JP2016058512A - Epitaxial layer-deposited gallium nitride film composite substrate and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an epitaxial layer-deposited GaN film composite substrate including an AlGaN epitaxial layer as an epitaxial layer less in occurrence of crack; and a method for manufacturing such a composite substrate.SOLUTION: An epitaxial layer-deposited GaN film composite substrate 2 comprises: a GaN film composite substrate 1 arranged by putting together a support substrate 11 and a GaN film 13; and an InGaN epitaxial layer 22 (0<y<1) and an AlGaN epitaxial layer 24 (0<x<1) which are arranged in turn on the side of the GaN film 13 of the GaN film composite substrate 1. An Al composition ratio x of the AlGaN epitaxial layer 24, and a thickness tμm satisfy the relation given by the following formula (1): x×t≥0.028.SELECTED DRAWING: Figure 1

Description

The present invention relates to an epitaxial layer-attached GaN film composite substrate including an Al _x Ga _1-x N epilayer and a method for manufacturing the same.

  Semiconductor devices using Group III nitride semiconductors are formed by various methods. One method is a method of epitaxially growing at least one group III nitride layer on a group III nitride substrate. However, in this method, since the group III nitride substrate is very expensive, the resulting semiconductor device is also very expensive.

  Therefore, by using a composite substrate in which a group III nitride film is arranged on a support substrate having a different chemical composition from the group III nitride, at least one group III nitride is formed on the group III nitride film of the composite substrate. A method of epitaxially growing the layer is preferably used.

  For example, Japanese Unexamined Patent Application Publication No. 2010-182936 (Patent Document 1) includes a composite substrate including a support substrate, a nitride semiconductor layer, and a bonding layer formed between the support substrate and the nitride semiconductor layer. An epitaxial substrate comprising an epitaxial layer provided on a nitride semiconductor layer of a composite substrate is disclosed.

  Japanese Patent Laying-Open No. 2012-230969 (Patent Document 2) discloses that a support substrate having a thermal expansion coefficient of 0.8 to 1.2 by using an ion implantation separation method, and a support substrate A composite substrate including a GaN layer bonded to the substrate, a step of growing at least one GaN-based semiconductor layer on the GaN layer of the composite substrate, and removing the composite substrate by dissolving the support substrate And a method for manufacturing a GaN-based semiconductor device.

Japanese Patent Laying-Open No. 2003-060212 (Patent Document 3) is a Schottky barrier diode using a nitride-based compound semiconductor, which is made of silicon containing impurities or a silicon compound and has a low resistivity. A buffer layer disposed on one main surface of the substrate, a nitride compound semiconductor region disposed on the buffer layer, and a first electrode in Schottky barrier contact with a surface of the semiconductor region , and a second electrode which is in ohmic contact with the other main surface of the substrate, the buffer layer, the chemical formula _{Al x M y Ga 1-xy} N ( here, M is, in a (indium) B (boron And at least one element selected from the group consisting of a material represented by the following formula: 0 <x ≦ 1, 0 ≦ y <1, and x + y ≦ 1 Al _a M _b Ga _1-ab N (where M is at least one element selected from In (indium) and B (boron)), and a and b are 0 ≦ a ≦ 1, 0 ≦ b <1, Disclosed is a Schottky barrier diode comprising a composite layer with a second layer comprising a material represented by (a value satisfying a + b ≦ 1) and a method for producing the same.

JP 2010-182936 A JP 2012-230969 A JP 2003-060212 A

In JP 2010-182936 A (Patent Document 1) and JP 2012-230969 A (Patent Document 2), an Al _x Ga _1-x N layer (group III nitride layer) is formed on a GaN film of a composite substrate ( When 0 <x <1) was grown, there was a problem that cracks occurred in the Al _x Ga _1-x N layer.

Further, JP 2003-060212 (Patent Document 3), when the supporting substrate made of silicon or silicon compound, a made of a material represented by the chemical formula _{Al x M y Ga 1-xy} N on the support substrate And forming a nitride compound semiconductor by interposing a composite layer of a first layer and a second layer made of a material represented by the chemical formula Al _{a Mb} Ga _1-ab N. It merely suppresses the strain generated by the difference in thermal expansion coefficient with the compound semiconductor.

Therefore, in order to solve the above-mentioned problems and to manufacture a high-quality semiconductor device, an epitaxial layer-attached GaN film composite substrate including an Al _x Ga _1-x N epilayer free from cracks as an epilayer and its An object is to provide a manufacturing method.

An epilayer-attached GaN film composite substrate according to an aspect of the present invention includes a GaN film composite substrate obtained by bonding a support substrate and a GaN film, and an In _y Ga ₁₋ disposed in this order from the GaN film side of the GaN film composite substrate. _y N epilayer (0 <y <1) and Al _x Ga _1-x N epilayer (0 <x <1),
The Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer are expressed by the formula (1)
x × t _x ≧ 0.028 (1)
Satisfy the relationship.

The manufacturing method of the epilayer-attached GaN film composite substrate according to another aspect of the present invention includes a step of preparing a GaN film composite substrate in which a support substrate and a GaN film are bonded together, and a GaN film composite substrate on the GaN film side. At least an In _y Ga _1-y N epilayer (0 <y <1) and an Al _x Ga _1-x N epilayer (0 <x <1) are formed in this order to form a GaN film composite substrate with an epilayer. And comprising the steps of:
The Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer are expressed by the formula (1)
x × t _x ≧ 0.028 (1)
Satisfy the relationship.

According to the above, it is possible to provide an epilayer-attached GaN film composite substrate including an Al _x Ga _1-x N epilayer free from cracks as an epilayer and a method for manufacturing the same.

It is a schematic sectional drawing which shows the 1st example of the GaN film | membrane composite substrate with an epi layer concerning a certain aspect of this invention. It is a schematic sectional drawing which shows the 2nd example of the GaN film | membrane composite substrate with an epi layer concerning a certain aspect of this invention. It is a schematic sectional drawing which shows the 3rd example of the GaN film | membrane composite substrate with an epi layer concerning a certain aspect of this invention. It is a schematic sectional drawing which shows the 4th example of the GaN film | membrane composite substrate with an epi layer concerning a certain aspect of this invention. It is a schematic sectional drawing which shows the 5th example of the GaN film | membrane composite substrate with an epi layer concerning a certain aspect of this invention. It is a schematic sectional drawing which shows a certain example of the GaN film | membrane composite substrate with an epi layer outside this invention. It is a schematic sectional drawing which shows another example of the GaN film | membrane composite substrate with an epi layer outside this invention. It is a schematic sectional drawing which shows another example of the GaN film | membrane composite substrate with an epi layer outside this invention. It is a schematic sectional drawing which shows the process of preparing the GaN film composite substrate in the manufacturing method of the GaN film composite substrate with an epi layer concerning another aspect of this invention. Is a graph showing the relationship between the Al composition ratio and the critical thickness of the Al _x Ga _1-x N epitaxial layer in the GaN film composite substrate with epitaxial layer according to an aspect of the present invention.

<Description of Embodiment of the Present Invention>
An epilayer-attached GaN film composite substrate according to an embodiment of the present invention includes a GaN film composite substrate obtained by bonding a support substrate and a GaN film, and In _y Ga ₁ arranged in order from the GaN film side of the GaN film composite substrate. _-y N epilayer (0 <y <1) and Al _x Ga _1-x N epilayer (0 <x <1), Al composition ratio x and thickness of Al _x Ga _1-x N epilayer T _x μm is expressed by equation (1)
x × t _x ≧ 0.028 (1)
Satisfy the relationship.

In the GaN film composite substrate with an epi layer of this embodiment, the In _y Ga _1-y N epi layer and the Al _x Ga _1-x N epi layer are arranged in this order from the GaN film side of the GaN film composite substrate. Therefore, the tensile stress applied to the Al _x Ga _1-x N epilayer when forming the Al _x Ga _1-x N epilayer can be reduced by the compressive stress generated in the In _y Ga _1-y N epilayer. Therefore, the generation of cracks in the Al _x Ga _1-x N epilayer can be suppressed. Accordingly, Al _x Ga _1-x N epitaxial layer without causing cracks _{to, Al x Ga 1-x N} Al composition ratio of the epitaxial layer x and thickness t _x [mu] m is an expression (1) x × t The relationship _x ≧ 0.028 is satisfied. That is, the epilayer-attached GaN film composite substrate of the present embodiment includes an Al _x Ga _1-x N epilayer having a thickness of (0.028 / x) μm or more at which cracks do not occur.

In the GaN film composite substrate with an epi layer of the present embodiment, the In composition ratio y and the thickness t _y μm of the In _y Ga _1-y N epilayer are the same as the Al composition ratio x of the Al _x Ga _1-x N epilayer and Between thickness t _x μm, formula (2)
0.01 × x × t _x ≦ y × t _y ≦ 2 × x × t _x (2)
Can satisfy the relationship. _{Accordingly, Al x Ga 1-x N} In y Ga 1-y N epitaxial for generating a compressive stress which is suitable for reducing the Al _x Ga _1-x N epitaxial layer in accordance tensile stress during the formation of the epitaxial layer Since the layer is formed, the generation of cracks in the Al _x Ga _1-x N epilayer can be further suppressed.

The epitaxial layer-attached GaN film composite substrate of this embodiment can have a GaN film thickness t _f of 0.05 μm or more and 50 μm or less. Thus, according to the thickness t _f of the GaN film of GaN film composite substrate, the _{Al x Ga 1-x N Al} x Ga 1-x N epitaxial layer in accordance tensile stress during the formation of the epitaxial layer, an In _y it is possible to reduce the compressive stress generated in the Ga _1-y N epitaxial layer, it is possible to suppress occurrence of cracks in the Al _x Ga _1-x N epitaxial layer.

The epilayer-attached GaN film composite substrate of this embodiment can further include a GaN epilayer disposed between the GaN film and the In _y Ga _1-y N epilayer. Thus, Al _x with Ga _1-x N cracks Al _x Ga _1-x N epitaxial layer during formation of the epitaxial layer can be inhibited from occurring, In _y Ga _1-y N epitaxial layer and Al _x Ga The morphology and crystal quality of the _1-x N epilayer can be enhanced.

In addition to the GaN epilayer disposed between the GaN film and the In _y Ga _1-y N epilayer, the epilayer _- attached GaN film composite substrate according to the present embodiment is provided between the GaN film and the GaN epilayer. The Al _z Ga _1-z N epilayer (0 <z <1) is further included, and the Al composition ratio z and the thickness t _z μm of the Al _z Ga _1-z N epilayer are expressed by the formula (3)
z × t _z <0.028 (3)
Can satisfy the relationship. Thus, while suppressing occurrence of cracks in the Al _x Ga _1-x N epitaxial layer during formation of the Al _x Ga _1-x N epitaxial layer, GaN epi-layer, In _y Ga _1-y N epitaxial layer And the morphology and crystal quality of the Al _x Ga _1-x N epilayer can be enhanced.

The epilayer-attached GaN film composite substrate of the present embodiment can further include a GaN epilayer disposed between the In _y Ga _1-y N epilayer and the Al _x Ga _1-x N epilayer. Thus, while suppressing occurrence of cracks in the Al _x Ga _1-x N epitaxial layer during formation of the Al _x Ga _1-x N epitaxial layer, Al _x Ga _1-x N epitaxial layer of morphology and crystallinity Quality can be improved.

In addition to the GaN epilayer disposed between the In _y Ga _1-y N epilayer and the Al _x Ga _1-x N epilayer, the epilayer-attached GaN film composite substrate of the present embodiment includes: An Al _z Ga _1-z N epilayer (0 <z <1) disposed between the In _y Ga _1-y N epilayer and an Al composition ratio of the Al _z Ga _1-z N epilayer z and thickness t _z μm are given by equation (3)
z × t _z <0.028 (3)
Can satisfy the relationship. Thus, while suppressing occurrence of cracks in the Al _x Ga _1-x N epitaxial layer during formation of the Al _x Ga _1-x N epitaxial layer, In _y Ga _1-y N epitaxial layer, GaN epi-layer And the morphology and crystal quality of the Al _x Ga _1-x N epilayer can be enhanced.

An epilayer-attached GaN film composite substrate manufacturing method according to another embodiment of the present invention includes a step of preparing a GaN film composite substrate in which a support substrate and a GaN film are bonded together, and a GaN film composite substrate on the GaN film side. Forming an GaN film composite substrate with an epi layer by forming at least an In _y Ga _1-y N epilayer (0 <y <1) and an Al _x Ga _1-x N epilayer (0 <x <1) in this order. And an Al composition ratio x and a thickness t _x μm of the Al _x Ga _1-x N epilayer are expressed by the formula (1):
x × t _x ≧ 0.028 (1)
Satisfy the relationship.

In the manufacturing method of the epitaxial layer-attached GaN film composite substrate of this embodiment, the In _y Ga _{1 -y} N epi layer and the Al _x Ga _{1 -x} N epi layer are formed in this order from the GaN film side of the GaN film composite substrate. Therefore, the tensile stress applied to the Al _x Ga _1-x N epi layer when forming the Al _x Ga _1-x N epi layer is reduced by the compressive stress generated in the In _y Ga _1-y N epi layer. Therefore, the generation of cracks in the Al _x Ga _1-x N epilayer can be suppressed. Accordingly, Al _x Ga _1-x N epitaxial layer without causing cracks _{to, Al x Ga 1-x N} Al composition ratio of the epitaxial layer x and thickness t _x [mu] m is an expression (1) x × t The relationship _x ≧ 0.028 is satisfied. That is, the manufacturing method of the epilayer-attached GaN film composite substrate according to the present embodiment has an epilayer including an Al _x Ga _1-x N epilayer having a thickness of (0.028 / x) μm or more without occurrence of cracks. A GaN film composite substrate can be manufactured.

In the manufacturing method of the epitaxial layer-attached GaN film composite substrate of the present embodiment, the In composition ratio y and the thickness t _y μm of the In _y Ga _1-y N epilayer are the same as the Al composition of the Al _x Ga _1-x N epilayer. Between the ratio x and the thickness t _x μm, the formula (2)
0.01 × x × t _x ≦ y × t _y ≦ 2 × x × t _x (2)
Can satisfy the relationship. _{Accordingly, Al x Ga 1-x N} In y Ga 1-y N epitaxial for generating a compressive stress which is suitable for reducing the Al _x Ga _1-x N epitaxial layer in accordance tensile stress during the formation of the epitaxial layer Since the layer can be formed, the epitaxial layer-attached GaN film composite substrate including the Al _x Ga _1-x N epilayer free of cracks can be more reliably manufactured.

<Details of Embodiment of the Present Invention>
[Embodiment 1: GaN film composite substrate with epi layer]
1 to 5, the epilayer-attached GaN film composite substrate 2 of this embodiment includes a GaN film composite substrate 1 in which a support substrate 11 and a GaN film 13 are bonded together, and GaN of the GaN film composite substrate 1. In _y Ga _1-y N epilayer 22 (0 <y <1) and Al _x Ga _1-x N epilayer 24 (0 <x <1) arranged in this order from the film 13 side, Al _x The Al composition ratio x and the thickness t _x μm of the Ga _1-x N epilayer 24 are expressed by the formula (1)
x × t _x ≧ 0.028 (1)
Satisfy the relationship.

In the GaN film composite substrate 2 with an epi layer of this embodiment, the In _y Ga _{1 -y} N epi layer 22 and the Al _x Ga _{1 -x} N epi layer 24 are arranged in this order from the GaN film 13 side of the GaN film composite substrate 1. since it was arranged, the Al _x Ga _1-x N tensile according to Al _x Ga _1-x N epitaxial layer 24 stress during formation of the epitaxial layer 24, occurs in in _y Ga _1-y N epitaxial layer 22 Therefore, the generation of cracks in the Al _x Ga _1-x N epilayer 24 can be suppressed. Thus, Al _x Ga _1-x N epitaxial layer 24 without causing cracks, Al _x Ga _1-x N epitaxial layer 24 of Al composition x and the thickness t _x [mu] m is an expression (1) x The relationship of xt _x ≧ 0.028 is satisfied. That is, the epitaxial layer-attached GaN film composite substrate 2 of the present embodiment includes the Al _x Ga _1-x N epilayer 24 having a thickness of (0.028 / x) μm or more where cracks do not occur.

  Here, the “epi layer” refers to a layer formed by epitaxial growth on the GaN film 13 of the GaN film composite substrate 1 or on the underlying “epi layer” formed thereon.

Referring to FIG. 6, when an Al _x Ga _1-x N epilayer 24 (0 <x <1) is formed on the GaN film 13 of the GaN film composite substrate 1, an Al _x Ga _1-x N crystal is formed. Since the lattice constant of (0 <x <1) is smaller than that of GaN crystal, tensile stress is applied to the Al _x Ga _1-x N epilayer 24. Therefore, cracks are generated in the Al _x Ga _1-x N epitaxial layer 24 when the Al _x Ga _1-x N epitaxial layer 24 Al composition ratio x and thickness t _x [mu] m and is x × t _x <0.028 However, the present inventors have found that cracks occur in the Al _x Ga _1-x N epilayer 24 when x × t _x ≧ 0.028.

Therefore, the present inventors have determined that the lattice constant of In _y Ga _1-y N crystal (0 <y <1) is the lattice constant of GaN crystal and that of Al _x Ga _1-x N crystal (0 <x <1). Focusing on the larger, as shown in FIGS. 1 to 5, from the GaN film 13 side of the GaN film composite substrate 1, an In _y Ga _{1 -y} N epilayer 22 and an Al _x Ga _{1 -x} N epilayer are formed. by placing the 24 in this order, Al _x Ga _1-x N tensile according to Al _x Ga _1-x N epitaxial layer 24 stress during formation of the epitaxial layer _{24, in y Ga 1-y} N epitaxial layer 22 It was succeeded in reducing the occurrence of cracks in the Al _x Ga _1-x N epilayer 24 by reducing the compressive stress generated in the above.

With reference to FIGS. 1 to 5, the GaN film composite substrate 2 with an epi layer according to the present embodiment has an In composition ratio y and a thickness t _y μm of an In _y Ga _1-y N epilayer 22 of Al _x Ga. _Between the Al composition ratio x and the thickness t _x μm of the _1-x N epilayer 24, the formula (2)
0.01 × x × t _x ≦ y × t _y ≦ 2 × x × t _x (2)
It is preferable to satisfy the relationship. The In composition ratio y and the thickness t _y μm of the In _y Ga _1-y N epilayer 22 are expressed by the equation (2) between the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer 24. ) 0.01 × x × t _x ≦ y × t _y ≦ 2 × x × t _x , the Al _x Ga _1-x N epilayer 24 is formed during the formation of the Al _x Ga _{1− Since the} In _y Ga _1-y N epi layer 22 having an In composition ratio y and a thickness t _y μm that generates a compressive stress suitable for reducing the tensile stress applied to the _x N epi layer 24 is formed, The generation of cracks in the Al _x Ga _1-x N epilayer 24 can be further suppressed.

1 to 5, in the GaN film composite substrate 2 with an epi layer according to this embodiment, the thickness t _f of the GaN film 13 is preferably 0.05 μm or more and 50 μm or less. If the thickness t _f of the GaN film 13 of the GaN film composite substrate is 0.05 μm or more and 50 μm or less, the Al _x Ga _1-x N epilayer 24 is formed according to the thickness t _f of the GaN film 13. Since the tensile stress applied to the Al _x Ga _1-x N epi layer 24 can be reduced by the compressive stress generated in the In _y Ga _1-y N epi layer 22, the Al _x Ga _1-x N epi layer The occurrence of cracks in 24 can be suppressed.

  The GaN film composite substrate 1 in the epilayer-attached GaN film composite substrate 2 of this embodiment is a composite substrate in which a support substrate 11 and a GaN film 13 are bonded together. The GaN film composite substrate 1 preferably further includes a bonding film 12 interposed between the support substrate 11 and the GaN film 13 from the viewpoint of increasing the bonding strength by bonding the support substrate 11 and the GaN film 13 together.

The support substrate 11 of the GaN film composite substrate 1 is not particularly limited, but from the viewpoint of forming a high quality epi layer on the GaN film 13 of the GaN film composite substrate 1, the linear thermal expansion coefficient of the support substrate 11 is a GaN film. The linear thermal expansion coefficient of 13 is preferably 0.8 times or more and 1.2 times or less, more preferably 0.9 times or more and 1.1 times or less. For example, a mullite substrate (3Al ₂ O ₃ .2SiO _{2 to} 2Al ₂ O ₃ · SiO ₂ ), yttria stabilized zirconia-mullite substrate, molybdenum substrate and the like are preferable. The thickness of the support substrate 11 is not particularly limited as long as it can support the GaN film 13, and is, for example, 250 μm or more and 2500 μm or less.

  The thickness of the GaN film 13 of the GaN film composite substrate 1 is not particularly limited, but from the viewpoint of forming a high quality epi layer on the GaN film composite substrate 1 and reducing the cost of the GaN film composite substrate 1, the thickness is 50 nm or more and less than 10 μm. preferable.

The bonding film 12 that can be included in the GaN film composite substrate 1 is not particularly limited, but an SiO ₂ film, an SiN _x film, or the like is preferable from the viewpoint of increasing the bonding strength by bonding the support substrate 11 and the GaN film 13 together. .

(First example)
Referring to FIG. 1, a first example of the epilayer-attached GaN film composite substrate 2 of the present embodiment includes a GaN film composite substrate 1 in which a support substrate 11 and a GaN film 13 are bonded together, and a GaN film composite substrate 1. An In _y Ga _{1 -y} N epilayer 22 and an Al _x Ga _{1 -x} N epilayer 24 arranged in this order from the GaN film 13 side. In the first example GaN film composite substrate 2 with an epi layer, for example, an In _y Ga _{1 -y} N epi layer 22 is disposed on the GaN film 13 of the GaN film composite substrate 1 and an In _y Ga _{1 -y} N epi layer is formed. An Al _x Ga _1-x N epilayer 24 is disposed on the substrate 22.

In the GaN film composite substrate 2 with the epi layer of the first example, the In _y Ga _{1 -y} N epi layer 22 and the Al _x Ga _{1 -x} N epi layer 24 are arranged in this order from the GaN film 13 side of the GaN film composite substrate 1. since it was arranged, the Al _x Ga _1-x N tensile according to Al _x Ga _1-x N epitaxial layer 24 stress during formation of the epitaxial layer 24, occurs in in _y Ga _1-y N epitaxial layer 22 Therefore, the generation of cracks in the Al _x Ga _1-x N epilayer 24 can be suppressed.

(Second example)
Referring to FIG. 2, a second example of the epitaxial layer with GaN film composite substrate 2 of the present embodiment, the epitaxial layer with GaN film composite substrate 2 of the first example shown in FIG. 1, the GaN film 13 and an In _y Ga Further included is a GaN epi layer 26 disposed between the _1-y N epi layer 22. That is, the GaN film composite substrate 2 with the epi layer of the second example is arranged in order from the GaN film composite substrate 1 in which the support substrate 11 and the GaN film 13 are bonded together, and the GaN film composite substrate 1 from the GaN film 13 side. A GaN epi layer 26, an In _y Ga _{1 -y} N epi layer 22, and an Al _x Ga _{1 -x} N epi layer 24. In the GaN film composite substrate 2 with the epi layer of the second example, for example, a GaN epi layer 26 is disposed on the GaN film 13 of the GaN film composite substrate 1, and an In _y Ga _1-y N epi layer is formed on the GaN epi layer 26. 22, and an Al _x Ga _1-x N epilayer 24 is disposed on the In _y Ga _1-y N epilayer 22.

The GaN film composite substrate 2 with the epi layer of the second example includes a GaN epi layer 26, an In _y Ga _{1 -y} N epi layer 22 and an Al _x Ga _{1 -x} N epi layer from the GaN film 13 side of the GaN film composite substrate 1. since 24 is disposed in this order, it is possible to reduce the Al _x Ga _1-x N tensile stress exerted on the Al _x Ga _1-x N epitaxial layer 24 during the formation of the epitaxial layer 24, Al _x Ga _The occurrence of cracks in the _1-x N epilayer 24 can be suppressed. Further, the morphology and crystal quality of the In _y Ga _1-y N epilayer 22 and the Al _x Ga _1-x N epilayer 24 can be improved.

(Third example)
Referring to FIG. 3, the third example of the epilayer-attached GaN film composite substrate 2 of the present embodiment is the same as the GaN film composite substrate 2 with the epilayer of the second example shown in FIG. Al _z Ga _1-z N epi layer 28 which is arranged between the 26 (0 <z <1) further comprises, Al _z Ga _1-z N Al composition ratio z and the thickness t _z epilayer 28 μm is the formula (3)
z × t _z <0.028 (3)
Satisfy the relationship. That is, the GaN film composite substrate 2 with the epi layer of the third example is arranged in order from the GaN film composite substrate 1 in which the support substrate 11 and the GaN film 13 are bonded together, and the GaN film 13 side of the GaN film composite substrate 1. An Al _z Ga _{1 -z} N epi layer 28, a GaN epi layer 26, an In _y Ga _{1 -y} N epi layer 22, and an Al _x Ga _{1 -x} N epi layer 24. In the GaN film composite substrate 2 with the epi layer of the third example, for example, an Al _z Ga _{1 -z} N epi layer 28 is disposed on the GaN film 13 of the GaN film composite substrate 1, and an Al _z Ga _{1 -z} N epi layer is formed. A GaN epi layer 26 is disposed on the layer 28, an In _y Ga _{1 -y} N epi layer 22 is disposed on the GaN epi layer 26, and an Al _x Ga _{1 -x} N layer is disposed on the In _y Ga _{1 -y} N epi layer 22. An epi layer 24 is disposed.

The GaN film composite substrate 2 with the epi layer of the third example includes an Al _z Ga _{1 -z} N epi layer 28, a GaN epi layer 26, an In _y Ga _{1 -y} N epi layer from the GaN film 13 side of the GaN film composite substrate 1. 22 and Al _x Ga _1-x N for epi layer 24 are disposed in this order, Al _x Ga _1-x N in forming the epitaxial layer 24 according to the Al _x Ga _1-x N epitaxial layer 24 tensile stress Therefore, the generation of cracks in the Al _x Ga _1-x N epilayer 24 can be suppressed. Further, the morphology and crystal quality of the GaN epi layer 26, the In _y Ga _{1 -y} N epi layer 22 and the Al _x Ga _{1 -x} N epi layer 24 can be improved. Here, the Al composition ratio z and the thickness t _z μm of the Al _z Ga _1-z N epilayer 28 must satisfy the relationship of z × t _z <0.028 in the formula (3). the _z Ga _1-z Al in the formation of the N epitaxial layer 28 _z Ga _1-z N epitaxial layer 28 is because cracks can be suppressed.

(Fourth example)
Referring to FIG 4, a fourth example of the epitaxial layer with GaN film composite substrate 2 of the present embodiment, the epitaxial layer with GaN film composite substrate 2 of the first example shown in FIG. _{1, In y Ga 1-y} N Further included is a GaN epi layer 26 disposed between the epi layer 22 and the Al _x Ga _1-x N epi layer 24. That is, the GaN film composite substrate 2 with the epi layer of the fourth example is arranged in order from the GaN film composite substrate 1 in which the support substrate 11 and the GaN film 13 are bonded together, and the GaN film composite substrate 1 from the GaN film 13 side. In _y Ga _1-y N epilayer 22, GaN epilayer 26 and Al _x Ga _1-x N epilayer 24. In the GaN film composite substrate 2 with the epi layer of the fourth example, for example, an In _y Ga _{1 -y} N epi layer 22 is disposed on the GaN film 13 of the GaN film composite substrate 1 and an In _y Ga _{1 -y} N epi layer is formed. A GaN epi layer 26 is disposed on the substrate 22, and an Al _x Ga _1-x N epi layer 24 is disposed on the GaN epi layer 26.

The GaN film composite substrate 2 with the epi layer of the fourth example includes an In _y Ga _{1 -y} N epi layer 22, a GaN epi layer 26, and an Al _x Ga _{1 -x} N epi layer from the GaN film 13 side of the GaN film composite substrate 1. since 24 is disposed in this order, it is possible to reduce the Al _x Ga _1-x N tensile stress exerted on the Al _x Ga _1-x N epitaxial layer 24 during the formation of the epitaxial layer 24, Al _x Ga _The occurrence of cracks in the _1-x N epilayer 24 can be suppressed. In addition, the morphology and crystal quality of the Al _x Ga _1-x N epilayer 24 can be improved.

(Fifth example)
Referring to FIG. 5, the fifth example of the epitaxial layer with GaN film composite substrate 2 of the present embodiment, the epitaxial layer with GaN film composite substrate 2 of the fourth example shown in FIG. 4, the GaN film 13 and an In _y Ga An Al _z Ga _1-z N epi layer 28 (0 <z <1) arranged between the _1-y N epi layer 22 and an Al composition ratio of the Al _z Ga _1-z N epi layer 28 z and thickness t _z μm are given by equation (3)
z × t _z <0.028 (3)
Satisfy the relationship. That is, the GaN film composite substrate 2 with the epi layer of the fifth example is disposed in order from the GaN film composite substrate 1 in which the support substrate 11 and the GaN film 13 are bonded together, and the GaN film 13 side of the GaN film composite substrate 1. An Al _z Ga _{1 -z} N epi layer 28, an In _y Ga _{1 -y} N epi layer 22, a GaN epi layer 26, and an Al _x Ga _{1 -x} N epi layer 24. In the GaN film composite substrate 2 with the epi layer of the fourth example, for example, an Al _z Ga _{1 -z} N epi layer 28 is disposed on the GaN film 13 of the GaN film composite substrate 1, and an Al _z Ga _{1 -z} N epi layer is formed. An In _y Ga _{1 -y} N epilayer 22 is disposed on the layer 28, a GaN epilayer 26 is disposed on the In _y Ga _{1 -y} N epilayer 22, and an Al _x Ga _{1 -x} N layer is disposed on the GaN epilayer 26. An epi layer 24 is disposed.

The GaN film composite substrate 2 with an epi layer of the fifth example includes an Al _z Ga _{1 -z} N epi layer 28, an In _y Ga _{1 -y} N epi layer 22, and a GaN epi layer from the GaN film 13 side of the GaN film composite substrate 1. 26 and Al _x Ga _1-x N for epi layer 24 are disposed in this order, Al _x Ga _1-x N in forming the epitaxial layer 24 according to the Al _x Ga _1-x N epitaxial layer 24 tensile stress Therefore, the generation of cracks in the Al _x Ga _1-x N epilayer 24 can be suppressed. In addition, the morphology and crystal quality of the In _y Ga _{1 -y} N epilayer 22, the GaN epilayer 26 and the Al _x Ga _{1 -x} N epilayer 24 can be improved. Here, the Al composition ratio z and the thickness t _z μm of the Al _z Ga _1-z N epilayer 28 must satisfy the relationship of z × t _z <0.028 in the formula (3). the _z Ga _1-z Al in the formation of the N epitaxial layer 28 _z Ga _1-z N epitaxial layer 28 is because cracks can be suppressed.

[Embodiment 2: Manufacturing method of GaN film composite substrate with epi layer]
With reference to FIGS. 1 to 5 and FIG. 9, the manufacturing method of the epitaxial layer-attached GaN film composite substrate 2 of the present embodiment is not particularly limited. From the viewpoint of manufacturing, a step of preparing the GaN film composite substrate 1 in which the support substrate 11 and the GaN film 13 are bonded together (FIG. 9), and at least In _y Ga _{1 -y} on the GaN film side of the GaN film composite substrate 1. Forming an epilayer-attached GaN film composite substrate 2 by forming an N epilayer 22 (0 <y <1) and an Al _x Ga _1-x N epilayer 24 (0 <x <1) in this order; The Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer 24 are given by the formula (1)
x × t _x ≧ 0.028 (1)
Satisfy the relationship.

The manufacturing method of the epilayer-attached GaN film composite substrate 2 of the present embodiment includes an In _y Ga _1-y N epilayer 22 and an Al _x Ga _1-x N epilayer 24 from the GaN 13 film side of the GaN film composite substrate 1. Since the layers are formed in this order, tensile stress applied to the Al _x Ga _1-x N epilayer 24 during the formation of the Al _x Ga _1-x N epilayer 24 is generated in the In _y Ga _1-y N epilayer 22. Therefore, the generation of cracks in the Al _x Ga _1-x N epilayer 24 can be suppressed. Thus, Al _x Ga _1-x N epitaxial layer 24 without causing cracks, Al _x Ga _1-x N epitaxial layer 24 of Al composition x and the thickness t _x [mu] m is an expression (1) x The relationship of xt _x ≧ 0.028 is satisfied. That is, the manufacturing method of the epitaxial layer-attached GaN film composite substrate 2 of the present embodiment includes an epitaxial layer including an Al _x Ga _1-x N epi layer 24 having a thickness of (0.028 / x) μm or more without cracks. The layered GaN film composite substrate 2 can be manufactured.

In the manufacturing method of the epitaxial layer-attached GaN film composite substrate 2 of the present embodiment, the In composition ratio y and the thickness t _y μm of the In _y Ga _1-y N epilayer 22 are such that the Al _x Ga _1-x N epilayer 24 Between the Al composition ratio x and the thickness t _x μm of the formula (2)
0.01 × x × t _x ≦ y × t _y ≦ 2 × x × t _x (2)
It is preferable to satisfy the relationship. The In composition ratio y and the thickness t _y μm of the In _y Ga _1-y N epilayer 22 are expressed by the equation (2) between the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer 24. ) 0.01 × x × t _x ≦ y × t _y ≦ 2 × x × t _x , the Al _x Ga _1-x N epilayer 24 is formed during the formation of the Al _x Ga _{1− Since the} In _y Ga _{1 -y} N epi layer 22 that generates compressive stress suitable for reducing the tensile stress applied to the _x N epi layer 24 can be formed, the Al _x Ga _{1 -x} free from cracks can be formed. The epilayer-attached GaN film composite substrate 2 including the N epilayer 24 can be more reliably manufactured.

(Process to prepare GaN film composite substrate)
Referring to FIG. 9, the manufacturing method of the epilayer-attached GaN film composite substrate 2 of the present embodiment includes a step of preparing a GaN film composite substrate 1 in which a support substrate 11 and a GaN film 13 are bonded together. The step of preparing the GaN film composite substrate 1 is not particularly limited, but from the viewpoint of efficiently preparing the GaN film composite substrate 1 including the high-quality GaN film 13, the bonding film 12a is formed on the main surface 11m of the support substrate 11. And forming a bonding film 12b on the main surface 13n of the GaN film donor substrate 13D, and forming ions at a predetermined depth from the main surface 13n of the GaN film donor substrate 13D. A sub-process for forming the implantation region 13i (FIG. 9B) and a sub-process for bonding the bonding film 12a formed on the support substrate 11 and the bonding film 12b formed on the GaN film donor substrate 13D (FIG. C)) and the GaN film donor substrate 13D are separated by the ion implantation region 13i, thereby supporting the support substrate 11, the bonding film 12 disposed on the support substrate 11, and the G disposed on the bonding film 12. And N film 13, the sub-step of forming a GaN film composite substrate 1 comprising (FIG. 9 (D)), it will be preferable to include.

Referring to FIG. 9A, as described above, the support substrate 11 of the GaN film composite substrate 1 has a linear expansion coefficient of the support substrate 11 that is 0.8 times or more the linear expansion coefficient of the GaN film 13. It is preferably 2 times or less, more preferably 0.9 times or more and 1.1 times or less, for example, mullite substrate (3Al ₂ O ₃ .2SiO _{2 to} 2Al ₂ O ₃ .SiO ₂ ), yttria stable A zirconia mullite substrate, a molybdenum substrate, or the like is preferable. Referring to FIG. 9B, the GaN film donor substrate 13D is a GaN substrate for supplying the GaN film 13. The method for forming the GaN film donor substrate 13D is not particularly limited. From the viewpoint of obtaining a high quality GaN film donor substrate 13D, an HVPE (hydride vapor phase) is formed on a base substrate such as a sapphire substrate, a GaAs substrate, or a GaN substrate. (Growth) method, MOCVD (Metal Organic Chemical Vapor Deposition) method, MBE (Molecular Beam Growth) method, gas phase method such as sublimation method, liquid phase method such as high nitrogen pressure solution method, flux method and the like are preferable.

Referring to FIGS. 9A and 9B, the bonding films 12a, 12b, and 12 are films interposed to increase the bonding strength between the support substrate 11 and the GaN film 13, and increase the bonding strength. From the viewpoint, a SiO ₂ film, a SiN _x film, and the like are preferable. As a method of forming the bonding films 12a and 12b, a plasma CVD (chemical vapor deposition) method, a sputtering method, a vacuum evaporation method, and the like are preferable from the viewpoint of obtaining high-quality bonding films 12a and 12b.

  Referring to FIG. 9C, the method for bonding the bonding film 12a formed on the support substrate 11 and the bonding film 12b formed on the GaN film donor substrate 13D is not particularly limited, and the bonded surface is cleaned. Then, after bonding together, the temperature is raised to about 600 ° C. to 1200 ° C. for direct bonding, and after bonding surfaces are cleaned and activated with plasma, ions, etc., room temperature (for example, 25 ° C.) to low temperature of about 400 ° C. For example, a surface activation method in which bonding is performed with a metal is preferable. By bonding, the bonding film 12a and the bonding film 12b are integrated by bonding to form the bonding film 12, and the support substrate 11 and the GaN film donor substrate 13D are bonded with the bonding film 12 interposed.

  Referring to FIG. 9D, the method for separating the GaN film donor substrate 13D by the ion implantation region 13i is not particularly limited as long as it is a method for applying some energy to the ion implantation region 13i of the GaN film donor substrate 13D. At least one of a method of applying stress to the ion implantation region 13i, a method of applying heat, a method of irradiating light, and a method of applying ultrasonic waves is possible. In this way, the GaN film composite substrate 2 in which the support substrate 11 and the GaN film 13 are bonded together with the bonding film 12 interposed therebetween is obtained. The remaining GaN film donor substrate 13Dr from which the GaN film 13 is separated from the GaN film donor substrate 13D can be reused.

(Process of forming GaN film composite substrate with epi layer)
With reference to FIGS. 1 to 5, in the manufacturing method of the epitaxial layer-attached GaN film composite substrate 2 of this embodiment, next, at least In _y Ga _1-y N is formed on the GaN film composite substrate 1 side of the GaN film composite substrate 1. A step of forming the epitaxial layer-attached GaN film composite substrate 2 by forming the epi layer 22 (0 <y <1) and the Al _x Ga _1-x N epi layer 24 (0 <x <1) in this order is provided. Here, a GaN epi layer 26 can be further formed before the In _y Ga _{1 -y} N epi layer 22 is formed, and an Al _z Ga _{1 -z} N epi layer 28 is formed before the GaN epi layer 26 is further formed. (0 <z <1) can be further formed. Further, after the In _y Ga _{1 -y} N epi layer 22 is formed and before the Al _x Ga _{1 -x} N epi layer 24 is formed, a GaN epi layer 26 can be further formed, and the In _y Ga _{1 -y} is further formed. An Al _z Ga _{1 -z} N epi layer 28 can be further formed before the N epi layer 22 is formed. Specifically, the steps of forming the epilayer-attached GaN film composite substrate 2 of the first to fifth examples of the first embodiment are as follows.

(First example)
Referring to FIG. 1, in the step of forming the epitaxial layer-attached GaN film composite substrate 2 of the first example of Embodiment 1, at least In _y Ga _1-y N is formed on the GaN film 13 side of the GaN film composite substrate 1. An epi layer 22 (0 <y <1) and an Al _x Ga _1-x N epi layer 24 (0 <x <1) are formed in this order.

(Second example)
Referring to FIG. 2, in the step of forming the epilayer-attached GaN film composite substrate 2 of the second example of Embodiment 1, at least the GaN epilayer 26, In _y is formed on the GaN film 13 side of the GaN film composite substrate 1. A Ga _1-y N epi layer 22 (0 <y <1) and an Al _x Ga _1-x N epi layer 24 (0 <x <1) are formed in this order.

(Third example)
Referring to FIG. 3, in the step of forming the epitaxial layer-attached GaN film composite substrate 2 of the third example of Embodiment 1, at least Al _z Ga _{1 -z} N is formed on the GaN film 13 side of the GaN film composite substrate 1. Epi layer 28 (0 <z <1), GaN epi layer 26, In _y Ga _1-y N epi layer 22 (0 <y <1) and Al _x Ga _1-x N epi layer 24 (0 <x <1 ) In this order. Here, Al _z Ga _1-z N from the viewpoint of suppressing occurrence of cracks in the epitaxial layer _{28, Al z Ga 1-z} Al composition ratio of the N epitaxial layer 28 z and the thickness t _z [mu] m has the formula (3 ) Z × t _z <0.028.

(Fourth example)
Referring to FIG. 4, in the step of forming the epilayer-attached GaN film composite substrate 2 of the fourth example of Embodiment 1, at least In _y Ga _1-y N is formed on the GaN film 13 side of the GaN film composite substrate 1. An epi layer 22 (0 <y <1), a GaN epi layer 26 and an Al _x Ga _1-x N epi layer 24 (0 <x <1) are formed in this order.

(Fifth example)
Referring to FIG. 5, in the step of forming the epitaxial layer-attached GaN film composite substrate 2 of the fifth example of Embodiment 1, at least Al _z Ga _1-z N is formed on the GaN film 13 side of the GaN film composite substrate 1. Epi layer 28 (0 <z <1), In _y Ga _1-y N epi layer 22 (0 <y <1), GaN epi layer 26 and Al _x Ga _1-x N epi layer 24 (0 <x <1 ) In this order. Here, Al _z Ga _1-z N from the viewpoint of suppressing occurrence of cracks in the epitaxial layer _{28, Al z Ga 1-z} Al composition ratio of the N epitaxial layer 28 z and the thickness t _z [mu] m has the formula (3 ) Z × t _z <0.028.

(Example A1)
Example A1 is an example of the epitaxial layer-attached GaN film composite substrate of the third example of the first embodiment.

1. 3. Preparation of GaN Film Composite Substrate Referring to FIG. 3, a mullite substrate (thickness ratio of Al ₂ O ₃ and SiO ₂ of 3: 2) having a thickness of 350 μm, which is a support substrate 11, and a junction disposed thereon A GaN film composite substrate 1 having a diameter of 100 mm including a SiO ₂ film having a thickness of 0.5 μm as the film 12 and a GaN film 13 having a thickness of 0.2 μm disposed thereon was prepared.

  As shown in FIG. 9, the GaN film composite substrate 1 is bonded to a support substrate 11 and a GaN substrate, which is a GaN film donor substrate 13D in which an ion implantation region 13i is formed, with a bonding film 12 interposed therebetween. The GaN film donor substrate 13D was obtained by separating the GaN film donor substrate 13D into the GaN film 13 and the remaining GaN film donor substrate 13Dr in the ion implantation region 13i.

2. Formation of epilayer-attached GaN film composite substrate Referring to FIG. 3, an Al _z Ga having a thickness of 0.05 μm and an Al composition ratio z of 0.05 is formed on GaN film 13 of GaN film composite substrate 1 by MOCVD. _1-z N epi layer 28 (z × t _z = 0.0025), GaN epi layer 26 having a thickness of 4.5 μm, and In _y Ga ₁₋ having a thickness of 0.05 μm and an In composition ratio y of 0.07 _{The y} N epi layer 22 (y × t _y = 0.0035) is formed in this order, and the Al _x Ga _{1 -x} N epi layer 24 having a different Al composition ratio x is further formed on the In _y Ga _{1 -y} N epi layer 22. As a result, an epitaxial layer-attached GaN film composite substrate 2 was formed.
Here, when the Al composition ratio x when forming the Al _x Ga _1-x N epilayer 24 is 0.02, 0.04, 0.06, 0.08, 0.10, and 0.12. The critical thickness at which cracks begin to occur in the Al _x Ga _1-x N epilayer 24 (that is, the minimum thickness at which cracks occur) was measured from a Nomarski image and / or a fluorescence image using a fluorescence microscope. They were 2.25 μm, 1.13 μm, 0.75 μm, 0.56 μm, 0.45 μm, and 0.38 μm, respectively.

Regarding the Al _x Ga _1-x N epilayer 24 of Example A1, the relationship between the Al composition ratio and the critical thickness was plotted in FIG. 10, and the relationship shown by the curve EA1 was found. That is, the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer 24 have a relationship of x × t _x ≈0.045, and x × t _x ≧ 0 represented by the formula (1). .028 relationship was satisfied. The In composition ratio y and the thickness t _y μm of the In _y Ga _1-y N epilayer 22 are between the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer, There was a relationship of y × t _y ≈0.08x × t _{x, and} the relationship of 0.01 × x × t _x ≦ y × t _y ≦ 2 × x × t _x which is the expression (2) was satisfied.

(Example A2)
This Example A2 is an example of the epitaxial layer-attached GaN film composite substrate of the third example of Embodiment 1 as in Example 1, and with reference to FIG. The GaN film composite with an epi layer having the same epi layer structure as in Example 1 except that the thickness of the In _y Ga _1-y N epi layer 22 of 07 was set to 1 μm (y × t _y = 0.07). A substrate 2 was formed.
Here, when the Al composition ratio x when forming the Al _x Ga _1-x N epilayer 24 is 0.02, 0.04, 0.06, 0.08, 0.10, and 0.12. The critical thickness at which cracks begin to occur in the Al _x Ga _1-x N epilayer 24 (ie, the minimum thickness at which cracks occur) are 8.10 μm, 4.05 μm, 2.70 μm, 2.03 μm, 1 0.62 μm and 1.35 μm.

Regarding the Al _x Ga _1-x N epilayer 24 of Example A2, the relationship between the Al composition ratio and the critical thickness was plotted in FIG. 10, and the relationship shown by the curve EA2 was found. That is, the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer 24 have a relationship of x × t _x ≈0.162), and x × t _x ≧ equation (1) The relationship of 0.028 was satisfied. The In composition ratio y and the thickness t _y μm of the In _y Ga _1-y N epilayer 22 are between the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer, There was a relationship of y × t _y ≈0.43x × t _{x, and} the relationship of 0.01 × x × t _x ≦ y × t _y ≦ 2 × x × t _x which is the expression (2) was satisfied.

(Comparative Example A)
Referring to FIG. 7, an epitaxial layer-attached GaN film composite substrate was formed in the same manner as Example A1 except that the In _y Ga _1-y N epilayer having an In composition ratio y of 0.07 was not formed. . That is, by MOCVD, an Al _z Ga _{1 -z} N epilayer 28 having a thickness of 0.05 μm and an Al composition ratio z of 0.05 μm and a thickness of 4.5 μm are formed on the GaN film 13 of the GaN film composite substrate 1. A GaN epi layer 26 (z × t _z = 0.0025) is formed in this order, and an Al _x Ga _1-x N epi layer 24 having a different Al composition ratio x is formed on the GaN epi layer 26, thereby producing an epi. A layered GaN film composite substrate 2 was formed.

Here, when the Al composition ratio x when forming the Al _x Ga _1-x N epilayer 24 is 0.02, 0.04, 0.06, 0.08, 0.10, and 0.12. The critical thickness at which cracks start to occur in the Al _x Ga _1-x N epilayer (that is, the minimum thickness at which cracks occur) are 1.35 μm, 0.68 μm, 0.45 μm, 0.34 μm,. 27 μm and 0.23 μm.

Regarding the Al _x Ga _1-x N epilayer 24 of Comparative Example A, the relationship between the Al composition ratio and the critical thickness was plotted in FIG. 10, and the relationship shown by the curve RA was found. That is, the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer 24 have a relationship of x × t _x ≈0.027, and x × t _x ≧ 0 expressed by Equation (1). .028 relationship was not satisfied.

(Reference Example A)
Referring to FIG. 8, a GaN epilayer having a thickness of 3 μm is formed by MOCVD on a sapphire substrate 31 having a diameter of 100 mm and a thickness of 850 μm, and an Al composition ratio is further formed on the In _y Ga _1-y N epilayer. By forming Al _x Ga _1-x N epilayers with different _x , an epilayer-attached GaN film composite substrate 2S was formed.

Here, when the Al composition ratio x when forming the Al _x Ga _1-x N epilayer is 0.02, 0.04, 0.06, 0.08, 0.10, and 0.12, The critical thickness at which cracks begin to occur in the Al _x Ga _1-x N epilayer (ie, the minimum thickness at which cracks occur) are 6.08 μm, 3.04 μm, 2.03 μm, 1.52 μm, and 1.22 μm, respectively. And 1.02 μm.

Regarding the Al _x Ga _1-x N epilayer 24 of Reference Example A, the relationship between the Al composition ratio and the critical thickness was plotted in FIG. 10, and the relationship shown by the curve SA was found. That is, the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer 24 have a relationship of x × t _x ≈0.122, and x × t _x ≧ 0 expressed by Equation (1). .028 relationship was satisfied.

(Comparative Example B)
3 and 7, in this comparative example B, the In _y Ga _1-y N epilayer 22 is excluded from the epilayer _- attached GaN film composite substrate 2 (FIG. 3) of the third example of the first embodiment. This is a comparative example of the epitaxial layer-attached GaN film composite substrate 2R (FIG. 7).

1. Preparation of GaN film composite substrate Referring to FIG. 7, in the same manner as in Example A1, a mullite substrate having a thickness of 350 μm (a molar ratio of Al ₂ O ₃ and SiO ₂ of 3: 2) is used as support substrate 11. A GaN film composite substrate 1 having a diameter of 100 mm, including a SiO ₂ film having a thickness of 0.5 μm, which is a bonding film 12 disposed thereon, and a GaN film 13 having a thickness of 0.2 μm disposed thereon. Prepared.

2. Referring to epi layer with GaN film composite molding 7 of the substrate, on the GaN film 13 of GaN film composite substrate 1 by MOCVD, Al composition ratio z of the thickness of 0.05μm is 0.05 Al _z Ga _{A 1-z} N epi layer 28 (z × t _z = 0.0025) and a GaN epi layer 26 having a thickness of 4.5 μm are formed in this order, and an Al composition ratio x is 0.08 on the GaN epi layer 26. By forming the Al _x Ga _1-x N epilayer 24 in this order, the epilayer-attached GaN film composite substrate 2 was formed.

Here, Al _x Ga _1-x N critical thickness of Al _x Ga _1-x N cracks in epi layer 24 when forming the epitaxial layer 24 begins to occur (the minimum thickness or generation of cracks) is performed When measured in the same manner as in Example A1, it was 0.34 μm. That is, the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer 24 have a relationship of x × t _x ≈0.027, and x × t _x ≧ 0 expressed by Equation (1). .028 relationship was not satisfied.

(Example B1)
This Example B1 is an example of the GaN film composite substrate with an epi layer of the first example of the first embodiment.

1. Preparation of GaN Film Composite Substrate With reference to FIG. 1, in the same manner as in Example A1, a 350 μm thick mullite substrate (Molar ratio of Al ₂ O ₃ and SiO ₂ is 3: 2) as a support substrate 11 A GaN film composite substrate 1 having a diameter of 100 mm, including a SiO ₂ film having a thickness of 0.5 μm, which is a bonding film 12 disposed thereon, and a GaN film 13 having a thickness of 0.2 μm disposed thereon. Prepared.

2. Formation of epilayer-attached GaN film composite substrate Referring to FIG. 1, In _y Ga ₁ having a thickness of 0.05 μm and an In composition ratio y of 0.07 is formed on GaN film 13 of GaN film composite substrate 1 by MOCVD. _-y N epitaxial layer _{22 (y × t y = 0.0035} ) is formed, further in _y Ga _1-y N epitaxial layer 22 on the Al composition ratio x of 0.08 of Al _x Ga _1-x N epitaxial By forming the layer 24, the epitaxial layer-attached GaN film composite substrate 2 was formed.

Here, Al _x Ga _1-x N critical thickness of Al _x Ga _1-x N cracks in epi layer 24 when forming the epitaxial layer 24 begins to occur (the minimum thickness or generation of cracks) is performed When measured in the same manner as in Example A1, it was 0.56 μm. That is, the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer 24 have a relationship of x × t _x ≈0.045, and x × t _x ≧ 0 represented by the formula (1). .028 relationship was satisfied. The In composition ratio y and the thickness t _y μm of the In _y Ga _1-y N epilayer 22 are between the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer 24. , Y × t _y ≈0.08x × t _{x, and} the relationship of 0.01 × x × t _x ≦ y × t _y ≦ 2 × x × t _x which is the expression (2) was satisfied. In addition, the critical thickness of the Al _x Ga _1-x N epilayer 24 in Example B1 is larger than the critical thickness of the Al _x Ga _1-x N epilayer 24 in Comparative Example B, which will be compared with Comparative Example B described later. This was equivalent to the critical thickness of the Al _x Ga _1-x N epilayer 24 in Example B3.

(Example B2)
Example B2 is an example of the epitaxial layer-attached GaN film composite substrate of the second example of the first embodiment.

1. Preparation of GaN Film Composite Substrate With reference to FIG. 2, a GaN film composite substrate 1 similar to Example A1 was prepared.

2. Formation of epilayer-attached GaN film composite substrate Referring to FIG. 2, GaN epilayer 26 having a thickness of 3 μm and In composition having a thickness of 0.05 μm are formed on GaN film 13 of GaN film composite substrate 1 by MOCVD. in _y Ga _1-y N epitaxial layer 22 of the ratio y is _{0.07 (y × t y = 0.0035} ) was formed in this order, further in _y Ga _1-y N Al composition ratio on the epitaxial layer 22 x By forming the Al _x Ga _1-x N epilayer 24 having a thickness of 0.08, the epitaxial layer-attached GaN film composite substrate 2 was formed.

Here, Al _x Ga _1-x N critical thickness of Al _x Ga _1-x N cracks in epi layer 24 when forming the epitaxial layer 24 begins to occur (the minimum thickness or generation of cracks) is performed When measured in the same manner as in Example A1, it was 0.58 μm. That is, the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer 24 have a relationship of x × t _x ≈0.046, and x × t _x ≧ 0 represented by the equation (1). .028 relationship was satisfied. The In composition ratio y and the thickness t _y μm of the In _y Ga _1-y N epilayer 22 are between the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer, There was a relationship of y × t _y ≈0.08x × t _{x, and} the relationship of 0.01 × x × t _x ≦ y × t _y ≦ 2 × x × t _x which is the expression (2) was satisfied. The critical thickness of the Al _x Ga _1-x N epitaxial layer 24 in Example B2 was equivalent to the critical thickness of the Al _x Ga _1-x N epitaxial layer 24 in the embodiment B1.

(Example B3)
Example B3 is an example of the epitaxial layer-attached GaN film composite substrate of the third example of the first embodiment.

1. Preparation of GaN Film Composite Substrate With reference to FIG. 3, a GaN film composite substrate 1 similar to Example A1 was prepared.

2. Referring to form Figure 3 GaN film composite substrate epilayer, on the GaN film 13 of GaN film composite substrate 1 by MOCVD, Al composition ratio z of the thickness of 0.05μm is 0.05 Al _z Ga _1-z N epi layer 28 (z × t _z = 0.0025), GaN epi layer 26 having a thickness of 4.5 μm, and In _y Ga ₁₋ having a thickness of 0.05 μm and an In composition ratio y of 0.07 _{An y} N epi layer 22 (y × t _y = 0.0035) is formed in this order, and an Al _x Ga _1-x N having an Al composition ratio x of 0.08 is further formed on the In _y Ga _{1 -y} N epi layer 22. The epitaxial layer-attached GaN film composite substrate 2 was formed by forming the epitaxial layer 24 in this order.

Here, Al _x Ga _1-x N critical thickness of Al _x Ga _1-x N cracks in epi layer 24 when forming the epitaxial layer 24 begins to occur (the minimum thickness or generation of cracks) is performed When measured in the same manner as in Example A1, it was 0.55 μm. That is, the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer 24 have a relationship of x × t _x ≈0.044, and x × t _x ≧ 0 expressed by Equation (1). .028 relationship was satisfied. The In composition ratio y and the thickness t _y μm of the In _y Ga _1-y N epilayer 22 are between the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer, There was a relationship of y × t _y ≈0.08x × t _{x, and} the relationship of 0.01 × x × t _x ≦ y × t _y ≦ 2 × x × t _x which is the expression (2) was satisfied. Further, the critical thickness of the Al _x Ga _1-x N epilayer 24 in Example B3 is larger than the critical thickness of the Al _x Ga _1-x N epilayer 24 in the comparative example B to be compared, and the Al _x Ga _1-x N epilayer 24 in the comparative example B is larger. It was equivalent to the critical thickness of the _x Ga _1-x N epilayer 24.

(Example B4)
Example B4 is an example of the GaN film composite substrate with an epi layer of the fourth example of the first embodiment.

1. Preparation of GaN Film Composite Substrate With reference to FIG. 4, a GaN film composite substrate 1 similar to Example A1 was prepared.

2. Formation of epilayer-attached GaN film composite substrate Referring to FIG. 4, an In _y Ga having a thickness of 0.05 μm and an In composition ratio of 0.07 is formed on GaN film 13 of GaN film composite substrate 1 by MOCVD. _1-y N epitaxial layer _{22 (y × t y = 0.0035} ) and a thickness of 3μm of GaN epi-layer 26 (※ 15: thickness of the GaN epitaxial layer in Comparative example B and example B3, B5 4. The thickness is 5 μm, which is different from Example B4.From the viewpoint of comparison, I think that the same thickness is preferable between Comparative Example B and Examples B2 to B5. If there is, please tell us)) in this order, and further, an Al _x Ga _1-x N epilayer 24 having an Al composition ratio x of 0.08 is formed on the GaN epilayer 26, thereby forming the GaN with epilayer A membrane composite substrate 2 was formed.

Here, Al _x Ga _1-x N critical thickness of Al _x Ga _1-x N cracks in epi layer 24 when forming the epitaxial layer 24 begins to occur (the minimum thickness or generation of cracks) is performed It was 0.57 micrometer when measured similarly to Example A1. That is, the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer 24 have a relationship of x × t _x ≈0.046, and x × t _x ≧ 0 represented by the equation (1). .028 relationship was satisfied. The In composition ratio y and the thickness t _y μm of the In _y Ga _1-y N epilayer 22 are between the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer, There was a relationship of y × t _y ≈0.08x × t _{x, and} the relationship of 0.01 × x × t _x ≦ y × t _y ≦ 2 × x × t _x which is the expression (2) was satisfied. Further, the critical thickness of the Al _x Ga _1-x N epilayer 24 in Example B4 was equal to the critical thickness of the Al _x Ga _1-x N epilayer 24 in Example B1.

(Example B5)
Example B5 is an example of the epitaxial layer-attached GaN film composite substrate of the fifth example of the first embodiment.

1. Preparation of GaN Film Composite Substrate With reference to FIG. 5, a GaN film composite substrate 1 similar to Example A1 was prepared.

2. Referring to formation Figure 5 GaN film composite substrate epilayer, on the GaN film 13 of GaN film composite substrate 1 by MOCVD, Al composition ratio z of the thickness of 0.05μm is 0.05 Al _z Ga _1-z N epi layer 28 (z × t _z = 0.0025), In _y Ga _1-y N epi layer 22 (y × t _y = 0) having a thickness of 0.05 μm and an In composition ratio y of 0.07 , And a 4.5 μm thick GaN epi layer 26 in this order, and an Al _x Ga _1-x N epi layer 24 having an Al composition ratio x of 0.08 on the GaN epi layer 26 in this order. By forming, the epitaxial layer-attached GaN film composite substrate 2 was formed.

Here, Al _x Ga _1-x N critical thickness of Al _x Ga _1-x N cracks in epi layer 24 when forming the epitaxial layer 24 begins to occur (the minimum thickness or generation of cracks) is performed When measured in the same manner as in Example A1, it was 0.55 μm. That is, the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer 24 have a relationship of x × t _x ≈0.044, and x × t _x ≧ 0 expressed by Equation (1). .028 relationship was satisfied. The In composition ratio y and the thickness t _y μm of the In _y Ga _1-y N epilayer 22 are between the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer, There was a relationship of y × t _y ≈0.08x × t _{x, and} the relationship of 0.01 × x × t _x ≦ y × t _y ≦ 2 × x × t _x which is the expression (2) was satisfied. Further, the critical thickness of the Al _x Ga _1-x N epilayer 24 in Example B5 was equal to the critical thickness of the Al _x Ga _1-x N epilayer 24 in Example B1.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 GaN film composite substrate 2 epilayer GaN film composite substrate 11 supporting substrate 11m, 13n major surface 12, 12a, 12b bonding film 13 GaN film 13i ion implantation region 13D, 13Dr GaN film donor substrate 22 In _y Ga _1-y N Epi layer 24 Al _x Ga _{1 -x} N epi layer 26 GaN epi layer 28 Al _z Ga _{1 -z} N epi layer 31 Sapphire substrate.

Claims (9)

A GaN film composite substrate obtained by bonding a support substrate and a GaN film, an In _y Ga _1-y N epilayer (0 <y <1) and Al _x arranged in order from the GaN film side of the GaN film composite substrate. Ga _1-x N epilayer (0 <x <1), and
The Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer are expressed by the formula (1)
x × t _x ≧ 0.028 (1)
A GaN film composite substrate with an epi layer that satisfies the above relationship. The In composition ratio y and the thickness t _y μm of the In _y Ga _1-y N epilayer are expressed by the formula between the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer. (2)
0.01 × x × t _x ≦ y × t _y ≦ 2 × x × t _x (2)
The GaN film composite substrate with an epi layer according to claim 1, satisfying the relationship: The GaN in the thickness t _f is 0.05μm or more 50μm or less GaN film composite substrate with epitaxial layer according to claim 1 or claim 2 of the membrane. The GaN film composite substrate with an epi layer according to any one of claims 1 to 3, further comprising a GaN epi layer disposed between the GaN film and the In _y Ga _1-y N epi layer. . An Al _z Ga _{1 -z} N epi layer (0 <z <1) disposed between the GaN film and the GaN epi layer;
The Al composition ratio z and the thickness t _z μm of the Al _z Ga _1-z N epilayer are expressed by the formula (3).
z × t _z <0.028 (3)
The GaN film composite substrate with an epi layer according to claim 4, satisfying the relationship: 4. The GaN epi layer according to claim 1, further comprising a GaN epi layer disposed between the In _y Ga _1-y N epilayer and the Al _x Ga _1-x N epilayer. 5. GaN film composite substrate with epi layer. An Al _z Ga _1-z N epilayer (0 <z <1) disposed between the GaN film and the In _y Ga _1-y N epilayer;
The Al composition ratio z and the thickness t _z μm of the Al _z Ga _1-z N epilayer are expressed by the formula (3).
z × t _z <0.028 (3)
The GaN film composite substrate with an epi layer according to claim 6, satisfying the relationship: Preparing a GaN film composite substrate obtained by bonding a support substrate and a GaN film;
At least an In _y Ga _1-y N epilayer (0 <y <1) and an Al _x Ga _1-x N epilayer (0 <x <1) are formed in this order on the GaN film side of the GaN film composite substrate. A step of forming a GaN film composite substrate with an epi layer by,
The Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer are expressed by the formula (1)
x × t _x ≧ 0.028 (1)
The manufacturing method of the GaN film | membrane composite substrate with an epi layer which satisfy | fills these relationships. The In composition ratio y and the thickness t _y μm of the In _y Ga _1-y N epilayer are expressed by the formula between the Al composition ratio x and the thickness t _x μm of the Al _x Ga _1-x N epilayer. (2)
0.01 × x × t _x ≦ y × t _y ≦ 2 × x × t _x (2)
The manufacturing method of the GaN film | membrane composite substrate with an epi layer of Claim 8 which satisfy | fills the relationship of these.

Images