatus inputs the magnitude of the power of the pulsed laser light and the numerical aperture of the optical system including the condensing lens by using a keyboard or the like. In this example, instead of directly inputting the numerical aperture size, an input may be used to select one of the focusing lenses 105a, 105b, and 105c. In this case, the numerical apertures of the focusing lenses 105a, 105b, and 105c are registered in advance in the overall control unit 127, and the numerical aperture data of the optical system including the selected focusing lens is automatically dimensioned. It is input to the selection unit 411.
【0087】
The correlation storage unit 413 stores in advance the correlation between the set of the power magnitude and the numerical aperture of the pulsed laser beam and the dimensions of the modified spot. FIG. 33 is an example of a table showing this correlation. In this example, the numerical aperture of the optical system including the focusing lenses 105a, 105b, and 105c is registered in the numerical aperture column. In the power column, the magnitude of the power of the pulsed laser beam adjusted by the power adjusting unit 401 is registered. In the dimension column, the dimensions of the modified spot formed by the combination of the corresponding set of power and numerical aperture are registered. For example, the power is 1.24 x 10<sup>11</sup>(W / cm<sup>2</sup>), The dimension of the modified spot formed when the numerical aperture is 0.55 is 120 μm. The data of this correlation can be obtained, for example, by performing the experiments described in FIGS. 22 to 29 before laser machining.
【0088】
By inputting the magnitude of power and the numerical aperture of the numerical aperture to the dimension selection unit 411, the dimension selection unit 411 selects a set of values having the same values from the correlation storage unit 413 and corresponds to the set. Send dimensional data to monitor 129. As a result, the monitor 129 displays the dimensions of the modified spots formed under the magnitude of the input power and the numerical aperture. If there is no set of values with the same magnitude, the dimensional data corresponding to the set of closest values is sent to monitor 129.
【0089】
The dimensional data corresponding to the set selected by the dimensional selection unit 411 is sent from the dimensional selection unit 411 to the image creation unit 415. The image creation unit 415 creates image data of the modified spot of this dimension based on the data of this dimension, and sends it to the monitor 129. As a result, the image of the modified spot is also displayed on the monitor 129. Therefore, it is possible to know the size of the modified spot and the shape of the modified spot before laser machining.
【0090】
The magnitude of power can be fixed and the numerical aperture can be made variable. The table in this case is shown in FIG. For example, power 1.49 x 10<sup>11</sup>(W / cm<sup>2</sup>) And the numerical aperture of the modified spot formed when the numerical aperture is 0.55 is 150 μm. It is also possible to fix the numerical aperture and make the power variable. The table in this case is shown in FIG. For example, the numerical aperture is fixed at 0.8 and the power is 1.19 x 10.<sup>11</sup>(W / cm<sup>2</sup>The size of the modified spot formed at) is 30 μm.
【0091】
Next, the laser processing method according to the first example of the present embodiment will be described with reference to FIGS. 31 and 36. FIG. 36 is a flowchart for explaining this laser processing method. The object to be processed 1 is a silicon wafer.
【0092】
First, the light absorption characteristics of the object to be processed 1 are measured by a spectrophotometer or the like (not shown). Based on this measurement result, a laser light source 101 that generates laser light L having a transparent wavelength or a wavelength with little absorption with respect to the object 1 to be processed is selected (S101). Next, the thickness of the object to be processed 1 is measured. The amount of movement of the workpiece 1 in the Z-axis direction is determined based on the thickness measurement result and the refractive index of the workpiece 1 (S103). This is because the condensing point P of the laser beam L is located inside the machining object 1, so that the condensing point P of the laser beam L located on the surface 3 of the machining object 1 is used as a reference. The amount of movement in the Z-axis direction. This movement amount is input to the overall control unit 127.
【0093】
The object 1 to be machined is placed on the mounting table 107 of the laser machining apparatus 400. Then, visible light is generated from the observation light source 117 to illuminate the object 1 to be processed (S105). The surface 3 of the workpiece 1 including the illuminated line 5 to be cut is imaged by the image sensor 121. This imaging data is sent to the imaging data processing unit 125. Based on this image pickup data, the image pickup data processing unit 125 calculates focus data such that the focus of visible light of the observation light source 117 is located on the surface 3 (S107).
【0094】
This focus data is sent to the stage control unit 115. The stage control unit 115 moves the Z-axis stage 113 in the Z-axis direction based on this focus data (S109). As a result, the focus of visible light of the observation light source 117 is located on the surface 3. The imaging data processing unit 125 calculates the enlarged image data of the surface 3 of the processing target 1 including the scheduled cutting line 5 based on the imaging data. This enlarged image data is sent to the monitor 129 via the overall control unit 127, so that the enlarged image near the line 5 scheduled to be cut is displayed on the monitor 129.
【0095】
The movement amount data determined in advance in step S103 is input to the overall control unit 127, and this movement amount data is sent to the stage control unit 115. Based on this movement amount data, the stage control unit 115 moves the workpiece 1 in the Z-axis direction by the Z-axis stage 113 to a position where the condensing point P of the laser beam L is inside the workpiece 1. S111).
【0096】
Next, as described above, the power and the numerical aperture are input to the overall control unit 127. Based on the input power data, the power of the laser beam L is adjusted by the power adjusting unit 401. Based on the input numerical aperture data, the numerical aperture is adjusted by the lens selection mechanism 403 selecting the focusing lens via the lens selection mechanism control unit 405. Further, these data are input to the dimension selection unit 411 (FIG. 32) of the overall control unit 127. As a result, the dimensions of the melting treatment spot formed inside the object 1 to be processed by the irradiation of the laser beam L of one pulse and the shape of the melting treatment spot are displayed on the monitor 129 (S112).
【0097】
Next, the laser light L is generated from the laser light source 101, and the laser light L is applied to the planned cutting line 5 on the surface 3 of the processing object 1. Since the condensing point P of the laser beam L is located inside the object to be processed 1, the melt processing region is formed only inside the object 1 to be processed. Then, the X-axis stage 109 and the Y-axis stage 111 are moved along the scheduled cutting line 5, and the melting processing region is formed inside the machining object 1 along the scheduled cutting line 5 (S113). Then, the object to be machined 1 is cut by bending the object to be machined 1 along the scheduled cutting line 5 (S115). As a result, the object 1 to be processed is divided into silicon chips.
【0098】
The effect of the first example will be described. According to this, the pulsed laser beam L is irradiated to the scheduled cutting line 5 under the condition of causing multiphoton absorption and by setting the condensing point P inside the object 1 to be processed. Then, by moving the X-axis stage 109 and the Y-axis stage 111, the condensing point P is moved along the scheduled cutting line 5. As a result, the modified region (for example, the crack region, the melt processing region, and the refractive index change region) is formed inside the workpiece 1 so as to be along the scheduled cutting line 5. If there is some starting point at the cutting point of the work object, the work object can be cut with a relatively small force. Therefore, by dividing the work target 1 along the scheduled cutting line 5 starting from the modified region, the work target 1 can be cut with a relatively small force. As a result, the workpiece 1 can be cut without causing unnecessary cracks off the scheduled cutting line 5 on the surface 3 of the workpiece 1.
【0099】
Further, according to the first example, the pulsed laser beam L is irradiated to the scheduled cutting line 5 under the condition that the processing object 1 causes multiphoton absorption and the condensing point P is set inside the processing object 1. ing. Therefore, the pulsed laser beam L passes through the object to be processed 1, and the pulsed laser beam L is hardly absorbed by the surface 3 of the object to be processed 1, so that the surface 3 is damaged such as melting due to the formation of the modified region. There is no.
【0100】
As described above, according to the first example, the machining object 1 can be cut without unnecessary cracking or melting off the scheduled cutting line 5 on the surface 3 of the machining object 1. Therefore, when the object to be processed 1 is, for example, a semiconductor wafer, the semiconductor chip can be cut out from the semiconductor wafer without causing unnecessary cracking or melting off the line to be cut. The same applies to a processed object having an electrode pattern formed on the surface and a processed object having an electronic device formed on the surface such as a glass substrate on which a display device such as a piezoelectric element wafer or a liquid crystal is formed. Therefore, according to the first example, it is possible to improve the yield of a product (for example, a display device such as a semiconductor chip, a piezoelectric device chip, or a liquid crystal) manufactured by cutting an object to be processed.
【0101】
Further, according to the first example, since the planned cutting line 5 on the surface 3 of the processing object 1 does not melt, the width of the planned cutting line 5 (in the case of a semiconductor wafer, for example, this width is between regions that are semiconductor chips). The interval.) Can be reduced. As a result, the number of products produced from one processed object 1 can be increased, and the productivity of the products can be improved.
【0102】
Further, according to the first example, since the laser beam is used for cutting the object 1 to be processed, more complicated processing than dicing using a diamond cutter becomes possible. For example, as shown in FIG. 37, even if the scheduled cutting line 5 has a complicated shape, cutting can be performed according to the first example. These effects are the same in the examples described later.
【0103】
[Second Example] Next, the second example of the present embodiment will be described focusing on the differences from the first example. FIG. 38 is a schematic configuration diagram of this laser processing apparatus 500. Among the components of the laser processing device 500, the same components as the components of the laser processing device 400 according to the first example shown in FIG. 31 are designated by the same reference numerals, and the description thereof will be omitted.
【0104】
In the laser processing apparatus 500, the beam expander 501 is arranged on the optical axis of the laser beam L between the power adjusting unit 401 and the dichroic mirror 103. The beam expander 501 has a variable magnification, and the beam expander 501 adjusts the beam diameter of the laser beam L to be large. The beam expander 501 is an example of a numerical aperture adjusting means. Further, the laser processing apparatus 500 includes one focusing lens 105 instead of the lens selection mechanism 403.
【0105】
The difference between the operation of the laser processing device 500 and the operation of the laser processing device of the first example is the adjustment of the numerical aperture based on the size of the numerical aperture input to the overall control unit 127. This will be described below. The overall control unit 127 is electrically connected to the beam expander 501. FIG. 38 omits this illustration. By inputting the magnitude of the numerical aperture to the overall control unit 127, the overall control unit 127 controls to change the magnification of the beam expander 501. As a result, the magnification of the beam diameter of the laser beam L incident on the condensing lens 105 is adjusted. Therefore, even if there is only one condensing lens 105, it is possible to adjust the numerical aperture of the optical system including the condensing lens 105 to be large. This will be described with reference to FIGS. 39 and 40.
【0106】
FIG. 39 is a diagram showing the focusing of the laser beam L by the focusing lens 105 when the beam expander 501 is not arranged. On the other hand, FIG. 40 is a diagram showing the focusing of the laser beam L by the focusing lens 105 when the beam expander 501 is arranged. As can be seen by comparing FIGS. 39 and 40, the numerical aperture of the optical system including the condensing lens 105 when the beam expander 501 is not arranged is large in the second example. Can be adjusted as
【0107】
[Third Example] Next, the third example of the present embodiment will be described focusing on the differences from the previous examples. FIG. 41 is a schematic configuration diagram of this laser processing apparatus 600. Among the components of the laser processing device 600, the same components as the components of the laser processing device according to the previous examples are designated by the same reference numerals, and the description thereof will be omitted.
【0108】
In the laser processing apparatus 600, instead of the beam expander 501, the iris diaphragm 601 is arranged on the optical axis of the laser beam L between the dichroic mirror 103 and the condensing lens 105. The effective diameter of the condensing lens 105 is adjusted by changing the size of the aperture of the iris diaphragm 601. The iris diaphragm 601 is an example of a numerical aperture adjusting means. Further, the laser processing apparatus 600 includes an iris diaphragm control unit 603 that controls changing the size of the opening of the iris diaphragm 601. The iris diaphragm control unit 603 is controlled by the overall control unit 127.
【0109】
The difference between the operation of the laser machining apparatus 600 and the operation of the laser machining apparatus of the previous examples is the adjustment of the numerical aperture based on the size of the numerical aperture input to the overall control unit 127. The laser processing device 600 adjusts the effective diameter of the condensing lens 105 to be reduced by changing the size of the aperture of the iris diaphragm 601 based on the size of the input numerical aperture. As a result, even if there is only one condensing lens 105, the numerical aperture of the optical system including the condensing lens 105 can be adjusted to be small. This will be described with reference to FIGS. 42 and 43.
【0110】
FIG. 42 is a diagram showing the focusing of the laser beam L by the focusing lens 105 when the iris diaphragm is not arranged. On the other hand, FIG. 43 is a diagram showing the focusing of the laser beam L by the focusing lens 105 when the iris diaphragm 601 is arranged. As can be seen by comparing FIGS. 42 and 43, the numerical aperture of the optical system including the condensing lens 105 when the iris diaphragm is not arranged is reduced in the third example. Can be adjusted.
【0111】
Next, a modified example of this embodiment will be described. FIG. 44 is a block diagram of the overall control unit 127 provided in the modified example of the laser processing apparatus of the present embodiment. The overall control unit 127 includes a power selection unit 417 and a correlation storage unit 413. The correlation storage unit 413 stores the correlation data shown in FIG. 35 in advance. The operator of the laser processing apparatus inputs the desired dimensions of the reforming spot into the power selection unit 417 using a keyboard or the like. The dimensions of the modified spot are determined in consideration of the thickness and material of the object to be processed. By this input, the power selection unit 417 selects the power corresponding to the dimension having the same value as this dimension from the correlation storage unit 413, and sends the power data to the power adjustment unit 401. Therefore, it is possible to form a modified spot having a desired size by performing laser processing with a laser processing apparatus adjusted to the magnitude of this power. This power magnitude data is also sent to monitor 129 to display the power magnitude. In this example, the numerical aperture is fixed and the power is variable. If the dimension having the same value as the input dimension is not stored in the correlation storage unit 413, the power data corresponding to the dimension having the closest value is sent to the power adjusting unit 401 and the monitor 129. This also applies to the modification described below.
【0112】
FIG. 45 is a block diagram of the overall control unit 127 provided in another modification of the laser processing apparatus of the present embodiment. The overall control unit 127 includes a numerical aperture selection unit 419 and a correlation storage unit 413. The difference from the modified example of FIG. 44 is that the numerical aperture is selected instead of the power. The data shown in FIG. 34 is stored in advance in the correlation storage unit 413. The operator of the laser processing apparatus inputs the desired dimensions of the reforming spot into the numerical aperture selection unit 419 using a keyboard or the like. As a result, the numerical aperture selection unit 419 selects the numerical aperture number corresponding to the dimension having the same value as this dimension from the correlation storage unit 413, and uses the numerical aperture data of the lens selection mechanism control unit 405, the beam expander 501, or the beam expander 501. Send to the iris aperture control unit 603. Therefore, it is possible to form a modified spot having a desired size by performing laser processing with a laser processing apparatus adjusted to the numerical aperture. The data of the numerical aperture size is also sent to the monitor 129, and the numerical aperture size is displayed. In this example, the power is fixed and the numerical aperture is variable.
【0113】
FIG. 46 is a block diagram of the overall control unit 127 provided in still another modification of the laser processing apparatus of the present embodiment. The overall control unit 127 includes a set selection unit 421 and a correlation storage unit 413. The difference from the examples in FIGS. 44 and 45 is that both power and numerical aperture are selected. The correlation storage unit 413 stores in advance the data of the correlation between the power and numerical aperture set of FIG. 33 and the dimensions. The operator of the laser processing apparatus inputs the desired dimensions of the reforming spot into the set selection unit 421 using a keyboard or the like. As a result, the set selection unit 421 selects a set of power and numerical aperture corresponding to the dimension having the same value as this dimension from the correlation storage unit 413. The power data of the selected set is sent to the power adjustment unit 401. On the other hand, the numerical aperture data of the selected set is sent to the lens selection mechanism control unit 405, the beam expander 501, or the iris diaphragm control unit 603. Therefore, it is possible to form a modified spot having a desired size by laser machining with a laser machining device adjusted to the size of this set of power and numerical aperture. Data on the power and numerical aperture of this set is also sent to the monitor 129, and the power and numerical aperture size are displayed.
【0114】
According to these modifications, the dimensions of the modified spot can be controlled. Therefore, by reducing the size of the modified spot, it is possible to precisely cut along the planned cutting line of the object to be processed, and it is possible to obtain a flat cut surface. When the thickness of the object to be processed is large, the object to be processed can be cut by increasing the size of the modified spot.
【0115】
[Effect of the invention]
According to the laser processing apparatus and the laser processing method according to the present invention, the object to be machined can be cut without melting or cracking off the planned cutting line on the surface of the object to be machined. Therefore, it is possible to improve the yield and productivity of products (for example, display devices such as semiconductor chips, piezoelectric device chips, and liquid crystals) manufactured by cutting an object to be processed.
【0116】
According to the laser processing apparatus and the laser processing method according to the present invention, the dimensions of the modified spot can be controlled. Therefore, the object to be machined can be precisely cut along the planned cutting line, and a flat cut surface can be obtained.
【0117】
According to the laser processing apparatus according to the present invention, the dimensions of the modified spots formed under these conditions are displayed on the display means based on the input of at least one of the magnitude of the power and the magnitude of the numerical aperture. To. Therefore, the dimensions of the modified spot can be known before laser machining.
【0118】
According to the laser processing apparatus according to the present invention, at least one of the magnitude of power and the magnitude of numerical aperture is adjusted so that the modified spot has this dimension based on the input of the dimension of the modified spot. To do. Therefore, it is possible to form a modified spot having a desired size.
[Simple explanation of drawings]
[Figure 1]
It is a top view of the processing object during laser processing by the laser processing method which concerns on this embodiment.
[Figure 2]
It is sectional drawing along the line II-II of the processing object shown in FIG.
[Fig. 3]
It is a top view of the processing object after laser processing by the laser processing method which concerns on this embodiment.
[Fig. 4]
It is sectional drawing along the IV-IV line of the processing object shown in FIG.
[Fig. 5]
It is sectional drawing along the VV line of the processing object shown in FIG.
[Fig. 6]
It is a top view of the processing object cut by the laser processing method which concerns on this embodiment.
[Fig. 7]
It is a graph which shows the relationship between the electric field strength and the size of a crack in the laser processing method which concerns on this embodiment.
[Fig. 8]
It is sectional drawing of the processing object in the 1st process of the laser processing method which concerns on this embodiment.
[Fig. 9]
It is sectional drawing of the processing object in the 2nd step of the laser processing method which concerns on this embodiment.
[Fig. 10]
It is sectional drawing of the processing object in the 3rd process of the laser processing method which concerns on this embodiment.
[Fig. 11]
It is sectional drawing of the processing object in the 4th process of the laser processing method which concerns on this embodiment.
[Fig. 12]
It is a figure showing the photograph of the cross section of a part of the silicon wafer cut by the laser processing method which concerns on this embodiment.
[Fig. 13]
It is a graph which shows the relationship between the wavelength of the laser light and the transmittance inside the silicon substrate in the laser processing method which concerns on this embodiment.
[Fig. 14]
It is a top view of the processing object when the crack spot is formed relatively large by using the laser processing method which concerns on this embodiment.
[Fig. 15]
It is sectional drawing which cut along the XV-XV on the planned cutting line shown in FIG.
[Fig. 16]
It is sectional drawing which cut along the XVI-XVI orthogonal to the cut line to be shown in FIG.
[Fig. 17]
It is sectional drawing which cut along the XVII-XVII orthogonal to the planned cutting line shown in FIG.
[Fig. 18]
It is sectional drawing which cut along the XVIII-XVIII orthogonal to the planned cutting line shown in FIG.
[Fig. 19]
It is a top view which cut the processing object shown in FIG. 14 along the planned cutting line.
[Fig. 20]
It is sectional drawing of the processing object along the planned cutting line when the crack spot is formed relatively small by using the laser processing method which concerns on this embodiment.
[Fig. 21]
It is a top view which cut the processing object shown in FIG. 20 along the planned cutting line.
[Fig. 22]
It is sectional drawing of the processing object which shows the state which the pulse laser light is focused inside the processing object using the condensing lens of a predetermined numerical aperture.
[Fig. 23]
FIG. 22 is a cross-sectional view of a work object including a crack spot formed due to absorption of multiple photons by irradiation with a laser beam shown in FIG. 22.
[Fig. 24]
It is sectional drawing of the processing object in the case of using the condensing lens of the numerical aperture larger than the example shown in FIG.
[Fig. 25]
FIG. 24 is a cross-sectional view of a work object including a crack spot formed due to absorption of multiple photons by irradiation with a laser beam shown in FIG. 24.
[Fig. 26]
FIG. 5 is a cross-sectional view of an object to be processed when a pulsed laser beam having a power smaller than that shown in FIG. 22 is used.
[Fig. 27]
FIG. 26 is a cross-sectional view of a work object including a crack spot formed due to absorption of multiple photons by irradiation with a laser beam shown in FIG. 26.
[Fig. 28]
It is sectional drawing of the processing object when the pulse laser light of power smaller than the example shown in FIG. 24 is used.
[Fig. 29]
FIG. 28 is a cross-sectional view of a work object including a crack spot formed due to absorption of multiple photons by irradiation with a laser beam shown in FIG. 28.
[Fig. 30]
It is sectional drawing which cut along XXX-XXX orthogonal to the planned cutting line shown in FIG.
[Fig. 31]
It is a schematic block diagram of the laser processing apparatus which concerns on 1st Example of this Embodiment.
[Fig. 32]
It is a block diagram which shows a part of an example of the whole control part provided in the laser processing apparatus which concerns on this embodiment.
[Fig. 33]
It is a figure which shows an example of the table of the correlation storage part included in the whole control part of the laser processing apparatus which concerns on this embodiment.
[Fig. 34]
It is a figure which shows another example of the table of the correlation storage part included in the whole control part of the laser processing apparatus which concerns on this embodiment.
[Fig. 35]
It is a figure which shows still another example of the table of the correlation storage part included in the whole control part of the laser processing apparatus which concerns on this embodiment.
[Fig. 36]
It is a flowchart for demonstrating the laser processing method which concerns on 1st Example of this Embodiment.
[Fig. 37]
It is a top view of the processing object for demonstrating the pattern which can be cut by the laser processing method which concerns on 1st Example of this Embodiment.
[Fig. 38]
It is a schematic block diagram of the laser processing apparatus which concerns on the 2nd example of this embodiment.
[Fig. 39]
It is a figure which shows the focusing of the laser light by the focusing lens when the beam expander is not arranged.
[Fig. 40]
It is a figure which shows the focusing of the laser light by the focusing lens when a beam expander is arranged.
[Fig. 41]
It is a schematic block diagram of the laser processing apparatus which concerns on 3rd example of this embodiment.
[Fig. 42]
It is a figure which shows the focusing of the laser light by the focusing lens when the iris diaphragm is not arranged.
[Fig. 43]
It is a figure which shows the focusing of the laser light by the focusing lens when the iris diaphragm is arranged.
[Fig. 44]
It is a block diagram of an example of the whole control unit provided in the modification of the laser processing apparatus of this embodiment.
[Fig. 45]
It is a block diagram of another example of the whole control part provided in the modification of the laser processing apparatus of this embodiment.
[Fig. 46]
It is a block diagram of still another example of the whole control part provided in the modification of the laser processing apparatus of this embodiment.
[Explanation of symbols]
1 ... Processing target, 3 ... Surface, 5 ... Scheduled cutting line, 7 ... Modified area, 9 ... Crack area, 11 ... Silicon wafer, 13 ... Melting process Region, 41 ... Region, 43 ... Cut surface, 90 ... Crack spot, 101 ... Laser light source, 105, 105a, 105b, 105c ... Condensing lens, 109 ... X-axis stage , 111 ... Y-axis stage, 113 ... Z-axis stage, 400 ... Laser processing device, 401 ... Power adjustment unit, 403 ... Lens selection mechanism, 411 ... Dimension selection unit, 413 Correlation storage unit, 415 Image creation unit, 417 Power selection unit, 419 Numerical aperture selection unit, 421 Group selection unit, 500 Laser processing device, 501 Beam expander, 600 Laser processing equipment, 601 Iridescent diaphragm, P Focus point
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Numbers
- Publication
- 2002-205181
- Publication, DOCDB
- 2002205181
- Publication, EPODOC
- JP2002205181
- Application
- 278665
- Application, DOCDB
- 2001278665
- Application, EPODOC
- JP20010278665
Titles2
- Japanese
- 【発明の名称】レーザ加工装置及びレーザ加工方法
- English
- [Title of Invention] Laser Machining Equipment and Laser Machining Method
Classification
- CPC, 4
- B23K26/40
- B23K26/53
- B23K2101/40
- B23K2103/50
- IPC, 8
- B23K26 40
- B23K26 00
- B23K26 02
- B23K26 03
- B23K26 046
- B23K26 064
- B23K26 38
- C03B33 08