JP7779213B2 - Method for manufacturing a bonded light-emitting device wafer - Google Patents

Description

The present invention relates to a method for manufacturing a bonded light-emitting device wafer.

Technology for bonding wafers via BCB (benzocyclobutene) has been disclosed for AlGaInP-based micro-LED wafers. 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.

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

This section describes the case of bonding a sapphire substrate and an AlGaInP epitaxial wafer (a GaAs wafer is used as the starting substrate, and an AlGaInP epitaxial layer, etc., is grown on it). The thermal expansion coefficient of sapphire is approximately 5.5×10 ⁻⁶ [/K], while the thermal expansion coefficient of GaAs, the material of the starting substrate for the AlGaInP epitaxial wafer, is approximately 5.7×10 ⁻⁶ [/K]. When the BCB is thermally cured, since the thermal expansion coefficient of GaAs, the material of the starting substrate for the AlGaInP epitaxial wafer, is larger, after the BCB thermal curing process, tensile stress is applied to the GaAs substrate relative to the BCB cured layer.

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

Internal stress can cause a variety of problems. For example, after the BCB hardens and the starting substrate is removed, it can cause cracks in the epitaxial layer. 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 cracking.

This stress also creates a sliding force between the BCB and the epitaxial surface. This makes it easy for the adhesive surface between the BCB and the epitaxial layer to break, and the epitaxial layer is not retained after the starting substrate is removed, making it more likely that the epitaxial layer will break or peel off.

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 higher. However, because micro-LEDs are not devices that are used while heated, the method of reducing the internally fixed stress by using them at an elevated ambient temperature cannot be used.

Therefore, in order to prevent epitaxial layer delamination and cracks from occurring in the epitaxial layer, it is necessary to reduce the stress at the interface with the epitaxial layer, which is fixed with BCB.

Japanese Patent Application Laid-Open No. 2002-246640 Japanese Patent Application Laid-Open No. 2006-261510 Special Publication No. 2009-537970 Special Publication No. 2011-523383

The present invention was 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 removing the starting substrate.

The present invention has been made to achieve the above-mentioned object, and provides a method for manufacturing a bonded light-emitting element wafer in which a light-emitting element structure having ( _{AlyGa1 -y} ) _{xIn1 -xP} (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 to 320°C, or by a gradual increase, or by a combination of these, to cure the thermosetting bonding material.

In this way, by increasing the curing temperature of the thermosetting bonding material in three or more stages within the range of 120°C or higher and 320°C or lower, or by gradually increasing the temperature, or by a combination of these, the stress at the interface with the light-emitting element structure fixed by the thermosetting bonding material is reduced, and peeling or cracking of the light-emitting element structure after removal of the starting substrate can be suppressed.

In addition, 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 in which the temperature is maintained in a temperature range of 120°C or higher and 180°C or lower for a predetermined time; a second step in which the temperature is maintained in a temperature range of more than 180°C and 220°C or lower for a predetermined time; a third step in which the temperature is maintained in a temperature range of more than 220°C and 270°C or lower for a predetermined time; or a fourth step in which the temperature is maintained in a temperature range of more than 270°C and 320°C or lower for a predetermined time.

By gradually increasing the curing temperature in this manner, peeling and cracking of the light-emitting element structure can be more reliably prevented.

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

By setting the holding time in this manner, peeling and cracking of the light-emitting element structure can be more reliably prevented.

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 increased continuously at an average rate of temperature increase that is no more than half the average rate of temperature increase in the temperature range from above 180°C to the maximum curing temperature.

By gradually increasing the curing temperature of this thermosetting bonding material, peeling and cracking of the light-emitting element structure can be more reliably prevented.

It is also preferable that the thermosetting bonding material be benzocyclobutene.

In the manufacturing method of the bonded light-emitting element wafer of the present invention, benzocyclobutene (BCB) can be suitably used as a thermosetting bonding agent.

The method for manufacturing a 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 prevent peeling and cracking of the light-emitting element structure after removing the starting substrate.

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. 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. 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. 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. 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. 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. 1 is a photograph of the wafer appearance of the junction-type light-emitting element wafer of Example 1. 10 is a photograph of the wafer appearance of the junction-type light-emitting element wafer of Example 2. 10 is a photograph of the wafer appearance of a bonded light-emitting device wafer of a comparative example.

The present invention is described in detail below, but is not limited to these.

The present invention provides a method for manufacturing a bonded light-emitting element wafer in which a light-emitting element structure having ( _{AlyGa1 -y} ) _{xIn1 -xP} (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 to 320°C, or by a gradual increase, or by a combination of these, to cure the thermosetting bonding material.

The following describes aspects of the present invention, illustrating a first and second embodiment, with reference to the drawings. Some overlapping descriptions will be omitted.

[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.

First, a light-emitting device structure having ( _{AlyGa1 -y} ) _{xIn1 -} xP (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.

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 can be formed, for example, by stacking a GaAs buffer layer of the first conductivity type, and then growing a first etch stop layer of Ga _x In _1-x P (0.4≦x≦0.6) of the first conductivity type to a thickness of, for example, 0.1 μm, and a second etch stop layer of GaAs of the first conductivity type to a thickness of, for example, 0.1 μm. Further, on the etch stop layer 12, for example, a first conductive type (Al _y Ga _1-y ) _x In _1-x P (0.4≦x≦0.6, 0<y≦1.0) first cladding layer 13 is formed to a thickness of, for example, 1.0 μm, a non-doped (Al _y Ga _1-y ) _x In _1-x P (0.4≦x≦0.6, 0≦y≦0.5) active layer 14, a second conductive type (Al _y Ga _1-y ) _x In _1-x An epitaxial wafer 20 is prepared, which has a light-emitting device structure 18 as an epitaxial functional layer, formed by sequentially growing an AlGaInP (0.4≦x≦0.6, 0.6≦y≦1.0) second cladding layer 15 having a thickness of, for example, 1.0 μm, a second-conductivity-type GaInP intermediate layer (not shown) having a thickness of, for example, 0.1 μm, and a second-conductivity-type GaP window layer 16 having a thickness of, for example, 4 μm. Here, the layers from the AlGaInP first cladding layer 13 to the AlGaInP second cladding layer 15 are referred to as a double heterostructure (DH) ( FIG. 1 ). Note that the material of the light-emitting device structure 18 is not limited to these, and any material having a light-emitting device structure may be used.

The above-mentioned film thicknesses are merely examples, and are merely parameters that may be changed depending on the device's operating specifications, and are not limited to the film thicknesses described here. Furthermore, each layer may not be a single-composition layer, but may have multiple composition layers within the composition ranges shown as examples. Furthermore, the carrier concentration level may not be uniform in each layer, but may have multiple levels within each layer.

The active layer 14 may be composed of a single composition, or may have a structure in which multiple barrier layers and active layers are alternately stacked, as both have similar functions and either can be selected.

Next, the light-emitting element structure 18 having the thus prepared ( _{AlyGa1 -y} ) _{xIn1 -} xP (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.

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

The thermosetting bonding material 25 between the two substrates is cured as described above. In the first embodiment, when thermally curing the thermosetting bonding material 25, the temperature is increased in three or more stages within the range of 120°C or higher and 320°C or lower.

More specifically, the stepwise increase in the curing temperature here can be achieved by first performing the first step, followed by raising the temperature by performing at least two of the second, third, and fourth steps, of the following: a first step in which the temperature is maintained in the range of 120°C to 180°C for a predetermined time; a second step in which the temperature is maintained in the range of more than 180°C to 220°C for a predetermined time; a third step in which the temperature is maintained in the range of more than 220°C to 270°C for a predetermined time; and a fourth step in which the temperature is maintained in the range of more than 270°C to 320°C for a predetermined time.

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 to third steps are performed, the fourth step (a step at more than 270°C and less than 320°C) does not necessarily have to be performed.

The definition of the cure rate can be found 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).

When BCB is used as the material for the thermosetting bonding material 25, the number of cyclobutene rings decreases as the curing progresses. Therefore, it is possible to determine this by measuring the intensity of the spectral component corresponding to the cyclobutene ring from the infrared absorption spectrum. When BCB in an unheat-treated state is measured using an FT-IR device, the infrared absorption spectrum at a cure rate of 0% is obtained. From the infrared absorption spectrum at a cure rate of 0%, the intensity _P1 of the spectral component corresponding to the cyclobutene ring is determined. On the other hand, when a fully cured BCB is measured using an FT-IR device, the infrared absorption spectrum at a cure rate of 100% is obtained. From the infrared absorption spectrum at a cure rate of 100%, the intensity _P2 of the spectral component corresponding to the cyclobutene ring is determined. Furthermore, when a 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 such semi-cured BCB, the intensity _P3 of the spectral component corresponding to the cyclobutene ring is determined. The curing rate S of such semi-cured BCB is:
S=[(P ₃ - P ₁ )/(P ₂ - _{P 1} )]×100(%)
It is calculated by:

Note that, while the example described here uses the intensity of the spectral component corresponding to the cyclobutene ring to determine the cure rate of BCB, the spectral component used to calculate the cure rate of the thermosetting bonding material 25 is not limited to the spectral component corresponding to the cyclobutene ring.

When BCB is used as the material for the thermosetting bonding material 25, as the curing process progresses, the amount of cyclobutene rings decreases while the amount of tetrahydronaphthalene rings increases. 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.

Furthermore, 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 fully achieve the effects of the present invention and do not incur unnecessary costs.

More specifically, the first step can be, for example, a set temperature of 150°C and a holding time of 180 minutes (BCB cure rate of 35%). The second step can be, for example, a set temperature of 200°C and a holding time of 120 minutes. The third step can be, for example, a set temperature of 250°C and a holding time of 30 minutes. The fourth step can be, for example, a set temperature of 300°C and a holding time of 15 minutes.

Furthermore, as mentioned above, it is not necessary to maintain a constant temperature in each step, and as long as it is within the temperature range for each step, it is possible to freely choose to continuously increase the temperature or maintain a constant temperature.

In this embodiment, a vacuum atmosphere is used, but this is not limited to this atmosphere; any atmosphere with an oxygen concentration of 100 ppm or less can be used. Similar effects can be obtained with a nitrogen or argon atmosphere.

Furthermore, the substrate to be bonded is not limited to a sapphire substrate; any material can be selected as long as it ensures laser light transparency and flatness. In addition to sapphire, quartz can also be selected.

Furthermore, the thermosetting bonding material 25 such as BCB is not limited to being applied in a layer. Similar results can be obtained by using a photosensitive thermosetting bonding material 25 such as BCB to pattern it into isolated islands, lines, or other shapes and then performing the bonding process.

Furthermore, the BCB film thickness is not limited to 0.6 μm; similar effects can be obtained even with a thickness thinner than this.

Furthermore, curing to over 95% is not necessarily required; a cure rate of 95% or less will still be viable as a product. In particular, in the case of micro-LEDs bonded to a sapphire wafer, which serves as a UV-transparent and visible-light-transparent support substrate, using a UV-absorbing and visible-light-transparent 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 device processing. Therefore, curing can be stopped at a cure rate of 80-95%, meaning that the fourth step does not necessarily have to be performed.

Furthermore, in order to carry out the device process for micro LEDs, it is preferable to achieve a BCB cure rate of 80% or more. In the present invention, the temperature is increased in a stepwise manner having three or more steps within the range of 120°C to 320°C, and this can be carried out in the form of a first step process, a second step process, and a third step process, a first step process, a third step process, and a fourth step process, or a first step process, a second step process, and a fourth step process.

In this manner, a bonded light-emitting device wafer can be manufactured. The bonded light-emitting device wafer shown in Figure 2 can be used for a micro LED structure having a light-emitting device structure. Electrodes and other components for each device can then be formed as follows:

As shown in Figure 3, the starting substrate 11 is removed. More specifically, the process is as follows. If a GaAs substrate is used as the starting substrate 11, as in the example above, 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 solution 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 solution (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 (Figure 3).

Next, as shown in Figure 4, a pattern is formed using photolithography, and element isolation processing is performed using 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.

Figure 4 shows an example in which the second cladding layer 15 is exposed, but the same effect can be achieved when the GaP window layer 16 is exposed.

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 SiO ₂ , SiNx, titanium oxide, magnesium oxide, or the like.

After forming the protective film 52, electrodes 54, 56 are formed in contact with the first conductivity type layer and the second conductivity type layer, respectively, as shown in Figure 6, and heat treatment is performed to form ohmic contacts. 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.

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

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.

Unlike the first embodiment, the second embodiment does not thermally cure the thermosetting bonding material 25, such as a BCB layer, in a stepwise manner, but instead gradually increases the temperature. At this time, it is preferable to increase the heating rate as the temperature increases. More specifically, it is preferable to continuously increase the curing temperature, and to continuously increase the heating rate in the temperature range of 120°C to 180°C at an average heating rate of no more than half the average heating rate in the temperature range from above 180°C to the maximum curing temperature. For example, the temperature can 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.

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 above 180 to 320°C is 2°C/min, meaning the average temperature rise rate in the high temperature region is faster. 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.

Furthermore, as with the first embodiment, it is not necessary to perform the process at temperatures above 270°C and below 320°C.

The present invention will be explained in detail below using examples and comparative examples, but these are not intended to limit the scope of the present invention.

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

First, as shown in FIG. 1, an n-type GaAs buffer layer was deposited on an n-type (first conductivity type) GaAs starting substrate 11, and then an n-type Ga _x In _1-x P (0.4≦x≦0.6) first etch stop layer with a thickness of 0.1 μm and an n-type GaAs second etch stop layer with a thickness of 0.1 μm were epitaxially grown to form etch stop layer 12. Further, an n-type ( _{AlyGa1 -y} ) _{xIn1 -xP} (0.4≦x≦0.6, 0.6≦y≦1.0) first cladding layer 13 is formed to a thickness of 1.0 μm, a non-doped ( _{AlyGa1 -y} ) _{xIn1 -} xP (0.4≦x≦0.6, 0≦y≦0.5) active layer 14 is formed, a p-type ( _{AlyGa1 -y} ) _{xIn1 -xP} (0.4≦x≦0.6, 0≦y≦1.0) second cladding layer 15 is formed to a thickness of 1.0 μm, and a p-type _{GaxIn1 -x} A 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).

Next, as shown in Figure 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 placed face-to-face on a sapphire wafer (wafer to be bonded), which is a visible light-transmitting substrate 30, and thermocompression bonded in a vacuum atmosphere. When applying the BCB by spin coating, the designed film thickness was 0.6 μm.

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, achieving a cure rate of 98%.

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. The etchant was then switched to remove the second etch stop layer, exposing the first cladding layer 13, producing an epitaxial junction substrate retaining only the DH layer and window layer.

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.

After the element isolation process, as shown in FIG. 5, a SiO ₂ protective film 52 was formed as end surface treatment.

After forming the protective film 52, as shown in Figure 6, electrodes 54 and 56 were formed in contact with the n-type layer and p-type layer, respectively, 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.

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.

(Comparative Example)
A bonded 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.

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 wafers after bonding in the Comparative Example. When bonding was performed using the temperature profile of the Example, no major bonding defects occurred, but when performed in the Comparative Example, bonding defects occurred at the outer periphery and the epitaxial layer peeled off significantly.

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 concept described in the claims of the present invention and exhibits similar effects is within the technical scope of the present invention.

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

Claims (2)

A light emitting device structure having an active layer of ( _{AlyGa1 -y} ) _{xIn1 -xP} (0.4≦x≦0.6, 0≦y≦0.5),
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. A light emitting device structure having an active layer of ( _{AlyGa1 -y} ) _{xIn1 -xP} (0.4≦x≦0.6, 0≦y≦0.5),
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.