JP5075692B2 - Group III nitride semiconductor substrate forming substrate - Google Patents

Description

The present invention relates to a group III nitride semiconductor substrate forming board.

  In recent years, attempts have been made to use a bulk crystal of 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, in a group III nitride semiconductor crystal such as GaN, it is difficult to obtain a large bulk crystal from a solution like GaAs due to the high dissociation pressure of nitrogen. Crystal production is very difficult.

For this reason, for example, the HVPE (hydride vapor phase epitaxy) method is mainly used to manufacture the 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 (Al ₂ O ₃ ) 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.

An object of the present invention is to solve the problems described above in obtaining a group III nitride semiconductor substrate, the group III nitride semiconductor substrate forming board which can be obtained a group III nitride semiconductor substrate without requiring labor Is to provide.

  According to the present invention, there is provided a base substrate, a layer provided on the base substrate and nitrided with an aluminum carbide layer, and a group III nitride semiconductor film provided on the layer nitrided with the aluminum carbide layer. A substrate for forming a group nitride semiconductor substrate is provided.

  The substrate for forming a group III nitride semiconductor substrate of the present invention is used to obtain a group III nitride semiconductor substrate, and a group III nitride semiconductor layer is laminated on the group III nitride semiconductor film, By removing the substrate, a group III nitride semiconductor substrate can be obtained.

In the present invention, the layer obtained by nitriding the aluminum carbide layer contains aluminum carbide, aluminum nitride, and carbon.
Here, a method for forming a group III nitride semiconductor substrate using a group III nitride semiconductor substrate forming substrate will be described.
In the process of forming the group III nitride semiconductor layer on the group III nitride semiconductor film of the group III nitride semiconductor substrate forming substrate, nitrogen supplied from the group III nitride semiconductor in the layer obtained by nitriding the aluminum carbide layer Atoms diffuse to produce aluminum nitride and carbon from aluminum carbide.
During the formation of the group III nitride semiconductor layer, AlN forms a mixed crystal with the group III nitride semiconductor, and finally C is concentrated on the boundary surface between the substrate for forming the group III nitride semiconductor substrate and the base substrate. Thus, the group III nitride semiconductor layer is formed.
Since C is inactive with respect to the group III nitride semiconductor layer and the base substrate, the bond strength between the group III nitride semiconductor layer and the base substrate is reduced at the boundary surface where C is concentrated, and the base is formed with extremely small stress. The substrate can be separated.
Therefore, a group III nitride semiconductor substrate can be easily obtained by using the group III nitride semiconductor substrate forming substrate of the present invention.

The above principle will be described in detail as follows.
Aluminum carbide produces AlN and CH ₄ by nitriding as shown in the formula (1). When aluminum carbide is nitrided, Al ₄ C ₃ remains in the portion in contact with the base substrate, and a nitrided aluminum carbide layer having AlN that inherits the crystal information of Al ₄ C ₃ is formed thereon.

Inheritance of crystal information from Al ₄ C ₃ to AlN is very good because the crystal structures of carbide and nitride are the same and the lattice mismatch is small. Furthermore, since the crystal structure of Al ₄ C ₃ and AlN belongs to hexagonal crystal, it is suitable for growing a group III nitride semiconductor film.

Al ₄ C ₃ + 4NH ₃ → 4AlN + 3CH ₄ (1)

In the process of growing the group III nitride semiconductor film on the nitrided aluminum carbide layer, as shown in the formula (1), the group III nitride semiconductor is grown on the AlN. In the remaining Al ₄ C ₃ , nitrogen atoms supplied from the group III nitride semiconductor diffuse through AlN, and the nitriding reaction expressed by the formula (2) proceeds.

Al ₄ C ₃ + 4N → 4AlN + 3C (2) Formula

Therefore, the layer obtained by nitriding the aluminum carbide layer of the formation substrate of the present invention has a structure containing aluminum carbide, aluminum nitride, and carbon.
When a group III nitride semiconductor layer is grown using this forming substrate, AlN forms a mixed crystal with the group III nitride semiconductor, and finally group III nitride in which C is concentrated on the boundary surface with the base substrate. A physical semiconductor layer is formed.

  Since C is inactive to the group III nitride semiconductor and the base substrate, the bond strength between the group III nitride semiconductor layer and the base substrate is reduced at the interface where C is concentrated, and the base substrate is reduced with extremely small stress. Can be separated.

Therefore, according to the present invention, the base substrate can be easily removed from the group III nitride semiconductor layer without taking time and effort as in the prior art, and the method for manufacturing the group III nitride semiconductor substrate is simple. A forming substrate can be provided.
Aluminum carbide has a stoichiometric composition and a C / M molar ratio (M is Al) 3/4, but is not limited to a stoichiometric composition, and it is sufficient that aluminum carbide is formed as a main component.

In this case, the thickness of the III nitride semiconductor film, 20 nm or more, Ru der below 50 [mu] m.

By setting the thickness of the group III nitride semiconductor film to 20 nm or more, the layer obtained by nitriding the aluminum carbide layer can surely contain aluminum carbide, aluminum nitride, and carbon. Thereby, after the group III nitride semiconductor layer is grown, it becomes easy to separate and remove the base substrate.
When the thickness of the group III nitride semiconductor film is less than 20 nm, it is difficult to make the layer obtained by nitriding the aluminum carbide layer contain carbon, and after growing the group III nitride semiconductor layer, the base substrate is formed. Separation and removal may be difficult.
Moreover, by setting the thickness of the group III nitride semiconductor film to 50 μm or less, the layer obtained by nitriding the aluminum carbide layer can surely contain aluminum carbide, aluminum nitride, and carbon. Thereby, after the group III nitride semiconductor layer is grown, it becomes easy to separate and remove the base substrate.
If the thickness of the group III nitride semiconductor film exceeds 50 μm, a carbon layer may be formed on the entire interface between the layer obtained by nitriding the aluminum carbide layer and the base substrate. There is a risk of peeling.

Further, the thickness of the aluminum carbide layer was nitrided layer 20nm or more, Ru der below 140 nm.
By setting the thickness of the nitrided aluminum carbide layer to 20 nm or more, in the process of forming the group III nitride semiconductor substrate, the aluminum carbide becomes almost aluminum nitride, and the group III nitride semiconductor film adheres to the base substrate. Therefore, it is possible to prevent the base substrate from being easily separated and removed.
In addition, by setting the thickness of the layer obtained by nitriding the aluminum carbide layer to 140 nm or less, it is possible to prevent the base substrate from being easily separated and removed in the process of forming the group III nitride semiconductor substrate.
That is, when the thickness of the nitrided carbide Arumini c beam layer layer was in excess of 140nm, the aluminum carbide layer even when forming a group III nitride semiconductor layer in the group III nitride semiconductor substrate formed on a substrate for In some cases, the base substrate and the group III nitride semiconductor layer are firmly bonded to each other by the aluminum carbide layer, so that it may be difficult to separate the base substrate.
In addition, by making the thickness of the layer obtained by nitriding the aluminum carbide layer 140 nm or less, the crystallinity of the group III nitride semiconductor substrate produced using the group III nitride semiconductor substrate forming substrate should be improved. Can do.

Further, a layer obtained by nitriding the aluminum carbide layer includes a carbide of aluminum, and aluminum nitride, including the carbon.
Thus, when the group III nitride semiconductor layer is formed on the group III nitride semiconductor substrate forming substrate according to the present invention, the peelability of the base substrate can be improved.

Furthermore, said base substrate, not formed with a layer of carbon at the interface between the layer formed by nitriding the aluminum carbide layer, the carbon in the layer by nitriding the AlC layer you are dispersed.
By doing in this way, it can suppress that a group III nitride semiconductor film peels from a base substrate in the board | substrate for group III nitride semiconductor substrate formation.

According to the present invention, III-nitride semiconductor substrate forming board which can be obtained a group III nitride semiconductor substrate without the need for labor is provided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, an outline of the present embodiment will be described.
As shown in FIG. 1, the substrate for forming a group III nitride semiconductor substrate 1 of this embodiment includes a base substrate 11, a layer 12 provided on the base substrate 11 and nitrided an aluminum carbide layer, and an aluminum carbide layer. And a group III nitride semiconductor film 13 provided on the nitrided layer 12.
This group III nitride semiconductor substrate forming substrate 1 is used for growing a group III nitride semiconductor layer on a group III nitride semiconductor film 13, removing the base substrate 11, and obtaining a group III nitride semiconductor substrate. It is what is used. This group 1 nitride semiconductor substrate forming substrate 1 is used as a so-called template for forming a group III nitride semiconductor substrate.

Next, the III nitride semiconductor substrate forming substrate 1 of this embodiment will be described in detail.
The base substrate 11 is a sapphire substrate, ZnO substrate, SiC substrate, GaAs substrate, Ga ₂ O ₃ substrate, spinel substrate, or the like.
The layer 12 obtained by nitriding the aluminum carbide layer is provided on the base substrate 11.

The layer 12 obtained by nitriding the aluminum carbide layer contains aluminum carbide, which is a metal carbide, aluminum nitride, which is a metal nitride, and carbon.
The layer 12 includes a first layer 121 containing aluminum carbide, aluminum nitride, and carbon, and a second layer 122 that is an aluminum nitride layer provided on the first layer 121.
In addition, although the layer 12 was comprised with the 1st layer 121 and the 2nd layer 122 here, not only this but the layer 12 may be in the state which is not isolate | separated into two layers clearly.
Carbon is dispersed and precipitated in the first layer 121 and does not cover the entire interface between the base substrate 11 and the first layer 121. In other words, no carbon layer is formed between the first layer 121 and the base substrate 11.
The thickness of this layer 12 is preferably 20 nm or more and 140 nm or less.
Especially, it is especially preferable that it is 20 nm or more and 70 nm or less.

The group III nitride semiconductor film 13 is, for example, Ga _x Al _1-x N (0 ≦ x ≦ 1) or Ga _x In _1-x N (0 ≦ x ≦ 1). In particular, the group III nitride semiconductor film 13 is preferably GaN.
The group III nitride semiconductor film 13 is preferably 20 nm or more and 50 μm or less. Especially, it is especially preferable that it is 70 nm or more and 50 micrometers or less.

Such a group III nitride semiconductor substrate forming substrate 1 can be manufactured as follows. This will be described with reference to FIG.
First, an outline of a method for manufacturing the group 1 nitride semiconductor substrate forming substrate 1 will be described.
(i) forming an aluminum carbide layer 14 on the base substrate 11;
(ii) nitriding the aluminum carbide layer 14 to form a nitrided aluminum carbide layer 15;
(iii) providing a group III nitride semiconductor film 13 on the nitrided carbide layer 15;
including.

Hereinafter, the manufacturing method of the substrate 1 for forming a group III nitride semiconductor substrate will be described in detail.
(Formation process of aluminum carbide layer)
First, the aluminum carbide layer 14 is formed over the base substrate 11 (FIG. 2A). The aluminum carbide layer 14 is formed using an organic aluminum gas (for example, trimethylaluminum) as a source gas.
The film forming conditions for the aluminum carbide layer 14 are, for example, as follows.

Film formation method: metal organic chemical vapor deposition (MOVPE) method Raw material gas: Trimethylaluminum (TMAl), hydrogen (H2) gas, nitrogen (N2) gas Film formation temperature: 300 ° C to 1000 ° C
Deposition time: 5 minutes to 60 minutes Film thickness: 20 nm to 140 nm

As the carrier gas, a gas that does not easily react with trimethylaluminum such as hydrogen, nitrogen, and argon may be selected. Here, hydrogen gas and / or nitrogen gas is used as the carrier gas.
When nitrogen gas is used as the carrier gas, aluminum nitride (AlN) may be formed instead of aluminum carbide if the molar partial pressure of nitrogen gas is set to a certain level or more with respect to the molar partial pressure of TMAl. Therefore, it is necessary to set the molar partial pressure of nitrogen gas to a predetermined value or less with respect to the molar partial pressure of TMAl. In this embodiment, the molar partial pressure ratio of nitrogen gas to the molar partial pressure of TMAl is 1.8 × 10 ⁵ or less (TMAl, 18 ° C.). Preferably, if only hydrogen gas is used as the carrier gas, the formation of AlN does not occur.
Moreover, although the film-forming temperature of the aluminum carbide layer 14 should just be 300 to 1000 degreeC, it is preferable that it is 400 degreeC or more, and it is preferable that it is 600 degrees C or less.

(Step of nitriding the aluminum carbide layer)
Next, as shown in FIG. 2B, the aluminum carbide layer 14 is nitrided in an atmosphere of 300 ° C. to 900 ° C. to form a nitrided aluminum carbide layer 15.
The nitriding conditions for the aluminum carbide layer 14 are, for example, as follows.

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. When the temperature is higher than 550 ° C., CH ₄ is decomposed and C is precipitated as shown in the formula (5), and the crystallinity of the group III nitride semiconductor layer may be deteriorated by mixing C with AlN. 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 (5) Further, the nitriding time is more preferably 30 minutes or less. By setting the nitriding time to about 30 minutes, the aluminum carbide layer 14 can be appropriately nitrided.

Note that ammonia is preferable as a reaction gas when nitriding the aluminum carbide layer 14. AlN can be formed even if nitrogen is used as the reaction gas in addition to ammonia. However, as shown in the formula (6), when AlN and C are formed and C is mixed into AlN, the crystal of the group III nitride semiconductor substrate is formed. May affect quality.
Al ₄ C ₃ + 2N ₂ → 4AlN + 3C (6) Formula The nitriding of the aluminum carbide layer 14 can be performed continuously from the formation step of the aluminum carbide layer in the MOVPE apparatus. it can.
Note that reference numeral 151 shown in FIG. 2B denotes an aluminum carbide layer, and reference numeral 152 denotes an aluminum nitride layer. That is, Al ₄ C ₃ remains in the portion in contact with the substrate 11, and an AlN layer that inherits the crystal information of Al ₄ C ₃ is formed on the Al ₄ C ₃ .
In this nitriding step, the entire surface of the interface between the base substrate 11 and the layer 151 is not covered with carbon, and the aluminum carbide layer 14 is nitrided to such an extent that no carbon layer is formed at this interface.

(Step of forming group III nitride semiconductor film 13)
Next, a group III nitride semiconductor film 13 is provided on the nitrided aluminum carbide layer 15 (see FIG. 1).
The group III nitride semiconductor film 13 is, for example, GaN, and the film formation conditions can be as follows, for example.

Film forming method: MOVPE film forming temperature: 300 ° C. to 1050 ° C.
Film forming gas: Trimethylgallium (TMG) gas, H2 gas, N2 gas, NH3 gas Film thickness: 20 nm to 50 [mu] m
Film formation time: 10 minutes to 40 minutes The formation of the group III nitride semiconductor film 13 can be performed continuously from the step of nitriding the aluminum carbide layer in the MOVPE apparatus.
In the process of forming the group III nitride semiconductor film 13, the aluminum carbide layer 151 is formed of nitrogen atoms supplied from the group III nitride semiconductor film 13 in the process of increasing the thickness of the group III nitride semiconductor film 13. Nitrided to produce aluminum nitride and carbon. Accordingly, as shown in FIG. 1, a layer 121 containing carbon, aluminum carbide, and aluminum nitride, and an aluminum nitride layer 122 are formed. This corresponds to the layer 12 obtained by nitriding the carbide layer.
Here, the group III nitride semiconductor film 13 is formed to such an extent that the base substrate 11 does not peel from the nitrided layer 12 of the carbide layer, that is, no carbon layer is deposited at the interface between the base substrate 11 and the layer 12. It is necessary to carry out the process so that the entire interface is not covered with carbon. For example, when the film is formed at 300 ° C., the film formation time is 40 minutes, and when the film is formed at 700 ° C., the film formation time is 15 minutes. Further, when the film is formed at 1000 ° C., the film formation time is 11 minutes, and when the film is formed at 1050 ° C., the film formation time is 10 minutes.
The group 1 nitride semiconductor substrate forming substrate 1 manufactured in this way is cooled to room temperature, but the base substrate 11 is not peeled off in this cooling step.
Since the above steps can be performed consistently in the MOVPE apparatus, the substrate 1 for forming a group III nitride semiconductor substrate can be easily produced in a short time without contamination by fine particles or gas floating in the atmosphere. Is possible.

Next, a method for manufacturing a group III nitride semiconductor substrate using the substrate for forming a group III nitride semiconductor substrate 1 manufactured as described above will be described with reference to FIG.
First, as shown in FIG. 3A, a group III nitride semiconductor layer 21 is epitaxially grown on the group III nitride semiconductor film 13.
The group III nitride semiconductor layer 21 is the same group III nitride as the group III nitride semiconductor film 13 and is, for example, GaN.
The growth conditions of group III nitride semiconductor layer 21 can be, for example, as follows.

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: 250 μm to 2000 μm
In the HVPE apparatus (not shown), a Ga source is disposed, and HCl gas is supplied to the Ga source. HCl gas and Ga source are reacted to transport GaCl to a region near the group III nitride semiconductor film 13. Since the NH ₃ gas is also supplied to the region in the vicinity of the group III nitride semiconductor film 13, the NH ₃ gas and GaCl react to grow GaN to form the group III nitride semiconductor layer 21. It becomes. In the process of increasing the thickness of the group III nitride semiconductor layer 21, the aluminum nitride 122 forms a mixed crystal with GaN. Aluminum carbide 121 is nitrided with nitrogen atoms supplied from GaN to produce aluminum nitride and carbon. Since aluminum nitride forms a mixed crystal with GaN, finally, as shown in FIG. 3A, a GaN semiconductor layer enriched with C is generated at the interface with the base substrate 11. In FIG. 3A, reference numeral 16 denotes a carbon layer which is a C enrichment part.

(Undersubstrate peeling process)
Next, as shown in FIG. 3B, the base substrate 11 is peeled and removed from the GaN semiconductor layer in which C is concentrated on the interface with the base substrate 11.
Specifically, the temperature of the HVPE apparatus in which the GaN semiconductor layer is formed is lowered, and the GaN semiconductor layer is cooled to room temperature.
During this cooling, the stacked body is distorted due to the difference in thermal expansion coefficient between the GaN semiconductor layer and the base substrate 11, and the GaN semiconductor layer and the base substrate 11 are separated. Since C is inactive with respect to the base substrate 11, the bond strength with the base substrate 11 decreases at the boundary surface where C is concentrated, and the base substrate 11 can be separated with extremely small stress.
Thereafter, by polishing the front surface and the back surface of the separated GaN semiconductor layer, a GaN substrate that is a flattened self-supporting substrate can be manufactured.

Next, the effect of this embodiment is demonstrated.
The nitrided layer 12 contains aluminum carbide, aluminum nitride, and carbon.
In the process of forming the group III nitride semiconductor layer 21 on the group III nitride semiconductor film 13, nitrogen atoms supplied from the group III nitride semiconductor diffuse into the nitrided layer 12, and aluminum carbide and aluminum nitride , Carbon and are produced.
During the formation of the group III nitride semiconductor layer 21, AlN forms a mixed crystal with the group III nitride semiconductor, and finally a group III nitride semiconductor layer in which C is concentrated on the boundary surface with the base substrate 11 is formed. It is formed.
Since C is inactive with respect to the group III nitride semiconductor layer and the base substrate 11, the bond strength between the group III nitride semiconductor layer and the base substrate 11 decreases at the interface where C is concentrated, and extremely small stress is applied. Thus, the base substrate 11 can be separated.
Therefore, the group III nitride semiconductor substrate can be easily obtained by using the group III nitride semiconductor substrate forming substrate 1 of the present embodiment.

Further, by setting the thickness of the group III nitride semiconductor film 13 to 20 nm or more, the layer 12 obtained by nitriding the aluminum carbide layer can contain aluminum carbide, aluminum nitride, and carbon. Thereby, after the group III nitride semiconductor layer 21 is grown, it is easy to separate and remove the base substrate 11.
When the thickness of the group III nitride semiconductor film 13 is less than 20 nm, it becomes difficult for the nitrided layer 12 to contain carbon, and after the group III nitride semiconductor layer 21 is grown, the base substrate 11 may be difficult to separate and remove.

Further, by setting the thickness of the group III nitride semiconductor film 13 to 50 μm or less, the layer 12 obtained by nitriding the aluminum carbide layer can contain aluminum carbide, aluminum nitride, and carbon. Thereby, after the group III nitride semiconductor layer 21 is grown, it is easy to separate and remove the base substrate 11.
When the thickness of the group III nitride semiconductor film 13 exceeds 50 μm, carbon may cover the entire interface between the layer 12 obtained by nitriding the aluminum carbide layer and the base substrate 11. May peel off.
In addition, the crystallinity of the group III nitride semiconductor layer 21 can be made favorable by setting the group III nitride semiconductor film 13 to 70 nm or more.

Furthermore, the group 12 nitride semiconductor film 13 can be prevented from adhering to the base substrate 11 by setting the thickness of the layer 12 obtained by nitriding the aluminum carbide layer to 20 nm or more.
That is, when the thickness of the layer 12 is less than 20 nm, the layer 12 is almost aluminum nitride, and the group III nitride semiconductor film 13 may be firmly bonded to the base substrate 11 via the aluminum nitride. Therefore, it may be difficult to separate and remove the base substrate 11 after the group III nitride semiconductor layer 21 is grown.
The crystallinity of the group III nitride semiconductor layer 21 can be improved by setting the thickness of the layer 12 obtained by nitriding the aluminum carbide layer to 70 nm or less.

By setting the thickness of the layer 12 obtained by nitriding the aluminum carbide layer to 140 nm or less, the group III nitride semiconductor film 13 can be prevented from adhering to the base substrate 11.
That is, when the thickness of the layer 12 exceeds 140 nm, the aluminum carbide layer remains even after the group III nitride semiconductor layer 21 is grown, and the aluminum carbide layer causes the base substrate 11 and the group III nitride semiconductor to remain. Since the film 13 is firmly bonded, it may be difficult to separate and remove the base substrate 11.
Furthermore, by making the thickness of the layer 12 obtained by nitriding the aluminum carbide layer 140 nm or less, the crystallinity of the group III nitride semiconductor substrate produced using the group III nitride semiconductor substrate forming substrate 1 is improved. can do.

Further, in the present embodiment, carbon is not deposited on the entire interface between the base substrate 11 and the layer 12 obtained by nitriding the carbide layer in the group III nitride semiconductor substrate forming substrate 1, and a carbon layer is also formed. Absent.
By doing in this way, it can suppress that the group III nitride semiconductor film 13 peels from the base substrate 11 in the board | substrate 1 for group III nitride semiconductor substrate formation.

In addition, the present inventors have previously proposed a method of manufacturing a group III nitride semiconductor substrate that can easily remove the base substrate. In this method, a carbide layer selected from aluminum carbide, titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, or tantalum carbide is formed on a base substrate, and the carbide layer is nitrided, and then a group III nitride is formed. This is a method of epitaxially growing a compound semiconductor layer, removing the base substrate from the group III nitride semiconductor layer, and obtaining a group III nitride semiconductor substrate including the group III nitride semiconductor layer.
In this method, it is preferable to continuously perform the steps from the formation of the carbide layer to the removal of the base substrate.
In contrast, by using the group III nitride semiconductor substrate forming substrate 1 of the present embodiment, it is not necessary to continuously perform the steps from the formation of the carbide layer to the removal of the base substrate.

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.
For example, in the embodiment, the group III nitride semiconductor film 13 is formed by the MOVPE method. However, the present invention is not limited to this, and the group III nitride semiconductor film 13 may be formed by the HVPE method. Alternatively, an aluminum carbide layer may be formed by sputtering, and the group III nitride semiconductor film 13 may be formed by HVPE.

  Moreover, in the said embodiment, although the group III nitride semiconductor layer was formed by HVPE method, you may form not only this but a flux method and an ammonothermal method, for example.

Further, when forming the group III nitride semiconductor layer, it may be formed by the FIELO method. Specifically, an SiO ₂ film serving as a mask is formed on the surface of the substrate for forming a group III nitride semiconductor substrate 1 and a <1-100> direction ((<11-20 of GaN) of the sapphire substrate (underlying substrate 11). GaN semiconductor layer finally formed when a GaN semiconductor layer is grown while forming a facet structure having a {1-101} side wall in the opening provided with a stripe-shaped opening in a direction along the> direction)) Transmission of crystal defects in the layer is suppressed. For this reason, the quality of the obtained GaN semiconductor substrate can be improved.

  In the embodiment, the nitriding gas is used to nitride the aluminum carbide layer. However, the present invention is not limited to this. For example, by forming an aluminum nitride layer on the aluminum carbide layer, the carbide layer is nitrided. Also good.

Hereinafter, the present invention will be described in more detail, but the present invention is not limited to the following examples.
Example 1
The same process as described in the above embodiment was performed to manufacture a group III nitride semiconductor substrate forming substrate.
(Formation process of aluminum carbide layer)
Film formation method: MOVPE film formation temperature: 500 ° C.
Deposition time: 5 minutes Deposition gas: TMAl 20 cc / min (18 ° C.), H ₂ gas 6 L / min, N ₂ gas 10.5 L / min
Film thickness: 70nm

(Step of nitriding the aluminum carbide layer)
Nitriding temperature: 500 ° C
Nitriding time: 30 minutes Nitriding gas: NH ₃ gas 5 L / min, H ₂ gas 6 L / min, N ₂ gas 4.5 L / min

(Process for forming GaN semiconductor film)
Film formation method: MOVPE film formation temperature: 500 ° C.
Deposition gas: TMG 4 cc / min (10 ° C.), NH ₃ gas 5 L / min, H ₂ gas 6 L / min, N 2 gas 4.5 L / min
Film thickness: 70 nm
Deposition time: 30 minutes

The group III nitride semiconductor substrate forming substrate thus obtained was cooled to room temperature, but the base substrate was not peeled off in the group III nitride semiconductor substrate forming substrate.
Next, a GaN semiconductor layer was epitaxially grown using this group III nitride semiconductor substrate forming substrate to obtain a group III nitride semiconductor substrate.

(Process for epitaxial growth of GaN semiconductor layer)
Deposition method: HVPE Deposition temperature: 1040 ° C
Deposition gas: HCl gas 0.15 L / min, NH ₃ gas 1.5 L / min
Source: Ga source (850 ° C.)
Film thickness: 310μm
Temperature profile: Fig. 4
In FIG. 4, the arrow on the lower side of GaCl indicates that GaCl is generated between 50 minutes and 80 minutes and 90 to 180 minutes, and the arrow on the upper side of NH ₃ is the middle of the arrow. , NH ₃ gas supply time is shown.

(Sapphire substrate peeling process)
The temperature in the HVPE apparatus on which the GaN semiconductor layer was formed was lowered and cooled to room temperature. In the cooling process, the base substrate was peeled off satisfactorily, and a GaN semiconductor substrate having a film thickness of about 300 μm could be obtained. When the half width of the X-ray rocking curve of the (0002) plane of this GaN semiconductor substrate was measured, it was 600 arcsec.

(Example 2)
The thickness of the GaN semiconductor film was 20 nm.
Other conditions are the same as those in Example 1.
Also in Example 2, the base substrate did not peel off in the group III nitride semiconductor substrate forming substrate.
Further, when the GaN semiconductor substrate was manufactured, the base substrate could be peeled off, and a GaN semiconductor substrate having a film thickness of about 300 μm could be obtained. The half width of the X-ray rocking curve of the (0002) plane of this GaN semiconductor substrate was measured and found to be 650 arcsec.

(Example 3)
The thickness of the GaN semiconductor film was 50 μm.
Other conditions are the same as those in Example 1.
Also in Example 3, the base substrate did not peel off in the group III nitride semiconductor substrate forming substrate.
Also in Example 3, when the GaN semiconductor substrate was manufactured, the base substrate was peeled off satisfactorily, and a GaN semiconductor substrate having a film thickness of about 300 μm could be obtained. When the half width of the X-ray rocking curve of the (0002) plane of this GaN semiconductor substrate was measured, it was 250 arcsec.

Example 4
The thickness of the GaN semiconductor film was 20 μm.
Other conditions are the same as those in Example 1.
Also in Example 4, the base substrate did not peel off in the group III nitride semiconductor substrate forming substrate.
Also in Example 4, when the GaN semiconductor substrate was manufactured, the base substrate could be peeled well, and a GaN semiconductor substrate having a film thickness of about 300 μm could be obtained. When the half width of the X-ray rocking curve of the (0002) plane of this GaN semiconductor substrate was measured, it was 300 arcsec.

(Example 5)
The thickness of the aluminum carbide layer was 20 nm.
Other conditions are the same as those in Example 1.
Also in Example 5, the base substrate did not peel off in the group III nitride semiconductor substrate forming substrate.
Further, when the GaN semiconductor substrate was manufactured, the base substrate was peeled off satisfactorily, and a GaN semiconductor substrate having a film thickness of about 300 μm could be obtained. When the half width of the X-ray rocking curve of the (0002) plane of this GaN semiconductor substrate was measured, it was 250 arcsec.

(Example 6)
The thickness of the aluminum carbide layer was 140 nm.
Other conditions are the same as those in Example 1.
Also in Example 6, the base substrate did not peel off in the group III nitride semiconductor substrate forming substrate.
Also in Example 6, when the GaN semiconductor substrate was manufactured, the base substrate was peeled off satisfactorily, and a GaN semiconductor substrate having a film thickness of about 300 μm could be obtained. When the half width of the X-ray rocking curve of the (0002) plane of this GaN semiconductor substrate was measured, it was 700 arcsec.

It is a schematic diagram showing a substrate for forming a group III nitride semiconductor substrate according to an embodiment of the present invention. It is a schematic diagram which shows the manufacturing process of the board | substrate for group III nitride semiconductor substrate formation concerning embodiment of this invention. It is a schematic diagram which shows the manufacturing process of the group III nitride semiconductor substrate which uses the board | substrate for group III nitride semiconductor substrate formation concerning embodiment of this invention. It is a figure which shows the temperature profile of the process of epitaxially growing the GaN semiconductor layer of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Group III nitride semiconductor substrate formation substrate 11 Base substrate 12 Layer nitrided layer 13 Group III nitride semiconductor film 14 Aluminum carbide layer 15 Aluminum nitride layer 16 Carbon enriched portion of carbon 21 Group 21 nitrided Semiconductor layer 121 first layer 122 second layer 151 aluminum carbide layer 152 aluminum nitride layer

Claims (1)

A base substrate;
A layer provided on the base substrate and nitrided an aluminum carbide layer;
A group III nitride semiconductor film provided on a layer obtained by nitriding the aluminum carbide layer,
The thickness of the group III nitride semiconductor film is 20 nm or more and 50 μm or less,
The thickness of the layer obtained by nitriding the aluminum carbide layer is 20 nm or more and 140 nm or less,
The layer obtained by nitriding the aluminum carbide layer includes aluminum carbide, aluminum nitride, and carbon.
A group III nitride semiconductor substrate in which no carbon layer is formed at the interface between the base substrate and the layer obtained by nitriding the aluminum carbide layer, and the carbon is dispersed in the layer obtained by nitriding the aluminum carbide layer Substrate for forming.

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