JP4768759B2 - Group III nitride semiconductor substrate - Google Patents

Description

The present invention relates to a self-supporting board of the group III nitride semiconductor.

  GaN-based compound semiconductors such as gallium nitride (GaN), indium gallium nitride (InGaN), and gallium aluminum nitride (AlGaN) are in the limelight as materials for blue light-emitting diodes (LEDs) and laser diodes (LDs). . Furthermore, GaN-based compound semiconductors have begun to be applied to electronic device elements, taking advantage of their good heat resistance and environmental resistance.

  Since GaN-based compound semiconductors are difficult to grow bulk crystals, it is difficult to obtain a GaN substrate that can withstand practical use. A substrate for GaN growth that is currently in wide use is a sapphire substrate, and a method of epitaxially growing GaN on a single crystal sapphire substrate by metal organic vapor phase epitaxy (MOVPE method) is generally used.

However, since the sapphire substrate has a lattice constant different from that of GaN, a single crystal film cannot be grown by directly growing GaN on the sapphire substrate. For this reason, a method has been devised in which a buffer layer of AlN or GaN is once grown on a sapphire substrate at a low temperature, and lattice distortion is relaxed by this low-temperature growth buffer layer, and then GaN is grown thereon (Patent Document). 1). Using this low-temperature grown nitride layer as a buffer layer, GaN single crystal epitaxial growth has become possible. However, even with this method, the difference between the lattice of the substrate and the crystal is still difficult, and GaN has innumerable defects. This defect is expected to be an obstacle to manufacturing a GaN-based LD. In recent years, ELO (Non-Patent Document 1), FIELO (Non-Patent Document 2), and pendeo epitaxy (Non-patent Document) are methods for reducing the density of defects generated due to the difference in lattice constant between sapphire and GaN. A growth technique such as literature 3) has also been reported, and a GaN epitaxial wafer with dramatically improved crystallinity has been obtained.
Japanese Unexamined Patent Publication No. 63-188983 Appl.Phys.Lett.71 (18) 2638 (1997) Jpn.J.Appl.Phys.38, L184 (1999) MRS Internet J. Nitride Semicond. Res. 4S1, G3.38 (1999)

  However, although single crystal GaN layers with low defect density can be grown by methods such as ELO and FIELO, the above-mentioned epitaxial wafer is caused by the difference in lattice constant and thermal expansion coefficient between sapphire and GaN. Thus, there is a problem that the substrate is warped. When the substrate is warped, it is not only easy to break the substrate during handling, but also when it is difficult to focus uniformly on the substrate surface when baking the mask pattern on the substrate in the photolithography process of the device process, etc. Yield decreases. For these reasons, it is highly desirable to develop a GaN epi substrate having a low defect density and no warpage. Furthermore, although it is desirable to obtain a GaN bulk substrate having a low defect density and no warpage, it is very difficult to produce a large bulk GaN crystal, and a practical one has not yet been obtained.

  Recently, a method has been proposed in which a GaN thick film is heteroepitaxially grown on a substrate by a method such as HVPE (hydride vapor phase epitaxy), and then the substrate is removed to obtain a GaN free-standing substrate. However, in this method, a technique for separating GaN grown on the sapphire substrate by etching from the sapphire substrate has not been developed so far. Attempts have also been made to mechanically remove the sapphire substrate by polishing, but the warpage of the substrate increases during the polishing process, and the substrate may be cracked. In Jpn.J.Appl.Phys.Vol.38 (1999) Pt.2, No.3A, GaN is grown thickly on the sapphire substrate by HVPE method, and then laser pulse is irradiated to peel off only the GaN layer. The method to make it reported. However, even with this method, there is a problem that the substrate is easily cracked. As a method of using a substrate that can be easily removed, Japanese Patent Application Laid-Open No. 2000-12900 discloses a method of growing GaN thickly on a GaAs substrate by HVPE and then removing the GaAs substrate by etching. If this method is used, a large GaN substrate can be obtained with a relatively high yield. However, the GaAs substrate is decomposed during GaN crystal growth, and As is mixed into the GaN as an impurity. is there. For reducing the defect density of epitaxially grown GaN, selective growth using a patterned mask, such as the above-described FIELO, is effective, and a technique such as JP-A-10-312971 has been disclosed. Since there was no technique for peeling, it has not been applied to the production of a GaN free-standing substrate.

  In view of the above circumstances, an object of the present invention is to provide a group III nitride semiconductor substrate having a low defect density and little warpage.

According to the invention, the step of forming a metal element-containing film on the base substrate, the step of growing the first group III nitride semiconductor layer in contact with the metal element-containing film, and the first Heat treating the metal element-containing film and the first group III nitride semiconductor layer at a temperature higher than the growth temperature of the group III nitride semiconductor layer, and forming a void in the first group III nitride semiconductor layer. A step of forming, a step of forming a second group III nitride semiconductor layer on the first group III nitride semiconductor layer, and a step of peeling off and removing the base substrate using the gap as a peeling portion. A group III nitride semiconductor substrate obtained by a manufacturing method including :

Further, according to the present invention, a step of forming a metal element-containing film having at least a surface made of metal nitride on the base substrate, and a V / III ratio of the source gas in contact with the metal element-containing film is 10 or less. conditions by growing a group III nitride semiconductor in the production comprising the steps of forming a group III nitride semiconductor layer, and removing by peeling the base substrate the gap portion as a release position, the including a void portion A group III nitride semiconductor substrate obtained by the method is provided.

  In the present invention, a group III nitride semiconductor layer having a void portion is formed on a substrate via a metal element-containing film, and the underlying substrate is peeled and removed by using the void portion as a peeling portion. The metal element-containing film has a role of forming a group III nitride semiconductor layer of good quality on the film and forming a void in the group III nitride semiconductor layer. The void functions as a strain relaxation region, improves the crystal quality of the group III nitride semiconductor layer formed thereon, and facilitates peeling and removal of the base substrate.

  The form of the voids in the group III nitride semiconductor is not particularly limited, but is preferably formed in layers on the metal element-containing film. By doing so, the group III nitride semiconductor layer including the porous layer is stably formed, and the residual strain in the group III nitride semiconductor layer can be effectively reduced. In addition, it becomes easier to remove and remove the base substrate, and natural peeling can be performed in the temperature lowering process after the growth of the group III nitride semiconductor layer without going through a special process for peeling.

  Various methods can be employed for forming the voids in the present invention. A metal element-containing film may be formed using a metal having a decomposition action on a group III nitride semiconductor, and voids may be formed by such a decomposition action. By forming the group III nitride semiconductor layer, a group III nitride semiconductor layer having a void near the interface with the metal element-containing film can be formed.

  Even in the conventional process, there has been an example in which voids are introduced into the group III nitride semiconductor layer formed on the substrate. For example, in the ELO process described in the section of the prior art, when a mask is grown using a silicon mask, the mask may not be completely filled with GaN and a void may remain. In the mask growth using a tungsten mask, GaN and tungsten may react with each other on the mask to generate voids. However, these are examples where undesired voids are introduced unintentionally on the mask, and the underlying substrate is not peeled off with the voids being peeled off. In addition, the gap does not play a role of relaxing the strain or assisting the peeling of the base substrate as in the present invention. On the other hand, since the present invention has voids formed by a chemical action or a physical action of the metal element-containing film, the following effects can be obtained.

  First, a group III nitride semiconductor substrate having a low defect density and good crystal quality can be obtained. This is because a region having voids functions as a strain relaxation region, and alleviates strain caused by a difference in lattice constant and a difference in thermal expansion coefficient between the base substrate and the group III nitride semiconductor layer.

  Secondly, the warp of the obtained semiconductor substrate can be significantly reduced, and the yield in the photolithography process of the device process can be improved. This is because the layer having voids functions as a strain relaxation region, and alleviates strain caused by a difference in lattice constant and a difference in thermal expansion coefficient between the base substrate and the group III nitride semiconductor layer.

  Third, since the substrate can be easily removed, a self-standing GaN single crystal substrate having a large diameter and free from cracks and scratches can be easily obtained. This is because a layer having a gap is interposed between the base substrate and the group III nitride semiconductor layer, so that the base substrate can be easily removed by natural peeling, chemical solution, mechanical impact, or the like.

  According to the present invention, a group is introduced into the group III nitride semiconductor layer, and a structure in which the base substrate is peeled off from the gap is adopted, so that the group III nitride semiconductor has low defect density and low warpage. A substrate can be obtained. This is because the layer having voids functions as a strain relaxation region and the base substrate can be easily peeled and removed from the voids.

  The present invention includes a step of forming a metal element-containing film on a base substrate, a step of forming a group III nitride semiconductor layer including a void in contact with the metal element-containing film, and peeling the void And removing the base substrate as a location. Hereinafter, a method for stably forming a void having a structure in which distortion can be sufficiently relaxed and the substrate can be easily peeled will be described by classifying into types I to IV.

Type I
The type I manufacturing method includes a step of forming a metal element-containing film on a base substrate, a step of growing a first group III nitride semiconductor layer in contact with the metal element-containing film, and the first Heat treating the metal element-containing film and the first group III nitride semiconductor layer at a temperature higher than the growth temperature of the group III nitride semiconductor layer, and forming a void in the first group III nitride semiconductor layer. Forming a second group III nitride semiconductor layer on the first group III nitride semiconductor layer. In this manufacturing method, the metal element-containing film may be a metal oxide film or a metal nitride film, but is preferably a metal film made of a single metal. This is because the decomposition action on the group III nitride semiconductor tends to be remarkable.

  According to this manufacturing method, the growth of the group III nitride semiconductor layer on the metal element-containing film is performed by a low-temperature process, so that the layer growth can be performed in a state in which the metal element-containing film surface maintains high catalytic activity. . For example, when a group III nitride semiconductor layer is formed on a film made of a simple metal, the growth of the layer is usually difficult, but a relatively high quality crystal quality layer is obtained by employing a low temperature process. be able to. That is, according to the present manufacturing method, it is possible to grow a group III nitride semiconductor layer having a good film quality while maintaining high catalytic activity of the metal element-containing film, and to obtain a group III nitride semiconductor substrate having an excellent quality. be able to.

  The growth temperature of the first group III nitride semiconductor layer is preferably 400 ° C. or higher and 800 ° C. or lower. By doing so, the group III nitride semiconductor layer can be preferably grown on the metal element-containing film. As described above, when a metal film made of a single metal is used as a metal element-containing film, it is usually difficult to grow a group III nitride semiconductor layer on the metal element-containing film. , Stable layer growth.

  The heat treatment for forming the void is preferably performed at a temperature of 900 ° C. or higher and 1400 ° C. or lower. By doing so, it is possible to stably form a void having a structure in which distortion can be sufficiently relaxed and the substrate can be easily peeled off with good controllability. This heat treatment can be performed, for example, in an atmosphere of nitrogen gas, oxygen gas, hydrogen gas, or a mixed gas thereof, but it is preferable to use a gas containing nitrogen element such as nitrogen gas or ammonia gas. By carrying out like this, a space | gap part can be formed suitably. Even if this heat treatment is not provided as a separate step, the voids may be formed by heat treatment when growing the second group III nitride semiconductor layer. For example, in the epitaxial growth of GaN-based semiconductors, growth is usually performed at a temperature of 1000 ° C. or higher. By growing a GaN layer at such a temperature using a metal element-containing film as an underlayer, the vicinity of the interface with the metal element-containing film is obtained. A GaN layer provided with voids can be obtained stably.

  The thickness of the first group III nitride semiconductor layer is preferably 20 nm or more, more preferably 50 nm or more, preferably 2000 nm or less, more preferably 1000 nm or less. By doing so, it is possible to stably form voids in the layer with good controllability while maintaining good crystal quality of the group III nitride semiconductor layer.

Type II
A type II manufacturing method includes forming a metal element-containing film having a microporous structure on a base substrate, and forming a group III nitride semiconductor layer including a void portion in contact with the metal element-containing film. And a process. It is preferable that at least the surface of the metal element-containing film having a microporous structure is made of a metal nitride. In this way, a good quality group III nitride semiconductor layer can be epitaxially grown on the metal element-containing film.

  The metal element-containing film having a microporous structure is the surface of the base substrate (if the metal element-containing film is directly formed on a different substrate, the surface of the different substrate, and the III-nitride semiconductor film is formed on the different substrate. It is possible to obtain a metal material that does not lattice match with the group nitride semiconductor film) by using a film formation method and film formation conditions that can obtain relatively high crystallinity. It is considered that since the crystal structure is different from that of the base substrate and the lattice constant is also different, a large residual strain is generated in the film, resulting in a microporous structure. When a group III nitride semiconductor layer is grown thereon, epitaxial information is passed from the base substrate to the group III nitride semiconductor layer through the fine holes, and a large number of fine voids are generated in this layer.

  Note that the structure having the micropores can be created by adjusting the film formation conditions, but can also be created by appropriately performing a heat treatment after forming the metal film or the metal nitride film. The heat treatment for forming the void is appropriately selected depending on the material of the metal element-containing film. For example, when a titanium film is formed, the heat treatment temperature is preferably 700 ° C. or higher, more preferably 800 ° C. or higher. If the temperature is too low, the void formation efficiency may be reduced. The upper limit is appropriately set depending on the film forming material or the like, but in the case of a GaN-based material, it is preferably 1400 ° C. or lower.

Type III
A type III manufacturing method includes a step of forming a metal element-containing film having at least a surface made of a metal nitride on a base substrate, a step of desorbing nitrogen contained in the metal nitride, and the metal element. Forming a group III nitride semiconductor layer including a void in contact with the containing film. According to this manufacturing method, the catalytic activity on the surface of the metal element-containing film is improved, and voids can be formed more stably in the group III nitride semiconductor layer.

  The metal element-containing film in this manufacturing method can be formed by forming a metal film on a base substrate and then nitriding the metal film or by forming a metal nitride film on the base substrate. The nitrogen desorption treatment may be a treatment such as bringing the metal element-containing film into contact with a reducing atmosphere. The reducing atmosphere refers to an atmosphere containing hydrogen, ammonia, or the like.

Type IV
In the type IV manufacturing method, a step of forming a metal element-containing film having at least a surface made of metal nitride on a base substrate, and a V / III ratio of a source gas in contact with the metal element-containing film is 10 or less. And a step of growing a group III nitride semiconductor under the conditions and forming a group III nitride semiconductor layer including a void. By so doing, the lateral growth of the group III nitride semiconductor layer on the metal element-containing film can be promoted, and the voids can be suitably formed.

  Various configurations can be adopted for each process and materials used in the present invention. Hereinafter, such a configuration will be described.

  In the present invention, the metal element-containing film can be formed on the entire surface of the base substrate. By doing so, voids can be formed over the entire surface of the substrate, distortion can be more effectively mitigated, and the substrate can be more easily separated.

In the present invention, the metal element-containing film may contain a metal element having a catalytic action that promotes decomposition of the group III nitride semiconductor. Examples of such metal elements include transition elements, particularly d-block transition elements. Of these, scandium, yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, tungsten, chromium, molybdenum, Les chloride, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, manganese, copper, platinum And one or more elements selected from the group consisting of gold and gold. By using such a material, it is possible to form a void having a suitable shape in the group III nitride semiconductor layer.

  Among the above, titanium, zirconium, hafnium, tantalum, tungsten, platinum, cobalt, and nickel are particularly preferable because they easily form voids in the group III nitride semiconductor layer. Furthermore, titanium, zirconium, hafnium, tantalum and tungsten are relatively stable at the growth temperature of the group III nitride semiconductor layer and can be preferably used in the present invention. However, when tungsten is selected, since decomposition of GaN occurs even at a low temperature of about 600 ° C., voids may suddenly occur, and handling may be required.

  The reason why the metal forms voids in the group III nitride semiconductor layer is not always clear, but it is presumed that the metal acts as a catalyst on the group III nitride semiconductor and promotes decomposition.

The metal element-containing film in the present invention preferably further satisfies the following conditions.
(i) The orientation of the base substrate is transmitted, and the group III nitride semiconductor layer can be suitably single-crystal epitaxially grown on the metal element-containing film. The metal element-containing film has a hexagonal or cubic crystal system. If the metal element-containing film is a hexagonal crystal system on the base substrate, the [0001] axial direction, and if the metal element-containing film is a cubic crystal system, [111] It is desirable that it can be oriented in the axial direction.
(ii) The melting point or decomposition start temperature of the metal element-containing film is higher than the growth temperature of the group III nitride semiconductor layer formed thereon, and the film form can be maintained at the growth temperature.
(iii) The vapor pressure at the growth temperature of the group III nitride semiconductor layer grown on the metal element-containing film is sufficiently low, and no sublimation occurs at the growth temperature.
(iv) At the growth temperature of the group III nitride semiconductor layer grown on the metal element-containing film, it does not react with the nitride semiconductor, its source gas, or growth atmosphere gas (ammonia gas, hydrogen gas, etc.), and the crystal orientation is Do not disturb.
By using a metal element-containing film that satisfies these conditions, a group III nitride semiconductor substrate with even better crystal quality can be obtained.

  The metal element-containing film in the present invention may be a single metal or a metal compound, and may be a single layer film or a composite film in which two or more kinds of films are laminated. Preferably, a metal film, a metal nitride film, or a laminate thereof is used.

  The metal element-containing film in the present invention serves as an underlayer for growing a high-quality crystal-quality group III nitride semiconductor layer thereon, so that at least a part of the surface thereof becomes a metal nitride. It is preferable. By doing so, the group III nitride semiconductor can be suitably grown at a normal film forming temperature. For these reasons, it is preferable to select a metal element that is easily nitrided as a material constituting the metal element-containing film. From such a viewpoint, titanium, tantalum, tungsten, or the like is preferable as the metal element constituting the metal element-containing film. In addition, since the surface of the metal film such as titanium is nitrided by being exposed to the growth atmosphere of the group III nitride semiconductor, a step for nitriding is not particularly required. You may provide the process for controlling independently. Further, by introducing nitrogen gas or a compound gas containing nitrogen atoms simultaneously with hydrogen into the heat treatment atmosphere in the step of forming voids, it is possible to nitride titanium simultaneously with the formation of voids. In the type I process described above, the group III nitride semiconductor on the metal element-containing film is grown at a low temperature. In this case, the metal element-containing film can be formed of a single metal.

  In addition, since the metal element-containing film in the present invention has a role of acting on the group III nitride semiconductor layer formed thereon to generate voids, the metal element-containing film is formed on at least a part of the surface of the metal element-containing film. It is preferable that a surface having high catalytic activity such as a simple metal is exposed. Here, the surface of the metal element-containing film refers to the upper surface of a flat film, and refers to both the inner wall of the hole and the upper surface of the film in a film having fine holes. If a surface having high catalytic activity such as a simple metal is exposed at these locations, a group III nitride semiconductor layer having voids is suitably formed.

  The thickness of the metal element-containing film in the present invention is appropriately set according to the material and the like, and is, for example, 3 nm or more, more preferably 5 nm or more. The upper limit is 500 nm or less, more preferably 50 nm or less. By doing so, it is possible to suitably form voids on the metal element-containing film while maintaining good crystal quality of the group III nitride semiconductor layer formed on the metal element-containing film.

  As a method for depositing the metal element-containing film, an evaporation method, a sputtering method, various CVD methods, or the like can be used. The metal element-containing film desirably has a flat surface and covers the entire surface of the substrate, and may have a structure having fine holes in the film. With such a structure having fine holes, the defect density in the group III nitride semiconductor layer formed on the metal element-containing film can be effectively reduced. The group III nitride semiconductor layer can be grown over the hole.

  For example, when titanium is selected as the material for the metal element-containing film, the heat treatment for nitriding the metal film and generating substantially uniform holes is desirably performed at a temperature of 700 ° C. or higher and 1400 ° C. or lower. This is because if the temperature is lower than 700 ° C., the nitriding reaction does not proceed sufficiently and substantially uniform holes cannot be formed. When a nitride semiconductor substrate or a nitride semiconductor epitaxial wafer is used as the base substrate, if the temperature exceeds 1400 ° C., the thermal decomposition of the single crystal gallium nitride layer may proceed excessively and the metal nitride film may be peeled off. The heat treatment for nitriding the metal film and generating substantially uniform holes is preferably performed in an atmosphere containing nitrogen gas or nitrogen-containing compound gas. By doing so, it is possible to form a film having micropores capable of generating a void having a suitable form in the group III nitride semiconductor layer.

In the present invention, the formation conditions of the metal element-containing film may be appropriately adjusted, and after the metal element-containing film is formed, the surface treatment of the metal element-containing film is performed before the group III nitride semiconductor layer is formed thereon. May be performed. By doing this,
(I) Group III nitride semiconductor decomposition action (catalytic action) of the metal element-containing film is sufficiently exerted, or
(Ii) A lateral structure is promoted to form a bridge-like structure on the metal element-containing film,
A void portion having a high stress relaxation effect and a high substrate peeling effect can be formed more stably. Hereinafter, an example of such a surface treatment method will be described.

Method 1
The formation rate of the metal element-containing film is 1 nm / sec or less. By doing so, the orientation of the metal element-containing film can be maintained moderately, and a void portion having a high stress relaxation effect and a high substrate peeling effect can be suitably formed. For example, in the case of Ti, if the deposition rate is 1 nm / sec or less, the (0001) orientation of Ti is maintained well, and good crystallinity is obtained even when nitriding. As a result, it is possible to suppress the precipitation of island crystals having different crystal orientations on the surface of the nitride film, and the voids intended by the present invention can be suitably formed.

Method 2
The thickness of the metal element-containing film is adjusted. For example, the thickness of the metal element-containing film is set to 5 nm to 50 nm. By doing so, it is possible to suitably form voids on the metal element-containing film while maintaining good crystal quality of the group III nitride semiconductor layer formed on the metal element-containing film. When Ti is employed as the metal element-containing film material, the thickness of Ti is desirably 5 nm to 50 nm. If Ti is too thin, the network after nitriding will be too large, the area of TiN will be reduced, void formation will be insufficient, and peeling will not be possible. On the other hand, if the thickness is more than 50 nm, the crystallinity of the nitride film deteriorates, and island-like crystals with different crystal orientations are likely to precipitate on the nitride film surface, which hinders lateral growth and leads to void formation. This is because it becomes insufficient.

Method 3
Before the group III nitride semiconductor layer is grown on the metal element-containing film, the surface of the metal element-containing film is wet-treated. In this way, the natural oxide film on the metal element-containing film is removed, and the catalytic action for forming voids is sufficiently exhibited. For the wet treatment, for example, a method of immersing in HF for 30 minutes and washing with water can be used.

Method 4
The carrier gas composition during growth of the group III nitride semiconductor layer on the metal element-containing film is adjusted. By so doing, the lateral growth of the group III nitride semiconductor layer on the metal element-containing film can be promoted, and the voids can be suitably formed. For example, the group III nitride semiconductor layer is formed by HVPE, and the carrier gas at the time of growth has a composition containing 70% or more of an inert gas (N ₂ or the like).

Method 5
The reaction gas composition during the growth of the group III nitride semiconductor layer on the metal element-containing film is adjusted. Specifically, the V / III ratio is adjusted. Specifically, the V / III ratio is 10 or less. By so doing, the lateral growth of the group III nitride semiconductor layer on the metal element-containing film can be promoted, and the voids can be suitably formed.

Method 6
The doping profile during the growth of the group III nitride semiconductor layer on the metal element-containing film is adjusted. For example, when Si is introduced as an impurity to form an n-type group III nitride semiconductor substrate,
The Si atom concentration is set to 5 × 10 ¹⁷ cm ⁻³ or less until the thickness reaches 5 μm after the start of growth. This is because lateral growth is hindered if too much Si is added.

  In the above method, the growth temperature during growth of the group III nitride semiconductor layer on the metal element-containing film is preferably 800 ° C. or higher. This is because the catalytic action of the metal constituting the metal element-containing film is exhibited at or above that temperature.

  The growth method of the group III nitride semiconductor layer in the present invention includes various methods such as the MOCVD method (metal organic vapor phase growth method), the MBE method (molecular beam epitaxy method), the HVPE method (hydride vapor phase growth method). It is possible to use the method. It is desirable to use the HVPE method for the growth of a thick film group III nitride semiconductor to obtain a group III nitride semiconductor free-standing substrate. This is because the crystal growth rate is fast and it is easy to obtain a thick film, but also by another method such as MOCVD method, a group III nitride semiconductor is grown partway by MOCVD method, and then A plurality of growth methods may be used in combination, such as a thick growth of a group III nitride semiconductor by the HVPE method.

In the group III nitride semiconductor layer in the present invention, an inert gas or a mixed gas of hydrogen and the like can be used as a carrier gas. The inert gas can include at least one of N ₂ , He, Ne, Ar, Kr, and Xe. When forming a group III nitride layer, an inert gas such as nitrogen can be used as a carrier gas at the initial stage of growth, and then the carrier gas can be switched to hydrogen to grow a layer having excellent crystallinity.

  In the present invention, the base substrate is not particularly limited, and various substrates can be used. Examples include substrates made of different materials such as sapphire, silicon, SiC, langasite, Al, and GaAs, and substrates made of group III nitride semiconductors such as GaN, AlN, and AlGaN. For example, when using sapphire, the C-plane, A-plane, R-plane, etc. can be used. The base substrate may have an off angle, but it is preferable to set the off angle within 1 °. By making it within 1 °, the orientation of the metal film can be kept good and the group III nitride semiconductor layer can be grown well on the film.

  The base substrate in the present invention may be made of a substrate made of the above-mentioned material, or may have a structure in which a group III nitride semiconductor is appropriately formed thereon via a GaN low-temperature growth buffer layer.

  In the present invention, the group III nitride semiconductor layer can be various semiconductor layers, such as GaN, AlGaN, InGaN, or InAlGaN. Of these, the vicinity of the metal element-containing film, for example, the region extending over 100 nm on the metal element-containing film is preferably composed of GaN or AlGaN having an aluminum composition of 0.1 or less. By doing so, voids suitable for stress relaxation and substrate peeling can be formed near the metal element-containing film with good controllability.

  The thickness of the group III nitride semiconductor layer is desirably 1 μm or more. There may be a minute hole on the surface of the metal nitride film, and the hole is inherited on the surface of the group III nitride semiconductor layer at the initial stage of growth. Although the holes are gradually filled and eventually disappeared, the thickness of the group III nitride semiconductor layer is preferably 1 μm or more in order to fill the holes and make the surface completely flat.

  The porosity of the group III nitride semiconductor layer is preferably 20% or more, more preferably 30% or more, and preferably 90% or less, more preferably 80% or less. If the porosity is too small, the effect of strain relaxation is small, and the effect of reducing the warpage of the substrate and the defect density may not be obtained. If the porosity is too large, the metal film may partially peel during growth of the group III nitride semiconductor layer on the metal element-containing film, and crystal growth may be inhibited.

  In the present invention, the step of forming the group III nitride semiconductor layer on the metal film includes the step of forming a mask having an opening directly or via another layer on the metal film, and then forming the opening in a growth region. As a process, a group III nitride semiconductor layer can be epitaxially grown on the opening and the mask. In this case, the group III nitride semiconductor is epitaxially grown on the entire surface of the substrate so as to cover the opening and then the mask, starting from the mask opening. As such a growth method, a method called ELO for performing selective lateral growth or a method called FIELO for growing a selective mask while forming a facet structure can be employed.

  In the present invention, the base substrate is peeled off after the step of forming the group III nitride semiconductor layer. As a method for removing the base substrate, after the growth of the group III nitride semiconductor layer, a method of naturally peeling the base substrate by lowering the ambient temperature, mechanically applying stress to the group III nitride semiconductor layer having voids For example, a method for peeling the base substrate, a method for removing the base substrate by etching away a region provided with a void in the metal element-containing film or the group III nitride semiconductor layer, or the like can be used.

  Next, an example using a Ti-containing film as the metal element-containing film of the present invention will be described.

The present inventors have found that when a heat treatment is performed on a group III nitride semiconductor layer laminated on a specific metal film such as Ti or Ni, voids are formed in the group III nitride semiconductor layer. .
(I) The catalytic action of Ti / TiN should be significantly reduced at low temperatures below 800 ° C.
(Ii) It is possible to grow a GaN crystal on Ti at about 500 to 800 ° C.
Based on the above two findings, it was found that a void portion can be generated by the following method using a substrate that is not decomposed by the action of Ti / TiN, such as a sapphire substrate.

(Example 1)
This example belongs to type I described above. First, Ti is vapor-deposited on a sapphire substrate. Next, GaN is deposited at a low temperature. Thereafter, the temperature is raised to generate voids in the low-temperature GaN. Subsequently, a thick GaN film is grown at a high temperature, and then the sapphire substrate is removed by natural peeling or etching to obtain a self-supporting substrate.

(Example 2)
This example belongs to the above-mentioned type II. In this example, a void is formed above the metal element-containing film without nitriding. The inventors of the present invention have found that the surface of the base substrate (if the metal element-containing film is formed directly on the heterogeneous substrate, the heterogeneous substrate surface, and if the group III nitride semiconductor film is formed on the heterogeneous substrate, the group III nitride semiconductor film It has been found that a thin film having a fine pore structure can be formed by forming a metal nitride or metal thin film that does not lattice match with (1). At this time, after forming a thin film of metal or metal nitride, it is not necessary to perform nitriding or heat treatment on the thin film. A thin film of metal or a metal nitride thereof has a crystal structure and a lattice constant different from those of the base substrate, so that a large strain is applied to the thin film. As a result, it is considered that pores are generated at crystal grain boundaries and a fine pore structure is generated. When the group III nitride semiconductor layer is crystallized thereon, the epitaxial information is inherited from the underlying substrate to the group III nitride semiconductor layer through the fine holes. Crystals appearing on the thin film are combined with each other by lateral growth to form a continuous nitride film, but many fine voids are generated at the interface between the thin film and the group III nitride semiconductor layer.

  The structure having the fine holes can be created by adjusting the deposition conditions of the metal film or metal nitride film, but can also be created by appropriately performing a heat treatment after forming the metal film or metal nitride film. be able to. The heat treatment for forming the void is appropriately selected depending on the material of the metal element-containing film. For example, when a titanium film is formed, the heat treatment temperature is preferably 700 ° C. or higher, more preferably 800 ° C. or higher. If the temperature is too low, the void formation efficiency may be reduced. The upper limit is appropriately set depending on the film forming material or the like, but in the case of a GaN-based material, it is preferably 1400 ° C. or lower.

(Example 3)
This example belongs to the aforementioned type III. The temperature rise before growing the nitride layer may be performed only in an H ₂ atmosphere. By doing so, the TiN surface can be exposed to an H ₂ atmosphere before embedding to promote N desorption, and a part of Ti can be exposed. As a result, the decomposition effect on the group III nitride semiconductor of Ti becomes remarkable, and the void portion is suitably formed.

  In this example, when the nitride semiconductor layer is grown on the metal element-containing film, the V / III ratio is <10 at least in the initial growth stage. By performing the growth under Ga-rich conditions, Ti having high catalytic activity can be exposed on the surface by promoting N desorption of TiN in the initial growth stage.

(Reference example)
A metal Ti film having a thickness of 30 nm was deposited on the C-plane of a single crystal sapphire substrate having a diameter of 2 inches. This substrate was placed in an electric furnace and subjected to a heat treatment at 1050 ° C. for 30 minutes in an N ₂ stream mixed with 20% NH ₃ to nitride the Ti film surface. Thereafter, the temperature was raised to 1040 ° C. under a _{N 2} atmosphere, deposited GaN of about 500nm thick was formed HVPE-GaN layer. N ₂ was used as the carrier gas. When the cross section of the obtained substrate was observed with a scanning electron microscope (SEM), it was confirmed that a large number of voids were generated above the Ti film and a porous layer was formed.

  Further, when a similar experiment was performed by replacing the metal Ti film with a cobalt film, it was confirmed that a large number of voids were generated above the cobalt film and a porous layer was formed. Furthermore, when a similar experiment was conducted with respect to a nickel film and a platinum film, it was confirmed that a large number of voids were generated above these films and a porous layer was formed.

Based on the results of these experiments, the present inventors conducted further detailed experiments using a Ti film and proceeded with studies. Hereinafter, the present invention will be described in more detail based on examples. Details of the process conditions and evaluation results in each example are summarized in Table 1. In the examples, in the growth of the GaN layer immediately above Ti, TiN, etc., silicon was doped at 5 × 10 ¹⁷ cm ⁻² except that Example 2 was used as an impurity.

Example 1
Each step of this embodiment will be described with reference to FIG. First, a 30 nm-thick metal Ti film 12 was deposited at a deposition rate of 0.8 nm / sec on the C-plane of a single crystal sapphire substrate 11 (FIG. 1A) having a diameter of 2 inches (FIG. 1B )). This substrate was put into an HVPE furnace, and 1 μm of the first GaN layer 13 was grown at 750 ° C. using GaCl and NH ₃ as raw materials (FIG. 1C). Next, the temperature of the substrate is raised to 1050 ° C. in the furnace, and heat treatment is performed for 30 minutes in an NH ₃ gas stream, whereby the metal Ti film 12 is changed to the TiN film 15 and voids are formed in the first GaN layer. 14 is formed (FIG. 1D).

Subsequently, in the same furnace, a Si-doped second GaN layer 16 was grown by 250 μm on the first GaN layer 13 using GaCl and NH ₃ as raw materials and SiH ₂ Cl ₂ as a dopant at 1050 ° C. (FIG. 1). (E)). These growths were performed at normal pressure, and a mixed gas in which 10% H ₂ and 90% N ₂ (volume basis) were mixed was used as a carrier gas. The growth gas V / III ratio was 10.

  After the growth of the second GaN layer 16 was completed, the stacked body of the first GaN layer 13 and the second GaN layer 16 naturally separated from the sapphire substrate 11 during the temperature lowering process, and a GaN free-standing substrate was obtained. At the interface of the peeled GaN layer, voids 14 are exposed on the surface, so that fine irregularities were observed on the entire surface. The surface having the irregularities was finished flat by polishing with diamond abrasive grains. As a result, a single-crystal GaN free-standing substrate 17 was obtained (FIG. 1 (f)).

When the warpage of the obtained GaN free-standing substrate 17 was measured, the curvature radius of the warpage of the substrate was about 10 m, and it was confirmed that a very flat substrate was obtained. Further, when the surface of the obtained GaN free-standing substrate 17 (surface opposite to the side from which the base substrate was peeled off) was observed with an atomic force microscope and the density of pits on the surface was measured, 2 × 10 ⁶ cm ⁻² Therefore, it was confirmed that the substrate had high crystallinity.

  In the same manner as described above, the process up to the middle of FIG. 1E is performed, and after the second GaN layer 16 is grown to a thickness of several μm, the substrate is divided, and the cross section is SEM (scanned). 2), as shown in FIG. 2, the sapphire substrate has a GaN layer having a gap through a Ti nitride film layer, and a flat GaN layer is deposited thereon. It was confirmed that The porosity of the first GaN layer 13 estimated from the cross-sectional SEM photograph was about 50%. The reason why the crystallinity and flatness of the crystal grown by this method is high is considered to be borne by the first GaN layer 13 having this void.

(Example 2)
Each process of a present Example is demonstrated using FIG. On the C-plane of a single crystal sapphire substrate 31 (FIG. 3A) having a diameter of 2 inches, an undoped GaN layer 32 was grown by 1 μm by MOVPE using TMG and NH ₃ as raw materials (FIG. 3B). On the GaN epitaxial substrate thus obtained, TiN 4 was deposited to a thickness of 20 nm at 800 ° C. by CVD using TiCl ₄ and NH ₃ as raw materials to provide a TiN film 34 (FIG. 3C). The deposition rate was about 1 nm / sec. When X-ray diffraction measurement was performed on this sample, a TiN diffraction peak was observed as shown in FIG. 4, and it was confirmed that the TiN film 34 was a film oriented in the [111] direction.

  Further, when the surface and cross section of the sample at the stage of FIG. 3C where the TiN film 34 was formed were observed with an SEM, the structure was as shown in FIG. FIG. 5A is a view of the TiN film 34 as viewed from above, and FIG. 5B is a cross-sectional view of the TiN film 34. Submicron-order minute holes were uniformly formed on the surface of the TiN film, and the underlying GaN crystal surface was partially exposed.

This was put into an HVPE furnace, heated to 1040 ° C. in an N ₂ atmosphere, GaN having a thickness of 300 μm was deposited, and an HVPE-GaN layer 36 was provided (FIG. 3D). The raw materials used for the growth are NH ₃ and GaCl. Moreover, the GaCl partial pressure and the NH ₃ partial pressure in the supply gas are 8 × 10 ⁻³ atm and 8 × 10 ⁻² atm, respectively. Growth was carried out at normal pressure, and the growth temperature was 1040 ° C. N ₂ was used as the carrier gas. The reason why N ₂ is used as a carrier gas is to promote the formation of voids 35 on the TiN film. In addition to N _2, the same effect can be obtained by using an inert gas such as Ar or He.

  The HVPE-GaN layer 36 was naturally peeled from the sapphire substrate 31 in the temperature lowering process after the growth was finished with the gap 35 as a peeling location. At the interface of the peeled HVPE-GaN layer 36, since the voids 35 are exposed on the surface, fine irregularities were observed on the entire surface. The surface having the irregularities was finished flat by polishing with diamond abrasive grains. As a result, a single-crystal GaN free-standing substrate 37 was obtained (FIG. 3E).

  The surface of the obtained GaN free-standing substrate 37 is very flat, and is equal to or higher than that of a conventional GaN layer grown on a sapphire substrate via a low-temperature growth buffer layer by microscopic observation and SEM observation. The surface condition was good. Moreover, when the porosity of the GaN layer was estimated from the cross-sectional SEM photograph of another sample prepared in the same manner as described above, it was about 50%.

Further, when the warpage of the obtained GaN free-standing substrate 37 was measured, it was confirmed that the curvature radius of the warpage of the substrate was about 12 m, which was a very flat substrate. Further, the surface of the obtained GaN free-standing substrate 37 (surface opposite to the side from which the base substrate was peeled) was immersed in a hot phosphoric acid / sulfuric acid mixed solution (250 ° C.), and the dislocation density was examined by etch pits. It was confirmed that the substrate was extremely low at 10 ⁶ pieces / cm ² and had high crystallinity.

(Example 3)
Each step of the present embodiment will be described with reference to FIG. First, an undoped GaN layer 62 of 1 μm was grown on the C-plane of a single crystal sapphire substrate 61 (FIG. 6A) having a diameter of 2 inches by MOVPE using TMG and NH ₃ as raw materials (FIG. 6B). On the GaN epitaxial substrate thus obtained, metal Ti was deposited by 20 nm to provide a metal Ti film 63 (FIG. 6C). The deposition rate was 0.8 nm / sec. This substrate was placed in an electric furnace and subjected to a heat treatment at 1050 ° C. for 30 minutes in an N ₂ stream containing 20% NH ₃ to form a TiN film 64 (FIG. 6D). When the surface and the cross section were observed with an SEM, fine holes of submicron order were uniformly formed on the surface of the TiN film, and the surface of the underlying GaN crystal was partially exposed.

This was put in an HVPE furnace, heated to 1040 ° C. in an N ₂ atmosphere, GaN was deposited to a thickness of about 300 μm, and an HVPE-GaN layer 66 was provided (FIG. 6E). This layer was grown in two stages.

The raw materials used for the first stage growth are NH ₃ and GaCl. The GaCl partial pressure and NH ₃ partial pressure in the supply gas were 8 × 10 ⁻³ atm and 5.6 × 10 ⁻² atm, respectively, and the V / III ratio was 7. Growth was performed at atmospheric pressure, as a carrier gas N ₂ was used mixed with H ₂ 10%. Under this condition, GaN was grown to about 20 μm, and then the carrier gas was switched to H ₂ to continue the second stage GaN growth. At this time, the GaCl partial pressure and the NH ₃ partial pressure in the supply gas in the growth with the H ₂ carrier gas were set to 1 × 10 ⁻² atm and 2.5 × 10 ⁻¹ atm, respectively. A GaN layer having a thickness of 300 μm was grown by the above two-stage growth. The surface of the GaN layer was suppressed in abnormal growth and improved in surface morphology as compared with the case where all growth was performed in N ₂ carrier gas. The HVPE-GaN layer 66 was naturally peeled from the sapphire substrate 61 in the temperature lowering process after the growth was finished, using the gap 65 as a peeling portion. On the peeled surface of the peeled HVPE-GaN layer 66, since the voids 65 are exposed on the surface, fine irregularities were observed on the entire surface. The surface having the irregularities was finished flat by polishing with diamond abrasive grains. As a result, a single crystal GaN free-standing substrate 67 was obtained (FIG. 6 (f)).

  The surface of the obtained GaN free-standing substrate 67 is very flat, and is equal to or higher than that of a conventional GaN layer grown on a sapphire substrate via a low-temperature growth buffer layer by microscopic observation and SEM observation. It was confirmed that the surface condition was good. Moreover, when the porosity of the GaN layer was estimated from the cross-sectional SEM photograph of another sample prepared in the same manner as described above, it was about 50%.

When the warpage of the obtained GaN free-standing substrate 67 was measured, the curvature radius of the warpage of the substrate was about 11 m, which was a very flat substrate. Further, the surface of the obtained GaN free-standing substrate 67 (surface opposite to the side on which the base substrate was peeled) was immersed in hot phosphoric acid and sulfuric acid mixed solution (250 ° C.), and the dislocation density was examined by etch pits. It was confirmed that the substrate had a very low crystallinity of ⁶ / cm ² and high crystallinity.

Example 4
Each step of the present embodiment will be described with reference to FIG. An undoped GaN layer 62 of 1 μm was grown on the C-plane of a single crystal sapphire substrate 61 having a diameter of 2 inches by MOVPE using TMG and NH ₃ as raw materials (FIG. 6B). On the GaN epitaxial substrate thus obtained, metal Ti was deposited by 20 nm to provide a metal Ti film 63 (FIG. 6C). The deposition rate was 0.8 nm / sec. This substrate was placed in an electric furnace and subjected to a heat treatment at 1050 ° C. for 30 minutes in an N ₂ stream containing 20% NH ₃ to form a TiN film 64 (FIG. 6D). When this surface and cross section were observed with an SEM, fine holes of submicron order were uniformly formed on the surface of the TiN film, and the underlying GaN crystal surface was partially exposed.

The substrate thus obtained was placed in an HVPE furnace, heated to 1040 ° C. in an H ₂ atmosphere, and GaN was deposited to a thickness of about 300 μm. This layer was grown in two stages.

The raw materials used for the first stage growth are NH ₃ and GaCl. The GaCl partial pressure and NH ₃ partial pressure in the supply gas are 8 × 10 ⁻³ atm and 1 × 10 ⁻¹ atm (V / III ratio is 12.5), respectively, and the growth is performed at normal pressure. N ₂ was used as the gas. Under this condition, GaN was grown to about 20 μm, and then the carrier gas was switched to H ₂ to continue the second stage GaN growth. At this time, the GaCl partial pressure and the NH ₃ partial pressure in the supply gas in the growth with the H ₂ carrier gas were set to 1 × 10 ⁻² atm and 2.5 × 10 ⁻¹ atm, respectively. A GaN layer having a thickness of 300 μm was grown by the above two-stage growth.

The surface of the GaN layer was suppressed in abnormal growth and improved in surface morphology as compared with the case where all growth was performed in N ₂ carrier gas. The HVPE-GaN layer 66 was naturally peeled from the sapphire substrate 61 in the temperature lowering process after the growth was finished, using the gap 65 as a peeling portion. At the interface of the peeled HVPE-GaN layer 66, since voids 65 are exposed on the surface, fine irregularities were observed on the entire surface. The surface having the irregularities was finished flat by polishing with diamond abrasive grains. As a result, a single crystal GaN free-standing substrate 67 was obtained (FIG. 6 (f)).

  The surface of the obtained GaN free-standing substrate 67 is very flat, and is equal to or higher than that of a conventional GaN layer grown on a sapphire substrate via a low-temperature growth buffer layer by microscopic observation and SEM observation. It was confirmed that the surface condition was good. Moreover, when the porosity of the GaN layer was estimated from the cross-sectional SEM photograph of another sample prepared in the same manner as described above, it was about 60%.

When the warpage of the obtained GaN free-standing substrate 67 was measured, the curvature radius of the warpage of the substrate was about 13 m, which was a very flat substrate. Further, the surface of the obtained GaN free-standing substrate 67 (surface opposite to the side from which the base substrate was peeled) was immersed in a mixed solution of hot phosphoric acid and sulfuric acid (250 ° C.), and the dislocation density was examined by etch pits. It was confirmed that the substrate was very low at 10 ⁵ pieces / cm ² and had high crystallinity.

In the above embodiment, the surface of the TiN film is reduced in an H ₂ atmosphere, but a wet treatment using an HF solution can be used instead of this treatment. For example, the void 65 can be suitably formed in the GaN layer by the treatment of immersing in HF for 30 minutes and washing with water.

Comparative Example 1
In this comparative example, a Ti film is deposited on a single crystal sapphire C-plane substrate having a diameter of 2 inches at a deposition rate of about 2 nm / sec to 100 nm, and a gold film is formed thereon with a thickness of 10 to 20 nm to prevent oxidation. Vapor deposited. This substrate was placed in an MBE furnace (molecular beam crystal growth furnace), and a GaN layer (film thickness 0.5 μm) was grown on the substrate at 700 ° C. In this comparative example, formation of voids in the GaN layer on the gold film can be suppressed.

  When the substrate taken out of the MBE furnace was immersed in hydrofluoric acid, the Ti film was selectively etched, but the GaN epitaxial layer was shattered.

  Table 1 shows the experimental conditions and evaluation results of the above Examples and Comparative Examples. In the table, “process” indicates which of the above-mentioned types I to IV is applicable, and for a plurality of applicable types, the intended main type of the embodiment is described. In addition, “GaN growth” indicates a condition for growing GaN formed immediately above Ti or TiN.

  In each of the above embodiments, a porous layer including a void is formed, which facilitates peeling of the substrate and significantly reduces the warp, thereby greatly reducing the substrate surface defect density. It became clear.

  Although the present invention has been described above based on the embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit of the present invention. Hereinafter, such modifications will be described.

  In the above embodiment, the sapphire substrate having the C plane as the growth surface is used as the base substrate, but a sapphire substrate having the A plane as the growth surface may be used. The A-plane sapphire can be easily increased in diameter compared to the C-plane sapphire, and a large-diameter group III nitride semiconductor substrate can be obtained.

  In the above embodiment, the present invention is applied to a method of manufacturing a GaN substrate. However, a ternary mixed crystal single crystal free-standing substrate such as aluminum gallium nitride or gallium indium nitride is manufactured, Mg or the like is used. It is also possible to apply to the manufacture of a doped p-type GaN substrate.

  Moreover, in the said Example, although Ti film | membrane was used as a metal film, you may use the film | membrane which consists of another metal material. According to the study by the present inventors, it has been confirmed that even when platinum, nickel, tungsten or the like is used as the metal film material, a void can be formed in the group III nitride semiconductor layer formed thereon. A metal film or a metal nitride film made of such a metal material may be used. An alloy film can also be used. Furthermore, it is possible to employ a method in which GaN is grown after an element such as silicon having a surfactant effect is adsorbed on the surface of the metal film to further reduce the defect density.

  In addition, although a simple self-forming method was used for forming the TiN film having micropores, it may of course be formed by photolithography after the film formation by the sputtering method.

  Further, when forming a GaN layer on a Ti or TiN film, selective growth using a mask such as ELO or FIELO may be employed.

  The group III nitride semiconductor substrate obtained by the present invention can be widely used as a substrate for a GaN-based device. In particular, when used as a laser diode substrate, a high-quality GaN-based crystal with a low defect density can be obtained, so that a highly reliable and high-performance laser diode can be manufactured.

It is process sectional drawing which shows the manufacturing method of the semiconductor substrate which concerns on this invention. It is a drawing substitute photograph which shows the SEM observation result in an Example. It is process sectional drawing which shows the manufacturing method of the semiconductor substrate which concerns on this invention. It is a figure which shows the X-ray-diffraction measurement result in an Example. It is a drawing substitute photograph which shows the SEM observation result in an Example. It is process sectional drawing which shows the manufacturing method of the semiconductor substrate which concerns on this invention.

Explanation of symbols

11 Sapphire substrate 12 Metal Ti film 13 First GaN layer 14 Void 15 TiN film 16 Second GaN layer 17 GaN free-standing substrate 31 Sapphire substrate 32 GaN layer 34 TiN film 35 Void 36 HVPE-GaN layer 37 GaN free-standing substrate 61 Sapphire Substrate 62 GaN layer 63 Metal Ti film 64 TiN film 65 Void 66 HVPE-GaN layer 67 GaN free-standing substrate

Claims (14)

Forming a metal element-containing film on the base substrate;
Growing a first group III nitride semiconductor layer in contact with the metal element-containing film;
Heat-treating the metal element-containing film and the first group III nitride semiconductor layer at a temperature higher than the growth temperature of the first group III nitride semiconductor layer, and in the first group III nitride semiconductor layer Forming a void,
Forming a second group III nitride semiconductor layer on the first group III nitride semiconductor layer;
Peeling and removing the base substrate with the void as a peeling location;
A Group III nitride semiconductor substrate, wherein the metal element-containing film contains a metal element having a decomposition action on a Group III nitride semiconductor. In the group III nitride semiconductor substrate according to claim 1 ,
A group III nitride semiconductor substrate, wherein a growth temperature of the first group III nitride semiconductor layer is 400 ° C. or higher and 800 ° C. or lower. In the group III nitride semiconductor substrate according to claim 1 or 2 ,
A group III nitride semiconductor substrate, wherein the heat treatment of the first group III nitride semiconductor layer is performed at a temperature of 900 ° C. or higher and 1400 ° C. or lower. In the group III nitride semiconductor substrate according to any one of claims 1 to 3 ,
A group III nitride semiconductor substrate, wherein the thickness of the first group III nitride semiconductor layer is 20 nm or more and 2000 nm or less. In the group III nitride semiconductor substrate according to any one of claims 1 to 4 ,
The group III nitride semiconductor substrate, wherein the metal element-containing film is a metal film. The group III nitride semiconductor substrate according to any one of claims 1 to 5 ,
The group III nitride semiconductor substrate, wherein the metal element is a transition element. The group III nitride semiconductor substrate according to claim 1 ,
The metal elements are scandium, yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, manganese, copper, platinum Or a group III nitride semiconductor substrate characterized by being gold. In the group III nitride semiconductor substrate according to claim 7,
A group III nitride semiconductor substrate characterized by being made of titanium, zirconium, hafnium, tantalum, platinum, cobalt, or nickel. Forming a metal element-containing film having at least a surface made of metal nitride on a base substrate;
A step of growing a group III nitride semiconductor in contact with the metal element-containing film under a condition where the V / III ratio of the source gas is 10 or less to form a group III nitride semiconductor layer including a void;
Peeling and removing the base substrate with the void as a peeling location;
A Group III nitride semiconductor substrate, wherein the metal element-containing film contains a metal element having a decomposition action on a Group III nitride semiconductor. In the group III nitride semiconductor substrate according to claim 9 ,
The group III nitride semiconductor substrate, wherein the metal element is a transition element. In the group III nitride semiconductor substrate according to claim 9 or 10 ,
The metal elements are scandium, yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, manganese, copper, platinum Or a group III nitride semiconductor substrate characterized by being gold. In the group III nitride semiconductor substrate according to claim 11 ,
The group III nitride semiconductor substrate, wherein the metal element is titanium, zirconium, hafnium, tantalum, platinum, cobalt, or nickel. The group III nitride semiconductor substrate according to any one of claims 1 to 12 ,
A group III nitride semiconductor substrate, wherein the metal element-containing film is formed on the entire surface of the base substrate. The group III nitride semiconductor substrate according to any one of claims 1 to 13 ,
The step of peeling and removing the base substrate includes a step of naturally peeling the base substrate by lowering the ambient temperature after growing the group III nitride semiconductor layer. .

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