Method for manufacturing nitride semiconductor light emitting device

Abstract

To provide a manufacturing method of a nitride semiconductor light-emitting element improved in quality of a structure that a current flows in a vertical direction.SOLUTION: A manufacturing method of a nitride semiconductor light-emitting element includes: a first step of growing an n-AlGaN layer 12 including a low AlN molar fraction region LC1, in which an AlN molar fraction is lower than that in the other region, at a surface side of a second AlN layer 11; and a second step of executing laser lift-off to peel the n-AlGaN layer 12 from the second AlN layer 11.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a nitride semiconductor light-emitting device. [Background technology]

[0002] It is known that ultraviolet light-emitting devices are fabricated using an insulating sapphire substrate or an AlN substrate as an underlayer and an AlGaN-based nitride semiconductor crystal grown on the underlayer. For example, Patent Document 1 discloses that AlN nuclei are formed on the surface of a sapphire substrate, the AlN nuclei are embedded to reduce threading dislocations, and then high-speed vertical crystal growth is repeated to obtain a high-quality AlN layer as an underlayer, on which a high-quality AlGaN layer with an AlN mole fraction of 0.7 or more is then formed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-54780 [Non-Patent Document 1] Michael K. Kelly Michael K. Kelly et al"Large Free-Standing GaN Substrates by Hydride Vapor Phase Epitaxy and Laser-Induced Liftoff", Japanese Journal of Applied Physics 1999 Jpn.J.Appl.Phys. 38 L217 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned method has the following two problems. The first problem is that when AlGaN crystals are grown on an AlN layer using MOCVD or other methods, compressive stress is applied to the AlGaN layer due to the difference in lattice constants between the AlN layer and the AlGaN layer, which causes lattice relaxation in the AlGaN layer. The second problem is that because an insulating substrate is used, both the p-side electrode and the n-side electrode of the element are formed on the wafer surface, which means that current flows in a direction perpendicular to the thickness direction of the element (i.e., in the direction in which the element expands (laterally)), resulting in non-uniform current flow in the light-emitting region. Furthermore, the electrical resistance of the element increases.

[0005] The first problem can be overcome in AlGaN growth with a high AlN mole fraction of 0.7 or more by using the above-mentioned method disclosed in Patent Document 1. However, in AlGaN growth with an AlN mole fraction of less than 0.7, lattice relaxation occurs, and crystal defects of 3 to 5 × 10 9 / cm 2 The second problem can be overcome by using the technique disclosed in Non-Patent Document 1, for example. Specifically, the second problem can be overcome by using a laser to peel off the nitride semiconductor crystal from the sapphire substrate (laser lift-off (LLO) technique), providing electrodes on the front and back surfaces of the peeled nitride semiconductor crystal, and passing a current through the crystal in the thickness direction (i.e., vertical direction).

[0006] When using the LLO technique to delaminate AlGaN crystals from sapphire or AlN substrates, it is conceivable to use either an excimer laser with a wavelength of 248 nm or a YAG laser with a wavelength of 266 nm. However, when using lasers with these wavelengths for LLO, it is necessary to provide an AlGaN layer with a low AlN mole fraction between the substrate and the crystal to be delaminated, as this layer is susceptible to decomposition due to absorption of laser light of these wavelengths. For example, even if high-quality AlGaN crystals with few dislocations are produced using the technique described in Patent Document 1, providing an AlGaN layer with a low AlN mole fraction between the substrate and the crystal to adopt the LLO technique could result in lattice relaxation due to the difference in lattice constant between the low-AlN mole fraction AlGaN layer and the high-quality, high-AlN mole fraction AlGaN crystal with few dislocations, ultimately reducing the crystallinity of the AlGaN crystal.

[0007] The present invention has been made in view of the above-mentioned conventional circumstances, and an object to be achieved is to provide a method for manufacturing a nitride semiconductor light-emitting device having a high-quality structure in which current flows in the vertical direction. [Means for solving the problem]

[0008] The method for manufacturing a nitride semiconductor light-emitting device of the present invention includes the steps of: a first step of growing an AlGaN layer on a surface side of an underlayer, the AlGaN layer having a low AlN mole fraction region in which the AlN mole fraction is lower than that of other regions; a second step of performing laser lift-off to remove the AlGaN layer from the underlying layer; Equipped with.

[0009] According to this configuration, by performing laser lift-off in the second step, the low AlN mole fraction region grown in the first step can be decomposed, and the AlGaN layer can be effectively separated from the underlayer. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing the structure of a nitride semiconductor light-emitting device according to Example 1. FIG. [Figure 2]1 is an electron microscope image showing an enlarged view of a second AlN layer and an n-AlGaN layer in the nitride semiconductor light-emitting device of Example 1. [Figure 3] 1 is a schematic diagram showing a state in which the nitride semiconductor light-emitting element of Example 1 is attached to a holding substrate and laser light is irradiated from the back surface of the sapphire substrate. FIG. [Figure 4] 1 is an electron microscope image showing an enlarged view of a second AlN layer and an AlGaN layer after the nitride semiconductor light-emitting element of Example 1 is irradiated with laser light. [Figure 5] 2 is a schematic diagram showing a state in which the sapphire substrate is peeled off from the supporting substrate together with the low AlN mole fraction region in the nitride semiconductor light-emitting device of Example 1. FIG. [Figure 6] In the nitride semiconductor light-emitting device of Example 1, (A) is an electron microscope image of the exposed n-AlGaN layer on the support substrate side, and (B) is an electron microscope image of the exposed n-AlGaN layer on the sapphire substrate side. [Figure 7] FIG. 2 is a schematic diagram showing the structure of a nitride semiconductor light-emitting device according to Example 2. [Figure 8] 10A and 10B are electron microscope images of the surface of the second AlN layer on which convex portions are formed in the nitride semiconductor light-emitting device of Example 2, where (A) is a planar electron microscope image and (B) is a side microscope image. [Figure 9] 10 is an electron microscope image showing an enlarged view of a second AlN layer and a u-AlGaN layer in the nitride semiconductor light-emitting device of Example 2. [Figure 10] Electron microscope images showing the nitride semiconductor light-emitting device of Example 2 after the sapphire substrate has been peeled off from the holding substrate, where (A) is an electron microscope image of a side view from the holding substrate side, (B) is an electron microscope image of a side view from the sapphire substrate side, (C) is an electron microscope image of the exposed surface of the u-AlGaN layer on the holding substrate side, and (D) is an electron microscope image of the exposed surface of the second AlN layer on the sapphire substrate side. [Figure 11] 10 is a schematic diagram showing a state in which the sapphire substrate is peeled off from the supporting substrate in the nitride semiconductor light-emitting device of Example 2. FIG. [Figure 12]FIG. 10 is a schematic diagram showing the structure of a nitride semiconductor light-emitting device according to Example 3. [Figure 13] 10 is an electron microscope image showing an enlarged view of a second AlN layer and an AlGaN layer in the nitride semiconductor light-emitting device of Example 3. [Figure 14] 10 is an electron microscope image of a side view of the AlGaN layer in the nitride semiconductor light-emitting device of Example 3 after the sapphire substrate has been peeled off from the supporting substrate. DETAILED DESCRIPTION OF THE INVENTION

[0011] A preferred embodiment of the present invention will now be described.

[0012] In the method for manufacturing a nitride semiconductor light-emitting device of the present invention, a convexity forming step of forming a plurality of convexities on the surface of the underlayer may be performed before performing step 1. According to this configuration, the convexities formed on the surface of the underlayer serve to reduce crystal defects in the AlGaN layer and also to facilitate peeling of the AlGaN layer from the underlayer, thereby enabling better peeling of the AlGaN layer from the underlayer.

[0013] In the method for manufacturing a nitride semiconductor light-emitting device of the present invention, the base layer can be formed of either AlGaN or AlN. With this configuration, when the base layer and the AlGaN layer are grown in layers, different types of layers can be produced by adjusting the supply of Al to the reactor.

[0014] In the method for manufacturing a nitride semiconductor light-emitting device of the present invention, the low AlN mole fraction region may have a first region and a second region that overlap in the thickness direction and have different AlN mole fractions, and the first region may be located between the second region and the surface of the underlayer. With this configuration, when laser lift-off is performed, peeling is likely to be contained within the low AlN mole fraction region.

[0015] In the method for manufacturing a nitride semiconductor light-emitting device of the present invention, the first region may be located between the second region and the surface of the underlayer, and may have a higher AlN mole fraction than the second region. With this configuration, when laser lift-off is performed, the second region can absorb laser light and decompose, thereby causing separation between the first region and the second region.

[0016] In the method for manufacturing a nitride semiconductor light-emitting device of the present invention, the first region may be located between the second region and the surface of the underlayer, and may have a lower AlN mole fraction than the second region. With this configuration, when laser lift-off is performed, the first region can absorb laser light and decompose, thereby causing delamination between the first region and the underlayer.

[0017] Next, Examples 1 to 3 embodying the method for manufacturing a nitride semiconductor light-emitting device of the present invention will be described with reference to the drawings.

[0018] Example 1 As shown in Fig. 1, the nitride semiconductor light-emitting device 1 of Example 1 includes a sapphire substrate 10A, a first AlN layer 10B, a second AlN layer 11, an n-AlGaN layer 12, and a light-emitting layer 13. The light-emitting layer 13 includes a first guide layer 13A, a double quantum well active layer 13B, and a second guide layer 13C. The nitride semiconductor light-emitting device 1 is a test structure for checking the level of crystal defects, and is obtained by performing crystal growth up to the second guide layer 13C located on the surface of the double quantum well active layer 13B that functions as the light-emitting layer 13. The nitride semiconductor light-emitting device 1 of Example 1 is grown by stacking layers using MOCVD (metal-organic chemical vapor deposition).

[0019] The C-plane ((0001) plane) of the sapphire substrate 10A is the surface (the front is the upper side in FIG. 1, the same applies below). The first AlN layer 10B is deposited on the surface of the sapphire substrate 10A by sputtering. The first AlN layer 10B is an underlayer. The first AlN layer 10B contains at least AlN. The molar fraction of AlN in the first AlN layer 10B is 1. The thickness of the first AlN layer 10B is 175 nm. After the first AlN layer 10B is deposited, annealing is performed in an N2 (nitrogen) atmosphere at 1700°C for 3 hours. In this way, an AlN template substrate 10 having the sapphire substrate 10A and the first AlN layer 10B is fabricated by sputtering. Thereafter, a layer structure is formed by MOCVD.

[0020] The AlN template substrate 10 is placed in a reactor capable of carrying out the MOCVD method (hereinafter simply referred to as the reactor), and while NH3 (ammonia), which is an N (nitrogen) raw material, is flowed onto the surface of the AlN template substrate 10 (the surface of the first AlN layer 10B) (hereinafter, the supply is not stopped), the temperature of the AlN template substrate 10 is raised to 1200°C in an H2 (hydrogen) atmosphere, and then maintained at that temperature for 10 minutes.

[0021] Next, a second AlN layer 11 is stacked on the surface of the first AlN layer 10B for crystal growth. The thickness of the second AlN layer 11 is 1 μm. The second AlN layer 11 is formed by supplying TMAl (trimethylaluminum), an Al (aluminum) raw material, into a reactor while the temperature of the AlN template substrate 10 is set to 1200°C. The mole fraction of AlN in the second AlN layer 11 is 1. The second AlN layer 11 contains at least AlN. The second AlN layer 11 is an underlayer.

[0022] Next, a first step is performed to grow an n-AlGaN layer 12 having a low AlN mole fraction region LC1, where the AlN mole fraction is lower than other regions, on the surface of the second AlN layer 11 (underlayer). Specifically, the n-AlGaN layer 12 is stacked on the surface of the second AlN layer 11 and crystal growth is performed. The thickness of the n-AlGaN layer 12 is 5 μm. First, the temperature of the AlN template substrate 10 is lowered to 1130°C. Once the predetermined temperature is reached, N2, TMGa (trimethylgallium), TMAl, and SiH4 (silane), a Si source acting as a donor, are supplied into the reactor so that the AlN mole fraction becomes 0.6. At this time, the V / III ratio is set to 800 to 1200, and the growth rate is kept low at 0.8 to 1.2 μm / h. The Si doping concentration in the n-AlGaN layer 12 is 3×10 18 cm -3 The supply flow rates of the raw materials are adjusted so that the molar fraction of AlN in the n-AlGaN layer 12 is smaller than that in the first AlN layer 10B and the second AlN layer 11. From the start to the end of the first step, the supply amounts of the raw materials to the reactor, and the temperature and pressure inside the reactor are constant.

[0023] Next, the light emitting layer 13 is deposited by crystal growth on the surface of the n-AlGaN layer 12. First, the first guide layer 13A is deposited by crystal growth. The thickness of the first guide layer 13A is 180 nm. First, the supply of TMGa, TMAl, and SiH4 into the reactor is stopped, and the temperature of the AlN template substrate 10 is lowered to 1100° C. Once the predetermined temperature is reached, TMGa and TMAl are supplied into the reactor so that the mole fraction of AlN becomes 0.5.

[0024] Next, the double quantum well active layer 13B is deposited on the surface of the first guide layer 13A and crystal grown. The double quantum well active layer 13B has an AlGaN well layer with an AlN molar fraction of 0.3 and an AlGaN barrier layer with an AlN molar fraction of 0.5 (not shown). The AlGaN well layer is 4 nm thick. The AlGaN barrier layer is 8 nm thick. The double quantum well active layer 13B is deposited and crystal grown with the temperature of the AlN template substrate 10 set to 1100°C, and then an AlGaN barrier layer is deposited and crystal grown under the same growth conditions as for the first guide layer 13A. This process is repeated twice to form the AlGaN / AlGaN double quantum well active layer 13B.

[0025] Next, TMGa and TMAl are supplied into the reactor so that the molar fraction of AlN becomes 0.5, and the second guide layer 13C is deposited and crystal grown, thus forming the light emitting layer 13. The second guide layer 13C has a thickness of 180 nm.

[0026] Then, the supply of TMGa and TMAl to the reactor is stopped to terminate crystal growth, and the temperature of the AlN template substrate 10 is lowered to room temperature while H and NH are flowed into the reactor. After the temperature of the AlN template substrate 10 has reached room temperature, the reactor is thoroughly purged, and the AlN template substrate 10 is removed from the reactor. In this way, the nitride semiconductor light-emitting device 1 having the layer structure shown in FIG. 1 is completed. The number of defects in the n-AlGaN layer 12 fabricated as described above was 5.8×10 8 / cm 2 It was.

[0027] As shown in Figure 2, the nitride semiconductor light-emitting device 1 removed from the reactor was found to have multiple tiny triangular regions Tr formed on the surface of the second AlN layer 11. It was also found that the n-AlGaN layer 12 had low AlN mole fraction regions LC1 (indicated by white dotted lines in Figure 2) formed adjacent to the vertices of the regions Tr, with the AlN mole fraction lower than that of the regions Tr. That is, the n-AlGaN layer 12 has a low AlN mole fraction region LC1 within itself, where the AlN mole fraction is lower than that of other regions. The low AlN mole fraction region LC1 was formed in the n-AlGaN layer 12 during the initial stage of the first step, when the supply amounts of raw materials into the reactor, the temperature, and the pressure within the reactor were constant.

[0028] Next, the rear surface of the nitride semiconductor light-emitting element 1 (i.e., the rear surface of the sapphire substrate 10A) is mirror-polished, and then a holding substrate 14 made of AlN is attached to the front surface of the nitride semiconductor light-emitting element 1 (i.e., the front surface of the second guide layer 13C) using epoxy resin (see FIG. 3). In FIG. 3, the orientation of the nitride semiconductor light-emitting element 1 is upside down compared to FIG. 1.

[0029] Then, a second step is performed in which the n-AlGaN layer 12 is peeled off from the second AlN layer 11 (underlying layer) along the low AlN mole fraction region LC1 by laser lift-off. Specifically, a laser beam with a wavelength of 257 nm and an energy density of 0.53 J / cm is applied from the back surface side of the nitride semiconductor light-emitting element 1 (i.e., the back surface side of the sapphire substrate 10A). 2 The laser light L is irradiated evenly over the entire rear surface.

[0030] Observation of the nitride semiconductor light-emitting device 1 after irradiation with laser light L using an electron microscope revealed that a crack C had occurred along the low AlN mole fraction region LC1, as shown in Fig. 4. In this state, an external force was applied to the sapphire substrate 10A in a direction to peel it off from the holding substrate 14. Then, as shown in Fig. 5, the sapphire substrate 10A was peeled off from the holding substrate 14 together with the first AlN layer 10B, the second AlN layer 11, and part of the n-AlGaN layer 12. In this way, the nitride semiconductor light-emitting device 1 separated into two pieces had the back surface side of the n-AlGaN layer 12 exposed on the holding substrate 14 side, and the n-AlGaN layer 12 also exposed on the sapphire substrate 10A side.

[0031] As shown in Fig. 6(A), multiple hexagonal pyramidal shapes Hp were observed on the back surface side of the exposed n-AlGaN layer 12. Furthermore, as shown in Fig. 6(B), multiple depressions D corresponding to the shapes Hp were observed in the n-AlGaN layer 12 exposed on the sapphire substrate 10A side.

[0032] Next, the effects of the above embodiment will be described.

[0033] The method for manufacturing a nitride semiconductor light-emitting device of the present invention includes a first step of growing an n-AlGaN layer 12 having a low AlN mole fraction region LC1, where the AlN mole fraction is lower than other regions, on the surface side of a second AlN layer 11 (underlayer), and a second step of performing laser lift-off to peel the n-AlGaN layer 12 from the second AlN layer 11. According to this configuration, by performing laser lift-off in the second step, the low AlN mole fraction region LC1 grown in the first step can be decomposed, and the n-AlGaN layer 12 can be successfully peeled off from the second AlN layer 11.

[0034] In the method for manufacturing a nitride semiconductor light-emitting device, the second AlN layer 11 is formed of AlN. With this configuration, when the second AlN layer 11 and the n-AlGaN layer 12 are grown in a stacked state, different types of layers can be produced by adjusting the supply of Al to the reactor.

[0035] <Example 2> 7, the nitride semiconductor light-emitting device 2 of Example 2 differs from the nitride semiconductor light-emitting device 1 of Example 1 in that a plurality of protrusions 11A are provided on the surface side of the second AlN layer 11, and in the configuration of the layers grown on the second AlN layer 11. Components identical to those in Example 1 are given reference numerals and detailed descriptions thereof will be omitted. Detailed descriptions of procedures identical to those in Example 1 will be omitted. In the nitride semiconductor light-emitting device 2 of Example 2, the procedure for growing the first AlN layer 10B and the second AlN layer 11 on the sapphire substrate 10A is the same as the procedure for fabricating the nitride semiconductor light-emitting device 1 of Example 1, and detailed descriptions thereof will be omitted.

[0036] [Convex part formation process] Prior to the first step, a convex portion forming step is performed to form multiple convex portions 11A on the surface of the second AlN layer 11 (underlayer). Specifically, a sputtering device is used to deposit a 420 nm SiO2 layer on the surface of the second AlN layer 11. Then, a resist is applied to the surface of the SiO2 layer to form a resist film, and a nanoimprinting device is used to form a fine pattern with a pitch of 1000 nm and a diameter of 300 nm on the resist film. The surface of the SiO2 layer is exposed outside the fine pattern. Then, an ICP device is used to dry-etch the exposed SiO2 layer with CF4 gas, and subsequently, buffered hydrofluoric acid is used to remove the SiO2 layer residue. Then, Cl2 gas is used to etch the surface side of the second AlN layer 11 to a depth of 500 nm, and the SiO2 layer and resist film used as a mask are removed with buffered hydrofluoric acid. 8(A) and 8(B), a plurality of protrusions 11A with a pitch of approximately 1000 nm, a diameter of approximately 270 nm, and a height of approximately 500 nm are formed on the surface side of the second AlN layer 11. In this manner, the protrusion forming step is carried out.

[0037] Next, the first step is performed. A u-AlGaN layer 112A is deposited on the surface of the second AlN layer 11 on which the protrusions 11A are formed, allowing crystal growth. The AlN template substrate 10 on which the protrusions 11A are formed is placed back into the reactor. The temperature of the AlN template substrate 10 is then raised to 1200°C. Once the predetermined temperature is reached, H2, TMGa, TMAl, and NH3 are supplied into the reactor so that the AlN mole fraction becomes 0.6. The pressure inside the reactor is 7 kPa. The thickness of the u-AlGaN layer 112A is 3 μm. By making the thickness of the u-AlGaN layer 112A 3 μm, the surface of the second AlN layer 11 on which the protrusions 11A are formed can be buried and planarized. The u-AlGaN layer 112A is not doped with impurities such as Si or Mg. However, the u-AlGaN layer 112A may be replaced with an n-AlGaN layer doped with Si or the like. Here, the thickness of the u-AlGaN layer 112A is the dimension from the base end of the protrusion 11A to the surface of the u-AlGaN layer 112A.

[0038] Next, the n-AlGaN layer 112B is stacked on the surface of the u-AlGaN layer 112A for crystal growth. Specifically, while H2, TMGa, TMAl, and NH3 are continuously supplied to the reactor, SiH4 is supplied to the reactor. The Si concentration in the n-AlGaN layer 112B is 6×10 18 cm -3 The supply flow rates of the raw materials are adjusted so that the thickness of the n-AlGaN layer 112B is 2 μm. The mole fraction of AlN in the n-AlGaN layer 112B is 0.6. In this manner, the first step is carried out. In the first step, the supply amounts of the raw materials into the reactor, as well as the temperature and pressure within the reactor, are constant from the start to the end of the growth of the u-AlGaN layer 112A.

[0039] Next, the light emitting layer 113 is deposited on the surface of the n-AlGaN layer 112B for crystal growth. Specifically, the temperature of the AlN template substrate 10 is lowered to 1050°C, and the pressure in the reactor is set to 30 kPa. Then, TMGa is switched to TEGa (triethylgallium). When the temperature of the AlN template substrate 10 reaches a predetermined temperature, a first guide layer with a thickness of 150 nm, a double quantum well active layer having two stacked pairs of a 4 nm thick well layer and an 8 nm thick barrier layer, and a second guide layer with a thickness of 150 nm are deposited in this order for crystal growth.

[0040] Next, an electron barrier layer 15 is deposited on the surface of the light-emitting layer 113 and crystals are grown. Specifically, TEGa is switched to TMGa. The thickness of the electron barrier layer 15 is 20 nm. Then, a p-AlGaN layer 16 and a p-GaN layer 17 are deposited on the surface of the electron barrier layer 15 and crystals are grown. The p-AlGaN layer 16 is formed with an AlN mole fraction that is graded in the thickness direction of the layer. In this way, the nitride semiconductor light-emitting element 2 having the layer structure shown in FIG. 7 is completed. The number of defects in the u-AlGaN layer 112A, n-AlGaN layer 112B, etc. fabricated as described above is 1.0×10 9 / cm 2 It was.

[0041] As shown in FIG. 9 , the nitride semiconductor light-emitting device 2 has a triangular first region LC2 formed between adjacent protrusions 11A of the second AlN layer 11. The second region LC3 is formed above the first region LC2, connecting to the two upper sides of the first region LC2 and expanding upward. The second region LC3 extends above the protrusion 11A. The second region LC3 wraps around above the protrusion 11A, covering the tip of the protrusion 11A. The AlN mole fractions of the first region LC2 and the second region LC3 are smaller than those of the upper portion of the u-AlGaN layer 112A and the n-AlGaN layer 112B. The AlN mole fraction in the second region LC3 is smaller than that of the first region LC2. In other words, the first region LC2 and the second region LC3 are low AlN mole fraction regions. In other words, the low AlN mole fraction region has a first region LC2 and a second region LC3 that overlap in the thickness direction and have different AlN mole fractions. The first region LC2 is located between the second region LC3 and the surface of the second AlN layer 11 (underlayer), and has a higher AlN mole fraction than the second region LC3. In Example 2, the low AlN mole fraction region is disposed between adjacent protrusions 11A. The low AlN mole fraction region of the u-AlGaN layer 112A is formed in the early stage of the first step while the supply amounts of raw materials into the reactor, and the temperature and pressure within the reactor are constant.

[0042] Next, the rear surface of the nitride semiconductor light-emitting element 2 (i.e., the rear surface of the sapphire substrate 10A) is mirror-polished, and then a holding substrate 14 made of AlN is attached to the front surface of the nitride semiconductor light-emitting element 2 (i.e., the front surface of the p-GaN layer 17) using epoxy resin (see FIG. 11). Then, a light beam with a wavelength of 257 nm and an energy density of 0.53 J / cm is applied from the rear surface side of the nitride semiconductor light-emitting element 2 (i.e., the rear surface side of the sapphire substrate 10A). 2 The laser light is irradiated evenly over the entire back surface.

[0043] Thereafter, when an external force was applied to the sapphire substrate 10A in a direction to peel it off from the holding substrate 14, the sapphire substrate 10A was peeled off from the holding substrate 14 (see FIG. 11). When the surfaces of the peeled and exposed sapphire substrate 10A and the holding substrate 14 were observed using an electron microscope, it was found that the protrusions 11A were attached to the holding substrate 14 side together with the u-AlGaN layer 112A (i.e., the protrusions 11A were peeled off from the second AlN layer 11) as shown in FIGS. 10(A) to 10(D) (see FIG. 11). It was also found that peeling occurred at the interface between the first region LC2 and the second region LC3 between adjacent protrusions 11A. In other words, it was found that the first region LC2 was attached to the second AlN layer 11, and the second region LC3 was attached to the u-AlGaN layer 112A on the holding substrate 14 side (see FIGS. 10(A) and 10(B)).

[0044] It is believed that the 257 nm wavelength laser light passes through the first region LC2 and is absorbed by the second region LC3, resulting in delamination at the interface between the first region LC2 and the second region LC3 without the application of external force. The delamination at the interface between the first region LC2 and the second region LC3 triggers the separation of the protrusions 11A from the second AlN layer 11, which in turn allows the u-AlGaN layer 112A to be separated from the sapphire substrate 10A without any damage.

[0045] In the method for manufacturing a nitride semiconductor light-emitting device of the present invention, a convexity forming step is performed before the first step, in which a plurality of convexities 11A are formed on the surface of the second AlN layer 11 (underlying layer). According to this configuration, the convexities 11A formed on the surface of the second AlN layer 11 act as triggers for peeling the u-AlGaN layer 112A from the second AlN layer 11, thereby enabling the u-AlGaN layer 112A to be more satisfactorily peeled off from the second AlN layer 11.

[0046] In the method for manufacturing a nitride semiconductor light-emitting device of the present invention, the low AlN mole fraction region has a first region LC2 and a second region LC3 that overlap in the thickness direction and have different AlN mole fractions. With this configuration, when laser lift-off is performed, delamination occurs at the interface between the first region LC2 and the second region LC3, making it easy to contain the delamination within the low AlN mole fraction region.

[0047] In the method for manufacturing a nitride semiconductor light-emitting device of the present invention, the first region LC2 is located between the second region LC3 and the surface of the second AlN layer 11, and has a higher AlN mole fraction than the second region LC3. According to this configuration, when laser lift-off is performed, the second region LC3 absorbs laser light and decomposes the second region LC3, which triggers delamination between the first region LC2 and the second region LC3, and the u-AlGaN layer 112A can be successfully delaminated from the second AlN layer 11.

[0048] Example 3 12, the nitride semiconductor light-emitting device 3 of Example 3 differs from the nitride semiconductor light-emitting device 2 of Example 2 in the height of the multiple protrusions 211A formed on the surface side of the second AlN layer 11 and the thickness of the u-AlGaN layer 212A. The same components as those of Example 2 are denoted by reference numerals and detailed descriptions thereof will be omitted. Detailed descriptions of the same procedures as those of Example 2 will be omitted.

[0049] A plurality of protrusions 211A having a pitch of 1000 nm, a diameter of 270 nm, and a height of 1000 nm are formed on the surface side of the second AlN layer 11. The thickness of the u-AlGaN layer 212A is 4 μm. By making the thickness of the u-AlGaN layer 212A 4 μm, the surface of the second AlN layer 11 on which the protrusions 211A are formed can be buried and flattened. The u-AlGaN layer 212A may be an n-AlGaN layer doped with Si or the like. Here, the thickness of the u-AlGaN layer 212A is the dimension from the base end of the protrusions 211A to the surface of the u-AlGaN layer 212A. The number of defects in the u-AlGaN layer 212A, the n-AlGaN layer 112B, etc. fabricated as described above is 3.4×10 8 / cm2 12, the back surface of the sapphire substrate 10A is located at the upper end, and the front surface of the p-GaN layer 17 is located at the lower end.

[0050] As shown in FIG. 13 , a space Vo (void) is formed around the base end of the protrusion 211A of the nitride semiconductor light-emitting element 3. It was found that a first region LC4 is formed on the outer peripheral surface of the protrusion 211A facing the space Vo, covering this outer peripheral surface. Furthermore, it was found that a second region LC5 is formed above the space Vo and extending vertically between adjacent protrusions 11A. That is, the first region LC4 is located between the second region LC5 and the surface of the second AlN layer 11. The second region LC5 is formed to extend above the protrusion 211A. The second region LC5 wraps around above the protrusion 211A, covering the tip of the protrusion 211A. It was found that the AlN mole fractions in the first region LC4 and the second region LC5 are smaller than the AlN mole fraction in the upper part of the u-AlGaN layer 212A. That is, the first region LC4 and the second region LC5 are low-AlN mole fraction regions. It was also found that the AlN molar fraction of the first region LC4 was lower than the AlN molar fraction of the second region LC5.

[0051] Next, the rear surface of the nitride semiconductor light-emitting element 3 (i.e., the rear surface of the sapphire substrate 10A) is mirror-polished, and then a holding substrate 14 made of AlN is attached to the front surface of the nitride semiconductor light-emitting element 3 (i.e., the front surface of the p-GaN layer 17) using epoxy resin. Then, a light beam having a wavelength of 257 nm and an energy density of 0.53 J / cm is applied from the rear surface side of the nitride semiconductor light-emitting element 3. 2The entire rear surface was uniformly irradiated with the laser light. Thereafter, an external force was applied to the sapphire substrate 10A in a direction to peel it off from the holding substrate 14, and the sapphire substrate 10A was peeled off from the holding substrate 14 together with the first AlN layer 10B and the second AlN layer 11. As shown in FIG. 14, it was found that the protrusions 211A were attached to the holding substrate 14 together with the u-AlGaN layer 212A (i.e., the protrusions 211A were peeled off from the second AlN layer 11). Furthermore, peeling occurred within the first region LC4 between adjacent protrusions 211A, and as a result, part of the first region LC4 was also attached to the holding substrate 14 together with the u-AlGaN layer 212A. In other words, peeling occurred between the first region LC4 and the second AlN layer 11 due to the laser lift-off.

[0052] It is believed that the 257 nm wavelength laser light is absorbed by the first region LC4, resulting in delamination within the first region LC4. The delamination within the first region LC4 triggers the separation of the protrusions 211A from the second AlN layer 11, which in turn allows the u-AlGaN layer 212A to be separated from the sapphire substrate 10A without any damage.

[0053] In the method for manufacturing a nitride semiconductor light-emitting device of the present invention, the first region LC4 is located between the second region LC5 and the surface of the second AlN layer 11, and has a lower AlN mole fraction than the second region LC5. According to this configuration, when laser lift-off is performed, the first region LC4 absorbs laser light and decomposes the first region LC4, which triggers delamination between the first region LC4 and the second AlN layer 11 (underlayer), peeling off the protrusions 211A from the second AlN layer 11 and successfully peeling off the u-AlGaN layer 212A.

[0054] The present invention is not limited to the first to third embodiments described above with reference to the drawings, and the following embodiments are also included within the technical scope of the present invention. (1) In Example 1, Si is added as an n-type impurity to form an n-AlGaN layer, but this is not limiting and n-type impurities such as Ge and Te may also be used. Furthermore, Mg, Zn, Be, Ca, Sr, Ba, etc. may also be added as p-type impurities to form a p-AlGaN layer. Alternatively, a u-AlGaN layer may be initially grown, followed by the growth of an n-AlGaN layer. (2) In Examples 1, 2, and 3, a sapphire substrate is used, but an AlN layer may be laminated on another substrate, such as an AlN substrate, through which the laser light used in laser lift-off (LLO) passes, and crystal growth may be performed. (3) In Examples 1, 2, and 3, the first AlN layer and the second AlN layer are used as the underlayer, but AlGaN may also be used as the underlayer. In other words, the underlayer may be formed of either AlGaN or AlN. (4) In Examples 1, 2, and 3, the underlayer includes an AlN layer formed by sputtering, but instead of sputtering, only an AlN layer grown by MO-VPE may be used.

[0055] 1, 2, 3...Nitride semiconductor light emitting device 10B...1st AlN layer (base layer) 11…Second AlN layer (base layer) 11A, 211A...Convex part 12...n-AlGaN layer (AlGaN layer with low AlN mole fraction region) 112A, 212A...u-AlGaN layer (AlGaN layer with low AlN mole fraction region) LC1: Low AlN mole fraction region LC2, LC4... Region 1 (low AlN mole fraction region) LC3, LC5...Second region (low AlN mole fraction region)

Claims

1. a first step of growing an AlGaN layer on a surface side of an underlayer, the AlGaN layer having a low AlN mole fraction region in which the AlN mole fraction is lower than that of other regions; a second step of performing laser lift-off to remove the AlGaN layer from the underlying layer; Equipped with a convex portion forming step of forming a plurality of convex portions on the surface of the underlayer before the first step is performed; In the second step, the protrusions are peeled off from the base layer together with the AlGaN layer, the low AlN mole fraction region has a first region and a second region that overlap in a thickness direction and have different AlN mole fractions; A method for manufacturing a nitride semiconductor light-emitting element, wherein the interface between the first region and the second region is formed between adjacent convex portions.

2. The method for manufacturing a nitride semiconductor light-emitting device according to claim 1 , wherein the underlayer is made of either AlGaN or AlN.

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