Method for manufacturing a bonded light-emitting device wafer

Abstract

To provide a method of manufacturing a bonded light-emitting element wafer, reducing a stress at an interface with a light-emitting element structure that is fixed with a thermosetting bonding material and thereby suppressing the occurrence of peeling and cracks of the light-emitting element structure after a starting substrate has been removed.SOLUTION: In a method of manufacturing a bonded light-emitting element wafer, a light-emitting element structure having, as an active layer, (AlyGa1-y)xIn1-xP (0.4≤x≤0.6, 0≤y≤0.5), and a substrate that is transparent with respect to visible light and that is transparent with respect to ultraviolet light are bonded or adhered via a thermosetting bonding material that is transparent with respect to visible light and that absorbs ultraviolet light. In the method, the curing temperature of the thermosetting bonding material is increased by a step-by-step increase having three or more steps in a range of 120°C or more and 320°C or less, by a gradual increase, or by a combination thereof to cure the thermosetting bonding material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A technology for bonding wafers via BCB (benzocyclobutene) has been disclosed as a wafer for AlGaInP-based micro LEDs. BCB has excellent characteristics as an adhesive material, such as a small volume change rate after curing. Wafer bonding using BCB is described in, for example, Patent Documents 1 to 4.

[0003] However, this feature can be detrimental if the thermal expansion coefficient of the bonding and bonded wafers is greater than that of the BCB.

[0004] The following describes the case of bonding a sapphire substrate to an AlGaInP epitaxial wafer (a GaAs wafer is used as the starting substrate and an AlGaInP epitaxial layer is grown on it). The thermal expansion coefficient of sapphire is approximately 5.5 x 10 -6 [ / K], and the thermal expansion coefficient of GaAs, the starting substrate material for AlGaInP epitaxial wafers, is approximately 5.7 × 10 -6 When the BCB is thermally cured, the GaAs substrate, which is the material of the starting substrate for the AlGaInP epitaxial wafer, has a larger thermal expansion coefficient, so after the BCB thermal curing process, tensile stress is applied to the GaAs substrate relative to the BCB cured layer.

[0005] On the other hand, the thermal expansion coefficient of an AlGaInP epitaxial wafer is approximately 5.4 × 10 -6 [ / K]. When the AlGaInP epitaxial wafer is heated to the heating temperature during BCB thermal curing, the thermal expansion coefficient of the AlGaInP epitaxial wafer is smaller than that of GaAs, so tensile stress is applied to the epitaxial layer. Since the BCB is thermally cured while this tensile stress is still applied, the tensile stress remains fixed inside the epitaxial layer during curing.

[0006] Internally fixed stress can cause various problems. For example, it can cause cracks in the epitaxial layer after the BCB hardens and the starting substrate is removed. When the stress is compressive, the crystal lattice is distorted and cracks do not occur. However, semiconductors have a lower resistance to tensile stress than compressive stress, making them more susceptible to cracks.

[0007] This stress also creates a sliding force between the BCB and the epitaxial surface, which can easily cause damage to the adhesive surface between the BCB and the epitaxial layer, resulting in the epitaxial layer not being retained after the starting substrate is removed, leading to damage and peeling of the epitaxial layer.

[0008] This stress occurs when the temperature is lowered from the heat curing temperature to room temperature, so it can be reduced if the ambient temperature is high. However, since micro LEDs are not devices that are used while being heated, the method of reducing the internally fixed stress by using them at elevated ambient temperatures cannot be adopted.

[0009] Therefore, in order to prevent epitaxial layer peeling and cracks from occurring in the epitaxial layer, it is necessary to reduce the stress at the interface with the epitaxial layer fixed by BCB. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-246640 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-261510 [Patent Document 3] Special Publication No. 2009-537970 [Patent Document 4] Special Publication No. 2011-523383 Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been made to solve the above-mentioned problems, and aims to provide a method for manufacturing a bonded light-emitting element wafer that reduces stress at the interface with the light-emitting element structure fixed with a thermosetting bonding material, and suppresses peeling and cracking of the light-emitting element structure after removal of the starting substrate. [Means for solving the problem]

[0012] The present invention has been made to achieve the above object, and y Ga 1-y ) x In 1-x The present invention provides a method for manufacturing a bonded light-emitting element wafer, in which a light-emitting element structure having P(0.4≦x≦0.6, 0≦y≦0.5) as an active layer is bonded or adhered to a substrate that is transparent to visible light and transparent to ultraviolet light via a thermosetting bonding material that is transparent to visible light and absorbs ultraviolet light, wherein the curing temperature of the thermosetting bonding material is increased by a stepwise increase having three or more steps in the range of 120°C to 320°C, or by a gradual increase, or by a combination of these, to cure the thermosetting bonding material.

[0013] In this way, by increasing the curing temperature of the thermosetting bonding material in a stepwise manner having three or more steps in the range of 120°C or higher and 320°C or lower, or by a gradual increase, or by a combination thereof, the stress at the interface with the light-emitting element structure fixed by the thermosetting bonding material can be reduced, and peeling and cracking of the light-emitting element structure after the starting substrate is removed can be suppressed.

[0014] Furthermore, in the method for manufacturing a bonded light-emitting element wafer of the present invention, the stepwise increase in the curing temperature can be performed by carrying out at least two of the following processes after the first step: a first step of maintaining the temperature in a temperature range of 120°C or higher and 180°C or lower for a predetermined time; a second step of maintaining the temperature in a temperature range of more than 180°C and 220°C or lower for a predetermined time; a third step of maintaining the temperature in a temperature range of more than 220°C and 270°C or lower for a predetermined time; and a fourth step of maintaining the temperature in a temperature range of more than 270°C and 320°C or lower for a predetermined time.

[0015] By increasing the curing temperature stepwise in this manner, peeling and cracking of the light emitting element structure can be more reliably prevented.

[0016] In this case, the holding time of the first step process can be 30 minutes or more and 300 minutes or less, the holding time of the second step process can be 15 minutes or more and 200 minutes or less, the holding time of the third step process can be 5 minutes or more and 50 minutes or less, and the holding time of the fourth step process can be 1 minute or more and 30 minutes or less.

[0017] By setting the holding time in this range, it is possible to more reliably prevent peeling and cracking of the light emitting element structure.

[0018] Furthermore, in the method for manufacturing a bonded light-emitting element wafer of the present invention, the curing temperature can be continuously increased, and the average rate of temperature increase in the temperature range of 120°C or higher and 180°C or lower can be continuously increased at an average rate of temperature increase that is not more than half the average rate of temperature increase in the temperature range from above 180°C to the maximum curing temperature.

[0019] Such a gradual increase in the curing temperature of the thermosetting bonding material also makes it possible to more reliably prevent peeling and cracking of the light emitting element structure.

[0020] The thermosetting bonding material is preferably benzocyclobutene.

[0021] In the method for producing a bonded light-emitting element wafer of the present invention, benzocyclobutene (BCB) can be suitably used as a thermosetting bonding agent. [Effects of the Invention]

[0022] The manufacturing method of the bonded light-emitting element wafer of the present invention reduces stress at the interface with the light-emitting element structure fixed by the thermosetting bonding material, and can suppress peeling and cracking of the light-emitting element structure after removal of the starting substrate. [Brief explanation of the drawings]

[0023] [Figure 1] 3A to 3C are schematic cross-sectional views showing a part of a method for manufacturing a junction-type light-emitting element wafer according to the present invention. [Figure 2] 4 is a schematic cross-sectional view showing another part of the method for manufacturing a junction-type light-emitting element wafer according to the present invention. FIG. [Figure 3] 4 is a schematic cross-sectional view showing another part of the method for manufacturing a junction-type light-emitting element wafer according to the present invention. FIG. [Figure 4] 4 is a schematic cross-sectional view showing another part of the method for manufacturing a junction-type light-emitting element wafer according to the present invention. FIG. [Figure 5] 4 is a schematic cross-sectional view showing another part of the method for manufacturing a junction-type light-emitting element wafer according to the present invention. FIG. [Figure 6] 4 is a schematic cross-sectional view showing another part of the method for manufacturing a junction-type light-emitting element wafer according to the present invention. FIG. [Figure 7] 1 is a photograph of the wafer appearance of the junction-type light-emitting element wafer of Example 1. [Figure 8] 10 is a photograph of the wafer appearance of the junction-type light-emitting element wafer of Example 2. [Figure 9] 10 is a photograph of the wafer appearance of a bonded light-emitting device wafer of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will be described in detail below, but the present invention is not limited thereto.

[0025] The present invention relates to (Al y Ga 1-y ) x In 1-x A method for manufacturing a bonded light-emitting element wafer in which a light-emitting element structure having P(0.4≦x≦0.6, 0≦y≦0.5) as an active layer and a substrate that is transparent to visible light and transparent to ultraviolet light are bonded or adhered via a thermosetting bonding material that is transparent to visible light and absorbs ultraviolet light, characterized in that the curing temperature of the thermosetting bonding material is increased by a stepwise increase having three or more steps in the range of 120°C or more and 320°C or less, or by a gradual increase, or by a combination of these, to cure the thermosetting bonding material.

[0026] Hereinafter, aspects of the present invention will be described by way of examples of a first embodiment and a second embodiment with reference to the drawings. Also, some overlapping descriptions will be omitted.

[0027] [First embodiment] First, a first embodiment will be described. In this embodiment, the curing temperature of the thermosetting bonding material is increased stepwise in three or more stages within a range of 120°C or higher and 320°C or lower.

[0028] First, (Al y Ga 1-y ) x In 1-x A light emitting device structure having P (0.4≦x≦0.6, 0≦y≦0.5) as an active layer is prepared. To this end, as shown in FIG. 1, epitaxial growth is performed sequentially on a starting substrate 11 to form each layer, and an epitaxial wafer 20 is produced. This produces an etch stop layer 12 and an epitaxial layer having a light emitting device structure 18. More specifically, the epitaxial growth of each layer can be performed as follows.

[0029] As shown in Fig. 1, an etch stop layer 12 is epitaxially grown on a starting substrate 11 made of, for example, GaAs of the first conductivity type. The etch stop layer 12 can be formed, for example, by growing a GaAs buffer layer of the first conductivity type and then growing a first etch stop layer of In x P(0.4 ≦ x ≦ 0.6) with a thickness of, for example, 0.1 μm and a second etch stop layer of GaAs of the first conductivity type with a thickness of, for example, 0.1 μm. Further, on the etch stop layer 12, for example, a first cladding layer 13 of (Al y Ga 1-y ) x In 1-x P(0.4 ≦ x ≦ 0.6, 0 < y ≦ 1.0) with a thickness of, for example, 1.0 μm, an active layer 14 of undoped (Al y Ga 1-y ) x In 1-x P(0.4 ≦ x ≦ 0.6, 0 ≦ y ≦ 0.5), a second cladding layer 15 of (Al y Ga 1-y ) x In 1-x P(0.4 ≦ x ≦ 0.6, 0.6 ≦ y ≦ 1.0) with a thickness of, for example, 1.0 μm, an intermediate layer of GaInP of the second conductivity type (not shown) with a thickness of, for example, 0.1 μm, and a window layer 16 of GaP of the second conductivity type with a thickness of, for example, 4 μm are sequentially grown to prepare an epitaxial wafer 20 having a light-emitting element structure 18 as an epitaxial functional layer. Here, the portion from the AlGaInP first cladding layer 13 to the AlGaInP second cladding layer 15 is referred to as a double heterojunction (DH) structure portion (Fig. 1). Note that the material of the light-emitting element structure 18 is not limited to these, and any structure having a light-emitting element structure may be used. x In 1-x P(0.4 ≦ x ≦ 0.6) first etch stop layer with a thickness of, for example, 0.1 μm and a second etch stop layer of GaAs of the first conductivity type with a thickness of, for example, 0.1 μm can be formed by growth. Further, on the etch stop layer 12, for example, a first cladding layer 13 of (Al y Ga 1-y ) x In 1-x P(0.4 ≦ x ≦ 0.6, 0 < y ≦ 1.0) with a thickness of, for example, 1.0 μm, an active layer 14 of undoped (Al y Ga 1-y ) x In 1-x P(0.4 ≦ x ≦ 0.6, 0 ≦ y ≦ 0.5), a second cladding layer 15 of (Al y Ga 1-y ) x In 1-x P(0.4 ≦ x ≦ 0.6, 0.6 ≦ y ≦ 1.0) with a thickness of, for example, 1.0 μm, an intermediate layer of GaInP of the second conductivity type (not shown) with a thickness of, for example, 0.1 μm, and a window layer 16 of GaP of the second conductivity type with a thickness of, for example, 4 μm are sequentially grown to prepare an epitaxial wafer 20 having a light-emitting element structure 18 as an epitaxial functional layer. Here, the portion from the AlGaInP first cladding layer 13 to the AlGaInP second cladding layer 15 is referred to as a double heterojunction (DH) structure portion (Fig. 1). Note that the material of the light-emitting element structure 18 is not limited to these, and any structure having a light-emitting element structure may be used. y Ga 1-y ) x In 1-x P(0.4 ≦ x ≦ 0.6, 0 < y ≦ 1.0) first cladding layer 13 with a thickness of, for example, 1.0 μm, an active layer 14 of undoped (Al y Ga 1-y ) x In 1-x P(0.4 ≦ x ≦ 0.6, 0 ≦ y ≦ 0.5), a second cladding layer 15 of (Al y Ga 1-y ) x In 1-x P(0.4 ≦ x ≦ 0.6, 0.6 ≦ y ≦ 1.0) with a thickness of, for example, 1.0 μm, an intermediate layer of GaInP of the second conductivity type (not shown) with a thickness of, for example, 0.1 μm, and a window layer 16 of GaP of the second conductivity type with a thickness of, for example, 4 μm are sequentially grown to prepare an epitaxial wafer 20 having a light-emitting element structure 18 as an epitaxial functional layer. Here, the portion from the AlGaInP first cladding layer 13 to the AlGaInP second cladding layer 15 is referred to as a double heterojunction (DH) structure portion (Fig. 1). Note that the material of the light-emitting element structure 18 is not limited to these, and any structure having a light-emitting element structure may be used. y Ga 1-y ) x In 1-x P(0.4 ≦ x ≦ 0.6, 0 ≦ y ≦ 0.5) active layer 14, a second cladding layer 15 of (Al y Ga 1-y ) x In 1-x P(0.4 ≦ x ≦ 0.6, 0.6 ≦ y ≦ 1.0) with a thickness of, for example, 1.0 μm, an intermediate layer of GaInP of the second conductivity type (not shown) with a thickness of, for example, 0.1 μm, and a window layer 16 of GaP of the second conductivity type with a thickness of, for example, 4 μm are sequentially grown to prepare an epitaxial wafer 20 having a light-emitting element structure 18 as an epitaxial functional layer. Here, the portion from the AlGaInP first cladding layer 13 to the AlGaInP second cladding layer 15 is referred to as a double heterojunction (DH) structure portion (Fig. 1). Note that the material of the light-emitting element structure 18 is not limited to these, and any structure having a light-emitting element structure may be used. y Ga 1-y ) x In 1-x P(0.4 ≦ x ≦ 0.6, 0.6 ≦ y ≦ 1.0) second cladding layer 15 with a thickness of, for example, 1.0 μm, an intermediate layer of GaInP of the second conductivity type (not shown) with a thickness of, for example, 0.1 μm, and a window layer 16 of GaP of the second conductivity type with a thickness of, for example, 4 μm are sequentially grown to prepare an epitaxial wafer 20 having a light-emitting element structure 18 as an epitaxial functional layer. Here, the portion from the AlGaInP first cladding layer 13 to the AlGaInP second cladding layer 15 is referred to as a double heterojunction (DH) structure portion (Fig. 1). Note that the material of the light-emitting element structure 18 is not limited to these, and any structure having a light-emitting element structure may be used. <0000​​​​​​The active layer 14 may be made of a single composition, or may have a structure in which a plurality of barrier layers and active layers are alternately stacked, and both have similar functions, so either one can be selected.

[0032] Next, the Al prepared as above y Ga 1-y ) x In 1-x A light-emitting element structure 18 having P(0.4≦x≦0.6, 0≦y≦0.5) as an active layer and a substrate that is transparent to visible light and transparent to ultraviolet light (hereinafter, may be simply referred to as a "transparent substrate") are bonded or adhered via a thermosetting bonding material that is transparent to visible light and absorbs ultraviolet light.

[0033] Specifically, this bonding or adhesion can be performed as follows. As shown in Fig. 2, an epitaxial wafer 20 (light-emitting element structure 18) is spin-coated with, for example, benzocyclobutene (BCB) as a thermosetting bonding material 25, and then the epitaxial wafer 20 is placed face-to-face with a light-transmitting substrate (for example, a sapphire wafer) 30, which is the wafer to be bonded, and the two are thermocompression-bonded in a vacuum atmosphere. When applying BCB by spin coating, the designed film thickness can be, for example, 0.6 µm.

[0034] As described above, the thermosetting bonding material 25 between the two substrates is cured. Here, in the first embodiment, when the thermosetting bonding material 25 is thermally cured, the temperature is increased stepwise in three or more steps within a range of 120°C or higher and 320°C or lower.

[0035] More specifically, the stepwise increase in the curing temperature here can be carried out by first performing the first step, followed by performing at least two of the second step, third step, and fourth step, among which the temperature is maintained for a predetermined time in a temperature range of 120°C or higher and 180°C or lower, the second step, the third step, the fourth step, the temperature is maintained for a predetermined time in a temperature range of 220°C or higher and 270°C or lower, and the fourth step, the temperature is maintained for a predetermined time.

[0036] Furthermore, the holding time for the first step can be 30 minutes or more, the holding time for the second step can be 15 minutes or more, the holding time for the third step can be 5 minutes or more, and the holding time for the fourth step can be 1 minute or more. By doing so, for example, the curing rate can be 55% or less in the first step, more than 55% and less than 80% in the second step, more than 80% and less than 95% in the third step, and more than 95% in the fourth step. For example, if the first step to the third step are performed, the fourth step (a step at more than 270°C and less than 320°C) does not necessarily have to be performed.

[0037] The definition of the cure rate can be that described in Patent Document 2. The cure rate of the thermosetting bonding material 25 can be determined by analyzing the infrared absorption spectrum using an FT-IR device (Fourier Transform Infrared Spectrophotometer).

[0038] When BCB is used as the material for the thermosetting bonding material 25, the cyclobutene rings decrease as the curing progresses. Therefore, it is possible to determine the curing rate S by measuring the intensity of the spectral component corresponding to the cyclobutene rings from the infrared absorption spectrum. When BCB in a state not subjected to heat treatment is measured using an FT-IR device, the infrared absorption spectrum at a curing rate of 0% is obtained. From the infrared absorption spectrum at a curing rate of 0%, the intensity P1 of the spectral component corresponding to the cyclobutene rings is determined. On the other hand, when fully cured BCB is measured using an FT-IR device, the infrared absorption spectrum at a curing rate of 100% is obtained. From the infrared absorption spectrum at a curing rate of 100%, the intensity P2 of the spectral component corresponding to the cyclobutene rings is determined. Furthermore, when semi-cured BCB is measured using an FT-IR device, the infrared absorption spectrum of the semi-cured BCB is obtained. From the infrared absorption spectrum of this semi-cured BCB, the intensity P3 of the spectral component corresponding to the cyclobutene rings is determined. The curing rate S of this semi-cured BCB is then calculated as follows: S = [(P3 - P1) / (P2 - P1)] x 100(%) It is calculated by:

[0039] Here, the case where the curing rate of BCB is calculated based on the intensity of the spectral component corresponding to the cyclobutene ring has been described as an example, but the spectral component used to calculate the curing rate of the thermosetting bonding material 25 is not limited to the spectral component corresponding to the cyclobutene ring.

[0040] When BCB is used as the material for the thermosetting bonding material 25, as the curing proceeds, the cyclobutene rings decrease while the tetrahydronaphthalene rings increase. Therefore, the curing rate of BCB can also be determined by measuring the intensity of the spectral component corresponding to the tetrahydronaphthalene rings from the infrared absorption spectrum.

[0041] The upper limit of the holding time at each temperature can be set to 300 minutes or less for the first step, 200 minutes or less for the second step, 50 minutes or less for the third step, and 30 minutes or less for the fourth step. These times are suitable because they can sufficiently obtain the effects of the present invention and do not incur unnecessary costs.

[0042] More specifically, the first step may be performed at a set temperature of 150°C for 180 minutes (BCB cure rate of 35%). The second step may be performed at a set temperature of 200°C for 120 minutes. The third step may be performed at a set temperature of 250°C for 30 minutes. The fourth step may be performed at a set temperature of 300°C for 15 minutes.

[0043] Furthermore, as described above, it is not necessary to maintain a constant temperature in each step, and the temperature can be freely selected to be continuously increased or maintained at a constant temperature as long as it is within the temperature range of each step.

[0044] In this embodiment, a vacuum atmosphere is used, but the present invention is not limited to this atmosphere, and any atmosphere can be used as long as the oxygen concentration is 100 ppm or less. Similar effects can be obtained with a nitrogen atmosphere or an argon atmosphere.

[0045] The substrate to be bonded is not limited to a sapphire substrate, and any material can be selected as long as it is laser light transmissive and flat. In addition to sapphire, quartz can also be selected.

[0046] The thermosetting bonding material 25 such as BCB is not limited to being applied in a layer form. The same results can be obtained by patterning the thermosetting bonding material 25 such as photosensitive BCB into isolated islands, lines, or other shapes and then performing the bonding process.

[0047] Furthermore, the thickness of the BCB film is not limited to 0.6 μm, and the same effect can be obtained even if the thickness is thinner than this.

[0048] Furthermore, curing to over 95% is not necessarily required; a cure rate of 95% or less can be used as a product. In particular, in the case of micro LEDs bonded to a sapphire wafer, which is a UV-transparent and visible-light-transmitting support substrate, with UV-absorbing and visible-light-transmitting BCB, the micro LED and support substrate are ultimately separated and mounted at the BCB layer, so the BCB layer only needs to have a cure rate that is mechanically strong and chemically resistant enough to withstand the device process. Therefore, curing can be stopped at a cure rate of 80-95%, i.e., the fourth step does not necessarily have to be performed.

[0049] In addition, in order to carry out the device process of micro LEDs, it is preferable to set the BCB curing rate to 80% or more. In the present invention, the temperature is increased stepwise in a range of 120°C to 320°C in three or more steps, and in this case, it can be carried out in the form of a first step, a second step, and a third step, a first step, a third step, and a fourth step, or a first step, a second step, and a fourth step.

[0050] In this manner, a bonded light-emitting device wafer can be manufactured. The bonded light-emitting device wafer shown in FIG. 2 can be used for a micro LED structure having a light-emitting device structure. Furthermore, electrodes and the like for each element can be formed subsequently as follows.

[0051] As shown in FIG. 3, the starting substrate 11 is removed. More specifically, the process is as follows. When a GaAs substrate is used as the starting substrate 11, as in the above example, it is removed by wet etching using ammonia hydrogen peroxide (a mixed solution of ammonia and hydrogen peroxide). This exposes the GaInP first etch stop layer of the etch stop layer 12. Next, the etchant is switched to a hydrochloric acid-based etchant to selectively remove the GaInP first etch stop layer of the etch stop layer 12, exposing the GaAs second etch stop layer of the etch stop layer 12. Next, the etchant is switched to a sulfuric acid hydrogen peroxide-based etchant (a mixed solution of sulfuric acid and hydrogen peroxide) to selectively remove the GaAs second etch stop layer, exposing the first cladding layer 13. By performing the above processes, an epitaxial junction substrate retaining only the DH layer and window layer can be fabricated (FIG. 3).

[0052] Next, as shown in Figure 4, a pattern is formed by photolithography, and element isolation processing is performed by ICP (Inductively Coupled Plasma) (element isolation groove 47 in Figure 4). The gases used for ICP can be chlorine and argon. ICP processing is performed twice: once to expose the BCB layer (thermosetting bonding material 25) and once to expose the second cladding layer 15 or GaP window layer 16.

[0053] Although FIG. 4 shows an example in which the second cladding layer 15 is exposed, the same effect can be obtained even when the GaP window layer 16 is exposed.

[0054] 5, after the element isolation process, a protective film 52 is formed as an end surface treatment. The protective film 52 may be made of SiO2, SiNx, titanium oxide, magnesium oxide, or the like.

[0055] After forming the protective film 52, electrodes 54 and 56 are formed in contact with the first conductivity type layer and the second conductivity type layer, respectively, as shown in Fig. 6, and ohmic contacts are formed by performing heat treatment. If the first conductivity type is n-type and the second conductivity type is p-type, a metal containing Au and Si can be used for the electrode in contact with the n-type layer, and a metal containing Au and Be can be used for the electrode in contact with the p-type layer.

[0056] The n-type electrode is not limited to Au and Si, and similar results can be obtained by using a metal containing Au and Ge. The p-type electrode is not limited to Au and Be, and similar results can be obtained by using a metal containing Au and Zn.

[0057] Second Embodiment The second embodiment is the same as the first embodiment except for the step of thermally curing the thermosetting bonding material 25 such as BCB, and therefore the description of these steps will be omitted.

[0058] Unlike the first embodiment, the second embodiment does not thermally cure the thermosetting bonding material 25, such as the BCB layer, in a stepwise manner, but instead gradually increases the temperature. Preferably, the temperature increase rate increases as the temperature increases. More specifically, the curing temperature is continuously increased, and the average temperature increase rate in the temperature range of 120°C to 180°C is preferably equal to or less than half the average temperature increase rate in the temperature range from above 180°C to the maximum curing temperature. For example, the temperature may be gradually increased from 120°C to 180°C over 60 minutes, gradually increased from above 180°C to 220°C over 40 minutes, gradually increased from above 220°C to 270°C over 20 minutes, and gradually increased from above 270°C to 320°C over 10 minutes.

[0059] In this case, the average temperature rise rate from 120°C to 180°C is 1°C / min, and the average temperature rise rate from over 180°C to 320°C is 2°C / min, which is a faster average temperature rise rate in the high temperature region. In this way, it is preferable to raise the temperature so that the average temperature rise rate in the high temperature region is faster than that in the low temperature region.

[0060] Moreover, as in the first embodiment, the step at a temperature higher than 270°C and equal to or lower than 320°C does not necessarily have to be carried out. [Example]

[0061] EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0062] Example 1 A junction-type light-emitting device wafer was manufactured in accordance with the first embodiment.

[0063] First, as shown in FIG. 1, an n-type GaAs buffer layer is laminated on an n-type (first conductivity type) GaAs starting substrate 11, and then an n-type Ga x In 1-x A P (0.4≦x≦0.6) first etch stop layer was epitaxially grown to a thickness of 0.1 μm, and an n-type GaAs second etch stop layer was epitaxially grown to a thickness of 0.1 μm to form an 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 with a thickness of 1.0 μm and undoped (Al y Ga 1-y ) x In 1-x P(0.4≦x≦0.6, 0≦y≦0.5) active layer 14, p-type (Al y Ga 1-y ) x In 1-x P(0.4≦x≦0.6, 0.6≦y≦1.0) second cladding layer 15 with a thickness of 1.0 μm, p-type Ga x In 1-xA P(0.5≦x≦1.0) intermediate layer (not shown) was grown to a thickness of 0.1 μm, and a p-type GaP window layer 16 was grown in this order to prepare an epitaxial wafer 20 having a light emitting device structure 18 as an epitaxial functional layer (FIG. 1).

[0064] 2, benzocyclobutene (BCB) was spin-coated onto the epitaxial wafer 20 (on the light-emitting element structure 18) as a thermosetting bonding material 25, and then the epitaxial wafer 20 was placed face-to-face with a sapphire wafer (wafer to be bonded), which was a visible light transmissive substrate 30, and the two were thermocompression-bonded in a vacuum atmosphere. When applying BCB by spin coating, the designed film thickness was 0.6 μm.

[0065] Next, the BCB was thermally cured in a vacuum atmosphere. During thermal curing, the temperature was increased in stages as follows: In the first step, the set temperature was 150°C and the holding time was 180 minutes (BCB cure rate 35%). Next, in the second step, the set temperature was 200°C and held for 120 minutes. Next, in the third step, the set temperature was 250°C and held for 30 minutes. Next, in the fourth step, the set temperature was 300°C and held for 15 minutes, resulting in a cure rate of 98%.

[0066] Next, as shown in Figure 3, the GaAs starting substrate 11 was removed by wet etching using ammonia hydrogen peroxide (a mixed solution of ammonia and hydrogen peroxide) to expose the first etch-stop layer of the etch-stop layer 12, and the etchant was switched to remove the second etch-stop layer to expose the first cladding layer 13, thereby producing an epitaxial junction substrate retaining only the DH layer and window layer.

[0067] Next, as shown in Figure 4, a pattern was formed by photolithography, and element isolation processing was performed by ICP (element isolation groove 47). The gases used for ICP were chlorine and argon. ICP processing was performed twice: once to expose the BCB layer 25 and once to expose the second cladding layer 15.

[0068] After the element isolation process, as shown in FIG. 5, an SiO2 protective film 52 was formed as end face treatment.

[0069] After forming the protective film 52, electrodes 54 and 56 were formed in contact with the n-type layer and p-type layer, respectively, as shown in Fig. 6, and ohmic contacts were formed by heat treatment. A metal containing Au and Si was used for the electrode in contact with the n-type layer, and a metal containing Au and Be was used for the electrode in contact with the p-type layer.

[0070] Example 2 In Example 2, a bonded light-emitting device wafer was manufactured under the same conditions as in Example 1, except that the BCB layer was not thermally cured stepwise but rather the temperature was increased gradually as follows: The temperature was gradually increased from 120°C to 180°C over 60 minutes, then from 180°C to 220°C over 40 minutes, then from 220°C to 270°C over 20 minutes, and finally from 270°C to 320°C over 10 minutes to thermally cure the BCB.

[0071] (Comparative Example) A junction type light-emitting element wafer was manufactured under the same conditions as in Example 1, except that the BCB curing step was performed as a single-stage treatment at 250° C. for 1 hour.

[0072] Figures 7 and 8 show the appearance of the wafers after bonding in Examples 1 and 2, and Figure 9 shows the appearance of the wafer after bonding in the Comparative Example. When bonding was performed using the temperature profile of the Examples, no major bonding defects occurred, but when it was performed in the Comparative Example, bonding defects occurred in the outer periphery and the epitaxial layer peeled off significantly.

[0073] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0074] 11... Starting substrate; 12... Etch stop layer; 13...first cladding layer, 14...active layer, 15...second cladding layer, 16...window layer, 18...light emitting device structure, 20...epitaxial wafer, 25...Thermosetting bonding material, 30...Transparent substrate, 47...element isolation trench, 52...protective film, 54, 56...electrodes.

Claims

1. (Al ｙ Ga １－ｙ ) ｘ In １－ｘ a light-emitting device structure having P (0.4≦x≦0.6, 0≦y≦0.5) as an active layer; a substrate that is transparent to visible light and transparent to ultraviolet light; A method for manufacturing a bonded light-emitting element wafer in which bonding or adhesion is performed via benzocyclobutene, which is a thermosetting bonding material that is transparent to visible light and absorbs ultraviolet light, comprising: The curing temperature of the thermosetting bonding material is increased stepwise in a range of 120°C or more and 320°C or less, with three or more steps, A first step process of maintaining the temperature in the range of 120°C or higher and 180°C or lower for 30 minutes or longer and 300 minutes or shorter; A second step of maintaining the temperature in the range of more than 180°C and not more than 220°C for 15 minutes to 200 minutes; A third step of maintaining the temperature in a range of more than 220°C and not more than 270°C for 5 minutes to 50 minutes; A fourth step of maintaining the temperature in the range of more than 270°C and not more than 320°C for 1 minute or more and not more than 30 minutes; After the first step, A method for manufacturing a bonded light-emitting element wafer, characterized in that the temperature is raised by performing at least two of the second step process, the third step process, and the fourth step process, thereby hardening the thermosetting bonding material.

2. (Al ｙ Ga １－ｙ ) ｘ In １－ｘ a light-emitting device structure having P (0.4≦x≦0.6, 0≦y≦0.5) as an active layer; a substrate that is transparent to visible light and transparent to ultraviolet light; A method for manufacturing a bonded light-emitting element wafer in which bonding or adhesion is performed via benzocyclobutene, which is a thermosetting bonding material that is transparent to visible light and absorbs ultraviolet light, comprising: A method for manufacturing a bonded light-emitting element wafer, characterized in that the curing temperature of the thermosetting bonding material is continuously increased, and the average temperature rise rate in the temperature range of 120°C or higher and 180°C or lower is gradually increased at an average temperature rise rate of not more than 1 / 2 of the average temperature rise rate in the temperature range from above 180°C to the maximum curing temperature, thereby curing the thermosetting bonding material.

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