JPH10321908A - Nitride group compound semiconductor element and light-emitting semiconductor element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To utilize a groove formed accurately in a small chip and form chips for a short time and precisely, by a method wherein a first groove is formed by laser irradiation and a scriber or a dicer aligned to an edge along the groove is driven. SOLUTION: A semiconductor wafer 1 is fixed on an XY stage and moved while excimer lasers are radiated, whereby first grooves 103 are formed vertically and laterally. Next, an edge of dicing is abutted on the first groove 103 and an edge of dicing is run along the first groove 103, whereby a second groove 104 is formed. Thereafter, pressure is applied by a roller from a sapphire substrate side to split it and separate it into each semiconductor chip 105. As a result, a contour of each semiconductor chip 105 can be formed equally.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device which can be used as a light emitting device capable of emitting light from ultraviolet light to red light, a light receiving device having a high electromotive force, and a method of manufacturing the same. And a method of manufacturing the same.

[0002]

2. Description of the Related Art At present, a semiconductor device using a nitride compound semiconductor having a high energy band gap is being developed. Examples of a device using a semiconductor element having a high energy band gap include a light emitting diode capable of emitting blue light and a semiconductor laser capable of emitting blue violet light. The device has a configuration in which a semiconductor chip is arranged on a stem or the like and can be energized.

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

Usually, GaAs, GaP or InGaAlA
A semiconductor wafer on which a semiconductor material such as s is stacked is cut into chips and used as a semiconductor light emitting device or the like. As a method of cutting out a semiconductor wafer into chips, a dicer or a scriber is used. The dicer is a device that cuts a wafer by an external force after a wafer is fully cut by a rotating motion of a disk having a blade as a diamond, or after a groove having a width wider than the blade is cut (half cut). On the other hand, a scriber is a device that similarly draws a very thin line (scribe line) on a wafer in a checkerboard shape with a needle having a diamond tip, and then cuts the wafer with an external force. Crystals having a zinc zinc structure, such as GaP and GaAs, have cleavage in the "110" direction. Therefore, GaAs, GaAs
Semiconductor wafers such as GaAs and GaP can be relatively easily separated into desired shapes.

[0005] However, the nitride-based compound semiconductor has a heteroepitaxial structure laminated on a sapphire substrate or the like, and the nitride-based compound semiconductor and the sapphire substrate have large lattice constant irregularities. The sapphire substrate has no cleavage property due to its hexagonal nature. Further, both sapphire and nitride-based compound semiconductors are very hard substances having Mohs hardness of about 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 cutting could not be performed neatly. In some cases, the formed semiconductor layer was separated from sapphire.

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

For this reason, a 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. Specifically, a groove is formed on the lower surface of the sapphire substrate by a dicer on a semiconductor wafer made of a gallium nitride-based compound semiconductor such that the distance between the bottom surface and the upper surface of the sapphire substrate is approximately 100 μm. Next, a scribe line is formed on the bottom surface of the groove by a scriber. Subsequently, it is disclosed that a desired semiconductor light emitting element is formed by applying a weight by a roller along a scribe line and cutting the semiconductor wafer. By such a method of manufacturing a semiconductor element, a semiconductor chip can be cut into a desired size from a semiconductor wafer.

[0008]

However, today, when it is desired to form smaller chips accurately and with good mass productivity, the above cutting method is not sufficient, and a more excellent chip separation method is required. . Further, when 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 separating the nitride-based compound semiconductor wafer into chips. Another object of the present invention is to provide a semiconductor device separated into a desired shape and size at a high yield without impairing the crystallinity of the nitride-based compound semiconductor, and a method for manufacturing the same.

[0009]

The manufacturing method of the present invention relates to a method for separating a semiconductor device from a nitride-based compound semiconductor wafer for each semiconductor element. In particular, a step of forming a first groove by irradiating a semiconductor wafer with a laser prior to separation of a semiconductor element, and driving a scriber and / or a dicer having a cutting edge along the first groove to form a nitride-based compound. Manufacture semiconductor devices.

The present invention is also a method for manufacturing a nitride-based compound semiconductor device in which a nitride-based compound semiconductor is formed on a sapphire substrate.

The semiconductor device of the present invention is a light emitting device having a nitride compound semiconductor layer on a sapphire substrate. The sapphire substrate constituting the semiconductor light emitting device has a cloudy portion at the outer edge or the outer edge of the nitride-based compound layer.

[0012]

According to the present invention, a laser beam is used to form the first groove, so that the groove can be accurately formed even in a nitride semiconductor device or a smaller chip. In addition, by performing scriber and / or dicer using the first groove as a guide, a semiconductor chip can be formed accurately in a short time. In addition, even a sapphire substrate or a nitride-based compound semiconductor having extremely high hardness can be manufactured with high productivity. Furthermore, although the cause is not clear when the groove is formed by the laser, a cloudy portion is formed at the outer peripheral end. It is considered that the 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
In the case of separating a semiconductor element from a nitride-based compound semiconductor wafer, a step of forming a groove for guiding a scribe and / or a dicer blade prior to the scribe and / or dicing in the separation step, and forming a substantial separation groove The present inventors have found that the functions can be separated into a chip shape and the like with high accuracy, yield, and mass productivity by separating functions into a scriber and / or a dicer process to be performed.

That is, it is necessary to apply a certain amount of weight in order to separate the semiconductor chips with high productivity by a scriber or the like. When a load is applied to the blade edge of the scriber, the nitride-based compound semiconductor element or sapphire has a very high Mohs hardness of about 9, which is so hard that a desired groove 201 may be formed into a distorted groove 202 as shown in FIG. Such groove distortion not only cannot be separated into chips with high accuracy, but also causes a reduction in yield. In addition, it may cause damage to the blade of the scriber. Further, cracking and chipping of the wafer may occur. On the other hand, if the weight is reduced, it takes an extremely long time to separate the chip into a desired chip shape or the like, and mass productivity is deteriorated.

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

FIG. 1 shows an example of separation of a nitride-based compound semiconductor of the present invention. FIG. 1 shows a nitride-based compound semiconductor 101 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. The semiconductor wafer 1 has a diameter of 2 inches in which GaN is sequentially formed as an N-type contact layer, non-doped InGaN is formed as an active layer, AlGaN is formed as a P-type cladding layer, and GaN is formed as a P-type contact layer. The semiconductor is partially etched (not shown) to expose the P-type and N-type semiconductors. An electrode is formed on the exposed surface of the semiconductor, and is formed so as to function as a light emitting element after separation. Also, the semiconductor junction is etched along the groove irradiated with the laser (FIG. 1A).

Such a semiconductor wafer is fixedly arranged on an XY stage. The semiconductor wafer was moved in the X-axis direction and the Y-axis direction while irradiating the excimer laser to form the first grooves 103 vertically and horizontally. The formed first groove 103 was formed from the semiconductor surface side to a part of the sapphire substrate, and had an inverted triangular shape having a width of about 40 μm (FIG. 1B).

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

Thereafter, the semiconductor chips 105 are separated from each other by applying pressure from the sapphire substrate side with a roller along the second groove 104 and pressing the same (FIG. 1).
(D)). As a result, a semiconductor element having the same outer shape of each semiconductor chip can be formed. Hereinafter, the configuration of the present invention will be described in detail.

(Laser) As the laser used in the present invention, various lasers can be used as long as grooves or through holes can be formed in a sapphire substrate or a nitride-based compound semiconductor. Specifically, various types such as an excimer laser and a YAG laser can be suitably used. In particular, an excimer laser can form a thin groove in any of a nitride-based compound semiconductor and a sapphire substrate. It is preferable that the length in the depth direction in the laser processing is not too large from the viewpoint that it takes a longer time to form a deep groove by laser as compared with a scriber or a dicer and partial destruction due to long-time heating. The depth and width of the first groove formed by the laser are determined by the energy density of the laser,
Various adjustments can be made by changing the irradiation time or the focus to another stage.

When laser irradiation is performed from the surface of the nitride-based compound semiconductor, short-circuiting may occur at the semiconductor junction end face due to the laser irradiation. Therefore, the semiconductor junction end face may be etched in advance. Further, the laser irradiation may irradiate only one surface of the semiconductor wafer,
Both surfaces may be irradiated.

(Nitride-based compound semiconductor) As the nitride-based compound semiconductor used in the present invention, BN, GaN, A
1N, InN, GaAlN, InGaN, InGaAl
N and the like. Such a nitride-based compound semiconductor can be formed by utilizing the MOCVD method or the like. The nitride-based compound semiconductor can be formed over silicon carbide, zinc oxide, gallium nitride single crystal, spinel, or a sapphire substrate. In order to form a single crystal with good crystallinity, sapphire is preferably used as a substrate. By forming an MIS junction, PN junction or PIN junction in such a nitride-based compound semiconductor, it can be used as a semiconductor element. The structure of the semiconductor can be variously selected such as a homo junction, a hetero junction, and a double hetero junction. In addition, a single quantum well structure or a multiple quantum well structure in which the semiconductor layer is thin enough to produce a quantum effect can be used. A semiconductor element can be formed by separating the semiconductor wafers thus formed, respectively.

Since the nitride-based compound semiconductor device has a relatively large band gap, a light-emitting diode such as a light-emitting diode capable of emitting light from ultraviolet to red, a short-wavelength laser diode usable for DVD and the like, an optical sensor, and a light-emitting device. It can be used as a light receiving element such as a solar cell having a high electromotive force.

(First Groove 103) The first groove 103 preferably has a depth and a width to be used as a guide groove for guiding a blade during scribing and / or dicing. Chipping or the like does not occur in the first groove 103 itself formed by the laser. However, if it is formed too deep, the wafer 1 is cut into chips in an undesired manner in the subsequent separation step, and chipping and cracking tend to occur. When the semiconductor element side is irradiated with a laser, it is preferable not to cut the semiconductor junction. This is because a short circuit may occur when the laser beam reaches the semiconductor bonding surface. Therefore, it is desirable to remove the semiconductor junction surface by etching in advance or not to irradiate the laser to the depth of the semiconductor junction surface.

(Second Groove 104) The second groove 104 formed along the first groove 103 is used to separate the wafer 1 into semiconductor chips by applying a load. Therefore, the formation of the second groove 104 has a thickness of 10
% Or less is preferable. If the thickness is larger than this, the wafer is cut into chips during the formation of the groove, and chipping and cracking tend to occur. Further, after the second groove 104 is formed by a scriber or a dicer, a scribe line may be formed again by a scriber or the like for the purpose of more accurately separating into chips. This second groove 1
The scriber after the formation of 04 can be used again to separate the chips into chips. Further, the wafer separation after the formation of the second groove 104 is performed such that an external force is applied along the groove.
It can also be separated by applying a weight to a roller or the like along 4. Hereinafter, specific examples of the present invention will be described in detail based on examples, but it is needless to say that the present invention is not limited to only these examples.

[0026]

【Example】

(Example 1) On a sapphire substrate having a thickness of 450 μm and a size of 2 inches φ, GaN is used as an n-type contact layer, non-doped InGaN having a thickness of about 3 nm which produces a quantum effect as an active layer, and AlGaN as a p-type cladding layer. , P
A nitride-based compound semiconductor wafer in which GaN was sequentially stacked as a mold contact layer was formed. The thickness of the formed semiconductor layer is about 5 μm. After the formation of the semiconductor layer, the semiconductor layer was etched to expose the semiconductor surface and form electrodes so that PN electrodes could be formed. (Note 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 layer only by doping impurities.) The sapphire substrate side of the semiconductor wafer formed to facilitate 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.

An adhesive tape is attached to the polished sapphire substrate and fixed with a vacuum chuck. The table can move in the X axis (left and right) and the Y axis (front and rear) and has a rotatable structure. After fixing, the semiconductor wafer was irradiated with an excimer laser at a maximum energy density of 20 J / cm ² from the sapphire substrate side. X while irradiating laser
By moving the Y stage, a groove having one chip of 300 μm square was formed. Laser irradiated end face is about 1
An inverted cone having an angle of 0 ° was formed, and a groove having a width of about 10 μm was formed.

The laser-irradiated semiconductor wafer is stuck on a scriber table and fixed with a vacuum chuck. The table moves along the x-axis (left and right) and the y-axis (back and forth).
It has a structure that can rotate 80 degrees horizontally. After fixation, the scriber bar provided with the diamond blade has a structure capable of moving in the z-axis (vertical) and y-axis (front-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, the scriber blade is aligned along the first groove formed by laser irradiation, and a scribe line is drawn on a predetermined cut line (300 μm square). Was. By moving the scriber again under the same conditions, a 300 μm square nitride-based compound semiconductor device was obtained.

The nitride-based compound semiconductor separated into a desired size by the scriber was peeled off from the table to obtain each semiconductor light emitting device. The gallium nitride-based semiconductor light-emitting chip obtained in this manner was free from defects due to outer shape defects, and the yield was 97% or more. The end face of the obtained semiconductor chip was almost uniform.

Example 2 A semiconductor light emitting device was separated under the same conditions except that the first and second grooves were formed not from the semiconductor device side but from the sapphire substrate. The etching for forming the electrode 306 is performed on the nitride-based compound semiconductor side, 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 layers 305 are separated from each other by etching. The light emitting chip thus formed also has an end face 30 similar to the first embodiment.
2,303 had a beautiful surface without chipping and the like, and the yield was high.

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

(Comparative Example 1) Cutting was performed in the same manner as in Example 1 except that the step of forming the first groove using an excimer laser was omitted, and the nitride-based compound semiconductor epitaxial wafer was cut using a scriber. Some of the formed semiconductor chips differ in size partially due to the shift of the cutting edge during scribing. In addition, there were cracks in the cutting line. The yield excluding such semiconductor chips was 75% or less.

[0033]

As described above, according to the manufacturing method of the present invention, a nitride-based compound semiconductor wafer can be separated with good yield and mass productivity without generating cracks and chipping.

Further, according to the present invention, since the running grooves 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 as desired. In addition, there is an advantage that the cutting time at the scriber and / or the dicer is very short, and damage to the cutting edge is reduced. Further, in the formed semiconductor element, a cloudy portion is formed at the outer peripheral end irradiated with the laser, so that the semiconductor element can be used as a light emitting element with high contrast.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating a method for manufacturing a nitride-based compound semiconductor according to the present invention. FIG. 1A is a schematic cross-sectional view of a semiconductor wafer, and FIG. 1B is a schematic cross-sectional view of a semiconductor wafer in which a first groove is formed by a laser. FIG. 1C is a schematic cross-sectional view of a semiconductor wafer in which a second groove is formed by a dicer. FIG.
(D) is a schematic cross-sectional view in which individual semiconductor elements are separated by an external force.

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

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor wafer 101 ... Nitride compound semiconductor with semiconductor junction formed 102 ... Sapphire substrate 103 ... First groove formed by laser 104 ... Dicing formed by dicer 2 grooves 105: separated semiconductor element 2: semiconductor wafer 201: desired groove formed by scriber 202: undesired distorted groove formed by scriber 301: cloudy Section 302: End face formed by laser 303: End face formed by scribing 304: Sapphire substrate 305: Active layer to be a semiconductor bonding surface 306: Electrode of light emitting element 307: End face formed by etching

Claims (3)

[Claims] 1. A method for manufacturing a nitride-based compound semiconductor device from a semiconductor wafer on which a nitride-based compound semiconductor is stacked, wherein a first groove is formed on the semiconductor wafer by laser irradiation, And / or a step of aligning and driving the cutting edge of the scriber along the first groove. 2. The method for manufacturing a nitride-based compound semiconductor device according to claim 1, wherein said nitride-based compound semiconductor is formed on a sapphire substrate. 3. A semiconductor light-emitting device having a nitride-based compound semiconductor layer on a sapphire substrate, wherein the semiconductor light-emitting device has a white turbid portion at an outer peripheral end of a safare substrate or at an outer peripheral end of the nitride-based compound layer. A semiconductor light emitting device characterized by the above-mentioned.