Method for removing bonding defects from a bonded wafer and method for manufacturing a bonded wafer.

Abstract

The present invention is a bonding defect removal method for a bonded wafer that is bonded to a transparent substrate by curing a thermosetting bonding member, said bonded wafer having a light-emitting element structure that has an active layer comprising (AlyGa1-y)xIn1-xP(0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5), and said transparent substrate transmitting light of a light-emitting wavelength, wherein the bonded wafer is introduced into a plasma atmosphere, and the defects of the thermosetting bonding member where curing is insufficient are removed by being selectively destroyed. Thus, there is provided a bonding defect removal method for a bonded wafer, said method making it possible to remove curing defects from a bonded wafer in which a transparent substrate and a light-emitting element structure that has an active layer of an AlGaInP type are bonded with a thermosetting bonding member interposed therebetween, without using techniques such as measuring or the like.

Description

[Technical Field]

[0001] The present invention relates to a method for removing bonding defects from a bonded wafer and a method for manufacturing a bonded wafer, and more particularly to a method for removing bonding defects from a bonded wafer having a light-emitting element structure and a method for manufacturing a bonded wafer. [Background technology]

[0002] To realize micro-light-emitting diode displays (micro-LED displays), a technique has been disclosed (Patent Document 1) in which an LED is detached from a starting substrate using laser lift-off (LLO), transferred to a mounting substrate, and then transferred to a drive substrate. However, all of these disclosures are for GaN-based LEDs only, and there are few technical disclosures regarding μ-LEDs using AlGaInP-based LEDs.

[0003] To realize micro-LED elements using AlGaInP-based LEDs via the LLO process, it is necessary to transfer them to a sapphire substrate. Prior art disclosures exist regarding the technology for transferring AlGaInP-based LEDs to a sapphire substrate, such as in Patent Document 2. However, there is no prior art disclosure regarding how to address the issue of partial curing failures.

[0004] Benzocyclobutene (BCB) does not cure sufficiently at the design temperature and time if oxygen is present during curing, resulting in curing failure. Therefore, curing is generally performed in a vacuum or nitrogen atmosphere. However, due to the nature of the process, which involves stacking and pressing two wafers together and then heating them, oxygen may remain at the bonding interface.

[0005] For example, if the surface is very uneven after BCB application and oxygen cannot be sufficiently removed before bonding, or if oxygen cannot be completely removed, residual oxygen will remain. This residual oxygen will cause poor crosslinking of the BCB, resulting in poor curing.

[0006] Although it is possible to inspect and identify the poorly cured portion of the BCB by means such as FTIR, etc., the poorly cured portion peels off one after another in the subsequent process, and the peeled fragments may damage the good portion or contaminate the apparatus. Therefore, it is necessary to remove the defective portion before feeding it into the subsequent process.

[0007] However, there is no prior art disclosure regarding the detection and removal of the poorly cured portion.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention has been made in view of the above problems, and in a bonded wafer in which a light-emitting element structure having an AlGaInP-based active layer and a transparent substrate are bonded via a thermosetting bonding member, a method for removing a bonding defect portion of the bonded wafer that can be removed without using a method such as measuring the poorly cured portion, and a method for manufacturing such a bonded wafer are provided.

Means for Solving the Problems

[0010] The present invention has been made to achieve the above object, and (Al y Ga 1-y ) x In 1-xThe present invention provides a method for removing bonding defects from a bonded wafer having a light-emitting element structure having an active layer made of P (0.4≦x≦0.6, 0≦y≦0.5), and bonded to a transparent substrate that transmits light of the emission wavelength by curing a thermosetting bonding member, characterized in that the bonded wafer is introduced into a plasma atmosphere and the bonding defects in which the thermosetting bonding member has not cured sufficiently are selectively destroyed and removed.

[0011] By introducing the bonded wafer into a plasma atmosphere and selectively destroying and removing the poorly bonded areas where hardening was insufficient, it becomes possible to remove the poorly bonded areas in a single process, eliminating the need for two or more steps such as detecting the poorly bonded areas and removing the detected areas.

[0012] In this case, it is preferable that the thermosetting bonding member be benzocyclobutene.

[0013] By using benzocyclobutene as a thermosetting bonding member, defective bonding areas can be removed more reliably.

[0014] Furthermore, it is preferable that the transparent substrate be sapphire or quartz.

[0015] These substrates can be suitably used as transparent substrates, and in particular, those with high transparency to the LLO laser can be selected.

[0016] Furthermore, it is preferable that the plasma atmosphere be a plasma generated by creating a plasma from one or more of the following gases: oxygen, nitrogen, argon, helium, and hydrogen, in a plasma generator having a barrel-type or parallel-plate electrode structure.

[0017] By using such a plasma atmosphere, defective parts can be removed more easily and reliably.

[0018] Furthermore, it is preferable that the apparatus for generating the plasma atmosphere be an RIE (Reactive Ion Etching) apparatus, an ICP (Inductively Coupled Plasma) apparatus, a plasma CVD apparatus, an ashing apparatus, or a sputtering apparatus.

[0019] Plasma generators like these can be suitably used as the apparatus for generating the atmosphere used in the present invention.

[0020] Furthermore, the present invention is (Al y Ga 1-y ) x In 1-x A method for manufacturing a bonded wafer is provided, comprising the steps of: preparing an epitaxial wafer having a light-emitting element structure having an active layer made of P (0.4≦x≦0.6, 0≦y≦0.5) and a transparent substrate that transmits light of the emission wavelength in the light-emitting element structure; and bonding the epitaxial wafer and the transparent substrate via a thermosetting bonding member and curing the thermosetting bonding member to form a bonded wafer, wherein after curing the thermosetting bonding member, the bonded wafer is introduced into a plasma atmosphere and selectively destroyed and removed any defective bonding portions where the thermosetting bonding member has not cured sufficiently.

[0021] This method for manufacturing bonded wafers involves introducing the bonded wafer, after the thermosetting bonding member has hardened, into a plasma atmosphere, and selectively destroying and removing any insufficiently hardened bonded areas. Therefore, it is a method for manufacturing bonded wafers that does not require two or more steps, such as detecting and removing the detected areas, and can remove bonded areas in a single process.

[0022] In this case, it is preferable that the thermosetting bonding member be benzocyclobutene.

[0023] By using benzocyclobutene as a thermosetting bonding member, it is possible to manufacture bonded wafers with more reliable removal of bonding defects.

[0024] Furthermore, it is preferable that the transparent substrate be sapphire or quartz.

[0025] These substrates can be suitably used as transparent substrates, and in particular, those with high transparency to the LLO laser can be selected.

[0026] Furthermore, it is preferable that the plasma atmosphere be a plasma generated by creating a plasma from one or more of the following gases: oxygen, nitrogen, argon, helium, and hydrogen, in a plasma generator having a barrel-type or parallel-plate electrode structure.

[0027] By using such a plasma atmosphere, it is possible to manufacture bonded wafers with defects removed more easily and reliably.

[0028] Furthermore, it is preferable that the apparatus for generating the plasma atmosphere be an RIE (Reactive Ion Etching) apparatus, an ICP (Inductively Coupled Plasma) apparatus, a plasma CVD apparatus, an ashing apparatus, or a sputtering apparatus.

[0029] In the method for manufacturing the bonded wafer of the present invention, plasma generators such as those described above can be suitably used as the apparatus for generating the plasma atmosphere. [Effects of the Invention]

[0030] The method for removing defective bonding portions of a bonded wafer of the present invention and the method for manufacturing a bonded wafer introduce a bonded wafer in which a light-emitting element structure having an AlGaInP-based active layer and a transparent substrate are bonded via a thermosetting bonding member into a plasma atmosphere, and remove the defective bonding portions with insufficient curing by selectively destroying them. Thus, more than two steps such as detection of defective bonding portions and removal of the detected locations are not required, and defective bonding portions can be removed in a single process. That is, since defective curing portions in the bonded wafer can be removed without using a method such as measurement, productivity is improved, and the yield of products such as micro LEDs manufactured from the bonded wafer is improved.

Brief Description of the Drawings

[0031] [Figure 1] FIG. 8 is a schematic cross-sectional view showing a part of a manufacturing process of a bonded wafer to which the method for removing defective bonding portions of a bonded wafer of the present invention is applied. [Figure 2] FIG. 11 is a schematic cross-sectional view showing another part of a manufacturing process of a bonded wafer to which the method for removing defective bonding portions of a bonded wafer of the present invention is applied. [Figure 3] FIG. 14 is a schematic cross-sectional view showing another part of a manufacturing process of a bonded wafer to which the method for removing defective bonding portions of a bonded wafer of the present invention is applied. [Figure 4] FIG. 17 is a graph showing the results in Examples and Comparative Examples.

Modes for Carrying Out the Invention

[0032] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0033] One aspect of the present invention is (Al y Ga 1-y ) x In 1-xA method for removing defective bonding portions of a bonded wafer having a light-emitting element structure having an active layer made of P (0.4≦x≦0.6, 0≦y≦0.5), and bonded to a transparent substrate that transmits light of the emission wavelength by curing a thermosetting bonding member, characterized in that the bonded wafer is introduced into a plasma atmosphere and the defective bonding portions where the curing of the thermosetting bonding member is insufficient are selectively destroyed and removed.

[0034] Another aspect of the present invention is (Al y Ga 1-y ) x In 1-x A method for manufacturing a bonded wafer, comprising the steps of: preparing an epitaxial wafer having a light-emitting element structure having an active layer made of P (0.4≦x≦0.6, 0≦y≦0.5) and a transparent substrate that transmits light of the emission wavelength in the light-emitting element structure; and bonding the epitaxial wafer and the transparent substrate via a thermosetting bonding member and curing the thermosetting bonding member to form a bonded wafer, wherein after curing the thermosetting bonding member, the bonded wafer is introduced into a plasma atmosphere and selectively destroyed and removed any poorly bonded portions of the thermosetting bonding member where curing was insufficient.

[0035] The present invention will be described in detail below with reference to the drawings, but the present invention is not limited thereto. Hereinafter, embodiments of the present invention will be described by illustrating the first to fourth embodiments.

[0036] (First embodiment) First, let me describe the first embodiment. The first embodiment is an example in which the plasma generator is used as an ashing device.

[0037] First, (Al y Ga 1-y ) x In 1-xA bonded wafer is prepared having a light-emitting element structure with an active layer made of P (0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5), and bonded to a transparent substrate that transmits light of the emission wavelength by curing a thermosetting bonding member. The preparation of such a bonded wafer is done by (Al y Ga 1-y ) x In 1-x This can be done by the steps of: preparing an epitaxial wafer having a light-emitting element structure with an active layer made of P (0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5); and a transparent substrate that transmits light of the emission wavelength in the light-emitting element structure; and bonding the epitaxial wafer and the transparent substrate via a thermosetting bonding member and curing the thermosetting bonding member to form a bonded wafer. Specifically, such a bonded wafer can be manufactured as follows.

[0038] First, as shown in Figure 1, an etch stop layer 12 is epitaxially grown on a starting substrate 11 made of, for example, GaAs of a first conductivity type. The etch stop layer 12 is made by, for example, stacking a GaAs buffer layer of a first conductivity type, followed by, for example, a GaAs buffer layer of a first conductivity type. x In 1-x A first etch stop layer of P(0.4≦x≦0.6) can be formed by growing it with a thickness of, for example, 0.1 μm, and a second etch stop layer of, for example, a first conductive type GaAs with a thickness of, for example, 0.1 μm. Furthermore, on the etch stop layer 12, a first conductive 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 is, for example, 1.0 μm thick, for example, undoped (Al y Ga 1-y ) x In 1-x P(0.4≦x≦0.6,0≦y≦0.5) Active layer 14, for example, 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 is, for example, 1.0 μm thick, second conductive type Gax In 1-x An epitaxial wafer 20 is prepared having a light-emitting element structure 18 as an epitaxial functional layer, for example, a GaP window layer 16 of the second conductivity type with a thickness of 0.1 μm, formed by sequentially growing a P(0.5≦x≦1.0) intermediate layer (not shown). Here, the first cladding layer 13 to the second cladding layer 15 are referred to as the double hetero (DH) structure (Figure 1).

[0039] The aforementioned film thickness is merely an example, and the film thickness should be changed depending on the operating specifications of the element; it is not limited to the film thickness described here. Although the first cladding layer 13 and the second cladding layer 15 are both shown as being 1.0 μm thick in the example, in micro-LEDs, the thickness is smaller than that of discrete LEDs with a high rated current density, and the function of the cladding layer is not impaired even if the film thickness is thinner than this.

[0040] Furthermore, since electrodes are formed in contact with the first cladding layer 13, it is preferable that the first cladding layer 13 has a thickness of 0.6 μm or more, taking into consideration metal diffusion during ohmic contact formation. A thickness greater than this is preferable, and any thickness can be selected. However, if it becomes too thick, it will increase costs and may lead to a decrease in luminescence efficiency during constant current driving, or a decrease in yield due to increased wafer warping. For this reason, it is preferable that this thickness be 10 μm or less.

[0041] Furthermore, when the second conductivity type is P-type, the effective mass of the holes is large, so even if the second cladding layer 15 is, for example, about 0.2 μm thick, it functions as if it were 1.0 μm thick. For this reason, a thickness of 0.2 μm or more is preferable, and any thickness can be selected. However, if it becomes too thick, it will increase costs and may lead to a decrease in luminescence efficiency during constant current driving, or a decrease in yield due to increased wafer warping. For this reason, it is preferable to keep this thickness at 10 μm or less.

[0042] Furthermore, each layer is not a single-composition layer, but conceptually includes having multiple composition layers within the exemplified range of compositions. Additionally, the carrier concentration levels are not uniform across each layer, but conceptually include having multiple levels within each layer.

[0043] The active layer 14 may be composed of a single composition, or it may be a superlattice structure in which multiple barrier layers and active layers 14 are alternately stacked, both of which have similar functions and can be selected. The effects of the present invention are the same regardless of which structure is selected.

[0044] Furthermore, the thickness of the GaP window layer is preferably greater than 5 μm, and can be, for example, 6 μm. However, it is not limited to this 6 μm thickness; for example, any thickness within the range of thickness thinner than the short side length of the element isolation can be selected.

[0045] Next, as shown in Figure 2, a thermosetting bonding member 25, such as benzocyclobutene (BCB), is spin-coated onto the epitaxial wafer 20, and the wafers are placed opposite a transparent substrate 30, such as a sapphire wafer, and then thermocompressed together under a vacuum atmosphere. When applying BCB by spin-coating, the film thickness can be, for example, 0.6 μm. In this way, the epitaxial wafer 20 and the transparent substrate 30 are bonded together via the thermosetting bonding member 25, and the bonding is achieved by curing the thermosetting bonding member 25 to form a bonded wafer.

[0046] Furthermore, the atmosphere used for heat bonding is not limited to a vacuum; any atmosphere with an oxygen concentration of 100 ppm or less can be used. For example, similar effects can be obtained in a nitrogen or argon atmosphere.

[0047] Furthermore, the transparent substrate 30 is not limited to sapphire; any material can be selected as long as it ensures laser light transmittance and flatness for LLO. In addition to sapphire, quartz can also be selected.

[0048] Furthermore, when using BCB as the thermosetting bonding member 25, similar results can be obtained not only by applying the BCB in layers, but also by using photosensitive BCB to pattern it into isolated island shapes, lines, or other shapes, and then performing the bonding process.

[0049] Furthermore, the thickness of the thermosetting bonding member 25, such as BCB, is not limited to 0.6 μm, and may be thinner than this thickness.

[0050] Next, as shown in Figure 3, the starting substrate 11 (e.g., a GaAs starting substrate) is removed by wet etching, and then the etch stop layer 12 is also removed. When the etch stop layer 12 has a first etch stop layer and a second etch stop layer as described above, the first etch stop layer can be exposed by etching, and then the etchant can be switched to remove the second etch stop layer and expose the epitaxial layer (the first cladding layer 13 of the light-emitting element structure 18). In this way, a bonded wafer can be fabricated that retains only the double hetero (DH) structure (first cladding layer 13, active layer 14, second cladding layer 15) and the window layer 16 (Figure 3).

[0051] After preparing the bonded wafer in this manner, the present invention introduces the bonded wafer into a plasma atmosphere and selectively destroys and removes the bonded defects where the thermosetting bonding member 25 has not hardened sufficiently. That is, after hardening the thermosetting bonding member 25, the bonded wafer is introduced into a plasma atmosphere and selectively destroys and removes the bonded defects where the thermosetting bonding member 25 has not hardened sufficiently. In this way, a bonded wafer can be manufactured in which the bonded defects where the thermosetting bonding member 25 has not hardened sufficiently have been selectively destroyed. At this time, it is preferable that the plasma atmosphere be a plasma generated by creating a plasma from a gas containing one or more of oxygen, nitrogen, argon, helium, and hydrogen in a plasma generator having a barrel-type or parallel-plate electrode structure. Furthermore, in the present invention, the device that generates the plasma atmosphere can be an RIE (Reactive Ion Etching) device, an ICP (Inductively Coupled Plasma) device, a plasma CVD device, an ashing device, or a sputtering device. In the first embodiment, an example in which the plasma generator is an ashing device will be described.

[0052] The pressure of the plasma atmosphere can be reduced to, for example, 100 [Pa], and oxygen can be introduced at a rate of, for example, 100 sccm, and the atmosphere in which the oxygen plasma is generated is held for, for example, 5 minutes. Similar effects can be obtained by introducing a mixture of one or more gases other than oxygen, such as nitrogen, argon, helium, or hydrogen, and performing plasma treatment. However, the mixture of oxygen and hydrogen is excluded from the above gases.

[0053] The plasma conditions described above are merely examples and are not limited to the aforementioned figures. The pressure can be higher or lower than the example pressure, and can be freely set between, for example, 5 and 150 Pa. The gas flow rate is also a design element for plasma generation density, and similar effects can be obtained with a flow rate higher or lower than the example flow rate, as long as the pressure control allows.

[0054] When the above plasma treatment is applied, the plasma causes charge-up / heating in the poorly cured areas of the thermosetting bonding member 25, such as BCB, causing the poorly cured areas to expand and vaporize. As a result, both the thermosetting bonding member with the poor curing (e.g., the defective BCB layer) and the epitaxial layer on the poorly cured area peel off from the bonding substrate, and the defective area is removed.

[0055] After plasma treatment, the wafer can be cleaned as appropriate. For example, the wafer can be rotated while applying a plasma at a rate of, for example, 5 kg / cm². 2 An organic solvent is sprayed at pressure to remove the peeled BCB and epitaxial layer adhering to the surface, followed by pure water washing and spin drying.

[0056] (Second Embodiment) Next, a second embodiment will be described. The second embodiment is an example in which the plasma generator is a plasma generator having a parallel plate structure. The process and structure for manufacturing the bonded wafer are the same as in the first embodiment.

[0057] The bonded wafer is introduced into a plasma generator having a parallel plate structure, and plasma processing is performed in a reduced-pressure atmosphere. In this embodiment, the plasma generator is an RIE apparatus, an ICP apparatus, or another apparatus having a parallel plate structure. Although dry etching processing using an ICP apparatus is performed in a subsequent process to form the element shape, the plasma processing of the present invention is performed before the subsequent process, as described above.

[0058] The reduced pressure atmosphere can be, for example, 1.0 [Pa], and defects are removed by introducing, for example, 50 sccm of oxygen and generating an oxygen plasma for treatment. Similar effects can be obtained by introducing a mixture of one or more of the following gases: nitrogen, argon, helium, or hydrogen, and performing plasma treatment. However, a mixture of oxygen and hydrogen is excluded from this method.

[0059] Furthermore, similar effects can be obtained by introducing reactive gases other than those mentioned above, such as chlorine-based or fluorine-based gases. However, in the case of these reactive gases, etching of the surface of the light-emitting structure proceeds even with a weak plasma, so it is preferable to use the gases mentioned above.

[0060] The plasma conditions are merely examples and are not limited to the aforementioned figures. The pressure can be higher or lower than the example pressure, and can be freely set between, for example, 0.1 and 10 Pa. The gas flow rate is also a design element for plasma generation density, and similar effects can be obtained with a flow rate higher or lower than the example flow rate, as long as the pressure control allows.

[0061] After plasma treatment, the wafer is rotated while applying a plasma flow rate of, for example, 5 kg / cm². 2 An organic solvent is sprayed at pressure to remove the peeled BCB and epitaxial layer adhering to the surface, followed by pure water washing and spin drying.

[0062] (Third embodiment) Next, a third embodiment will be described. The third embodiment is an example in which the plasma generator is a plasma CVD apparatus. The process and structure for manufacturing the bonded wafer are the same as in the first embodiment.

[0063] The bonded wafer is introduced into a plasma CVD apparatus, and defects are removed by plasma deposition in a reduced-pressure atmosphere.

[0064] The reduced pressure atmosphere can be, for example, 5.0 [Pa], and a film of SiO2 is deposited by introducing, for example, 20 sccm of TEOS (tetraethooxylan) and for example, 50 sccm of oxygen. Note that the film deposition is not limited to SiO2 films; similar effects can be obtained by depositing other silicon-containing films such as SiNx, phosphosilicate glass (PSG), and oxynitride (SiNxOx).

[0065] The plasma conditions are merely examples and are not limited to the numbers mentioned above. Since pressure is a parameter that determines the film deposition rate, similar effects can be obtained whether the pressure is higher or lower than the example pressure. For example, it can be freely set between 0.1 and 10 Pa. The gas flow rate is also a design element of the plasma generation density, i.e., a parameter of the film deposition rate, and similar effects can be obtained whether the flow rate is higher or lower than the example flow rate, as long as the pressure control allows.

[0066] After film formation, the film can be removed by etching. For example, after forming an SiO2 film, the SiO2 film can be removed by wet etching with a hydrofluoric acid-based solution.

[0067] (Fourth embodiment) Next, a fourth embodiment will be described. The fourth embodiment is an example in which the plasma generator is a sputtering apparatus. The process and structure for manufacturing the bonded wafer are the same as in the first embodiment.

[0068] The bonded wafer is introduced into a sputtering apparatus, and defects are removed by sputtering film deposition in a reduced-pressure atmosphere.

[0069] The reduced pressure atmosphere can be set to, for example, 2.0 [Pa], and an SiO2 film is deposited by irradiating the SiO2 target with RF plasma. Note that the deposition is not limited to SiO2 films; similar effects can be obtained by depositing other wet-etchable films such as Ti, Al, TiO2, ZnO, NbOx, SiNx, and TiNx.

[0070] The plasma conditions are merely examples and are not limited to the aforementioned figures. Since pressure is a parameter that determines the film deposition rate, similar effects can be obtained whether the pressure is higher or lower than the example pressure. For example, it can be freely set between 0.1 and 10 Pa. The gas flow rate is also a design element of the plasma generation density, i.e., a parameter of the film deposition rate, and similar effects can be obtained whether the flow rate is higher or lower than the example flow rate, as long as the pressure control allows.

[0071] After film formation, the film can be removed by etching. For example, after forming an SiO2 film, the SiO2 film can be removed by wet etching with a hydrofluoric acid-based solution. [Examples]

[0072] The present invention will be described in detail below with reference to examples and comparative examples, but these are not intended to limit the present invention.

[0073] (Example 1) First, as shown in Figure 1, an epitaxial wafer having a light-emitting element structure as the epitaxial functional layer was prepared. Specifically, the following was done: First, an n-type GaAs buffer layer was stacked on an n-type GaAs starting substrate 11, followed by a 0.1 μm thick n-type GaAs buffer layer. x In 1-x A first etch stop layer of P(0.4≦x≦0.6) and a second etch stop layer of n-type GaAs with a thickness of 0.1 μm were formed to form the etch stop layer 12. A 1.0 μm thick n-type (Al) layer was formed on top of the etch stop layer 12. y Ga 1-y ) x In 1-x P(0.4≦x≦0.6,0.6≦y≦1.0) First cladding layer 13, undoped (Al y Ga 1-y ) x In 1-x P(0.4≦x≦0.6,0≦y≦0.5) Active layer 14, 1.0 μm thick 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, 0.1 μm thick p-type Ga x In 1-x An epitaxial wafer 20 having a light-emitting element structure as an epitaxial functional layer was prepared by sequentially growing a P(0.5≦x≦1.0) intermediate layer (not shown) and a 0.6 μm thick p-type GaP window layer 16 (Figure 1).

[0074] Next, as shown in Figure 2, benzocyclobutene (BCB) was spin-coated onto the epitaxial wafer 20 as a thermosetting bonding member 25, and the wafer was placed opposite the transparent substrate 30, a sapphire wafer, and thermocompressed under a vacuum atmosphere. When applying the BCB by spin-coating, the designed film thickness was set to 0.6 μm.

[0075] Next, as shown in Figure 3, the GaAs starting substrate 11 was removed by wet etching to expose the n-type first etch stop layer. The etchant was then switched to remove the second etch stop layer, exposing the first cladding layer and removing the etch stop layer 12. This resulted in the fabrication of an epitaxial junction substrate that retains only the DH layer and the window layer 16.

[0076] The bonded wafer was introduced into an ashing apparatus having a barrel structure, and plasma treatment was performed by introducing 100 sccm of oxygen in a reduced pressure atmosphere of 100 [Pa] and holding it in an atmosphere that generated oxygen plasma for 5 minutes. In this way, a bonded wafer was manufactured in which the bonded defective parts of the thermosetting bonding member 25 with insufficient curing were selectively destroyed.

[0077] After plasma atmosphere treatment, the wafer is rotated while applying a pressure of 5 kg / cm². 2 An organic solvent was sprayed to remove the delaminate BCB and epitaxial layer adhering to the surface, followed by pure water washing and spin drying to remove any defective bonding areas from the bonded wafer. Subsequently, as a post-processing step, dry etching was performed using an ICP apparatus to form the element shape, and the degree of delamination of the epitaxial layer during the dry etching process was investigated.

[0078] (Example 2) The preparation of the bonded wafer shown in Figure 3 was carried out in the same manner as in Example 1. This bonded wafer was introduced into an RIE apparatus having a parallel plate structure, and plasma treatment was performed in an atmosphere where oxygen plasma was generated by introducing 50 sccm of oxygen in a reduced pressure atmosphere of 1.0 [Pa], except that the bonded defective parts of the bonded wafer were removed under the same conditions as in Example 1. In addition, the delamination of the epitaxial layer during the dry etching process was investigated, as in Example 1.

[0079] (Example 3) The preparation of the bonded wafer shown in Figure 3 was carried out in the same manner as in Example 1. This bonded wafer was introduced into a plasma CVD apparatus, and a SiO2 film was deposited by introducing 20 sccm of TEOS and 50 sccm of oxygen in a reduced pressure atmosphere of 5.0 [Pa]. After film deposition, the SiO2 film was removed by wet etching with a hydrofluoric acid-based solution. The bonded defective parts of the bonded wafer were removed under the same conditions as in Example 1. In addition, the delamination of the epitaxial layer during the dry etching process was investigated, as in Example 1.

[0080] (Example 4) The preparation of the bonded wafer shown in Figure 3 was carried out in the same manner as in Example 1. This bonded wafer was introduced into a sputtering apparatus, and an SiO2 film was formed by irradiating an SiO2 target with RF plasma in a reduced pressure atmosphere of 2.0 [Pa]. After film formation, the SiO2 film was removed by wet etching with a hydrofluoric acid-based solution. The bonded defective parts of the bonded wafer were removed under the same conditions as in Example 1. In addition, the delamination of the epitaxial layer during the dry etching process was investigated, as in Example 1.

[0081] (Comparative example) Except for not performing plasma treatment, a bonded wafer was fabricated in the same manner as in Example 1. Then, as a post-processing step, dry etching was performed using an ICP apparatus to form the element shape without performing plasma treatment, and the peeling status of the epitaxial layer during the dry etching process was investigated.

[0082] (Comparison of Examples and Comparative Examples) Figure 4 shows a comparison of the percentage of epitaxial layer delamination area during the subsequent ICP treatment in the examples and comparative examples. Although the occurrence rate is not constant because the degree of residual oxygen is not constant, in the examples, plasma treatment is performed before feeding the material into the subsequent ICP treatment to remove defective parts, so it can be seen that no new epitaxial layer delamination occurs during the subsequent ICP treatment.

[0083] Furthermore, it is possible to measure the BCB curing rate using methods such as FTIR and identify areas of curing defects, and if the only goal is to detect areas of curing defects, alternative methods are available without using this technology. However, it is difficult to remove the defective areas inexpensively after they have been identified. BCB curing defects are irregular in shape, and if one attempts to identify the area to be removed using a photolithography method, for example, with a photomask, it is necessary to prepare a mask each time, which incurs considerable costs. In addition, selecting a different removal method after identifying the location using a measurement method increases processing time and costs compared to this technology. In the present invention, the identification and removal of defective areas are completed in one step, making it a quick and simple method.

[0084] This specification includes the following embodiments: [1]:(Al y Ga 1-y ) x In 1-x A method for removing a bonding defect from a bonded wafer having a light-emitting element structure having an active layer made of P (0.4≦x≦0.6, 0≦y≦0.5), and bonded to a transparent substrate that transmits light of the emission wavelength by curing a thermosetting bonding member, characterized in that the bonded wafer is introduced into a plasma atmosphere and the bonding defect, in which the curing of the thermosetting bonding member is insufficient, is selectively destroyed and removed. [2]: A method for removing a defective bond from the bonded wafer of [1], wherein the thermosetting bonding member is benzocyclobutene. [3]: A method for removing a bonding defect from a bonded wafer according to [1] or [2] above, wherein the transparent substrate is sapphire or quartz. [4]: A method for removing a bonding defect from a bonded wafer according to [1], [2], or [3], wherein the plasma atmosphere is a plasma generated in a plasma generator having a barrel-type or parallel-plate electrode structure, containing one or more gases that include oxygen, nitrogen, argon, helium, and hydrogen. [5]: A method for removing a bonding defect from a bonded wafer according to [1], [2], [3], or [4] above, wherein the apparatus for generating the plasma atmosphere is an RIE (Reactive Ion Etching) apparatus, an ICP (Inductively Coupled Plasma) apparatus, a plasma CVD apparatus, an ashing apparatus, or a sputtering apparatus. [6]: (Al y Ga 1-y ) x In 1-x A step of preparing an epitaxial wafer having a light-emitting element structure having an active layer made of P (0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5), and a transparent substrate that transmits light of the emission wavelength in the light-emitting element structure, The process involves bonding the epitaxial wafer and the transparent substrate via a thermosetting bonding member, and then curing the thermosetting bonding member to form a bonded wafer. A method for manufacturing a bonded wafer, comprising: A method for manufacturing a bonded wafer, characterized by comprising the step of curing the thermosetting bonding member, then introducing the bonded wafer into a plasma atmosphere, and selectively destroying and removing the bonded defective portions of the thermosetting bonding member where curing was insufficient. [7]: A method for manufacturing the bonded wafer according to [6], wherein the thermosetting bonding member is benzocyclobutene. [8]: A method for manufacturing a bonded wafer according to [6] or [7], wherein the transparent substrate is sapphire or quartz. [9]: The method for manufacturing a bonded wafer according to [6], [7], or [8] above, wherein the plasma atmosphere is a plasma generated in a plasma generator having a barrel-type or parallel-plate electrode structure, containing one or more gases that include oxygen, nitrogen, argon, helium, and hydrogen.

[10] : A method for manufacturing a bonded wafer according to [6], [7], [8] or [9], wherein the apparatus for generating the plasma atmosphere is an RIE (Reactive Ion Etching) apparatus, an ICP (Inductively Coupled Plasma) apparatus, a plasma CVD apparatus, an ashing apparatus, or a sputtering apparatus.

[0085] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention.

Claims

1. (Al ｙ Ga １－ｙ ) ｘ In １－ｘ A method for removing a bonding defect in a bonded wafer having a light-emitting element structure having an active layer made of P (0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5), and bonded to a transparent substrate that transmits light of the emission wavelength by curing a thermosetting bonding member, A method for removing a defective bond from a bonded wafer, characterized by introducing the bonded wafer into a plasma atmosphere and selectively destroying and removing the defective bond portion where the curing of the thermosetting bonding member is insufficient.

2. The method for removing a defective bond from a bonded wafer according to claim 1, characterized in that the thermosetting bonding member is benzocyclobutene.

3. The method for removing a bonding defect in a bonded wafer according to claim 1 or 2, characterized in that the transparent substrate is sapphire or quartz.

4. The method for removing a bonding defect from a bonded wafer according to claim 1 or 2, characterized in that the plasma atmosphere is created by generating a plasma of one or more gases containing oxygen, nitrogen, argon, helium, and hydrogen in a plasma generator having a barrel-type or parallel plate-type electrode structure.

5. The method for removing a defective bond from a bonded wafer according to claim 1 or 2, characterized in that the apparatus for generating the plasma atmosphere is an RIE (Reactive Ion Etting) apparatus, an ICP (Inductively Coupled Plasma) apparatus, a plasma CVD apparatus, an ashing apparatus, or a sputtering apparatus.

6. (Al ｙ Ga １－ｙ ) ｘ In １－ｘ A step of preparing an epitaxial wafer having a light-emitting element structure having an active layer made of P (0.4 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5), and a transparent substrate that transmits light of the emission wavelength in the light-emitting element structure, The process involves bonding the epitaxial wafer and the transparent substrate via a thermosetting bonding member, and then curing the thermosetting bonding member to form a bonded wafer. A method for manufacturing a bonded wafer, comprising: A method for manufacturing a bonded wafer, characterized by comprising the step of curing the thermosetting bonding member, then introducing the bonded wafer into a plasma atmosphere, and selectively destroying and removing the bonded defective portions of the thermosetting bonding member where curing was insufficient.

7. The method for manufacturing a bonded wafer according to claim 6, characterized in that the thermosetting bonding member is benzocyclobutene.

8. The method for manufacturing a bonded wafer according to claim 6 or 7, characterized in that the transparent substrate is sapphire or quartz.

9. The method for manufacturing a bonded wafer according to claim 6 or 7, characterized in that the plasma atmosphere is created by generating a plasma of one or more gases containing oxygen, nitrogen, argon, helium, and hydrogen in a plasma generator having a barrel-type or parallel plate-type electrode structure.

10. The method for manufacturing a bonded wafer according to claim 6 or 7, characterized in that the apparatus for generating the plasma atmosphere is an RIE (Reactive Ion Etting) apparatus, an ICP (Inductively Coupled Plasma) apparatus, a plasma CVD apparatus, an ashing apparatus, or a sputtering apparatus.

Images