Method for laser beam machining

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to 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, this method also melts the periphery of the region to be cut on the surface of the object to be processed. 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 element located near the above 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, or 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 method that does 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 method according to the present invention includes a step of determining the position of a condensing point of laser light in the thickness direction of the object to be processed based on the thickness and refractive index of the object to be processed, and the thickness of the object to be processed. The position of the focusing point of the laser light in the direction is determined so that the focusing point is aligned with the inside of the object to be processed and the laser light is irradiated, and the object to be processed is aligned with the planned cutting line of the object to be processed. It is characterized by including a step of forming a modified region inside.

【0007】

According to the laser processing method according to the present invention, a modified region is formed inside the object to be processed by irradiating the inside of the object to be processed with a laser beam by aligning a condensing point. 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. According to the laser machining method according to the present invention, the machining target can be cut by cracking the machining target 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 method according to the present invention, a modified region is locally formed 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.

【0009】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the laser processing method according to the present embodiment, a modified region is formed by multiphoton absorption. Multiphoton absorption is a phenomenon that occurs when the intensity of laser light is extremely high. First, multiphoton absorption will be briefly described.

【0010】

Material absorption bandgap E_GWhen the photon energy hν is smaller than that, it becomes optically transparent. Therefore, the condition for absorption in the material is hν> E_GIs. However, even if it is optically transparent, if the intensity of the laser beam is made very large, nhν> E_GAbsorption 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.²), For example, the peak power density is 1 × 10.⁸(W / cm²) 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.²).

【0011】

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.

【0012】

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.

【0013】

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.

【0014】

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.

【0015】

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 work target after the modified region is formed, so that the work target is cracked and the work target is cut from the modified region 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 spontaneous cracking, the crack does not advance to the portion where the modified region is not formed on the surface of the cut portion, and only the portion where the modified portion is formed can be cut. The division can be controlled 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.

【0016】

By the way, as the modified region formed by multiphoton absorption in this embodiment, there are the following (1) to (3).

【0017】

(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)₃The electric field strength at the condensing point is 1 × 10 by aligning the condensing point inside the (piezoelectric material consisting of).⁸(W / cm²) 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 × 10.¹²(W / cm²). 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".

【0018】

The present inventor experimentally determined the relationship between the electric field strength and the size of cracks. The experimental conditions are as follows. (A) Object to be processed: Pyrex (registered trademark) 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^-8cm²Oscillation form: Q-switched pulse Repeat frequency: 100kHz Pulse width: 30ns Output: Output <1mJ / pulse Laser light quality: TEM₀₀Polarization 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.₀₀Means that the light collecting property is high and the light can be collected up to the wavelength of the laser beam.

【0019】

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 10¹¹(W / cm²It 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.

【0020】

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, and the laser light L is irradiated to the work target 1, and a crack region is formed 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.

【0021】

(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 × 10.⁸(W / cm²) 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 × 10.¹²(W / cm²). The pulse width is preferably 1 ns to 200 ns, for example.

【0022】

The present inventor has experimentally confirmed that a melt processing region is formed inside the silicon wafer. The experimental conditions are as follows. (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^-8cm²Oscillation form: Q-switched pulse Repeat frequency: 100kHz Pulse width: 30ns Output: 20 μJ / pulse Laser light quality: TEM₀₀Polarization 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 [0023]

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.

【0024】

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.

【0025】

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. 66 (April 2000). Are listed.

【0026】

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.

【0027】

(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 × 10.⁸(W / cm²) 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 × 10.¹²(W / cm²). The pulse width is preferably 1 ns or less, more preferably 1 ps or less, for example. 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 .

【0028】

Next, a specific example of this embodiment will be described.

【0029】

[First Example] The laser processing method according to the first example of the present embodiment will be described. FIG. 14 is a schematic configuration diagram of a laser processing apparatus 100 that can be used in this method. The laser processing apparatus 100 includes a laser light source 101 that generates a laser beam L, a laser light source control unit 102 that controls the laser light source 101 to adjust the output of the laser beam L, a pulse width, and the like, and a reflection function of the laser beam L. A dichroic mirror 103 that has a light source L and is arranged so as to change the direction of the optical axis of the laser light L by 90 °, a condensing lens 105 that condenses the laser light L reflected by the dichroic mirror 103, and a condensing lens 105. A mounting table 107 on which the processing object 1 irradiated with the laser beam L focused by the lens 105 is placed, an X-axis stage 109 for moving the mounting table 107 in the X-axis direction, and a mounting table 107 are provided. A Y-axis stage 111 for moving the mounting table 107 in the Y-axis direction orthogonal to the X-axis direction, and a Z-axis stage 113 for moving the mounting table 107 in the Z-axis direction orthogonal to the X-axis and the Y-axis direction. It includes a stage control unit 115 that controls the movement of the stages 109,111,113.

【0030】

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.

【0031】

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: YVO₄There are lasers, Nd: YLF lasers and titanium sapphire lasers. When forming crack regions and melt processing regions, Nd: YAG laser, Nd: YVO₄It 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.

【0032】

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. In the present invention, the laser beam means to include a laser beam. The condensing lens 105 is an example 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 lens 105 in the Z-axis direction, the focusing point of the laser beam can be aligned with the inside of the object to be processed.

【0033】

The laser processing apparatus 100 further includes an observation light source 117 that generates visible light for illuminating 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.

【0034】

The laser processing apparatus 100 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.

【0035】

The laser processing apparatus 100 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 100, 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.

【0036】

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 100 is controlled. Therefore, the overall control unit 127 functions as a computer unit.

【0037】

Next, the laser processing method according to the first example of the present embodiment will be described with reference to FIGS. 14 and 15. FIG. 15 is a flowchart for explaining this laser processing method. The object to be processed 1 is a silicon wafer.

【0038】

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 a laser beam 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.

【0039】

The object 1 to be machined is placed on the mounting table 107 of the laser machining apparatus 100. 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).

【0040】

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 focal point of the 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.

【0041】

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).

【0042】

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.

【0043】

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 planned 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.

【0044】

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.

【0045】

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.

【0046】

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.

【0047】

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. 16, 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.

【0048】

The number of laser light sources is not limited to one, and may be multiple. For example, FIG. 17 is a schematic diagram illustrating a laser processing method according to the first example of the present embodiment in which a plurality of laser light sources are used. This irradiates the three laser beams emitted from the three laser light sources 15, 17, and 19 from different directions by aligning the condensing point P inside the processing object 1. Each laser beam from the laser light sources 15 and 17 is incident on the surface 3 of the object 1 to be processed. The laser beam from the laser light source 19 is incident on the back surface 3 of the object 1 to be processed. According to this, since a plurality of laser light sources are used, even if the laser light is a continuous wave laser light having a smaller power than the pulsed laser light, the electric field strength at the focusing point is set to a magnitude that causes multiphoton absorption. It becomes possible. For the same reason, it is possible to generate multiphoton absorption without a condensing lens. In this example, the focusing point P is formed by three laser light sources 15, 17, and 19, but the present invention is not limited to this, and a plurality of laser light sources may be used.

【0049】

FIG. 18 is a schematic diagram illustrating another laser processing method according to the first example of the present embodiment in which a plurality of laser light sources are used. This example includes three array light sources 25, 27, 29 in which a plurality of laser light sources 23 are arranged in a row along a line 5 to be cut. The laser light emitted from the laser light sources 23 arranged in the same row in each of the array light source units 25, 27, and 29 is one focusing point (for example, the focusing point P).₁) Is formed. According to this example, a plurality of focusing points P along the planned cutting line 5.₁, P₂Since, ... Can be formed at the same time, the processing speed can be improved. Further, in this example, it is also possible to form a plurality of rows of modified regions at the same time by performing a laser scan on the surface 3 in a direction orthogonal to the planned cutting line 5.

【0050】

[Second Example] Next, a second example of the present embodiment will be described. An example of this is a cutting method and cutting device for light transmissive materials. The light transmissive material is an example of an object to be processed. In this example, LiTaO as a light-transmitting material₃A piezoelectric element wafer (board) having a thickness of about 400 μm is used.

【0051】

The cutting apparatus according to the second example includes the laser processing apparatus 100 shown in FIG. 14 and the apparatus shown in FIGS. 19 and 20. The apparatus shown in FIGS. 19 and 20 will be described. The piezoelectric element wafer 31 is held by a wafer sheet (film) 33 as a holding means. The wafer sheet 33 has elasticity because the surface on the side holding the piezoelectric element wafer 31 is made of an adhesive resin tape or the like. The wafer sheet 33 is sandwiched between the sample holders 35 and set on the mounting table 107. As shown in FIG. 19, the piezoelectric element wafer 31 includes a large number of piezoelectric device chips 37 that are later cut and separated. Each piezoelectric device chip 37 has a circuit unit 39. The circuit unit 39 is formed on the surface of the piezoelectric element wafer 31 for each piezoelectric device chip 37, and a predetermined gap α (about 80 μm) is formed between adjacent circuit units 39. Note that FIG. 20 shows a state in which a minute crack region 9 as a modified portion is formed only inside the piezoelectric element wafer 31.

【0052】

Next, a method for cutting the light-transmitting material according to the second example will be described with reference to FIG. First, a light-transmitting material to be cut (LiTaO in the second example)₃The light absorption characteristics of the piezoelectric element wafer 31) made of the above are measured (S201). The light absorption characteristics can be measured by using a spectrophotometer or the like. When the light absorption characteristics are measured, a laser light source 101 that emits a laser beam L having a wavelength that is transparent or has little absorption with respect to the material to be cut is selected based on the measurement result (S203). In the second example, a pulse wave (PW) type YAG laser having a fundamental wave wavelength of 1064 nm is selected. This YAG laser has a pulse repetition frequency of 20 Hz, a pulse width of 6 ns, and a pulse energy of 300 μJ. The spot diameter of the laser beam L emitted from the YAG laser is about 20 μm.

【0053】

Next, the thickness of the material to be cut is measured (S205). When the thickness of the material to be cut is measured, based on the measurement result, the material to be cut in the optical axis direction of the laser light L so that the focusing point of the laser light L is located inside the material to be cut. The amount of displacement (movement amount) of the condensing point of the laser beam L from the surface (incident surface of the laser beam L) is determined (S207). The displacement amount (movement amount) of the condensing point of the laser beam L is set to, for example, 1/2 the thickness of the material to be cut, corresponding to the thickness and the refractive index of the material to be cut.

【0054】

As shown in FIG. 22, the position of the focusing point P of the actual laser beam L is determined by the difference between the refractive index in the atmosphere of the material to be cut (for example, air) and the refractive index of the material to be cut. The laser beam L focused by the lens 105 is located deeper than the surface of the material to be cut (refractive index wafer 31) than the position of the focusing point Q. That is, in the case of air, the relationship "movement amount of the Z-axis stage 113 in the optical axis direction of the laser light L x refractive index of the material to be cut = actual movement amount of the condensing point of the laser light L" is established. Become. The displacement amount (movement amount) of the condensing point of the laser beam L is set in consideration of the above-mentioned relationship (thickness and refractive index of the material to be cut). After that, the cutting held on the wafer sheet 33 with respect to the mounting table 107 arranged on the XYZ-axis stage (in this embodiment, composed of the X-axis stage 109, the Y-axis stage 111, and the Z-axis stage 113). Place the target material (S209). When the material to be cut is placed, light is emitted from the observation light source 117, and the emitted light is applied to the material to be cut. Then, based on the image pickup result of the image pickup device 121, the Z-axis stage 113 is moved so that the focusing point of the laser beam L is located on the surface of the material to be cut, and the focus is adjusted (S211). Here, the surface observation image of the piezoelectric element wafer 31 obtained by the observation light source 117 is imaged by the image pickup element 121, and the image pickup data processing unit 125 cuts off the light emitted from the observation light source 117 based on the image pickup result. The moving position of the Z-axis stage 113 is determined so as to focus on the surface of the target material, and the image is output to the stage control unit 115. In the stage control unit 115, the moving position of the Z-axis stage 113 is such that the light emitted from the observation light source 117 focuses on the surface of the material to be cut, that is, based on the output signal from the imaging data processing unit 125. The Z-axis stage 113 is controlled so that the condensing point of the laser beam L is positioned on the surface of the material to be cut.

【0055】

When the focus adjustment of the light emitted from the observation light source 117 is completed, the focusing point of the laser beam L is moved to the focusing point corresponding to the thickness and the refractive index of the material to be cut (S213). Here, the entire Z-axis stage 113 is moved in the optical axis direction of the laser beam L by the amount of displacement of the focusing point of the laser beam L determined according to the thickness and the refractive index of the material to be cut. The control unit 127 sends an output signal to the stage control unit 115, and the stage control unit 115 that receives the output signal controls the moving position of the Z-axis stage 113. As described above, by moving the Z-axis stage 113 in the optical axis direction of the laser beam L by the amount of displacement of the focusing point of the laser beam L determined according to the thickness and the refractive index of the material to be cut. , The placement of the focusing point of the laser beam L inside the material to be cut is completed (S215).

【0056】

When the arrangement of the condensing point of the laser beam L inside the material to be cut is completed, the laser light L is irradiated to the material to be cut, and the X-axis stage 109 and the Y-axis stage 111 are moved according to a desired cutting pattern. (S217). As shown in FIG. 22, the laser beam L emitted from the laser light source 101 has a predetermined gap α (80 μm as described above) formed between the adjacent circuit portions 39 by the condensing lens 105. The light is collected so that the light collecting point P is located inside the piezoelectric element wafer 31 facing the surface. The desired cutting pattern described above is set so that the gap formed between the adjacent circuit portions 39 is irradiated with the laser beam L in order to separate the plurality of piezoelectric device chips 37 from the piezoelectric element wafer 31. Therefore, the laser beam L is irradiated while checking the irradiation state of the laser beam L on the monitor 129.

【0057】

Here, the laser beam L irradiated to the material to be cut is a circuit formed on the surface of the piezoelectric element wafer 31 (the surface on which the laser beam L is incident) by the condensing lens 105 as shown in FIG. The part 39 is focused at an angle at which the laser beam L is not irradiated. In this way, by condensing the laser beam L at an angle at which the circuit unit 39 is not irradiated with the laser beam L, it is possible to prevent the laser beam L from being incident on the circuit unit 39, and the circuit unit 39 can be subjected to the laser beam L. Can be protected from.

【0058】

The laser beam L emitted from the laser light source 101 is focused so that the focusing point P is located inside the piezoelectric element wafer 31, and the energy density of the laser beam L at the focusing point P is the optics of the material to be cut. When the threshold value of physical damage or optical insulation failure is exceeded, a minute crack region 9 is formed only in the condensing point P and its vicinity inside the piezoelectric element wafer 31 as a material to be cut. At this time, the front surface and the back surface of the material to be cut (piezoelectric element wafer 31) are not damaged.

【0059】

Next, a point of moving the focusing point of the laser beam L to form a crack will be described with reference to FIGS. 23 to 27. By irradiating the material 32 (light transmitting material) having a substantially rectangular shape shown in FIG. 23 with the laser light L so that the condensing point of the laser light L is located inside the material 32 to be cut. As shown in FIGS. 24 and 25, a minute crack region 9 is formed only in the condensing point and its vicinity inside the material 32 to be cut. Further, the scanning of the laser beam L or the movement of the material 32 to be cut is controlled so that the condensing point of the laser beam L moves in the longitudinal direction D of the material 32 to be cut intersecting the optical axis of the laser beam L. ..

【0060】

Since the laser beam L is emitted in a pulse shape from the laser light source 101, when the laser beam L is scanned or the material 32 to be cut is moved, the crack region 9 is the object to be cut as shown in FIG. 25. A plurality of crack regions 9 are formed along the longitudinal direction D of the material 32 with an interval corresponding to the scanning speed of the laser beam L or the moving speed of the material 32 to be cut. By slowing the scanning speed of the laser beam L or the moving speed of the material 32 to be cut, as shown in FIG. 26, the distance between the crack regions 9 is shortened and the number of crack regions 9 formed is increased. Is also possible. Further, by further reducing the scanning speed of the laser beam L or the moving speed of the material to be cut, as shown in FIG. 27, the crack region 9 is the scanning direction of the laser light L or the moving direction of the material 32 to be cut. That is, it is continuously formed along the moving direction of the condensing point of the laser beam L. Adjusting the spacing between the crack regions 9 (the number of crack regions 9 formed) can also be achieved by changing the relationship between the repetition frequency of the laser beam L and the moving speed of the material 32 to be cut (X-axis stage or Y-axis stage). It is feasible. Further, the throughput can be improved by increasing the repetition frequency of the laser beam L and the moving speed of the material 32 to be cut.

【0061】

When the crack region 9 is formed along the desired cutting pattern described above (S219), stress is generated in the material to be cut, particularly in the portion where the crack region 9 is formed, by applying a physical external force or changing the environment. , The crack region 9 formed only inside the material to be cut (condensing point and its vicinity) is grown, and the material to be cut is cut at the position where the crack region 9 is formed (S221).

【0062】

Next, with reference to FIGS. 28 to 32, cutting of the material to be cut by applying a physical external force will be described. First, the material to be cut (piezoelectric element wafer 31) in which the crack region 9 is formed along the desired cutting pattern is placed in the cutting device in a state of being held by the wafer sheet 33 sandwiched between the sample holders 35. The cutting device includes a suction chuck 34 as described later, a suction pump (not shown) to which the suction chuck 34 is connected, a pressure needle 36 (pressing member), and a pressure needle drive for moving the pressure needle 36. It has means (not shown) and the like. As the pressurizing needle driving means, an electric or hydraulic actuator can be used. In FIGS. 28 to 32, the circuit unit 39 is not shown.

【0063】

When the piezoelectric element wafer 31 is arranged in the cutting device, the suction chuck 34 is brought closer to the position corresponding to the piezoelectric device chip 37 to be separated, as shown in FIG. 28. As shown in FIG. 29, the piezoelectric device chip 37 (piezoelectric element wafer) that separates into the suction chuck 34 by operating the suction pump device in a state of being close to or in contact with the piezoelectric device chip 37 that separates the suction chuck 34. 31) is adsorbed. When the piezoelectric device chip 37 (piezoelectric element wafer 31) to be separated is attracted to the suction chuck 34, it is separated from the back surface of the wafer sheet 33 (the back surface of the surface on which the piezoelectric element wafer 31 is held) as shown in FIG. Move the pressurizing needle 36 to the position corresponding to the piezoelectric device chip 37.

【0064】

When the pressure needle 36 is further moved after the pressure needle 36 comes into contact with the back surface of the wafer sheet 33, the wafer sheet 33 is deformed and stress is applied to the piezoelectric element wafer 31 from the outside by the pressure needle 36. Stress is generated in the wafer portion where the crack region 9 is formed, and the crack region 9 grows. As the crack region 9 grows to the front and back surfaces of the piezoelectric wafer 31, the piezoelectric wafer 31 is cut at the ends of the separating piezoelectric device chips 37, as shown in FIG. 31, and the piezoelectric device chips 37 Will be separated from the piezoelectric element wafer 31. Since the wafer sheet 33 has adhesiveness as described above, it is possible to prevent the cut-separated piezoelectric device chip 37 from scattering.

【0065】

When the piezoelectric device chip 37 is separated from the piezoelectric element wafer 31, the suction chuck 34 and the pressure needle 36 are moved away from the wafer sheet 33. When the suction chuck 34 and the pressure needle 36 move, the separated piezoelectric device chip 37 is attracted to the suction chuck 34 and is separated from the wafer sheet 33 as shown in FIG. 32. At this time, using an ion air blower (not shown), ion air is sent in the direction of arrow B in FIG. 32, and is held by the piezoelectric device chip 37, which is separated and attracted to the suction chuck 34, and the wafer sheet 33. The piezoelectric element wafer 31 (surface) is cleaned with ion air. Instead of ion-air cleaning, a suction device may be provided to clean the piezoelectric device chip 37 and the piezoelectric element wafer 31 that have been cut and separated by sucking dust or the like. As a method of cutting the material to be cut due to an environmental change, there is a method of giving a temperature change to the material to be cut in which a crack region 9 is formed only inside. In this way, by giving a temperature change to the material to be cut, thermal stress is generated in the material portion where the crack region 9 is formed, and the crack region 9 is grown to cut the material to be cut. it can.

【0066】

As described above, in the second example, the condensing point of the laser beam L emitted from the laser light source 101 by the condensing lens 105 is located inside the light transmitting material (piezoelectric element wafer 31). The energy density of the laser beam L at the condensing point exceeds the threshold of optical damage or optical insulation destruction of the light transmitting material, and the condensing point inside the light transmitting material and its A minute crack region 9 is formed only in the vicinity. Then, since the light-transmitting material is cut at the position of the formed crack region 9, the amount of dust generated is extremely low, and the possibility of dicing scratches, chipping, cracks on the surface of the material, etc. is extremely low. Further, since the light-transmitting material is cut along the crack region 9 formed by the optical damage or the optical dielectric breakdown of the light-transmitting material, the cutting direction stability is improved and the cutting direction can be controlled. It can be done easily. In addition, the dicing width can be reduced as compared with dicing with a diamond cutter, and the number of light-transmitting materials cut from one light-transmitting material can be increased. As a result, according to the second example, the light-transmitting material can be cut extremely easily and appropriately.

【0067】

Further, by generating stress in the material to be cut by applying a physical external force or changing the environment, the formed crack region 9 is grown to cut the light transmissive material (piezoelectric element wafer 31), so that the material is formed. The light transmissive material can be reliably cut at the position of the crack region 9.

【0068】

Further, since the light transmissive material (piezoelectric element wafer 31) is stressed by using the pressure needle 36 to grow the crack region 9 and cut the light transmissive material, the crack region 9 formed is formed. The light-transmitting material can be cut more reliably at the position of.

【0069】

Further, when the piezoelectric element wafer 31 (light transmissive material) in which a plurality of circuit portions 39 are formed is cut and separated for each piezoelectric device chip 37, it is formed between adjacent circuit portions 39 by a condensing lens 105. The laser beam L is focused so that the focusing point is located inside the wafer portion facing the gap, and the crack region 9 is formed. Therefore, at the position of the gap formed between the adjacent circuit portions 39, The piezoelectric element wafer 31 can be reliably cut.

【0070】

Further, by moving the light transmissive material (piezoelectric element wafer 31) or scanning the laser beam L to move the condensing point in a direction intersecting the optical axis of the laser beam L, for example, in a direction orthogonal to the optical axis, the crack region 9 Is continuously formed along the moving direction of the condensing point, the directional stability of cutting is further improved, and the direction of cutting can be controlled more easily.

【0071】

Further, in the second example, since there is almost no dust-generated powder, lubricating cleaning water for preventing the dust-generated powder from scattering becomes unnecessary, and a dry process can be realized in the cutting process.

【0072】

Further, in the second example, since the modified portion (crack region 9) is formed by non-contact processing with the laser beam L, problems such as blade durability and replacement frequency in dicing with a diamond cutter occur. There is no such thing. Further, in the second example, as described above, since the modified portion (crack region 9) is formed by non-contact processing with the laser beam L, the light transmissive material is not completely cut and the light transmissive. It is possible to cut a light-transmitting material along a cutting pattern that cuts out a sex material. The present invention is not limited to the second example described above. For example, the light transmissive material is not limited to the piezoelectric element wafer 31, but may be a semiconductor wafer, a glass substrate, or the like. The laser light source 101 can also be appropriately selected according to the light absorption characteristics of the light-transmitting material to be cut. Further, in the second example, the modified portion is formed by irradiating the laser beam L to form a minute crack region 9, but the present invention is not limited to this. For example, by using an ultrashort pulse laser light source (for example, a femtosecond (fs) laser) as the laser light source 101, it is possible to form a modified portion due to a change in the refractive index (high refractive index). The light-transmitting material can be cut without generating the crack region 9 by utilizing the change in the characteristics.

【0073】

Further, in the laser processing apparatus 100, the focus of the laser beam L is adjusted by moving the Z-axis stage 113, but the focus is not limited to this. The focus may be adjusted by moving the light in the direction.

【0074】

Further, in the laser processing apparatus 100, the X-axis stage 109 and the Y-axis stage 111 are moved according to a desired cutting pattern, but the laser beam L is scanned according to a desired cutting pattern. You may try to do it.

【0075】

Further, after the piezoelectric element wafer 31 is attracted to the suction chuck 34, the piezoelectric element wafer 31 is cut by the pressure needle 36, but the present invention is not limited to this, and the piezoelectric element wafer 31 is cut by the pressure needle 36. After cutting the wafer, the cut and separated piezoelectric device chip 37 may be attracted to the suction chuck 34. After the piezoelectric element wafer 31 is attracted to the suction chuck 34, the surface of the cut and separated piezoelectric device chip 37 is covered with the suction chuck 34 by cutting the piezoelectric element wafer 31 with the pressure needle 36. Therefore, it is possible to prevent dust and the like from adhering to the surface of the piezoelectric device chip 37.

【0076】

Further, by using an image sensor 121 for infrared rays, the focus can be adjusted by using the reflected light of the laser beam L. In this case, it is necessary to use a half mirror instead of using the dichroic mirror 103 and to dispose an optical element between the half mirror and the laser light source 101 so as to suppress the return light to the laser light source 101. At this time, the output of the laser beam L emitted from the laser light source 101 during the focus adjustment is higher than the output for crack formation so that the material to be cut is not damaged by the laser beam L for the focus adjustment. It is preferable to set the energy value to a low value.

【0077】

The features of the present invention will be described below from the viewpoint of the second example.

【0078】

In the method for cutting a light-transmitting material according to the present invention, the laser light emitted from a laser light source is collected so that the focusing point is located inside the light-transmitting material, and the light is collected inside the light-transmitting material. It is characterized by including a modified portion forming step of forming a modified portion only at the light spot and its vicinity, and a cutting step of cutting a light-transmitting material at the position of the formed modified portion. ..

【0079】

In the method for cutting a light-transmitting material according to the present invention, in the process of forming a modified portion, the laser light is focused so that the focusing point of the laser light is located inside the light-transmitting material, thereby transmitting light. A modified portion is formed only at the condensing point inside the material and its vicinity. In the cutting process, the light-transmitting material is cut at the position of the formed modified part, the amount of dust generated is extremely low, and there is a possibility that dicing scratches, chipping, cracks on the material surface, etc. may occur. It will be extremely low. Further, since the light-transmitting material is cut at the position of the formed modified portion, the cutting direction stability is improved and the cutting direction can be easily controlled. In addition, the dicing width can be reduced as compared with dicing with a diamond cutter, and the number of light-transmitting materials cut from one light-transmitting material can be increased. As a result, according to the present invention, the light-transmitting material can be cut extremely easily and appropriately.

【0080】

Further, in the method for cutting a light-transmitting material according to the present invention, since there is almost no dust-generated powder, lubricating cleaning water for preventing scattering of the dust-generated powder becomes unnecessary, and a dry process can be performed in the cutting process. It can be realized.

【0081】

Further, in the method for cutting a light-transmitting material according to the present invention, since the modified portion is formed by non-contact processing with laser light, the durability of the blade in dicing with a diamond cutter as in the conventional technique , There is no problem such as replacement frequency. Further, in the method for cutting a light-transmitting material according to the present invention, since the formation of the modified portion is realized by non-contact processing with a laser beam as described above, the light-transmitting material is not completely cut. It is possible to cut the light-transmitting material along a cutting pattern that cuts out the transparent material.

【0082】

Further, a plurality of circuit portions are formed in the light transmissive material, and in the process of forming the modified portion, a condensing point is formed inside the light transmissive material portion facing the gap formed between the adjacent circuit portions. It is preferable that the laser beam is focused so that the modified portion is formed. With such a configuration, the light transmissive material can be reliably cut at the position of the gap formed between the adjacent circuit portions.

【0083】

Further, in the step of forming the modified portion, when irradiating the light transmitting material with the laser beam, it is preferable to collect the laser beam at an angle at which the circuit portion is not irradiated with the laser beam. In this way, when the light-transmitting material is irradiated with the laser beam in the reforming portion forming step, the laser beam is incident on the circuit portion by condensing the laser beam at an angle at which the circuit portion is not irradiated with the laser beam. This can be prevented and the circuit unit can be protected from the laser beam.

【0084】

Further, in the reforming portion forming step, it is preferable to continuously form the reforming portion along the moving direction of the condensing point by moving the condensing point in the direction intersecting the optical axis of the laser beam. In this way, in the reforming portion forming step, by moving the condensing point in the direction intersecting the optical axis of the laser beam, the reforming portion is continuously formed along the moving direction of the condensing point. , The cutting direction stability is further improved, and the cutting direction control can be performed more easily.

【0085】

In the method for cutting a light-transmitting material according to the present invention, the laser light emitted from a laser light source is collected so that the focusing point is located inside the light-transmitting material, and the light is collected inside the light-transmitting material. It is characterized by including a crack forming step of forming a crack only in the light spot and its vicinity, and a cutting step of cutting a light transmissive material at the position of the formed crack.

【0086】

In the method for cutting a light-transmitting material according to the present invention, in the crack forming step, the laser light is focused so that the focusing point of the laser light is located inside the light-transmitting material, so that the laser at the focusing point is located. The energy density of light exceeds the threshold of optical damage or optical insulation failure of the light-transmitting material, and cracks are formed only at the condensing point inside the light-transmitting material and its vicinity. In the cutting process, the light-transmitting material is cut at the position of the cracks formed, the amount of dust generated is extremely low, and the possibility of dicing scratches, chipping, cracks on the material surface, etc. is extremely low. Become. Further, since the light-transmitting material is cut along the crack formed by the optical damage or the optical dielectric breakdown of the light-transmitting material, the cutting direction stability is improved and the cutting direction can be easily controlled. It can be carried out. In addition, the dicing width can be reduced as compared with dicing with a diamond cutter, and the number of light-transmitting materials cut from one light-transmitting material can be increased. As a result, according to the present invention, the light-transmitting material can be cut extremely easily and appropriately.

【0087】

Further, in the method for cutting a light-transmitting material according to the present invention, since there is almost no dust-generated powder, lubricating cleaning water for preventing scattering of the dust-generated powder becomes unnecessary, and a dry process can be performed in the cutting process. It can be realized.

【0088】

Further, in the method for cutting a light-transmitting material according to the present invention, since crack formation is realized by non-contact processing with laser light, the durability and replacement of the blade in dicing with a diamond cutter as in the conventional technique. There are no problems such as frequency. Further, in the method for cutting a light-transmitting material according to the present invention, since crack formation is realized by non-contact processing with a laser beam as described above, the light-transmitting material is not completely cut, and the light-transmitting material is not completely cut. It is possible to cut a light-transmitting material along a cutting pattern that cuts out the material.

【0089】

Further, in the cutting step, it is preferable to cut the light-transmitting material by growing the formed cracks. As described above, in the cutting step, the light-transmitting material is cut by growing the formed cracks, so that the light-transmitting material can be surely cut at the position of the formed cracks.

【0090】

Further, in the cutting step, it is preferable to use a pressing member to apply stress to the light-transmitting material to grow cracks and cut the light-transmitting material. In this way, in the cutting step, by applying stress to the light-transmitting material using the pressing member, cracks are grown and the light-transmitting material is cut, so that the light-transmitting material is further formed at the position of the crack. It can be cut more reliably.

【0091】

The device for cutting a light-transmitting material according to the present invention has a laser light source, a holding means for holding the light-transmitting material, and a condensing point of the laser light emitted from the laser light source inside the light-transmitting material. An optical element that condenses light so that it is located, a cutting means that cuts the light transmissive material at the position of a modified portion formed only at the condensing point of laser light inside the light transmissive material and its vicinity, and It is characterized by having.

【0092】

In the light-transmitting material cutting apparatus according to the present invention, the laser beam is focused by the optical element so that the focusing point of the laser light is located inside the light-transmitting material, so that the light-transmitting material is collected. The modified portion is formed only at the condensing point inside and its vicinity. Then, since the cutting means cuts the light-transmitting material at the position of the modification portion formed only at the condensing point of the laser light and the vicinity thereof inside the light-transmitting material, the light-transmitting material is formed. It is surely cut along the modified portion, the amount of dust generated is extremely low, and the possibility of dicing scratches, chipping, cracks on the material surface, etc. is extremely low. Further, since the light-transmitting material is cut along the modified portion, the cutting direction stability is improved and the cutting direction can be easily controlled. In addition, the dicing width can be reduced as compared with dicing with a diamond cutter, and the number of light-transmitting materials cut from one light-transmitting material can be increased. As a result, according to the present invention, the light-transmitting material can be cut extremely easily and appropriately.

【0093】

Further, in the cutting device for the light-transmitting material according to the present invention, since there is almost no dust-generated powder, lubricating cleaning water for preventing the dust-generated powder from scattering becomes unnecessary, and a dry process can be performed in the cutting process. It can be realized.

【0094】

Further, in the light-transmitting material cutting apparatus according to the present invention, since the modified portion is formed by non-contact processing with laser light, the durability and replacement of the blade in dicing with a diamond cutter as in the conventional technique. There are no problems such as frequency. Further, in the light-transmitting material cutting apparatus according to the present invention, since the modified portion is formed by non-contact processing with laser light as described above, the light-transparent material is not completely cut, and the light-transmitting material is not completely cut. It is possible to cut a light-transmitting material along a cutting pattern that cuts out the material.

【0095】

The device for cutting a light-transmitting material according to the present invention has a laser light source, a holding means for holding the light-transmitting material, and a condensing point of the laser light emitted from the laser light source inside the light-transmitting material. It is provided with an optical element that condenses light so as to be located, and a cutting means that cuts the light transmissive material by growing cracks formed only at the condensing point of laser light inside the light transmissive material and its vicinity. It is characterized by that.

【0096】

In the light-transmitting material cutting apparatus according to the present invention, the laser light is focused by the optical element so that the light-transmitting point of the laser light is located inside the light-transmitting material, so that the laser at the light-transmitting point is focused. The energy density of light exceeds the threshold of optical damage or optical insulation failure of the light-transmitting material, and cracks are formed only at the condensing point inside the light-transmitting material and its vicinity. Then, since the cutting means cuts the light-transmitting material by growing cracks formed only in the condensing point of the laser light and its vicinity inside the light-transmitting material, the light-transmitting material is light-transmitting. It will be surely cut along the cracks formed by the optical damage of the material or the optical insulation destruction, the amount of dust generated is extremely low, and there is a possibility that dicing scratches, chipping or cracks on the material surface may occur. Is also extremely low. Further, since the light-transmitting material is cut along the cracks, the cutting direction stability is improved, and the cutting direction can be easily controlled. In addition, the dicing width can be reduced as compared with dicing with a diamond cutter, and the number of light-transmitting materials cut from one light-transmitting material can be increased. As a result, according to the present invention, the light-transmitting material can be cut extremely easily and appropriately.

【0097】

Further, in the cutting device for the light-transmitting material according to the present invention, since there is almost no dust-generated powder, lubricating cleaning water for preventing the dust-generated powder from scattering becomes unnecessary, and a dry process can be performed in the cutting process. It can be realized.

【0098】

Further, in the light-transmitting material cutting apparatus according to the present invention, since cracks are formed by non-contact processing with laser light, the durability of the blade in dicing with a diamond cutter, the frequency of replacement, etc., as in the conventional technique, etc. The problem does not occur. Further, in the light transmitting material cutting apparatus according to the present invention, since cracks are formed by non-contact processing with laser light as described above, a light transmitting material that does not completely cut the light transmitting material is used. It is possible to cut a light-transmitting material along a cutting pattern that cuts out.

【0099】

Further, the cutting means preferably has a pressing member for applying stress to the light transmissive material. As described above, since the cutting means has a pressing member for applying stress to the light-transmitting material, the pressing member makes it possible to apply stress to the light-transmitting material to grow cracks, and the cracks are formed. The light transmitting material can be cut more reliably at the position of the crack.

【0100】

Further, the light transmissive material is a light transmissive material having a plurality of circuit portions formed on its surface, and the optical element is a light transmissive material portion facing a gap formed between adjacent circuit portions. It is preferable to collect the laser light so that the focusing point is located inside. With this configuration, the light transmissive material can be reliably cut at the position of the gap formed between the adjacent circuit portions.

【0101】

Further, the optical element preferably collects the laser beam at an angle at which the circuit portion is not irradiated with the laser beam. In this way, by condensing the laser beam at an angle at which the optical element does not irradiate the circuit section with the laser beam, it is possible to prevent the laser beam from entering the circuit section and protect the circuit section from the laser beam. Can be done.

【0102】

Further, it is preferable to further provide a focusing point moving means for moving the focusing point in a direction intersecting the optical axis of the laser beam. As described above, by further providing the condensing point moving means for moving the condensing point in the direction intersecting the optical axis of the laser beam, cracks are continuously formed along the moving direction of the condensing point. The cutting direction stability is further improved, and the cutting direction control can be performed more easily.

【0103】

[Effect of the invention]

According to 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) produced by cutting an object to be processed.

【0104】

Further, since the position of the condensing point of the laser light in the thickness direction of the processing object is determined based on the thickness and the refractive index of the processing object, the formation position of the modified region inside the processing object can be easily performed. Can be asked for.

[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 schematic block diagram of the laser processing apparatus which can be used for the laser processing method which concerns on 1st Example of this Embodiment.

[Fig. 15]

It is a flowchart for demonstrating the laser processing method which concerns on 1st Example of this Embodiment.

[Fig. 16]

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. 17]

It is a schematic diagram explaining the laser processing method which concerns on 1st example of this Embodiment regarding a plurality of laser light sources.

[Fig. 18]

It is a schematic diagram explaining another laser processing method which concerns on 1st Example of this Embodiment regarding a plurality of laser light sources.

[Fig. 19]

In the second example of this embodiment, it is the schematic plan view which shows the piezoelectric element wafer in the state of being held by the wafer sheet.

[Fig. 20]

In the second example of this embodiment, it is the schematic sectional drawing which shows the piezoelectric element wafer in the state of being held by the wafer sheet.

[Fig. 21]

It is a flowchart for demonstrating the cutting method which concerns on 2nd Example of this Embodiment.

[Fig. 22]

It is sectional drawing of the light transmissive material which is irradiated with a laser beam by the cutting method which concerns on 2nd Example of this Embodiment.

[Fig. 23]

It is a top view of the light transmissive material irradiated with the laser beam by the cutting method which concerns on 2nd Example of this Embodiment.

[Fig. 24]

It is sectional drawing along the line XXIV-XXIV of the light transmissive material shown in FIG.

[Fig. 25]

FIG. 3 is a cross-sectional view taken along the line XXV-XXV of the light transmissive material shown in FIG. 23.

[Fig. 26]

It is sectional drawing along the XXV-XXV line of the light transmissive material shown in FIG. 23 when the moving speed of a condensing point is slowed down.

[Fig. 27]

It is sectional drawing along the XXV-XXV line of the light transmissive material shown in FIG. 23 when the moving speed of a condensing point is further slowed down.

[Fig. 28]

It is sectional drawing of the piezoelectric element wafer or the like which shows the 1st step of the cutting method which concerns on 2nd Example of this Embodiment.

[Fig. 29]

It is sectional drawing of the piezoelectric element wafer or the like which shows the 2nd step of the cutting method which concerns on 2nd Example of this Embodiment.

[Fig. 30]

It is sectional drawing of the piezoelectric element wafer or the like which shows the 3rd process of the cutting method which concerns on 2nd Example of this Embodiment.

[Fig. 31]

It is sectional drawing of the piezoelectric element wafer or the like which shows the 4th process of the cutting method which concerns on 2nd Example of this Embodiment.

[Fig. 32]

It is sectional drawing of the piezoelectric element wafer or the like which shows the 5th step of the cutting method which concerns on the 2nd example of this embodiment.

[Explanation of symbols]

1 ... Processed object, 3 ... Surface, 5 ... Scheduled cutting line, 7 ... Modified area, 9 ... Crack area, 11 ... Silicon wafer, 13 ... Melting process Region, 15,17,19,23 ... Laser light source, 25,27,29 ... Array light source, 31 ... Piezoelectric element wafer, 37 ... Piezoelectric device chip, 100 ... Laser processing equipment , 101 Laser light source, 105 Focusing lens, 109 X-axis stage, 111 Y-axis stage, 113 Z-axis stage, P Focusing point