Manufacturing method of bonded wafer for micro LED

Abstract

To provide a method of manufacturing a junction-type wafer for AlGaInP based micro LEDs with reduced deterioration of manufacturing yield caused by cracking of micro LED elements in a laser-lift-off process.SOLUTION: A method of manufacturing a junction-type wafer for AlGaInP based micro LEDs comprises the steps of: forming an epithelial layer by stacking an AlGaInP based first clad layer, an active layer, and a second clad layer on a GaAs substrate through epithelial growth; growing a GaP window layer on the second clad layer; bonding the GaP window layer and a transparent substrate via a thermosetting joining member; removing the GaAs substrate; dividing the epithelial layer into micro LED elements; exposing the second clad layers or GaP window layers of the micro LED elements; forming electrodes; adhering the electrodes to a transfer substrate; and separating the micro LED elements from the transparent substrate by laser emission from the side of the transparent substrate, the thickness of the GaP window layer being 6 μm or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a bonded wafer for micro LEDs.

Background Art

[0002] In order to realize a display using micro light-emitting diodes (micro LEDs), a technique has been disclosed in which GaN-based LEDs are peeled off from a starting substrate using laser lift-off (LLO) technology, transferred to a mounting substrate, and then transferred to a driving substrate (Patent Document 1).

[0003] Also, there is a disclosure of a technique compatible with LLO of an upper surface two-electrode type LED (Patent Document 2), which relates to a GaN-based LED and has a very general film thickness structure. This is because the mechanical strength of the GaN-based LED is strong and there are few structural requirements in the LLO transfer process.

[0004] On the other hand, there is no disclosure of LLO technology using AlGaInP-based LEDs. This is because the starting substrate of the AlGaInP-based LED is GaAs, and LLO is fundamentally impossible with the starting substrate attached. However, LLO can be enabled by removing the starting substrate and transferring the epitaxial layer to a substrate on which LLO is possible.

[0005] Although not applying LLO technology, a technique for separating from a starting substrate by sacrificial layer etching has been disclosed as a transfer technique for AlGaInP-based LEDs (Patent Document 3). Also, there is a disclosure of a technique for removing the sacrificial layer and bonding to a support substrate via BCB (adhesive) (Patent Document 4), but it is not a structure suitable for LLO, and there is no disclosure of an AlGaInP-based LED structure suitable for LLO.

[0006] AlGaInP-based LEDs have lower mechanical strength than GaN-based LEDs. Therefore, when performing LLO transfer with an AlGaInP-based LED upper surface two-electrode structure, there is a problem that the LED breaks (is damaged) in the transfer process under the same conditions as GaN-based LEDs.

Prior Art Documents

Patent Document

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0008] The present invention has been made in view of the above problems, and an object thereof is to provide a method for manufacturing a bonded wafer for AlGaInP-based micro-LEDs that improves the yield reduction due to cracking of micro-LED elements during the LLO process.

Means for Solving the Problems

[0009] The present invention is made to achieve the above object. A process of epitaxially growing a first clad layer made of a first conductivity type of AlGaInP, a non-doped active layer of AlGaInP, and a second clad layer made of a second conductivity type of AlGaInP on a GaAs substrate to form an epitaxial layer; a process of growing a GaP window layer on the second clad layer; a process of bonding the GaP window layer and a transparent substrate, which is a bonded substrate transparent to visible light and ultraviolet light, via a thermosetting bonding member; a process of peeling the GaAs substrate; a process of separating the epitaxial layer into micro-LED elements that are square with a short side length of 50 μm or less; a process of exposing the second clad layer or the GaP window layer in a partial region of the micro-LED element; a process of forming a first electrode in contact with the first conductivity type layer and a second electrode in contact with the second conductivity type layer, and forming an ohmic contact by performing heat treatment; a process of bonding the first electrode and the second electrode to a transfer substrate via a silicone resin; and a process of irradiating a laser from the transparent substrate side and separating the transparent substrate and the micro-LED element by a laser lift-off process of sublimating the thermosetting bonding member in contact with the transparent substrate. In a method for manufacturing a bonded-type wafer for micro-LEDs, a method for manufacturing a bonded-type wafer for micro-LEDs is provided, characterized in that the thickness of the GaP window layer is 6 μm or more.

[0010] By setting the thickness of the GaP window layer to 6 μm or more in this way, even in the case of a minute AlGaInP-based micro-LED element that is square with a short side length of 50 μm or less, cracking can be suppressed during the laser lift-off process, and a reduction in yield can be improved.

[0011] At this time, it is preferable that the thermosetting bonding member is at least one of benzocyclobutene, silicone resin, epoxy resin, SOG, polyimide, and amorphous fluororesin.

[0012] With such a thermosetting bonding member, the laser lift-off process using an excimer laser can be surely performed.

[0013] Further, it is preferable that the transparent substrate is a sapphire substrate or a quartz substrate.

[0014] In this way, if the transparent substrate, which is the substrate to be joined, is made of sapphire or quartz, it is transparent to the excimer laser and has sufficient thermal strength, which is preferable.

[0015] In addition, in the step of separating the epitaxial layer into the micro LED elements, it is preferable that the method is by forming a pattern by photolithography and performing ICP etching using chlorine gas and argon gas.

[0016] According to such a method, element separation can be performed reliably and relatively easily.

[0017] Further, it is preferable that the transfer substrate is a quartz substrate.

[0018] In the method for manufacturing the bonded wafer for micro LEDs of the present invention, a quartz substrate can be suitably used as the transfer substrate.

Advantages of the Invention

[0019] In the method for manufacturing the bonded light-emitting element wafer of the present invention, by making the thickness of the GaP window layer a thick layer of 6 μm or more, even when manufacturing a minute micro LED element that is square with a short side length of 50 μm or less using a material with relatively low strength such as an AlGaInP-based material, it is possible to obtain a method for manufacturing a bonded wafer for AlGaInP-based micro LEDs that improves the yield reduction due to cracking of the micro LED elements during the LLO process.

Brief Description of the Drawings

[0020]

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Embodiments for Carrying Out the Invention

[0021] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0022] The present invention relates to a method for manufacturing a bonded wafer for micro-LEDs, comprising the steps of: epitaxially growing a first cladding layer made of an AlGaInP-based first conductivity type, a non-doped active layer made of AlGaInP, and a second cladding layer made of an AlGaInP-based second conductivity type on a GaAs substrate to form an epitaxial layer; growing a GaP window layer on the second cladding layer; bonding the GaP window layer and a transparent substrate, which is a bonded substrate transparent to visible light and ultraviolet light, via a thermosetting bonding member; peeling off the GaAs substrate; separating the epitaxial layer into micro-LED elements having a square shape with a short side length of 50 μm or less; exposing a part of the second cladding layer or the GaP window layer of the micro-LED element; forming a first electrode in contact with the first conductivity type layer and a second electrode in contact with the second conductivity type layer, and performing heat treatment to form an ohmic contact; bonding the first electrode and the second electrode to a transfer substrate via a silicone resin; and separating the transparent substrate and the micro-LED element by laser lift-off treatment in which a laser is irradiated from the transparent substrate side to sublime the thermosetting bonding member in contact with the transparent substrate. In this method, the thickness of the GaP window layer is 6 μm or more.

[0023] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0024] First, an AlGaInP-based light-emitting element structure is formed on a GaAs substrate. Therefore, as shown in FIG. 1, on a GaAs substrate 11 as a starting substrate, sequential epitaxial growth of a first cladding layer 13 made of an AlGaInP-based first conductivity type, a non-doped active layer 14 made of AlGaInP, and a second cladding layer 15 made of an AlGaInP-based second conductivity type is performed to form an epitaxial layer. Further, a GaP window layer 16 is grown on the second cladding layer 15. In this way, each layer is formed to produce an epitaxial wafer 20. More specifically, epitaxial growth of each layer can be performed as follows.

[0025] As shown in FIG. 1, an etch stop layer 12 is epitaxially grown on a first-conductivity-type GaAs substrate 11 which is a starting substrate. The etch stop layer 12 is formed, for example, by growing a first-conductivity-type GaAs buffer layer and then growing a first-conductivity-type Ga x In 1-x P(0.4 ≦ x ≦ 0.6) first etch stop layer by, for example, 0.1 μm and a first-conductivity-type GaAs second etch stop layer by, for example, 0.1 μm. Further, on the etch stop layer 12, for example, a first-conductivity-type (Al y Ga 1-y ) x In 1-x P(0.4 ≦ x ≦ 0.6, 0.6 ≦ y ≦ 1.0) first cladding layer 13 by, for example, 1.0 μm, a non-doped (Al y Ga 1-y ) x In 1-x P(0.4 ≦ x ≦ 0.6, 0 ≦ y ≦ 0.5) active layer 14, a second-conductivity-type (Al y Ga 1-y ) x In 1-x P(0.4 ≦ x ≦ 0.6, 0.6 ≦ y ≦ 1.0) second cladding layer 15 by, for example, 1.0 μm, a second-conductivity-type Ga x In 1-x P(0.5 ≦ x ≦ 1.0) intermediate layer (not shown) by, for example, 0.1 μm, and a second-conductivity-type GaP window layer 16 are sequentially grown to prepare an epitaxial wafer 20 having a light-emitting element structure 18 as an epitaxial functional layer. Here, from the first cladding layer 13 to the second cladding layer 15 is referred to as a double heterostructure (DH) portion (FIG. 1).

[0026] The above-described film thicknesses are merely examples, and are only parameters that should be changed according to the operating specifications of the device, and are not limited to the film thicknesses described here. Although the case where both the first cladding layer 13 and the second cladding layer 15 are 1.0 μm is exemplified, in a micro LED, it is smaller than a discrete LED having a large rated current density, and even if it is thinner than this film thickness, the function as a cladding layer is not impaired.

[0027] Since the electrode is formed in contact with the first cladding layer 13 as described below, the first cladding layer 13 preferably has a thickness of 0.6 μm or more in consideration of metal diffusion during ohmic contact formation. A thickness greater than this is preferable, and any thickness can be selected.

[0028] When the second conductivity type is p-type, since the effective mass of holes is large, the second cladding layer 15 functions in the same way as 1.0 μm even if it has a thickness of about 0.2 μm, for example. Therefore, it preferably has a thickness of 0.2 μm or more, and any thickness can be selected.

[0029] Also, each layer is not a single composition layer, but conceptually includes having a plurality of composition layers within the illustrated composition range. Also, the level of carrier concentration is not uniform in each layer, but conceptually includes having a plurality of levels within each layer.

[0030] The active layer 14 may be composed of a single composition, or may be a superlattice structure in which a plurality of barrier layers and active layers are alternately laminated, and both have similar functions and either can be selected.

[0031] In the present invention, the thickness of the GaP window layer 16 needs to be 6 μm or more. If it is thinner than this, it will cause a reduction in yield due to cracking of the micro-LED element in the LLO process described below. Also, the upper limit of the thickness of the GaP window layer 16 can be any film thickness as long as it is thinner than the short side length of the element isolation described below.

[0032] Next, as shown in FIG. 2, a GaP window layer 16 and a transparent substrate 30, which is a substrate to be joined and transparent to visible light and ultraviolet light, are joined via a thermosetting joining member 25. Specifically, this joining can be performed as follows. For example, benzocyclobutene (BCB) is spin-coated as the thermosetting joining member 25 on the epitaxial wafer 20, overlapped with the transparent substrate 30 (for example, a sapphire substrate), which is the substrate to be joined, and thermocompression bonded to produce an epitaxial joined substrate in which the epitaxial wafer and the transparent substrate 30 (sapphire substrate) are joined via BCB. When applying BCB by spin coating, the designed film thickness can be, for example, 0.6 μm.

[0033] Note that the transparent substrate 30, which is the substrate to be joined, is not limited to a sapphire substrate, and any material can be selected as long as it is transparent to visible light and ultraviolet light and flatness is ensured. In addition to sapphire, quartz can be selected.

[0034] Also, the thermosetting joining member 25 is not limited to BCB, and any material can be selected as long as it is suitable for the laser process described later, that is, a material that is transparent to visible light and absorbs ultraviolet light. In addition to BCB, silicone resin, epoxy resin, SOG (spin-on-glass), polyimide (PI), amorphous fluororesin such as CYTOP (registered trademark), etc. can be used.

[0035] Also, the thermosetting joining member 25 such as BCB can be patterned into an island shape, a line shape, or other shapes in addition to being applied in layers, and the same results can be obtained when performing the joining process. Also, the film thickness of the thermosetting joining member 25 is not limited to 0.6 μm, and the same effect can be obtained even if it is thinner than this thickness.

[0036] Next, as shown in FIG. 3, the GaAs substrate 11, which is the starting substrate, is peeled off. More specifically, it is as follows. The GaAs substrate can be peeled off and removed by wet etching with aqueous ammonia peroxide (a mixed solution of ammonia and hydrogen peroxide). As a result, among the etch stop layers 12, the GaInP first etch stop layer is exposed. Next, the etchant is switched to a hydrochloric acid-based one to selectively remove the GaInP first etch stop layer among the etch stop layers 12, exposing the GaAs second etch stop layer among the etch stop layers 12. Then, the etchant is switched to a sulfuric acid peroxide (a mixed solution of sulfuric acid and hydrogen peroxide)-based one to selectively remove the GaAs second etch stop layer, exposing the first cladding layer 13. By performing the above processes, an epitaxial junction substrate that retains only the DH layer and the GaP window layer can be fabricated.

[0037] Next, as shown in FIG. 4, the epitaxial layer is separated into micro-LED elements that are square with a short side length of 50 μm or less. Also, a part of the second cladding layer 15 or the GaP window layer 16 in the micro-LED element is exposed. This element separation process is preferably performed by forming a pattern by photolithography and performing ICP (Inductively Coupled Plasma) etching using chlorine gas and argon gas (element separation groove 47 in FIG. 4). The ICP process can be performed twice, namely, a process of exposing the BCB layer (thermosetting joint member 25) and a process of exposing the second cladding layer 15 or the GaP window layer 16.

[0038] The size of the device isolation here can be, for example, 25 μm × 50 μm, but this is merely an example, and the present invention shows remarkable effects on a minute micro-LED device that is square with a short side length of 50 μm or less. Also, the thickness of the GaP window layer 16 is preferably equal to or less than the short side length of the device isolation (when the size of the micro-LED device by the above device isolation is 25 μm × 50 μm, it is 25 μm or less). The reason is that although the LLO process itself is possible even if the GaP window layer 16 has a thickness exceeding 25 μm, when the thickness of the GaP window layer 16 is greater than the short side length, the micro-LED device is likely to fall after LLO, and even if the fracture yield of the micro-LED device is improved, there is a risk that the transfer yield will decrease due to the micro-LED device falling. Therefore, it is preferable to keep the height of the GaP window layer 16 equal to or less than the short side length.

[0039] In FIG. 4, the case where the second cladding layer 15 is exposed is illustrated, but it is not limited to the case where the second cladding layer 15 is exposed. As long as the active layer 14 is separated at least minimally, the same effect can be obtained even when the GaP window layer 16 is exposed instead of the second cladding layer 15 being exposed.

[0040] After the device isolation process shown in FIG. 4, as shown in FIG. 5, a protective film 52 can be formed as an end face treatment. SiO2 can be used as the protective film 52. Also, the protective film 52 is not limited to SiO2, and any material can be selected as long as it can protect the end face and has insulating properties. SiNx, titanium oxide, magnesium oxide, etc. can also be selected.

[0041] After forming the protective film 52, as shown in FIG. 6, a first electrode 54 in contact with the first conductive type layer and a second electrode 56 in contact with the second conductive type layer are formed, and heat treatment is performed to form an ohmic contact. For example, when the first conductive type is designed as n-type and the second conductive type is designed as p-type, a metal containing Au and Si can be used for the electrode in contact with the n-type layer, and a metal containing Au and Be can be used for the electrode in contact with the p-type layer.

[0042] The n-type electrode is not limited to metals such as Au and Si, and the same results can be obtained by using a metal containing Au and Ge. Also, the p-type electrode is not limited to metals such as Au and Be, and the same results can be obtained by using a metal containing Au and Zn.

[0043] After forming the ohmic contact, as shown in FIG. 7, the first electrode 54 and the second electrode 56 are adhered to the transfer substrate 70 via the silicone resin 65. A quartz substrate is suitable as the transfer substrate 70. For example, as shown in FIG. 7, a transfer substrate 70 on which a silicone resin 65 is applied to form a convex pattern is used, the transfer substrate 70 and the ohmic electrodes (the first electrode 54 and the second electrode 56) are opposed to each other, pressure is applied, and the ohmic electrode portions (the first electrode 54 and the second electrode 56) can be adhered to the silicone resin 65.

[0044] Next, as shown in FIG. 8, a laser (illustrated by six single arrows in FIG. 7) is irradiated from the transparent substrate 30 side, and the transparent substrate 30 and the micro-LED element are separated by a laser lift-off process that sublimates the thermosetting bonding member 25 in contact with the transparent substrate 30, thereby manufacturing a bonded wafer for micro-LEDs (FIG. 9). In this way, from the transparent substrate 30 side such as a sapphire substrate, for example, an excimer laser is irradiated, and the transparent substrate 30 and the micro-LED element are separated by a laser lift-off (LLO) process that sublimates the layer of the thermosetting bonding member 25 such as the BCB layer in contact with the transparent substrate 30 side.

[0045] After separating the micro-LED element from the transparent substrate 30 such as a sapphire substrate, as shown in FIG. 10, the thermosetting bonding member 25 such as BCB remaining on the surface of the micro-LED element can be removed by ashing or plasma etching.

Examples

[0046] Hereinafter, the present invention will be described in detail with reference to examples and comparative examples, but these do not limit the present invention.

[0047] (Examples and Comparative Examples) First, as shown in FIG. 1, after an n-type GaAs buffer layer is laminated on an n-type (first conductivity type) GaAs substrate 11 which is a starting substrate, an n-type GaInP first etch stop layer with a thickness of 0.1 μm and an n-type GaAs second etch stop layer with a thickness of 0.1 μm are epitaxially grown to form an etch stop layer 12. Further, an n-type (Al y Ga 1-y ) x In 1-x P (0.4 ≦ x ≦ 0.6, 0.6 ≦ y ≦ 1.0) first cladding layer 13 with a thickness of 1.0 μm, an undoped (Al y Ga 1-y ) x In 1-x P (0.4 ≦ x ≦ 0.6, 0 ≦ y ≦ 0.5) active layer 14, a p-type (Al y Ga 1-y ) x In 1-x P (0.4 ≦ x ≦ 0.6, 0.6 ≦ y ≦ 1.0) second cladding layer 15 with a thickness of 1.0 μm, a p-type Ga x In 1-x P (0.5 ≦ x ≦ 1.0) intermediate layer (not shown) with a thickness of 0.1 μm, and a p-type GaP window layer 16 are sequentially grown to prepare an epitaxial wafer 20 having a light-emitting element structure 18 as an epitaxial functional layer (FIG. 1). Here, the thickness of the GaP window layer 16 was changed in the range of 2 to 5 μm (comparative example) and 6 to 15 μm (example).

[0048] Next, as shown in FIG. 2, benzocyclobutene (BCB) is spin-coated on the epitaxial wafer 20 (on the light-emitting element structure 18) as a thermosetting bonding member 25, and is superposed facing a sapphire wafer which is a transparent substrate 30, and thermocompression bonding is performed to bond the epitaxial wafer and the sapphire substrate via BCB. When applying BCB by spin coating, the designed film thickness was 0.6 μm.

[0049] Next, as shown in FIG. 3, the GaAs starting substrate 11 and the etch stop layer 12 which are starting substrates are removed by wet etching to fabricate an epitaxial bonding substrate.

[0050] Next, as shown in FIG. 4, a pattern was formed by photolithography, and element isolation processing of 50×100 μm was performed by ICP using chlorine gas and argon gas (element isolation groove 47). The ICP processing was performed twice, once to expose the BCB layer 25 and once to expose the second cladding layer 15.

[0051] After the element isolation processing, as shown in FIG. 5, a SiO2 protective film 52 was formed as an end face treatment.

[0052] After the formation of the protective film 52, as shown in FIG. 6, a first electrode 54 and a second electrode 56 in contact with the n-type layer or the p-type layer, respectively, were formed, and heat treatment was performed to form an ohmic contact.

[0053] After the formation of the ohmic contact, as shown in FIG. 7, silicone resin 65 was applied, and a transfer substrate 70 made of quartz having a convex pattern formed thereon was opposed to the ohmic electrodes (first electrode 54, second electrode 56), and pressure was applied to adhere the ohmic electrode portions (first electrode 54, second electrode 56) to the silicone resin 65.

[0054] Next, as shown in FIG. 8, an excimer laser was irradiated from the side of the transparent substrate 30 made of sapphire, and the sapphire substrate and the micro LED dice were separated by laser lift-off (LLO) processing for sublimating the BCB layer portion in contact with the sapphire substrate (FIG. 9). Further, as shown in FIG. 10, the BCB was removed.

[0055] FIG. 11 shows the results of examining the yield of each wafer with different thicknesses of the GaP window layer 16. As shown in FIG. 11, when the thickness of the GaP window layer 16 was 4 μm or less (comparative example), all the micro LED elements were cracked and the yield was 0. When the thickness of the GaP window layer 16 was 5 μm (comparative example), the yield rate improved but was insufficient. When the thickness of the GaP window layer 16 was 6 μm (example), the yield rate was 80% or more, and when the thickness of the GaP window layer 16 was 8 μm or more (example), there were no cracks and the yield was 100%.

[0056] This specification includes the following aspects. [1]: A step of epitaxially growing a first cladding layer made of an AlGaInP-based first conductivity type, a non-doped active layer made of AlGaInP, and a second cladding layer made of an AlGaInP-based second conductivity type on a GaAs substrate to form an epitaxial layer; A step of growing a GaP window layer on the second cladding layer; A step of bonding the GaP window layer and a transparent substrate, which is a joined substrate transparent to visible light and ultraviolet light, via a thermosetting bonding member; A step of peeling off the GaAs substrate; A step of separating the epitaxial layer into micro-LED elements in a square shape with a short side length of 50 μm or less; A step of exposing the second cladding layer or the GaP window layer in a partial region of the micro-LED element; A step of forming a first electrode in contact with the first conductivity type layer and a second electrode in contact with the second conductivity type layer, and performing heat treatment to form an ohmic contact; A step of bonding the first electrode and the second electrode to a transfer substrate via a silicone resin; In a method for manufacturing a bonded wafer for micro-LEDs by separating the transparent substrate and the micro-LED element by laser lift-off treatment in which a laser is irradiated from the transparent substrate side to sublime the thermosetting bonding member in contact with the transparent substrate, A method for manufacturing a bonded wafer for micro-LEDs, characterized in that the thickness of the GaP window layer is 6 μm or more. [2]: The method for manufacturing a bonded wafer for micro-LEDs according to [1] above, wherein the thermosetting bonding member is at least one of benzocyclobutene, silicone resin, epoxy resin, SOG, polyimide, and amorphous fluororesin. [3]: The method for manufacturing a bonded wafer for micro-LEDs according to [1] or [2] above, wherein the transparent substrate is a sapphire substrate or a quartz substrate. [4]: The method in the step of separating the epitaxial layer into the micro-LED elements is the method according to [1], [2], or [3] above, which forms a pattern by photolithography and uses ICP etching with chlorine gas and argon gas, for manufacturing a bonded wafer for micro-LEDs. [5]: The method for manufacturing a bonded wafer for micro-LEDs according to [1], [2], [3], or [4] above, wherein the transfer substrate is a quartz substrate.

[0057] Note that the present invention is not limited to the above embodiments. The above embodiments are examples, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same operational effects is included in the technical scope of the present invention.

Explanation of Reference Numerals

[0058] 11…GaAs substrate, 12…etch stop layer, 13…first cladding layer, 14…active layer, 15…second cladding layer, 16…GaP window layer, 18…light-emitting element structure, 20…epitaxial wafer, 25…thermosetting bonding member, 30…transparent substrate, 47…element isolation groove, 52…protective film, 54…first electrode, 56…second electrode, 65…silicone resin, 70…transfer substrate.

Claims

1. A step of epitaxially growing a first cladding layer made of a first conductivity type of AlGaInP, a non-doped active layer of AlGaInP, and a second cladding layer made of a second conductivity type of AlGaInP on a GaAs substrate to form an epitaxial layer; A step of growing a GaP window layer on the second cladding layer; A step of bonding the GaP window layer and a transparent substrate, which is a bonding substrate transparent to visible light and ultraviolet light, via a thermosetting bonding member; A step of peeling the GaAs substrate; A step of separating the epitaxial layer into micro-LED elements that are square with a short side length of 50 μm or less; A step of exposing the second cladding layer or the GaP window layer in a partial region of the micro-LED element; A step of forming a first electrode in contact with the first conductivity type layer and a second electrode in contact with the second conductivity type layer, and forming an ohmic contact by performing a heat treatment; A step of bonding the first electrode and the second electrode to a transfer substrate via a silicone resin; In a method for manufacturing a bonded wafer for micro-LEDs by separating the transparent substrate and the micro-LED element by laser lift-off processing in which a laser is irradiated from the transparent substrate side to sublime the thermosetting bonding member in contact with the transparent substrate, A method for manufacturing a bonded wafer for micro-LEDs, characterized in that the thickness of the GaP window layer is 6 μm or more.

2. The method for manufacturing a bonded wafer for micro-LEDs according to claim 1, characterized in that the thermosetting bonding member is at least one of benzocyclobutene, silicone resin, epoxy resin, SOG, polyimide, and amorphous fluororesin.

3. The method for manufacturing a bonded wafer for micro-LEDs according to claim 1 or claim 2, characterized in that the transparent substrate is a sapphire substrate or a quartz substrate.

4. The method for manufacturing a bonded wafer for micro-LEDs according to claim 1 or claim 2, characterized in that the method in the step of separating the epitaxial layer into the micro-LED elements forms a pattern by photolithography and is by ICP etching using chlorine gas and argon gas.

5. The method for manufacturing a bonded wafer for micro-LEDs according to claim 1 or claim 2, characterized in that the transfer substrate is a quartz substrate.

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