Temporarily bonded wafer and manufacturing method thereof

Abstract

A provisionally bonded wafer which is obtained by provisionally bonding a supporting substrate and an epitaxial functional layer that has two or more electrodes having different polarities on one surface, and which is characterized in that the surface of the epitaxial functional layer, the surface being provided with the electrodes, and the supporting substrate are provisionally bonded to each other by the intermediary of an uncured thermosetting bonding material. Consequently, the present invention provides a technology which enables a provisionally bonded wafer to be reduced in bonding failure and separation failure after a substrate removal step that is performed after the bonding process, while improving the yield of the provisionally bonded wafer. In addition, this technology also enables easy removal of a provisional supporting substrate.

Description

[Technical field]

[0001] The present invention relates to a temporary bonding method for temporarily bonding a semiconductor substrate to be mounted on a mounting substrate to a temporary support substrate, and a temporarily bonded wafer. [Background technology]

[0002] The technology to separate only an epitaxial functional layer, such as a light-emitting element, from a starting substrate and transfer it to another substrate is important for alleviating the constraints imposed by the physical properties of the starting substrate and increasing the design freedom of the device system. In order to achieve this transfer, a technology is required to bond the epitaxial functional layer to a temporary support substrate, remove the starting substrate, and transfer it to a permanent substrate.

[0003] Patent Document 1 discloses a technique for thermocompression bonding a semiconductor epitaxial substrate and a temporary support substrate via a dielectric layer, and a technique for separating the temporary support substrate and the epitaxial functional layer by wet etching. Patent Document 2 discloses a technique for inserting a transparent conductive layer between an adhesive layer and a functional layer as one form of bonding, although it is not directly related to improving the bonding property.

[0004] Patent Document 3 discloses a technique in which temporary bonding is performed using polyimide, the starting substrate is removed, and then an electrode is formed on the surface on which the substrate was removed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-27301 [Patent Document 2] Patent No. 4159421 [Patent Document 3] JP 2008-187160 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in Patent Document 3, by forming an electrode after temporary bonding and removing the starting substrate, there is a problem that peeling occurs due to heat treatment during ohmic contact formation. In particular, when forming a heterostructure combining materials with large lattice mismatch or materials with large differences in thermal expansion coefficient, the bimetal effect during heat treatment tends to increase the peeling rate.

[0007] In order to lower the temperature for forming ohmic contacts, it is necessary to dope the dopant impurities to a concentration close to the solubility limit, but a crystal layer doped to a concentration close to the solubility limit is more likely to have poorer crystal quality than a relatively lightly doped crystal layer. The highly doped layer must be provided between the starting substrate and the functional layer. Since the functional layer is provided on top of the highly doped layer, it is affected by the quality of the highly doped layer. In other words, the poor quality of the highly doped layer below the functional layer will also result in a deterioration in the quality of the functional layer.

[0008] In addition, in order to avoid the influence of thermal deformation caused by the bimetal, it is considered to select a material system with a small difference in thermal expansion coefficient. However, it is impossible to select a material with a small difference in thermal expansion coefficient while maintaining the function of the functional layer, and the only technical option is to reduce the influence of the difference in thermal expansion coefficient, that is, to make each layer thinner. Although it is technically possible to design the film thickness to be thin, it is highly likely that the carrier behavior in the functional layer cannot be sufficiently controlled by making the film thickness thin, and the design function of the functional layer is reduced.

[0009] Due to the above-mentioned background, when forming electrodes and forming ohmic contacts after temporary bonding of a support substrate, it has been extremely difficult to prevent peeling due to the bimetal effect.

[0010] The present invention has been made in consideration of the above problems, and aims to provide a technology that reduces bonding defects and peeling defects in temporary bonded wafers after the starting substrate removal process following bonding processing, improves yield, and makes it easy to remove the temporary support substrate. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention provides A temporarily bonded wafer in which an epitaxial functional layer having two or more electrodes of different polarities on one surface is temporarily bonded to a support substrate, The present invention provides a temporarily bonded wafer in which a surface of the epitaxial functional layer having the electrode and the supporting substrate are temporarily bonded via an uncured thermosetting bonding material.

[0012] In the case of a temporarily bonded wafer in which a support substrate is temporarily bonded to the surface on which the electrodes are formed with a thermosetting bonding material in an uncured state, there is no bonding failure or peeling failure at the temporarily bonded portion, and since the bonding material is bonded in an uncured state, the temporary support substrate can be easily removed.

[0013] The epitaxial functional layer is preferably a light emitting element.

[0014] The temporarily bonded wafer of the present invention can be used for such purposes.

[0015] It is also preferable that the epitaxial functional layer contains an AlGaInP-based or InGaN-based material.

[0016] The present invention can be particularly suitably used in the case of epitaxial functional layers that include such materials.

[0017] The thermosetting bonding material is preferably any one of benzocyclobutene (BCB) resin, polyimide (PI) resin, fluororesin, and epoxy resin.

[0018] Such a thermosetting bonding material not only allows temporary bonding in a softened state, but also allows easy peeling.

[0019] The support substrate is preferably made of any one of silicon, sapphire, GaP, GaAs, InP, SiC, quartz, glass, LiTaO3, and LiNbO3.

[0020] In the present invention, for example, such a support substrate can be used.

[0021] Furthermore, the provisionally bonded wafer of the present invention may have no starting substrate on the surface of the epitaxial functional layer opposite the surface having the electrode.

[0022] In this manner, the temporarily bonded wafer of the present invention can be one from which the starting substrate has been removed.

[0023] The present invention also provides a method for temporarily bonding an epitaxial substrate, which is formed by growing an epitaxial functional layer on a starting substrate, to a support substrate, comprising the steps of: (1) forming two or more electrodes having different polarities on one surface of the epitaxial functional layer of the epitaxial substrate; and (2) a step of temporarily bonding the support substrate to the surface on which the electrodes are formed via an uncured thermosetting bonding material; The present invention provides a method for producing a temporarily bonded wafer, comprising the steps of:

[0024] By manufacturing the temporary bonded wafer in this manner, the temporary bonding process is performed after the electrode formation process, so there is no thermal constraint associated with electrode formation, and therefore poor bonding and peeling between the epitaxial functional layer and the temporary support substrate can be prevented, and the yield can be improved. In addition, since the bonding material is temporarily bonded to the temporary support substrate in an uncured state, the temporary support substrate can be easily removed.

[0025] The epitaxial functional layer is preferably used as a light emitting device.

[0026] The present invention can be used to manufacture temporarily bonded wafers for such applications.

[0027] It is also preferable that the epitaxial functional layer contains an AlGaInP-based or InGaN-based material.

[0028] The present invention can be particularly suitably used in the case of epitaxial functional layers that include such materials.

[0029] The thermosetting bonding material is preferably any one of benzocyclobutene (BCB) resin, polyimide (PI) resin, fluororesin, and epoxy resin.

[0030] Such a thermosetting bonding material not only allows temporary bonding in a softened state, but also allows easy peeling.

[0031] Also, it is preferable that the support substrate is made of any one of the following materials: silicon, sapphire, GaP, GaAs, InP, SiC, quartz, glass, LiTaO3, and LiNbO3.

[0032] The present invention can use, for example, such a support substrate.

[0033] Furthermore, the method for producing a temporarily bonded wafer of the present invention may further include, after the step (2), a step (3) of removing the starting substrate from the epitaxial substrate.

[0034] In this manner, a provisionally bonded wafer that does not have a starting substrate can be manufactured. Effect of the Invention

[0035] As described above, the present invention can provide a technology that reduces bonding defects and peeling defects in a temporarily bonded wafer after the starting substrate removal process following the bonding process, improves yield, and further makes it easy to remove the temporary support substrate. [Brief description of the drawings]

[0036] [Figure 1] 1 is a schematic diagram showing an example of a temporarily bonded wafer of the present invention. [Diagram 2] 1 is a schematic diagram showing the fabrication of an epitaxial substrate by growing an epitaxial functional layer on a GaAs starting substrate in a first embodiment of a method for producing a temporary bonded wafer of the present invention. FIG. [Diagram 3]FIG. 2 is a schematic diagram showing a first electrode formed on a GaP window layer in the first embodiment. [Figure 4] 3 is a schematic diagram showing a state in which an AlGaInP first cladding layer is exposed by dry etching in the first embodiment. FIG. [Diagram 5] FIG. 2 is a schematic diagram showing a state in which a second electrode is formed on an AlGaInP first cladding layer in the first embodiment. [Figure 6] 1 is a schematic diagram showing a state in which a surface of an epitaxial functional layer on which an electrode is formed is temporarily bonded to a support substrate via BCB resin to produce a temporarily bonded wafer in the first embodiment. FIG. [Figure 7] 4 is a schematic diagram showing a state in which the GaAs starting substrate has been removed from the temporarily bonded wafer produced in the first embodiment. FIG. [Figure 8] 1 is a schematic diagram showing a state in the first embodiment in which the provisionally bonded wafer from which the GaAs starting substrate has been removed and the silicon wafer are adhered via silicone, and the support substrate is then peeled off. FIG. [Figure 9] FIG. 11 is a schematic diagram showing the process for producing an epitaxial substrate by growing an epitaxial functional layer on a starting sapphire substrate in a second embodiment of the method for producing a provisionally bonded wafer of the present invention. [Figure 10] FIG. 11 is a schematic diagram showing a state in which a first electrode is formed on a GaN contact layer in the second embodiment. [Figure 11] FIG. 11 is a schematic diagram showing the state in which the GaN first cladding layer is exposed by dry etching in the second embodiment. [Figure 12] FIG. 11 is a schematic diagram showing a second electrode formed on a GaN first cladding layer in the second embodiment. [Figure 13] 13 is a schematic diagram showing a second embodiment in which a surface of an epitaxial functional layer on which an electrode is formed is temporarily bonded to a support substrate via BCB resin to produce a temporarily bonded wafer. FIG. [Figure 14] 11 is a schematic diagram showing the state in which the sapphire starting substrate is removed from the temporarily bonded wafer produced in the second embodiment. FIG. [Figure 15]FIG. 11 is a schematic diagram showing a state in the second embodiment in which the temporarily bonded wafer from which the sapphire starting substrate has been removed and a silicon wafer are adhered together via silicone, and the support substrate is then peeled off. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] As described above, when electrodes are formed after the supporting substrate is temporarily bonded, there is a problem that peeling occurs due to heat treatment during the formation of ohmic contacts. In particular, when a heterostructure is formed by combining materials with large lattice mismatch or materials with large differences in thermal expansion coefficients, the bimetal effect during heat treatment tends to increase the peeling rate.

[0038] The inventors conducted extensive research into these problems and discovered that by temporarily bonding a surface of an epitaxial functional layer having two or more electrodes of different polarity to a support substrate using a thermosetting bonding material in an uncured state, peeling of the temporary bonded portion due to the heat treatment used to form the electrodes does not occur, and further, because the thermosetting bonding material is bonded in an uncured state, the temporary bonded support substrate can be removed extremely easily when necessary, thereby completing the present invention.

[0039] In other words, the present invention is a temporarily bonded wafer in which an epitaxial functional layer having two or more electrodes of different polarity on one surface is temporarily bonded to a support substrate, and the electrode-bearing surface of the epitaxial functional layer and the support substrate are temporarily bonded via an uncured thermosetting bonding material.

[0040] The present invention will be described in detail below, but the present invention is not limited thereto.

[0041] [Temporarily bonded wafers] An example of a temporarily bonded wafer of the present invention is shown in Figure 1. In the temporarily bonded wafer 100 of the present invention, an epitaxial functional layer 1 has two electrodes 2 of different polarity on one surface, and the surface of the epitaxial functional layer 1 having the electrodes 2 and a supporting substrate 3 are temporarily bonded via an uncured thermosetting bonding material 4.

[0042] A conventional temporarily bonded wafer has a structure in which an electrode is formed on one side of an epitaxial functional layer, and a support substrate is temporarily bonded to the other side (opposite the electrode-formed side). This is because, in the manufacturing process of a conventional temporarily bonded wafer, first, an epitaxial layer of an epitaxial substrate having an epitaxial functional layer formed on a starting substrate is temporarily bonded to the support substrate, and then the starting substrate is removed, and an electrode is formed on the surface from which the starting substrate has been removed. In contrast, the temporarily bonded wafer of the present invention has a structure in which an electrode is disposed between the epitaxial functional layer and the support substrate, unlike the conventional temporarily bonded wafer. This structure is obtained because the wafer is manufactured by forming an electrode and then performing temporary bonding according to the manufacturing method of the temporarily bonded wafer of the present invention described below.

[0043] [Manufacturing method for temporary bonded wafers] In view of the above, the present invention provides a method for temporarily bonding an epitaxial substrate, which is formed by growing an epitaxial functional layer on a starting substrate, to a support substrate, comprising the steps of: (1) forming two or more electrodes having different polarities on one surface of the epitaxial functional layer of the epitaxial substrate; and (2) a step of temporarily bonding the support substrate to the surface on which the electrodes are formed via an uncured thermosetting bonding material; The present invention provides a method for producing a temporarily bonded wafer, comprising the steps of:

[0044] Unlike the conventional method of performing heat treatment (ohmic heat treatment) for forming ohmic contacts of electrodes on a wafer having a temporary bond, the manufacturing method of such a temporary bonded wafer performs electrode formation and ohmic heat treatment on a wafer prior to the formation of the temporary bond, and then performs temporary bonding with a support substrate. Therefore, since peeling or thermal deformation of the temporary bond does not occur due to high-temperature heat treatment during electrode formation, the temporary bonded wafer can be manufactured with a high yield. Furthermore, in the manufacturing method of the temporary bonded wafer of the present invention, the temporary bonding is performed via an uncured thermosetting bonding material, so that the support substrate can be easily removed.

[0045] Hereinafter, the present invention will be described in more detail with reference to the drawings for embodiments, but the present invention is not limited thereto.

[0046] (First Embodiment) A first embodiment of a method for manufacturing a temporarily bonded wafer of the present invention will be described with reference to FIGS. 2 to 8. In the first embodiment, the epitaxial functional layer is made to contain an AlGaInP-based material.

[0047] First, as shown in FIG. 2, after laminating a first-conductivity-type GaAs buffer layer 102 on a first-conductivity-type GaAs starting substrate 101, a first-conductivity-type Ga y In 1-y P (0.4 ≦ y ≦ 0.6) first etch stop layer 103, for example, 0.3 μm, a first-conductivity-type GaAs second etch stop layer 104, for example, 0.3 μm, and a first-conductivity-type (Al x Ga 1-x ) y In 1-y P (0 < x ≦ 1, 0.4 ≦ y ≦ 0.6) first cladding layer 105, for example, 1.0 μm, an undoped (Al x Ga 1-x ) y In 1-y P (0 ≦ x ≦ 0.6, 0.4 ≦ y ≦ 0.6) active layer 106, a second-conductivity-type (Al x Ga 1-x ) y In 1-y P (0 < x ≦ 1, 0.4 ≦ y ≦ 0.6) second cladding layer 107, for example, 1.0 μm, a second-conductivity-type Ga y In 1-y P (0.45 ≦ y ≦ 1) intermediate layer 108, for example, 0.1 μm, and a second-conductivity-type GaP window layer 109, for example, 4 μm, are sequentially grown to prepare an epitaxial substrate having a light-emitting element structure as an epitaxial functional layer. Here, from the AlGaInP first cladding layer 105 to the AlGaInP second cladding layer 107 is referred to as a double heterostructure (DH) portion 111 (FIG. 3).

[0048] 3, a first electrode 110 is formed on a partial region of the second conductivity type GaP window layer 109. A highly reflective metal is preferably used for the first electrode 110, and an Au-based electrode can be used. For example, an AuBe alloy can be used as the metal in contact with the GaP window layer 109, and Au can be laminated thereon to form the first electrode 110.

[0049] The metal in contact with the second conductivity type GaP window layer 109 is not limited to the AuBe alloy, and any metal or alloy can be selected as long as an ohmic contact can be formed. In general, alloys such as AuZn are often selected other than AuBe.

[0050] Next, after forming the first electrode 110 as shown in FIG. 4, a part of the region of the second-conductivity-type GaP window layer 109 other than the region where the first electrode 110 is to be formed is covered with a material having etching selectivity such as SiO2 or SiNx as a mask, and the exposed portion is cut out by a method such as dry etching to expose the first-conductivity-type AlGaInP first cladding layer 105.

[0051] 5, the second-conductivity-type GaP window layer 109, the side surface of the cutout, and the first-conductivity-type AlGaInP first cladding layer 105 are covered with SiO2 or SiNx as a PSV (passivation) film 113, and the first electrode 110 and a part of the first-conductivity-type AlGaInP first cladding layer 105 are exposed by photolithography. Then, a second electrode 112 is formed on the exposed portion on the first-conductivity-type AlGaInP first cladding layer 105.

[0052] The second electrode 112 is preferably made of a highly reflective metal, and may be an Au-based electrode. For example, the second electrode 112 may be made by using an AuSi alloy as the metal in contact with the first conductive type AlGaInP first cladding layer 105, and laminating Au thereon.

[0053] Moreover, the metal in contact with the first conductivity type AlGaInP cladding layer 105 is not limited to the AuSi alloy, and any metal or alloy can be selected as long as an ohmic contact can be formed. In general, alloys such as AuGe are often selected other than AuSi.

[0054] Moreover, it is not necessarily required to form the PSV film 113 before forming the second electrode 112, and the PSV film 113 may be formed after forming the second electrode 112. Furthermore, the same effect can be obtained even if the PSV film 113 itself is not formed.

[0055] After the first and second electrodes 110 and 112 are formed, an RTA heat treatment is performed for example at 400° C. for 5 minutes in order to obtain ohmic contact. Although the RTA treatment is exemplified here, the RTA treatment is not limited to this, and treatment may be performed at a relatively low temperature, for example, at 350° C. for about 30 minutes.

[0056] 6, after forming ohmic contacts, BCB resin 114 is spin-coated on the electrode formation surface, and placed opposite a support substrate 115 selected from silicon or the like, and pressure is applied in a vacuum atmosphere and maintained at 150°C for about 15 minutes to temporarily bond to the support substrate 115. Since the BCB resin 114 hardens when maintained at a temperature above 150°C, hardening of the BCB resin 114 can be prevented by maintaining the temperature at 150°C or less. Leaving the BCB resin 114 unhardened can improve the peelability of the support substrate 115 from the epitaxial substrate.

[0057] Furthermore, the thermosetting bonding material is not limited to benzocyclobutene (BCB) resin, but may be, for example, polyimide (PI) resin, fluororesin, or epoxy resin.

[0058] The support substrate 115 is not limited to silicon, and any material having good surface flatness can be selected, such as sapphire, GaP, GaAs, InP, quartz, glass, LiTaO3, LiNbO3, crystal, and SiC.

[0059] Next, as shown in FIG. 7, after temporarily bonding to the support substrate 115, the starting substrate is removed by a selective etching method. The GaAs starting substrate 101 is removed with aqueous ammonia peroxide, the GaInP first etch stop layer 103 is removed with diluted hydrochloric acid or a hydrochloric acid-based etchant, and finally the GaAs second etch stop layer 104 is removed with sulfuric acid peroxide to expose the p-type AlGaInP first cladding layer 105. In this way, a temporarily bonded wafer can be manufactured.

[0060] Finally, as shown in FIG. 8, after exposing the p-type AlGaInP first cladding layer 105 of the temporarily bonded wafer, it is adhered to a silicon wafer 117 coated with silicone 116. The BCB resin 114 in a softened state is dissolved with a BCB dissolving solution to peel off the support substrate 115, and individual chips are formed.

[0061] (Second Embodiment) A second embodiment of the method for manufacturing a temporarily bonded wafer of the present invention will be described with reference to FIGS. 9 to 15. In the second embodiment, the epitaxial functional layer includes an InGaN-based material.

[0062] First, as shown in FIG. 9, on a sapphire starting substrate 201, after laminating a p-type GaN buffer layer 202, a p-type GaN first cladding layer 203 is, for example, 1.0 μm, and an undoped In z Ga 1-z N (0 < z ≦ 0.4) active layer 204, a n-type Al v Ga 1-v N (0 ≦ v ≦ 0.4) (GaN) second cladding layer 205 is, for example, 1.0 μm, and a n-type GaN contact layer 206 is, for example, 0.1 μm, and an epitaxial substrate having a light-emitting element structure as an epitaxial functional layer is sequentially grown. Here, from the GaN first cladding layer 203 to the AlGaN second cladding layer 205 is referred to as a double heterojunction (DH) structure portion 208 (FIG. 10).

[0063] 10, a first electrode 207 is formed on a partial region of the second conductivity type GaN contact layer 206. It is preferable to use a highly reflective metal for the first electrode 207, and an electrode using Ag can be used. The first electrode 207 can be formed by using Ag as the metal in contact with the GaN contact layer 206 and laminating Pd thereon.

[0064] Moreover, the metal in contact with the second conductivity type GaN contact layer 206 is not limited to Ag-based metals, and any metal or alloy can be selected as long as an ohmic contact can be formed. In general, metals other than Ag, such as Au and Ti, are often selected.

[0065] Next, after forming the first electrode 207 as shown in FIG. 11, a part of the region of the second conductivity type GaN contact layer 206 other than the region where the first electrode 207 is to be formed is covered with a material having etching selectivity such as SiO2 or SiNx as a mask, and the exposed portion is cut out by a method such as dry etching to expose the first conductivity type GaN first cladding layer 203.

[0066] 12, GaN contact layer 206, the side surface of the notch, and GaN first cladding layer 203 are covered with SiO2 or SiNx as PSV film 210, and first electrode 207 and a part of GaN first cladding layer 203 are exposed by photolithography. Second electrode 209 is formed on the exposed portion on GaN first cladding layer 203.

[0067] Moreover, it is preferable to use a highly reflective metal for the second electrode 209, and an Al-based electrode can be used. For example, the second electrode 209 can be formed by using Al metal as the metal in contact with the first conductivity type GaN first cladding layer 203 and laminating Au thereon.

[0068] Moreover, the metal in contact with the first conductivity type GaN first cladding layer 203 is not limited to Al metal, and any metal or alloy can be selected as long as an ohmic contact can be formed. In general, metals other than Al, such as Ti and Au, are often selected.

[0069] Moreover, it is not necessarily required to form the PSV film 210 before forming the second electrode 209, and the PSV film 210 may be formed after forming the second electrode 209. Furthermore, the same effect can be obtained even if the PSV film 210 itself is not formed.

[0070] After the first and second electrodes 207 and 209 are formed, an RTA heat treatment is performed at, for example, 700° C. for 5 minutes in order to obtain ohmic contact.

[0071] 13, after forming ohmic contacts, BCB resin 211 is spin-coated on the electrode formation surface, and placed opposite a support substrate 212 selected from silicon or the like, and pressure is applied in a vacuum atmosphere and maintained at 150°C for about 15 minutes to temporarily bond to the support substrate 212. Since the BCB resin 211 hardens when maintained at a temperature exceeding 150°C, hardening of the BCB resin 211 can be prevented by maintaining a temperature of 150°C or less. By leaving the BCB resin 211 unhardened, the peelability of the support substrate 212 from the epitaxial substrate can be improved.

[0072] Furthermore, the thermosetting bonding material is not limited to benzocyclobutene (BCB) resin, but may be, for example, polyimide (PI) resin, fluororesin, or epoxy resin.

[0073] The support substrate 212 is not limited to silicon, and any material having good surface flatness can be selected, such as sapphire, GaP, GaAs, InP, quartz, glass, LiTaO3, LiNbO3, crystal, and SiC.

[0074] 14, after the temporary bonding, a laser is irradiated from the starting substrate side to ablate the GaN buffer layer 202, removing the sapphire starting substrate 201 and exposing the first conductivity type GaN first cladding layer 203. In this manner, a temporarily bonded wafer can be manufactured.

[0075] Finally, as shown in FIG. 15, after exposing the first-conductivity-type GaN first cladding layer 203, it is adhered to a silicon wafer 214 coated with silicone 213. The softened BCB resin 211 is dissolved with a BCB solution to peel off the support substrate 212, and individual chips are formed.

Example

[0076] Hereinafter, the present invention will be specifically described using examples and comparative examples, but the present invention is not limited thereto.

[0077] (Example 1) On a first-conductivity-type GaAs starting substrate, after laminating a first-conductivity-type GaAs buffer layer, a first-conductivity-type Ga y In 1-y P (0.4 ≦ y ≦ 0.6) first etch stop layer of 0.3 μm, a first-conductivity-type GaAs second etch stop layer of 0.3 μm, a first-conductivity-type (Al x Ga 1-x ) y In 1-y P (0 <x ≦ 1, 0.4 ≦ y ≦ 0.6) first cladding layer of 1.0 μm, undoped (Al x Ga 1-x ) y In 1-y P (0 ≦ x ≦ 0.6, 0.4 ≦ y ≦ 0.6) active layer, a second-conductivity-type (Al x Ga 1-x ) y In 1-y P (0 <x ≦ 1, 0.4 ≦ y ≦ 0.6) second cladding layer of 1.0 μm, a second-conductivity-type Ga y In 1-y P (0.45 ≦ y ≦ 1) intermediate layer of 0.1 μm, and a second-conductivity-type GaP window layer of 4 μm were sequentially grown to prepare an epitaxial substrate having a light-emitting element structure as an epitaxial functional layer (see FIG. 2).

[0078] Next, a first electrode is formed in a partial region of the second-conductivity-type GaP window layer. It is preferable to use a highly reflective metal for the first electrode, and an electrode using an Au-based material was used. In this technology, an AuBe alloy was used as the metal in contact with the GaP window layer, and Au was laminated thereon to form the first electrode (see FIG. 3).

[0079] After forming the first electrode, a portion of the second conductivity type GaP window layer other than the region where the first electrode was to be formed was covered with SiO2, and the exposed portion was cut away by dry etching to expose the first conductivity type AlGaInP first cladding layer (see Figure 4).

[0080] The second-conductivity-type GaP window layer, the side of the notch, and the first-conductivity-type AlGaInP first cladding layer were covered with SiO2 as a PSV film, and the first electrode and a part of the first-conductivity-type AlGaInP first cladding layer were exposed by photolithography. A second electrode was then formed on the exposed part of the first-conductivity-type AlGaInP first cladding layer. The second electrode was formed by using an AuSi alloy as the metal in contact with the first-conductivity-type AlGaInP first cladding layer, and layering Au on top of that (see Figure 5).

[0081] After forming the first and second electrodes, RTA heat treatment was performed at 400°C for 5 minutes to obtain ohmic contact.

[0082] After forming the ohmic contact, BCB resin was spin-coated on the electrode formation surface, which was then placed opposite a silicon support substrate. Pressure was applied in a vacuum atmosphere, and the substrate was temporarily bonded to the support substrate by maintaining the substrate at 150°C for approximately 15 minutes (see Figure 6).

[0083] After temporary bonding to the support substrate, the GaAs starting substrate was removed with ammonia hydrogen peroxide, the GaInP first etch stop layer was removed with diluted hydrochloric acid or a hydrochloric acid-based etchant, and finally the GaAs second etch stop layer was removed with sulfuric acid hydrogen peroxide to expose the first conductivity type AlGaInP first cladding layer (see Figure 7).

[0084] After exposing the first conductive type AlGaInP first cladding layer, it was attached to a silicon wafer coated with silicone, and the softened BCB resin was dissolved in a BCB dissolving solution to peel off the support substrate and create individual chips (see Figure 8).

[0085] Example 2 After laminating a GaN buffer layer of the first conductivity type on a sapphire starting substrate, a GaN first cladding layer of the first conductivity type with a thickness of 1.0 μm, and an undoped In z Ga 1-z N (0 < z ≤ 0.4) active layer, an Al v Ga 1-v N (0 ≤ v ≤ 0.4) (GaN) second cladding layer with a thickness of 1.0 μm, and a GaN contact layer of the second conductivity type with a thickness of 0.1 μm were successively grown to prepare an epitaxial substrate having a light-emitting element structure as an epi-functional layer (see Fig. 9).

[0086] Next, Ag was used as the metal in contact with the GaN contact layer in a partial region of the GaN contact layer of the second conductivity type, and Pd was laminated thereon to form a first electrode (see Fig. 10).

[0087] After forming the first electrode, a part of the region of the GaN contact layer of the second conductivity type other than the first electrode formation region was coated with SiO2, the exposed portion was notched by dry etching, and the GaN first cladding layer of the first conductivity type was exposed (see Fig. 11).

[0088] The GaN contact layer, the side surface of the notch, and the GaN first cladding layer were coated with SiO2 as a PSV film, and a part of the first electrode portion and the GaN first cladding layer were exposed by photolithography. On the exposed portion on the GaN first cladding layer, Al metal was used as the metal in contact with the GaN first cladding layer of the first conductivity type, and Au was laminated thereon to form a second electrode (see Fig. 12).

[0089] After forming the first and second electrodes, an RTA heat treatment was performed at 700 °C for 5 minutes to obtain an ohmic contact.

[0090] After forming the ohmic contact, a BCB resin was spin-coated on the electrode formation surface side, opposed to a support substrate made of silicon, pressure was applied in a vacuum atmosphere, and it was held at 150 °C for about 15 minutes to temporarily bond to the support substrate (see Fig. 13).

[0091] After temporary bonding, the GaN buffer layer was ablated by irradiating a laser from the starting substrate side, the starting substrate was removed, and the n-type GaN first cladding layer was exposed (see Fig. 14).

[0092] After the n-type GaN cladding layer was exposed, it was adhered to a silicon wafer coated with silicone, the softened BCB resin was dissolved with a BCB solution to peel off the support substrate, and individual chips were formed (see Fig. 15).

[0093] (Comparative Example) On an n-type GaAs starting substrate, after laminating an n-type GaAs buffer layer, n-type Ga y In 1-y P (0.4 ≤ y ≤ 0.6) first etch stop layer of 0.3 μm, n-type GaAs second etch stop layer of 0.3 μm, n-type (Al x Ga 1-x ) y In 1-y P (0 < x ≤ 1, 0.4 ≤ y ≤ 0.6) first cladding layer of 1.0 μm, undoped (Al x Ga 1-x ) y In 1-y P (0 ≤ x ≤ 0.6, 0.4 ≤ y ≤ 0.6) active layer, p-type (Al x Ga 1-x ) y In 1-y P (0 < x ≤ 1, 0.4 ≤ y ≤ 0.6) second cladding layer of 1.0 μm, p-type Ga y In 1-y P (0.45 ≤ y ≤ 1) intermediate layer of 0.1 μm, p-type GaP window layer of 4 μm, and an epitaxial substrate having a light-emitting element structure as an epitaxial functional layer grown in sequence was prepared.

[0094] 1.0 μm of BCB resin was spin-coated on the epitaxial substrate, overlapped with a sapphire wafer facing each other, and thermocompression bonded to fabricate an epitaxial bonded substrate in which the epitaxial substrate and the sapphire wafer were bonded via BCB. At the time of bonding, a curing treatment was performed by holding at 250 °C for 1 hour.

[0095] The GaAs starting substrate was removed with ammonia / hydrogen peroxide water to expose the GaInP first etch stop layer. The etchant was switched to a hydrochloric acid system to remove the GaInP first etch stop layer and expose the GaAs second etch stop layer. The etchant was switched to a sulfuric acid / hydrogen peroxide water system to remove the GaAs second etch stop layer and expose the first cladding layer. By carrying out the above processes, an epitaxial junction substrate that retains only the double hetero layer and the window layer was produced.

[0096] After removing the starting substrate, an AuBe-based metal was used for the metal in contact with the surface (first cladding layer) of the starting substrate from which the starting substrate had been removed, and Au was laminated thereon to form a first electrode.

[0097] After the first electrode was formed, a part of the first clad layer other than the region where the first electrode was to be formed was cut out by a method such as dry etching, and the second clad layer was exposed in the cutout portion.

[0098] The AlGaInP first cladding layer, the side of the notch, and the AlGaInP second cladding layer were covered with a passivation (PSV) film, and the first electrode and a part of the AlGaInP second cladding layer were exposed by photolithography. A second electrode made of Au was then formed on the exposed part of the second cladding layer.

[0099] After forming the first and second electrodes, RTA heat treatment was performed at 400°C for 5 minutes to obtain ohmic contact.

[0100] After adhering to the silicone-coated wafer, a laser was irradiated from the supporting substrate side to ablate the device, and the supporting substrate and device were separated.

[0101] (Comparison of results between Examples and Comparative Examples) The temporarily bonded wafers produced in Examples 1 and 2 and the Comparative Example were compared in terms of area yield, doping level, area yield when P-CVD was employed, and leakage defect rate as follows.

[0102] [Area yield] Table 1 shows a comparison of yields (ratio of bonding area). In Examples 1 and 2, the electrode formation process and element isolation process were completed before temporary bonding, so the temporary bonded portions did not peel off or deform due to ohmic heat treatment, and the processes could be carried out in a wafer state with good flatness and warpage, so the yield associated with the electrode formation process and element isolation process could be maintained at the same level as that of non-bonded wafers. On the other hand, in the comparative example, a high-temperature RTA heat treatment was performed on a wafer with temporary bonded portions, which caused the temporary bonded portions to peel off and deform, and sufficient yield was not obtained.

[0103] [Table 1]

[0104] [Doping level] Even if the BCB film is hardened, it cannot be treated at high temperatures because it loses its bonding strength when the temperature exceeds its softening point. To form an ohmic contact, it is necessary to either treat it at a temperature above the BCB softening point, or to make the metal contact layer a highly doped layer to avoid high temperature treatment. However, heat treatment above the BCB softening point is likely to induce deformation of the BCB bonding layer, leading to a decrease in device yield. On the other hand, making the contact layer highly doped is likely to induce device degradation during current application due to the electromigration effect, leading to a decrease in performance. Performing the electrode formation and device isolation process in the wafer state before the BCB bonding layer formation has the effect of avoiding the thermal constraints and epitaxial substrate design constraints mentioned above, increasing the degree of design freedom and avoiding the quality deterioration of devices due to process constraints.

[0105] Table 2 shows the doping levels required for the first and second electrode contact layers in Examples 1 and 2 and the Comparative Example. In the Examples, high temperature processing is possible during electrode formation, so ohmic contact is obtained at a doping level of the order of 17. On the other hand, in the Comparative Example, ohmic heat treatment is performed for electrode formation on a wafer including a BCB temporary bond, so high temperature processing would cause the temporary bond to peel off. Therefore, in the Comparative Example, low temperature heat treatment is required to maintain a high yield, so a doping level of the order of 18 is required.

[0106] When a cladding layer with a doping level of 18th power is formed, defects are likely to occur in the active layer due to electromigration during current flow, and there is a high possibility that the element will deteriorate due to current flow. A light-emitting element with a doping level of 18th power satisfies the quality only for initial characteristics, but does not meet the quality for transient characteristics. In the embodiment, an epitaxial layer with a doping level one order of magnitude lower can be used, so the problem of not meeting the transient characteristics that occurs in the comparative example can be avoided.

[0107] [Table 2]

[0108] [Area yield when using P-CVD] To form SiO2 as a PSV film, a film formation method such as P-CVD is required, and a thermal environment of 400°C or higher is required due to material reaction system factors. When forming a film using P-CVD after BCB bonding (comparison example), film formation must be performed under conditions at the BCB softening point, which makes it easy for the BCB film to deform during film formation. The deformation of the BCB film manifests itself as the epitaxial layer lifting (peeling), and the lifted part eventually peels off, reducing the yield.

[0109] The yield (ratio of bonding area) when the P-CVD process was started is shown in Table 3. As shown in Table 3, a high yield was obtained in the working examples, whereas in the comparative example in which the PSV film formation process was carried out after temporary bonding, peeling of the bonding portion occurred during the PSV film formation process, resulting in a decrease in yield.

[0110] [Table 3]

[0111] [Leak defect rate] In addition, if the PSV film is only a hard mask, it is possible to select a film formation method other than the P-CVD method, for example, a physical film formation method. However, in PSV film formation, the physical film formation method has a problem that the coverage rate of the side surface is poor, and leakage that occurs on the side surface cannot be suppressed.

[0112] Therefore, as shown in Table 4, in the comparative example in which the optimal P-CVD method for PSV film formation could not be adopted, the leakage defect rate was higher than in Example 1 and Example 2 in which the P-CVD method could be adopted.

[0113] [Table 4]

[0114] The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included in the technical scope of the present invention.

Claims

1. A temporarily bonded wafer in which an epitaxial functional layer having two or more electrodes of different polarities on one surface is temporarily bonded to a support substrate, A temporarily bonded wafer, characterized in that a surface of the epitaxial functional layer having the electrode and the supporting substrate are temporarily bonded via an uncured thermosetting bonding material.

2. The temporarily bonded wafer according to claim 1 , wherein the epitaxial functional layer is a light emitting device.

3. 2. The temporarily bonded wafer according to claim 1, wherein the epitaxial functional layer contains an AlGaInP-based or InGaN-based material.

4. 3. The temporarily bonded wafer according to claim 2, wherein the epitaxial functional layer contains an AlGaInP-based or InGaN-based material.

5. 2. The temporarily bonded wafer according to claim 1, wherein the thermosetting bonding material is any one of benzocyclobutene (BCB) resin, polyimide (PI) resin, fluororesin, and epoxy resin.

6. 3. The temporarily bonded wafer according to claim 2, wherein the thermosetting bonding material is any one of benzocyclobutene (BCB) resin, polyimide (PI) resin, fluororesin, and epoxy resin.

7. 4. The temporarily bonded wafer according to claim 3, wherein the thermosetting bonding material is any one of benzocyclobutene (BCB) resin, polyimide (PI) resin, fluororesin, and epoxy resin.

8. 5. The temporarily bonded wafer according to claim 4, wherein the thermosetting bonding material is any one of benzocyclobutene (BCB) resin, polyimide (PI) resin, fluororesin, and epoxy resin.

9. The support substrate is made of silicon, sapphire, GaP, GaAs, InP, SiC, quartz, glass, LiTaO ３ , and LiNbO ３ 9. The temporarily bonded wafer according to claim 1, wherein the temporarily bonded wafer is made of any one of the materials listed above.

10. 9. The provisionally bonded wafer according to claim 1, wherein the epitaxial functional layer has no starting substrate on a surface opposite to the surface having the electrode.

11. A method for temporarily bonding an epitaxial substrate, in which an epitaxial functional layer is grown on a starting substrate, to a support substrate, comprising the steps of: (1) forming two or more electrodes having different polarities on one surface of the epitaxial functional layer of the epitaxial substrate; and (2) a step of temporarily bonding the support substrate to the surface on which the electrodes are formed via an uncured thermosetting bonding material; A method for producing a temporarily bonded wafer, comprising:

12. The method for producing a temporary bonded wafer according to claim 11, wherein the epitaxial functional layer is a light emitting element.

13. The method for producing a temporary bonded wafer according to claim 11, wherein the epitaxial functional layer contains an AlGaInP-based or InGaN-based material.

14. 13. The method for producing a temporary bonded wafer according to claim 12, wherein the epitaxial functional layer contains an AlGaInP-based or InGaN-based material.

15. 12. The method for producing a temporary bonded wafer according to claim 11, wherein the thermosetting bonding material is any one of benzocyclobutene (BCB) resin, polyimide (PI) resin, fluororesin, and epoxy resin.

16. 13. The method for producing a temporarily bonded wafer according to claim 12, wherein the thermosetting bonding material is any one of benzocyclobutene (BCB) resin, polyimide (PI) resin, fluororesin, and epoxy resin.

17. 14. The method for producing a temporarily bonded wafer according to claim 13, wherein the thermosetting bonding material is any one of benzocyclobutene (BCB) resin, polyimide (PI) resin, fluororesin, and epoxy resin.

18. 15. The method for producing a temporarily bonded wafer according to claim 14, wherein the thermosetting bonding material is any one of benzocyclobutene (BCB) resin, polyimide (PI) resin, fluororesin, and epoxy resin.

19. The support substrate is made of silicon, sapphire, GaP, GaAs, InP, SiC, quartz, glass, LiTaO ３ , and LiNbO ３ 19. The method for producing a temporarily bonded wafer according to claim 11, wherein the temporarily bonded wafer is made of any one of the materials listed above.

20. 19. The method for producing a temporary bonded wafer according to claim 11, further comprising, after the step (2), a step (3) of removing the starting substrate from the epitaxial substrate.

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