Method for manufacturing bonded wafer for micro-LED

Abstract

The present invention is a method for manufacturing a junction-type wafer for a micro LED, the method comprising: a step for manufacturing a junction-type wafer for a micro LED by separating a transparent substrate from a micro LED element by irradiating a laser beam from the transparent substrate side through the following steps: epitaxially growing an AlGaInP-based first cladding layer, an active layer, and a second cladding layer on a GaAs substrate to form an epitaxial layer; a step for growing a GaP window layer on the second cladding layer; a step for bonding the GaP window layer and the transparent substrate via a thermosetting bonding member; a step for peeling off the GaAs substrate; a step for separating the epitaxial layer into micro LED elements; a step for exposing the second cladding layer or the GaP window layer of the micro LED element; a step for forming an electrode; and a step for bonding the electrode to the transfer substrate, in which the thickness of the GaP window layer is set to 6 [mu] m or more. As a result, it is possible to provide a method for manufacturing a junction-type wafer for an AlGaInP-based micro LED in which a reduction in yield due to breakage of a micro LED element during an LLO step is improved.

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 based on micro light-emitting diodes (Micro LEDs), a technique has been disclosed in which a GaN-based LED is peeled off from a starting substrate using a laser lift-off (LLO) technique and transferred to a mounting substrate and then to a driving substrate (Patent Document 1).

[0003] In addition, a technique suitable for LLO of an upper surface double electrode type LED has been disclosed (Patent Document 2), but it is a technique related to a GaN-based LED and has a very common film thickness structure. This is because the GaN-based LED has strong mechanical strength and fewer structural requirements in the LLO transfer process.

[0004] On the other hand, an LLO technique using an AlGaInP-based LED has not been disclosed. This is because the starting substrate of the AlGaInP-based LED is GaAs, and in principle, LLO (laser lift-off) cannot be performed in a state where the starting substrate is attached. However, as long as the starting substrate is removed and the epitaxial layer is transferred to a substrate capable of performing LLO, LLO (laser lift-off) can be performed.

[0005] Although not applying the LLO technique, a technique for separating from a starting substrate by sacrificial layer etching has been disclosed as a transfer technique for an AlGaInP-based LED (Patent Document 3). In addition, there is 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 use, and there is still no disclosure of a structure of an AlGaInP-based LED suitable for LLO.

[0006] The mechanical strength of the AlGaInP-based LED is lower than that of the GaN-based LED. Therefore, when performing LLO transfer in the upper surface double electrode structure of the AlGaInP-based LED, there is a problem that the LED is broken (destroyed) in the transfer process under the same conditions as the GaN-based LED.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-521181

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2015-2324

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 2021-153186

[0012] Patent Document 4: Japanese Patent Application Laid-Open No. 2006-32952 Summary of the Invention

[0013] (1) Technical Problem to be Solved

[0014] 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, which improves the yield reduction caused by the breakage of micro LED elements during the LLO process.

[0015] (2) Technical Solution

[0016] The present invention has been completed to achieve the above object, and the present invention provides a method for manufacturing a bonded wafer for micro LEDs, characterized in that, through the following steps and by irradiating a laser from the transparent substrate side to sublime the thermosetting bonding member in contact with the transparent substrate, the transparent substrate and the micro LED element are separated to manufacture a bonded wafer for micro LEDs, and an epitaxial layer is formed by epitaxially growing a first cladding layer made of AlGaInP-based first conductivity type, an undoped active layer made of AlGaInP-based, and a second cladding layer made of AlGaInP-based second conductivity type on a GaAs substrate; a GaP window layer is grown on the second cladding layer; a step of bonding the GaP window layer to a transparent substrate as a substrate to be bonded transparent to visible light and ultraviolet light via a thermosetting member; a step of peeling off the GaAs substrate; a step of separating the epitaxial layer into square micro LED elements having 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 layer of the first conductivity type and a second electrode in contact with the layer of the second conductivity type, and performing heat treatment to form an ohmic contact; and a step of bonding the first electrode and the second electrode to a transfer substrate via a silicone resin. In this method for manufacturing a bonded wafer for micro LEDs, the thickness of the GaP window layer is set to 6 μm or more.

[0017] By setting the thickness of the GaP window layer to 6 μm or more in this way, even for such small AlGaInP-based micro LED elements with a short side length of 50 μm or less, breakage can be suppressed during the laser lift-off process, thereby improving the yield reduction.

[0018] At this time, it is preferable to set the thermosetting bonding member to at least any one of benzocyclobutene, silicone resin, epoxy resin, SOG, polyimide, and amorphous fluororesin.

[0019] In the case of such a thermosetting type bonding member, laser lift-off processing based on excimer laser can be performed more reliably.

[0020] In addition, it is preferable that the transparent substrate is a sapphire substrate or a quartz substrate.

[0021] Thus, if the transparent substrate as the substrate to be bonded is a substrate made of sapphire or quartz, it is transparent to excimer laser and has sufficient thermal strength, so it is suitable.

[0022] In addition, it is preferable that the method in the process of separating the epitaxial layer into the micro LED elements is a method performed by ICP etching using chlorine gas and argon gas after forming a pattern by photolithography.

[0023] In the case of such a method, element separation can be performed more easily and reliably.

[0024] In addition, it is preferable that the transfer substrate is a quartz substrate.

[0025] In the method for manufacturing a bonded type wafer for micro LEDs of the present invention, a quartz substrate can be applied as the transfer substrate.

[0026] (III) Beneficial effects

[0027] If it is the method for manufacturing a bonded type light-emitting element wafer of the present invention, by setting the thickness of the GaP window layer to a layer as thick as 6 μm or more, even when manufacturing a micro LED element as small as a 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 can be a method for manufacturing a bonded type wafer for AlGaInP-based micro LEDs that improves the yield reduction caused by the cracking of the micro LED elements during the LLO process. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 FIG. is a cross-sectional schematic view showing a part of the method for manufacturing a bonded type wafer for micro LEDs of the present invention.

[0029] Figure 2 FIG. is a cross-sectional schematic view showing another part of the method for manufacturing a bonded type wafer for micro LEDs of the present invention.

[0030] Figure 3 FIG. is a cross-sectional schematic view showing another part of the method for manufacturing a bonded type wafer for micro LEDs of the present invention.

[0031] Figure 4 FIG. is a cross-sectional schematic view showing another part of the method for manufacturing a bonded type wafer for micro LEDs of the present invention.

[0032] Figure 5A cross-sectional schematic view showing another part of the method for manufacturing a bonded wafer for micro LEDs of the present invention.

[0033] Figure 6 A cross-sectional schematic view showing another part of the method for manufacturing a bonded wafer for micro LEDs of the present invention.

[0034] Figure 7 A cross-sectional schematic view showing another part of the method for manufacturing a bonded wafer for micro LEDs of the present invention.

[0035] Figure 8 A cross-sectional schematic view showing another part of the method for manufacturing a bonded wafer for micro LEDs of the present invention.

[0036] Figure 9 A cross-sectional schematic view showing another part of the method for manufacturing a bonded wafer for micro LEDs of the present invention.

[0037] Figure 10 A cross-sectional schematic view showing another part of the method for manufacturing a bonded wafer for micro LEDs of the present invention.

[0038] Figure 11 A graph showing the results of the yields of wafers with different thicknesses of the GaP window layer in the bonded wafers for micro LEDs manufactured in the examples and comparative examples. Detailed Description of the Invention

[0039] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0040] The present invention relates to a method for manufacturing a bonded wafer for micro LEDs. The method is characterized in that, through the following steps and a laser lift-off process in which a thermosetting bonding member in contact with the transparent substrate is sublimated by irradiating laser from the transparent substrate side, the transparent substrate is separated from the micro LED element, thereby manufacturing a bonded wafer for micro LEDs. The steps include: epitaxially growing a first cladding layer made of AlGaInP of a first conductivity type, an undoped active layer made of AlGaInP, and a second cladding layer made of AlGaInP of a 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 to a transparent substrate, which is a substrate to be bonded and transparent to visible light and ultraviolet light, via a thermosetting bonding member; peeling off the GaAs substrate; separating the epitaxial layer into square micro LED elements 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 layer of the first conductivity type and a second electrode in contact with the layer of the second conductivity type, and performing heat treatment to form an ohmic contact; and bonding the first electrode and the second electrode to a transfer substrate via silicone resin. In this method for manufacturing a bonded wafer for micro LEDs, the thickness of the GaP window layer is set to 6 μm or more.

[0041] Hereinafter, the solution of the present invention will be described with reference to the accompanying drawings.

[0042] First, a light-emitting element structure made of AlGaInP is formed on a GaAs substrate. Thus, as Figure 1 shown, on a GaAs substrate 11 as a starting substrate, epitaxial growth of a first cladding layer 13 made of AlGaInP of a first conductivity type, an undoped active layer 14 made of AlGaInP, and a second cladding layer 15 made of AlGaInP of a second conductivity type is sequentially performed to form an epitaxial layer. In addition, a GaP window layer 16 is grown on the second cladding layer 15. Thus, each layer is formed to fabricate an epitaxial wafer 20. More specifically, the epitaxial growth of each layer is performed in the following manner.

[0043] As Figure 1 shown, an etch stop layer 12 is epitaxially grown on a first-conductivity-type GaAs substrate 11 as a starting substrate. The etch stop layer 12 can be formed, for example, by stacking a first-conductivity-type GaAs buffer layer and then making the first-conductivity-type Ga x In 1-xP(0.4 ≤ x ≤ 0.6) First etch stop layer is grown, for example, by 0.1 μm, and a second etch stop layer of GaAs of the first conductivity type is grown, for example, by 0.1 μm. Further, on the etch stop layer 12, 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, 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 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, a second conductivity type Ga x In 1-x P(0.5 ≤ x ≤ 1.0) intermediate layer (not shown), a second conductivity type GaP window layer 16 are grown in sequence, thereby preparing an epitaxial wafer 20 having a light-emitting element structure 18 as an epitaxial functional layer formed by the above-described sequential growth. Among them, the portion from the first cladding layer 13 to the second cladding layer 15 is referred to as a double heterostructure (DH) portion ( Figure 1 )

[0044] The film thicknesses are only examples, and the film thickness is only a parameter that should be changed according to the operating specifications of the device, and thus is not limited to the film thicknesses described herein. Although the case where both the first cladding layer 13 and the second cladding layer 15 are 1.0 μm is illustrated, in a micro LED, even if the rated current density is smaller than that of a large-sized discrete LED and the film thickness is thinner, the function as a cladding layer is not impaired.

[0045] As described later, an electrode is formed in contact with the first cladding layer 13. Considering metal diffusion during the formation of an ohmic contact, the first cladding layer 13 preferably has a thickness of 0.6 μm or more. A thickness of 0.6 μm or more is preferred, and any thickness can be selected.

[0046] When the second conductivity type is p-type, the effective mass of holes is large. Therefore, even if the second cladding layer 15 has a thickness of, for example, about 0.2 μm, it functions in the same manner as 1.0 μm. Therefore, a thickness of 0.2 μm or more is preferred, and any such thickness can be selected.

[0047] In addition, each layer is not a single constituent layer, and it includes the concept of having multiple constituent layers within the constituents shown in the examples. In addition, the level of carrier concentration is not uniform in each layer, including the concept of having multiple levels within each layer.

[0048] The active layer 14 can be composed of a single constituent. In addition, even if it is a superlattice structure in which multiple barrier layers and the active layer are alternately stacked and have a similar function, either of the two can be arbitrarily selected.

[0049] In the present invention, the thickness of the GaP window layer 16 needs to be 6 μm or more. When it is thinner than this thickness, it will cause a decrease in yield due to the breakage of the micro-LED element in the LLO process described later. In addition, 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 separation described later.

[0050] Next, as Figure 2 shown, the GaP window layer 16 is bonded to the transparent substrate 30, which is a substrate to be bonded and transparent to visible light and ultraviolet light, via the thermosetting bonding member 25. Specifically, this bonding can be carried out in the following manner. For example, benzocyclobutene (BCB) as the thermosetting bonding member 25 is spin-coated on the epitaxial wafer 20, and it is opposed to and overlapped with the transparent substrate 30 (e.g., sapphire substrate) as the substrate to be bonded, and an epitaxial bonding substrate in which the epitaxial wafer and the transparent substrate 30 (sapphire substrate) are bonded via the BCB is formed by thermocompression bonding. When BCB is coated by spin coating, the designed film thickness can be set to 0.6 μm, for example.

[0051] In addition, the transparent substrate 30 as the substrate to be bonded is not limited to the sapphire substrate, and any material can be selected as long as it is transparent to visible light and ultraviolet light and can ensure flatness. In addition to sapphire, quartz can also be selected.

[0052] In addition, the thermosetting bonding member 25 is not limited to BCB, and any material can be selected as long as it is a material suitable for the laser process described later, that is, a material that is transparent to visible light and can absorb 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 also be used.

[0053] In addition, for the thermosetting bonding member 25 such as BCB, the same result can be obtained by bonding it in a pattern such as isolated island shape or linear shape or other shapes in addition to coating it in a layer shape. In addition, the film thickness of the thermosetting bonding member 25 is not limited to 0.6 μm, and the same effect can be obtained as long as it is thicker than this thickness even if it is thinner.

[0054] Next, as Figure 3 shown, the GaAs substrate 11 serving as the starting substrate is peeled off. More specifically, as described below. The GaAs substrate can be removed by wet etching using ammonia-peroxide water (a mixed solution of ammonia and hydrogen peroxide). Thereby, the GaInP first etch stop layer in the etch stop layer 12 is exposed. Next, by switching the etchant to a hydrochloric acid-based one, the GaInP first etch stop layer in the etch stop layer 12 is selectively removed, and the GaAs second etch stop layer in the etch stop layer 12 is exposed. Then, by switching the etchant to a sulfuric acid-peroxide water (a mixed solution of sulfuric acid and hydrogen peroxide)-based one, the GaAs second etch stop layer is selectively removed, and the first cladding layer 13 is exposed. By performing the above processing, an epitaxial bonded substrate having only the DH layer and the GaP window layer retained can be fabricated.

[0055] Next, as Figure 4 shown, the epitaxial layer is separated into square micro-LED elements with a short side length of 50 μm or less. In addition, a part of the second cladding layer 15 or the GaP window layer 16 of the micro-LED element is exposed. This element separation process is preferably performed by forming a pattern using photolithography and ICP (Inductively Coupled Plasma) etching using chlorine and argon (the element separation groove 47 in Figure 4 ). The ICP process can perform two processes of exposing the BCB layer (the thermosetting bonding member 25) and the process of exposing the second cladding layer 15 or the GaP window layer 16.

[0056] The size of the element separation here can be set to, for example, 25 μm × 50 μm, but this is only an illustration, and the present invention shows a remarkable effect on square micro-LED elements with a short side length of 50 μm or less. In addition, it is preferable that the thickness of the GaP window layer 16 is set to be equal to or less than the short side length of the element separation (when the size of the micro-LED element separated by the above element separation is 25 μm × 50 μm, it is 25 μm or less). The reason is that even if the GaP window layer 16 has a thickness greater than 25 μm, the LLO process itself is feasible, but when the thickness of the GaP window layer 16 is thicker than the short side length, after LLO, the micro-LED element is likely to collapse. Even if the yield due to the breakage of the micro-LED element is improved, there is still a possibility that the transfer yield will decrease due to the collapse of the micro-LED element. Therefore, the height of the GaP window layer 16 is preferably set to be equal to or less than the short side length in advance.

[0057] In Figure 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. It is sufficient that at least the active layer 14 is separated, and the same effect can be obtained in the case where the GaP window layer 16 is exposed instead of the second cladding layer 15.

[0058] After the components shown in Figure 4 are separated and processed, as Figure 5 shown, a protective film 52 can be formed as an end face treatment. As the protective film 52, SiO 2 can be used. In addition, the protective film 52 is not limited to SiO 2 . Any material can be selected as long as it can protect the end face and has insulation properties. SiNx, titanium oxide, magnesium oxide, etc. can also be selected.

[0059] After forming the protective film 52, as Figure 6 shown, 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 an ohmic contact is formed by performing heat treatment. For example, the first conductive type can be designed as n-type and the second conductive type can be designed as p-type. The electrode in contact with the n-type layer uses a metal containing Au and Si, and the electrode in contact with the p-type layer uses a metal containing Au and Be.

[0060] As the n-type electrode, it is not limited to the metal of Au and Si, and the same result can be obtained by using a metal containing Au and Ge. In addition, as the p-type electrode, it is not limited to the metal of Au and Be, and the same result can be obtained by using a metal containing Au and Zn.

[0061] After forming the ohmic contact, as Figure 7 shown, the first electrode 54 and the second electrode 56 are bonded to the transfer substrate 70 via a silicone resin 65. As the transfer substrate 70, a quartz substrate is suitable. For example, as Figure 7 shown, a substrate with a raised pattern formed by coating the transfer substrate 70 with the silicone resin 65 is used. The transfer substrate 70 is opposed to the ohmic electrodes (the first electrode 54 and the second electrode 56) and pressure is applied, so that the ohmic electrode portions (the first electrode 54 and the second electrode 56) can adhere to the silicone resin 65.

[0062] Next, as Figure 8 shown, a laser lift-off process is performed by irradiating a laser ( Figure 7 shown as six half-arrowheads in Figure 9 ) from the side of the transparent substrate 30 to sublime the thermosetting bonding member 25 in contact with the transparent substrate 30, separating the transparent substrate 30 from the micro-LED element, thereby manufacturing a bonded wafer for micro-LEDs (

[0063] After separating the micro-LED element from a transparent substrate 30 such as a sapphire substrate, as Figure 10 shown, it is possible to remove thermosetting bonding members 25 such as BCB remaining on the surface of the micro-LED element by ashing or plasma etching.

[0064] Example

[0065] Hereinafter, examples and comparative examples will be given to describe the present invention in detail. These examples and comparative examples do not limit the present invention.

[0066] (Examples and Comparative Examples)

[0067] First, as Figure 1 shown, on an n-type (first conductivity type) GaAs substrate 11 as a starting substrate, after laminating an n-type GaAs buffer layer, an n-type GaInP first etch stop layer is epitaxially grown to a thickness of 0.1 μm, and an n-type GaAs second etch stop layer is epitaxially grown to a thickness of 0.1 μm to fabricate 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, 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, a p-type Ga x In 1-x P (0.5 ≤ x ≤ 1.0) intermediate layer (not shown), 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 ( Figure 1 ). Among them, the thickness of the GaP window layer 16 varies within a range of 2 to 5 μm (comparative example), 6 to 15 μm (example).

[0068] Next, as Figure 2As shown, benzocyclobutene (BCB) as a thermosetting bonding member 25 is spin-coated on the epitaxial wafer 20 (on the light-emitting element structure 18), and it is superposed facing the sapphire substrate as the transparent substrate 30. Through thermocompression bonding, the epitaxial wafer and the sapphire substrate are bonded via the BCB. When spin-coating and applying the BCB, the designed film thickness is 0.6 μm.

[0069] Next, as Figure 3 shown, the GaAs substrate 11 as the starting substrate and the etch stop layer 12 are removed by wet etching to fabricate an epitaxial bonding substrate.

[0070] Next, as Figure 4 shown, a pattern is formed by photolithography, and chlorine gas and argon gas are used to perform element separation processing (element separation groove 47) of 50×100 μm by ICP. The ICP processing is performed in two steps: a step of exposing the BCB layer 25 and a step of exposing the second cladding layer 15.

[0071] After the element separation processing, as Figure 5 shown, SiO 2 protective film 52 is formed as an end face treatment.

[0072] After forming the protective film 52, as Figure 6 shown, the first electrode 54 and the second electrode 56 that are in contact with the n-type layer or the p-type layer respectively are formed, and then heat treatment is performed to form an ohmic contact.

[0073] After forming the ohmic contact, as Figure 7 shown, silicone resin 65 is applied, the transfer substrate 70 formed with a convex pattern and made of quartz is opposed to the ohmic electrodes (the first electrode 54 and the second electrode 56), and pressure is applied to make the ohmic electrode portions (the first electrode 54 and the second electrode 56) adhere to the silicone resin 65.

[0074] Next, as Figure 8 shown, by laser lift-off (LLO) processing in which excimer laser is irradiated from the side of the transparent substrate 30 made of sapphire to sublime the BCB layer portion in contact with the sapphire substrate, the sapphire substrate and the micro-LED die are separated ( Figure 9 ). Further, as Figure 10 shown, the BCB is removed.

[0075] Figure 11 shows the results of investigating the yield of each wafer with different thicknesses of the GaP window layer 16. As Figure 11As shown, when the thickness of the GaP window layer 16 is 4 μm or less (comparative example), all the micro-LED elements are broken and the yield is 0. Since the thickness of the GaP window layer 16 is 5 μm (comparative example), the yield rate has increased, but it is not sufficient. When the thickness of the GaP window layer 16 is 6 μm (example), the yield rate is 80% or more. When the thickness of the GaP window layer 16 is 8 μm or more (example), there is no breakage and the yield is 100%.

[0076] This specification includes the following aspects.

[0077] [1]: A method for manufacturing a bonded wafer for micro-LEDs, characterized in that, through the following steps and by irradiating a laser from the side of the transparent substrate to sublime the thermosetting bonding member in contact with the transparent substrate, the transparent substrate and the micro-LED element are separated, thereby manufacturing a bonded wafer for micro-LEDs.

[0078] A step of epitaxially growing a first cladding layer made of AlGaInP of the first conductivity type, an undoped active layer made of AlGaInP, and a second cladding layer made of AlGaInP of the second conductivity type on a GaAs substrate to form an epitaxial layer.

[0079] A step of growing a GaP window layer on the second cladding layer.

[0080] A step of bonding the GaP window layer to a transparent substrate as a substrate to be bonded that is transparent to visible light and ultraviolet light via a thermosetting bonding member.

[0081] A step of peeling off the GaAs substrate.

[0082] A step of separating the epitaxial layer into square micro-LED elements with a short side length of 50 μm or less.

[0083] A step of exposing a part of the second cladding layer or the GaP window layer of the micro-LED element.

[0084] A step of forming a first electrode in contact with the layer of the first conductivity type and a second electrode in contact with the layer of the second conductivity type, and performing heat treatment to form an ohmic contact.

[0085] And a step of bonding the first electrode and the second electrode to a transfer substrate via a silicone resin.

[0086] In this method for manufacturing a bonded wafer for micro-LEDs, the thickness of the GaP window layer is set to 6 μm or more.

[0087] [2]: The manufacturing method of the bonded wafer for micro-LEDs as described in [1] above, wherein the thermosetting bonding member is at least any one of benzocyclobutene, silicone resin, epoxy resin, SOG, polyimide, and amorphous fluororesin.

[0088] [3]: The manufacturing method of the bonded wafer for micro-LEDs as described in [1] or [2] above, wherein the transparent substrate is a sapphire substrate or a quartz substrate.

[0089] [4]: The manufacturing method of the bonded wafer for micro-LEDs as described in [1], [2], or [3] above, wherein the method in the process of separating the epitaxial layer into the micro-LED elements is a method carried out by ICP etching using chlorine gas and argon gas after forming a pattern by photolithography.

[0090] [5]: The manufacturing method of the bonded wafer for micro-LEDs as described in [1], [2], [3], or [4] above, wherein the transfer substrate is a quartz substrate.

[0091] In addition, the present invention is not limited to the above embodiments. The above embodiments are illustrative, and all solutions having substantially the same composition and exhibiting the same effects as the technical concept described in the claims of the present invention are included within the technical scope of the present invention.

Claims

1. A manufacturing method of a bonded wafer for micro LEDs, characterized in that, through the following processes and a laser lift-off process of sublimating a thermosetting bonding member in contact with the transparent substrate by irradiating laser from the transparent substrate side, separating the transparent substrate from the micro LED element, thereby manufacturing a bonded wafer for micro LEDs, a process of epitaxially growing a first cladding layer made of AlGaInP of a first conductivity type, an undoped active layer made of AlGaInP, and a second cladding layer made of AlGaInP of a second conductivity type on a GaAs substrate to form an epitaxial layer; a process of growing a GaP window layer on the second cladding layer; a process of bonding the GaP window layer to a transparent substrate as a substrate to be bonded transparent to visible light and ultraviolet light via a thermosetting bonding member; a process of peeling off the GaAs substrate; a process of separating the epitaxial layer into square micro LED elements with a short side length of 50 μm or less; a process of exposing the second cladding 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 layer of the first conductivity type and a second electrode in contact with the layer of the second conductivity type, and performing heat treatment to form an ohmic contact; and a process of bonding the first electrode and the second electrode to a transfer substrate via a silicone resin, in this manufacturing method of a bonded wafer for micro LEDs, the thickness of the GaP window layer is set to 6 μm or more.

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

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

4. The manufacturing method of a bonded wafer for micro LEDs according to claim 1 or 2, characterized in that, the method in the process of separating the epitaxial layer into the micro LED elements is set to a method performed by forming a pattern using photolithography and inductively coupled plasma etching using chlorine gas and argon gas.

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

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