JP2016174069A - Method for manufacturing group iii nitride semiconductor substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for delaminating a base substrate and a group III nitride semiconductor layer from each other.SOLUTION: A method for manufacturing a group III nitride semiconductor substrate comprises: an XC layer formation step for forming a TiC layer (XC layer 12) on a sapphire substrate 10, provided that the TiC layer is arranged by alternately and continuously laminating a Ti film (X film 12-1) and a C film 12-2, which are each controlled to have a given thickness, followed by heating; a group III nitride semiconductor layer formation step for forming a group III nitride semiconductor layer 14 on the TiC layer (XC layer 12); and a separation step for separating the sapphire substrate 10 and the group III nitride semiconductor layer 14 from each other.SELECTED DRAWING: Figure 12

Description

  The present invention relates to a method for manufacturing a group III nitride semiconductor substrate.

  In recent years, attempts have been made to use a group III nitride semiconductor such as a gallium nitride (GaN) crystal as a substrate for producing a blue-violet laser or a white light emitting diode. However, it is difficult to obtain a large-diameter GaN bulk crystal because the dissociation pressure of nitrogen is high.

  For this reason, for example, a HVPE (hydride vapor phase epitaxy) method is used to manufacture a GaN semiconductor substrate.

  Patent Document 1 discloses a method for manufacturing a GaN semiconductor substrate using the HVPE method. In this manufacturing method, on a sapphire substrate, a mask having a rectangular cross-section covering portion arranged in a stripe shape and an opening formed between the covering portions is formed. The covering part of the mask extends in the <11-20> direction of the sapphire substrate and the <1-100> direction of the GaN semiconductor.

  After the mask is formed, a GaN semiconductor layer is grown from the opening, and the growth is stopped without completely covering the upper surface of the covering portion of the mask. Next, the mask is removed by dry etching, and a GaN semiconductor layer is further grown on the GaN semiconductor layer. Thereafter, the sapphire substrate is peeled off as it is to obtain a GaN semiconductor substrate.

  However, in the conventional method of manufacturing a GaN semiconductor substrate, when the sapphire substrate is peeled from the GaN semiconductor layer, the GaN semiconductor layer is often damaged, and in a severe case, the GaN semiconductor layer may be shattered. It was.

  In order to solve such problems, various methods for peeling the sapphire substrate have been proposed.

  As a conventional method for peeling the sapphire substrate, for example, a method described in Patent Document 2 can be cited. In this method, laser light is irradiated from the sapphire substrate side while heating the GaN semiconductor layer. As the laser light, a YAG laser having a wavelength of 355 nm is used. The laser light is absorbed by the GaN semiconductor layer, whereby GaN near the interface between the sapphire substrate and the GaN semiconductor layer is thermally decomposed and delamination occurs.

  Moreover, the method described in patent document 3 is also mentioned as a conventional method of peeling a sapphire substrate. In this method, a metal film (for example, an aluminum film) is deposited on a sapphire substrate, GaN is grown on the metal film, and a GaN semiconductor layer is formed. Then, the sapphire substrate is peeled from the GaN semiconductor layer by etching the metal film.

JP 2003-55097 A JP 2002-57119 A JP 2002-284600 A

  However, the technique described in Patent Document 2 requires an expensive laser irradiation device for peeling, and the sapphire substrate must be peeled off while scanning the laser beam. .

  Similarly, the technique described in Patent Document 3 also requires an etching facility for peeling, and the etching solution hardly penetrates the interface between the sapphire substrate and the GaN film, and a metal film having a particularly large area can be completely etched. It takes a long time to remove.

  This invention makes it a subject to provide the new peeling method which can eliminate the problem mentioned above.

According to the present invention,
X films (X is Ti, Al, Zr, Hf, V, or Ta) and C films are alternately and continuously stacked, and an XC layer obtained by heating is formed on a base substrate. An XC layer forming step;
A growth step of forming a group III nitride semiconductor layer on the XC layer;
A separation step of separating the base substrate and the group III nitride semiconductor layer;
There is provided a method for producing a group III nitride semiconductor substrate having:

  According to the present invention, an unprecedented new peeling method is realized.

It is a figure which shows the relationship between the value of 2 (theta) of the TiC layer provided between the sapphire substrate and the group III nitride semiconductor layer, a half value width, and the yield of peeling. It is a schematic diagram which shows an example of the manufacturing process of the manufacturing method of the group III nitride semiconductor substrate of this embodiment. It is a schematic diagram which shows an example of the manufacturing process of the manufacturing method of the group III nitride semiconductor substrate of this embodiment. It is a schematic diagram which shows an example of the manufacturing process of the manufacturing method of the group III nitride semiconductor substrate of this embodiment. It is a schematic diagram which shows an example of the manufacturing process of the manufacturing method of the group III nitride semiconductor substrate of this embodiment. It is a schematic diagram which shows an example of the manufacturing process of the manufacturing method of the group III nitride semiconductor substrate of this embodiment. It is a schematic diagram of an HVPE apparatus. It is a schematic diagram for demonstrating an example of a separation process. It is a schematic diagram for demonstrating an example of a separation process. It is a schematic diagram for demonstrating an example of a separation process. It is a schematic diagram for demonstrating an example of a separation process. It is a figure which shows the effect of the manufacturing method of the group III nitride semiconductor substrate of this embodiment. It is a figure which shows the effect of the manufacturing method of the group III nitride semiconductor substrate of this embodiment. It is a figure which shows the effect of the manufacturing method of the group III nitride semiconductor substrate of this embodiment. It is a figure which shows the effect of the manufacturing method of the group III nitride semiconductor substrate of this embodiment. It is a figure which shows the effect of the manufacturing method of the group III nitride semiconductor substrate of this embodiment. It is a figure which shows the effect of the manufacturing method of the group III nitride semiconductor substrate of this embodiment. It is a figure which shows the effect of the manufacturing method of the group III nitride semiconductor substrate of this embodiment.

  Hereinafter, embodiments of a group III nitride semiconductor substrate and a method for manufacturing a group III nitride semiconductor substrate of the present invention will be described with reference to the drawings. The drawings are only schematic diagrams for explaining the configuration of the invention, and the size, shape, number, and ratio of different member sizes are not limited to those shown in the drawings.

<First Embodiment>
First, an outline of the present embodiment will be described. The present inventors formed a group III nitride semiconductor layer with a XC layer (X is Ti, Al, Zr, Hf, V, or Ta) on a dissimilar substrate such as a sapphire substrate, and then, under predetermined conditions, Invented a peeling method (hereinafter sometimes referred to as “XC layer decomposition peeling”) in which the XC layer is decomposed and deteriorated by heating the laminate, and the dissimilar substrate and the group III nitride semiconductor layer are separated from each other at the decomposition deterioration portion. did. And as a result of earnestly examining the said peeling method, the regularity shown in FIG. 1 was discovered.

  The data shown in FIG. 1 includes the XRD (x-ray diffraction) 2θ peak value of the TiC layer (hereinafter sometimes simply referred to as “2θ value”) and the half-value width (FWHM: full width at) of the X-ray rocking curve. half maximum) (hereinafter simply referred to as “half width”) and the separation yield (hereinafter also referred to simply as “yield”).

  The value of 2θ is the 2θ peak value of TiC (111) measured by XRD using Cu Kα rays. The half width is a value calculated from a TiC (111) rocking curve by ω scan.

  As can be seen from FIG. 1, a high yield can be obtained by appropriately controlling the 2θ value and the half-value width value of the TiC layer. Specifically, the value of 2θ is 35.75 ° or more and 35.95 ° or less, preferably 35.80 ° or more and 35.90 ° or less, and the half-value width is 6000 sec or more, preferably 7000 sec or more, More preferably, it is understood that a high yield can be obtained when it is 8000 sec or more, more preferably 9000 sec or more and 10000 sec or less. The present inventors have confirmed the same regularity when an AlC layer, a ZrC layer, an Hf layer, a V layer, or a Ta layer is employed instead of the TiC layer.

  We have heretofore produced an XC layer by reactive sputtering. However, in the case of this method, it has been difficult to control the 2θ value and the half width value of the XC layer. Therefore, the present inventors have newly invented XC layer decomposition and peeling using a method for generating an XC layer that can control the 2θ value and the half-value width value of the XC layer.

  The present embodiment is characterized by having an XC layer generation method capable of controlling the 2θ value and the half-value width value of the XC layer with respect to the XC layer decomposition peeling. Hereinafter, this embodiment will be described in detail.

The manufacturing method of the group III nitride semiconductor substrate (free-standing substrate) of the present embodiment is as follows:
(1) forming a base C film on the base substrate (base C film forming process);
(2) a step of forming an XC layer on the base C film (XC layer forming step);
(3) a step of nitriding at least a part of the XC layer (nitriding step);
(4) forming a group III nitride semiconductor layer on the nitrided XC layer and separating the base substrate and the group III nitride semiconductor layer by heating (growth step and separation step);
Have

In addition, you may have the following processes after (2) XC layer formation process and before (3) nitriding process.
(2) ′ A step (reactive sputtering step) of forming an XC layer (reactive sputtering XC layer) on the XC layer by reactive sputtering.

  In this case, (3) in the nitriding step, at least a part of the reactive sputtered XC layer and the XC layer is nitrided, and (4) in the growing step and the separating step, the nitrided reactive sputtered XC layer A group III nitride semiconductor layer will be formed thereon.

  Hereinafter, each step will be described in detail.

<Base C film forming process>
In the base C film forming step, a film composed of C (base C film) is formed on the base substrate. First, a base substrate is prepared. The base substrate can be a different substrate from the group III nitride semiconductor layer formed in (4) growth step and separation step. The group III nitride semiconductor layer separated from the base substrate becomes a group III nitride semiconductor substrate (self-standing substrate). In this embodiment, for example, a 3-inch φ sapphire (Al ₂ O ₃ ) substrate 10 having a thickness of 550 μm is prepared as a base substrate.

  The thickness of the base substrate is 250 μm or more and 1500 μm or less, and preferably 400 μm or more and 600 μm or less. If the base substrate is too thick, cracks and cracks will occur due to the stress caused by the difference in thermal expansion coefficient between the base substrate and the group III nitride semiconductor layer during the growth step and separation step described below (4). May end up. Such inconvenience can be reduced by setting the thickness of the base substrate to 400 μm or more and 600 μm or less.

  In this step, a base C film 11 is formed on the sapphire substrate 10 as shown in FIG. As will be described in detail in the following examples, by controlling the thickness of the base C film 11, the half width of the XC layer formed thereon can be controlled. For example, when the XC layer is a TiC layer, the half width of the TiC layer can be controlled to 6000 sec or more by controlling the thickness of the base C film 11 to 1.1 nm or more and 1.3 nm or less. Similarly, when the XC layer is a layer other than the TiC layer, the half width of the XC layer can be controlled to a desired value by controlling the thickness of the base C film 11.

  The base C film 11 can be formed by sputtering, for example. The film forming conditions for the base C film 11 can be set as follows, for example.

Film forming method: Sputtering film forming temperature: 25 to 1000 ° C.
Deposition time: 5 to 300 seconds Pressure: 0.2 to 0.5 Pa
Applied power: 50-300W
Sputtering gas: Ar
Sputtering gas flow rate: 2 to 100 sccm
Target: C

  The thickness of the base C film 11 can be adjusted by adjusting the film formation time and the applied power. The longer the film formation time and the greater the applied power, the thicker the film.

<XC layer formation process>
In the XC layer forming step, X films and C films are alternately and continuously stacked, and an X layer obtained by heating is formed on a base substrate. That is, as shown in FIG. 3, X films 12-1 and C films 12-2 are alternately and continuously stacked on the base C film 11. When this laminated body is heated at a predetermined temperature, X in the X film 12-1 and C in the C film 12-2 become XC, and the XC layer 12 is obtained. At this time, a part of the base C film 11 may react with the adjacent X film 12-1 to become XC. The C film 12-2 is thinner than the base C film 11. That is, the base C film 11 is controlled to have a predetermined thickness that is thicker than the C film 12-2. The heating temperature is adjusted according to the type of X and the like. For example, when X is Ti, the heating temperature of the laminate can be set to 500 ° C. or higher.

  As will be described in detail in the following examples, the orientation of the sapphire substrate 10 can be transferred to the XC layer 12 by controlling the thicknesses of the base C film 11, the X film 12-1, and the C film 12-2. . For example, the thickness of the X film 12-1 is 0.2 nm or more and 1.0 nm or less, the thickness of the C film 12-2 is 0.2 nm or more and 1.0 nm or less, and the thickness of the base C film 11 is 0.2 nm or more. And it is controlled to 1.3 nm or less. By controlling in this way, the orientation of the sapphire substrate 10 can be inherited, and, for example, the (111) -oriented XC layer 12 can be formed.

  Further, as will be described in detail in the following embodiment, 2θ of the XC layer 12 is controlled by controlling the ratio of the thickness T1 of the X film 12-1 and the thickness T2 of the C film 12-2. can do. For example, when the XC layer is a TiC layer, the value of 2θ is 35.75 ° or more and 35.95 ° or less by controlling T1 and T2 so as to satisfy 2/3 ≦ T1 / T2 ≦ 3/2. Can be controlled. Similarly, when the XC layer is a layer other than the TiC layer, 2θ of the XC layer 12 can be controlled to a desired value by controlling the ratio of T1 and T2.

  The thickness of the XC layer 12 is controlled to 5 nm or more and 200 nm or less. When the (2) ′ reactive sputtering step is included, the total film thickness of the XC layer 12 and the reactive sputtering XC layer is controlled to 40 nm or more and 200 nm or less. By controlling the thickness of the XC layer 12 or the total film thickness of the XC layer 12 and the reactive sputtered XC layer in this way, an effect of controlling the crystallinity of the XC layer can be obtained. When the said total film thickness is too large, the crystallinity of a XC layer will worsen and orientation will deteriorate.

  The number of times of repeating the pair of the X film 12-1 and the C film 12-2 is not particularly limited. It can be determined based on the desired thickness of the XC layer 12, the thicknesses of the X film 12-1 and the C film 12-2, and the like.

  The X film 12-1 can be formed by sputtering, for example. Hereinafter, an example of film forming conditions when the X film 12-1 is a Ti film will be described. As shown in the following examples, the value of 2θ of the XC layer 12 can be controlled by controlling the applied power when forming the X film 12-1.

Film forming method: Sputtering film forming temperature: 25 to 1000 ° C.
Deposition time: 5 to 120 seconds Pressure: 0.2 to 0.5 Pa
Applied power: 50-300W
Sputtering gas: Ar
Sputtering gas flow rate: 5-100 sccm
Target: Ti

  The C film 12-2 can be formed by sputtering, for example. The film forming conditions for the C film 12-2 can be set as follows, for example.

Film forming method: Sputtering film forming temperature: 25 to 1000 ° C.
Deposition time: 5 to 120 seconds Pressure: 0.2 to 0.5 Pa
Applied power: 50-300W
Sputtering gas: Ar
Sputtering gas flow rate: 5-100 sccm
Target: C

  Heating for XC conversion may be performed during sputtering for forming the X film 12-1 and the C film 12-2. For example, the film formation temperature when forming the X film 12-1 and the C film 12-2 is set to a predetermined value or higher for XC conversion (when the X film 12-1 is a Ti film, 500 ° C. or higher). Also good. In this case, while the X film 12-1 and the C film 12-2 are repeatedly and continuously formed, the X film 12-1 and the C film 12-2 that have been formed so far become XC. In addition to the sputtering process for forming the X film 12-1 and the C film 12-2, a heating process for XC conversion may be provided.

<Reactive sputtering process>
In the reactive sputtering process, as shown in FIG. 4, an XC layer (reactive sputtering XC layer 13) is formed by reactive sputtering on the XC layer 12 formed in the XC layer forming process.

  The present inventors have confirmed that the reactive sputtered XC layer 13 inherits the crystallinity of the XC layer 12. That is, when the reactive sputter XC layer 13 is formed on the XC layer 12 in which 2θ and the half width are controlled to a desired state, the reactive sputter XC layer 13 has the same 2θ and half width as the XC layer 12. Show. Note that Xs of the XC layer 12 and the reactive sputtered XC layer 13 coincide with each other.

  The reactive sputtered XC layer 13 has a function of supplementing the thickness of the XC layer 12. The thickness T4 of the XC layer 12 and the thickness T5 of the reactive sputtered XC layer 13 satisfy 40 ≦ (T4 + T5) ≦ 200.

  However, as shown in the following examples, the half width of the reactive sputtered XC layer 13 can be controlled by providing the reactive sputtered XC layer 13 and controlling the thickness thereof. Specifically, the full width at half maximum increases as the film thickness increases.

  Thus, by providing the reactive sputtering step, the parameter for controlling the half width of the XC layer (XC layer 12 and / or reactive sputtered XC layer 13) is increased. As a result, the half width of the XC layer (XC layer 12 and / or reactive sputtered XC layer 13) can be easily controlled, which is preferable. On the other hand, when the reactive sputtering process is not provided, there is an advantage that the number of processes is reduced and work efficiency is improved. In the case of this embodiment, these can be used properly according to the situation.

  The reactive sputtered XC layer 13 is formed by reactive sputtering. The film formation conditions are a matter of design. Hereinafter, an example of film forming conditions when the reactive sputtered XC layer 13 is a TiC layer will be shown.

Film forming method: reactive sputtering film forming temperature: 500 to 1000 ° C.
Deposition time: 4.5 to 114 minutes Pressure: 0.2 to 0.5 Pa
Applied power: 100-300W
Sputtering gas: Ar gas Sputtering gas flow rate: 5-50 sccm
Reactive gas: CH ₄
Reactive gas flow rate: 10.0sccm
Target: Ti
Film thickness: 20 nm to 200 nm

<Cap layer forming step>
Although not described above, a cap layer forming step may be provided after (2) the XC layer forming step and (2) ′ reactive sputtering step and (3) before the nitriding step. In the cap layer forming step, a cap layer is formed on the XC layer 12 or the reactive sputtered XC layer 13.

  The cap layer can be a C film in which XC is dispersed. The film formation conditions are a matter of design. Hereinafter, an example of film formation conditions when the C film in which XC is dispersed is a C film in which TiC is dispersed will be described.

Deposition method: Reactive sputtering Deposition temperature: 25-1000 ° C
Deposition time: 2.5-25 minutes Pressure: 0.3-0.5 Pa
Applied power: 100-300W
Reactive gas: CH ₄
Reactive gas flow rate: 10.0sccm
Target: Ti
Film thickness: 5 nm to 50 nm

  When reactive sputtering is performed under conditions where the amount of introduced hydrocarbon is larger, more XC can be dispersed in the cap layer. In the case of the above conditions, the amount of XC dispersed in the cap layer can be adjusted by appropriately adjusting the supply amount of methane gas. That is, by appropriately adjusting the supply amount of methane gas, the atomic ratio C / X of X and C in the cap layer can be adjusted to a desired value.

  In addition, when reactive sputtering is performed under a condition where the applied power is increased, more XC can be dispersed in the cap layer. That is, by appropriately adjusting the applied power, the amount of XC dispersed in the cap layer can be adjusted, and the atomic ratio C / X of X and C in the cap layer can be adjusted to a desired value.

  The cap layer is a film containing C as a main component, the C film as a base material, and a film containing XC in the base material. For example, C is a sea state (matrix), and XC is dispersed in this matrix.

  The XC concentration in the cap layer is lower than the concentration of C alone (C excluding C existing as XC). For example, the XC concentration in the cap layer is 33 to 49%.

  The film formation temperature of the cap layer may be 25 ° C. or higher. Specifically, it is preferable to form a film at 600 ° C. or higher, particularly 800 ° C. or higher. By doing so, the cap layer becomes a dense film, and oxidation of the XC layer 12 and the reactive sputtered XC layer 13 can be effectively prevented.

  Further, the film thickness of the cap layer is preferably 5 nm or more and 50 nm or less, and more preferably 10 nm or more. By setting the cap layer to 10 nm or more, oxidation of the XC layer 12 and the reactive sputtered XC layer 13 can be effectively prevented. The cap layer may completely cover the entire surface of the XC layer 12 or the reactive sputtered XC layer 13.

<Nitriding process>
In the nitriding step, at least a part of the XC layer including the XC layer 12 and / or the reactive sputtered XC layer 13 is nitrided.

  For example, an XC layer composed of the XC layer 12 and / or the reactive sputtered XC layer 13 is partially nitrided in an atmosphere of 300 ° C. or higher and 1000 ° C. or lower to form a nitrided XC layer. The nitrided XC layer has a laminated structure of an XC layer mainly containing XC and an XN layer mainly containing XN. The nitriding conditions are, for example, as follows.

Nitriding temperature: 300 ° C to 950 ° C
Nitriding time: 5 to 30 minutes Nitriding gas: NH ₃ gas, H ₂ gas, N ₂ gas

When the cap layer is formed, the XC layer 12 and the reactive sputtered XC layer 13 are covered with the cap layer. However, in the nitriding process, carbon in the cap layer is vaporized as CH ₄ by the nitriding gas. For this reason, a gap reaching the XC layer composed of the XC layer 12 and / or the reactive sputtered XC layer 13 is generated in the cap layer. Then, the nitriding gas reaches the XC layer through this gap, and these are partially nitrided.

  The nitriding temperature is more preferably 500 ° C. or more and 700 ° C. or less, and particularly preferably 550 ° C. or less. By setting the nitriding temperature to 500 ° C. or higher, there is an effect of increasing the nitriding rate.

When the nitriding temperature is higher than 550 ° C., CH ₄ is decomposed and C is precipitated as shown in the formula (1), and C is mixed into XN, so that the crystallinity of the group III nitride semiconductor layer is lowered. There is a case. In order to suppress the precipitation of C, it is effective to increase the introduction of hydrogen and the partial pressure of ammonia.

CH ₄ → C + 2H ₂ ... (1) Formula

  The nitriding time is preferably 30 minutes or less. By setting the nitriding time to about 30 minutes, the XC layer 12 and / or the reactive sputtered XC layer 13 can be appropriately nitrided.

  Note that ammonia is preferable as a reaction gas for nitriding. XN can be formed even when nitrogen is used as a reaction gas in addition to ammonia. However, when XN and C are generated as shown in the formula (2) and C is mixed into XN, the crystal of the group III nitride semiconductor layer is formed. May affect quality.

2XC + N ₂ → 2XN + 2C (2) formula

  When the cap layer is formed, XC contained in the cap layer is partially nitrided by the nitriding step to form a nitrided cap layer. In some cases, XC contained in the first layer 11 is partially nitrided to become XN.

<Growth process and separation process>
In the growth step and the separation step, a group III nitride semiconductor layer is formed on the nitrided XC layer (growth step), and the base substrate (sapphire substrate 10) and the group III nitride semiconductor layer are formed by heating. Separate (separation step). That is, the group III nitride semiconductor layer is formed on the nitrided XC layer 12 or the nitrided reactive sputtered XC layer 13.

  The growth step and the separation step may be separate steps or a single step. That is, the process for forming the group III nitride semiconductor layer and the process for separating the sapphire substrate 10 and the group III nitride semiconductor layer by heating may be performed separately. Alternatively, the separation may be performed by heating at the time of processing for forming the group III nitride semiconductor layer. That is, the process of forming the group III nitride semiconductor layer and the process of separating the sapphire substrate 10 and the group III nitride semiconductor layer by heating may be realized by the same process.

  First, an example in which the growth process and the separation process are performed separately will be described.

"Growth process"
In this step, as shown in FIG. 5 and FIG. 6, a nitrided XC layer 12 (hereinafter sometimes simply referred to as “XC layer 12”) or a nitrided reactive sputtered XC layer 13 (hereinafter simply referred to as “XC layer 12”). A group III nitride semiconductor layer 14 is formed on the “reactive sputtered XC layer 13”. When the cap layer is formed, the group III nitride semiconductor layer 14 is formed on the nitrided cap layer. Here, a GaN semiconductor layer is epitaxially grown as the group III nitride semiconductor layer 14. The group III nitride semiconductor layer 14 is not limited to a GaN semiconductor layer, and may be, for example, AlGaN. The growth conditions of the GaN semiconductor layer can be set as follows, for example.

Film forming method: HVPE (hydride vapor phase epitaxy) film forming temperature: 1000 ° C. to 1050 ° C.
Deposition time: 30 minutes to 500 minutes Film thickness: 100 μm to 1500 μm

  In addition, after forming the low-temperature growth buffer layer of the group III nitride semiconductor at a temperature lower than the film formation temperature, the group III nitride semiconductor may be epitaxially grown under the above growth conditions.

  Further, after forming the group III nitride semiconductor facets, the group III nitride semiconductor may be epitaxially grown under the above growth conditions to obtain the group III nitride semiconductor layer 14 which is a flat film.

  Here, the hydride vapor phase epitaxy (HVPE) apparatus 3 will be briefly described with reference to FIG. FIG. 7 is a schematic diagram of the HVPE apparatus 3.

  The HVPE apparatus 3 includes a reaction tube 31 and a substrate holder 32 provided in the reaction tube 31. The HVPE apparatus 3 includes a group III source gas supply unit 33 that supplies a group III source gas into the reaction tube 31 and a nitrogen source gas supply unit 34 that supplies a nitrogen source gas into the reaction tube 31. Further, the HVPE apparatus 3 includes a gas discharge pipe 35 and heaters 36 and 37.

  The substrate holder 32 is rotatably provided on the downstream side of the reaction tube 31 by a rotation shaft 41. The gas discharge pipe 35 is provided on the downstream side of the substrate holder 32 in the reaction pipe 31.

  The group III source gas supply unit 33 includes a gas supply pipe 311, a source boat 312, a group III (Ga) source 313, and a layer below the shielding plate 38 among the reaction tubes 31.

  The nitrogen source gas supply unit 34 includes a gas supply pipe 341 and a layer on the shielding plate 38 in the reaction pipe 31.

  The group III source gas supply unit 33 generates a halide of a group III atom (for example, GaCl), which is nitrided XC layer 12 of the laminated body on the substrate holder 32 or the nitrided reactive sputter XC. Supply to the surface of layer 13 or the nitrided cap layer. In addition, in FIG.

  The supply port of the gas supply pipe 311 is arranged on the upstream side in the group III source gas supply unit 33. For this reason, the supplied hydrogen halide gas (for example, HCl gas) comes into contact with the group III material 313 in the source boat 312 in the group III material gas supply unit 33.

  Thereby, the halogen-containing gas supplied from the gas supply pipe 311 comes into contact with the surface of the group III raw material 313 in the source boat 312 or the volatilized group III molecule, and the group III molecule is halogenated to form a group III halide. A Group III source gas is produced. A heater 36 is disposed around the group III source gas supply unit 33, and the group III source gas supply unit 33 is maintained at a temperature of about 800 to 900 ° C., for example.

  The upstream side of the reaction tube 31 is divided into two layers by a shielding plate 38. Ammonia supplied from the gas supply pipe 341 passes through the nitrogen source gas supply unit 34 located above the shielding plate 38 in the drawing, and decomposition is accelerated by heat. A heater 36 is disposed around the nitrogen source gas supply unit 34, and the nitrogen source gas supply unit 34 is maintained at a temperature of about 800 to 900 ° C., for example.

  In the growth region 39 located on the right side in the figure, a substrate holder 32 is disposed, and a group III nitride semiconductor such as GaN is grown in the growth region 39. A heater 37 is arranged around the growth region 39, and the inside of the growth region 39 is maintained at a temperature of about 1000 ° C. to 1050 ° C., for example.

  The thickness of group III nitride semiconductor layer 14 is, for example, 600 μm or less from the viewpoint of reducing the stress generated by the difference in linear expansion coefficient between sapphire substrate 10 (underlying substrate) and group III nitride semiconductor layer 14. In particular, it is preferably 450 μm or less, and more preferably 300 μm or less. Furthermore, the thickness of the group III nitride semiconductor layer 14 is preferably 50 μm or more from the viewpoint of handleability.

"Separation process"
In this step, after the process of forming the group III nitride semiconductor layer 14, the stacked body including the group III nitride semiconductor layer 14 is heated more than when the group III nitride semiconductor layer 14 is formed. Heat at high temperature.

  By the heating, the XC layer composed of the XC layer 12 and / or the reactive sputtered XC layer 13 is decomposed and deteriorated. Then, the sapphire substrate 10 and the group III nitride semiconductor layer 14 are separated using the decomposed and degraded portion as a separation position. Thus, in the case of the method, the separation position can be controlled to one of the XC layers including the XC layer 12 and / or the reactive sputtered XC layer 13. That is, it is possible to reduce the inconvenience that the separation position is generated in the group III nitride semiconductor layer 14 or the like. Further, the variation in shape after separation can be reduced by controlling the separation position.

  In the separation treatment, for example, the laminate is heated at a temperature higher than 1050 ° C. and lower than or equal to 1200 ° C., more preferably higher than 1050 ° C. and lower than or equal to 1195 ° C., more preferably higher than 1100 ° C. and lower than or equal to 1190 ° C. . When the heating temperature is increased, decomposition and deterioration of the XC layer can be promoted, but dislocations are likely to occur in the group III nitride semiconductor layer 14.

  In the separation step, the laminate is heated at the above temperature for 5 hours to 30 hours. If the heating time is long, dislocations are likely to occur in the group III nitride semiconductor layer 14, and the manufacturing time of the free-standing substrate is long, resulting in poor production efficiency.

  Here, a specific example of heat treatment in the separation step is shown.

<First heat treatment example>
After the process of forming the group III nitride semiconductor layer 14, the stacked body after the formation of the group III nitride semiconductor layer 14 is cooled to room temperature (room temperature), whereby the sapphire substrate 10 and the group III nitride semiconductor are formed. The sapphire substrate 10 and the group III nitride semiconductor layer 14 may be separated on the basis of the stress caused by the difference in linear expansion coefficient from the layer 14. In the case of separation by such a mechanism, the separation position or the separation shape of the sapphire substrate 10 and the group III nitride semiconductor layer 14 is likely to vary. There is a concern that the productivity of the group III nitride semiconductor substrate may be reduced due to this variation.

  Therefore, in the heat treatment, the stacked body in the heated state after the formation of the group III nitride semiconductor layer 14 by the process of forming the group III nitride semiconductor layer 14 is not cooled to room temperature (room temperature) without being grown. After that, the laminated body may be heated at a temperature higher than the temperature of epitaxial growth. The heating can be performed using, for example, an HVPE apparatus in which the group III nitride semiconductor layer 14 is formed.

  For example, after forming the group III nitride semiconductor layer 14 with the HVPE apparatus, the supply of the source gas and the reactive gas is stopped while the stacked body is housed in the HVPE apparatus, and the heater temperature is raised to a desired value. The laminate may be heated.

<Second heat treatment example>
For example, after forming the group III nitride semiconductor layer 14 by controlling the conditions of the nitriding step or controlling the relationship between the thickness of the sapphire substrate 10 and the group III nitride semiconductor layer 14, the stacked body may be cooled to room temperature. The sapphire substrate 10 and the group III nitride semiconductor layer 14 can be controlled so as not to separate based on the stress caused by the difference in linear expansion coefficient. In such a case, after the group III nitride semiconductor layer 14 is formed, the stacked body is once cooled to room temperature, and then heat treatment can be performed.

The control of the conditions of the nitriding step is, for example, control of the flow rate (partial pressure) of NH ₃ gas (nitriding gas). When the flow rate of the NH ₃ gas is small, the sapphire substrate 10 and the group III nitride semiconductor layer 14 are easily separated by cooling after the processing for forming the group III nitride semiconductor layer 14. On the other hand, when the flow rate of the NH ₃ gas is large, the sapphire substrate 10 and the group III nitride semiconductor layer 14 are difficult to separate by cooling after the processing for forming the group III nitride semiconductor layer 14.

  Also in this example, the HVPE apparatus 3 can be used for heating the laminate. For example, the laminated body may be arranged and heated in a region surrounded by the heater 37 shown in FIG. 7 (for example, downstream of the pipe 40 and in the growth region 39).

  For example, a jig 55 having a recess 511 formed on the surface as shown in FIG. 8 is prepared, and the laminate B is inserted into the recess 511. Then, the laminate B together with such a jig 55 is accommodated in the HVPE apparatus 3. Then, the heaters 36 and 37 are driven to heat the plurality of stacked bodies B at the same time. During the heat treatment, the growth of the group III nitride semiconductor layer 14 is stopped. In addition, a heat treatment apparatus may be prepared separately from the HVPE apparatus 3, and the laminated body may be heat-treated.

<Third heat treatment example>
Also in this example, the laminated body is cooled to room temperature and then heat treatment is performed. For example, the laminated body B is heated in a state of being immersed in a liquid of a group III element. The group III element liquid is a liquid of the same element as the group III element contained in the group III nitride semiconductor layer 14. For example, when the group III nitride semiconductor layer 14 is GaN, the group III element liquid is a Ga liquid.

  The group III element liquid may be any liquid that becomes liquid at least at the heat treatment temperature of the laminate. For example, even if it is solid at 25 ° C., it may be liquid at the heat treatment temperature of the laminate. When it is solid at 25 ° C., for example, a powder of a group III element may be put in containers 5 and 6 described later.

  For example, a container 5 as shown in FIGS. 9 and 10 is prepared. FIG. 9 is a cross-sectional view orthogonal to the bottom surface of the container 5. FIG. 10 is a perspective view of the container 5, and is a view showing the laminated body B disposed inside.

  The container 5 includes a container main body 50 whose upper surface is open, a lid 53 that closes the opening of the container main body 50, and a pin 52, and is configured to accommodate a plurality of laminates B inside the container main body 50. Yes.

  The container 5 is made of a heat-resistant material. For example, the container body 50, the lid 53, and the pins 52 are made of graphite.

  A plurality of pins 52 are inserted into the side wall 51 of the container body 50. Among the plurality of pins 52, some of the pins 52 have different attachment positions in the height direction with respect to the side wall 51 of the container 5, and are arranged in the order of the pins 52 </ b> A to 52 </ b> D from the bottom surface side of the container 5.

  First, the pins 52 </ b> A to 52 </ b> D inserted into the side wall 51 are pulled out from the side wall 51 of the container 5 to a certain extent. However, the pins 52A to 52D are not completely pulled out. Next, a predetermined amount of Group III element liquid is placed in the container 5, and then the laminate B is placed in the container 5. The laminated body B is inserted into the container 5 so that the sapphire substrate 10 is on the upper side of the container 5. The laminate B will float in the liquid due to buoyancy. Then, the pin 52 </ b> A is pushed into the container 5, and the outer peripheral edge of the sapphire substrate 10 of the laminate B is pressed with the pin 52.

  Thereafter, the liquid of the group III element is again filled in the container 5, and the second laminate B is inserted into the container 5. Then, the pin 52B at a position higher than the pin 52A is pushed into the inside of the container 5, and the outer peripheral edge of the sapphire substrate 10 of the second laminate B is pressed with the pin 52B. Such an operation is repeated, and the outer peripheral edge of the sapphire substrate 10 of each stacked body B is pressed by the pins 52A to 52D.

  If such a container 5 is used, a plurality of laminated bodies B can be immersed in the liquid L of a group III element in the container 5. In the container 5, the whole laminated body B will be immersed in the liquid L of a III group element.

  Thereafter, the lid 53 is fitted into the opening of the container 5. Then, the container 5 filled with the group L element liquid L and having the plurality of laminated bodies B immersed in the group III element liquid L is disposed in the HVPE apparatus 3. For example, as shown in FIG. 7, the container 5 is arranged in an area surrounded by the heater 37 (for example, downstream of the pipe 40 and in the growth area 39). Then, the heaters 36 and 37 are driven to simultaneously heat the plurality of laminated bodies B immersed in the liquid of the group III element from the outside of the container 5. Further, a heat treatment apparatus may be prepared separately from the HVPE apparatus 3 and the laminated body B in the container 5 may be heat-treated.

  Moreover, the container for immersing the laminated body B in the liquid of a group III element is not restricted to what is shown in FIG.9 and FIG.10, You may use the container 6 shown in FIG.

  The container 6 includes a container main body 61 whose upper surface is open, a lid 62 that closes the opening of the container main body 61, and a jig 63 for placing the laminate B in the container main body 61.

  The container 6 is made of a heat resistant material. For example, the container body 61, the lid 62, and the jig 63 are made of graphite.

  The jig 63 includes a plurality of holding portions 631 formed by separating a plurality of grooves along the longitudinal direction, and a fixing portion 632 that integrally fixes the end portions of the holding portions 631 in the longitudinal direction. .

  For example, the laminated body B is held by the jig 63 by fitting the outer peripheral edge of the laminated body B into the grooves of the plurality of holding portions 631.

  With the jig 63, the plurality of laminated bodies B are installed at a predetermined interval. And the jig | tool 63 holding the some laminated body B is inserted in the container main body 61. FIG. Thereafter, the container main body 61 is filled with the group III element liquid, and the plurality of laminated bodies B are completely immersed in the group III element liquid.

  Thereafter, the opening of the container body 61 is closed with the lid 62. Next, the container 6 is placed in the HVPE apparatus 3. For example, the container 6 is arranged in a region surrounded by the heater 37 (for example, downstream of the pipe 40 and in the growth region 39). The heaters 36 and 37 are driven to simultaneously heat the plurality of laminated bodies B immersed in the liquid of the group III element from the outside of the container 6. Further, a heat treatment apparatus may be prepared separately from the HVPE apparatus 3 and the laminated body B in the container 6 may be heat-treated.

  In the heat treatment step, it is preferable to arrange the containers 5 and 6 in a non-oxidizing gas atmosphere such as nitrogen gas in order to suppress corrosion of the containers 5 and 6. Further, the containers 5 and 6 are filled with the liquid of the group III element, but the powder of the group III element that becomes liquid at the heat treatment temperature of the laminate B may be filled.

  The heat treatment is not limited to those exemplified above, and other forms can also be adopted.

  In addition, it is preferable to heat-process a laminated body in non-oxidizing gas. For example, nitrogen gas may be supplied from the nitrogen source gas supply unit 34, or non-oxidizing gas may be supplied from the pipe 40 to make the growth region 39 a non-oxidizing gas atmosphere.

As the non-oxidizing gas, at least one kind can be selected from any of rare gases such as Ar gas and N ₂ gas. By performing the heat treatment in a non-oxidizing gas atmosphere, oxidation of the group III nitride semiconductor layer 16 can be suppressed.

Among them, the non-oxidizing gas, it is preferable to use N ₂ gas. Since nitrogen has a lower nitriding power than ammonia, the use of N ₂ gas can suppress the desorption of N atoms on the surface of the group III nitride semiconductor layer 15 to a certain extent, while the group III nitride is moderately moderated. Can occur, and group III atoms can be generated. The generated group III atoms cause decomposition and degradation of the XC layer, and can promote the separation between the sapphire substrate 10 and the group III nitride semiconductor layer 14.

  Next, an example in which the growth process and the separation process are realized by the same process will be described. In this example, the growth rate of the group III nitride semiconductor layer 14 is optimized, and the group III nitride semiconductor layer 14 is grown at a general growth temperature. Then, during the formation of the group III nitride semiconductor layer 14, decomposition and deterioration of the XC layer are promoted by heating during growth, and the sapphire substrate 10 and the group III nitride semiconductor layer 14 are separated.

  In addition, after separating from the sapphire substrate 10, the structure on the side including the group III nitride semiconductor layer 14 may be washed with an acid (for example, hydrochloric acid aqueous solution). Further, other layers except the group III nitride semiconductor layer 14 may be removed by polishing or the like. In the present embodiment, the structure including the group III nitride semiconductor layer 14 thus obtained can be used as the group III nitride semiconductor substrate of the present embodiment.

  In the present embodiment, the following post-process may be further performed on the self-supporting substrate made of the group III nitride semiconductor layer 14 obtained through the steps up to here.

<Post process>
In this step, the growth surface of the group III nitride semiconductor layer 14 is etched with a mixed solution of phosphoric acid and sulfuric acid at 100 ° C. to 300 ° C. for 0.5 hours to 3 hours. The ratio of phosphoric acid to sulfuric acid (phosphoric acid: sulfuric acid) is 2: 1 to 1:10. For example, a mixed solution of phosphoric acid and sulfuric acid is put in a predetermined container (eg, quartz beaker) and heated to a predetermined temperature with a heating device such as a hot plate. After reaching a predetermined temperature, the group III nitride semiconductor layer 14 is immersed in the container and held for a predetermined time. Thereafter, the group III nitride semiconductor layer 14 is taken out of the container and naturally cooled to prevent cracks due to rapid cooling. After cooling, the acid is washed off with ultrapure water and the process is completed.

  As described above, in the method for manufacturing a group III nitride semiconductor substrate according to the present embodiment, a group III nitride semiconductor layer is formed on a heterogeneous substrate such as a sapphire substrate with an XC layer interposed therebetween, and then the lamination is performed under predetermined conditions. The present invention relates to a peeling method (XC layer decomposition peeling) in which an XC layer is decomposed and deteriorated by heating a body, and a heterogeneous substrate and a group III nitride semiconductor layer are separated from each other at the decomposition deterioration portion.

  And the manufacturing method of the group III nitride semiconductor substrate of this embodiment controls the value of 2θ and the half-value width of the XC layer to desired values by forming the XC layer by a characteristic manufacturing method.

  In the method for manufacturing a group III nitride semiconductor substrate of this embodiment, the X films 12-1 and the C films 12-2 are laminated alternately and continuously, and the XC layers 12 are formed by heating them. By controlling the ratio of the thicknesses of the X film 12-1 and the C film 12-2, variation in the 2θ value of the XC layer 12 can be suppressed and controlled within a desired range. For example, when the X film 12-1 is a Ti film, the thickness T1 of the X film 12-1 and the thickness T2 of the C film 12-2 satisfy 2/3 ≦ T1 / T2 ≦ 3/2. By controlling in this way, the value of 2θ of the XC layer (TiC layer) 12 can be controlled to 35.75 ° or more and 35.95 ° or less.

  Further, in the method for manufacturing a group III nitride semiconductor substrate according to this embodiment, the base C film 11 can be formed under the XC layer 12. Then, by controlling the thickness of the base C film 11, the half width of the XC layer 12 can be controlled. For example, when the XC layer 12 is a TiC layer, the full width at half maximum of the XC layer (TiC layer) 12 is controlled to 6000 sec to 10000 sec by controlling the thickness of the base C film 11 to 1.1 nm to 1.3 nm. Can be controlled.

  In addition, in the method for manufacturing a group III nitride semiconductor substrate of this embodiment, the reactive sputtered XC layer 13 can be formed on the XC layer 12. The reactive sputtered XC layer 13 inherits the crystallinity of the XC layer 12. That is, when the reactive sputter XC layer 13 is formed on the XC layer 12 in which 2θ and the half width are controlled to a desired state, the reactive sputter XC layer 13 has the same 2θ and half width as the XC layer 12. Show. For this reason, by controlling the 2θ and half-value width of the XC layer 12 as described above, the 2θ and half-value width of the reactive sputtered XC layer 13 can be controlled to desired values. As a result, the 2θ and the half width of the XC layer composed of the XC layer 12 and the reactive sputtered XC layer 13 can be controlled to desired values.

  Further, in the method for manufacturing a group III nitride semiconductor substrate of this embodiment, the half width of the reactive sputtered XC layer 13 can be controlled by controlling the thickness of the reactive sputtered XC layer 13. That is, by controlling the thickness of the reactive sputtered XC layer 13, the half width on the surface side of the XC layer composed of the XC layer 12 and the reactive sputtered XC layer 13 can be controlled.

  Moreover, in the manufacturing method of the group III nitride semiconductor substrate of this embodiment, the base substrate (sapphire substrate 10) is controlled by controlling the thicknesses of the base C film 11, the X film 12-1, and the C film 12-2. The orientation can be inherited by the XC layer 12. Specifically, the thickness of the base C film 11 is 0.2 nm to 1.3 nm, the thickness of the X film 12-1 is 0.2 nm to 1.0 nm, and the thickness of the C film 12-2 is By controlling to 0.2 nm or more and 1.0 nm or less, the orientation of the sapphire substrate 10 can be inherited by the XC layer 12. As a result, for example, the (111) -oriented XC layer 12 can be formed.

  Further, in the method for manufacturing a group III nitride semiconductor substrate of the present embodiment, the value of 2θ of the XC layer 12 can be controlled by controlling the applied power when forming the X film 12-1.

  As described above, according to the method for manufacturing a group III nitride semiconductor substrate of the present embodiment, by controlling various parameters, the 2θ of the XC layer composed of the XC layer 12 and / or the reactive sputtered XC layer 13 can be controlled. The value and the half value width can be controlled to desired values. As described above, in the XC layer decomposition peeling, as shown in FIG. 1, there is a predetermined regularity between the value of 2θ, the half-value width, and the peeling yield. According to the present embodiment in which the 2θ value and the half-value width of the XC layer can be controlled, the separation yield can be improved.

  For example, according to the method of manufacturing a group III nitride semiconductor substrate of the present embodiment, the XC layer forming step is performed by XRD using Cu Kα rays by controlling the above various parameters (111). A TiC layer having a value of 2θ of 35.75 ° or more and 35.95 ° or less and a (111) rocking curve half-value width of 6000 scan or more can be formed. As a result, the separation yield between the sapphire substrate 10 and the group III nitride semiconductor layer 14 can be significantly improved by the regularity of FIG.

<< Example >>
<Control of half width of XC layer>
This shows that the half width of the XC layer formed of the XC layer 12 and / or the reactive sputtered XC layer 13 can be controlled by controlling the thickness of the base C film 11 and / or the reactive sputtered XC layer 13. Specifically, the full width at half maximum in a plurality of samples in which the thickness of the base C film 11 and the thickness of the reactive sputtered XC layer 13 are changed is shown.

  First, a 3-inch φ sapphire substrate 10 having a thickness of 550 μm was prepared. Then, a base C film 11, a TiC layer (XC layer 12), and a reactive sputtered TiC layer (reactive sputtered XC layer 13) were formed on the sapphire substrate 10 under the following conditions. The layer structure is as shown in FIG.

“Deposition conditions of base C film 11”
Film forming method: Sputtering film forming temperature: 800 ° C.
Deposition time: 60 seconds, 72 seconds, 84 seconds (3 patterns)
Pressure: 0.4Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: C
Thickness: 0.9, 1.1, 1.3 nm (three patterns according to the film formation time)

"TiC layer (XC layer 12) formation conditions"
○ Ti film (X film 12-1) film forming conditions Film forming method: Sputtering film forming temperature: 800 ° C.
Deposition time: 12 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: Ti
Thickness: 1.0nm

○ Film formation conditions for C film 12-2 Film formation method: Sputtering film forming temperature: 800 ° C
Deposition time: 60 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: C
Thickness: 0.9nm

Number of pairs of Ti film (X film 12-1) and C film 12-2: 20
TiC layer (XC layer 12) thickness: 20 nm

"Film formation conditions for reactive sputtered TiC layer (reactive sputtered XC layer 13)"
Deposition method: Reactive sputtering Deposition temperature: 800 ° C
Deposition time: 0 minutes, 3.5 minutes, 17.5 minutes (3 patterns)
Pressure: 0.4Pa
Applied power: 300W
Sputtering gas: Ar gas Sputtering gas flow rate: 30.0 sccm
Reactive gas: CH ₄
Reactive gas flow rate: 10.0sccm
Target: Ti
Thickness: 0, 20, 100 nm (three patterns according to the film formation time)

  FIG. 12 shows the film formation time (thickness) of the base C film 11 and the half width of the TiC layer composed of the TiC layer (XC layer 12) and / or the reactive sputtered TiC layer (reactive sputtered XC layer 13). Show the relationship.

  The squares are data of a sample in which a reactive sputtered TiC layer (reactive sputtered XC layer 13) having a thickness of 100 nm is formed, and the triangles are formed of a reactive sputtered TiC layer (reactive sputtered XC layer 13) of 20 nm. It is sample data, and the diamond is data of a sample in which no reactive sputtered TiC layer (reactive sputtered XC layer 13) was formed.

  From the figure, in the sample in which the reactive sputtered TiC layer (reactive sputtered XC layer 13) having a thickness of 100 nm is formed, the film formation time of the base C film 11 is changed to 60 seconds, 72 seconds, and 84 seconds. Yes. From the data in the figure, the half width of the TiC layer composed of the TiC layer (XC layer 12) and / or the reactive sputtered TiC layer (reactive sputtered XC layer 13) increases as the thickness of the base C film 11 increases. It turns out that it becomes big.

  Next, FIG. 13 shows the thickness of the reactive sputtered TiC layer (reactive sputtered XC layer 13) and the TiC composed of the TiC layer (XC layer 12) and / or the reactive sputtered TiC layer (reactive sputtered XC layer 13). The relationship with the half width of a layer is shown.

  The square is the data of the sample in which the base C film 11 is formed with a film formation time of 60 seconds, the triangle is the data of the sample with the base C film 11 formed in a film formation time of 72 seconds, and the diamond is the film formation time of 84 seconds. It is the data of the sample which formed the base C film | membrane 11 by.

  From the figure, in the sample in which the base C film 11 was formed with a deposition time of 84 seconds, the thickness of the reactive sputtered TiC layer (reactive sputtered XC layer 13) was changed to 0 nm, 20 nm, and 100 nm. From the data in the figure, as the thickness of the reactive sputtered TiC layer (reactive sputtered XC layer 13) increases, the TiC layer (XC layer 12) and / or the reactive sputtered TiC layer (reactive sputtered XC layer 13). It can be seen that the half-value width of the TiC layer made of is increased.

  As described above, the TiC layer (XC layer 12) and / or the reactive sputtered TiC layer (reactive sputter XC) are controlled by controlling the thickness of the base C film 11 and / or the reactive sputtered TiC layer (reactive sputtered XC layer 13). It can be seen that the full width at half maximum of the TiC layer comprising the layer 13) can be controlled.

  Further, from FIG. 13, when the base C film 11 having a thickness of 1.3 nm or more is formed in a film formation time of 84 seconds or more, a reactive sputtered TiC layer (reactive sputter XC layer having a thickness of 70 nm or more) is formed. It can be seen that by forming 13), the half width of the TiC layer composed of the TiC layer (XC layer 12) and / or the reactive sputtered TiC layer (reactive sputtered XC layer 13) can be controlled to 6000 sec or more.

  Although not shown here, the present inventors have found that the base C film 11 has a thickness even when the reactive sputtered TiC layer (reactive sputtered XC layer 13) has a thickness of less than 70 nm (for example, 0 nm). Confirming that the full width at half maximum of the TiC layer composed of the TiC layer (XC layer 12) and / or the reactive sputtered TiC layer (reactive sputtered XC layer 13) can be controlled to 6000 sec or more by sufficiently increasing the thickness. Yes. Similarly, the inventors have made the reactive sputtered TiC layer (reactive sputtered XC layer 13) sufficiently thick even when the thickness of the base C film 11 is less than 1.1 nm. It has been confirmed that the half width of the TiC layer composed of the TiC layer (XC layer 12) and / or the reactive sputtered TiC layer (reactive sputtered XC layer 13) can be controlled to 6000 sec or more.

<TiC layer orientation>
It shows that the orientation of the sapphire substrate 10 can be inherited by the XC layer 12 by controlling the thicknesses of the base C film 11, the X film 12-1, and the C film 12-2.

  First, a 3-inch φ C-plane sapphire substrate 10 having a thickness of 550 μm was prepared. Then, a base C film 11, a TiC layer (XC layer 12), and a reactive sputtered TiC layer (reactive sputtered XC layer 13) were formed on the sapphire substrate 10 under the following conditions.

“Deposition conditions of base C film 11”
Film forming method: Sputtering film forming temperature: 800 ° C.
Deposition time: 84 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: C
Thickness: 1.3nm

"TiC layer (XC layer 12) formation conditions"
○ Ti film (X film 12-1) film forming conditions Film forming method: Sputtering film forming temperature: 800 ° C.
Deposition time: 12 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: Ti
Thickness: 1.0nm

○ Film formation conditions for C film 12-2 Film formation method: Sputtering film forming temperature: 800 ° C
Deposition time: 60 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: C
Thickness: 0.9nm

Number of pairs of Ti film (X film 12-1) and C film 12-2: 9
TiC layer (XC layer 12) thickness: 10 nm

"Film formation conditions for reactive sputtered TiC layer (reactive sputtered XC layer 13)"
Deposition method: Reactive sputtering Deposition temperature: 800 ° C
Deposition time: 17.5 minutes Pressure: 0.4 Pa
Applied power: 300W
Sputtering gas: Ar
Sputtering gas flow rate: 30sccm
Reactive gas: CH ₄
Reactive gas flow rate: 10.0sccm
Target: Ti
Thickness: 100nm

The resulting TiC layer composed of the TiC layer (XC layer 12) and the reactive sputtered TiC layer (reactive sputtered XC layer 13) was (111) oriented. That is, the orientation of the sapphire substrate 10 was taken over.
<Separation of Sapphire Substrate 10 and Group III Nitride Semiconductor Layer 14>
It shows that the sapphire substrate 10 and the group III nitride semiconductor layer 14 can be peeled by the manufacturing method of the present invention.

  First, a 3-inch φ sapphire substrate 10 having a thickness of 550 μm was prepared. Then, a base C film 11, a TiC layer (XC layer 12), and a reactive sputtered TiC layer (reactive sputtered XC layer 13) were formed on the sapphire substrate 10 under the following conditions.

“Deposition conditions of base C film 11”
Film forming method: Sputtering film forming temperature: 800 ° C.
Deposition time: 84 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: C
Thickness: 1.3nm

"TiC layer (XC layer 12) formation conditions"
○ Ti film (X film 12-1) film forming conditions Film forming method: Sputtering film forming temperature: 800 ° C.
Deposition time: 12 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: Ti
Thickness: 1.0nm

○ Film formation conditions for C film 12-2 Film formation method: Sputtering film forming temperature: 800 ° C
Deposition time: 60 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: C
Thickness: 0.9nm

Number of pairs of Ti film (X film 12-1) and C film 12-2: 9
TiC layer (XC layer 12) thickness: 10 nm

"Film formation conditions for reactive sputtered TiC layer (reactive sputtered XC layer 13)"
Deposition method: Reactive sputtering Deposition temperature: 800 ° C
Deposition time: 17.5 minutes Pressure: 0.4 Pa
Applied power: 300W
Sputtering gas: Ar
Sputtering gas flow rate: 30sccm
Reactive gas: CH ₄
Reactive gas flow rate: 10.0sccm
Target: Ti
Thickness: 100nm

Thereafter, nitriding was performed under the following conditions.
Nitriding temperature: 940 ° C
Nitriding time: 30 minutes Nitriding gas: NH ₃ gas, H ₂ gas

Thereafter, a GaN layer was formed under the following conditions.
Film forming method: HVPE (hydride vapor phase epitaxy) film forming temperature: 1050 ° C.
Deposition time: 150 minutes Thickness: 400 μm

Thereafter, the stacked body after the GaN layer was formed was heated under the following conditions without being cooled to room temperature.
Heating temperature: 1130 ° C
Heating time: 5 hours Heating method: HVPE equipment

  On the upper side (GaN + Sap) of FIG. 14, a planar image of the stacked body in a state where the GaN layers are stacked is shown. 14 shows a planar image of the sapphire substrate immediately after the GaN layer is peeled off by heat treatment. From the figure, it can be seen that the GaN layer is peeled off cleanly without the GaN layer remaining on the sapphire substrate side.

<Control of 2θ value of XC layer>
It shows that the value of 2θ of the XC layer 12 can be controlled by controlling the ratio (T1 / T2) of the thickness T1 of the X film 12-1 and the thickness T2 of the C film 12-2. Further, it is shown that the 2θ value of the XC layer 12 can be controlled by controlling the applied power when forming the X film 12-1.

  First, a 3-inch φ sapphire substrate 10 having a thickness of 550 μm was prepared. Then, a base C film 11 and a TiC layer (XC layer 12) were formed on the sapphire substrate 10 under the following nine pattern conditions to obtain nine samples.

☆ Sample 1 (* 150W: 40 pairs)
“Deposition conditions of base C film 11”
Film forming method: Sputtering film forming temperature: 800 ° C.
Deposition time: 84 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: C
Thickness: 1.3nm

"TiC layer (XC layer 12) formation conditions"
○ Ti film (X film 12-1) film forming conditions Film forming method: Sputtering film forming temperature: 800 ° C.
Deposition time: 12 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: Ti
Thickness: 1.0nm

○ Film formation conditions for C film 12-2 Film formation method: Sputtering film forming temperature: 800 ° C
Deposition time: 60 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: C
Thickness: 0.9nm

Thickness ratio (Ti / C) of Ti film (X film 12-1) and C film 12-2: 1.11
Number of pairs of Ti film (X film 12-1) and C film 12-2: 40
TiC layer (XC layer 12) thickness: 51 nm

☆ Sample 2 (* 150W: 80 pairs)
The conditions are the same as those of Sample 1 except for the following conditions.
Number of pairs of Ti film (X film 12-1) and C film 12-2: 80
TiC layer (XC layer 12) thickness: 101 nm

☆ Sample 3 (* 150W: 120 pairs)
The conditions are the same as those of Sample 1 except for the following conditions.
Number of pairs of Ti film (X film 12-1) and C film 12-2: 120
TiC layer (XC layer 12) thickness: 151 nm

☆ Sample 4 (* 120W: 40 pairs)
“Deposition conditions of base C film 11”
Film forming method: Sputtering film forming temperature: 800 ° C.
Deposition time: 60 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: C
Thickness: 0.9nm

"TiC layer (XC layer 12) formation conditions"
○ Ti film (X film 12-1) film forming conditions Film forming method: Sputtering film forming temperature: 800 ° C.
Deposition time: 12 seconds Pressure: 0.4 Pa
Applied power: 120W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: Ti
Thickness: 0.8nm

○ Film formation conditions for C film 12-2 Film formation method: Sputtering film forming temperature: 800 ° C
Deposition time: 60 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: C
Thickness: 0.9nm

Thickness ratio of Ti film (X film 12-1) and C film 12-2 (Ti / C): 0.89
Number of pairs of Ti film (X film 12-1) and C film 12-2: 40
TiC layer (XC layer 12) thickness: 43 nm

☆ Sample 5 (* 120W: 80 pairs)
The conditions are the same as those of Sample 4 except for the following conditions.
Number of pairs of Ti film (X film 12-1) and C film 12-2: 80
TiC layer (XC layer 12) thickness: 87 nm

☆ Sample 6 (* 120W: 120 pairs)
The conditions are the same as those of Sample 4 except for the following conditions.
Number of pairs of Ti film (X film 12-1) and C film 12-2: 120
TiC layer (XC layer 12) thickness: 129 nm

☆ Sample 7 (* 80W: 40 pairs)
“Deposition conditions of base C film 11”
Film forming method: Sputtering film forming temperature: 800 ° C.
Deposition time: 60 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: C
Thickness: 0.9nm

"TiC layer (XC layer 12) formation conditions"
○ Ti film (X film 12-1) film forming conditions Film forming method: Sputtering film forming temperature: 800 ° C.
Deposition time: 12 seconds Pressure: 0.4 Pa
Applied power: 80W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: Ti
Thickness: 0.5nm

○ Film formation conditions for C film 12-2 Film formation method: Sputtering film forming temperature: 800 ° C
Deposition time: 60 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: C
Thickness: 0.9nm

Thickness ratio (Ti / C) of Ti film (X film 12-1) and C film 12-2: 0.56
Number of pairs of Ti film (X film 12-1) and C film 12-2: 40
TiC layer (XC layer 12) thickness: 37 nm

☆ Sample 8 (* 80W: 80 pairs)
The conditions are the same as those of Sample 7 except for the following conditions.
Number of pairs of Ti film (X film 12-1) and C film 12-2: 80
TiC layer (XC layer 12) thickness: 73 nm

☆ Sample 9 (* 80W: 120 pairs)
The conditions are the same as those of Sample 1 except for the following conditions.
Number of pairs of Ti film (X film 12-1) and C film 12-2: 120
TiC layer (XC layer 12) thickness: 113 nm

  FIG. 17 shows the relationship between the ratio of the thickness T1 of the Ti film (X film 12-1) and the thickness T2 of the C film 12-2 (Ti / C ratio in the figure) and 2θ. FIG. 18 shows the relationship between applied power (Ti deposition power in the figure) and 2θ when the Ti film (X film 12-1) is deposited. In FIG. 17, the results of samples 3, 6 and 9 are plotted. In FIG. 18, the results of samples 1 to 9 are plotted. In the figure, 120P, 80P, and 40P mean that the number of pairs of the Ti film (X film 12-1) and the C film 12-2 is 120, 80, and 40, respectively.

  From FIG. 17, when the ratio of the thickness T1 of the Ti film (X film 12-1) and the thickness T2 of the C film 12-2 (T1 / T2) increases, 2θ of the TiC layer increases linearly. I understand that. Further, FIG. 18 shows that 2θ of the TiC layer increases linearly as the applied power when forming the Ti film (X film 12-1) increases. From the above, it can be seen that the value of 2θ of the XC layer 12 can be controlled by controlling the ratio (T1 / T2) of the thickness T1 of the X film 12-1 and the thickness T2 of the C film 12-2. It can also be seen that the value of 2θ of the XC layer 12 can be controlled by controlling the applied power when forming the X film 12-1.

<Control of variation in 2θ of XC layer>
It shows that by controlling the thickness ratio of the X film 12-1 and the C film 12-2, variation in the 2θ value of the XC layer 12 can be suppressed and controlled in a desired range.

  First, a plurality of 3 inch φ sapphire substrates 10 having a thickness of 550 μm were prepared. Then, the plurality of sapphire substrates 10 were arranged at predetermined positions on the tray as shown in FIG. 15, and the base C film 11 and the TiC layer (XC layer 12) were formed under the following conditions.

“Deposition conditions of base C film 11”
Film forming method: Sputtering film forming temperature: 800 ° C.
Deposition time: 84 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: C
Thickness: 1.3nm

"TiC layer (XC layer 12) formation conditions"
○ Ti film (X film 12-1) film forming conditions Film forming method: Sputtering film forming temperature: 800 ° C.
Deposition time: 12 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: Ti
Thickness: 1.0nm

○ Film formation conditions for C film 12-2 Film formation method: Sputtering film forming temperature: 800 ° C
Deposition time: 60 seconds Pressure: 0.4 Pa
Applied power: 150W
Sputtering gas: Ar
Sputtering gas flow rate: 100 sccm
Target: C
Thickness: 0.9nm

Number of pairs of Ti film (X film 12-1) and C film 12-2: 40
TiC layer (XC layer 12) thickness: 40 nm

  Then, as shown in FIG. 15, the value of 2θ was measured using “the origin that is the approximate center on the tray” and “a plurality of positions that are separated from the origin by a predetermined distance in a predetermined direction” as measurement points. . FIG. 16 shows the relationship between the position on the tray and the value of 2θ. FIG. 16 shows that the value of 2θ does not vary and is almost constant regardless of the position on the tray. It can be seen that the variation can be suppressed within 0.008 °.

  So far, the case where the XC layer is a TiC layer has been taken as an example, and various effects have been shown. The present inventors have replaced the TiC layer with an AlC layer, a ZrC layer, an Hf layer, a V layer, or a Ta layer. It has been confirmed that the same results can be obtained even when adopting.

<Second Embodiment>
The present inventors formed a group III nitride semiconductor layer with a XC layer (X is Ti, Al, Zr, Hf, V, or Ta) on a heterogeneous substrate such as a sapphire substrate, and then formed the laminate. A method of separating the sapphire substrate and the group III nitride semiconductor layer by generating a stress based on a difference in thermal expansion coefficient between the sapphire substrate and the group III nitride semiconductor layer by cooling (hereinafter referred to as “cooling”). Invented the “separation”.

  The presence of the XC layer can weaken the bonding force between the sapphire substrate and the group III nitride semiconductor layer. As a result, the sapphire substrate and the group III nitride semiconductor layer can be easily separated using the stress.

  By the way, the present inventors have produced | generated the XC layer by the reactive sputtering until now. However, this method has a problem that the value of 2θ of the XC layer varies. Further, there is a problem in that the separation method varies due to variation in the value of 2θ, resulting in poor yield. Therefore, the present inventors have newly invented cooling separation using a method for generating an XC layer that can control the value of 2θ of the XC layer. The present embodiment relates to the cooling separation and includes a step of forming an XC layer by a characteristic method. Hereinafter, this embodiment will be described in detail.

The manufacturing method of the group III nitride semiconductor substrate (free-standing substrate) of the present embodiment is as follows:
(1) 'a step of forming a base C film on the base substrate (base C film forming step);
(2) ′ a step of forming an XC layer on the base C film (XC layer forming step);
(3) ′ a step of nitriding at least a part of the XC layer (nitriding step);
(4) Step of separating the base substrate and the group III nitride semiconductor layer by forming a group III nitride semiconductor layer on the nitrided XC layer and then cooling (growth step and separation step) )When,
Have

  The outline of the (1) ′ base C film forming step is the same as the (1) base C film forming step described in the first embodiment. However, in the (1) base C film forming step, the thickness of the base C film 11 is controlled to be, for example, 1.1 nm to 1.3 nm, but in the (1) ′ base C film forming step, the base C film 11 The thickness is controlled to, for example, 1.3 nm or more and 1.5 nm or less. By controlling in this way, the half width of the XC layer can be increased. If the full width at half maximum is too small, the crystallinity of the XC layer is improved and peeling is difficult to occur. By controlling the thickness of the base C film 11 as described above and controlling the crystallinity of the XC layer to an appropriate state, peeling can easily occur. Here, an example is shown in which the half width of the XC layer is controlled by controlling the thickness of the base C film 11, but according to the first embodiment, the X film 12-1 and the C film 12-2 are controlled. The half width of the XC layer may be controlled by controlling the thickness ratio and the thickness of the reactive sputtered XC layer 13.

  The outline of the (2) ′ XC layer forming step is the same as the (2) XC layer forming step described in the first embodiment. (2) In the 'XC layer forming step, the value of 2θ of the XC layer is controlled by the same method as in (2) XC layer forming step to suppress the variation.

(3) The outline of the nitriding step is the same as the (3) nitriding step described in the first embodiment. In this step, the flow rate (partial pressure) of NH ₃ gas (nitriding gas) may be controlled so that separation between the sapphire substrate and the group III nitride semiconductor layer is likely to occur. When the flow rate of the NH ₃ gas is small, the sapphire substrate and the group III nitride semiconductor layer are easily separated by cooling after the group III nitride semiconductor layer is formed. For example, the flow rate of NH ₃ gas may be controlled to 3 L / min or more and 5 L / min or less.

  (4) The growth process and the separation process are performed separately in the growth process and the separation process. The growth process is the same as the growth process described in the first embodiment. Note that the thickness relationship between the sapphire substrate and the group III nitride semiconductor layer may be controlled so that the sapphire substrate and the group III nitride semiconductor layer are easily separated. For example, the thickness of the sapphire substrate may be 600 μm or more and 1500 μm or less, and the thickness of the group III nitride semiconductor layer may be 500 μm or more and 2000 μm or less.

  In the separation step performed after the growth step, the stacked body including the sapphire substrate and the group III nitride semiconductor layer is cooled to room temperature. Then, during this cooling, the stacked body is distorted due to the difference in thermal expansion coefficient between the sapphire substrate and the group III nitride semiconductor layer, and the sapphire substrate and the group III nitride semiconductor layer are separated. At this time, the bonding force between the sapphire substrate and the group III nitride semiconductor layer is weakened by the XC layer, and separation easily occurs.

  In the case of this embodiment, variation in the 2θ value of the XC layer can be suppressed. As a result, it is possible to suppress the inconvenience that the method of separating the sapphire substrate and the group III nitride semiconductor layer varies and to increase the yield.

Hereinafter, examples of the reference form will be added.
1. X films (X is Ti, Al, Zr, Hf, V, or Ta) and C films are alternately and continuously stacked, and an XC layer obtained by heating is formed on a base substrate. An XC layer forming step;
A growth step of forming a group III nitride semiconductor layer on the XC layer;
A separation step of separating the base substrate and the group III nitride semiconductor layer;
A method for producing a group III nitride semiconductor substrate having:
2. In the method for producing a group III nitride semiconductor substrate according to 1,
In the XC layer forming step, the thickness T1 of the X film and the thickness T2 of the C film are controlled so as to satisfy 2/3 ≦ T1 / T2 ≦ 3/2. Production method.
3. In the method for producing a group III nitride semiconductor substrate according to 1 or 2,
In the XC layer forming step,
A group III nitride semiconductor substrate in which the thickness T1 of the X film is controlled to satisfy T1 ≦ 1.0 nm and the thickness T2 of the C film is controlled to satisfy T2 ≦ 1.0 nm. Production method.
4). In the method for producing a group III nitride semiconductor substrate according to any one of 1 to 3,
In the XC layer forming step, a Group III nitride semiconductor substrate manufacturing method of forming the XC layer having a thickness of 5 nm or more and 200 nm or less.
5. In the method for producing a group III nitride semiconductor substrate according to any one of 1 to 3,
A reactive sputtering step of forming a reactive sputtered XC layer by reactive sputtering on the XC layer after the XC layer forming step and before the growth step;
The method of manufacturing a group III nitride semiconductor substrate, wherein the thickness T4 of the XC layer and the thickness T5 of the reactive sputtered XC layer satisfy 40 nm ≦ (T4 + T5) ≦ 200 nm.
6). In the method for producing a group III nitride semiconductor substrate according to 5,
In the reactive sputtering step, a Group III nitride semiconductor substrate manufacturing method for forming the reactive sputtered XC layer satisfying T5 ≧ 70 nm.
7). In the method for producing a group III nitride semiconductor substrate according to any one of 1 to 6,
Before the XC layer forming step, further comprising a base C film forming step of forming on the base substrate a base C film controlled to a predetermined thickness thicker than the C film;
In the XC layer forming step, the group III nitride semiconductor substrate is formed by forming the XC layer on the base C film.
8). In the method for producing a group III nitride semiconductor substrate according to 7,
In the base C film forming step, a Group III nitride semiconductor substrate manufacturing method of forming the base C film having a thickness of 1.1 nm or more and 1.3 nm or less.
9. In the method for producing a group III nitride semiconductor substrate according to any one of 1 to 8,
In the XC layer forming step, the value of 2θ of TiC (111) measured by XRD (x-ray diffraction) using CuKα rays is 35.75 ° or more and 35.95 ° or less, and TiC by ω scan is used. (111) A method for producing a group III nitride semiconductor substrate, wherein a TiC layer having a half-value width of a rocking curve of 6000 sec or more is formed.

3 HVPE device 5 Container 6 Container 10 Sapphire substrate (underlying substrate)
11 Base C film 12 XC layer 12-1 X film 12-2 C film 13 Reactive sputtered XC layer 14 Group III nitride semiconductor layer 31 Reaction tube 32 Substrate holder 33 Group III source gas supply unit 34 Nitrogen source gas supply unit 35 Gas exhaust pipes 36, 37 Heater 38 Shield plate 39 Growth region 40 Piping 41 Rotating shaft 50 Container body 51 Side wall 52 Pin 52A-52D Pin 53 Lid 55 Jig 61 Container main body 62 Lid 63 Jig 141 Titanium nitride layer 142 Titanium carbide layer 143 Nitrided cap layer 311 Gas supply pipe 312 Source boat 313 Group III raw material 341 Gas supply pipe 511 Recess 631 Holding part 632 Fixing part A Laminated body B Laminated body L Liquid

Claims (9)

X films (X is Ti, Al, Zr, Hf, V, or Ta) and C films are alternately and continuously stacked, and an XC layer obtained by heating is formed on a base substrate. An XC layer forming step;
A growth step of forming a group III nitride semiconductor layer on the XC layer;
A separation step of separating the base substrate and the group III nitride semiconductor layer;
A method for producing a group III nitride semiconductor substrate having: In the manufacturing method of the group III nitride semiconductor substrate according to claim 1,
In the XC layer forming step, the thickness T1 of the X film and the thickness T2 of the C film are controlled so as to satisfy 2/3 ≦ T1 / T2 ≦ 3/2. Production method. In the manufacturing method of the group III nitride semiconductor substrate according to claim 1 or 2,
In the XC layer forming step,
A group III nitride semiconductor substrate in which the thickness T1 of the X film is controlled to satisfy T1 ≦ 1.0 nm and the thickness T2 of the C film is controlled to satisfy T2 ≦ 1.0 nm. Production method. In the manufacturing method of the group III nitride semiconductor substrate of any one of Claim 1 to 3,
In the XC layer forming step, a Group III nitride semiconductor substrate manufacturing method of forming the XC layer having a thickness of 5 nm or more and 200 nm or less. In the manufacturing method of the group III nitride semiconductor substrate of any one of Claim 1 to 3,
A reactive sputtering step of forming a reactive sputtered XC layer by reactive sputtering on the XC layer after the XC layer forming step and before the growth step;
The method of manufacturing a group III nitride semiconductor substrate, wherein the thickness T4 of the XC layer and the thickness T5 of the reactive sputtered XC layer satisfy 40 nm ≦ (T4 + T5) ≦ 200 nm. In the manufacturing method of the group III nitride semiconductor substrate according to claim 5,
In the reactive sputtering step, a Group III nitride semiconductor substrate manufacturing method for forming the reactive sputtered XC layer satisfying T5 ≧ 70 nm. In the manufacturing method of the group III nitride semiconductor substrate of any one of Claim 1 to 6,
Before the XC layer forming step, further comprising a base C film forming step of forming on the base substrate a base C film controlled to a predetermined thickness thicker than the C film;
In the XC layer forming step, the group III nitride semiconductor substrate is formed by forming the XC layer on the base C film. In the manufacturing method of the group III nitride semiconductor substrate according to claim 7,
In the base C film forming step, a Group III nitride semiconductor substrate manufacturing method of forming the base C film having a thickness of 1.1 nm or more and 1.3 nm or less. In the manufacturing method of the group III nitride semiconductor substrate of any one of Claim 1 to 8,
In the XC layer forming step, the value of 2θ of TiC (111) measured by XRD (x-ray diffraction) using CuKα rays is 35.75 ° or more and 35.95 ° or less, and TiC by ω scan is used. (111) A method for producing a group III nitride semiconductor substrate, wherein a TiC layer having a half-value width of a rocking curve of 6000 sec or more is formed.