JP2011061084A - Method for manufacturing laminated substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a laminated substrate, which, when implanting ions on the major surface of a group III nitride semiconductor substrate, hardly damages the major surface. <P>SOLUTION: The method for manufacturing the laminated substrate 10, includes the steps of: forming a protective film 4 on the major surface 2a of the group III nitride semiconductor substrate 2; forming a vulnerable area f in the group III nitride semiconductor substrate 2 by implanting ions on the major surface 2a of the group III nitride semiconductor substrate 2 through the protective film 4; laminating the major surface 2a of the group III nitride semiconductor substrate 2 on a support substrate 6; and a part 2c of the group III nitride semiconductor substrate 2 is peeled from the support substrate 6 using the vulnerable area f as a boundary. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a bonded substrate.

  A method of forming a GaN layer on a silicon substrate by bonding a GaN substrate and a silicon substrate is known (see Patent Document 1). In this method, first, hydrogen and nitrogen ions are implanted into the surface of the GaN substrate by ion implantation. Thereafter, the ion-implanted surface of the GaN substrate and the silicon substrate are bonded together. Further, the GaN substrate is peeled from the silicon substrate with a fragile layer formed near the surface of the GaN substrate by ion implantation as a boundary. In this way, a GaN layer is formed on the silicon substrate.

JP 2006-210660 A

  However, in the above-described method, since ions are directly incident on the surface of the GaN substrate during ion implantation, the surface of the GaN substrate is damaged. As a result, the crystal quality of the GaN layer formed on the silicon substrate deteriorates, so that the characteristics of the device formed using this GaN layer deteriorate. Further, depending on the atomic species of the ion implantation, a crater-like recess is formed on the surface of the GaN substrate, so that there is a possibility that the bonding cannot be performed.

  The present invention has been made in view of the above circumstances, and provides a method for manufacturing a bonded substrate in which when the main surface of a group III nitride semiconductor substrate is ion-implanted, the main surface is not easily damaged. With the goal.

  In order to solve the above-mentioned problems, a method for manufacturing a bonded substrate according to the present invention includes a step of forming a protective film on a main surface of a group III nitride semiconductor substrate, and the group III nitride semiconductor substrate through the protective film. The step of forming a fragile region in the group III nitride semiconductor substrate by ion implantation into the main surface, the step of bonding the main surface of the group III nitride semiconductor substrate to a support substrate, and the boundary of the fragile region And removing a part of the group III nitride semiconductor substrate from the support substrate.

  According to the method for manufacturing a bonded substrate of the present invention, the protective film protects the main surface of the group III nitride semiconductor substrate while ions are implanted into the main surface of the group III nitride semiconductor substrate. Therefore, the main surface of the group III nitride semiconductor substrate is not easily damaged by ion implantation.

  The protective film preferably includes at least one of an oxide film, a nitride film, and a metal film.

  The method for manufacturing a bonded substrate includes planarizing the surface of the protective film between the step of forming the fragile region and the step of bonding the main surface of the group III nitride semiconductor substrate to the support substrate. It is preferable that the main surface of the group III nitride semiconductor substrate is bonded to the support substrate through the protective film.

  In this case, even if the surface roughness of the protective film is increased by ion implantation, the bonding strength between the surface of the protective film and the support substrate can be increased.

  The method for manufacturing a bonded substrate includes a step of removing the protective film between the step of forming the fragile region and the step of bonding the main surface of the group III nitride semiconductor substrate to the support substrate. Furthermore, it is preferable to include.

  In this case, the main surface of the group III nitride semiconductor substrate and the support substrate can be directly bonded.

  ADVANTAGE OF THE INVENTION According to this invention, when ion-implanting to the main surface of a group III nitride semiconductor substrate, the manufacturing method of the bonded substrate which the said main surface cannot easily receive a damage is provided.

It is process sectional drawing which shows typically the manufacturing method of the bonded substrate board which concerns on 1st Embodiment. It is process sectional drawing which shows typically the manufacturing method of the bonded substrate board which concerns on 2nd Embodiment. It is sectional drawing which shows an example of the semiconductor device produced using a bonded substrate board. It is sectional drawing which shows an example of the semiconductor device produced using a bonded substrate board. It is a figure which shows the result of cross-sectional TEM observation.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are used for the same or equivalent elements, and duplicate descriptions are omitted.

FIG. 1 is a process cross-sectional view schematically showing the method for manufacturing a bonded substrate according to the first embodiment. Hereinafter, a method for manufacturing the bonded substrate 10 will be described with reference to FIG.
(Protective film formation process)

  First, as shown in FIG. 1A, the protective film 4 is formed on the main surface 2 a of the group III nitride semiconductor substrate 2. Before forming protective film 4, main surface 2a of group III nitride semiconductor substrate 2 may be polished. The protective film 4 is formed by, for example, a plasma CVD method or a sputtering method. In this case, a dense film can be formed. The growth temperature of the protective film 4 is 400 ° C., for example. The thickness of the protective film 4 is 100 nm, for example.

  The group III nitride semiconductor substrate 2 is, for example, a gallium nitride (GaN) substrate or an AlN substrate. Main surface 2a of group III nitride semiconductor substrate 2 is preferably a (0001) plane. The main surface 2a of the group III nitride semiconductor substrate 2 is, for example, an N surface, but may be a group III surface (Ga surface, Al surface, etc.). The thickness of group III nitride semiconductor substrate 2 is preferably 100 to 2000 μm. The main surface 2a of the group III nitride semiconductor substrate 2 and the surface opposite to the main surface 2a are preferably mirror-polished, and the surface roughness Ra of each surface is preferably 5 nm or less.

The protective film 4 is preferably made of a material that can withstand a temperature of 1000 ° C. or higher. The protective film 4 preferably includes at least one of an oxide film, a nitride film, and a metal film. When the protective film 4 is an oxide film or a nitride film, processing of the film surface is facilitated, and voids are hardly generated at the interface when hydrophilic bonding or the like is used in the bonding process. The oxide film and the nitride film are preferably polycrystalline or amorphous. Examples of the oxide film include films made of SiO ₂ , TiO ₂ , ZrO _{2, and the} like. Examples of the nitride film include films made of Si ₃ N ₄ , TiN, or the like. Examples of the metal film include a conductive film made of a refractory metal such as Mo, W, Ti, or Pt. In this case, it is convenient to manufacture a vertical device (for example, see FIG. 4).
(Ion implantation process)

Subsequently, as shown in FIG. 1B, a weak region f is formed in the group III nitride semiconductor substrate 2 by ion implantation into the main surface 2 a of the group III nitride semiconductor substrate 2 through the protective film 4. To do. The fragile region f is formed at a predetermined depth (for example, 2 μm) from the main surface 2 a of the group III nitride semiconductor substrate 2. When the ion beam IB enters the group III nitride semiconductor substrate 2, the fragile region f is formed. In ion implantation, for example, ions such as hydrogen, helium, and nitrogen are used. The dose of ion implantation is preferably 5 × 10 ¹⁶ to 1 × 10 ¹⁸ ions / cm ² , more preferably 1 × 10 ¹⁷ to 1 × 10 ¹⁸ ions / cm ² , and the acceleration voltage is 80 to It is preferably 200 keV. The ion implantation angle (the angle formed between the normal line of the main surface 2a and the incident direction of the ion beam IB) is preferably 0 to 10 °. When the implantation angle is 0 °, the incident direction of the ion beam IB is parallel to the normal line of the main surface 2a. The temperature during ion implantation is preferably 50 to 200 ° C.

When the implantation angle is set to 0 °, the distribution of the implantation is normally expanded in the depth direction by channeling. Therefore, when a high dose region is formed in a specific region, the substrate is often tilted. However, when the substrate is tilted, damage to the substrate tends to be greater than when the implantation angle is 0 °. If the protective film 4 is polycrystalline or amorphous, the ion beam IB is scattered in various directions in a pseudo manner during ion implantation. For this reason, even if the implantation angle is set to 0 °, the same effect as that obtained when the main surface 2 a is inclined is obtained, and most of the energy is absorbed by the protective film 4. Therefore, the damage which the group III nitride semiconductor substrate 2 receives at the time of ion implantation can be reduced.
(Protective film removal process)

Subsequently, as shown in FIG. 1C, the protective film 4 may be removed as necessary. For example, the protective film 4 can be wet etched using hydrofluoric acid or the like.
(Lamination process)

  Subsequently, as shown in FIG. 1 (d), the main surface 2 a of the group III nitride semiconductor substrate 2 is bonded to the support substrate 6. Support substrate 6 is preferably made of a material different from group III nitride semiconductor substrate 2, a material that can withstand a high temperature of 1000 ° C. or higher, and a material that can withstand a gas such as ammonia or hydrogen. The support substrate 6 is, for example, a Si substrate, a SiC substrate, a sapphire substrate, or the like.

In the bonding process, for example, a method of bonding by heating while applying a load with the bonding surface as a mirror surface, a method of bonding by exposing the bonding surface to plasma, plasma, ions, neutral particles, etc. in vacuum It is possible to use a method of pasting together by increasing the reactivity of the surface by striking with the use of. Alternatively, a method in which a metal is interposed in the bonding interface and eutectic bonding is performed by heating, or a method in which a material that easily moves ions is interposed in the bonding interface may be used.
(Peeling process)

  Subsequently, as shown in FIG. 1 (e), by applying energy, a part 2 c of the group III nitride semiconductor substrate 2 is peeled from the support substrate 6 with the fragile region f as a boundary. As a result, a group III nitride semiconductor layer 2 b which is a part of the group III nitride semiconductor substrate 2 is formed on the support substrate 6. Examples of the method of applying energy include a method of heat-treating the substrate, applying a force to the substrate, and irradiating the substrate with light.

  The bonded substrate 10 can be manufactured through the above steps. According to the method for manufacturing a bonded substrate according to the present embodiment, the protective film 4 protects the main surface 2a of the group III nitride semiconductor substrate 2 while the ions are implanted into the main surface 2a of the group III nitride semiconductor substrate 2. ing. Therefore, main surface 2a of group III nitride semiconductor substrate 2 is not easily damaged by ion implantation (for example, dislocation such as loop dislocation, crystal distortion, etc.). Moreover, since it can suppress that a crater-shaped recessed part is formed in the main surface 2a of the group III nitride semiconductor substrate 2, it becomes easy to bond at the time of bonding. Further, the inside of the group III nitride semiconductor substrate 2 is not easily damaged by ion implantation. Therefore, a high-quality group III nitride semiconductor layer 2b is obtained. If a device is manufactured using such a bonded substrate 10, device characteristics can be improved.

  When the protective film removing step is performed, the main surface 2a of the group III nitride semiconductor substrate 2 and the support substrate 6 can be directly bonded.

  FIG. 2 is a process cross-sectional view schematically showing the method for manufacturing a bonded substrate according to the second embodiment. Hereinafter, a method for manufacturing the bonded substrate 10a will be described with reference to FIGS.

First, similarly to the first embodiment, the protective film forming step shown in FIG. 1A and the ion implantation step shown in FIG. 1B are performed in this order.
(Planarization process)

Subsequently, as shown in FIG. 2A, the surface 4a of the protective film 4 may be planarized as necessary. For example, it can planarize by grind | polishing the surface 4a using abrasives, such as colloidal silica.
(Lamination process)

Subsequently, as shown in FIG. 2B, the main surface 2 a of the group III nitride semiconductor substrate 2 is bonded to the support substrate 6 through the protective film 4. As a bonding method, the same method as in the first embodiment can be used.
(Peeling process)

  Subsequently, as shown in FIG. 2C, by applying energy, a part 2c of the group III nitride semiconductor substrate 2 is separated from the support substrate 6 with the weak region f as a boundary. As a result, a group III nitride semiconductor layer 2 b which is a part of the group III nitride semiconductor substrate 2 is formed on the protective film 4. As a peeling method, the same method as in the first embodiment can be used.

  The bonded substrate 10a can be manufactured through the above steps. In the method for manufacturing a bonded substrate according to the present embodiment, the same effects as those of the method for manufacturing a bonded substrate according to the first embodiment can be obtained.

  When the planarization step is performed, the bonding strength between the surface 4a of the protective film 4 and the support substrate 6 can be increased even if the surface roughness on the surface 4a of the protective film 4 is increased by ion implantation.

  FIG. 3 is a cross-sectional view illustrating an example of a semiconductor device manufactured using the bonded substrate 10. The semiconductor optical device 100 shown in FIG. 3 is, for example, an LED, an LD, or the like. The semiconductor optical device 100 includes a first conductivity type group III nitride semiconductor layer 12 provided on the group III nitride semiconductor layer 2b of the bonded substrate 10, and a surface of the first conductivity type group III nitride semiconductor layer 12. A group III nitride semiconductor layer 14, a group III nitride semiconductor layer 16, a light emitting layer 18, a second conductivity type group III nitride semiconductor layer 20, and a second conductivity type group III nitride provided in this order on the first region And a semiconductor layer 22. An electrode 24 is provided on a second region adjacent to the first region on the surface of the first conductivity type group III nitride semiconductor layer 12. An electrode 26 is provided on the second conductivity type group III nitride semiconductor layer 22.

  For example, the first conductivity type group III nitride semiconductor layer 12 is an n-type GaN layer, the group III nitride semiconductor layer 14 is a GaN layer, the group III nitride semiconductor layer 16 is an AlGaN layer, and the light emitting layer 18 has a multiple quantum well structure. The second conductivity type group III nitride semiconductor layer 20 is a p-type AlGaN layer, and the second conductivity type group III nitride semiconductor layer 22 is a p-type GaN layer. First conductivity type group III nitride semiconductor layer 12, group III nitride semiconductor layer 14, group III nitride semiconductor layer 16, light emitting layer 18, second conductivity type group III nitride semiconductor layer 20, second conductivity type group III The nitride semiconductor layer 22 is formed by, for example, the MBE method, the MOCVD method, or the like.

  Since the semiconductor optical device 100 is fabricated using the bonded substrate 10 having the high-quality group III nitride semiconductor layer 2b, it has good device characteristics.

  FIG. 4 is a cross-sectional view illustrating an example of a semiconductor device manufactured using the bonded substrate 10. A semiconductor electronic device 100a shown in FIG. 4 is, for example, a Schottky barrier diode. The semiconductor electronic device 100 a includes a group III nitride semiconductor device layer 30 provided on the group III nitride semiconductor layer 2 b of the bonded substrate 10. An electrode 32 is provided on the group III nitride semiconductor device layer 30. An electrode 34 is provided on the back surface of the support substrate 6, and the bonded substrate 10 and the group III nitride semiconductor device layer 30 are sandwiched between the electrodes 32 and 34. For example, the group III nitride semiconductor device layer 30 is a GaN device layer.

  Since the semiconductor electronic device 100a is fabricated using the bonded substrate 10 having the high-quality group III nitride semiconductor layer 2b, it has good device characteristics.

  As mentioned above, although preferred embodiment of this invention was described in detail, this invention is not limited to the said embodiment. For example, a semiconductor device as shown in FIGS. 3 and 4 may be manufactured using the bonded substrate 10a.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.
Example 1

Both surfaces of a 2 inch GaN wafer (thickness 500 μm) doped with oxygen were polished to form mirror surfaces. The GaN wafer is made of hexagonal GaN, and the main surface of the GaN wafer is a (0001) plane. The specific resistance of the GaN wafer is 1 Ω · cm or less, and the carrier concentration is 1 × 10 ¹⁷ cm ⁻³ or more.

A SiO ₂ film having a thickness of 100 nm was formed on one main surface (N surface) of the GaN wafer. Thereafter, hydrogen ions were implanted into the N surface through the SiO ₂ film. The acceleration voltage was 90 keV, and the dose was 6 × 10 ¹⁷ / cm ² .

Thereafter, the GaN wafer was divided into four, and a cross-sectional TEM observation of one of the GaN substrates was performed. The results are shown in FIG. As shown in FIG. 5A, the thickness d1 of damage caused by hydrogen ion implantation was 10 nm. The damage thickness d1 is preferably 15 nm or less. Note that the film visible on the SiO ₂ film in FIG. 5A is formed at the time of ion implantation because it is formed at the time of TEM sample preparation.
(Comparative Example 1)

The experiment was performed in the same manner as in Example 1 except that the SiO ₂ film was not formed. It should be noted that ion implantation was simultaneously performed on the GaN wafer of Example 1 and the GaN wafer of Comparative Example 1. The result of cross-sectional TEM observation is shown in FIG. As shown in FIG. 5B, the thickness d2 of damage caused by hydrogen ion implantation was 60 nm. Note that the film visible on the damaged region in FIG. 5B is formed at the time of ion implantation because it is formed at the time of manufacturing the TEM sample.

When Example 1 was compared with Comparative Example 1, it was found that the thickness of damage caused by hydrogen ion implantation was reduced by forming the SiO ₂ film.
(Example 2)

Instead of the SiO ₂ film, a polycrystalline Al ₂ O ₃ film having a thickness of 100 nm is formed by RF magnetron sputtering, and the GaN wafer into which hydrogen ions are implanted is divided into two instead of four. The experiment was conducted. As a result of cross-sectional TEM observation, the thickness of damage caused by hydrogen ion implantation was as good as 15 nm. The surface roughness Ra of the polycrystalline Al ₂ O ₃ film formed on the main surface of the GaN wafer was 2.4 nm.
(Example 3)

A GaN substrate obtained by dividing the GaN wafer of Example 1 into four was bonded to a sapphire substrate. Specifically, first, a support substrate was obtained by forming a SiO ₂ film having a thickness of 100 nm on a sapphire substrate and exposing the surface of the SiO ₂ film to plasma generated by discharge in Ar gas. . On the other hand, in the dry etching apparatus, the surface of the SiO ₂ film of the GaN substrate was exposed to plasma generated by discharge in Ar gas. Then, a SiO ₂ film of the SiO ₂ film and the GaN substrate of the supporting substrate were bonded with each other in the atmosphere. Note that the RF power for generating plasma was 100 W, the Ar gas flow rate was 50 sccm, and the pressure in the chamber was 6.7 Pa.

  Subsequently, in order to increase the bonding strength between the support substrate and the GaN substrate and to exfoliate a part of the GaN substrate with a weak region formed inside the GaN substrate by ion implantation as a boundary, at 300 ° C. in nitrogen for 2 hours. Heating was performed. Thus, a bonded substrate having a GaN layer formed on the support substrate was obtained.

Next, using the MOCVD method, an n-type GaN layer, a light emitting layer (In _0.2 Ga _0.8 N layer and Al _0.2 Ga _0.8 N layer), and a p-type GaN layer are formed on the exposed GaN layer. Were grown in this order to form an electrode, thereby producing an LED.
(Comparative Example 2)

An experiment was conducted in the same manner as in Example 3 except that a GaN substrate obtained by dividing the GaN wafer of Comparative Example 1 into four parts was used instead of the GaN substrate obtained by dividing the GaN wafer of Example 1 into four parts. Went. That is, an LED was manufactured using a GaN substrate obtained by performing hydrogen ion implantation without forming a SiO ₂ film.

The emission intensity at the peak wavelength of 450 nm of the emission spectrum of the LED obtained in Example 3 is 1.31 times higher than the emission intensity at the peak wavelength of 450 nm of the emission spectrum of the LED obtained in Comparative Example 2. I understood that. Accordingly, it was shown that it is preferable to form a SiO ₂ film and perform hydrogen ion implantation.
Example 4

The SiO ₂ film of the GaN substrate obtained by dividing the GaN wafer of Example 1 into four parts was removed, and the GaN substrate was bonded to the Si substrate. Specifically, the support substrate was obtained by first removing the natural oxide film of the Si substrate with hydrofluoric acid and exposing the hydrogen-terminated surface to plasma generated by discharge in Ar gas. On the other hand, the N surface of the GaN substrate was exposed to plasma generated by discharge in Ar gas in a dry etching apparatus. Then, the hydrogen-terminated surface of the support substrate and the N surface of the GaN substrate were bonded together in the atmosphere. Note that the RF power for generating plasma was 100 W, the Ar gas flow rate was 50 sccm, and the pressure in the chamber was 6.7 Pa.

  Subsequently, in order to increase the bonding strength between the support substrate and the GaN substrate and to exfoliate a part of the GaN substrate with a weak region formed inside the GaN substrate by ion implantation as a boundary, at 300 ° C. in nitrogen for 2 hours. Heating was performed. Thus, a bonded substrate having a GaN layer formed on the support substrate was obtained.

Next, an n-type GaN layer having a thickness of 5 μm was grown on the exposed GaN layer by MOCVD. The carrier concentration of the n-type GaN layer was 7 × 10 ¹⁵ cm ⁻³ .

  Next, the surface of the n-type GaN layer was surface-treated with an aqueous hydrochloric acid solution (hydrochloric acid: pure water = 1: 1) at room temperature for 1 minute. Thereafter, a Schottky electrode was formed by forming a gold film on the surface of the n-type GaN layer by resistance heating vapor deposition. The surface shape of the Schottky electrode was a circle having a diameter of 200 μm. In this way, a Schottky barrier diode was produced.

This Schottky barrier diode had a withstand voltage of 600 V, a current density of 500 A / cm ² , a current of 0.15 A, an on-resistance of 3.3 mΩsq, and a forward voltage of 1.5 V.
(Comparative Example 3)

An experiment was conducted in the same manner as in Example 4 except that a GaN substrate obtained by dividing the GaN wafer of Comparative Example 1 into four parts was used instead of the GaN substrate obtained by dividing the GaN wafer of Example 1 into four parts. Went. That is, a Schottky barrier diode was manufactured using a GaN substrate obtained by performing hydrogen ion implantation without forming an SiO ₂ film.

The on-resistance of the Schottky barrier diode obtained in Comparative Example 3 was much lower than the on-resistance of the Schottky barrier diode obtained in Example 4, and good device characteristics could not be obtained. Accordingly, it was shown that it is preferable to form a SiO ₂ film and perform hydrogen ion implantation.
(Example 5)

The surface of the polycrystalline Al ₂ O ₃ film of the GaN substrate obtained by dividing the GaN wafer of Example 2 into two was polished with colloidal silica. Thereby, the surface roughness Ra of the polycrystalline Al ₂ O ₃ film was set to 0.8 nm.

Subsequently, the GaN substrate and the Si substrate were joined. Specifically, first, a thermal oxide film having a thickness of 100 nm was formed on a Si substrate, and the surface of the thermal oxide film was exposed to plasma generated by discharge in Ar gas to obtain a support substrate. . On the other hand, the surface of the polycrystalline Al ₂ O ₃ film on the GaN substrate was exposed to plasma generated by discharge in Ar gas in a dry etching apparatus. Then, the thermal oxide film of the support substrate and the polycrystalline Al ₂ O ₃ film of the GaN substrate were bonded together in the atmosphere. Note that the RF power for generating plasma was 100 W, the Ar gas flow rate was 50 sccm, and the pressure in the chamber was 6.7 Pa.

  Subsequently, in order to increase the bonding strength between the support substrate and the GaN substrate and to exfoliate a part of the GaN substrate with a weak region formed inside the GaN substrate by ion implantation as a boundary, at 300 ° C. in nitrogen for 2 hours. Heating was performed. Thus, a bonded substrate having a GaN layer formed on the support substrate was obtained.

  When the interface between the support substrate and the GaN substrate was observed, the bonding strength between the support substrate and the GaN substrate obtained in Example 5 was higher than the bonding strength between the support substrate and the GaN substrate obtained in Example 2. It turned out to be expensive.

  2 ... Group III nitride semiconductor substrate, 2a ... Main surface of group III nitride semiconductor substrate, 2c ... Part of group III nitride semiconductor substrate, 4 ... Protective film, 4a ... Surface of protective film, 6 ... Support substrate, 10, 10a: Bonded substrate, f: Fragile region.

Claims (4)

Forming a protective film on the main surface of the group III nitride semiconductor substrate;
Forming a fragile region in the group III nitride semiconductor substrate by ion-implanting into the main surface of the group III nitride semiconductor substrate through the protective film;
Bonding the main surface of the group III nitride semiconductor substrate to a support substrate;
Peeling a part of the group III nitride semiconductor substrate from the support substrate with the fragile region as a boundary;
A method for manufacturing a bonded substrate board, comprising:   The method for manufacturing a bonded substrate according to claim 1, wherein the protective film includes at least one of an oxide film, a nitride film, and a metal film. A step of planarizing the surface of the protective film between the step of forming the fragile region and the step of bonding the main surface of the group III nitride semiconductor substrate to the support substrate;
3. The method for manufacturing a bonded substrate according to claim 1, wherein a main surface of the group III nitride semiconductor substrate is bonded to the support substrate via the protective film.   The method according to claim 1, further comprising a step of removing the protective film between the step of forming the fragile region and the step of bonding the main surface of the group III nitride semiconductor substrate to the support substrate. Manufacturing method of bonded substrate.