JP2020200235A - C PLANE GaN SUBSTRATE - Google Patents

Abstract

To provide a new C plane GaN substrate used for manufacturing a nitride semiconductor device and a bulk nitride semiconductor crystal, and a method for manufacturing the same.SOLUTION: A method for manufacturing a C plane GaN substrate 10 comprises: arranging a pattern mask having a periodic opening pattern provided on the polar surface of a GaN seed and composed of a linear opening; forming a gap between a GaN crystal and the pattern mask by ammonothermally growing the GaN crystal through the pattern mask; and growing the GaN crystal in a C axis direction; and processing the GaN crystal to obtain the C plane GaN substrate 10. In the C plane GaN substrate 10, when an X ray incident surface is parallel to each line segment when ω scanning on virtual line segments LS1 and LS2 drawn on the main surface of the C plane GaN substrate 10 and having a length of 40 mm and the XRC of (004) reflection is measured at an interval of 1 mm, the maximum value of FWHM of XRC among all measurement points is less than 30 arcsec and a difference between the maximum value and minimum value of peak angles of the XRC is less than 0.2°.SELECTED DRAWING: Figure 3

Description

The present invention mainly relates to a C-plane GaN substrate.

GaN (gallium nitride) is a kind of group III-V compound semiconductor and has a wurtzite type crystal structure belonging to a hexagonal system.
In recent years, a GaN single crystal substrate has attracted attention as a semiconductor substrate for a nitride semiconductor device.
Nitride semiconductors are also called nitride-based III-V group compound semiconductors, group III nitride-based compound semiconductors, GaN-based semiconductors, etc., and include GaN and part or all of GaN gallium in other periodic tables. Includes compounds substituted with Group 13 elements (B, Al, In, etc.).

One of the highly useful GaN single crystal substrates is a C-plane GaN substrate. The C-plane GaN substrate is a GaN single crystal substrate having a main surface parallel to the C-plane or slightly inclined from the C-plane.
The C-plane GaN substrate has a gallium polar surface which is the main surface on the [0001] side and a nitrogen polar surface which is the main surface on the [000-1] side. Currently, gallium polar surfaces are mainly used to form nitride semiconductor devices.
An example of producing a C-plane GaN substrate from a GaN single crystal grown by the amonothermal method has been reported (Non-Patent Document 1 and Non-Patent Document 2).

In Patent Document 1, a GaN crystal is grown on a C-plane GaN substrate provided with a striped pattern mask by an amonothermal method. NH 4 _{F (ammonium} fluoride) are used alone as a mineralizer, through a patterned mask, is that of the GaN crystal film having a thickness of 160~580μm having a flat upper surface grown. It is not clear whether the pattern mask was formed on the gallium polar surface or the nitrogen polar surface.

In Patent Document 2, a GaN single crystal is grown by an amonothermal method on a C-plane GaN substrate provided with a striped pattern mask on a nitrogen-polar surface. NH ₄ F and NH ₄ I (ammonium iodide) are used together as a mineralizing agent, and the GaN crystal does not coreless even after passing through the pattern mask until the size in the c-axis direction is on the order of millimeters [ It is said that it grew in the direction of 000-1].
Non-Patent Document 3 reports the growth rate of GaN crystals when various ammonium halide mineralizing agents are used in the amonothermal method.

Japanese Unexamined Patent Publication No. 2014-11527 Japanese Unexamined Patent Publication No. 2014-208571

R.Dwilinski, R.Doradzinski, J.Garczynski, LPSierzputowski, A.Puchalski, Y.Kanbara, K.Yagi, H.Minakuchi, H.Hayashi, “Excellent crystallinity of truly bulk ammonothermal GaN”, Journal of Crystal Growth 310 (2008) 3911-3916 R.Dwilinski, R.Doradzinski, J.Garczynski, L.Sierzputowski, R.Kucharski, M.Zajac, M. Rudzinski, R.Kudrawiec, J.serafnczuk, W.Strupinski, “Recent achievements in AMMONO-bulk method”, Journal of Crystal Growth 312 (2010) 2499-2502 Quanxi Bao, Makoto Saito, Kouji Hazu, Kentaro Furusawa, Yuji Kagamitani, Rinzo Kayano, Daisuke Tomida, Kun Qiao, Tohru Ishiguro, Chiaki Yokoyama, Shigefusa F. Chichibu, “Ammonothermal Crystal Growth of GaN Using an NH4F Mineralizer”, Crystal Growth & Design 4158-4161 (2013) 13

An object of the present invention is to provide a novel C-plane GaN substrate that can be preferably used for manufacturing nitride semiconductor devices, bulk nitride semiconductor crystals and the like.
An object of the present invention is also to provide a novel method for manufacturing a C-plane GaN substrate.

Embodiments of the present invention include:
[1] A C-plane GaN substrate capable of drawing at least one first line segment, which is a virtual line segment having a length of 40 mm, satisfying at least one of the following conditions (A1) and (B1) on the main surface:
(A1) On the first line segment, when the X-ray incident surface at each ω scan is parallel to the first line segment and (004) the XRC of reflection is measured at 1 mm intervals, between all measurement points. The maximum value of FWHM of XRC is less than 30 arcsec;
(B1) On the first line segment, when the X-ray incident surface at each ω scan is parallel to the first line segment and (004) the XRC of reflection is measured at 1 mm intervals, between all measurement points. The difference between the maximum value and the minimum value of the peak angle of XRC is less than 0.2 °.
[2] The C-plane GaN substrate according to the above [1], wherein the first line segment satisfies the above condition (A1). [3] The C-plane GaN substrate according to the above [2], wherein the first line segment satisfies the following condition (A2) in addition to the above condition (A1): (A2) On the first line segment obtained from the XRC measurement. The average FWHM of XRC among all the measurement points of is less than 20 arcsec.
[4] The C-plane GaN substrate according to the above [2], wherein the first line segment satisfies the following condition (A3) in addition to the above condition (A1): (A3) On the first line segment obtained from the XRC measurement. The mean and standard deviation of the XRC FWHM between all the measurement points of is less than 12 arcsec and less than 5 arcsec, respectively.
[5] At least one second line segment, which is a virtual line segment having a length of 40 mm that satisfies at least one of the following conditions (C1) and (D1), can be drawn on the main surface on which the first line segment can be drawn. , The C-plane GaN substrate according to any one of [1] to [4] above:
(C1) The second line segment is orthogonal to at least one of the first line segments, and the X-ray incident surface at each ω scan is made parallel to the second line segment on the second line segment. (004) When the XRC of reflection is measured at 1 mm intervals, the maximum value of FWHM of XRC between all measurement points is less than 30 arcsec;
(D1) The second line segment is orthogonal to at least one of the first line segments, and the X-ray incident surface at each ω scan is made parallel to the second line segment on the second line segment. (004) When the reflection XRC is measured at 1 mm intervals, the difference between the maximum value and the minimum value of the XRC peak angle among all the measurement points is less than 0.2 °.
[6] The C-plane GaN substrate according to [5], wherein the second line segment satisfies the condition (C1). [7] The C-plane GaN substrate according to [6] above, wherein the second line segment satisfies the following condition (C2) in addition to the condition (C1): (C2) On the second line segment obtained from the XRC measurement. The average FWHM of XRC between all the measurement points of is less than 20 arcsec.
[8] The C-plane GaN substrate according to [6] above, wherein the second line segment satisfies the following condition (C3) in addition to the condition (C1): (C3) On the second line segment obtained from the XRC measurement. The mean and standard deviation of the XRC FWHM between all the measurement points of is less than 12 arcsec and less than 5 arcsec, respectively.
[9] The C-plane GaN substrate according to any one of [1] to [8], which has a plurality of dislocation arrays periodically arranged on the main surface.
[10] The C-plane GaN substrate according to [9], wherein the arrangement of the plurality of dislocation arrays on the main surface is two-dimensional.
[11] The C-plane GaN substrate according to [10], wherein the arrangement of the plurality of dislocation arrays on the main surface has periodicity in two or more directions.
[12] The C-plane GaN substrate according to any one of [1] to [11] above, wherein the concentrations of Li, Na, K, Mg and Ca are less than 1 × 10 ¹⁶ atoms / cm ³ .
[13] The C-plane GaN substrate according to [12], which contains F.
[14] The C-plane GaN substrate according to the above [13], which contains one or more halogens selected from Cl, Br and I in addition to F.
[15] The C-plane GaN substrate according to [14] above, which contains F and I.
[16] The C-plane GaN substrate according to any one of [1] to [15] above, wherein the H concentration is 5 × 10 ¹⁷ atoms / cm ³ or more and 1 × 10 ²⁰ atoms / cm ³ or less.
[17] The C-plane GaN substrate according to any one of [1] to [16] above, which comprises a GaN crystal having an infrared absorption peak attributed to a gallium vacancy-hydrogen complex at 3140 to 3200 cm ^-1 .
[18] The C-plane GaN according to any one of [1] to [17] above, wherein the sizes in the [1-100] direction, the [10-10] direction, and the [01-10] direction are all 45 mm or more. substrate.
[19] The C-plane GaN substrate according to any one of [1] to [18] above, which has a disk shape and a diameter of 45 mm or more.
[20] The C-plane GaN substrate according to any one of [1] to [19] above, which has a gallium polar surface having an orientation within 5 ° from [0001].
[21] The step of preparing the C-plane GaN substrate according to any one of [1] to [20] above, and the step of epitaxially growing one or more nitride semiconductors on the prepared C-plane GaN substrate are included. A method for manufacturing a nitride semiconductor device.
[22] The step of preparing the C-plane GaN substrate according to any one of [1] to [20] above, and the step of epitaxially growing one or more nitride semiconductors on the prepared C-plane GaN substrate are included. A method for manufacturing an epitaxial substrate.
[23] Bulk nitride including the step of preparing the C-plane GaN substrate according to any one of [1] to [20] and the step of epitaxially growing a nitride semiconductor crystal on the prepared C-plane GaN substrate. A method for manufacturing a semiconductor crystal.
[24] A GaN layer bonding substrate including the step of preparing the C-plane GaN substrate according to any one of the above [1] to [20] and the step of bonding the prepared C-plane GaN substrate to a different composition substrate. Manufacturing method.

[25] A first step of preparing a GaN seed having a polar surface of nitrogen; a step of placing a pattern mask on the polar surface of the GaN seed, wherein the pattern mask is periodic consisting of linear openings. A second step in which an opening pattern is provided; a step of adversarially growing a GaN crystal through the pattern mask on the nitrogen polar surface of the GaN seed, between the GaN crystal and the pattern mask. A C-plane GaN substrate manufacturing method comprising a third step in which a gap is formed; and a fourth step in which the GaN crystal is processed to obtain a C-plane GaN substrate.
[26] The manufacturing method according to the above [25], wherein the periodic opening pattern is a stripe pattern.
[27] The manufacturing method according to the above [26], wherein the pitch between the linear openings is 1 mm or more. [28] In the second step, the pattern mask is arranged so that the longitudinal direction of the linear opening is at an angle of 12 ° ± 5 ° with respect to the direction of intersection of the nitrogen polar surface and the M surface. The production method according to any one of the above [25] to [27].
[29] The manufacturing method according to the above [25], wherein the periodic opening pattern includes an intersection.
[30] The manufacturing method according to [29], wherein the arrangement of the intersections in the periodic opening pattern is two-dimensional.
[31] The production method according to the above [30], wherein the pattern mask includes the intersection at a number density of 1 cm- ² or more.
[32] The [30] or [32], wherein the non-openings included in the unit pattern of the pattern mask are all quadrangular or hexagonal, and the pattern mask does not include linear openings arranged at a pitch of less than 1 mm. 31].
[33] The manufacturing method according to the above [32], wherein the pattern mask includes linear openings arranged at a pitch of 10 mm or less.
[34] The pattern mask includes linear openings arranged at a pitch of 2 mm or less and linear openings arranged at a pitch of more than 2 mm, or linear openings arranged at a pitch of 3 mm or less. [32] The present invention includes linear openings arranged at a pitch of more than 3 mm, or linear openings arranged at a pitch of 4 mm or less, and linear openings arranged at a pitch of more than 4 mm. The manufacturing method described in.
[35] The manufacturing method according to the above [34], wherein the pattern mask includes linear openings arranged at a pitch of more than 4 mm.
[36] The periodic opening patterns are square grid patterns, and in the second step, first linear openings and second linear openings having different longitudinal directions are provided in the pattern mask. 35] The manufacturing method according to any one of.
[37] The manufacturing method according to [36], wherein one of the pitch between the first linear openings and the pitch between the second linear openings is 1.5 times or more the other.
[38] In the second step, the pattern is such that the longitudinal direction of at least a part of the linear opening is at an angle of 12 ° ± 5 ° with respect to the direction of the line of intersection between the nitrogen polar surface and the M surface. The production method according to any one of [29] to [37] above, wherein the mask is arranged.
[39] In the second step, the longitudinal direction of the portion of the linear opening that occupies 50% or more of the total length is 12 ° ± 5 ° with respect to the direction of the line of intersection between the nitrogen polar surface and the M surface. The manufacturing method according to any one of [29] to [37], wherein the pattern mask is arranged so as to form an angle.
[40] In the second step, the pattern is such that the longitudinal direction in all the portions of the linear opening is at an angle of 12 ° ± 5 ° with respect to the direction of the line of intersection between the nitrogen polar surface and the M surface. The production method according to any one of [29] to [37] above, wherein the mask is arranged.
[41] The production method according to any one of [25] to [40], wherein in the third step, a void is formed between the GaN crystal and the pattern mask.
[42] The manufacturing method according to [41], wherein in the third step, a GaN crystal is grown so that no through hole remains above the non-opening portion of the pattern mask.
[43] The above-mentioned [25] to [42], wherein the mineralizing agent used in the third step contains one or more ammonium halides selected from NH ₄ Cl, NH ₄ Br and NH ₄ I, and NH ₄ F. ] The manufacturing method according to any one of.
[44] The production method according to the above [43], wherein the mineralizing agent used in the third step contains NH ₄ I and NH ₄ F.
[45] The production method according to any one of [25] to [44], wherein the GaN crystal contains F and I.
[46] The above-mentioned [25] to [45], wherein the sizes of the GaN seeds in the [1-100] direction, the [10-10] direction, and the [01-10] direction are all 45 mm or more. Manufacturing method.
[47] The above-mentioned [25] to [46], wherein the size of the GaN crystal in the [1-100] direction, the [10-10] direction, and the [01-10] direction is 45 mm or more. Manufacturing method.
[48] The [1-100] direction, the [10-10] direction, and [01-] of the C-plane GaN substrate.
10] The manufacturing method according to any one of [25] to [47] above, wherein the size in each of the directions is 45 mm or more.
[49] The production method according to any one of [25] to [48], wherein the fourth step includes a sub-step of slicing the GaN crystal in parallel or substantially parallel to the C plane.

According to one embodiment, a novel C-plane GaN substrate that can be preferably used for manufacturing a nitride semiconductor device, a bulk nitride semiconductor crystal, or the like is provided.
According to another embodiment, a novel method for manufacturing a C-plane GaN substrate is provided.

1A and 1B show a shape example of a C-plane GaN substrate according to an embodiment, FIG. 1A is a perspective view, and FIG. 1B is a side view. 2 (a) to 2 (c) are perspective views showing shapes that the C-plane GaN substrate according to the embodiment can have, respectively. FIG. 3 is a plan view of the C-plane GaN substrate according to the embodiment. FIG. 4 is a flowchart of the C-plane GaN substrate manufacturing method according to the embodiment. FIG. 5A is a perspective view showing the GaN seed, and FIG. 5B is a perspective view showing the GaN seed after the pattern mask is placed on the nitrogen polar surface. FIG. 6 is a plan view showing a part of the nitrogen polar surface side of the GaN seed after the pattern mask is arranged. FIG. 7 is a plan view showing a part of the nitrogen polar surface side of the GaN seed after the pattern mask is arranged. 8 (a) to 8 (d) are plan views of GaN seeds in which a pattern mask is arranged on a nitrogen polar surface, respectively. 9 (e) to 9 (h) are plan views of GaN seeds in which a pattern mask is arranged on a nitrogen polar surface, respectively. 10 (i) to 10 (l) are plan views of GaN seeds in which a pattern mask is arranged on a nitrogen polar surface, respectively. 11 (a) to 11 (f) are plan views showing a part of the pattern mask arranged on the nitrogen polar surface of the GaN seed, respectively. 12 (a) to 12 (f) are plan views showing a part of the pattern mask arranged on the nitrogen polar surface of the GaN seed, respectively. 13 (a) to 13 (e) are cross-sectional views showing a process in which a GaN crystal grows. FIG. 14 (a) is a plan view showing a part of the nitrogen polar surface side of the GaN seed after the pattern mask in which the linear openings form a continuous intersection is arranged, and FIG. 14 (b) is a plan view. , FIG. 14A is a plan view showing a GaN crystal in the initial growth stage grown through the pattern mask shown in FIG. 14 (a). FIG. 15 (a) is a plan view showing a part of the GaN seed on the nitrogen polar surface side after the pattern mask in which the linear openings form discontinuous intersections is arranged. FIG. 15 (b) is shown in FIG. Is a plan view showing a GaN crystal in the initial growth stage grown through the pattern mask shown in FIG. 15 (a). FIG. 16 shows a crystal growth apparatus that can be used for growing a GaN crystal by the amonothermal method. 17 (a) and 17 (b) are cross-sectional views showing positions for slicing a GaN crystal, respectively.

In a GaN crystal, the crystal axis parallel to [0001] and [000-1] is the c-axis, <10-
The crystal axis parallel to <10> is called the m-axis, and the crystal axis parallel to <11-20> is called the a-axis. The crystal plane orthogonal to the c-axis is called the C-plane, the crystal plane orthogonal to the m-axis is called the M-plane, and the crystal plane orthogonal to the a-axis is called the A-plane.
In the following, when the crystal axis, crystal plane, crystal orientation, etc. are referred to, they mean the crystal axis, crystal plane, crystal orientation, etc. of the GaN crystal unless otherwise specified.
Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate.

1. 1. C-plane GaN substrate One embodiment of the present invention relates to a C-plane GaN substrate.
1.1. Shape and Size The C-plane GaN substrate of the embodiment has the shape of a plate with a main surface on one side and a main surface on the opposite side, the thickness direction of which is parallel to or substantially parallel to the c-axis. .. One of the two main surfaces is a gallium polar surface and the other is a nitrogen polar surface. The shape of the main surface is not particularly limited.
FIG. 1 illustrates the shape of the C-plane GaN substrate of the embodiment, FIG. 1A is a perspective view, and FIG. 1B is a side view.
Referring to FIG. 1, the C-plane GaN substrate 10 has a disk shape, and the shapes of the gallium polar surface 11 which is the main surface on the [0001] side and the nitrogen polar surface 12 which is the main surface on the [000-1] side. Is circular. The gallium polar surface 11 and the nitrogen polar surface 12 are connected via a side surface 13.

2 (a) to 2 (c) are perspective views illustrating other shapes that the C-plane GaN substrate of the embodiment may have, respectively. In FIG. 2, the configurations corresponding to those shown in FIG. 1 are designated by the same reference numerals as those in FIG. 1 (the same applies to FIG. 3 described later).
In FIGS. 2A to 2C, the shapes of the main surfaces (gallium polar surface 11 and nitrogen polar surface 12) of the C-plane GaN substrate 10 are quadrangular, hexagonal, and octagonal, respectively.
Area of the main surface having the C-plane GaN substrate according to the embodiment, preferably at 15cm ² or more, 15cm ² 50cm or more than ^2, 50cm ² or more 100cm less than ^2, 100cm ² or more 200cm less than ^2, 200cm ² or more 350 cm ² less, 350 cm ² or more 500cm less than ^2, and the like 500cm ² or more 750cm less than ^2.

In the C-plane GaN substrate of the embodiment, the orientation of the gallium polar surface is within 10 ° from [0001]. This means that the angle formed by the normal vector of the gallium polar surface with [0001] is within 10 °.
When the normal vector of the gallium polar surface is tilted from [0001], the preferred tilting direction is within ± 10 ° from either the m-axis direction or the a-axis direction, but is not limited.
In the C-plane GaN substrate of the embodiment, the orientation of the gallium polar surface is preferably within 5 ° from [0001], more preferably within 2 °, and may be within 1 °. In the C-plane GaN substrate of the embodiment, the orientation of the nitrogen polar surface is within 10 ° from [000-1], preferably within 5 °, more preferably within 2 °, and within 1 °. It may be.
When the normal vector of the nitrogen polar surface is inclined from [0001], the preferable inclination direction is within ± 10 ° from either the m-axis direction or the a-axis direction, but is not limited.
Without limitation, the gallium polar surface and the nitrogen polar surface are preferably parallel to each other.

When the C-plane GaN substrate of the embodiment has a disk shape, its diameter is preferably 45 mm or more and 305 mm or less. The diameters are typically 45-55 mm (about 2 inches), 95-105 mm (about 4 inches), 145-155 mm (about 6 inches), 195-205 mm (about 8 inches), 295-305 mm (about). 12 inches) and so on.
When the C-plane GaN substrate of the embodiment has a rectangular main surface, the vertical and horizontal sizes of the main surface are preferably 5 cm or more, and 15 cm or less.
The thickness of the C-plane GaN substrate according to the embodiment is preferably 100 μm or more, 150 μm or more and less than 250 μm, 250 μm or more and less than 300 μm, 300 μm or more and less than 400 μm, 400 μm or more and less than 500 μm, 500 μm or more and less than 750 μm, 750 μm or more and less than 1 mm. It can be 1 mm or more and less than 2 mm, 2 mm or more and less than 5 mm, and the like. There is no particular upper limit to the thickness, but it is usually 20 mm or less.

In the C-plane GaN substrate of the embodiment, the boundary between the gallium polar surface and the side surface may be chamfered. The same applies to the boundary between the nitrogen polar surface and the side surface.
The C-plane GaN substrate according to the embodiment is marked with various markings as necessary, such as an orientation flat or notch for displaying the crystal orientation, and an index flat for facilitating the distinction between the gallium polar surface and the nitrogen polar surface. Can be provided.

1.2. Crystalline The first line segment, which is a virtual line segment having a length of 40 mm, satisfies at least one of the following conditions (A1) and (B1), preferably both, on the main surface of the C-plane GaN substrate according to the embodiment. You can subtract at least one minute.
(A1) On the first line segment, when the X-ray incident surface at each ω scan is parallel to the first line segment and (004) the XRC of reflection is measured at 1 mm intervals, between all measurement points. The maximum value of FWHM of XRC is less than 30 arcsec.
(B1) On the first line segment, when the X-ray incident surface at each ω scan is parallel to the first line segment and (004) the XRC of reflection is measured at 1 mm intervals, between all measurement points. The difference between the maximum value and the minimum value of the peak angle of XRC is less than 0.2 °.

The XRC here is an X-ray locking curve (or an X-ray diffraction locking curve). In XRC measurement of GaN crystals, CuKα is usually used as a radiation source.
The FWHM (Full Width at Half Maximum) of XRC is an index generally used in the quality evaluation of crystals.
The difference between the maximum value and the minimum value of the peak angle of XRC referred to in the above condition (B1) is an index showing how much the direction of the c-axis fluctuates on the first line segment.

In a preferred example, the first line segment satisfies the following condition (A2) in addition to the above condition (A1).
(A2) The average FWHM of XRC among all the measurement points on the first line segment obtained from the above XRC measurement is less than 20 arcsec.
In a more preferable example, the first line segment satisfies the following condition (A3) in addition to the above condition (A1).
(A3) The mean and standard deviation of the FWHM of XRC among all the measurement points on the first line segment obtained from the XRC measurement are less than 12 arcsec and less than 5 arc sec, respectively.

In the C-plane GaN substrate of the embodiment, the first line segment may be drawn on at least one of a gallium polar surface and a nitrogen polar surface. In some cases, one of the main surfaces is roughened and may not be suitable for XRC measurements. In a substrate in which both main surfaces are XRC-measurable, if a first line segment can be drawn on one main surface, it is often possible to draw a first line segment on the other main surface as well.
It is desirable, but not limited to, that at least one of the first line segments that can be drawn on the main surface of the C-plane GaN substrate according to the embodiment passes through the center (center of gravity) of the main surface.

In the C-plane GaN substrate of the embodiment, a virtual line having a length of 40 mm, which satisfies at least one of the following conditions (C1) and (D1), preferably both, on the main surface on which the first line segment can be drawn. It is desirable to be able to draw at least one second line segment, which is a minute.
(C1) The second line segment is orthogonal to at least one of the first line segments, and the X-ray incident surface at each ω scan is made parallel to the second line segment on the second line segment. (004) When the reflection XRC is measured at 1 mm intervals, the maximum value of the XRC FWHM between all the measurement points is less than 30 arcsec.
(D1) The second line segment is orthogonal to at least one of the first line segments, and the X-ray incident surface at each ω scan is made parallel to the second line segment on the second line segment. (004) When the reflection XRC is measured at 1 mm intervals, the difference between the maximum value and the minimum value of the XRC peak angle among all the measurement points is less than 0.2 °.

In a preferred example, the second line segment satisfies the following condition (C2) in addition to the above condition (C1).
(C2) The average FWHM of XRC among all the measurement points on the second line segment obtained from the above XRC measurement is less than 20 arcsec.
In a more preferable example, the second line segment satisfies the following condition (C3) in addition to the above condition (C1).
(C3) The mean and standard deviation of the FWHM of XRC between all the measurement points on the second line segment obtained from the above XRC measurement are less than 12 arcsec and less than 5 arc sec, respectively.
It is desirable, but not limited to, that at least one of the second line segments that can be drawn on the main surface of the C-plane GaN substrate of the embodiment passes through the center (center of gravity) of the main surface.

FIG. 3 shows an example of a C-plane GaN substrate capable of drawing two line segments corresponding to the above-mentioned first line segment and second line segment on the main surface.
The C-plane GaN substrate 10 shown in FIG. 3 has a disk shape, and its diameter is in the range of 45 to 55 mm. A line segment LS1 corresponding to the first line segment and a line segment LS2 corresponding to the second line segment can be drawn on the gallium polar surface 11 of the C-plane GaN substrate 10.
The line segment LS1 and the line segment LS2 that are orthogonal to each other have a length of 40 mm and both pass through the substantially center of the gallium polar surface 11. Each of the line segment LS1 and the line segment LS2 intersects the other line segment at its midpoint.

On the line segment LS1, the X-ray incident surface at each ω scan can be made parallel to the line segment LS1 and the reflected XRC can be measured at 1 mm intervals. When the X-ray incident surface is parallel to the line segment LS1, the incident direction of the X-ray with respect to the C-plane GaN substrate 10 is parallel to the plane including the line segment LS1 and perpendicular to the C-plane.
The maximum value of FWHM of XRC between 40 measurement points on the line segment LS1 obtained from such XRC measurement is less than 30 arcsec, preferably less than 25 arcsec, and more preferably less than 20 arcsec.
The average FWHM of the XRC between the 40 measurement points is preferably less than 20 arcsec, more preferably less than 16 arcsec, and more preferably less than 12 arcsec.
More preferably, the FWHM mean and standard deviation of the XRC between the 40 measurement points is less than 12 arcsec and less than 5 arcsec, respectively.
The difference between the maximum value and the minimum value of the XRC peak angle between the 40 measurement points is preferably less than 0.2 °, more preferably less than 0.15 °, and more preferably less than 0.1 °. ..

On the line segment LS2, the X-ray incident surface at each ω scan is made parallel to the line segment LS2, and the reflected XRC-FWHM can be measured at 1 mm intervals. When the X-ray incident surface is parallel to the line segment LS2, the incident direction of the X-ray with respect to the C-plane GaN substrate 10 is parallel to the plane including the line segment LS2 and perpendicular to the C-plane.
The maximum value of FWHM of XRC between 40 measurement points on the line segment LS2 obtained from such XRC measurement is less than 30 arcsec, preferably less than 25 arcsec, and more preferably less than 20 arcsec.
The average FWHM of the XRC between the 40 measurement points is preferably less than 20 arcsec, more preferably less than 16 arcsec, and more preferably less than 12 arcsec.
More preferably, the FWHM mean and standard deviation of the XRC between the 40 measurement points is less than 12 arcsec and less than 5 arcsec, respectively.
The difference between the maximum value and the minimum value of the XRC peak angle between the 40 measurement points is preferably less than 0.2 °, more preferably less than 0.15 °, and more preferably less than 0.1 °. ..

1.3. The C-plane GaN substrate according to the dislocation array embodiment may have a group of dislocations arranged linearly, that is, a dislocation array on the main surface. The dislocation referred to here is an end point of a through dislocation (blade dislocation, spiral dislocation, and mixed dislocation).
A plurality of dislocation arrays may be periodically arranged on the main surface of the C-plane GaN substrate according to the embodiment. The arrangement of the plurality of dislocation arrays may be two-dimensional and may have periodicity in two or more directions.
The presence, shape, arrangement, etc. of dislocation arrays on the main surface of the C-plane GaN substrate can be confirmed with an optical microscope by etching the main surface under appropriate conditions and forming etch pits at the end points of through-dislocations. It is possible. Confirmation may be performed on at least one of the gallium polar surface and the nitrogen polar surface.
For example, in the case of a gallium polar surface, etching is performed for 1 hour or more using 89% sulfuric acid heated to 270 ° C. to form etch pits corresponding to all kinds of penetrating dislocations existing on the surface. be able to.
The C-plane GaN substrate according to the embodiment may have a plurality of dislocation arrays periodically arranged on the main surface, for example, in the production of the C-plane GaN substrate, which will be described later. When the C-plane GaN substrate manufacturing method described in the above section is used, or the GaN seed used for manufacturing the GaN substrate is described later in 2. This is the case where the product is manufactured by the method for manufacturing a C-plane GaN substrate according to the above item.

1.4. Impurities The concentration of various impurities in a GaN crystal is determined by SIMS (Secondary Ion Mass Spectrometry).
) Is generally used. The impurity concentration referred to below is a value measured by SIMS at a depth of 1 μm or more from the crystal surface.
The C-plane GaN substrate of the embodiment is NH ₄ F, NH ₄ Cl (ammonium chloride), NH ₄ Br.
Ammonium halide such as (ammonium bromide) and NH ₄ I with the mineralizing agents, preferably ammonothermally to the grown GaN crystal in the capsule made of Pt (platinum). In such GaN crystals, alkali metals such as Li (lithium), Na (sodium) and K (potassium) and alkaline earth metals such as Mg (magnesium) and Ca (calcium) are used unless intentionally added. Concentration of each element can be less than 1 × 10 ¹⁶ atoms / cm ³ .

A GaN crystal grown amonothermally using ammonium halide as a mineralizing agent may contain halogens derived from the mineralizing agent. For example, a GaN crystal grown by the amonothermal method using NH ₄ F as a mineralizing agent is 5 × 10 ¹⁴ atoms / cm ³ or more and 1 × 10 ^1
6 F (fluorine) may be contained at a concentration such as less than ⁶ atoms / cm ³ and 1 × 10 ¹⁶ atoms / cm ³ or more and 1 × 10 ¹⁷ atoms / cm ^{3 or} less.
As confirmed by the present inventors in experiments, the concentration of I (iodine) in a GaN crystal grown amonothermally using NH ₄ F and NH ₄ I as mineralizing agents is usually 1. × 10 ¹⁶ atoms / cm ^{3 or} less.

A GaN crystal grown amonothermally using ammonium halide as a mineralizing agent can contain H (hydrogen) at a concentration of 5 × 10 ¹⁷ atoms / cm ³ or higher. The hydrogen concentration in such a GaN crystal is usually 10 ²¹ atoms / cm ³ or less, 5 × 10 ²⁰ atoms / cm ³ or less, 1 × 10 ²⁰ atoms / cm ³ or less, or 5 × 10 ¹⁹ atoms / cm ³ or less. possible.
GaN crystals grown in an amonothermal manner generally have an infrared absorption peak attributable to the gallium vacancy-hydrogen complex of 3140 to 3200c.
It has in m ^-1 . In the GaN crystal grown by the HVPE method or the Na flux method, such an infrared absorption peak is not observed.

1.5. Applications (1) Nitride semiconductor device The C-plane GaN substrate of the embodiment can be preferably used for manufacturing a nitride semiconductor device.
Usually, one or more nitride semiconductors are epitaxially grown on a C-plane GaN substrate to form an epitaxial substrate having a device structure. As the epitaxial growth method, a vapor phase method such as a MOCVD method, an MBE method, or a pulse vapor deposition method suitable for forming a thin film can be preferably used, but is not limited.
The device structure is formed on the main surface from which the aforementioned front line segment can be drawn.
After the semiconductor process is performed, including etching and the application of structures such as electrodes and protective films, the epitaxial substrate is fragmented into nitride semiconductor device chips.

Specific examples of the nitride semiconductor device that can be manufactured using the C-plane GaN substrate of the embodiment include a light emitting device such as a light emitting diode and a laser diode, a rectifier, a bipolar transistor, a field effect transistor, and HEMT (High Electron Mobility Transistor). Electronic devices, temperature sensors, pressure sensors, radiation sensors, semiconductor sensors such as visible-ultraviolet photodetectors, solar cells, and the like.
In addition, the C-plane GaN substrate of the embodiment is a SAW (Surface Acoustic Wave) device,
It can also be applied to applications such as oscillators, resonators, oscillators, MEMS (Micro Electro Mechanical System) components, voltage actuators, and electrodes for artificial photosynthesis devices.

(2) The C-plane GaN substrate of the seed embodiment can be preferably used for producing a bulk nitride semiconductor crystal, particularly a bulk GaN crystal.
Specifically, in the growth of bulk nitride semiconductor crystals by various methods, the C-plane GaN substrate of the embodiment can be used as a seed.
Bulk nitride semiconductor crystal growth methods include the HVPE (Hydlide Vapor Phase Epitaxy) method, the Amonothermal method, and the Na flux method, as well as the THVPE (Tri-Halide Vapor Phase Epitaxy) method and OVPE (Oxide Vapor Phase Epitaxy). The method and the like can also be preferably used.
The THVPE method is a vapor phase growth method for nitride semiconductor crystals using trichloride of a Group 13 element such as GaCl ₃ and a nitrogen-containing compound such as NH ₃ as raw materials. WO2015 / 037232 can be referred to. In the production of a bulk GaN crystal using the THVPE method, the GaN crystal is epitaxially grown on the nitrogen-polar surface of the C-plane GaN substrate of the embodiment.
The OVPE method is a vapor deposition method for GaN using Ga ₂ O and NH ₃ as raw materials. For details, refer to, for example, M. Imade, et al., Journal of Crystal Growth, 312 (2010) 676-679. Can be referred to.

(3) GaN Layer Bonded Substrate In one example, the C-plane GaN substrate of the embodiment can be used to manufacture a GaN layer bonded substrate.
The GaN layer bonded substrate is a composite substrate having a structure in which a GaN layer is bonded to a different composition substrate having a chemical composition different from that of GaN, and can be used for manufacturing a light emitting device or other semiconductor device. The different composition substrates include sapphire substrate, AlN substrate, SiC substrate, ZnSe substrate, Si substrate, ZnO substrate, ZnS substrate, quartz substrate, spinel substrate, carbon substrate, diamond substrate, Ga ₂ O ₃ substrate, ZrB ₂ substrate, and Mo. Examples thereof include a substrate, a W substrate, and a ceramics substrate.
For details of the structure, manufacturing method, application, etc. of the GaN layer bonding substrate, JP-A-2006-210660, JP-A-2011-44665, and the like can be referred to.

The GaN layer bonding substrate typically has a boundary between a step of implanting ions near the main surface of the GaN substrate, a step of bonding the main surface side of the GaN substrate to a different composition substrate, and an ion-implanted region. As a result, the GaN substrate is separated into two portions to form a GaN layer bonded to the different composition substrate, which is carried out in this order.
As a method for manufacturing a GaN layer-bonded substrate without ion implantation, there is also a method in which a GaN substrate is bonded to a heterogeneous substrate and then the GaN substrate is mechanically cut to form a GaN layer bonded to the heterogeneous substrate. It is being developed.
Regardless of which method is used, when the C-plane GaN substrate of the embodiment is used as the material, the GaN layer-bonded substrate having a structure in which the GaN layer separated from the C-plane GaN substrate is bonded to the heterogeneous substrate. Is obtained.

2. 2. C-plane GaN substrate manufacturing method One embodiment of the present invention relates to a C-plane GaN substrate manufacturing method.
A flowchart of the C-plane GaN substrate manufacturing method according to the embodiment is shown in FIG. This method includes the following steps S1 to S3 that are sequentially executed.
S1: A step of preparing a GaN seed having a nitrogen polar surface.
S2: A step of arranging the pattern mask on the nitrogen-polar surface of the GaN seed prepared in step S1.
S3: A step of amonothermally growing a GaN crystal on the nitrogen-polar surface of the GaN seed prepared in step S1 through a pattern mask arranged in step S2.
S4: A step of processing the GaN crystal grown in step S3 to obtain a C-plane GaN substrate.
The details of steps S1 to S4 will be described below.

(1) Step S1
In step S1, a GaN seed having a nitrogen polar surface is prepared.
A preferred GaN seed is a C-plane GaN substrate obtained by processing a bulk GaN crystal grown by the HVPE method or the acidic amonothermal method. It may be manufactured by the method described in the section. In the C-plane GaN substrate, the main surface on the [0001] side is a gallium polar surface, and the main surface on the [000-1] side is a nitrogen polar surface.
The orientation of the nitrogen polar surface of the GaN seed is preferably within 2 ° from [000-1], more preferably within 1 ° from [000-1].
Area of the N-polar surface of the GaN seed is preferably not 15cm ² or more, 15cm ² 50cm or more than ^2, 50cm ² or more 100cm less than ^2, 100cm ² or more 200cm less than ^2,
200 cm ² or more 350cm less than ^2, 350cm ² or more 500cm less than ^2, and the like 500cm ² or more 750cm less than ^2.

When the nitrogen polar surface of the GaN seed is circular, its diameter is preferably 45 mm or more. The diameters are typically 45-55 mm (about 2 inches), 95-105 mm (about 4 inches), 145-155 mm (about 6 inches), 195-205 mm (about 8 inches), 295-305 mm (about). 12 inches) and so on.
For example, when the GaN seed is a C-plane GaN substrate having a diameter of 50 mm, the thickness thereof is preferably 300 μm or more, and if the diameter is larger than this, the preferable lower limit value of the thickness is also larger. There is no particular upper limit to the thickness of the GaN seed, but it is usually 20 mm or less.

The size of the GaN seed is determined in consideration of the size of the GaN crystal to be grown in the later step S3.
For example, when trying to cut out a C-plane GaN substrate having a size of 45 mm in each of the [1-100] direction, the [10-10] direction, and the [01-10] direction from the GaN crystal to be grown, the GaN crystal It is necessary to grow the crystals so that the sizes in the [1-100] direction, the [10-10] direction, and the [01-10] direction are all 45 mm or more. To grow a GaN crystal having a size of 45 mm in each of the [1-100] direction, the [10-10] direction, and the [01-10] direction, the GaN seed is used in the [1-100] direction, [10-]. It is preferable to use one having a size of 45 mm or more in both the [10] direction and the [01-10] direction.
The nitrogen polar surface of the GaN seed is usually flattened by polishing or grinding. Preferably, by CMP (Chemical Mechanical Polishing) and / or etching, the damaged layer introduced by the flattening process is removed from the nitrogen polar surface.

(2) Step S2
In step S2, the pattern mask is placed on the nitrogen-polar surface of the GaN seed prepared in step S1.
The material forming the surface of the pattern mask is preferably a platinum group metal, namely a metal selected from Ru (ruthenium), Rh (rhodium), Pd (palladium), Os (osmium), Ir (iridium) and Pt (platinum). It is particularly preferably Pt (platinum). The pattern mask may be a single-layer film made of a platinum group metal or an alloy thereof, but preferably a platinum group as a surface layer on an underlayer made of a metal having better adhesion to a GaN crystal than a platinum group metal. It is a multilayer film formed by laminating metal layers. Examples of the material of the base layer include, but are not limited to, W (tungsten), Mo (molybdenum), Ti (titanium), and alloys containing one or more selected from these.

The pattern mask is provided with a periodic opening pattern composed of linear openings. An example will be described with reference to FIGS. 5 and 6.
FIG. 5A is a perspective view showing a GaN seed. The GaN seed 20 is a disk-shaped C-plane GaN substrate, which has a gallium-polarized surface 21, a nitrogen-polarized surface 22, and side surfaces 23.
FIG. 5B is a perspective view showing the GaN seed 20 after the pattern mask 30 is formed on the nitrogen polar surface 22. The pattern mask 30 is provided with a plurality of linear openings 31 arranged in parallel with each other. The periodic opening pattern formed by the linear opening 31 is a stripe pattern.
FIG. 6 is a plan view showing a part of the GaN seed 20 on the nitrogen polar surface 22 side after the pattern mask 30 is arranged.
Referring to FIG. 6, a plurality of linear openings 31 are provided in parallel to each other at a constant pitch P in the pattern mask 30, and the nitrogen polar surface 22 of the GaN seed is exposed inside each linear opening. Pitch means the distance between the center lines between parallel linear openings adjacent to each other across the non-opening of the pattern mask.

In order to reduce the dislocation defects that the GaN crystal grown in the subsequent step S3 inherits from the GaN seed 20, it is advantageous that the line width W of the linear opening 31 is narrow. Therefore, the line width W is preferably 0.5 mm or less, more preferably 0.2 mm or less, and even more preferably 0.1 mm or less.
From the viewpoint of manufacturing efficiency, it is preferable that the line width W of the linear opening 31 is appropriately wide. This is because the growth rate in the initial stage becomes higher when the GaN crystal grows in the later step S3. Therefore, the line width W is preferably 5 μm or more, more preferably 20 μm or more, and more preferably 40 μm or more.
In order to reduce the dislocation defects that the GaN crystal grown in the later step S3 inherits from the GaN seed 20, it is advantageous that the pitch P between the linear openings 31 is large. Therefore, the pitch P is preferably 1 mm or more, more preferably 2 mm or more, more preferably 3 mm or more, and more preferably 4 mm or more.

The larger the pitch P between the linear openings 31, the longer it takes for the through hole generated above the non-opening portion of the pattern mask to close when the GaN crystal is grown in the later step S3. Therefore, from the viewpoint of manufacturing efficiency, the pitch P is preferably 10 mm or less, and can be 4 mm or less, 3 mm or less, and further 2 mm or less.
When the direction of intersection between the nitrogen polar surface 22 and the M plane [(1-100) plane, (10-10) plane or (01-10) plane] in the GaN seed 20 is used as the reference direction, the linear opening 31 The angle θ formed by the longitudinal direction and the reference direction is preferably 12 ° ± 5 °. The angle θ may be 12 ° ± 3 °, 12 ° ± 2 ° or 12 ° ± 1 °. When the linear openings are oriented in this way, when the GaN crystal is grown in the later step S3, the through holes generated above the non-openings of the pattern mask are likely to be closed.

The pattern mask may be composed of linear openings and may be provided with a periodic opening pattern including intersections. An example will be described with reference to FIG.
FIG. 7 is a plan view showing a part of the GaN seed 20 on the nitrogen polar surface 22 side after the pattern mask 30 is formed.
The pattern mask 30 is provided with a linear opening 31, and the nitrogen polar surface 22 of the GaN seed is exposed inside the linear opening 31.
There are two types of linear openings provided in the pattern mask 30, that is, a first linear opening 311 and a second linear opening 312 having different longitudinal directions. A square lattice pattern is formed by the plurality of the first linear openings 311 and the plurality of the second linear openings 312.
The pitch P ₁ between the first linear openings 311 and the pitch P ₂ between the second linear openings 312 are constant. The pitch means the distance between the center lines of the linear openings parallel to each other, which are adjacent to each other across the non-opening of the pattern mask.
The pitch P ₁ and the pitch P ₂ may be the same, but as the present inventors have empirically found, if the pitch P ₁ and the pitch P ₂ are different, the GaN is performed in a later step S3. When the crystal is grown, the through hole formed above the non-opening of the pattern mask tends to be easily closed. Therefore, _{one of the} pitches P ₁ and P ₂ is preferably 1.5 times or more of the other, and more preferably 2 times or more.

The square grid pattern provided on the pattern mask 30 includes an intersection K formed between the first linear opening 311 and the second linear opening 312. As will be described later, providing the intersection in the opening pattern is advantageous in promoting the closing of the through hole generated above the non-opening of the pattern mask when the GaN crystal is grown in the later step S3. .. From this point of view, the number density of the intersections included in the pattern mask is preferably 1 cm- ² or more.
On the other hand, in order to increase the number density of intersections, it is necessary to increase the density of linear openings.
Then, considering that the dislocation defects that the GaN crystal growing in the later step S3 inherits from the GaN seed increases as the density of the linear openings increases, the number density of the intersections is preferably 20 cm- ² or less, and more. It is preferably 15 cm ^-2 or less, more preferably 10 cm ^-2 or less.

Regarding the orientation of the first linear opening 311 and the second linear opening 312, it is convenient to represent one of the directions of intersections between the nitrogen polar surface 22 and the M surface as the first reference direction and the other as the second reference direction. Is. For example, when the first reference direction is the direction of line of intersection between the nitrogen polar surface 22 and the (1-100) plane, the second reference direction is the nitrogen polarity with the (10-10) plane or the (01-10) plane. This is the direction of intersection with the surface 22.
In one preferred embodiment, the angle theta ₁ which the longitudinal direction of the first linear opening 311 forms a first reference direction, the angle theta ₂ which the longitudinal direction of the second linear opening 312 is formed with the second reference direction, at least One can be 12 ° ± 5 °.
When the total length of the first linear opening 311 is equal to or greater than the total length of the second linear opening 312, it is preferable that the angle θ ₁ is at least 12 ° ± 5 °. In other words, the longitudinal direction at 50% or more of the total length of the linear opening 31 may be at an angle of 12 ° ± 5 ° with respect to the direction of intersection between the nitrogen-polar surface of the GaN seed and the M-plane. preferable.
In a more preferred example, both the angle θ ₁ and the angle θ ₂ are 12 ± 5 °, that is, the longitudinal direction in all parts of the linear opening 31 is the direction of line of intersection between the nitrogen polar surface of the GaN seed and the M plane. The angle is 12 ± 5 °.
The angles θ ₁ and θ ₂ may be 12 ± 3 °, 12 ± 2 °, and 12 ± 1 °.
When the linear openings are oriented as described above, the through holes generated above the non-openings of the pattern mask when the GaN crystal is grown in the later step S3 are likely to be closed.

It does not prevent one or both of the angles θ ₁ and θ _{2 from being} less than 7 °. In one example, either or both of the angles θ ₁ and θ ₂ may be ± 3 °, ± 2 °, ± 1 °, and the like. According to what the present inventors have found, when the longitudinal direction of the linear opening is oriented substantially parallel to the M plane of the GaN seed, when the GaN crystal is grown in the subsequent step S3, it penetrates in the crystal. The effect is that the dislocations are bent in the lateral direction.
The angle θ ₁₂ formed by the first linear opening and the second linear opening may be, for example, 30 ° or more and less than 45 °, 45 ° or more and less than 75 °, or 75 ° or more and 90 ° or less. The angle θ ₁₂ may be 60 ° ± 10 °, 60 ° ± 5 °, 60 ° ± 3 °, 60 ° ± 1 °, or the like.

For GaN crystal grown in step S3 a later reduce the dislocation defect to take over from the GaN seed 20, better line width W ₂ of the line width W ₁ and the second linear opening 312 of the first linear opening 311 is narrower It is advantageous. Therefore, the line widths W ₁ and W ₂ are preferably 0.5 mm or less, more preferably 0.2 mm or less, and more preferably 0.1 mm or less, respectively.
From the viewpoint of production efficiency, the line width W ₂ of the line width W ₁ and the second linear opening 312 of the first linear opening 311 preferably has reasonably wide. This is because the growth rate in the initial stage becomes higher when the GaN crystal grows in the later step S3. Therefore, the line widths W ₁ and W ₂ are preferably 5 μm or more, more preferably 20 μm or more, and more preferably 40 μm or more, respectively.

In order to reduce the dislocation defects that the GaN crystal grown in the later step S3 inherits from the GaN seed 20, the pitch P ₁ between the first linear openings 311 and the pitch P ₂ between the second linear openings 312 should be larger. It is advantageous. Therefore, the pitches P ₁ and P ₂ are preferably 1 mm or more, more preferably 2 mm or more, more preferably 3 mm or more, and more preferably 4 mm or more.
The larger the pitches P ₁ and P _{2, the} longer the time required for the through hole generated above the non-opening portion of the pattern mask to close when the GaN crystal is grown in the later step S3. Therefore, from the viewpoint of manufacturing efficiency, it is preferable that at least one of the pitches P ₁ and P ₂ is 10 mm or less. In one example, one or both of the pitches P ₁ and P ₂ may be 4 mm or less, 3 mm or less, and further 2 mm or less.
In a preferred embodiment, reduction of dislocation defects taken over in consideration of both the production efficiency, less 4mm only either one of the pitch P ₁ and P _2, it can be less than 3mm or 2mm or less.

The periodic aperture pattern that can be provided in the pattern mask arranged on the nitrogen polar surface of the GaN seed in step S2 is not limited to the above-mentioned stripe pattern or square grid pattern.
Each of the drawings included in FIGS. 8 to 10 is a plan view of the GaN seed 20 after the pattern mask 30 is arranged on the nitrogen polar surface 22, exemplifying various periodic opening patterns that can be provided in the pattern mask. However, the opening patterns that can be adopted are not limited to these.
In FIG. 8A, the linear openings 31 form a zigzag stripe opening pattern.
In FIG. 8B, the linear openings 31 form a kind of lattice pattern.
In FIG. 8C, the linear opening 31 forms an inclined brick lattice pattern.
In FIG. 8D, the linear openings 31 form an inclined square lattice pattern.

In FIG. 9E, the linear openings 31 form a herringbone grid pattern.
In FIG. 9 (f), the linear opening 31 forms a lattice pattern in which an inclined brick lattice and an inclined square lattice are eclectic.
In FIG. 9 (g), the linear openings 31 form a triangular lattice pattern.
In FIG. 9 (h), the linear openings 31 form a flat honeycomb lattice pattern.

In FIG. 10 (i), the linear openings 31 form the Bishamon hexagonal lattice pattern.
In each of FIGS. 10 (j) and 10 (k), the linear openings 31 form a cubic pattern.
In FIG. 10 (l), the linear openings 31 form a Y-shaped pattern.

In any of the examples shown in FIGS. 8 to 10, the periodic opening pattern of the pattern mask 30 includes an intersection. Some types of intersections are shown in FIGS. 11 (a) to 11 (f) and FIGS. 12 (a) to 12 (f).
An intersection in which two or more linear openings having different longitudinal directions are connected, including those shown in FIGS. 11A to 11F, is referred to as a continuous intersection in the present specification.
Unless otherwise specified, the intersection referred to in the present specification includes not only a continuous intersection but also a discontinuous intersection illustrated in FIGS. 12 (a) to 12 (f). A discontinuous intersection can be regarded as an intersection made by modifying the continuous intersection to disconnect the connection between the linear openings.
The distance between two linear openings separated by a non-opening at a discontinuous intersection is 300 μm or less, preferably 200 μm or less.

In FIGS. 8 to 10, in all the examples except FIG. 8 (b), the arrangement of the intersections included in the periodic opening pattern is two-dimensional.
When the periodic opening pattern includes the intersection, the through hole generated above the non-opening of the pattern mask when the GaN crystal is grown in the later step S3 is likely to be closed. This effect is remarkable when the arrangement of the intersections in the periodic opening pattern is two-dimensional, and further becomes more remarkable by increasing the number density of the intersections.
From this, the arrangement of the intersections in the periodic opening pattern is preferably two-dimensional, and the number density of the intersections included in the pattern mask at that time is preferably 1 cm- ² or more. However, in order to increase the number density of the intersections, it is necessary to increase the density of the linear openings, and as the density of the linear openings is increased, the GaN crystal grown in the later step S3 inherits from the GaN seed. Considering the increase in dislocation defects, the number density of the intersection is preferably 20 cm ^-2 or less, more preferably 15 cm ^-2 or less, and more preferably 10 cm ^-2 or less.

Preferred designs for the orientation, line width and pitch of the linear aperture when the various periodic aperture patterns shown in FIGS. 8 to 10 are provided in the pattern mask are as follows.
At least a part of the linear opening preferably has a longitudinal direction at an angle of 12 ± 5 ° with respect to the direction of intersection of the nitrogen polar surface of the GaN seed and the M plane. More preferably, in the portion occupying 50% or more of the total length of the linear opening, and further in all the portions of the linear opening, the longitudinal direction is the line of intersection between the nitrogen polar surface of the GaN seed and the M surface. It is to make an angle of 12 ± 5 ° with respect to the direction of.
The line width of the linear opening is preferably 0.5 mm or less, more preferably 0.2 mm or less, more preferably 0.1 mm or less, and preferably 5 μm or more. It is more preferably 20 μm or more, and more preferably 40 μm or more. The line width does not have to be the same for all parts of the linear opening.

When the non-openings included in the unit pattern of the pattern mask are all quadrangular or all hexagonal, the following can be said about the pitch between the linear openings.
From the viewpoint of reducing dislocation defects that the GaN crystal grown on the GaN seed inherits from the GaN seed, it is preferable that the pattern mask does not include linear openings arranged at a pitch of less than 1 mm, and is arranged at a pitch of less than 2 mm. It is more preferable not to include the linear openings arranged at a pitch of less than 3 mm, and it is more preferable not to include the linear openings arranged at a pitch of less than 4 mm. ..
On the other hand, from the viewpoint of improving manufacturing efficiency, it is preferable that the pattern mask includes linear openings arranged at a pitch of 10 mm or less, and further, linear openings arranged at a pitch of 4 mm or less, 3 mm or less, or 2 mm or less. It may include an opening.
In consideration of both of the above viewpoints, the pattern mask is provided with linear openings arranged at a pitch of 1 mm or more and 4 mm or less and linear openings arranged at a pitch of more than 4 mm, or has a pitch of 1 mm or more and 3 mm or less. The linear openings arranged in 1 and the linear openings arranged at a pitch of more than 3 mm are provided, or the linear openings arranged at a pitch of 1 mm or more and 2 mm or less and arranged at a pitch of more than 2 mm. A linear opening may be provided. In any of these cases, the pattern mask may be provided with linear openings arranged at a pitch greater than 4 mm.
Among the examples shown in FIGS. 8 to 10, the non-openings included in the unit pattern of the pattern mask are all quadrangular in FIGS. 8 (c) and (d), 9 (e) and (f), and FIG. (J) and (k). In the example of FIG. 9H in which the periodic opening pattern is a flat honeycomb pattern, all the non-openings included in the unit pattern of the pattern mask are hexagonal.

(3) Step S3
In step S3, the GaN crystal is grown amonothermally on the nitrogen-polar surface on the GaN seed prepared in step S1 through the pattern mask arranged in step S2.
The growth process of the GaN crystal in step S3 will be described with reference to FIG.
FIG. 13A is a cross-sectional view showing a state before crystal growth starts. A pattern mask 30 having a linear opening 31 is provided on the nitrogen polar surface 22 of the GaN seed 20.
FIG. 13B shows the GaN crystal 40 starting to grow on the nitrogen polar surface 22 exposed inside the linear opening 31 provided in the pattern mask 30.
After passing through the pattern mask 30, the GaN crystal 40 grows not only in the [000-1] direction but also in the lateral direction (direction parallel to the nitrogen polar surface 22) as shown in FIG. 13 (c), but GaN. A gap G is formed between the crystal 40 and the pattern mask 30. As a result, the orientation disorder of the GaN crystal 40 that may occur due to contact with the pattern mask 30 is suppressed.

At the growth stage shown in FIG. 13 (c), the GaN crystal 40 has a through hole T above the non-opening portion of the pattern mask 30.
As the GaN crystal 40 grows further, the gap G is gradually filled, but not completely filled, and as shown in FIG. 13D, the through hole T is closed with the void V left.
After the through hole T is closed, the GaN crystal 40 is further grown in the [000-1] direction as shown in FIG. 13 (e). It is considered that the stress generated between the GaN seed 20 and the GaN crystal 40 is relaxed by the void V, and thus the strain of the GaN crystal 40 is reduced.
The amount of growth of the GaN crystal 40 in the [000-1] direction after the through hole T is closed is preferably 1 mm or more, more preferably 2 mm or more, more preferably 3 mm or more, and there is no particular upper limit.
Note that, in step S3, the GaN crystal also grows on the gallium polar surface 21 of the GaN seed 20, but is not shown in FIG.

When the through hole T is closed at the stage of FIG. 13D, dislocations occur on the coreless surface, or the dislocations are simultaneously bent in the [000-1] direction on the coreless surface, or both. For this reason, a dislocation array appears on the main surface of the C-plane GaN substrate cut out from the GaN crystal formed at the stage of FIG. 13 (e). The shape of the dislocation array is the shape of the line of intersection formed by the extension surface extending the coreless surface in the [000-1] direction and the main surface of the C surface substrate.
Since the coreless surface is formed on the non-openings of the pattern mask, when the pattern mask has a plurality of closed non-openings, the plurality of dislocation arrays are discrete on the main surface of the C-plane GaN substrate described above. Appears in. When the arrangement of the plurality of closed non-openings in the pattern mask is periodic, the arrangement of the plurality of dislocation arrays on the main surface of the C-plane GaN substrate is also periodic. When the arrangement of the plurality of closed non-openings in the pattern mask is two-dimensional, the arrangement of the plurality of dislocation arrays on the main surface of the above-mentioned C-plane GaN substrate is also two-dimensional.
The closed non-opening is a non-opening surrounded by a linear opening, and among the various examples shown in FIGS. 8 to 10, the non-opening in which the pattern mask is closed is shown in FIG. c) and (d), FIGS. 9 (e) to 9 (h), and FIGS. 10 (i) to 10 (k). In these examples, the arrangement of closed non-openings in the pattern mask is periodic and two-dimensional.

The effect of the orientation of the linear aperture provided on the pattern mask on the growth of the GaN crystal 40 will be described as follows.
According to what the present inventors have learned through experiments, when the opening pattern provided in the pattern mask is a stripe type, the growth of the GaN crystal 40 is most reliable from the stage shown in FIG. 13 (c) to the stage shown in FIG. 13 (d). That is, the through hole T formed in the GaN crystal 40 is most likely to be closed when the longitudinal direction of the linear opening is inclined by about 12 ° with respect to the direction of the line of intersection between the nitrogen polar surface and the M surface. Is. When the inclination is brought close to 0 ° and when the inclination is brought close to 30 °, the through hole T becomes difficult to close.
On the other hand, if the intersection is introduced into the pattern formed by the linear opening 31, the through hole T formed in the GaN crystal 40 is likely to be closed even if the linear opening 31 is parallel to the M plane.
Regarding the reason, the present inventors consider that the recessed angle effect described below is related.

FIG. 14A is a plan view showing a part of the nitrogen polar surface side of the GaN seed in which a pattern mask in which linear openings form intersections is arranged. The pattern mask 30 is provided with a first linear opening 311 and a second linear opening 312 having different longitudinal directions, and a continuous intersection is formed between them.
FIG. 14B shows a state in which the GaN crystal 40 at the growth stage shown in FIG. 13C is formed on the GaN seed shown in FIG. 14A. The GaN crystal 40 grows along the linear opening. Shown by the broken line is the outline of the linear openings 311 and 312 hidden below the GaN crystal 40.
The four arrows in FIG. 14B point to the recesses formed on the sides of the GaN crystal 40 that grow on the intersections formed by the linear openings 311 and 312, respectively. The direction of the arrow indicates the recessing direction of the recessed portion.
The formation of such a recessed portion causes a recessed angle effect (re-entrant angle effect), and Ga
The N crystal 40 is encouraged to grow in the direction opposite to the arrow. That is, the driving force for growing the GaN crystal so as to close the through hole generated above the non-opening of the pattern mask is generated by the recessed angle effect.
In retrospect, when the opening pattern is striped, the reason why the orientation of the linear opening has a dominant effect on the ease of closing the through hole is presumed to be that the recessed angle effect does not occur. ..

A similar mechanism can occur if the linear openings form discontinuous intersections rather than continuous intersections. This will be described with reference to FIG.
FIG. 15 (a) is a plan view showing a part of the GaN seed on the nitrogen polar surface side in which a pattern mask in which linear openings form discontinuous intersections is arranged. A discontinuous intersection is formed by the first linear opening 311 and the second linear opening 312 divided into two.
When a GaN crystal is grown on the GaN seed, the distance between the first linear opening 311 and the second linear opening 312 is small, so that the shape of the GaN crystal in the growth stage of FIG. 13C is continuous. It is the same as when it grows on the target intersection. That is, as shown in FIG. 15B, the recessed portion indicated by the arrow is formed on the side portion of the GaN crystal 40 that grows on the discontinuous intersection. The resulting recessed angle effect encourages the GaN crystal 40 to grow in the direction opposite to the arrow.
Those skilled in the art will appreciate that the recessed angle effect described above can occur when a GaN crystal grows on the various intersections illustrated in FIGS. 10 and 11.

Hereinafter, the crystal growth apparatus and crystal growth conditions that can be preferably used in step S3 will be described.
For the growth of the GaN crystal by the amonothermal method in step S3, the type of crystal growth apparatus shown in FIG. 16 can be preferably used.
Referring to FIG. 16, the crystal growth apparatus 100 includes an autoclave 101 and a Pt capsule 102 installed therein.
The capsule 102 has a raw material dissolution zone 102a and a crystal growth zone 102b internally partitioned by a baffle 103 made of Pt. The feedstock F is placed in the raw material dissolution zone 102a. A seed S suspended by a Pt wire 104 is installed in the crystal growth zone 102b.
A gas line to which the vacuum pump 105, the ammonia cylinder 106 and the nitrogen cylinder 107 are connected is connected to the autoclave 101 and the capsule 102 via a valve 108. When NH ₃ (ammonia) is put into the capsule 102, it is possible to check the amount of NH ₃ supplied from the ammonia cylinder 106 with the mass flow meter 109.

The feedstock, a gaseous GaCl obtained by contacting the HCl (hydrogen chloride) gas alone Ga (gallium metal) under heating, the polycrystalline GaN manufactured by the method of reacting the NH ₃ gas, preferably be used Can be done.
Mining agents for promoting the dissolution of feedstock include one or more ammonium halides selected from NH ₄ Cl (ammonium chloride), NH ₄ Br (ammonium bromide) and NH ₄ I (ammonium iodide). , NH ₄ F is preferably used in combination.
Particularly preferably, NH ₄ F and NH ₄ I are used in combination.
When using the growth temperature of 650 ° C. or less, it is not recommended to use only ammonium halide other than NH ₄ F in mineralizer. This is because the growth direction of the GaN crystal is substantially only in the [000-1] direction, and lateral growth does not occur.
On the other hand, when NH ₄ F is used alone as a mineralizing agent, lateral growth is strongly promoted.
It becomes difficult to grow the GaN crystal in the manner shown in FIG. 13, that is, to grow the GaN crystal so that a gap is formed between the GaN crystal and the pattern mask.

When growing a GaN crystal on the seed S, NH ₃ is also placed in the space between the autoclave 101 and the capsule 102, and the capsule 102 is heated from the outside of the autoclave 101 with a heater (not shown). The inside is a supercritical state or a subcritical state.
Etching also occurs on the surface of the seed S until the feedstock F is sufficiently dissolved and the solvent reaches saturation. If necessary, a temperature reversal period in which the temperature gradient between the raw material dissolution zone 102a and the crystal growth zone 102b is reversed from that during crystal growth for the purpose of promoting the etchback of the seed S before the start of growth. Can also be provided.
The growth temperature is preferably 550 ° C. or higher. It is not hindered to use a growth temperature of 1000 ° C. or higher, but it is possible to grow a GaN crystal of sufficiently high quality even at 700 ° C. or lower.
The growth pressure can be set, for example, in the range of 100 to 250 MPa, but is not limited.

As an example, NH ₄ F and NH ₄ I were used as mineralizing agents so that the molar ratios to NH ₃ were 0.5% and 4.0%, respectively, the pressure was about 220 MPa, and the temperature Ts of the raw material dissolution zone. GaN can be grown under the condition that the average value of the temperature Tg of the crystal growth zone is about 600 ° C. and the temperature difference Ts−Tg between these two zones is about 5 ° C. (Ts> Tg).
It is possible to increase the growth rate of the GaN crystal by increasing the temperature difference between the raw material dissolution zone and the crystal growth zone, but if the growth rate is too high, the growth of the GaN crystal is shown in FIG. 13 (c). It may be difficult to proceed from the stage of FIG. 13 (d), that is, it may be difficult to close the through hole of the GaN crystal.
In step S3, each time the feedstock is exhausted, the capsule can be replaced and the GaN crystal can be repeatedly regrown.
In order to impart n-type conductivity to the GaN crystal to be grown, it may be doped with O (oxygen), Si (silicon), Ge (germanium), S (sulfur) or the like.
In order to make the GaN crystal to be grown semi-insulating, it may be doped with iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), magnesium (magnesium) or the like.

(4) Step S4
By processing the GaN crystal grown in step S3, a GaN substrate having various plane orientations can be manufactured. The process may include slicing the GaN crystal with a slicer such as a single wire saw or a multi wire saw. The slice thickness can be appropriately determined depending on the intended purpose, but is usually 100 μm or more and 20 mm or less.
Flattening of the cut surface of a GaN crystal can be performed by either or both grinding and wrapping. The damage layer can be removed from the cut surface by CMP and / or etching.
When the GaN crystal 40 grown in step S3 is sliced parallel to or substantially parallel to the C plane to form a C plane GaN substrate, slicing at the position shown by the broken line in FIG. 17A does not have a through hole. A C-plane GaN substrate can be obtained. Such a substrate can be suitably used for manufacturing a semiconductor device or a GaN layer-bonded substrate, and can also be suitably used as a seed when growing a bulk GaN crystal by various crystal growth techniques. Such a substrate is also one of the preferred examples of the GaN seed to be prepared in step S1 described above.

On the other hand, when the GaN crystal 40 is sliced at the position shown by the broken line in FIG. 17B, the obtained C-plane GaN substrate has through holes on the main surface, so that it is not suitable for use as a substrate for a semiconductor device. It can be used as a seed when a bulk GaN crystal is grown amonothermally using an acidic mineralizing agent containing F. This is because when the acidic mineralizing agent contains F, the GaN crystal grows so as to close the through hole even if the seed has a through hole.
In one example, in step S3, the GaN crystal 40 is in a state in which the growth of the GaN crystal 40 does not completely proceed to the stage shown in FIG. 13 (d), that is, in a state where all or part of the through hole T remains unclosed. However, in such a case, in step S4, no matter where the grown GaN crystal 40 is sliced, only a C-plane GaN substrate having through holes can be obtained. The C-plane GaN substrate having through holes can be used as a seed when a bulk GaN crystal is grown amonothermally by using an acidic mineralizing agent containing F.

The case where a GaN crystal is grown on the nitrogen-polar surface of the C-plane GaN substrate manufactured by the method of the embodiment by the acidic amonothermal method without using a pattern mask will be described as follows.
As the growth device, the type shown in FIG. 16 can be preferably used.
The feedstock, a gaseous GaCl obtained by contacting the HCl gas alone Ga under heat, polycrystalline GaN manufactured by the method of reacting the NH ₃ gas can be preferably used.
NH ₄ F can be preferably used as the mineralizing agent. NH ₄ Cl, may be one or more ammonium halide is selected from _NH 4 Br and NH ₄ I in combination with NH ₄ F, for example, it may be a combination of NH ₄ F and NH ₄ I.
The concentration of NH ₄ F can be 0.1 to 1% in terms of molar ratio to NH ₃ . The concentration of ammonium halide other than NH ₄ F can be 1 to 5% in terms of molar ratio to NH ₃ .
The pressure and temperature can be set, for example, in the range of 100 to 250 MPa and in the range of 550 to 650 ° C, respectively, but are not limited.

3. 3. Experimental results 3.1. Experiment 1
<Manufacturing of C-plane GaN substrate>
As a GaN seed, a C-plane GaN substrate cut out from a GaN crystal grown by the HVPE method was prepared. This C-plane GaN substrate had a CMP-finished nitrogen-polar surface and a gallium-polar surface, respectively. The orientation of the nitrogen polar surface was within 1 ° from the [000-1] direction.
On the nitrogen-polar surface of the GaN seed, a pattern mask having a striped opening pattern was formed, which was composed of a laminated film having a 100 nm-thick Pt layer on a 100 nm-thick TiW layer. The lift-off method was used for patterning the mask. The line width of the linear openings constituting the opening pattern was 50 μm, and the pitch between the linear openings was 4 mm. The stripe direction was tilted 12 ° from the line of intersection between the nitrogen polar surface of the GaN seed and the M surface.

After forming the pattern mask, a GaN crystal was grown on the GaN seed by the amonothermal method using the crystal growth apparatus of the type shown in FIG.
The feedstock was used a gaseous GaCl obtained by contacting the HCl gas alone Ga under heat, polycrystalline GaN synthesized by a method of reacting the NH ₃ gas.
NH ₄ F and NH ₄ I were used in combination as the mineralizing agent. The amount of NH ₄ F and NH ₄ I is NH
_The molar ratio to _{3 was} 0.5% and 4.0%, respectively. NH ₄ I was synthesized by introducing HI (hydrogen iodide) into a Pt capsule after adding NH ₃ .

The growth conditions were such that the average value of the temperature Tg of the crystal growth zone and the temperature Ts of the raw material dissolution zone was 598 ° C., the temperature difference between the crystal growth zone and the raw material dissolution zone was 5 ° C. (Ts> Tg), and the pressure was 220 MPa.
When 35 days had passed from the start of growth, the capsule was opened and the GaN seed was taken out, and when the GaN crystal grown on the [000-1] side was observed, the growth front reached above the pattern mask, but in the lateral direction. The growth rate of the pattern mask was not uniform in the plane, and the through hole formed above the non-opening of the pattern mask started to be blocked in some parts, but was not closed in most parts.
After the observation, the GaN seed was transferred to a newly prepared capsule and re-grown under the same amonothermal growth conditions. Growth was terminated 35 days after the start of regrowth.

During the regrowth, the through holes of the GaN crystal were completely closed and the growth front was flattened.
When the grown GaN crystal was separated from the GaN seed and the surface on the [0001] side (the side bonded to the GaN seed) was observed, a plurality of V-grooves parallel to each other were formed at equal intervals.
The longitudinal direction of the V-grooves was the same as the longitudinal direction of the linear openings provided in the pattern mask, and the pitch between the V-grooves was the same as the pitch between the linear openings. This indicates that the GaN crystal grew in the manner shown in FIG. 13 and that the remnants of the voids formed as a result are the V-grooves.
The depth of the V-groove measured with a laser microscope was 1.9 mm at the deepest part. Combined with the observation results before regrowth, it was considered that the above-mentioned through holes formed in the growing GaN crystal began to be closed when the GaN crystal grew 1 to 2 mm in the [000-1] direction.
The above-mentioned GaN single crystal grown by the amonothermal method was sliced in parallel with the C plane to obtain a plurality of blank substrates. One of them was processed to prepare a C-plane GaN substrate having a thickness of 350 μm in which both main surfaces were CMP-finished.

<X-ray locking curve measurement>
The XRC of (004) reflection on the gallium polar surface of the produced C-plane GaN substrate was measured using an X-ray diffractometer [PANalytical X'Pert Pro MRD manufactured by Spectris Co., Ltd.] using CuKα as an X-ray source. .. The incident side optical system includes a 1/2 slit, an X-ray mirror, and Ge (
440) A 4-crystal monochromator and a cross slit of w0.2 mm × h1 mm were used, and the 0D mode of the PIXcel ^3D (registered trademark) detector was used for the light receiving optical system. The resolution of the optical system was 5 to 6 arcsec. The X-ray beam size on the sample surface was set to be 0.2 mm × 5 mm when the X-ray incident angle was 90 ° (the X-ray incident direction was orthogonal to the sample surface). At the time of measurement, the direction in which the beam size was 5 mm was made orthogonal to the X-ray incident surface.

First, ω scans were performed at 1 mm intervals on a line segment having a length of 70 mm parallel to the m axis and passing through the substantially center of the gallium polar surface. In each ω scan, the X-ray incident surface was parallel to the m-axis. That is, X-rays were incident on the gallium polar surface of the sample from the direction orthogonal to the a-axis.
The XRC peak angles and FWHM of the (004) reflection at all measurement points were as shown in Table 1 below.

The maximum, mean and standard deviations of FWHM between all measurement points were 26.3 arcsec, 11.7 arcsec and 3.8 arcsec, respectively.
The difference between the maximum and minimum peak angles among all the measurement points was 0.17 °.
Measurement point No. From 16 to measurement point No. Looking at the section of 40 mm in length including 40 measurement points up to 55, the maximum value, mean value and standard deviation of FWHM are 17.0 arcsec, 10.4 arcsec and 2.8 arcsec, respectively, and the peak angle The difference between the maximum value and the minimum value was 0.10 °.

Next, ω scans were performed at 1 mm intervals on a line segment having a length of 59 mm parallel to the a-axis, which passed through the substantially center of the gallium polar surface. In each ω scan, the X-ray incident surface was parallel to the a-axis. That is, X-rays were incident on the gallium polar surface of the sample from the direction orthogonal to the m-axis.
The XRC peak angles and FWHM of the (004) reflection at all measurement points were as shown in Table 2 below.

The maximum, mean and standard deviations of FWHM between all measurement points were 24.3 arcsec, 13.0 arcsec and 4.2 arcsec, respectively. The difference between the maximum and minimum peak angles among all the measurement points was 0.16 °.
Measurement point No. Measurement point No. 11 Looking at the 40 mm long section containing up to 50 measurement points, the maximum, mean and standard deviations of FWHM are 23.2 arcsec, 12.7 arcsec and 3.7 arcsec, respectively, of peak angles. The difference between the maximum value and the minimum value was 0.11 °.

<Infrared absorption spectrum measurement>
When the infrared absorption spectrum of the prepared C-plane GaN substrate was measured, a plurality of absorption peaks belonging to the gallium vacancy-hydrogen complex were observed at 3100 to 3500 cm ^-1 . Some of the plurality of absorption peaks, the peak wavelength was contained four peaks in each 3150cm around ^-1, 3164 cm around ^-1, around 3176Cm ^-1 and around 3188cm ^-1.

3.2. Experiment 2 <Preparation of C-plane GaN substrate>
A 330 μm-thick C-plane GaN substrate cut out from a GaN crystal grown monothermally in Experiment 1 was used as a GaN seed, and a crystal growth apparatus of the type shown in FIG. 16 was used by the amonothermal method. A GaN crystal was grown. For the GaN seed, both main surfaces were CMP-finished to remove the damaged layer formed during flattening by grinding.
The feedstock was used a gaseous GaCl obtained by contacting the HCl gas alone Ga under heat, polycrystalline GaN synthesized by a method of reacting the NH ₃ gas.
NH ₄ F and NH ₄ I were used as the mineralizing agents. The amounts of NH ₄ F and NH ₄ I were 1% each in terms of molar ratio to NH ₃ . NH ₄ I was synthesized by introducing HI into a Pt capsule after adding NH ₃ .

The growth conditions are as follows: the average value of the temperature Tg of the crystal growth zone and the temperature Ts of the raw material melting zone is 605 to 610 ° C., the temperature difference between the crystal growth zone and the raw material melting zone is 5 to 10 ° C. (Ts> Tg), and the pressure is 220 MPa. And said.
After 28 days of growth, GaN crystals grew 1.8 mm in the [000-1] direction on the nitrogen-polar surface of the GaN seed.
Next, the grown GaN crystal was processed to prepare a C-plane GaN substrate having a diameter of 50 mm. The main surface of the GaN substrate was ground and flattened on both sides, and then further CMP-finished to remove the damaged layer. The final substrate thickness was 350 μm.

<X-ray locking curve measurement>
The XRC of (004) reflection on the gallium polar surface of the prepared C-plane GaN substrate was measured in the same manner as in Experiment 1.
First, ω scans were performed at 1 mm intervals on a line segment having a length of 48 mm parallel to the m axis and passing through the substantially center of the gallium polar surface. In each ω scan, the X-ray incident surface was parallel to the m-axis. That is, X-rays were incident on the gallium polar surface of the sample from the direction orthogonal to the a-axis.
The XRC peak angles and FWHM of the (004) reflection at all measurement points were as shown in Table 3 below.

The maximum, mean and standard deviations of FWHM between all measurement points were 17.5 arcsec, 10.2 arcsec and 2.3 arcsec, respectively.
The difference between the maximum and minimum peak angles among all the measurement points was 0.08 °.
Measurement point No. Measurement point No. 5 Looking at the section of 40 mm in length including 40 measurement points up to 44, the maximum value, mean value and standard deviation of FWHM are 12.6 arcsec, 9.6 arcsec and 1.4 arc sec, respectively, and the peak angle The difference between the maximum value and the minimum value was 0.07 °.

Next, ω scans were performed at 1 mm intervals on a line segment having a length of 49 mm parallel to the a-axis, which passed through the substantially center of the gallium polar surface. In each ω scan, the X-ray incident surface was parallel to the a-axis. That is, X-rays were incident on the gallium polar surface of the sample from the direction orthogonal to the m-axis.
The XRC peak angles and FWHM of the (004) reflection at all measurement points were as shown in Table 4 below.

The maximum, mean and standard deviations of FWHM between all measurement points were 18.2 arcsec, 9.5 arcsec and 2.5 arcsec, respectively.
The difference between the maximum and minimum peak angles among all the measurement points was 0.07 °.
Measurement point No. Measurement point No. 5 Looking at the section of 40 mm in length including 40 measurement points up to 44, the maximum value, mean value and standard deviation of FWHM are 18.2 arcsec, 9.5 arcsec and 2.7 arcsec, respectively, of the peak angle. The difference between the maximum value and the minimum value was 0.06 °.
<Infrared absorption spectrum measurement>
When the infrared absorption spectrum of the prepared C-plane GaN substrate was measured, a plurality of absorption peaks attributed to the gallium vacancy-hydrogen complex were observed at 3140 to 3200 cm ^-1 .

3.3. Experiment 3
<Manufacturing of C-plane GaN substrate>
As a primary GaN seed, a C-plane GaN substrate cut out from a GaN crystal grown by the HVPE method was prepared. This C-plane GaN substrate had a CMP-finished nitrogen-polar surface and a gallium-polar surface, respectively. The orientation of the nitrogen polar surface was within 1 ° from [000-1].
On the nitrogen-polar surface of the primary GaN seed, a pattern mask having a square lattice-type periodic opening pattern was formed, which was composed of a laminated film having a 100 nm-thick Pt layer on a 100 nm-thick TiW layer. The lift-off method was used for patterning the mask.
The square grid-type periodic opening pattern was composed of a first linear opening and a second linear opening forming an angle of 60 ° with each other. The line width of each linear opening was 50 μm. The pitch between the first linear openings was 4 mm, and the pitch between the second linear openings was 2 mm.
The longitudinal directions of the first and second linear openings were each tilted 12 ° from one of the lines of intersection of the nitrogen-polar surface and the M-plane of the primary GaN seed.

After forming the pattern mask, a GaN crystal was grown on the primary GaN seed by an acidic amonothermal method using a crystal growth apparatus of the type shown in FIG.
The feedstock was used a gaseous GaCl obtained by contacting the HCl gas alone Ga under heat, polycrystalline GaN synthesized by a method of reacting the NH ₃ gas.
NH ₄ F and NH ₄ I were used in combination as the mineralizing agent. The amount of NH ₄ F and NH ₄ I is NH
_The molar ratio to _{3 was} 0.5% and 4.0%, respectively. NH ₄ I was synthesized by introducing HI (hydrogen iodide) into a Pt capsule after adding NH ₃ . The growth conditions are as follows: the average value of the temperature Tg of the crystal growth zone and the temperature Ts of the raw material melting zone is 605 to 610 ° C., the temperature difference between the crystal growth zone and the raw material melting zone is 3 to 8 ° C. (Ts> Tg), and the pressure is 220 MPa. And said.
After 22 days of growth, GaN crystals grew 3.2 mm in the [000-1] direction on the nitrogen-polar surface of the primary GaN seed.

The above-mentioned GaN crystal grown in an amonothermal manner was processed to prepare a C-plane GaN substrate having a thickness of 430 μm. Specifically, a GaN crystal was sliced parallel to the C plane using a multi-wire saw, and both main surfaces of the obtained blank substrate were ground and flattened, and then CMP finished to remove the damaged layer. ..
Next, the same pattern mask as the pattern mask provided on the primary GaN seed was formed on the nitrogen-polar surface of the C-plane GaN substrate by using the lift method. The orientation of the inclined square grid pattern provided on the pattern mask was also the same as that of the primary GaN seed.

After forming the pattern mask, the C-plane GaN substrate was used as a secondary GaN seed, and a GaN crystal was grown by an acidic amonothermal method.
As the crystal growth apparatus, the type shown in FIG. 16 was used.
The feedstock was used a gaseous GaCl obtained by contacting the HCl gas alone Ga under heat, polycrystalline GaN synthesized by a method of reacting the NH ₃ gas.
NH ₄ F and NH ₄ I were used in combination as the mineralizing agent. The amount of NH ₄ F and NH ₄ I is NH
_The molar ratio to ₃ was 1.0%, respectively. NH ₄ I was synthesized by introducing HI (hydrogen iodide) into a Pt capsule after adding NH ₃ .
The growth conditions are as follows: the average value of the temperature Tg of the crystal growth zone and the temperature Ts of the raw material melting zone is 605 to 610 ° C., the temperature difference between the crystal growth zone and the raw material melting zone is 5 to 10 ° C. (Ts> Tg), and the pressure is 220 MPa. And said.
After 28 days of growth, GaN crystals grew 2.0 mm in the [000-1] direction on the nitrogen-polar surface of the secondary GaN seed.
Next, the grown GaN crystal was processed to prepare a conductive C-plane GaN substrate having a diameter of 50 mm. The main surface of the GaN substrate was ground and flattened on both sides, and then further CMP-finished to remove the damaged layer. The final substrate thickness was 309 μm.

<X-ray locking curve measurement>
The XRC of (004) reflection on the gallium polar surface of the prepared C-plane GaN substrate was measured in the same manner as in Experiment 1.
First, ω scans were performed at 1 mm intervals on a line segment having a length of 47 mm parallel to the m axis and passing through the substantially center of the gallium polar surface. In each ω scan, the X-ray incident surface was parallel to the m-axis. That is, X-rays were incident on the gallium polar surface of the sample from the direction orthogonal to the a-axis.
The XRC peak angles and FWHM of the (004) reflection at all measurement points were as shown in Table 5 below.

The maximum, mean and standard deviations of FWHM between all measurement points were 19.7 arcsec, 11.2 arcsec and 2.7 arcsec, respectively.
The difference between the maximum and minimum peak angles among all the measurement points was 0.10 °.
Measurement point No. Measurement point No. 4 Looking at the section of 40 mm in length including 40 measurement points up to 43, the maximum value, mean value and standard deviation of FWHM are 19.7 arcsec, 11.2 arcsec and 3.1 arcsec, respectively, of the peak angle. The difference between the maximum value and the minimum value was 0.10 °.

Next, ω scans were performed at 1 mm intervals on a line segment having a length of 46 mm parallel to the a-axis, which passed through the substantially center of the gallium polar surface. In each ω scan, the X-ray incident surface was parallel to the a-axis. That is, X-rays were incident on the gallium polar surface of the sample from the direction orthogonal to the m-axis.
The XRC peak angle and FWHM of the (004) reflection at all measurement points were as shown in Table 6 below.

The maximum, mean and standard deviations of FWHM between all measurement points were 18.8 arcsec, 10.6 arcsec and 2.1 arcsec, respectively.
The difference between the maximum and minimum peak angles among all the measurement points was 0.11 °.
Measurement point No. Measurement point No. 4 Looking at the section of 40 mm in length including 40 measurement points up to 43, the maximum value, mean value and standard deviation of FWHM are 18.8 arcsec, 10.6 arcsec and 2.1 arcsec, respectively, of the peak angle. The difference between the maximum value and the minimum value was 0.10 °.

Although the present invention has been described above with reference to specific embodiments, each embodiment is presented as an example and does not limit the scope of the present invention. Each of the embodiments described herein can be variously modified without departing from the spirit of the invention and, to the extent practicable, combined with features described by other embodiments. be able to.

10 C surface GaN substrate 11 Gallium polar surface 12 Nitrogen polar surface 13 Side surface 20 Seed substrate 21 Gallium polar surface 22 Nitrogen polar surface 23 Side surface 30 Pattern mask 31 Linear opening 40 GaN crystal G Gap T Through hole V Void K Crossing 100 Crystal Growth device 101 Autoclave 102 Capsule 102a Raw material dissolution zone 102b Crystal growth zone 103 Baffle 104 Pt wire 105 Vacuum pump 106 Ammonia bomb 107 Nitrogen bomb 108 Valve 109 Mass flow meter

Claims (24)

A C-plane GaN substrate capable of drawing at least one first line segment, which is a virtual line segment having a length of 40 mm, satisfying at least one of the following conditions (A1) and (B1) on the main surface:
(A1) On the first line segment, when the X-ray incident surface at each ω scan is parallel to the first line segment and (004) the XRC of reflection is measured at 1 mm intervals, between all measurement points. The maximum value of FWHM of XRC is less than 30 arcsec;
(B1) On the first line segment, when the X-ray incident surface at each ω scan is parallel to the first line segment and (004) the XRC of reflection is measured at 1 mm intervals, between all measurement points. The difference between the maximum value and the minimum value of the peak angle of XRC is less than 0.2 °. The C-plane GaN substrate according to claim 1, wherein the first line segment satisfies the above condition (A1). The C-plane GaN substrate according to claim 2, wherein the first line segment satisfies the following condition (A2) in addition to the condition (A1).
(A2) The average FWHM of XRC among all the measurement points on the first line segment obtained from the XRC measurement is less than 20 arcsec. The C-plane GaN substrate according to claim 2, wherein the first line segment satisfies the following condition (A3) in addition to the condition (A1).
(A3) The mean and standard deviation of the FWHM of XRC among all the measurement points on the first line segment obtained from the XRC measurement are less than 12 arcsec and less than 5 arc sec, respectively. Claim that at least one second line segment, which is a virtual line segment having a length of 40 mm satisfying at least one of the following conditions (C1) and (D1), can be drawn on the main surface on which the first line segment can be drawn. The C-plane GaN substrate according to any one of 1 to 4:
(C1) The second line segment is orthogonal to at least one of the first line segments, and the X-ray incident surface at each ω scan is made parallel to the second line segment on the second line segment. (004) When the XRC of reflection is measured at 1 mm intervals, the maximum value of FWHM of XRC between all measurement points is less than 30 arcsec;
(D1) The second line segment is orthogonal to at least one of the first line segments, and the X-ray incident surface at each ω scan is made parallel to the second line segment on the second line segment. (004) When the reflection XRC is measured at 1 mm intervals, the difference between the maximum value and the minimum value of the XRC peak angle among all the measurement points is less than 0.2 °. The C-plane GaN substrate according to claim 5, wherein the second line segment satisfies the condition (C1). The C-plane GaN substrate according to claim 6, wherein the second line segment satisfies the following condition (C2) in addition to the condition (C1).
(C2) The average FWHM of XRC among all the measurement points on the second line segment obtained from the XRC measurement is less than 20 arcsec. The C-plane GaN substrate according to claim 6, wherein the second line segment satisfies the following condition (C3) in addition to the condition (C1).
(C3) The mean and standard deviation of the XRC FWHM between all measurement points on the second line segment obtained from the XRC measurement is less than 12 arcsec and less than 5 arc sec, respectively. The C-plane GaN substrate according to any one of claims 1 to 8, which has a plurality of dislocation arrays periodically arranged on the main surface. The C-plane GaN substrate according to claim 9, wherein the arrangement of the plurality of dislocation arrays on the main surface is two-dimensional. The C-plane GaN substrate according to claim 10, wherein the arrangement of the plurality of dislocation arrays on the main surface has periodicity in two or more directions. The C-plane GaN substrate according to any one of claims 1 to 11, wherein the concentrations of Li, Na, K, Mg and Ca are less than 1 × 10 ¹⁶ atoms / cm ³ . The C-plane GaN substrate according to claim 12, which contains F. The C-plane GaN substrate according to claim 13, which contains one or more halogens selected from Cl, Br and I in addition to F. The C-plane GaN substrate according to claim 14, which contains F and I. The C-plane GaN substrate according to any one of claims 1 to 15, wherein the H concentration is 5 × 10 ¹⁷ atoms / cm ³ or more and 1 × 10 ²⁰ atoms / cm ³ or less. The C-plane GaN substrate according to any one of claims 1 to 16, comprising a GaN crystal having an infrared absorption peak attributed to a gallium vacancy-hydrogen complex at 3140 to 3200 cm ^-1 . The C-plane GaN substrate according to any one of claims 1 to 17, wherein the sizes in the [1-100] direction, the [10-10] direction, and the [01-10] direction are all 45 mm or more. The C-plane GaN substrate according to any one of claims 1 to 18, which is disk-shaped and has a diameter of 45 mm or more. The C-plane GaN substrate according to any one of claims 1 to 19, which has a gallium polar surface having an orientation within 5 ° from [0001]. A nitride semiconductor device comprising the step of preparing the C-plane GaN substrate according to any one of claims 1 to 20 and the step of epitaxially growing one or more nitride semiconductors on the prepared C-plane GaN substrate. Manufacturing method. Manufacture of an epitaxial substrate including the step of preparing the C-plane GaN substrate according to any one of claims 1 to 20 and the step of epitaxially growing one or more nitride semiconductors on the prepared C-plane GaN substrate. Method. A bulk nitride semiconductor crystal comprising the step of preparing the C-plane GaN substrate according to any one of claims 1 to 20 and the step of epitaxially growing a nitride semiconductor crystal on the prepared C-plane GaN substrate. Production method. A method for manufacturing a GaN layer bonded substrate, comprising the step of preparing the C-plane GaN substrate according to any one of claims 1 to 20 and the step of bonding the prepared C-plane GaN substrate to a different composition substrate.