JP2011140428A - Method for manufacturing nitride-based compound semiconductor substrate, and nitride-based compound semiconductor self-standing substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a nitride-based compound semiconductor substrate, by which a nitride-based compound semiconductor layer free from a warp and having little variation in the off-angle in the plane is grown with satisfactory reproducibility, and to provide a nitride-based compound semiconductor self-standing substrate suitable for manufacturing a semiconductor device. <P>SOLUTION: In the method for manufacturing a nitride-based compound semiconductor substrate, comprising epitaxially growing a nitride-based compound semiconductor layer on a substrate for growth, a rare earth perovskite substrate having a main plane, where the (011) plane is made to incline at an off angle of 0-2°(0° is excepted) in ≈[010] direction, is used as the substrate for growth. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a nitride-based compound semiconductor substrate and a nitride-based compound semiconductor free-standing substrate, and more particularly to an off direction and an off angle of a main surface of a growth substrate.

  Conventionally, a semiconductor device (for example, an electronic device or an optical device) obtained by epitaxially growing a nitride compound semiconductor such as GaN (hereinafter referred to as a GaN-based semiconductor) on a substrate is known. For this semiconductor device, a substrate mainly made of sapphire or SiC is used. However, since these substrate materials have a large lattice mismatch with a GaN-based semiconductor, when a GaN-based semiconductor is epitaxially grown on the substrate, distortion occurs due to strain. Crystal defects will occur. And the crystal defect which arose in the epitaxial layer becomes a factor which reduces the characteristic of a semiconductor device. Therefore, various growth methods have been tried to solve the problems caused by such lattice mismatch.

For example, Patent Document 1 proposes to use an NdGaO ₃ substrate (hereinafter referred to as an NGO substrate) whose pseudo lattice constant is close to that of a GaN-based semiconductor. Specifically, a technique is disclosed in which a GaN thick film is grown on an NGO substrate by hydride vapor phase epitaxy (HVPE) to produce a GaN free-standing substrate (a substrate composed only of GaN). Yes. On the (011) plane of the NGO substrate, the length of the NGO a-axis and the lattice constant in the [11-20] direction of GaN substantially coincide with each other, so that the problem caused by the lattice mismatch described above can be solved. The device characteristics can be improved by using the GaN free-standing substrate as a semiconductor device substrate.

  In addition, the growth of the GaN thick film layer is generally performed at a growth temperature of about 1000 ° C., but when the NGO substrate is exposed to the source gas at a high temperature of about 1000 ° C., the GaN thick film layer changes in quality. The crystal quality of the will deteriorate. Therefore, a technique for protecting the NGO substrate by growing a GaN thin film layer called a low-temperature protective layer on the NGO substrate at around 600 ° C. before growing the GaN thick film layer (for example, Patent Documents 1 and 2). .

JP 2003-257854 A JP 2000-4045 A

  However, after the GaN thick film layer was grown at 1000 ° C., when the temperature was lowered to room temperature, stress was applied to the GaN thick film layer due to the difference in thermal expansion coefficient between GaN and NGO, and the GaN thick film layer warped. As a result, in-plane off-angle variation increases. Further, even in a GaN free-standing substrate obtained by separating the warped GaN thick film layer from the NGO substrate and cutting out from this GaN thick film crystal, the variation in the in-plane off angle becomes large. If the variation in the off angle within the surface of the GaN free-standing substrate becomes large, there is a possibility that desired characteristics (for example, the emission wavelength of the light emitting element) cannot be obtained in a semiconductor device using the substrate.

  INDUSTRIAL APPLICABILITY The present invention is suitable for a method of manufacturing a nitride-based compound semiconductor substrate capable of growing a nitride-based compound semiconductor layer without warping and having a small in-plane off-angle variation with good reproducibility, and for manufacturing a semiconductor device. An object is to provide a nitride-based compound semiconductor free-standing substrate.

In order to achieve the above object, the invention described in claim 1
In a method for manufacturing a nitride-based compound semiconductor substrate in which a nitride-based compound semiconductor layer is epitaxially grown on a growth substrate,
As the growth substrate, a rare earth perovskite substrate having a main surface in which the (011) plane is inclined at an off angle of 0 to 2 ° (excluding 0 °) in the ≈ [010] direction is used.

  Here, the “≈ [010] direction” is a direction (CCW 90 °) rotated 90 ° counterclockwise from the [100] direction with the [011] direction as an axis, strictly speaking, the [010] direction. It shows that it is slightly deviated from. The [100] direction and the [010] direction in the (011) plane of NGO correspond to the [1-100] direction and the [11-20] direction in the (0001) plane of GaN, respectively.

  According to a second aspect of the present invention, in the method for producing a nitride-based compound semiconductor substrate according to the first aspect, as the growth substrate, a (011) plane is inclined by 1 ° in the ≈ [010] direction. It is characterized by using a rare earth perovskite substrate having

The invention according to claim 3 is a method for producing a nitride-based compound semiconductor substrate according to claim 1 or 2, wherein a hydride vapor phase epitaxy (HVPE) is used to form a group III metal and A nitride compound semiconductor is epitaxially grown on a growth substrate by reacting a chloride gas generated from HCl with NH ₃ .

The invention according to claim 4 is a nitride system obtained by separating the nitride compound semiconductor layer from the nitride compound semiconductor substrate manufactured by the manufacturing method according to any one of claims 1 to 3. A compound semiconductor free-standing substrate,
The variation in off-angle with respect to the [11-20] direction and the [1-100] direction in the plane is 1 ° or less, respectively.

Conventionally, when a GaN free-standing substrate is manufactured by using the HVPE method, a low-temperature protective layer and a GaN thick film layer are formed on an NGO substrate having a main surface whose (011) plane is inclined by −2 ° in the [100] direction. It was growing. In this case, the warpage of the GaN thick film layer is large, and the variations of the off angles with respect to the [11-20] direction and the [1-100] direction in the GaN thick film layer are 1.11 ° and 1.22 °, respectively. It was over °. Even in such a GaN free-standing substrate made of a GaN thick film layer, the variation in off-angle exceeded 1 °.
Accordingly, the present inventors have focused on the main surface (growth surface) of the NGO substrate on which GaN is epitaxially grown, experimentally found the range of the off direction and the off angle that are optimal for the manufacture of the GaN-based semiconductor substrate, and arrived at the present invention. did.

  According to the present invention, it is possible to grow a nitride-based compound semiconductor layer with no reproducibility and a small variation in off-angle with respect to the in-plane [11-20] direction and [1-100] direction with good reproducibility. A nitride-based compound semiconductor free-standing substrate suitable for device fabrication can be obtained.

The figure which shows about the dispersion | variation in an off angle when measuring the off angle with respect to a [1-100] direction and a [11-20] direction at five points in a plane about the GaN self-supporting substrate produced in the Example and the comparative example 1. is there. It is a figure which shows about the dispersion | variation in an off angle when measuring the off angle with respect to a [1-100] direction and a [11-20] direction at five points in a plane about the GaN self-supporting substrate produced by the comparative example 2. FIG. It is a figure shown about the definition of the main surface of an off substrate.

Embodiments of the present invention are described in detail below.
In the present embodiment, a method for manufacturing a GaN substrate by epitaxially growing GaN, which is a GaN-based semiconductor, on an NGO substrate made of a rare earth perovskite using the HVPE method will be described. In the HVPE method, chloride gas (GaCl) generated from group III metal Ga and HCl is reacted with NH ₃ to epitaxially grow a GaN layer on the substrate.

  At this time, an NGO substrate having a main surface in which the (011) plane is inclined in the ≈ [010] direction at an off angle of 0 to 2 ° (excluding 0 °) is used as a growth substrate. Here, the principal surface obtained by inclining the (011) plane in the ≈ [010] direction with the off angle X is defined as shown in FIG. That is, the normal surface is inclined by the off-angle X from the [011] direction toward the [010] direction.

This NGO substrate is placed in the HVPE apparatus and heated up until the substrate temperature reaches the first growth temperature (400 to 800 ° C.). Then, GaCl as a group III material generated from Ga metal and HCl and NH ₃ as a group V material are supplied onto the NGO substrate to form a low-temperature protective layer made of GaN.
Next, the temperature is raised until the substrate temperature reaches the second growth temperature (950 to 1050 ° C.). Then, a source gas is supplied onto the low temperature protective layer to form a GaN thick film layer.

  As described above, a GaN substrate in which a low-temperature protective layer and a GaN thick film layer are formed on an NGO substrate is obtained. The GaN thick film layer in the GaN substrate does not warp, and the variation in off-angle with respect to the in-plane [1-100] direction and [11-20] direction is 1 ° or less. Further, after cooling to room temperature, the NGO free-standing substrate obtained by removing the NGO substrate by an appropriate method and polishing down is also used for the in-plane [1-100] direction and [11-20] direction off-angles. Variation of 1 ° or less. Therefore, by using this GaN free-standing substrate as a substrate for manufacturing a semiconductor device, a semiconductor device having desired characteristics can be realized.

[Example]
In the examples, an NGO substrate having a main surface in which the (011) plane is inclined in the ≈ [010] direction with an off angle of 0 to 2 ° was used.
On this NGO substrate, a raw material gas is supplied so that the supply partial pressure of HCl is 2.19 × 10 ⁻³ atm and the supply partial pressure of NH ₃ is 6.58 × 10 ⁻² atm. A protective layer was grown to 50 nm.
Next, a source gas is supplied onto the low-temperature protective layer so that the supply partial pressure of HCl is 1.06 × 10 ⁻² atm and the supply partial pressure of NH ₃ is 5.00 × 10 ⁻² atm. A 2500 μm thick GaN thick film layer was grown. At this time, the growth temperature was 1000 ° C., and the growth time was 8 hours.

[Comparative Example 1]
In Comparative Example 1, an NGO substrate having a main surface in which the (011) plane is inclined at an off angle of 4 ° in the ≈ [010] direction, and a low-temperature protective layer and a GaN thick film made of GaN as in the example are used. Growing layers.

  FIG. 1 shows the variation in off-angle when the off-angle is measured with respect to the [1-100] direction and the [11-20] direction for the GaN thick film layer of the GaN substrate produced in Example and Comparative Example 1. FIG. Note that a total of 5 points, which are one point in the plane of the GaN thick film layer and four points located on the peripheral edge on the orthogonal axis passing through the center point, are the measurement points. Based on the off angles at the five measurement points, the variation in the off angle is calculated by (maximum value−minimum value) / 2.

In the GaN thick film layer obtained in the example, the variation in the off angle with respect to the [1-100] direction and the [11-20] direction was 1 ° or less, whereas the GaN thick film obtained in the comparative example. In the layer, the variation in the off angle with respect to the [1-100] direction and the [11-20] direction was 1.5 ° or more. In particular, when an NGO substrate having a main surface in which the (011) plane is inclined at an off angle of 1 ° in the ≈ [010] direction is used, the off-direction with respect to the [1-100] direction and the [11-20] direction is used. The angle variation was 0.2 °, which was very good.
Further, when the obtained GaN thick film layer was visually observed for warping, the GaN thick film layer obtained in the example was clearly less warped than the GaN thick film layer obtained in the comparative example. It was.

[Comparative Example 2]
In Comparative Example 2, the GaN substrate having the main surface with the (011) plane inclined in the [100] direction at an off angle of −2 °, 1 °, 2 °, and 4 ° was used in the same manner as in the example. A low-temperature protective layer and a GaN thick film layer were grown.
FIG. 2 shows the off angle when the off angle with respect to the [1-100] direction and the [11-20] direction is measured at five points in the surface of the GaN thick film layer of the GaN substrate manufactured in Comparative Example 2. It is a figure shown about dispersion | variation.
As shown in FIG. 2, in the GaN thick film obtained in Comparative Example 2, the variation of the off angle with respect to the [1-100] direction and the [11-20] direction was both 1 ° or more. Further, when the obtained GaN thick film layer was visually checked for warpage, the warpage was clearly larger than that of the GaN thick film layer obtained in the examples.

As described above, in this embodiment, since the off direction and off angle of the NGO substrate are optimized, there is no warping and variation of the off angle with respect to the [1-100] direction and [11-20] direction in the plane. It is possible to grow a GaN thick film layer having an angle of 1 ° or less with good reproducibility.
Moreover, a GaN free-standing substrate suitable for manufacturing a semiconductor device can be obtained by separating a GaN thick film layer from the GaN substrate obtained in the embodiment and polishing it to prepare a GaN free-standing substrate.

As mentioned above, although the invention made by this inventor was concretely demonstrated based on embodiment, this invention is not limited to the said embodiment, It can change in the range which does not deviate from the summary.
In the above embodiment, the case where GaN, which is a nitride compound semiconductor, is grown on a growth substrate has been described. However, the present invention can also be applied to the case where a nitride compound semiconductor layer is grown on a growth substrate. it can. Here, the nitride-based compound semiconductor is a compound semiconductor represented by In _x Ga _y Al _1-xy N (0 ≦ x + y ≦ 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1). For example, there are GaN, InGaN, AlGaN, InGaAlN, and the like.
In the embodiment, the case where the HVPE method is used has been described. However, a nitride system using a metal organic chemical vapor deposition (MOCVD) method or a molecular beam epitaxy (MBE) method is used. The present invention can be applied to epitaxial growth of a compound semiconductor layer.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. 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.

Claims (4)

In a method for manufacturing a nitride-based compound semiconductor substrate in which a nitride-based compound semiconductor layer is epitaxially grown on a growth substrate,
As the growth substrate, a rare earth perovskite substrate having a main surface in which a (011) plane is inclined at an off angle of 0 to 2 ° (excluding 0 °) in the ≈ [010] direction is used. For manufacturing a semiconductor compound semiconductor substrate.   2. The production of a nitride-based compound semiconductor substrate according to claim 1, wherein a rare earth perovskite substrate having a main surface whose (011) plane is inclined by 1 ° in the ≈ [010] direction is used as the growth substrate. Method. Using a hydride vapor phase epitaxy (HVPE), a nitride compound semiconductor is epitaxially grown on a growth substrate by reacting a group III metal, a chloride gas generated from HCl, and NH ₃ . The method for producing a nitride-based compound semiconductor substrate according to claim 1 or 2, A nitride compound semiconductor free-standing substrate obtained by separating the nitride compound semiconductor layer from the nitride compound semiconductor substrate produced by the production method according to any one of claims 1 to 3,
A nitride-based compound semiconductor free-standing substrate, wherein variations in off-angle with respect to the [11-20] direction and the [1-100] direction in the plane are each 1 ° or less.

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