JP2018168029A - Template for growing group iii nitride semiconductor - Google Patents

Abstract

To provide a template for growing a group III nitride semiconductor capable of growing the group III nitride semiconductor having a small crystal dislocation density.SOLUTION: There is provided a template for growing a group III nitride semiconductor comprising a laminate containing a support substrate and an insulator film which is a mask pattern having a plurality of opening parts, in this order. In the template for growing the group III nitride semiconductor, the insulator film contains GaOas a principal ingredient.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a group III nitride semiconductor growth template and a group III nitride semiconductor substrate using the group III nitride semiconductor growth template.

  When a selective growth mask is formed on a sapphire substrate and a GaN-based film is grown by ELO (Epitaxial Lateral Overgrowth), the GaN-based film has a difference in growth rate between the horizontal direction and the vertical direction in the ELO. Growing so as to embed a selective growth mask. At this time, since crystal defects are generated along the lateral growth, dislocations are extremely reduced in the GaN film formed by ELO on the selective growth mask. When an element structure is obtained by laminating an epitaxial layer thereon, a defect density is very low, and a semiconductor light emitting element having excellent light emission characteristics can be obtained (Patent Documents 1 and 2, and Non-Patent Document 1). . However, further reduction in the defect density of the GaN film has been demanded.

JP 2001-177145 A JP 2003-229372 A

NATURE PHOTOTONICS | VOL 5 | DECEMBER 2011, p763

  An object of the present invention is to provide a group III nitride semiconductor growth template capable of growing a group III nitride semiconductor having a low crystal dislocation density.

According to the present invention, the following group III nitride semiconductor growth template and the like are provided.
1. A group III nitride semiconductor growth template comprising a laminated body including a support substrate and an insulating film which is a mask pattern having a plurality of openings in this order,
A group III nitride semiconductor growth template, wherein the insulating film contains Ga ₂ O ₃ as a main component.
2. _{2. The} group III nitride semiconductor growth template according to 1, wherein the insulating film is one or more selected from SnO ₂ and In ₂ O ₃ and Ga ₂ O ₃ .
3. Including a buffer layer between the support substrate and the insulating film;
The buffer layer is made of low-temperature grown GaN, low-temperature grown AlN, Ti, TiN, Al ₂ O ₃ , 6H—SiC, LiAlO ₂ , LiGaO ₂ , ZnO, (LaAlO ₃ ) 0.3 − (SrAl _0.5 Ta _0. Group III nitride semiconductor growth according to 1 or 2, consisting of ₅ O ₃ ) 0.7, MnAl ₂ O ₄ , LiNbO ₃ , LaNiO ₃ , ScMgAlO ₄ , LiTaO ₃ , NdGaO ₃ , graphene, corundum ITO, or corundum ITZO Template.
4). 4. The group III nitride semiconductor growth template according to 3, wherein the buffer layer is exposed from the opening, and the buffer layer is made of the low-temperature grown GaN.
5. The group III nitride semiconductor growth template according to any one of 1 to 4, wherein the support substrate is a glass substrate.
A Group III nitride semiconductor substrate having a Group III nitride semiconductor on the insulating film of the Group III nitride semiconductor growth template according to any one of 6.1 to 5.
7). 7. The group III nitride semiconductor substrate according to 6, wherein the group III nitride semiconductor is made of GaN, AlN, AlGaN, or InGaN.
8). The group III nitride semiconductor is formed by filling an opening of a mask pattern of the insulating film,
When the crystal dislocation density of the group III nitride semiconductor on the opening is A and the crystal dislocation density of the group III nitride semiconductor on the mask pattern is B, 1 ≦ B / A ≦ 100 is satisfied. 7. A group III nitride semiconductor substrate according to 7.

  According to the present invention, a group III nitride semiconductor growth template capable of growing a group III nitride semiconductor having a low crystal dislocation density can be provided.

It is a schematic sectional drawing which shows one Embodiment of the template for group III nitride semiconductor growth of this invention. FIG. 3 is a schematic plan view of the group III nitride semiconductor growth template of FIG. 1. It is a schematic sectional drawing which shows one Embodiment of the group III nitride semiconductor substrate of this invention. FIG. 4 is a schematic plan view of the group III nitride semiconductor substrate of FIG. 3.

[Group III nitride semiconductor growth template]
The group III nitride semiconductor growth template of the present invention is a laminated body including a support substrate and an insulating film which is a mask pattern having a plurality of openings in this order, and the insulating film contains Ga ₂ O ₃ as a main component. Including.

The insulating film, which is a mask pattern having a plurality of openings, has a function of separating the growth region and the non-growth region of the group III nitride semiconductor, and the group III nitride semiconductor grows starting from the openings. As the insulating film, Si-based insulating films such as SiO ₂ and SiN are known. However, Si has a property of easily reacting with nitride, and Si in the insulating film may diffuse into the group III nitride semiconductor, which may increase the defect density of the group III nitride semiconductor. Further, when the template includes a buffer layer made of low-temperature grown GaN, contamination of the surface of the buffer layer becomes a problem. Specifically, SiO ₂ and SiN used for forming the insulating film are usually formed by PE-CVD. However, when forming the film on the low-temperature growth GaN buffer layer, SiH _{4 as the} introduced gas is formed on the GaN surface. Causes a chemical reaction. This GaN surface is a surface on which GaN is epitaxially grown by MOCVD in a later step, and the defect density of the GaN film directly above the buffer layer remains high compared to the GaN film that has been crystal-grown laterally by ELO. There is.
In the present invention, since the insulating film contains Ga ₂ O ₃ as a main component, it does not react with the nitride in contact with the insulating film, and the defect density of the group III nitride semiconductor can be reduced.

FIG. 1 is a schematic cross-sectional view showing one embodiment of a group III nitride semiconductor growth template of the present invention.
In the group 1 nitride semiconductor growth template 1, the first buffer layer 30 and the second buffer layer 40 are stacked in this order on the support substrate 20, and the opening 12 is formed on the second buffer layer 40. An insulating film 10 which is a mask pattern provided is laminated.
The group III nitride semiconductor growth template of the present invention preferably includes a buffer layer between the support substrate and the insulating film. In FIG. 1, there are two buffer layers. However, a single buffer layer is also included in the group III nitride semiconductor growth template of this embodiment.
Hereinafter, each layer will be described.

The insulating film is a layer that promotes epitaxial lateral growth, and contains Ga ₂ O ₃ as a main component. Here, “containing Ga ₂ O ₃ as a main component” means, for example, that the content of Ga ₂ O ₃ in the insulating film is 50 atomic% or more.
The insulating film may contain Ga ₂ O ₃ as a main component, and may further contain one or more selected from SnO ₂ and In ₂ O ₃ . When the insulating film is made of Ga ₂ O ₃ and SnO ₂ , it is preferable to satisfy the atomic ratio Sn / (Ga + Sn) = 2 to 20% in the insulating film, and more preferable to satisfy Sn / (Ga + Sn) = 3 to 10%. .
Insulating film, _Ga 2 _{O 3} may consist only may consist of only one or a _Ga 2 _{O 3} is selected from SnO ₂ and _In 2 _{O 3.}

The insulating film is a mask pattern having a plurality of openings, and the shape of the openings is, for example, a cylindrical through hole. FIG. 2 is a schematic plan view of the group III nitride semiconductor growth template of FIG. In FIG. 2, openings 12 that are through holes are formed at regular intervals.
The pattern of the through hole is not particularly limited, but the diameter of the hole is preferably 0.1 to 20 μm, more preferably 0.2 to 10 μm, in order to efficiently promote the ELO of the group III nitride semiconductor. If the diameter of the hole is less than 0.1 μm, the cost of patterning by photolithography of an insulating film described later may increase. If the diameter of the hole exceeds 20 μm, the region where the group III nitride semiconductor is selectively grown becomes too large, and it may be difficult to obtain a group III nitride semiconductor having a low defect density.
The through-hole pattern may be a conventionally known stripe pattern. The preferred width of the stripe pattern is suitably selected in the range of window / mask = 1 μm / 3 μm to 10 μm / 50 μm.
The thickness of the insulating film is, for example, 10 nm to 1 μm.

As a constituent material of the support substrate, for example, sapphire, alumina, conductive alumina, silicon (Si), silicon carbide (SiC), quartz glass and the like can be used, and a material having heat resistance of 1000 ° C. or higher is preferable. Among these, a support substrate (glass substrate) made of quartz glass is preferable from the viewpoint of cost.
The support substrate may be formed of one of these constituent materials alone or in combination of two or more.

  Although there is no restriction | limiting in particular in the thickness of a support substrate, 200-1000 micrometers is preferable from viewpoints of handling, such as manufacturing processing. If it is necessary to reduce the electrical resistance in the vertical direction by using a template for manufacturing a diode, the substrate may be polished by a CMP method or the like.

The buffer layer is a layer provided for the purpose of epitaxially growing a good crystalline nitride semiconductor with a further reduced defect density.
As a constituent material of the buffer layer, a conventionally known material can be used as appropriate. Low-temperature growth GaN (LT-GaN), low-temperature growth AlN (LT-AlN), Ti, TiN, Al ₂ O ₃ , 6H—SiC, LiAlO _{2 , LiGaO 2, ZnO, LSAT (} ((LaAlO 3) 0.3- (SrAl 0.5 Ta 0.5 O 3) 0.7)), MnAl 2 O 4, LiNbO 3, LaNiO 3, ScMgAlO 4, LiTaO ₃ , NdGaO ₃ , graphene, corundum ITO, or corundum ITZO can be used.
The buffer layer may be formed of one of these constituent materials alone or in combination of two or more. The buffer layer may be a single layer or a laminate of two or more layers.

When the supporting substrate is a glass substrate, it is difficult to directly deposit a high-quality GaN crystal, and a material such as Ti, TiN, LaNiO ₃ , ZnO or the like that easily takes a uniaxially oriented structure regardless of the type of the substrate. Is preferably laminated as a buffer layer. The “uniaxially oriented structure” refers to a crystal structure in which all orientation planes are in the same direction, and refers to a single composition polycrystalline structure having the same orientation plane. It can be confirmed by XRD diffraction that the buffer layer has a uniaxially oriented structure.
When the support substrate is a silicon substrate, the silicon substrate is inexpensive and excellent in smoothness, but if nitride is deposited, there is a problem of meltback etching, so the constituent material of the buffer layer does not contain nitride Is preferred.
The thickness of the buffer layer may be appropriately set according to the purpose.

[Group III nitride semiconductor substrate]
The group III nitride semiconductor substrate of the present invention has a group III nitride semiconductor on the insulating film of the group III nitride semiconductor growth template of the present invention.
The group III nitride semiconductor is preferably formed so as to fill the opening of the mask pattern of the insulating film. In this case, when the crystal dislocation density of the group III nitride semiconductor on the opening of the insulating film is A and the crystal dislocation density of the group III nitride semiconductor on the mask pattern of the insulating film is B, 1 ≦ B / It is preferable that A ≦ 100 is satisfied.
When the group III nitride semiconductor satisfies 1 ≦ B / A ≦ 100, it means that the group III nitride semiconductor has a low defect density. When the crystal dislocation density of the group III nitride semiconductor on the opening of the insulating film is A and the crystal dislocation density of the group III nitride semiconductor on the mask pattern of the insulating film is B, 1 ≦ B / A ≦ 10 More preferably, it is more preferable that 1 ≦ B / A ≦ 2.5.
The evaluation of the crystal dislocation density can be confirmed by the method described in Examples.

  FIG. 3 is a schematic cross-sectional view showing an embodiment of a group III nitride semiconductor substrate of the present invention. In the group III nitride semiconductor substrate 2, the opening 12 of the insulating film 10 is filled to form a group III nitride semiconductor. 50 is formed. FIG. 4 is a schematic plan view of the group III nitride semiconductor substrate of FIG. 3, in which a group III nitride semiconductor 50 is formed in a hexagonal pyramid shape.

  The constituent material of the group III nitride semiconductor is preferably a compound of N and at least one selected from In, Al, and Ga. Examples of the compound of N and one or more selected from In, Al, and Ga include GaN, AlN, AlGaN, and InGaN. These GaN, AlN, AlGaN, and InGaN are all compounds that can have a hexagonal crystal structure.

  The nitride semiconductor layer may have a single layer configuration or a multilayer configuration. Here, the single layer configuration is a layer formed of one kind of compound. For example, when the nitride semiconductor layer is a layer made of a compound of N and one or more selected from In, Al, and Ga, the layer is preferably an epitaxial layer.

  The thickness of the nitride semiconductor layer can be appropriately changed depending on the use of the group III nitride semiconductor substrate. For example, when used as a diode, the thickness is 10 μV to 0.03 μm to 1.2 μm, and the 60 V breakdown voltage is 0.2 μm to In the case of 1.2 μm and 600V breakdown voltage, 2 μm to 12 μm is preferable.

[Group III Nitride Semiconductor Growth Template and Group III Nitride Semiconductor Substrate Manufacturing Method]
The group III nitride semiconductor growth template of the present invention can be manufactured by forming a buffer layer and an insulating film on a supporting substrate, and etching the insulating film to form an opening. In addition, a group III nitride semiconductor substrate can be manufactured by forming a group III nitride semiconductor in the opening of the insulating film.

A film formation method for forming the buffer layer and the insulating film over the supporting substrate is not particularly limited, and a known method can be used. For example, conventionally known manufacturing methods suitable for thick films such as sputtering methods, mist CVD methods, doctor blade methods, injection methods, extrusion methods, hot pressing methods, ceramic manufacturing methods, ion plating methods, aerosol deposition methods, etc. Can be used.
Note that in the formation of the insulating film containing Ga ₂ O ₃ as a main component, the film formation temperature is preferably room temperature to 400 ° C. When the film forming temperature exceeds 400 ° C., crystallization of Ga ₂ O ₃ starts, and high concentration HF having a concentration of 47% or more, phosphoric acid having a temperature of 200 ° C. or more are required for etching. In this case, the buffer layer may be damaged during overetching.
The film formation temperature in forming the insulating film containing Ga ₂ O ₃ as a main component is more preferably room temperature to 300 ° C., and further preferably room temperature to 200 ° C.

In the etching of the insulating film, when it is a Si-based insulating film such as SiO ₂ or SiN, dry etching using CF ₄ or the like is usually used. Surface damage becomes a problem in the process. Furthermore, as a buffer layer for promoting high-quality GaN crystals, low-temperature grown AlN, Ti, TiN, Al ₂ O ₃ , 6H—SiC, LiAlO ₂ , LiGaO ₂ , ZnO, LSAT, MnAl ₂ O ₄ , LiNbO ₃ , LaNiO _{3 3} , ScMgAlO ₄ , LiTaO ₃ , NdGaO ₃ , graphene, corundum ITO, corundum ITZO, and the like, but these are not necessarily resistant to the etching gas of SiO ₂ or SiNx.
In the present invention, the insulating film contains Ga ₂ O ₃ as a main component, and the Ga ₂ O ₃ is an amphoteric oxide and can be dissolved in a weak alkali, so that it can be easily etched without damaging the buffer layer. The etching rate can also be adjusted by adding an appropriate amount of SnO ₂ and / or In ₂ O ₃ .

The opening of the insulating film can be formed by using a conventionally known photolithography method or the like. For example, after Ga ₂ O _{3 is formed} by RF magnetron sputtering, a positive resist is applied by spin coating, exposed through a photomask having a through-hole pattern, and developed. An organic alkali such as TMAH (tetramethylammonium hydroxide) may be used for the developer. In the case where the Ga ₂ O ₃ film is significantly dissolved, an insulating film may be formed using a material containing SnO ₂ in a proportion of ₂ to 20 atomic% in Ga ₂ O ₃ . After development, through-holes can be formed by etching with an acid such as HF, BHF (buffered hydrofluoric acid), hydrochloric acid, sulfuric acid, phosphoric acid or the like.

  The method for forming a nitride semiconductor layer such as a GaN layer, an AlGaN layer, or an InGaN layer on the insulating film is not limited. For example, metal organic vapor phase epitaxy (MOCVD method); Hydride Vaor Phase Epitaxy method The film can be formed by a CVD growth method such as (HVPE method); molecular beam epitaxy method (MBE method); sputter epitaxy method or the like. In addition to GaN, InGaN, and AlGaN as materials for the epitaxial layer, these mixed crystals and doping for controlling pn can also be applied by a conventionally known method.

  By using the group III nitride semiconductor growth template and the group III nitride semiconductor substrate of the present invention, a diode or MOSFET comprising GaN, AlGaN, AlN or the like can be obtained. The diode includes a light emitting diode, a Schottky barrier diode, a laser diode, and the like.

Example 1
[Manufacture of Group III Nitride Semiconductor Growth Template]
A template having the same layer configuration as that of the group III nitride semiconductor growth template shown in FIG. 1 was manufactured by the following method.
A 2-inch sapphire substrate was ultrasonically cleaned with an organic solvent and previously cleaned at 960 ° C. for 30 minutes. Next, titanium was deposited on the c-plane with a 100 nm electron beam at a substrate temperature of room temperature. The titanium functions as a first buffer layer. Next, after setting the substrate in the MOCVD apparatus and heating to 560 ° C., a mixed gas of NH ₃ , H ₂ and trimethyl gallium is introduced to form a second buffer layer made of low-temperature grown GaN having a thickness of 130 nm. did.
Subsequently, the substrate obtained in the sputtering apparatus was set, and RF sputtering was performed by using an oxide sintered body of gallium and tin (Ga ₂ O ₃ : SnO ₂ = 95: 5 (atomic ratio)) as a target. A 300 nm insulating film was formed. The insulating film was formed at 100 ° C. Next, a resist was applied to the substrate, and after exposure and development through a photomask, etching with phosphoric acid was performed. After post-baking, the resist was peeled off to form a contact hole in which 2.5 μm diameter was aligned at a pitch of 5 μm to form a mask pattern, and a group III nitride semiconductor growth template was manufactured.

[Manufacture and evaluation of group III nitride semiconductor substrates]
The obtained group III nitride semiconductor growth template was set in a MOCVD apparatus, the substrate was heated to 1040 ° C., and then a mixed gas of NH ₃ , H ₂ and trimethyl gallium was introduced, and a 700 nm thick GaN layer (high temperature A GaN epitaxial layer) was formed to produce a group III nitride semiconductor substrate.
About the manufactured group III nitride semiconductor substrate, the threading dislocation density of the GaN layer was evaluated by an etch pit method. The threading dislocation density can be expressed as a hexagonal etch pit density. An InGaN layer is grown on the GaN layer, and the InGaN etch pit density of InGaN on the buffer layer and InGaN on the insulating film mask (on ELO). The ratio was determined. The results are shown in Table 1.
The hexagonal etch pit density is formed on the surface of the InGaN layer by immersing the group III nitride semiconductor substrate on which the InGaN layer is grown in an etching solution of phosphoric acid: sulfuric acid = 1: 3 (temperature: 250 ° C.) for 10 minutes. The etch pit density was obtained by measuring with a scanning electron microscope. Regarding the ratio of threading dislocation density, the InGaN on the buffer layer and the InGaN on the insulating film were observed with a scanning electron microscope, and the confirmed hexagonal etch pits were regarded as threading dislocations. The ratio of dislocation density was used.

Example 2
Other than using a glass substrate instead of a sapphire substrate and using a target made of an oxide sintered body of gallium and tin having a composition of Ga ₂ O ₃ : SnO ₂ = 90: 10 (atomic ratio) for forming an insulating film Manufactured and evaluated a group III nitride semiconductor growth template and a group III nitride semiconductor substrate in the same manner as in Example 1. The results are shown in Table 1.

Example 3
A glass substrate is used instead of a sapphire substrate, TiN is used for forming the first buffer layer, and gallium having a composition of Ga ₂ O ₃ : In ₂ O ₃ = 60: 40 (atomic ratio) is used for forming the insulating film; A group III nitride semiconductor growth template and a group III nitride semiconductor substrate were produced and evaluated in the same manner as in Example 1 except that a target made of an indium oxide sintered body was used. The results are shown in Table 1.

Example 4
A polycrystalline alumina substrate is used instead of the sapphire substrate, the first buffer layer is not formed, and the insulating film is formed of gallium and tin having a composition of Ga ₂ O ₃ : SnO ₂ = 90: 10 (atomic ratio). A group III nitride semiconductor growth template and group III nitride semiconductor substrate and a group III nitride semiconductor substrate were manufactured and evaluated in the same manner as in Example 1 except that a target made of an oxide sintered body was used. The results are shown in Table 1.

Example 5
A group III nitride semiconductor growth template and the same as in Example 1 except that a glass substrate is used instead of the sapphire substrate, the first buffer layer is not formed, and LaNiO ₃ is used to form the second buffer layer. A group III nitride semiconductor substrate was manufactured and evaluated. The results are shown in Table 1.

Comparative Example 1
A group III nitride semiconductor growth template and a group III nitride semiconductor substrate were produced in the same manner as in Example 1 except that the first buffer layer was not formed and a target made of SiO ₂ was used to form the insulating film, evaluated. The results are shown in Table 1.

  As can be seen from the results in Table 1, in Comparative Example 1, the ratio of etch pits is 130, indicating that the defect density of the GaN layer is high.

1 Group III nitride semiconductor growth template 2 Group III nitride semiconductor substrate 10 Insulating film 12 Opening 20 Support substrate 30 First buffer layer 40 Second buffer layer 50 Group III nitride semiconductor

Claims (8)

A group III nitride semiconductor growth template comprising a laminated body including a support substrate and an insulating film which is a mask pattern having a plurality of openings in this order,
A group III nitride semiconductor growth template, wherein the insulating film contains Ga ₂ O ₃ as a main component. The group III nitride semiconductor growth template according to claim 1, wherein the insulating film is made of one or more selected from SnO ₂ and In ₂ O ₃ and Ga ₂ O ₃ . Including a buffer layer between the support substrate and the insulating film;
The buffer layer is made of low-temperature grown GaN, low-temperature grown AlN, Ti, TiN, Al ₂ O ₃ , 6H—SiC, LiAlO ₂ , LiGaO ₂ , ZnO, (LaAlO ₃ ) 0.3 − (SrAl _0.5 Ta _{0. The} group III nitride according to claim 1, comprising ₅ O ₃ ) 0.7, MnAl ₂ O ₄ , LiNbO ₃ , LaNiO ₃ , ScMgAlO ₄ , LiTaO ₃ , NdGaO ₃ , graphene, corundum ITO, or corundum ITZO. Template for semiconductor growth.   The group III nitride semiconductor growth template according to claim 3, wherein the buffer layer is exposed from the opening, and the buffer layer is made of the low-temperature grown GaN.   The group III nitride semiconductor growth template according to any one of claims 1 to 4, wherein the support substrate is a glass substrate.   A group III nitride semiconductor substrate having a group III nitride semiconductor on the insulating film of the group III nitride semiconductor growth template according to claim 1.   The group III nitride semiconductor substrate according to claim 6, wherein the group III nitride semiconductor is made of GaN, AlN, AlGaN, or InGaN. The group III nitride semiconductor is formed by filling an opening of a mask pattern of the insulating film,
When the crystal dislocation density of the group III nitride semiconductor on the opening is A and the crystal dislocation density of the group III nitride semiconductor on the mask pattern is B, 1 ≦ B / A ≦ 100 is satisfied. The group III nitride semiconductor substrate according to claim 7.