JP2014132606A - Method of manufacturing nitride semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a nitride semiconductor element utilizing a laser lift-off technology based on a novel separation mechanism.SOLUTION: A method of manufacturing a nitride semiconductor element includes: a step of preparing a sandwich structure in which a growth substrate obtained by growing a luminescent optical semiconductor laminate including a nitride semiconductor and a supporting substrate are opposed to each other via the optical semiconductor laminate; and a step of irradiating the optical semiconductor laminate with pulse laser light having such a condition that the optical semiconductor laminate is not decomposed by one-pulse irradiation, and the optical semiconductor is decomposed by two-pulse irradiation, from the growth substrate side, scanning the pulse laser light so that no region irradiated with less than two pulses remain on the whole surface of the optical semiconductor laminate to decompose the whole surface of an interface part of the optical semiconductor layer contacting with the growth substrate and to separate the growth substrate and the optical semiconductor laminate from each other.

Description

  The present invention relates to a method for manufacturing a nitride semiconductor device, and more particularly to a method for manufacturing a nitride semiconductor device using a laser lift-off technique.

  A semiconductor light emitting element using a nitride semiconductor such as GaN (gallium / nitrogen) can emit ultraviolet light or blue light, and can emit white light by using a phosphor. Such a semiconductor light emitting element is used for illumination, for example.

  As a substrate for growing a nitride semiconductor, a sapphire substrate is generally used. However, since the sapphire substrate has a relatively low thermal conductivity and poor heat dissipation, it is not suitable as a support substrate for a light emitting device to which a large current used for illumination or the like is input.

  In recent years, a method has been developed in which after a nitride semiconductor is grown on a sapphire substrate, the nitride semiconductor is bonded to a silicon substrate or the like advantageous for heat dissipation, and the sapphire substrate is removed by a laser lift-off technique. Laser lift-off is a technique for separating a sapphire substrate and a nitride semiconductor by irradiating a nitride semiconductor with laser light from the sapphire substrate side and thermally decomposing a part of the nitride semiconductor in contact with the sapphire substrate.

  When the size of the nitride semiconductor grown on the sapphire substrate is large, for example, 10 mm □ or more, it is difficult to uniformly irradiate the entire surface of the nitride semiconductor with laser light to separate the nitride semiconductor from the sapphire substrate. is there. In such a case, after dividing the nitride semiconductor grown on the sapphire substrate into a size that can be irradiated with laser light at a time, each of the divided nitride semiconductors is irradiated with laser light, and individual nitrides are irradiated. There is a method of sequentially separating a semiconductor from a sapphire substrate (for example, Patent Documents 1 and 2). In addition, without dividing the nitride semiconductor, a laser beam that irradiates a part of the nitride semiconductor is scanned, and the entire surface of the nitride semiconductor is irradiated with the laser beam. (For example, patent document 3).

Special table 2007-534164 gazette JP 2007-134415 A Japanese Patent No. 4948629

  In the conventional laser lift-off technique, the growth substrate and the optical semiconductor stack are separated by thermal decomposition of the optical semiconductor stack by laser light irradiation.

  One object of the present invention is a method for manufacturing a nitride semiconductor device using a laser lift-off technique, which separates a growth substrate and an optical semiconductor stack based on a separation mechanism different from a conventional separation mechanism. The object is to provide a method for manufacturing a semiconductor device.

  Another object of the present invention is to provide a method of manufacturing a nitride semiconductor device having a relatively large size and having higher reliability than the conventional method.

  According to one aspect of the present invention, a) a sandwich structure in which a growth substrate on which a light-emitting optical semiconductor stack including a nitride semiconductor is grown and a support substrate are opposed to each other with the optical semiconductor stack interposed therebetween is prepared. And b) irradiating the optical semiconductor stack with pulsed laser light from the growth substrate side, wherein the optical semiconductor stack is not decomposed by one pulse irradiation, and the optical semiconductor is decomposed by two pulse irradiation. Scanning the pulsed laser light so that no region irradiated with less than two pulses remains on the entire surface of the optical semiconductor stack, decomposing the entire interface portion of the optical semiconductor layer in contact with the growth substrate, and And a step of separating the optical semiconductor stack. A method for manufacturing a nitride semiconductor device is provided.

  By utilizing a laser lift-off technique based on a separation mechanism different from the conventional separation mechanism, a nitride semiconductor device having higher reliability than the conventional one can be obtained.

1A and 1B are a perspective view illustrating a wafer according to an embodiment and a plan view illustrating one chip obtained by dividing the wafer into a plurality of parts. 2A to 2E are cross-sectional views showing how a wafer or chip according to the embodiment is manufactured. FIG. 3A is a plan view illustrating a support according to the embodiment, and FIGS. 3B to 3D are cross-sectional views illustrating how the support according to the embodiment is manufactured. FIG. 4A is a plan view illustrating a semiconductor light emitting device according to an embodiment, and FIGS. 4B and 4C are cross-sectional views illustrating how the semiconductor light emitting device according to the embodiment is manufactured. FIG. 5 is a table showing the results of experiments conducted by the present inventors. 6A to 6F are plan views showing a pulse laser beam irradiation method in a laser lift-off process. 7A and 7B are photomicrographs showing the interface of the optical semiconductor laminate with the growth substrate. 8A to 8C are plan views showing other examples of the pulse laser beam irradiation method in the laser lift-off process. 9A to 9C are plan views showing other examples of the pulse laser beam irradiation method in the laser lift-off process.

  Hereinafter, a method for manufacturing a nitride semiconductor device according to an embodiment of the present invention, specifically, a semiconductor light emitting device including a nitride semiconductor will be described.

  1A and 1B are a schematic perspective view showing a manufactured wafer 100 and a plan view showing one chip 101 obtained by dividing the wafer 100 into a plurality of parts.

  As shown in FIG. 1A, the wafer 100 has a configuration in which a light emitting structure 101a is formed on a growth substrate 1 having an orientation flat 1a. The light emitting structure 101a includes a light-emitting optical semiconductor stack 2 and an electrode 7 for injecting a current into the optical semiconductor stack 2. The size of the wafer 100 is about 50 mm in diameter.

  As shown in FIG. 1B, an optical semiconductor stack 2 in which at least an n-type semiconductor layer, an active layer, and a p-type semiconductor layer are stacked is grown on a growth substrate 1 as shown in FIG. 1B. Furthermore, it has the structure which formed the electrodes 4 and 5 on it. A plurality of bank portions 2a and groove portions 2b are formed on the surface of the optical semiconductor laminate 2, and an electrode 4 is formed on each bank portion 2a, and an electrode 5 is formed on one groove portion 2b (in the drawing). The groove 2b is indicated by a dotted line). The size of the chip 101 is about 10 mm □.

  Hereinafter, a process of manufacturing the wafer 100 or the chip 101 will be described with reference to FIGS. 2A to 2E. 2A to 2E are cross-sectional views showing how the wafer 100 or the chip 101 is manufactured. Moreover, the relative size of each component shown in the figure is different from the actual one.

  First, as shown in FIG. 2A, a wafer-like C-plane sapphire substrate 1 as a growth substrate is prepared, and an optical semiconductor stack 2 made of a nitride-based semiconductor is formed using a metal organic chemical vapor deposition (MOCVD) method. To do. Specifically, for example, after the sapphire substrate 1 having a thickness of 430 μm is put into an MOCVD apparatus, thermal cleaning is performed, and after the GaN buffer layer 20 is grown, an n-type GaN layer 21 doped with Si or the like, an InGaN well layer, and A multiple quantum well light-emitting layer (active layer) 22 including a GaN barrier layer, a p-type AlGaN cladding layer 23 doped with Mg and the like, and a p-type GaN layer 24 are sequentially grown.

  In the example, the GaN buffer layer 20 was produced under the conditions of trimethylgallium gas flow rate: 10.4 μmol / min, ammonia gas flow rate: 3.3 L / min, substrate temperature: 500 ° C., and growth time: 3 min. Thereafter, the substrate temperature was raised to 1000 ° C., and the temperature was maintained for 30 seconds to crystallize the GaN buffer layer 20.

Further, an n-type GaN layer 21 having a film thickness of about 5 μm is formed by trimethylgallium gas flow rate: 45 μmol / min, ammonia gas flow rate: 4.4 L / min, silane gas flow rate: 2.7 × 10 ⁻⁹ mol / min. The substrate temperature was 1000 ° C., and the growth time was 100 min.

  Further, an InGaN well layer having a thickness of about 2.2 nm is formed by using a trimethylgallium gas flow rate: 3.6 μmol / min, a trimethylindium gas flow rate: 10 μmol / min, an ammonia gas flow rate: 4.4 L / min, and a substrate temperature: A GaN barrier layer having a film thickness of about 15 nm is formed under conditions of 700 ° C. and growth time: 33 sec. Trimethylgallium gas flow rate: 3.6 μmol / min, ammonia gas flow rate: 4.4 L / min, substrate temperature: 700 ° C. , Growth time: 320 sec. And these were repeated 5 periods and the active layer 22 was produced.

Further, a p-type AlGaN layer 23 having a thickness of about 40 nm is formed by using a trimethylgallium gas flow rate of 8.1 μmol / min, a trimethylaluminum gas flow rate of 7.5 μmol / min, an ammonia gas flow rate of 4.4 L / min, and CP2Mg. (Biscyclopentadienylmagnesium) Gas flow rate: 2.9 × 10 ⁻⁷ mol / min, substrate temperature: 870 ° C., growth time: 5 min, p-type GaN layer 24 having a thickness of about 150 nm Trimethylgallium gas flow rate: 18 μmol / min, ammonia gas flow rate: 4.4 L / min, CP2Mg (biscyclopentadienyl magnesium) gas flow rate: 2.9 × 10 ⁻⁷ mol / min, substrate temperature: It was fabricated under conditions of 870 ° C. and growth time: 7 min.

  The sapphire substrate 1 is a single crystal substrate having a lattice constant capable of epitaxial growth of GaN, and with respect to light having a wavelength of 362 nm that is an absorption edge wavelength of GaN so that the substrate can be peeled off by laser lift-off in a later process. Selected from transparent ones. In addition to sapphire, spinel, ZnO, or the like may be used.

  Next, as shown in FIG. 2B, a plurality of grooves 2b reaching the n-type GaN layer 21 are formed in the optical semiconductor stack 2 by a dry etching method using a resist mask and chlorine gas. The groove 2 b has a shape that gradually decreases in width toward the sapphire substrate 1. In the optical semiconductor stack 2, a region that is not etched constitutes a bank portion 2 a.

Next, as shown in FIG. 2C, an insulating layer 3 made of, for example, SiO _{2 is} formed by photolithography or the like so as to cover the side surface of the bank portion 2a and a part of the bottom surface of the groove portion 2b. The n-type GaN layer 21 and the p-type GaN layer 24 are exposed at the top surface of the bank portion 2b and part of the bottom surface of the groove portion 2a, respectively.

  Next, as shown in FIG. 2D, for example, Pt (film thickness: 1 nm) / Ag (film thickness: 150 nm) / Ti (film thickness: 100 nm) is formed on the optical semiconductor laminate 2 and the insulating layer 3 by an electron beam evaporation method or the like. / Au (film thickness 200 nm) is sequentially deposited and patterned by a lift-off method or the like, and the p-side electrode 4 is formed on the upper surface of the bank portion 2a (the surface of the p-type GaN layer 23 exposed from the insulating film 3) in the optical semiconductor stack 2. Form.

  Next, as shown in FIG. 2E, for example, Ti (film thickness: 25 nm) / Pt (film thickness: 100 nm) / Au (film thickness: 1000 nm) is formed on the optical semiconductor laminate 2 and the insulating layer 3 by an electron beam evaporation method or the like. The n-side electrode 5 is formed on a part of the bottom surface of the groove 2b (the surface of the n-type GaN layer 20 exposed from the insulating film 3) in the optical semiconductor stack 2 by sequentially depositing and patterning by a lift-off method or the like.

  Thus, the wafer 100 (see FIG. 1A) is completed. Thereafter, the wafer 100 is divided into a plurality of pieces by dicing to form chips 101 (see FIG. 1B).

  FIG. 3A is a plan view showing the support 102 that is bonded to the chip 101 shown in FIG. 1B. The support body 102 is formed with first and second connection electrodes 7a and 7b on a support substrate 10 having an insulating film 9 formed on the surface thereof, and is further anisotropically conductive only in the thickness direction. The conductive conductive adhesive 8 is applied.

  Hereinafter, the process of manufacturing the support body 102 will be described with reference to FIGS. 3B to 3D. 3B to 3D are cross-sectional views showing how the support 102 is manufactured.

First, as shown in FIG. 3B, a silicon substrate 10 as a support substrate is prepared, and a thermal oxidation process is performed to form an insulating film (thermally oxidized SiO ₂ film) 9 on the surface. The support substrate 10 is preferably made of a material having a thermal expansion coefficient close to that of sapphire (7.5 × 10 ⁻⁶ / K) or GaN (5.6 × 10 ⁻⁶ / K) and having high thermal conductivity. For example, Si, AlN, Mo, W, CuW, or the like can be used. The film thickness of the insulating film 9 should just be the thickness which can achieve the objective of ensuring insulation.

  Next, as shown in FIG. 3C, for example, Ti (film thickness 25 nm) / Pt (film thickness 100 nm) / Au (film thickness 1000 nm) is sequentially deposited on the insulating film 9 by an electron beam evaporation method or the like, and lift-off is performed. Patterning is performed by a method or the like to form first and second connection electrodes 7a and 7b. The first and second connection electrodes 7a and 7b are formed at positions corresponding to the p-side electrode 4 and the n-side electrode 5, respectively, when bonded to the chip 101 (see FIG. 1B).

  Next, as shown in FIG. 3D, an anisotropic conductive adhesive 8 having conductivity only in the thickness direction is applied on the insulating film 9 and the first and second connection electrodes 7a and 7b, and about 60 Heat treatment is performed at 0 ° C. Note that the adhesive 8 only needs to be applied to a region overlapping the chip 101 when being bonded to the chip 101 (see FIG. 1B).

  Thus, the support body 102 is completed.

  4A is a plan view showing the semiconductor light emitting device 103 formed by bonding the chip 101 shown in FIG. 1B and the support body 102 shown in FIG. 3A and then removing the sapphire substrate 1 of the chip 101. FIG. By supplying electric power from the first and second connection electrodes 7 a and 7 b, light is emitted from the optical semiconductor stack 2.

  Hereinafter, with reference to FIGS. 4B and 4C, a process of manufacturing the semiconductor light emitting device 103 will be described. 4B to 4C are cross-sectional views showing how the semiconductor light emitting device 103 is manufactured.

First, as shown in FIG. 4B, the p-side electrode 4 and the first connection electrode 7a face each other through the anisotropic conductive adhesive 9 between the chip 101 and the support body 102 prepared in advance. And it bonds so that the n side electrode 5 and the 2nd connection electrode 7b may oppose. And it heats to 300 degreeC in the state pressurized with the pressure of 800 N / m < ² >. The anisotropic conductive adhesive 9 is deformed so that no gap is formed between the chip 101 and the support 102. As a result, a sandwich structure in which the sapphire substrate 1 and the support substrate 10 face each other with the optical semiconductor stack 2 interposed therebetween is completed.

  Thereafter, the UV excimer laser Le having a wavelength of 248 nm is irradiated from the sapphire substrate 1 side to decompose the GaN layer (the optical semiconductor stack 2, particularly the GaN buffer layer 20), thereby peeling off the sapphire substrate 1 by laser lift-off. Details of the irradiation conditions and irradiation method of the excimer laser Le will be described later.

  Next, as shown in FIG. 4C, Ga generated by laser lift-off is removed with hydrochloric acid or the like. As a result, the n-type GaN layer 21 is exposed. Any surface treatment can be used as long as it can etch a nitride semiconductor, and acids such as phosphoric acid, sulfuric acid, KOH, and NaOH, and chemicals such as alkali can also be used. The surface treatment may be performed by dry etching using Ar plasma or chlorine plasma, polishing, or the like.

  Thus, the semiconductor light emitting device 103 is completed.

  The present inventor has found that a unique phenomenon occurs in the optical semiconductor stack 2 by irradiating the optical semiconductor stack 2 with laser light Le having specific conditions in the laser lift-off process shown in FIG. 4B.

FIG. 5 is a table showing the results of experiments conducted by the present inventors. In the laser lift-off process, the present inventor shows the irradiation energy density of pulsed laser light (excimer laser, wavelength 248 nm, energy about 5 eV) whose light irradiation time in one pulse is about 2.5 nsec, as shown in FIG. 800 mJ ^/ in cm ² ~830mJ / cm 2 to varied, experiments were conducted to be irradiated from the sapphire substrate 1 side to the optical semiconductor lamination 2 (especially GaN buffer layer 20).

As a result, it was found that when the irradiation energy density of the pulse laser beam is 830 mJ / cm ² or more, the optical semiconductor stack 2 is completely separated from the growth substrate 1 by only one pulse irradiation.

Further, when the irradiation energy density of the pulse laser beam is 825 mJ / cm ² , the optical semiconductor stack 2 is not completely separated from the growth substrate 1 only by one pulse irradiation, and the same region is again irradiated with one pulse. That is, it was found that the optical semiconductor laminate 2 was completely separated from the growth substrate 1 by irradiating a total of two pulses.

Further, when the irradiation energy density of the pulsed laser beam is 815 mJ / cm ² , the optical semiconductor stack 2 is not separated from the growth substrate 1 at all by only one pulse irradiation, and the same region is again irradiated with one pulse. It was found that the optical semiconductor laminate 2 was completely separated from the growth substrate 1 by irradiating a total of two pulses. Further, at this time, it was found that the complete separation of the optical semiconductor stack 2 and the growth substrate 1 does not depend on the time from the first pulse irradiation to the second pulse irradiation.

Further, it was found that when the irradiation energy density of the pulse laser beam is 800 mJ / cm ² or less, the optical semiconductor stack 2 is not completely separated from the growth substrate 1 even if the pulse irradiation is performed twice or more times.

  In a general laser lift-off process, the optical semiconductor stack is separated from the growth substrate using heat generated by light absorption of the optical semiconductor stack (particularly, the GaN buffer layer). In other words, by laser irradiation, the interface portion of the optical semiconductor stack with the growth substrate is heated and pyrolyzed to separate the optical semiconductor stack from the growth substrate.

  According to this separation mechanism, if the irradiation energy density of the pulse laser beam does not reach the energy density required for the thermal decomposition of the optical semiconductor stack, the optical semiconductor stack will not be decomposed no matter how many times pulse irradiation is performed. On the other hand, if the irradiation energy density of the pulse laser beam reaches the energy density required for thermal decomposition of the optical semiconductor stack, the optical semiconductor stack is decomposed by only one pulse irradiation. In addition, when the irradiation time in one pulse is extremely short, the optical semiconductor stack is eventually subjected to a temperature required for thermal decomposition by repeatedly performing pulse irradiation before the temperature of the optical semiconductor stack heated by light absorption is completely lowered. Reach and disassemble.

Based on this decomposition mechanism due to heat generation, for example, when a pulsed laser beam having an irradiation energy density of 815 mJ / cm ² is irradiated to the optical semiconductor stack, the optical semiconductor stack is not decomposed even after one pulse irradiation. It is assumed that the optical semiconductor stack does not decompose no matter how many times the region is pulsed. However, according to the experimental results, it was found that when the same region was irradiated with two pulses, the optical semiconductor stack was completely decomposed. Moreover, this decomposition does not depend on the time from the first pulse irradiation to the second pulse irradiation, and the second pulse irradiation is performed even if the temperature of the optical semiconductor stack heated by the first pulse irradiation is completely lowered. It was found that the optical semiconductor stack was decomposed by performing the above. Such a decomposition mechanism cannot be explained by the conventional decomposition mechanism due to heat generation, and it is considered that the optical semiconductor stack and the growth substrate are separated based on a separation mechanism different from the conventional separation mechanism.

The experimental results, only one such pulse irradiation without disassembling the optical semiconductor multilayer, irradiation energy density of 2 pulse irradiation to the decomposed optical semiconductor multilayer pulsed laser ^{light, 800mJ / cm 2 ~825mJ / cm} 2 of about It is thought that. In addition, it is considered that the wavelength of the pulsed laser light may be any wavelength that allows the optical semiconductor stack to absorb light.

  Next, a pulse laser light irradiation method in the laser lift-off process using such a unique phenomenon will be described.

  6A to 6F are plan views showing a state in which pulse laser light is irradiated to the interface (that is, the GaN buffer layer 20) of the optical semiconductor multilayer 2 with the growth substrate 1 in the laser lift-off process shown in FIG. 4B. 6A to 6C show a first scanning process in which the entire surface of the GaN buffer layer 20 is sequentially scanned by scanning with a pulse laser beam, and FIGS. 6D to 6F scan again with the pulse laser beam. The second scanning step of sequentially irradiating the entire surface of the GaN buffer layer 20 is shown. The direction along one side of the square GaN buffer layer 20 (or optical semiconductor stack 2) is taken as the x axis, and the direction perpendicular to the x axis in the plane of the GaN buffer layer 20 (or optical semiconductor stack 2) is taken as the y axis. Define an xy Cartesian coordinate system.

  In the figure, in the GaN buffer layer 20, the region irradiated with one pulse by the pulsed laser beam is indicated by a diagonal pattern with a relatively wide pitch, and the region irradiated with two or more pulses by the pulsed laser beam has a relative pitch. Is shown with a narrow diagonal pattern. In addition, the region irradiated with the pulse laser beam most recently is indicated by a solid line, and the region irradiated earlier than that is indicated by a dotted line.

The pulsed laser light for irradiating the GaN buffer layer 20 is under the conditions that the wavelength is 248 nm, the irradiation energy density is 815 mJ / cm ² , and the light irradiation time per pulse is 0.2 seconds. The size of the unit irradiation region that irradiates the GaN buffer layer 20 with one pulse of laser light is set to 250 μm □.

  First, as shown in FIG. 6A, one pulse of pulsed laser light is irradiated near the corner of the GaN buffer layer 20. At this time, the region irradiated with one pulse of the pulse laser beam is referred to as a unit irradiation region A11. The unit irradiation area A11 is about 250 μm square, for example. Thereafter, one pulse of laser light is irradiated along the x-axis positive direction at a position shifted by 150 μm pitch from the unit irradiation region A11. At this time, the region irradiated with one pulse of the pulse laser beam is referred to as a unit irradiation region A12.

  The unit irradiation area A11 and the unit irradiation area A12 have areas that partially overlap each other. This region is irradiated with two pulses, and the GaN layer in this region is decomposed and separated from the growth substrate 1. The width of the region where the unit irradiation region A11 and the unit irradiation region A12 overlap is 100 μm, but the width of the region where the GaN layer was actually decomposed was 100 μm or less. This is considered to be because the irradiation energy density at the edge portion of the unit irradiation region is lower than the set irradiation energy density. Note that the GaN layer in a region other than the region irradiated with two pulses is in a state of being bonded to the growth substrate 1.

  In this way, the pulsed laser light irradiation is repeated in the positive x-axis direction so that the unit irradiation regions irradiated with the pulsed laser light are arranged from one end side to the other end side of the GaN buffer layer 20. At this time, the pulse laser beam is irradiated so that adjacent unit irradiation regions overlap.

  Next, as shown in FIG. 6B, one pulse of laser light is irradiated from the unit irradiation region A11 to a position shifted by 150 μm pitch along the positive y-axis direction. At this time, the region irradiated with one pulse of the pulse laser beam is referred to as a unit irradiation region A21. Thereafter, one pulse of laser light is irradiated along the x-axis positive direction at a position shifted by 150 μm pitch from the unit irradiation region A21. At this time, the region irradiated with one pulse of the pulse laser beam is referred to as a unit irradiation region A22.

  The unit irradiation areas A11, A12 and the unit irradiation areas A21, 22 have areas that partially overlap each other. This region is irradiated with at least two pulses, and the GaN layer in this region is decomposed and separated from the growth substrate 1. Note that the GaN layer in a region other than the region irradiated with two or more pulses is in a state of being bonded to the growth substrate 1.

  Thus, the pulse laser light irradiation is repeated so that the unit irradiation regions irradiated with the pulse laser light are arranged in a matrix on the entire surface of the GaN buffer layer 20. That is, the raster scanning of the pulse laser beam is performed so that the unit irradiation regions adjacent to each other partially overlap. Then, as shown in FIG. 6C, a multiple irradiation region Am irradiated with two or more pulses of pulsed laser light is formed in a net shape (or lattice shape) on the entire surface of the GaN buffer layer 20. The multiple irradiation region Am is continuously formed up to the side end faces of the growth substrate 1 and the optical semiconductor stack 2. A region other than the reticulated multiple irradiation region Am becomes a single irradiation region As irradiated with one pulse of pulsed laser light. The single irradiation region As has a shape surrounded by the multiple irradiation region Am.

  Next, the size of the unit irradiation region that irradiates the GaN buffer layer 20 with one pulse of pulsed laser light is set to 150 μm □. Then, as shown in FIGS. 6D to 6F, the pulse laser beam is sequentially irradiated from the single irradiation region As located near the corner of the GaN buffer layer 20, and the entire surface of the GaN buffer layer 20 is irradiated. That is, the pulse laser beam is scanned over the entire surface of the GaN buffer layer 20 so that no region irradiated with less than two pulses remains. As a result, the entire surface of the GaN buffer layer 20 is irradiated with two or more pulses, and the optical semiconductor stack 2 and the growth substrate 1 are completely separated.

When the GaN layer (the optical semiconductor stack 2, particularly the GaN buffer layer 20) is decomposed, nitrogen gas is generated. For example, in FIG. 6A, the unit irradiation regions A11 and A12 are irradiated with a pulse laser beam having an energy density sufficient to thermally decompose the GaN buffer layer (that is, a pulse laser beam having an irradiation energy density of 830 mJ / cm ² or more). Assume that At this time, since the unit irradiation regions A11 and A12 are entirely decomposed, a relatively large amount of nitrogen gas is generated at the interface between the GaN layer and the growth substrate 1. Then, due to the pressure of nitrogen gas generated in a relatively large amount, excessive stress is applied to the GaN layer (particularly, the optical semiconductor stack 2) particularly at the boundary between the region irradiated with the pulse laser beam and the region not irradiated. There is a possibility of joining. Thereby, a crack may generate | occur | produce in a GaN layer (especially optical semiconductor lamination 2).

  When the unit irradiation regions A11 and A12 are irradiated with pulsed laser light having a condition that the unit irradiation regions A11 and A12 are not decomposed only by irradiating the GaN layer with one pulse but are decomposed when two or more pulses are irradiated, the unit irradiation region Only the region where A11 and the unit irradiation region A12 overlap is decomposed. For this reason, only a relatively small amount of nitrogen gas is generated at the interface between the GaN layer and the growth substrate 1. Therefore, it is considered that the stress applied to the GaN layer (particularly the optical semiconductor stack 2) by the nitrogen gas is limited.

  As shown in FIGS. 6D to 6F, when decomposing the single irradiation region As having a relatively large area, the generated nitrogen gas passes through the multiple irradiation region Am in which the GaN layer is decomposed, and the side end surface. To the outside. For this reason, it is considered that the stress applied to the GaN layer (particularly the optical semiconductor stack 2) by the nitrogen gas is suppressed.

  From the above, the pulse laser light irradiation method shown in the embodiment is more effective than the method of sequentially irradiating pulse laser light having an energy density sufficient to thermally decompose the GaN layer. It is considered that the stress applied to 2) can be suppressed and the reliability of the manufactured semiconductor light emitting device can be improved.

  7A and 7B are photomicrographs showing the interface of the GaN buffer layer with the growth substrate in the state shown in FIGS. 6C and 6F. In FIG. 7A, a gray (or lattice) region shown in gray is a multiple irradiation region, which is a region where the GaN buffer layer and the growth substrate are separated. In addition, a black region occupying the mesh portion of the multiple irradiation region is a single irradiation region, which is a region where the GaN buffer layer and the growth substrate are joined. In FIG. 7B, the entire surface is shown in gray, that is, the GaN buffer layer and the growth substrate are completely separated.

  From FIG. 7A, the first scanning of the pulsed laser light (steps shown in FIGS. 6A to 6C) results in a net-like multiple irradiation region (decomposition region) in the GaN buffer layer and a single irradiation region (bonding region) that occupies the mesh portion. It can be seen that and are formed. Moreover, it can be seen from FIG. 7B that the GaN buffer layer and the growth substrate are completely separated by the second scan of the pulse laser beam (steps shown in FIGS. 6D to 6F).

Range of illumination energy density of 2 pulse irradiation to the decomposing pulsed laser beam a GaN crystal, in the embodiment, is generally the range of ^{800mJ / cm 2 ~825mJ / cm 2} . However, the inventors have found that the range of the irradiation energy density varies depending on the thickness of the growth substrate, the growth conditions of the optical semiconductor stack, and the like. When the semiconductor light emitting device is manufactured under conditions other than the manufacturing conditions of the semiconductor light emitting device shown in the embodiment, the optical semiconductor stack (or GaN buffer layer) is irradiated with pulsed laser light while changing the irradiation energy density, and the microscope If the decomposition state of the optical semiconductor stack (or GaN buffer layer) is confirmed by, for example, a suitable range of irradiation energy density under the manufacturing conditions can be determined.

  FIG. 8A to FIG. 8C are plan views showing other examples of the pulse laser beam irradiation method shown in the embodiment. 8A to 8C particularly show a pulse laser beam irradiation method according to the second scan.

  In this example, after forming the net-like multiple irradiation region Am and the single irradiation region As occupying the mesh portion in the GaN buffer layer 20 (FIG. 8A), as shown in FIG. 8B, from the periphery of the GaN buffer layer 20 The single irradiation region As located inside is irradiated. As a result, the inner portion of the optical semiconductor stack 2 is separated from the growth substrate 1, but the peripheral portion thereof is in a state of being bonded to the growth substrate 1. After that, as shown in FIG. 8C, the single irradiation region As located at the periphery of the GaN buffer layer 20 is irradiated to completely separate the optical semiconductor stack 2 and the growth substrate 1.

  6D to 6F, when the pulse laser beam is irradiated from the single irradiation region As located in the vicinity of the corner of the GaN layer, the portion separated from the growth substrate 1 of the GaN layer is floated. Therefore, depending on the flow of nitrogen gas related to the decomposition of the GaN layer, the floating portion may be warped or bent, and stress may be applied to the GaN layer (particularly, the optical semiconductor stack 2). As shown in FIGS. 8A to 8C, if the pulsed laser beam is irradiated first from the single irradiation region As located in the inner part of the GaN layer, the GaN layer caused by warping / deflection (particularly the optical semiconductor stack 2). It is thought that stress on the body is reduced.

  9A to 9C are plan views showing other examples of the pulse laser beam irradiation method shown in the embodiment. 9A to 9C particularly show a pulse laser light irradiation method according to the first scan.

  First, as shown in FIG. 9A, one pulse of laser light is irradiated in the vicinity of the first corner of the GaN buffer layer 20 (unit irradiation region A11). Thereafter, one pulse of laser light is irradiated along the x-axis positive direction at a position shifted by 150 μm pitch from the unit irradiation region A11. In this way, the pulsed laser light irradiation is repeated in the positive x-axis direction so that the unit irradiation regions irradiated with the pulsed laser light are arranged from one end side to the other end side of the GaN buffer layer 20.

  Next, as shown in FIG. 9B, one pulse laser beam is irradiated from the unit irradiation region A11 to a position shifted by 150 μm pitch along the y-axis positive direction and 75 μm pitch along the x-axis negative direction (unit). Irradiation area A21). Thereafter, one pulse of laser light is irradiated along the x-axis positive direction at a position shifted by 150 μm pitch from the unit irradiation region A21. In this way, the pulsed laser light irradiation is repeated in the positive x-axis direction so that the unit irradiation regions irradiated with the pulsed laser light are arranged from one end side to the other end side of the GaN buffer layer 20.

  Then, as shown in FIG. 9C, one pulse laser beam is irradiated from the unit irradiation region A21 to a position shifted by 150 μm pitch along the y-axis positive direction and 75 μm pitch along the x-axis positive direction (unit irradiation). Region A31), pulse laser light irradiation is repeated in the positive x-axis direction so that unit irradiation regions irradiated with pulse laser light are arranged from one end side to the other end side of the GaN buffer layer 20 interface. By such raster scanning with pulsed laser light, the multiple irradiation region Am irradiated with two or more pulses of pulsed laser light is formed in a net shape on the entire surface of the GaN buffer layer 20.

  In the steps shown in FIGS. 6A to 6C, for example, in the region where the unit irradiation regions A11 and A12 and the unit irradiation regions A21 and A22 overlap, the pulse laser light is irradiated four times. It has been confirmed by the present inventor that when the same region of the GaN layer is irradiated with four or more pulses of laser light, the separated GaN layer and the growth substrate 1 may be bonded again. Therefore, it is preferable that the number of pulses irradiated to the GaN layer is smaller.

  As shown in FIGS. 9A to 9C, by shifting the odd-numbered row components and the even-numbered row components of the unit irradiation regions arranged in a matrix in the x-axis direction, there is no region that is irradiated with four pulses. However, only the region irradiated with 3 pulses remains. By using such a pulse laser light irradiation method, the number of pulses irradiated to the GaN layer can be reduced.

  The GaN-based crystal constituting the optical semiconductor stack 2 has a hexagonal crystal structure. And it has a C surface parallel to the C surface sapphire substrate 1. Since the hexagonal M-plane is easy to cleave, the row direction and the column direction of the unit irradiation region in which the pulse laser beam is arranged in an edge line direction (x-axis direction and y-axis direction) It is preferable to deviate by about 10 ° to 15 °, for example, from the direction along the M plane of 2 (GaN-based crystal).

  As mentioned above, although this invention was demonstrated along the Example and the modification, this invention is not limited to these. For example, in the embodiments, a method for manufacturing a semiconductor light emitting element including a nitride semiconductor has been described. However, the present invention can also be applied to other electronic devices including a nitride semiconductor. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

DESCRIPTION OF SYMBOLS 1 ... Growth substrate, 2 ... Optical semiconductor lamination | stacking (GaN-type light emission part), 3 ... Insulating layer, 4 ... P side electrode, 5 ... N side electrode, 7 ... Connection electrode, 8 ... Anisotropic conductive adhesive, 9 DESCRIPTION OF SYMBOLS ... Insulating layer, 10 ... Support substrate, 100 ... Wafer, 101 ... Chip, 102 ... Support, 103 ... Semiconductor light emitting element.

Claims (5)

a) a step of preparing a sandwich structure in which a growth substrate including a nitride semiconductor and having a light emitting property and having a light emitting property grown thereon and a supporting substrate are opposed to each other with the optical semiconductor laminate interposed therebetween;
b) irradiating the optical semiconductor stack with pulsed laser light having a condition that the optical semiconductor stack is not decomposed by one-pulse irradiation but the optical semiconductor is decomposed by two-pulse irradiation from the growth substrate side; The pulse laser beam is scanned so that a region irradiated with less than two pulses does not remain on the entire surface of the stack, the entire interface portion of the optical semiconductor layer in contact with the growth substrate is decomposed, and the growth substrate and the optical semiconductor stack And a step of separating
A method for manufacturing a nitride semiconductor device comprising: Said step b)
b1) When the region where the pulse laser beam irradiates the interface portion of the optical semiconductor stack with one pulse is defined as a unit irradiation region, the pulse laser beam is irradiated so that the unit irradiation regions adjacent to each other partially overlap each other. Raster scanning is performed to irradiate the entire interface portion of the optical semiconductor stack with two or more pulses, to a multi-irradiation region having a net-like or lattice-like overall planar shape, and to one region irradiated with one pulse and excluding the multi-irradiation region Forming a defined single-irradiation region; and
b2) irradiating the single-shot irradiation region with the pulsed laser beam;
The method for manufacturing a nitride semiconductor device according to claim 1, comprising:   In the sub-step b2), the single irradiation region located at the periphery of the interface portion of the optical semiconductor stack after irradiating the single laser irradiation region positioned inside the periphery of the interface portion of the optical semiconductor stack with the pulse laser beam The method of manufacturing a nitride semiconductor device according to claim 2, wherein the pulsed laser beam is irradiated. The optical semiconductor stack has a hexagonal structure having a C plane in a plane parallel to the growth substrate surface,
4. The method of manufacturing a nitride semiconductor device according to claim 2, wherein in the sub-step b <b> 1), the edge line direction of the pulse laser beam is deviated from the direction along the M plane of the optical semiconductor stack. The optical semiconductor stack includes a GaN-based crystal,
The pulsed laser light, the optical semiconductor stacked a wavelength to light absorption, the nitride semiconductor of the irradiation energy density claim 1, wherein any one is in the range of 800mJ ^/ cm ² ~825mJ ^/ cm 2 Device manufacturing method.