JP6091969B2 - Manufacturing method of base substrate and manufacturing method of group III nitride semiconductor substrate - Google Patents

Description

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

  In recent years, it has been studied to use a group III nitride semiconductor substrate such as GaN as a substrate for a nitride-based optical device or an electronic device. As a method of manufacturing this group III nitride semiconductor substrate, after forming a group III nitride layer having a predetermined thickness or more to be a group III nitride semiconductor substrate on a different type substrate such as a sapphire substrate, the different type substrate is formed. Removal is performed (for example, refer to Patent Documents 1 and 2).

JP 2003-55097 A JP 2008-120670 A

  When a group III nitride layer having a thickness that becomes a group III nitride semiconductor substrate is grown on a different type substrate, the stress caused by the difference in linear expansion coefficient between the different type substrate and the group III nitride layer is III. It will be applied to the group nitride layer. This stress can be used to separate the dissimilar substrate and the group III nitride layer, but the separation position or shape of the dissimilar substrate and the group III nitride layer is likely to vary. There is a concern that the productivity of the group III nitride semiconductor substrate is lowered due to this variation.

Therefore, the present inventors examined the production of a group III nitride semiconductor base substrate, and formed a group III nitride semiconductor layer on the base layer, thereby improving the productivity of the group III nitride semiconductor substrate. We thought that we could improve.
Then, various studies were made on a method for manufacturing a base substrate of a group III nitride semiconductor, and the following manufacturing method was proposed.
That is, according to the present invention,
Forming a carbide layer selected from aluminum carbide, titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide and tantalum carbide on the base material layer;
Nitriding the carbide layer;
Epitaxially growing a group III nitride semiconductor layer on the nitrided carbide layer;
A laminate comprising the base material layer, the carbide layer, and the group III nitride semiconductor layer is heat-treated in a state of being immersed in a liquid of a group III element, and the base material layer is removed from the group III nitride semiconductor layer. Peeling and obtaining a base substrate of a group III nitride semiconductor including the group III nitride semiconductor layer; and
Including
In the heat treatment, there is provided a method for manufacturing a base substrate in which the stacked body of the base material layer, the carbide layer, and the group III nitride semiconductor layer is heat-treated at a temperature higher than a growth temperature of the epitaxial growth .

In such a method, when the base material layer and the group III nitride semiconductor layer are peeled off, the base material layer does not greatly depend on the stress due to the difference in linear expansion coefficient between the base material layer and the group III nitride semiconductor layer. It was found that the layer and the group III nitride semiconductor layer can be peeled off. Thereby, a base substrate can be obtained with high productivity.
If the same group III nitride semiconductor layer is formed on such a base substrate, the group III nitride semiconductor substrate can be obtained with high productivity.

That is, according to the present invention, there is provided a method for manufacturing a group III nitride semiconductor substrate including the above-described method for manufacturing a base substrate,
According to the method for manufacturing a base substrate, there is provided a method for manufacturing a group III nitride semiconductor substrate including a step of further growing a group III nitride semiconductor layer on the manufactured base substrate.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the base substrate which can improve the productivity of a group III nitride semiconductor substrate, and the manufacturing method of the group III nitride semiconductor substrate using this manufacturing method are provided.

(A)-(c) is process sectional drawing which shows the manufacturing process of the base substrate concerning one Embodiment of this invention, and is sectional drawing along the thickness direction of the base material layer. It is the schematic of an HVPE apparatus. It is sectional drawing which shows the state at the time of heat processing. It is a figure which shows the container used for heat processing. It is a figure which shows the container used for heat processing. (A)-(c) is process sectional drawing which shows the manufacturing process of a base substrate, and is sectional drawing along the thickness direction of the base material layer. (A) And (b) is process sectional drawing which shows the manufacturing process of a semiconductor substrate, and is sectional drawing along the thickness direction of a base substrate. It is a figure which shows the modification of the manufacturing process of a semiconductor substrate, and is sectional drawing along the thickness direction of a base substrate.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same components are denoted by the same reference numerals, and detailed description thereof is appropriately omitted so as not to overlap.
(Manufacturing process of base substrate)
First, an outline of the manufacturing process of the base substrate according to the present embodiment will be described with reference to FIGS.
The manufacturing method of the base substrate 10 of this embodiment is as follows:
Forming a carbide layer 12 selected from aluminum carbide, titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide and tantalum carbide on the base material layer 11;
Nitriding the carbide layer 12;
Epitaxially growing a group III nitride semiconductor layer 15 on the nitrided carbide layer 12;
A laminate composed of the base material layer 11, the nitrided carbide layer 12, and the group III nitride semiconductor layer 15 is heat-treated while being immersed in a liquid of a group III element, and the group III nitride semiconductor layer 15 forms the base Peeling the material layer 11 to obtain a group III nitride semiconductor base substrate 10 including the group III nitride semiconductor layer 15.

Next, with reference to FIGS. 1-6, the manufacturing process of the base substrate 10 of this embodiment is demonstrated in detail.
First, the base material layer 11 is prepared. The base material layer 11 is preferably a different substrate from the base substrate 10. For example, a substrate selected from a sapphire substrate, spinel substrate, SiC substrate, ZnO substrate, silicon substrate, GaAs substrate, GaP substrate and the like is used. Can be used. Among these, a sapphire substrate is preferable from the viewpoint of crystal quality and cost of commercially available products.

(Formation of carbide layer 12)
Next, as shown in FIG. 1A, a carbide layer 12 is formed on the base material layer 11.
The carbide layer 12 can be a layer made of any one or more selected from aluminum carbide, titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, and tantalum carbide. For example, when the carbide layer 12 is any one of an aluminum carbide layer, a titanium carbide layer, a zirconium carbide layer, a hafnium carbide layer, a vanadium carbide layer, and a tantalum carbide layer, an aluminum carbide layer, a titanium carbide layer, a zirconium carbide layer, and a hafnium carbide layer. The layers, vanadium carbide layer, and tantalum carbide layer are mainly composed of Al ₄ C ₃ , TiC, ZrC, HfC, VC, and TaC, respectively.
However, it is preferable that at least one of group III atoms constituting group III nitride semiconductor layer 15 is different from a metal atom constituting carbide layer 12. In the case where the group III nitride semiconductor layer 15 is an In _x Al _y Ga _z N (x + y + z = 1, 0 ≦ x ≦ 1, 0 <y ≦ 1, 0 ≦ z ≦ 1) layer, that is, when Al is included. The carbide layer 12 is preferably a layer of any of titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, and tantalum carbide.

The carbide layer 12 can be formed by metal organic vapor phase epitaxy (MOVPE method) or sputtering.
For example, trimethylaluminum may be used to form an aluminum carbide layer by the MOVPE method. Further, for example, the titanium carbide layer may be formed by reactive sputtering using Ti as the target, Ar gas as the sputtering gas, and methane gas as the reactive gas.
The thickness of the carbide layer 12 is, for example, 20 to 500 nm. When the thickness is 20 nm or more, the crystallinity of the carbide layer 12 can be improved, and when the thickness is 500 nm or less, the carbide layer 12 and the base material layer 11 can be easily separated.

(Nitriding of carbide layer 12)
Next, as shown in FIG. 1B, the carbide layer 12 is nitrided to form a nitrided carbide layer 12 (indicated by reference numeral 120). The nitrided carbide layer 12 has a carbide layer 12A in contact with the base material layer 11 and a nitride layer 13 formed on the carbide layer 12A and taking over the crystal information of the carbide layer 12A.
However, the nitride layer 13 may not completely cover the carbide layer 12A, and a part of the carbide layer 12A may be exposed. Further, as will be described in detail later, depending on the crystallinity of nitride layer 13 and carbide layer 12A, nitride layer 13 may completely cover carbide layer 12A.

For example, the carbide layer 12 can be nitrided under the following conditions.
Nitriding gas: ammonia (NH ₃ ) gas, H ₂ gas, N ₂ gas Nitriding temperature: 300 ° C. to 900 ° C.
Nitriding time: 5 minutes to 60 minutes The nitriding temperature is more preferably 500 ° C. or more and 700 ° C. or less, and particularly preferably 550 ° C. or less.
In this step, the following reaction (1) or (2) occurs on the surface of the carbide layer 12.
Al ₄ C ₃ + 4NH ₃ → 4AlN + 3CH ₄ (1) Formula 2MC + 2NH ₃ + H ₂ → 2MN + 2CH ₄ (2) In Formula (2), M is Ti, Zr, Hf, V, One of Ta.

At this time, by setting the nitriding temperature to 550 ° C. or lower, it is possible to suppress CH _{4 from} being decomposed and C to be precipitated, and C from being mixed into the nitride layer. Thereby, it is possible to prevent the crystallinity of the group III nitride semiconductor layer from being lowered. In order to suppress the precipitation of C, it is effective to increase the introduction of hydrogen and the partial pressure of ammonia.
Note that the carbide layer 12 may be nitrided while the temperature is raised from 300 ° C. to 900 ° C. By doing so, in the nitriding step, the temperature can be brought close to the film forming temperature of the group III nitride semiconductor layer 15 to be described later, and the manufacturing time can be shortened.
The thickness of the nitride layer 13 formed in this step is preferably 50 nm or less.
Thus, the base material layer 11 can be easily peeled by reducing the thickness of the nitride layer 13.

  As a reaction gas when nitriding the carbide layer 12, ammonia is preferable. Nitride can be formed even if nitrogen is used as a reaction gas in addition to ammonia. However, when C is formed and C is mixed into the nitride layer 13, the crystal quality of the group III nitride semiconductor layer may be affected. There is sex.

Here, taking over crystal information from Al ₄ C ₃ to AlN, TiC to TiN, ZrC to ZrN, HfC to HfN, VC to VN, or TaC to TaN, the crystal structures of these carbides and nitrides are the same, and the lattice structure is the same. Very good due to small mismatch. And since the crystal structure of all these compounds belongs to a hexagonal crystal or a face centered cubic crystal, it is suitable for epitaxial growth of a group III nitride semiconductor layer.

(Epitaxial growth of group III nitride semiconductor layer 15)
Next, group III nitride semiconductor layer 15 is epitaxially grown on nitrided carbide layer 12.
In the present embodiment, when the group III nitride semiconductor layer 15 is a GaN semiconductor layer, the growth conditions 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 270 minutes Film thickness: 100 μm to 500 μm
Thereby, as shown in FIG.1 (c), the group III nitride semiconductor layer 15 will be provided.
In addition, after forming the low temperature growth buffer layer of the group III nitride semiconductor at a temperature lower than the film forming temperature, the group III nitride semiconductor may be epitaxially grown under the above growth conditions.
Further, after forming the group III nitride semiconductor facet, the group III nitride semiconductor may be epitaxially grown under the above growth conditions to obtain the group III nitride semiconductor layer 15 which is a flat film.

  Here, the hydride vapor phase epitaxy (HVPE) apparatus 3 will be briefly described with reference to FIG. FIG. 2 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 group III atoms (for example, GaCl) and supplies it to the surface of the nitrided carbide layer 12 on the substrate holder 32. In FIG. 2, a laminate composed of the base material layer 11 and the nitrided carbide layer 12 is denoted by reference symbol A.

  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 source 313 in the source boat 312 in the group III source 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 containing is generated. 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.

In the initial stage of the step of forming group III nitride semiconductor layer 15, the surface of nitrided carbide layer 12 may be further nitrided with a nitrogen source gas.
In the initial stage of forming the group III nitride semiconductor layer 15, it is considered that the carbide exposed on the surface of the nitrided carbide layer 12 reacts with the group III nitride semiconductor as follows. Here, a case where the group III nitride semiconductor is GaN will be described as an example.
Al ₄ C ₃ + 4GaN → 4AlN + 4Ga + 3C (3) Formula MC + GaN → MN + Ga + C (4) In Formula (4), M is Ti, Zr, Hf, V, Ta Either.
Depending on the crystallinity of nitride layer 13 and carbide layer 12A, the following reaction may occur. The group III nitride semiconductor is thermally decomposed into nitrogen atoms and group III atoms. Nitrogen atoms generated by this thermal decomposition are formed on the surface of the carbide layer 12A through gaps (for example, crystal grain boundaries or microcracks) in the nitride layer 13, and in some cases, gaps in the surface layer of the carbide layer 12A (for example, A crystal grain boundary or a microcrack), and a reaction may occur in which the carbide on the surface of the carbide layer 12A and the carbide on the surface layer become nitrides.

As can be understood from the above description, at the initial stage of forming the group III nitride semiconductor layer 15, the thickness of the nitride layer 13 is increased to form the nitride layer 13A (see FIG. 1C). . Further, as can be understood from the above description, the thickness of the carbide layer 12A is reduced to become the carbide layer 12B in the initial stage of the step of forming the group III nitride semiconductor layer 15.
Further, the group III atoms deposited by the reactions (3) and (4) above and the thermal decomposition of the group III nitride semiconductor are located between the group III nitride semiconductor layer 15 and the nitride layer 13A. As a result, the group III element precipitation layer 14 is formed.

  The thickness of group III nitride semiconductor layer 15 is preferably 600 μm or less, for example, from the viewpoint of reducing the stress generated by the difference in linear expansion coefficient between base material layer 11 and group III nitride semiconductor layer 15. 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 15 is preferably 50 μm or more from the viewpoint of handleability.

Next, the supply of the source gas from the group III source gas supply unit 33 and the supply of the gas from the nitrogen source gas supply unit 34 are stopped, and the growth of the group III nitride semiconductor is stopped. Heating by the heaters 36 and 37 of the HVPE apparatus 3 is stopped, and the laminate B composed of the base material layer 11, the carbide layer 12B, the nitride layer 13A, the group III element precipitation layer 14 and the group III nitride semiconductor layer 15 is heated to room temperature ( For example, after cooling to 25 ° C., it is taken out from the HVPE apparatus 3. In this cooling process, the base material layer 11 and the group III nitride semiconductor layer 15 are not peeled off.
And the above process is repeated and the some laminated body B is prepared.

(Peeling process)
Next, the plurality of stacked bodies B are heated and heat-treated. In this heat treatment step, the laminate B is heat-treated in a state where the laminate B is 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 15. For example, when the group III nitride semiconductor layer 15 is GaN, the group III element liquid is a Ga liquid.
The group III element liquid may be any liquid that becomes liquid at the heat treatment temperature of the laminate B at least. For example, even if it is solid at 25 ° C., it may be liquid at the heat treatment temperature of the laminate B. 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 shown in FIGS. 3 and 4 is prepared. FIG. 3 is a cross-sectional view orthogonal to the bottom surface of the container 5. FIG. 4 is a perspective view of the container 5 and is a view showing the laminated body B arranged inside. In FIG. 3, for the sake of clarity, the carbide layer 12 </ b> B, the nitride layer 13 </ b> A, the group III element precipitation layer 14, and the group III nitride semiconductor layer 15 of the stacked body B are shown as a single layer. Yes.

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 base material layer 11 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 base material layer 11 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 base material layer 11 of the second laminate B is pressed with the pin 52B.
Such an operation is repeated, and the outer peripheral edge of the base material layer 11 of each laminate 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. 3, the container 5 is disposed 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 III group element is not restricted to what is shown in FIG.3, 4, 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 5 is arranged in an area surrounded by the heater 37 (for example, downstream of the pipe 40 and in the growth area 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.

In the heat treatment step, the base material layer 11 is peeled from the group III nitride semiconductor layer 15. In the heat treatment process, the group III nitride semiconductor layer 15 and the base material layer 11 are peeled off without physically applying an external force to the laminate B.
In the present embodiment, since the plurality of stacked bodies B are simultaneously heated, the group III nitride semiconductor layer 15 and the base material layer 11 of the plurality of stacked bodies B can be peeled in one heat treatment step.
It can be estimated from the following points that the group III nitride semiconductor layer 15 and the base material layer 11 are peeled off during the heat treatment process.
When the adhesion between the group III nitride semiconductor layer 15 and the base material layer 11 is not sufficiently reduced during the heat treatment, a portion with a strong adhesion between the group III nitride semiconductor layer 15 and the base material layer 11 A weak part will be mixed. In the cooling step, it is considered that the stress distribution generated due to the difference in linear expansion coefficient between the group III nitride semiconductor layer 15 and the base material layer 11 becomes non-uniform and induces cracking of the group III nitride semiconductor layer 15. It is done. On the other hand, in the present embodiment, since the group III nitride semiconductor layer 15 after the cooling step described later does not crack, in the heat treatment step before entering the cooling step, the group III nitride semiconductor layer 15; It is considered that the adhesion force between the base material layer 11 is reduced and the adhesion force is almost lost, and the group III nitride semiconductor layer 15 and the base material layer 11 are separated in the heat treatment step.

Although the mechanism by which the group III nitride semiconductor layer 15 and the base material layer 11 are peeled off is not clear, it is presumed as follows.
Group III atoms are present in the group III element precipitation layer 14 described above. Furthermore, the group III nitride constituting the group III nitride semiconductor layer 15 is decomposed by the heat treatment, and group III atoms are formed.
Since Group III atoms have a low melting point, they become liquid during the heat treatment process. Then, as shown in FIG. 6A, the group III atoms pass through the nitride layer 13A and reach the carbide layer 12B. The arrows in FIG. 6A indicate how the group III atoms pass through the nitride layer 13A.
And it is thought that the following reactions occur in carbide layer 12B. Here, an example in which the group III nitride semiconductor is Ga will be described.
Al ₄ C ₃ + 4Ga (l) → 4Al-Ga (l) + 3C (5) Formula MC + Ga (l) → M-Ga (l) + C (6) In Formula (6) , M is any one of Ti, Zr, Hf, V, and Ta.
From the viewpoint of advancing the reaction of the formulas (5) and (6), the group III atoms constituting the group III nitride semiconductor layer 15 and the metal atoms constituting the carbide layer 12B are preferably different. .

  Thereby, the crystal structure of the carbide of the carbide layer 12B is destroyed, and the adhesion between the carbide layer 12B and the base material layer 11 is deteriorated. Then, the group III nitride semiconductor layer 15 and the base material layer 11 are separated (see FIG. 6B). The location where peeling between group III nitride semiconductor layer 15 and base material layer 11 is not particularly limited, but peeling occurs at the interface between carbide layer 12B and base material layer 11, and group III nitride semiconductor layer 15 and base layer 11 are separated from each other. In many cases, separation from the material layer 11 occurs, or cracks are generated in the carbide layer 12B, so that the carbide layer 12B is separated into two, and the group III nitride semiconductor layer 15 and the base material layer 11 are separated. .

The heat treatment temperature is preferably higher than the epitaxial growth temperature of the group III nitride semiconductor layer 15. By performing the heat treatment at a temperature higher than the growth temperature of the group III nitride semiconductor layer 15, the reactions of the formulas (5) and (6) can easily proceed, and the group III nitride semiconductor layer 15 and the base material layer 11 can be combined. Can peel. Especially, it is preferable that it is 1100 degreeC or more and 1300 degrees C or less. Furthermore, it is preferable that it is 1150 degreeC or more and 1250 degrees C or less. By performing the heat treatment at 1100 ° C. or higher, the Ga permeation rate is moderately increased, and the base material layer 11 can be smoothly peeled off from the group III nitride semiconductor layer 15 during the heat treatment without applying external force. By setting the temperature to 1300 ° C. or lower, excessive decomposition of the group III nitride semiconductor layer 15 can be suppressed.
In addition, since the liquid of a group III element has favorable heat conductivity, it is thought that the temperature of the laminated body B is 1100 degreeC or more and 1300 degrees C or less.
Moreover, it is preferable that the time (heat processing time) heated at the heat processing temperature mentioned above is 5 to 15 hours, for example, and it is preferable that it is 6 to 10 hours especially.

Thus, in the present embodiment, it is considered that the group III nitride semiconductor layer 15 and the base material layer 11 are peeled off by the mechanism described above during the heat treatment. The base material layer 11 and the group III nitride semiconductor layer 15 can be peeled off almost independently of the stress due to the difference in linear expansion coefficient between the base material layer 11 and the group III nitride semiconductor layer 15. Therefore, a large variation in the peeled shape between the base material layer 11 and the group III nitride semiconductor layer 15 hardly occurs, and the desired base substrate 10 can be obtained with high productivity.
Moreover, since the group III nitride semiconductor layer 15 and the base material layer 11 are separated by the mechanism described above, the base material layer 11 and the group III nitride semiconductor layer 15 formed on the base material layer 11 have a large diameter. Even in this case, a large variation is hardly generated in the peeled shape between the base material layer 11 and the group III nitride semiconductor layer 15, and the desired base substrate 10 can be obtained with high productivity.
For example, the diameter of the base material layer 11 and the group III nitride semiconductor layer 15 (corresponding to the diameter of the base substrate 10) can be 10 mm or more and 200 mm or less.

  Here, in the heat treatment step, when the stacked body B is not immersed in the liquid of the group III element, the surface of the group III nitride semiconductor layer 15 may be decomposed. At this time, Group III element droplets generated by thermal decomposition adhere to the surface of the Group III nitride semiconductor layer 15. When the layered product B is not immersed in the group III element liquid during the heat treatment, the portion of the surface of the group III nitride semiconductor layer 15 covered with the group III element droplets is the group III nitride. Although the decomposition of the semiconductor layer 15 is suppressed, the decomposition of the group III nitride semiconductor layer 15 proceeds in the portion not covered with the group III element droplets, and the thickness of the group III nitride semiconductor layer 15 is increased. Will decrease. On the other hand, as in this embodiment, by immersing the stacked body B in the liquid of the group III element, the decomposition of the group III nitride semiconductor layer 15 can be suppressed, and the film thickness is reduced. Nonuniformity is less likely to occur, and in-plane film thickness variation can be suppressed. In addition, since the decrease in the thickness of the group III nitride semiconductor layer 15 can be suppressed, the base substrate 10 having a relatively large thickness can be obtained.

  Furthermore, the liquid of the group III element has good heat conduction, and the in-plane temperature distribution of the laminate B can be made uniform by immersing the laminate B in such a liquid. Thereby, the reaction that contributes to the peeling of the above-described formulas (5) and (6) can be uniformly generated in the plane of the laminate B, and even in the laminate B having a relatively large diameter, the group III nitride The group III nitride semiconductor layer 15 and the base material layer 11 can be peeled without causing cracks in the semiconductor layer 15.

Next, heating by the heaters 36 and 37 of the HVPE apparatus 3 is stopped, and the stacked body B in which the base material layer 11 and the group III nitride semiconductor layer 15 are separated is cooled. Then, the stacked body B in which the base material layer 11 and the group III nitride semiconductor layer 15 are separated in a state where the liquid of the group III element in the container 5 or the container 6 is in a liquid state is taken out from the HVPE apparatus 3. .
For example, the container 5 or the container 6 may be heated by a heating means such as a hot plate so that the liquid of the group III element does not solidify.
Note that group III atoms from the group III element precipitation layer 14 reach the carbide layer 12B and cause separation, so that the separation interface between the group III nitride semiconductor layer 15 and the base material layer 11, for example, group III nitride A group III atom droplet from the group III element deposition layer 14 adheres to the surface of the structure on the side including the physical semiconductor layer 15. Moreover, since the laminated body B is immersed in the liquid of a group III element, the liquid of a group III element will also adhere. Therefore, a liquid or solid group III group element is formed at the separation interface between the group III nitride semiconductor layer 15 and the base material layer 11.
Note that the group III nitride semiconductor layer 15 and the base material layer 11 that have been peeled off may be taken out of the container 5 or the container 6 in a state where the liquid of the group III element in the container 5 or the container 6 is solidified. A solidified layer of the group III element adheres to the separation interface between the group III nitride semiconductor layer 15 and the base material layer 11.

Thereafter, the structure on the side including the group III nitride semiconductor layer 15 cooled to room temperature (for example, 25 ° C.) is washed with an acid (for example, an aqueous hydrochloric acid solution or a mixed solution of phosphoric acid and sulfuric acid). Remove layer of group element. In this step, not only the group III element layer existing at the separation interface between the group III nitride semiconductor layer 15 and the base material layer 11 but also the carbide layer 12B, the nitride layer 13A, and the group III element precipitation. Layer 14 may also be etched.
Furthermore, if necessary, the structure may be polished to remove the carbide layer 12B, the nitride layer 13A, and the group III element precipitation layer 14. Then, as shown in FIG. 6C, a single crystal base substrate 10 made of a group III nitride semiconductor layer 15 is obtained. This base substrate 10 is a self-supporting substrate.

  Here, in the present embodiment, the base material layer 11 and the group III nitride semiconductor layer 15 are peeled off almost independently of the stress due to the difference in linear expansion coefficient between the base material layer 11 and the group III nitride semiconductor layer 15. can do. The base material layer 11 is hardly subjected to stress due to a difference in linear expansion coefficient between the base material layer 11 and the group III nitride semiconductor layer 15. Therefore, the process mentioned above can be implemented again by recycling the base material layer 11. That is, the steps of forming the carbide layer 12 again on the base material layer 11 and nitriding to form the group III nitride semiconductor layer 15 and separating the base material layer 11 and the group III nitride semiconductor layer 15 are performed. can do. Thereby, the production cost of the base substrate 10 can be reduced.

(Semiconductor substrate manufacturing process)
Next, as shown in FIGS. 7A and 7B, a thick film growth of the group III nitride semiconductor layer 21 is performed using the base substrate 10 to manufacture the semiconductor substrate 2.
At this time, the base substrate 10 may be selected in advance. For example, after manufacturing the plurality of base substrates 10, the plurality of base substrates 10 are selected based on the crystal defect density of the base substrate 10, and the group III nitride semiconductor layer 21 is formed on the base substrate 10 having a reference value or more. It may be formed.
In the present embodiment, after the base substrate 10 having a small thickness is formed, the group III nitride semiconductor layer 21 is grown on the base substrate 10 in a thick film. Before the thick film growth of the physical semiconductor layer 21, the base substrate 10 can be sorted and removed in advance. Thereby, the manufacturing cost of the semiconductor substrate can be reduced.

Here, the group III nitride semiconductor layer 21 is preferably at least twice as thick as the underlying substrate 10.
The growth conditions of group III nitride semiconductor layer 21 can be, for example, as follows. The group III nitride semiconductor layer 21 is preferably composed of a group III nitride having the same composition as the base substrate 10.

Film forming method: HVPE (hydride vapor phase epitaxy) film forming temperature: 1000 ° C. to 1050 ° C.
Deposition time: 30 minutes to 270 minutes Film thickness: 500 μm to 900 μm
The group III nitride semiconductor layer 21 can be manufactured using the HVPE apparatus 3 described above.
Thereby, the substrate 2 having the base substrate 10 and the group III nitride semiconductor layer 21 can be obtained.
Here, the group III nitride semiconductor layer 21 is preferably grown from the surface of the base substrate 10 on the side opposite to the surface located on the base material layer 11 side.
As shown in FIG. 8, the substrate 2 may be obtained by growing group III nitride semiconductor layers 21 and 22 from the front and back surfaces of the base substrate 10. Note that the group III nitride semiconductor layer 22 is also preferably made of a group III nitride having the same composition as the underlying substrate 10.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
In the present embodiment, there is one substrate holder 32 in the HVPE apparatus 3, but the present invention is not limited to this, and there may be a plurality of substrate holders 32.
Further, the group III nitride semiconductor and the group III nitride semiconductor layers 21 and 22 of the base substrate 10 (group III nitride semiconductor layer 15) are In _x Al _y Ga _z N (x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1).
Hereinafter, examples of the reference form will be added.
1. Forming a carbide layer selected from aluminum carbide, titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide and tantalum carbide on the base material layer;
Nitriding the carbide layer;
Epitaxially growing a group III nitride semiconductor layer on the nitrided carbide layer;
A laminate comprising the base material layer, the carbide layer, and the group III nitride semiconductor layer is heat-treated in a state of being immersed in a liquid of a group III element, and the base material layer is removed from the group III nitride semiconductor layer. Peeling the substrate to obtain a group III nitride semiconductor substrate including the group III nitride semiconductor layer.
2. In the manufacturing method of the base substrate of 1,
The method for producing a base substrate, wherein the group III element liquid is a group III element liquid constituting the group III nitride semiconductor layer.
3. In the manufacturing method of the base substrate of 1,
A method of manufacturing a base substrate in which the heat treatment is performed on the stacked body of the base material layer, the carbide layer, and the group III nitride semiconductor layer at a temperature higher than a growth temperature of the epitaxial growth.
4). In the manufacturing method of the base substrate in any one of 1 thru | or 3,
A method of manufacturing a base substrate, wherein the base material layer, the carbide layer, and the group III nitride semiconductor layer stack are heated at 1100 ° C. or higher and 1300 ° C. or lower when the heat treatment is performed.
5. In the method for manufacturing a base substrate according to any one of 1 to 4,
When the heat treatment is performed, the laminated body is heat-treated for 5 hours or more in a state of being immersed in the liquid of the group III element, and during the heat treatment, solidification between the group III nitride semiconductor layer and the substrate layer is performed. A method of manufacturing a base substrate that reduces adhesion.
6). In the manufacturing method of the base substrate of 1,
When the heat treatment is performed, the laminate of the base material layer, the carbide layer, and the group III nitride semiconductor layer is immersed in a liquid of a group III element, and the group III nitride semiconductor is subjected to the heat treatment. A method for producing a base substrate in which the base material layer peels from the layer.
7). In the manufacturing method of the base substrate in any one of 1 thru | or 6,
In the step of epitaxially growing a group III nitride semiconductor layer, a method for manufacturing a base substrate, wherein a group III nitride semiconductor layer having a thickness of 600 μm or less is formed.
8). In the manufacturing method of the base substrate in any one of 1 thru | or 7,
When performing the heat treatment,
A method for manufacturing a base substrate, comprising preparing a plurality of the laminates, housing the plurality of laminates in a container, and immersing the plurality of laminates in a Group III element liquid in the container.
9. A method for manufacturing a group III nitride semiconductor substrate including the method for manufacturing a base substrate according to any one of 1 to 8,
A method of manufacturing a group III nitride semiconductor substrate, further comprising a step of growing a group III nitride semiconductor layer on the base substrate manufactured by the method of manufacturing the base substrate.
10. In the method for producing a group III nitride semiconductor substrate according to 9,
Further, in the step of growing a group III nitride semiconductor layer, a group III nitride semiconductor substrate manufacturing method in which a group III nitride semiconductor layer is grown on each of the front and back surfaces of the base substrate.

Next, examples of the present invention will be described.
Example 1
The base substrate 10 was produced by the same method as in the above embodiment, and then the group III nitride semiconductor layer 21 was formed on the base substrate 10 to obtain the substrate 2.

  A titanium carbide layer was formed as the carbide layer 12. A 60 mmφ sapphire substrate was used as the base material layer 11.

(Titanium carbide layer forming process)
Deposition method: Reactive sputtering Deposition temperature: 800 ° C
Pressure: 0.4Pa
Sputtering gas: Ar gas Reactive gas: CH ₄
Target: Ti
Reactive gas flow rate: 5 sccm
Film thickness: 120nm

(Step of nitriding the titanium carbide layer)
Nitriding temperature: Temperature rising process from 300 ° C. to 900 ° C. (temperature rising rate 20 ° C./min)
Nitriding time: 30 minutes Nitriding gas: NH ₃ gas

Thereafter, a gallium nitride (GaN) semiconductor layer was grown as the group III nitride semiconductor layer 15. First, a buffer layer was formed, and then the main growth of GaN was performed. The conditions are as follows.
(Process for epitaxial growth of GaN semiconductor layer)
(GaN buffer layer)
Deposition method: HVPE
Deposition temperature: 970 ° C
Deposition gas: GaCl gas 180cc / min, NH ₃ gas 3300cc / min
Thickness: 5μm

(Main growth layer)
Deposition method: HVPE
Deposition temperature: 1040 ° C
Deposition gas: GaCl gas 180cc / min, NH ₃ gas 1800cc / min
Thickness: 450μm

After the growth of the main growth layer was finished, the HVPE apparatus was cooled, and the laminate B in which the base material layer, the nitrided carbide layer, and the GaN semiconductor layer were laminated was taken out.
By carrying out the above steps, 20 laminates B in which a base material layer, a nitrided carbide layer, and a GaN semiconductor layer were laminated were prepared.

(Peeling process)
Next, heat treatment was performed as in the above embodiment. Here, heat treatment was performed using the container 6. First, the outer peripheral edge of the laminated body B was fitted into the groove of the holding portion 631 of the jig 63, and 20 laminated bodies B were held by the jig 63.
Thereafter, a jig 63 for holding the laminate B was inserted into the container main body 61. Next, the container body 61 was filled with Ga liquid, and all the laminates B were immersed in the Ga liquid. The layered product B was completely immersed in the Ga liquid, and was not exposed from the Ga liquid.
Next, the opening of the container main body 61 was closed with a lid 62.
Then, the container 6 was arrange | positioned in an HVPE apparatus and the container 6 was heated in nitrogen gas atmosphere. The heat treatment conditions are as follows.
(Heat treatment)
Temperature: 1200 ° C
Atmosphere: N ₂ gas treatment time: 8 hours Heat treatment was performed at 1200 ° C. for 8 hours and then cooled. Since the GaN semiconductor layer is very thin, when the GaN semiconductor layer and the base material layer 11 are peeled off by a force due to a difference in linear expansion coefficient between the GaN semiconductor layer and the base material layer 11 during the cooling process, Cracks. On the other hand, in this example, since the GaN semiconductor layer is not cracked, the adhesion between the GaN semiconductor layer and the base material layer 11 is lost during the heat treatment, and the GaN semiconductor layer and the base layer are treated during the heat treatment. It is considered that peeling from the material layer 11 has occurred.
When the HVPE apparatus is cooled to a certain temperature, the container 6 is taken out from the HVPE apparatus, and the GaN semiconductor layer and the base material layer 11 are removed from the container 6 while heating with a hot plate so that the Ga liquid in the container 6 does not solidify. The laminate B from which was peeled off was taken out.

Thereafter, the structure on the GaN semiconductor layer side obtained by peeling the GaN semiconductor layer and the base material layer 11 was washed. The structure on the GaN semiconductor layer side was immersed in a cleaning solution. Specific cleaning conditions are as follows. In this step, not only the Ga existing at the separation interface between the group III nitride semiconductor layer 15 and the base material layer 11, but also the carbide layer 12B, the nitride layer 13A, and the group III element precipitation layer 14 are removed. It was done.
(Washing process)
Cleaning solution: phosphoric acid + sulfuric acid mixture temperature: 150 ° C
Time: 1 hour The above process yielded 20 self-supporting base substrates 10 made of a GaN semiconductor layer having a thickness of 400 μm.
Thereafter, a thick GaN layer was grown using the obtained base substrate 10. The growth conditions are as follows.
(Thick film growth process)
Deposition method: HVPE
Deposition temperature: 1040 ° C
Deposition gas: GaCl gas 180cc / min, NH3 gas 1800cc / min
Doping: HCl 3 cc / min was mixed with 3 cc / min of dichlorosilane (Si ₂ H ₂ Cl ₂ ) having a Si doping content of 3000 ppm and introduced into the HVPE apparatus.
Thickness: 1100μm

(Comparative Example 1)
After forming the GaN semiconductor layer with the base material layer without carrying out the peeling step of Example 1, the HVPE device was cooled and taken out from the HVPE device in the same manner as in Example 1. Thereafter, the GaN semiconductor layer with the base material layer was again put into the HVPE apparatus, and the same thick film growth as in Example 1 was performed. The GaN layer and the base material layer were separated using thermal stress in the cooling process after the thick film growth. Other points are the same as in the first embodiment. A GaN free-standing substrate having a thickness of 1000 μm was obtained.

(Results of Example 1 and Comparative Example 1)
In Comparative Example 1, cracks occurred in 5 out of 20 GaN free-standing substrates, whereas in Example 1, 20 out of 20 GaN semiconductors did not generate cracks in the heat treatment process. The layer and the base material layer could be peeled off. Therefore, it was possible to obtain 20 GaN free-standing substrates without cracks.

Moreover, the base substrate 10 obtained in Example 1 had a very smooth surface and little in-plane thickness variation. The thickness of the GaN semiconductor layer after measuring the structure on the GaN semiconductor layer side obtained by peeling the GaN semiconductor layer and the base material layer 11 was measured at 8 arbitrary points.
The results are shown in Table 1.
In addition, the reference example of Table 1 heat-processes in nitrogen gas atmosphere, without being immersed in the liquid of Ga during heat processing. Other points such as the heat treatment temperature are the same as those in the first embodiment. Also in the reference example, the thickness of the GaN semiconductor layer after measuring the structure on the GaN semiconductor layer side obtained by peeling the GaN semiconductor layer and the base material layer 11 is measured at eight arbitrary points. In addition, although the average thickness of the GaN semiconductor layer of Example 1 was 400 micrometers, it was 350 micrometers in the reference example.

2 Semiconductor substrate 3 HVPE apparatus 5 Container 6 Container 10 Base substrate 11 Base layer 12 Carbide layer 12A Carbide layer 12B Carbide layer 13 Nitride layer 13A Nitride layer 14 Group III element precipitation layer 15 Group III nitride semiconductor layers 21 and 22 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 tube 36, 37 Heater 38 Shielding plate 39 Growth region 40 Pipe 41 Rotating shaft 50 Container body 51 Side wall 52 Pin 52A-52D Pin 53 Lid 61 Container body 62 Lid 63 Jig 120 Nitrided carbide layer 311 Gas supply pipe 312 Source boat 313 Group III raw material 341 Gas supply pipe 631 Holding part 632 Fixed part A Laminated body B Laminated body L Liquid

Claims (9)

Forming a carbide layer selected from aluminum carbide, titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide and tantalum carbide on the base material layer;
Nitriding the carbide layer;
Epitaxially growing a group III nitride semiconductor layer on the nitrided carbide layer;
A laminate comprising the base material layer, the carbide layer, and the group III nitride semiconductor layer is heat-treated in a state of being immersed in a liquid of a group III element, and the base material layer is removed from the group III nitride semiconductor layer. Peeling and obtaining a base substrate of a group III nitride semiconductor including the group III nitride semiconductor layer ; and
Including
A method of manufacturing a base substrate in which the heat treatment is performed on the stacked body of the base material layer, the carbide layer, and the group III nitride semiconductor layer at a temperature higher than a growth temperature of the epitaxial growth . In the manufacturing method of the base substrate of Claim 1,
The method for producing a base substrate, wherein the group III element liquid is a group III element liquid constituting the group III nitride semiconductor layer. In the manufacturing method of the base substrate of Claim 1 or 2 ,
A method of manufacturing a base substrate, wherein the base material layer, the carbide layer, and the group III nitride semiconductor layer stack are heated at 1100 ° C. or higher and 1300 ° C. or lower when the heat treatment is performed. In the manufacturing method of the base substrate in any one of Claims 1 thru | or 3 ,
When the heat treatment is performed, the laminated body is heat-treated for 5 hours or more in a state of being immersed in the liquid of the group III element, and during the heat treatment, solidification between the group III nitride semiconductor layer and the base material layer is performed. A method of manufacturing a base substrate that reduces adhesion. In the manufacturing method of the base substrate of Claim 1,
When the heat treatment is performed, the laminate of the base material layer, the carbide layer, and the group III nitride semiconductor layer is immersed in a liquid of a group III element, and the group III nitride semiconductor is subjected to the heat treatment. A method for producing a base substrate in which the base material layer peels from the layer. In the manufacturing method of the base substrate in any one of Claims 1 thru | or 5 ,
In the step of epitaxially growing a group III nitride semiconductor layer, a method for manufacturing a base substrate, wherein a group III nitride semiconductor layer having a thickness of 600 μm or less is formed. In the manufacturing method of the base substrate in any one of Claims 1 thru | or 6 ,
When performing the heat treatment,
A method for manufacturing a base substrate, comprising preparing a plurality of the laminates, housing the plurality of laminates in a container, and immersing the plurality of laminates in a Group III element liquid in the container. A method for manufacturing a group III nitride semiconductor substrate including the method for manufacturing a base substrate according to claim 1 ,
A method of manufacturing a group III nitride semiconductor substrate, further comprising a step of growing a group III nitride semiconductor layer on the base substrate manufactured by the method of manufacturing the base substrate. In the manufacturing method of the group III nitride semiconductor substrate according to claim 8 ,
Further, in the step of growing a group III nitride semiconductor layer, a group III nitride semiconductor substrate manufacturing method in which a group III nitride semiconductor layer is grown on each of the front and back surfaces of the base substrate.

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