Nitride group compound semiconductor element and light-emitting semiconductor element and manufacture thereof

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a semiconductor element that can be used for a light emitting element capable of emitting light from ultraviolet light to a red color, a light receiving element having a high electromotive force, and a method for manufacturing the same, and particularly a semiconductor obtained by separating a nitride compound semiconductor wafer into a chip. The present invention relates to an element and a method for manufacturing the element.

【0002】

[Conventional technology]

Today, semiconductor devices using nitride-based compound semiconductors having a high energy bandgap are being developed. Examples of devices using semiconductor elements having a high energy bandgap include light emitting diodes capable of emitting blue light and semiconductor lasers capable of emitting blue purple light. The device has a configuration in which a semiconductor chip is placed on a stem or the like and can be energized.

【0003】

Unlike semiconductor devices such as GaAs, GaP, and InGaAlAs, it is difficult to form a single crystal in a semiconductor device using a nitride compound semiconductor. In order to obtain a single crystal film of a nitride compound semiconductor having good crystallinity, it is formed on a sapphire substrate via a buffer layer by using a MOCVD method or an HDVPE method.

【0004】

Usually, a semiconductor wafer on which semiconductor materials such as GaAs, GaP and InGaAlAs are laminated is cut out into a chip and used as a semiconductor light emitting element or the like. As a method of cutting into chips from a semiconductor wafer, a dicer or a scriber is used. A dicer is a device that fully cuts a wafer by the rotational movement of a disk having a diamond cutting edge, or cuts a groove having a width wider than the cutting edge width (half cut) and then cuts by an external force. On the other hand, a scriber is a device that draws an extremely thin line (scribe line) on a wafer with a needle having a diamond tip, for example, in a grid pattern, and then cuts the wafer by an external force. Crystals with a zinc-like structure such as GaP and GaAs have cleavage in the "110" direction. Therefore, it is possible to relatively easily separate semiconductor wafers such as GaAs, GaAlAs, and GaP into desired shapes by utilizing this property.

【0005】

However, the nitride-based compound semiconductor has a hetero-epi structure laminated on a sapphire substrate or the like, and the nitride-based compound semiconductor and the sapphire substrate have a large lattice constant irregularity. The sapphire substrate does not have cleavage due to its hexagonal nature. Furthermore, both sapphire and nitride compound semiconductors are extremely hard substances with a Mohs hardness of approximately 9. Therefore, it was difficult to cut with a scriber. In addition, when a full cut was made with a dicer, cracks and chipping were likely to occur on the cut surface, and it was not possible to cut cleanly. In some cases, the formed semiconductor layer was peeled off from the sapphire.

【0006】

If the semiconductor wafer can be accurately separated into chips without damaging the crystallinity of the nitride compound semiconductor, the electrical characteristics and efficiency of the semiconductor element can be improved. Moreover, since many semiconductor chips can be obtained from one wafer, productivity can be improved.

【0007】

Therefore, the nitride compound semiconductor wafer is separated into desired chips by combining a scriber and a dicer. A method for separating each chip is described in JP-A-8-274371 and the like. Specifically, for a semiconductor wafer made of a gallium nitride-based compound semiconductor, a groove is formed on the lower surface of the sapphire substrate by a dicer so that the distance between the lower surface and the upper surface of the sapphire substrate is approximately 100 μm. Next, the scriber forms a scribe line on the bottom surface of the groove. Subsequently, it is disclosed that a desired semiconductor light emitting device is formed by cutting a semiconductor wafer by applying a load by a roller along a scribe line. By such a method for manufacturing a semiconductor element, a semiconductor chip can be cut from a semiconductor wafer to a desired size.

【0008】

[Problems to be Solved by the Invention]

However, in today's world where it is desired to accurately form smaller chips with good mass productivity, the above-mentioned cutting method is not sufficient, and a better chip separation method is required. Further, when it is used as a semiconductor light emitting element, higher contrast is required. Therefore, the present invention prevents the occurrence of cracks and chipping on the cut surface when the nitride compound semiconductor wafer is separated into chips. Another object of the present invention is to provide a semiconductor device separated into a desired shape and size with a good yield without impairing the crystallinity of the nitride compound semiconductor, and a method for manufacturing the same.

【0009】

[Means for solving problems]

The manufacturing method of the present invention relates to a method of separating each semiconductor element from a nitride compound semiconductor wafer. In particular, prior to the separation of the semiconductor element, a step of forming a first groove by irradiating the semiconductor wafer with a laser, and driving a scriber and / or a dicer with a cutting edge aligned along the first groove are used to drive a nitride compound. Manufactures semiconductor devices.

【0010】

It is also a method for manufacturing a nitride compound semiconductor device in which a nitride compound semiconductor is formed on a sapphire substrate.

【0011】

The semiconductor device of the present invention is a light emitting device having a nitride compound semiconductor layer on a sapphire substrate. A cloudy portion is provided at the outer peripheral edge of the safaa substrate constituting this semiconductor light emitting device or at the outer peripheral edge of the nitride compound layer.

【0012】

[Action]

According to the present invention, by using laser light to form the first groove, it is possible to accurately form a groove in a nitride semiconductor device or a smaller chip. Further, the semiconductor chip can be formed in a short time and precisely by performing a scriber and / or a dicer using the first groove as a guide. Further, a sapphire substrate having extremely high hardness and a nitride compound semiconductor can also be manufactured with good mass productivity. Further, when the groove is formed by the laser, a cloudy portion is formed at the outer peripheral end, although the cause is not clear. It is considered that this cloudy portion can improve the contrast ratio when a light emitting element is formed to scatter external light.

【0013】

BEST MODE FOR CARRYING OUT THE INVENTION

As a result of various experiments, the present inventors formed a groove that guides the cutting edge of the scribing and / or dicing prior to scribing and / or dicing in the separation step when separating the semiconductor element from the nitride compound semiconductor wafer. The present invention has been made by finding that it is possible to separate into a chip shape and the like with good accuracy, yield and mass productivity by functionally separating the step of performing the process and the scriber and / or dicing process of forming a substantial separation groove.

【0014】

That is, it is necessary to apply a certain amount of weight in order to separate the semiconductor chips with good mass productivity by a scriber or the like. When a load is applied to the cutting edge of the scriber, the Mohs hardness of the nitride compound semiconductor element or sapphire is as hard as about 9, so that a distorted groove 202 may be formed with respect to the desired groove 201 as shown in FIG. Such distortion of the groove not only makes it impossible to separate into chips with high accuracy, but also causes a decrease in yield. It also causes damage to the scriber's cutting edge. Further, the wafer may be cracked or chipped. On the other hand, if the load is weakened, it takes an extremely long time to separate into a desired chip shape or the like, resulting in poor mass productivity.

【0015】

The present inventor has easily formed a groove shape that matches the cutting edge of a scriber by efficiently forming a groove for a scriber or the like on a very hard nitride compound semiconductor or sapphire using a laser. Therefore, the blade can be moved as desired even if the load at the time of scribe is increased. As a result, the separation time can be shortened and the chip shape can be accurately separated as desired. In addition, the cutting depth for scribing can be made shallow. Therefore, the stress ratio applied to the semiconductor wafer can be significantly reduced. Further, the end face irradiated with the laser becomes cloudy. Therefore, when the light emitting element is formed, there is an advantage that the reflection of external light is suppressed and the contrast is improved. Hereinafter, the present invention will be described in detail.

【0016】

FIG. 1 shows a separation example of the nitride compound semiconductor of the present invention. In FIG. 1, a semiconductor wafer 1 on which a nitride compound semiconductor 101 is formed in advance is prepared. In this semiconductor wafer, a buffer layer in which GaN is formed at a low temperature is formed on a sapphire substrate 102. A 2-inch diameter semiconductor wafer 1 in which GaN is formed as an N-type contact layer, non-doped InGaN as an active layer, AlGaN as a P-type clad layer, and GaN as a P-type contact layer. The semiconductors are partially etched as shown in the non-showing figure to expose the P-type and N-type semiconductors, respectively. Electrodes are formed on the exposed semiconductor surface so as to function as a light emitting element after separation. In addition, the semiconductor joint is etched along the groove irradiated by the laser (Fig. 1 (a)).

【0017】

Such a semiconductor wafer is fixedly arranged on the XY stage. While irradiating the excimer laser, the semiconductor wafer was moved in the X-axis and Y-axis directions, respectively, to form the first groove 103 in the vertical and horizontal directions. The first groove 103 formed was formed from the semiconductor surface side to a part of the sapphire substrate, and had an inverted triangular shape with an opening having a width of about 40 μm (FIG. 1 (b)).

【0018】

A dicing blade was applied to the first groove formed by laser irradiation, and the dicing blade was run along the first groove to form the second groove 104 (FIG. 1 (c)).

【0019】

After that, each semiconductor chip 105 was separated by applying pressure from the sapphire substrate side along the second groove 104 with a roller and cracking it (FIG. 1 (d)). As a result, it is possible to form a semiconductor element having the same outer shape of each semiconductor chip. Hereinafter, the configuration of the present invention will be described in detail.

【0020】

(Laser) As the laser used in the present invention, various lasers can be used as long as grooves and through holes can be formed in the sapphire substrate and the nitride compound semiconductor. Specifically, various lasers such as an excimer laser and a YAG laser can be preferably used. In particular, the excimer laser can form fine grooves in both the nitride compound semiconductor and the sapphire substrate. It is preferable that the length in the depth direction in laser machining is not too large from the viewpoint that it takes more time to form a deep groove by the laser than a scriber or a dicer and that it is partially destroyed by heating for a long time. Further, the depth and width of the first groove formed by the laser can be variously adjusted by changing the energy density, irradiation time and focus of the laser to other stages.

【0021】

When laser irradiation is performed from the surface side of the nitride compound semiconductor, the semiconductor joint end face may be short-circuited by the laser irradiation, so that the semiconductor joint end face can be etched in advance. Further, the laser irradiation may irradiate only one surface of the semiconductor wafer, or may irradiate both sides.

【0022】

(Nitride-based compound semiconductor) Examples of the nitride-based compound semiconductor used in the present invention include BN, GaN, AlN, InN, GaAlN, InGaN, and InGaAlN. Such a nitride compound semiconductor can be formed into a film by using a MOCVD method or the like. Nitride-based compound semiconductors can be formed on silicon carbide, zinc oxide, gallium nitride single crystals, spinels, and sapphire substrates. In order to form a single crystal having good crystallinity, it is preferable to use sapphire as a substrate. By forming such a nitride compound semiconductor with a MIS junction, a PN junction, or a PIN junction, it can be used as a semiconductor element. Various semiconductor structures such as homozygotes, heterozygotes, and double heterozygotes can be selected. It is also possible to have a single quantum well structure or a multiple quantum well structure in which the semiconductor layer is a thin film that causes a quantum effect. A semiconductor element can be formed by separating the semiconductor wafers thus formed.

【0023】

Nitride-based compound semiconductor devices include light-emitting diodes capable of emitting light from ultraviolet to red because of their relatively large bandgap, light-emitting devices such as short-wavelength laser diodes that can be used for DVDs, optical sensors, and relatively high electromotive force. It can be used as a light receiving element of a solar cell or the like having the above.

【0024】

(First Groove 103) The first groove 103 preferably has a depth and width for use as a guide groove for guiding the blade during scribe and / or dicing. Chipping or the like does not occur in the first groove 103 itself formed by the laser. However, if the wafer 1 is formed too deeply, the wafer 1 is unexpectedly cut into chips in the subsequent separation step, and chipping and cracks tend to occur easily. Further, when irradiating the semiconductor element side with a laser, it is preferable not to cut the semiconductor junction. This is because when the laser beam reaches the semiconductor junction surface, a short circuit may occur. Therefore, it is desirable to remove the semiconductor junction surface by etching in advance or not to irradiate the semiconductor junction surface with a laser.

【0025】

(Second groove 104) The second groove 104 formed along the first groove 103 is used to separate the wafer 1 into each semiconductor chip by applying a load. Therefore, the formation of the second groove 104 is preferably 10% or less of the total thickness. If the thickness is made larger than this, the wafer is cut into chips during groove formation, and chipping and cracks tend to occur easily. Further, after forming the second groove 104 with a scriber or a dicer, a scribe line may be formed again with a scriber or the like for the purpose of more accurately separating into chips. The scriber after the formation of the second groove 104 can be used again to separate the scriber into chips. Further, the wafer separation after the formation of the second groove 104 can be separated by applying a load to a roller or the like along the second groove 104 so that an external force is applied along the groove. Hereinafter, specific examples of the present invention will be described in detail based on Examples, but it goes without saying that the present invention is not limited to these Examples.

【0026】

[Example]

(Example 1) On a sapphire substrate having a thickness of 450 μm and a size of 2 inches Φ, GaN as an n-type contact layer, a non-doped InGaN with a thickness of about 3 nm that produces a quantum effect as an active layer, and AlGaN as a p-type clad layer. , A nitride compound semiconductor wafer in which GaN was sequentially laminated as a p-type contact layer was formed. The thickness of the formed semiconductor layer is about 5 μm. After forming the semiconductor layer, the semiconductor layer was etched to expose the semiconductor surface so that each PN electrode could be formed, and the electrode was formed. (It should be noted that a GaN layer is formed as a buffer layer on the sapphire substrate. The P-type layer is annealed at 400 ° C after film formation because it is difficult to form a P-type just by doping with impurities. ) The sapphire substrate side of the semiconductor wafer formed for easy separation was polished to a thickness of 80 μm by a polishing machine. The semiconductor wafer thus formed was sequentially cut in the following steps.

【0027】

Adhesive tape is attached to the polished sapphire substrate and fixed with a vacuum chuck. The table can be moved on the X-axis (left and right) and Y-axis (front and back), and has a rotatable structure. After fixing, the maximum energy density is 20 J / cm from the sapphire substrate side of the semiconductor wafer.²The excimer laser was irradiated at. By moving the XY stage while irradiating the laser, a groove was formed in which one chip became 300 μm square. The end face irradiated with the laser became an inverted cone with an angle of about 10 °, and a groove with a width of about 10 μm was formed.

【0028】

The laser-irradiated semiconductor wafer is attached to the scriber table and fixed with a vacuum chuck. The table moves on the x-axis (left and right) and y-axis (front and back), and has a structure that can rotate 180 degrees horizontally. After fixing, the bar provided with the diamond blade of the scriber has a structure that can move in the z-axis (up and down) and y-axis (front and back) directions. Under the conditions of a cutting speed of 13 mm / sec and a load of 110 g on the cutting edge of the diamond blade, align the scriber blade along the first groove formed by laser irradiation and draw a scribe line on the specified cut line (300 μm square). It was. By moving the scriber again under the same conditions, a nitride compound semiconductor device of 300 μm square was obtained.

【0029】

The nitride compound semiconductor separated to a desired size by a scriber was peeled off from the table to obtain each semiconductor light emitting device. The yield was 97% or more when the gallium nitride based semiconductor light emitting chips thus obtained were removed from those due to external defects. The end faces of the obtained semiconductor chips were almost uniform.

【0030】

(Example 2) The semiconductor light emitting elements were separated under the same conditions except that the first and second grooves were formed from the sapphire substrate instead of the semiconductor element side. The nitride compound semiconductor side is etched to form the electrode 306, and the groove of the present invention is formed on the sapphire substrate 304 side so as to coincide with the etching groove 307. The active layer 305 is separated by etching. The light emitting chip thus formed also had a clean surface with no chipping on the end faces 302 and 303 as in the first embodiment, and the yield was high.

【0031】

Further, the outer periphery of the sapphire end of the formed semiconductor light emitting element has a cloudy portion 301 as shown in FIG. 2, and the light emitting element having a high contrast ratio can be obtained.

【0032】

(Comparative Example 1) The step of forming the first groove portion by using an excimer laser was omitted, and the nitride compound semiconductor epitaxial wafer was cut by using a scriber in the same manner as in Example 1. Some of the formed semiconductor chips were partially different in size due to the displacement of the cutting edge during scribe. In addition, some of the cutting lines had cracks. The yield excluding these semiconductor chips was 75% or less.

【0033】

[Effect of the invention]

As described above, according to the production method of the present invention, the nitride compound semiconductor wafer can be separated with good yield and mass productivity without causing cracks, chipping and the like.

【0034】

Further, according to the present invention, since the traveling groove of the scriber and / or the dicer can be formed in advance by laser irradiation, even a smaller semiconductor chip can be cut with a desired yield. Further, there is an advantage that the cutting time in the scriber and / or the dicer is very short and the damage to the cutting edge is small. Further, in the formed semiconductor element, a cloudy portion is formed at the outer peripheral edge irradiated with the laser, and the semiconductor element can be used as a light emitting element having high contrast.

[Simple explanation of drawings]

[Figure 1]

FIG. 1 is a schematic view showing a method for producing a nitride compound semiconductor of the present invention. FIG. 1 (a) shows a schematic cross-sectional view of a semiconductor wafer, and FIG. 1 (b) is a schematic cross-sectional view of a semiconductor wafer in which a first groove is formed by a laser. Further, FIG. 1 (c) is a schematic cross-sectional view of a semiconductor wafer in which a second groove is formed by a dicer. FIG. 1 (d) is a schematic cross-sectional view in which individual semiconductor elements are separated by an external force.

[Figure 2]

FIG. 2 is a partial plan view of the separation groove by the scriber shown for comparison with the present invention.

[Fig. 3]

FIG. 3 is a schematic cross-sectional view of the semiconductor light emitting device of the present invention.

[Explanation of symbols]

1 ... Semiconductor wafer 101 ... Nitride-based compound semiconductor with semiconductor junction formed 102 Sapphire substrate 103 ... First groove formed by laser 104 ... Second groove formed by the dicer 105 Separated semiconductor elements 2 ... Semiconductor wafer 201 ... Desired groove formed by scriber 202 ... Undesired distorted groove formed by scriber 301 Cloudy part 302 ... End face formed by laser 303 End face formed by scribe 304 Sapphire substrate 305 Active layer to be a semiconductor junction surface 306 Electrode of light emitting element 307 End face formed by etching