JP7284983B2 - Semiconductor substrate manufacturing method and base substrate used therefor - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor substrate and a base substrate used therefor.

High-quality GaN substrates with low dislocation density are required to obtain highly efficient light-emitting devices and power devices. For example, Patent Documents 1 and 2 disclose, for the purpose of manufacturing a GaN substrate with a low dislocation density, a plurality of GaN triangular facet structures are formed on a base substrate, and then recesses between mutually adjacent triangular facet structures are formed. forming a first thick film growth layer so as to bury a plurality of triangular facet structures; burying the first thick film growth layer. Non-Patent Documents 1 and 2 also disclose techniques for reducing dislocations in GaN.

JP 2018-30763 A JP 2018-30764 A

Journal of Crystal Growth 350 (2012) 44-49 Huiyuan Geng, Haruo Sunakawa, Norihiko Sumi, Kazutomi Yamamoto, A. Atsushi Yamaguchi, Akira Usui Growth and strain characterization of high quality GaN crystal by HVPE Journal of Crystal Growth 305 (2007) 377-383 Kensaku Motoki, Takuji Okahisa, Ryu Hirota, Seiji Nakahata,Koji Uematsu, Naoki Matsumoto Dislocation reduction in GaN crystal by advanced-DEEP

An object of the present invention is to provide a method of manufacturing a semiconductor substrate in which dislocations are dispersed.

The present invention comprises: a substrate body; a plurality of striped long-period masks provided on the substrate body at regular intervals; and a plurality of striped short-period masks having different widths from the long-period masks provided at intervals of 15 μm or more and 80 μm or less, wherein the substrate body is exposed between the short-period masks adjacent to each other. preparing a base substrate; and causing crystal growth of a semiconductor starting from the substrate body exposed between the plurality of short-period masks on the base substrate, so that the width directions of the long-period mask and the short-period mask are respectively changed. A plurality of small triangular facet structures formed by crystal growth of the semiconductor are arranged side by side in the width direction of the long-period mask and the short-period mask so as to form a triangle having a relatively small cross-sectional shape along the and respectively capturing two or more of the plurality of small triangular facet structures between the plurality of long period masks in the underlying substrate, and widths of the long period mask and the short period mask. A plurality of large triangular facet structures formed by crystal growth of the semiconductor are arranged side by side in the width direction of the long-period mask and the short-period mask so as to form a triangular shape having a relatively large cross-sectional shape along the direction. and forming a semiconductor substrate.

The present invention relates to a base substrate used for manufacturing a semiconductor substrate, comprising: a substrate body ; a plurality of striped long-period masks provided on the substrate body at regular intervals at regular intervals; a plurality of striped short-period masks having widths different from those of the long-period masks, provided between the long-period masks adjacent to each other on the main body with a constant interval of 15 μm or more and 80 μm or less ; The substrate body is exposed between the short-period masks adjacent to each other .

According to the present invention, a dislocation-dispersed semiconductor is formed by forming a plurality of small triangular facet structures and forming a plurality of large triangular facet structures each incorporating two or more of the plurality of small triangular facet structures. A substrate can be manufactured.

1 is a perspective view of a base substrate used in a method for manufacturing a semiconductor substrate according to an embodiment; FIG. FIG. 4 is a plan view of a base substrate used in the method for manufacturing a semiconductor substrate according to the embodiment; It is IC-IC sectional drawing in FIG. 1B. FIG. 4 is a perspective view showing a state of crystal growth on a base substrate in a step of forming a small triangular facet structure; FIG. 4 is a cross-sectional view showing a state of crystal growth on the underlying substrate in the step of forming a small triangular facet structure; FIG. 4 is a perspective view showing a state of crystal growth on the underlying substrate in the step of forming a large triangular facet structure; FIG. 4 is a cross-sectional view showing a state of crystal growth on the underlying substrate in the step of forming a large triangular facet structure; FIG. 4 is a cross-sectional view showing a state of crystal growth on the base substrate in the first half of the thick film growth step; FIG. 11 is a cross-sectional view showing a state of crystal growth on the base substrate in the first half of the modification of the thick film growth step; FIG. 10 is a cross-sectional view showing a state of crystal growth on the base substrate in the second half of the thick film growth step; FIG. 11 is a cross-sectional view showing a state of crystal growth on the base substrate in the second half of the modification of the thick film growth step; FIG. 11 is a plan view of a modification of the underlying substrate; 1 is a plan view of an underlying substrate used in Example 1. FIG. 2 is a plan view of a base substrate used in Example 2. FIG. FIG. 11 is a plan view of a base substrate used in Example 3; 4 is a timing chart when crystal growth of GaN is performed on the base substrate; It is a fluorescent microscope image of a cross section of GaN crystal-grown on the underlying substrate. FIG. 4 is an explanatory diagram of a method of obtaining dislocation density distribution; FIG. 4 is a diagram showing the distribution of dislocation densities in regions A to E on the surface of a GaN layer;

Hereinafter, embodiments will be described in detail based on the drawings.

A method for manufacturing a semiconductor substrate according to an embodiment includes a base substrate preparation step and a semiconductor crystal growth step. Although an example of manufacturing a GaN substrate using GaN as a semiconductor will be described below, the present invention is not particularly limited to this, and the semiconductor may be AlGaN, InGaN, InAlGaN, InAlN, InN, or the like.

(Underlying substrate preparation process)
In the base substrate preparation step, a base substrate 10 as shown in FIGS. 1A to 1C, which is used for manufacturing a GaN substrate, is prepared. The underlying substrate 10 comprises a substrate body 11 and a long-period mask 12 and a short-period mask 13 respectively provided thereon.

The substrate body 11 preferably has a body surface exposed between the masks composed of GaN, the same semiconductor from which crystals are subsequently grown. Therefore, the substrate body 11 is preferably a GaN substrate, or a substrate having a GaN film on its surface, such as a sapphire substrate, ZnO substrate, or SiC substrate. The principal plane of GaN forming the substrate surface is not particularly limited, but is preferably the c-plane. Note that the substrate body 11 may be, for example, a sapphire substrate, a ZnO substrate, a SiC substrate, or the like.

The long-period mask 12 is made of, for example, silicon dioxide (SiO ₂ ), silicon nitride (SiNx), or the like. A plurality of long-period masks 12 are provided on the substrate body 11 so as to extend in a stripe shape parallel to one direction with a constant period _P1 and an interval _W1 . The long-period mask 12 is preferably provided so that the width direction is aligned with the a-axis direction or the m-axis direction of the substrate body 11 .

The width _w1 of the long-period mask 12 is preferably 10 μm or more and 100 μm or less, more preferably 10 μm or more and 50 μm or less, and still more preferably 10 μm or more and 20 μm or less. The width _w1 of the long period mask 12 is preferably constant in the length direction.

The interval _W1 between the long-period masks 12 adjacent to each other is preferably 100 μm to 3000 μm, more preferably 100 μm to 1000 μm, even more preferably 100 μm to 900 μm, and even more preferably 100 μm to 500 μm. The spacing _W1 between the long period masks 12 adjacent to each other is preferably constant in the length direction. The spacing _W1 between the long-period masks 12 adjacent to each other is preferably greater than the width _w1 of the long-period masks 12 . The ratio (W ₁ /w ₁ ) of the spacing W ₁ between the mutually adjacent long-period masks 12 to the width w 1 of the long-period masks 12 _is preferably 5 or more and 50 or less, more preferably 5 or more and 25 or less, and even more preferably. is 10 or more and 25 or less.

The sum of the width _w1 of the long-period mask 12 and the interval _W1 between the long-period masks 12 adjacent to each other, that is, the period _P1 of the long-period mask 12 is preferably 100 μm or more and 1000 μm or less, more preferably 100 μm or more and 500 μm. It is below. The thickness of the long-period mask 12 is preferably 10 nm or more and 500 nm or less, more preferably 10 nm or more and 200 nm or less.

The short-period mask 13 is made of, for example, silicon dioxide (SiO ₂ ), silicon nitride (SiNx), or the like. From the viewpoint of simultaneously forming the long-period mask 12 and the short-period mask 13 on the substrate body 11 , the short-period mask 13 is preferably made of the same material as the long-period mask 12 . The short-period masks 13 are arranged in parallel with the long-period masks 12 between the long-period masks 12 adjacent to each other on the substrate body 11, and a plurality of the short-period masks 13 are arranged in stripes parallel to one direction with a constant period _P2 and an interval _W2 . It is provided to extend to

The short-period mask 13 differs from the long-period mask 12 in its width _w2 . The width w ₂ of the short-period mask 13 is preferably smaller than the width w ₁ of the long-period mask 12 . The width _w2 of the short-period mask 13 is preferably 1 μm or more and 15 μm or less, more preferably 2 μm or more and 10 μm or less, and still more preferably 3 μm or more and 5 μm or less. The ratio (w ₂ /w ₁ ) of the width w ₂ of the short-period mask 13 to the width w ₁ of the long-period mask 12 is preferably 1/10 or more and 1/2 or less. The width _w2 of the short-period mask 13 is preferably constant in the length direction.

The interval _W2 between the short-period masks 13 adjacent to each other is preferably 10 μm or more and 80 μm or less, more preferably 15 μm or more and 60 μm or less, and still more preferably 20 μm or more and 40 μm or less. The spacing _W2 between the mutually adjacent short period masks 13 is shorter than the spacing _W1 between the mutually adjacent long period masks 12, but the ratio of the former to the latter ( _W2 / _W1 ) is preferably 1 /10 or more and 1/2 or less, more preferably 1/5 or more and 1/2 or less. The interval _W2 between the short-period masks 13 adjacent to each other is preferably constant in the longitudinal direction. The interval _W2 between the short-period masks 13 adjacent to each other is preferably the same as the interval between each of the short-period masks 13 at both ends in the width direction and the adjacent long-period masks 12 . In other words, it is preferable that the interval _W1 between the long-period masks 12 adjacent to each other is equally divided by the plurality of short-period masks 13 .

The spacing W ₂ between the short period masks 13 adjacent to each other is preferably larger than the width w ₂ of the short period masks 13 . The ratio (W ₂ / _{w 2 )} of the interval W ₂ between the short-period masks 13 adjacent to each other to the width w 2 of the short-period mask 13 is preferably 2 or more and 20 or less, more preferably 5 or more and 15 or less, and even more preferably. is 8 or more and 12 or less. The ratio (W ₂ / _{w 2 )} of the distance W 2 between the short-period masks 13 adjacent to each other to the width w ₂ of the short-period masks 13 is the distance W ₁ between the long-period masks 12 adjacent to each other. It is preferably less than the ratio of 12 to the width w ₁ (W ₁ /w ₁ ).

The sum of the width _w2 of the short-period mask 13 and the interval _W2 between the short-period masks 13 adjacent to each other, that is, the period _P2 of the short-period mask 13 is preferably 10 μm or more and 80 μm or less, more preferably 15 μm or more and 60 μm. Below, it is more preferably 20 μm or more and 40 μm or less. The thickness of the short-period mask 13 is preferably 10 nm or more and 500 nm or less, more preferably 10 nm or more and 200 nm or less. From the viewpoint of simultaneously forming the long-period mask 12 and the short-period mask 13 on the substrate body 11 , the thickness of the short-period mask 13 is preferably the same as the thickness of the long-period mask 12 . By selectively growing the long-period mask 12, the thickness of the short-period mask 13 can be made thinner than the thickness of the long-period mask 12. FIG.

(Semiconductor crystal growth process)
In the semiconductor crystal growth process, a vapor phase epitaxy apparatus is used, and a long period mask 12 and a short period mask are formed on the base substrate 10 by HVPE (Hydride Vapor Phase Epitaxy), a vapor phase epitaxy method, in a reaction chamber. A source gas is brought into contact with the surface on which 13 is provided to grow a semiconductor GaN crystal. The raw material gas includes GaCl gas obtained from Ga and HCl gas as Ga source gas, and _NH3 gas as N source gas. Further, examples of carrier gas include H ₂ gas and N ₂ gas.

A semiconductor crystal growth step of a method for manufacturing a semiconductor substrate according to an embodiment includes a small triangular facet structure forming step, a large triangular facet structure forming step, and a thick film growth step.

<Small Triangular Facet Structure Forming Step>
In the step of forming a small triangular facet structure, as shown in FIGS. 2A and 2B, GaN is crystal-grown starting from the body surface of the substrate body 11 exposed between the masks of the underlying substrate 10 . At this time, the crystal growth of GaN is restricted by the long-period mask 12 and the short-period mask 13, and epitaxially grows from the body surface of the substrate body 11 exposed between the masks. Therefore, if the body surface of the substrate body 11 exposed between the masks is the c-plane of GaN, the c-plane of GaN is grown. GaN finally converges linearly after the dimensions in the width direction of the long-period mask 12 and the short-period mask 13, which are predetermined directions, gradually narrow from both sides as the crystal grows between the masks.

As described above, on the base substrate 10, ridges formed by crystal growth of GaN are formed so as to form relatively small triangular cross-sectional shapes along the width direction of the long-period mask 12 and the short-period mask 13, respectively. A plurality of small triangular facet structures 21 are formed so that they are arranged side by side in the width direction of the long period mask 12 and the short period mask 13 . Here, the "triangle" in the present application means a triangle composed of three sides of a line segment, or a triangle in which at least one of the three sides bulges outward or sinks inward in an arcuate shape. Also includes approximate triangles.

GaN crystal growth conditions in the step of forming the small triangular facet structure may be appropriately selected so as to be suitable for forming the small triangular facet structure 21 .

<Step of forming large triangular facet structure>
In the large triangular facet structure forming step, GaN is crystal-grown on the small triangular facet structure 21 as shown in FIGS. 3A and 3B. At this time, GaN is epitaxially grown from the surface of the small triangular facet structure 21 . GaN takes in all the small triangular facet structures 21 formed between the long-period masks 12, and the widthwise dimensions of the long-period masks 12 and the short-period masks 13 change from both sides as the crystal grows. After gradually narrowing, it finally converges linearly.

As described above, all the small triangular facet structures 21 between the long-period masks 12 are incorporated on the base substrate 10, and the cross-sectional shapes along the width direction of the long-period masks 12 and the short-period masks 13 are relatively different. A plurality of large triangular facet structures 22 of ridges crystal-grown from GaN so as to form large triangles are formed so that they are arranged side by side in the width direction of the long-period mask 12 and the short-period mask 13. . The step of forming the large triangular facet structure may be performed simultaneously with the step of forming the small triangular facet structure.

The GaN crystal growth conditions in the large triangular facet structure forming step may be the same as those in the small triangular facet structure forming step, and may be appropriately selected so as to be suitable for forming the large triangular facet structure 22 .

<Thick film growth step>
In the thick film growth step, GaN is crystal-grown on the large triangular facet structure 22 . At this time, as shown in FIG. 4A, GaN is epitaxially laterally grown (hereinafter referred to as "ELO growth") from oblique facet planes of the slopes of the plurality of large triangular facet structures 22 so as to be adjacent to each other. A first thick film growth layer 23 is formed so as to fill the recesses between the large triangular facet structures 22 (first thick film growth step). At the same time, GaN is deposited on each of the plurality of large triangular facet structures 22, continuously on top thereof, on the bottom surface of the large triangular facet structure 22, and thus on the substrate body 11 exposed between the masks on the surface of the underlying substrate 10. The crystal grows on the same crystal growth plane as the surface of the main body of the mask, and the dimensions in the width direction of the long-period mask 12 and the short-period mask 13 gradually expand to both sides along with the crystal growth, and the long-period mask 12 and the short-period mask 13 The second thick film growth layer 24 is formed so that the cross-sectional shape along the width direction forms an inverted triangle (second thick film growth step). In addition to these first and second thick film growth layers 23 and 24, the small triangular facet structure 21 and the large triangular facet structure 22 are included to form a single GaN layer 20 (semiconductor layer) as a whole.

Further, if the structure of the underlying substrate 10 and the crystal growth conditions of GaN are appropriately selected, as shown in FIG. A first thick film growth layer 23 is formed so as to fill the recesses between the large triangular facet structures 22 adjacent to each other (first thick film growth step). Thereafter, GaN is deposited on each of the plurality of large triangular facet structures 22 along with the formation of a first thick film growth layer 23, spaced from the tops of the large triangular facet structures 22, and the bottom surfaces of the large triangular facet structures 22. The crystal grows on the same crystal growth plane, and along with the crystal growth, the dimension in the width direction of the long-period mask 12 and the short-period mask 13 gradually expands to both sides, and the width direction of the long-period mask 12 and the short-period mask 13 The second thick film growth layer 24 is formed so that the cross-sectional shape along the line forms an inverted triangle (second thick film growth step). A single GaN layer 20 (semiconductor layer) is formed as a whole including the small triangular facet structure 21 and the large triangular facet structure 22 in addition to the first and second thick film growth layers 23 and 24. .

Here, the "inverted triangle" in the present application means an inverted triangle composed of three line segment sides, and at least one of the three sides bulges outward in an arc or bulges inward. Also includes an immersed approximately inverted triangle.

As the crystal growth of GaN in the first and second thick film growth layers 23 and 24 progresses, as shown in FIGS. 5A (corresponding to FIG. 4A) and 5B (corresponding to FIG. 4B), the first thick film growth layer 23 The filling of the recesses between the large triangular facet structures 22 adjacent to each other is completed, and subsequently the plurality of second thick film growth layers 24 on the plurality of large triangular facet structures 22 are coalesced to form the first thick film. The growth layer 23 is buried, and finally the surface of the GaN layer 20 including the small triangular facet structure 21, the large triangular facet structure 22, and the first and second thick film growth layers 23, 24 is flattened.

The GaN crystal growth conditions in the thick film growth step may be the same as those in the small triangular facet structure forming step or the large triangular facet structure forming step, and are suitable for forming the first and second thick film growth layers 23 and 24. can be selected as appropriate.

The GaN substrate of the semiconductor substrate can be obtained by splitting the GaN layer 20 formed on the underlying substrate 10 from the underlying substrate 10 by cracking in the horizontal direction. According to the method of manufacturing a semiconductor substrate according to this embodiment, as described above, the plurality of small triangular facet structures 21 are formed on the base substrate 10, and two or more of the plurality of small triangular facet structures 21 are formed. By forming a plurality of large triangular facet structures 22 incorporating , a GaN substrate in which dislocations are dispersed can be manufactured. It is considered that this is because the ELO growth from the small triangular facet structure 21 and the ELO growth from the large triangular facet structure 22 cause concentration and dispersion of dislocations twice.

The obtained GaN substrate can be used for semiconductor light emitting devices (LED), semiconductor lasers (LD), solar cells, other electronic devices, and the like. Dislocations are dispersed in this GaN substrate, so it is particularly suitable for use in power devices from the viewpoint of reducing leakage current.

In the above-described embodiment, the underlying substrate 10 provided with the long-period mask 12 and the short-period mask 13 extending in stripes in one direction is used. 6, a long-period mask 12 is provided on the substrate body 11 so as to form a plurality of relatively large hexagonal honeycomb shapes in plan view, and each hexagon of the long-period mask 12 has a , the short-period mask 13 is provided so as to form a plurality of hexagonal honeycomb shapes that are relatively small in plan view, and therefore the long-period mask 12 and the short-period mask 13 extending in stripes in three directions are provided. A base substrate 10 may be used.

In the above embodiment, the short-period mask 13 has a width different from that of the long-period mask 12. However, the present invention is not limited to this. It may be configured to have different thicknesses.

In the above-described embodiment, the triangular facet structure is formed in two steps of the small triangular facet structure 21 and the large triangular facet structure 22 using the base substrate 10 provided with two kinds of masks, the long-period mask 12 and the short-period mask 13. However, the structure is not particularly limited to this, and a structure in which a triangular facet structure is formed in three stages using a base substrate provided with a third mask between short-period masks at regular intervals. , or a configuration in which a triangular facet structure is formed in multiple stages using an underlying substrate provided with four or more kinds of masks.

(Formation of GaN layer)
GaN layer formation experiments were conducted for Examples 1 to 3 and Comparative Example below. Table 1 shows the structure of the base substrate used in each case.

<Example 1>
A SiO 2 long-period mask 12 extending in stripes extending in the a-axis direction on a substrate body 11 obtained by epitaxially growing a GaN film having a thickness of about 3 μm by MOVPE on a sapphire substrate whose main surface is the c _- plane. and a base substrate 10 provided with a short-period mask 13 was produced. As shown in FIG. 7A, the width _w1 of the long-period mask 12 was set to 10 μm, and the interval _W1 between the long-period masks 12 was set to 200 μm. The width _w2 of the short-period masks 13 was 3 μm, the interval _W2 between the short-period masks 13 was 26 μm, and the interval _W1 between the long-period masks 12 was divided into 7 equal parts by the short-period masks 13 .

Then, GaN was crystal-grown on this underlying substrate by the HVPE method. Specifically, as shown in FIG. 8, first, the temperature of the underlying substrate was raised to 500° C. while flowing N ₂ gas. When the temperature of the underlying substrate reached 500° C., the N ₂ gas was stopped and the H ₂ gas and NH ₃ gas were started to flow. The temperature of the underlying substrate was further raised to 1040° C. while flowing H ₂ gas and NH ₃ gas. After that, HCl gas was started to flow in addition to H ₂ gas and NH ₃ gas, and the HCl gas was flowed for 180 minutes to grow a GaN crystal on the underlying substrate (first step). At this time, the flow rate of HCl gas was 0.40 slm and the flow rate of NH ₃ gas was 24.0 slm (V/III ratio=60).

Next, when the supply time of HCl gas reached 180 minutes, the supply of HCl gas was stopped, and then the temperature of the base substrate was raised to 1100° C. while continuously supplying H ₂ gas and NH ₃ gas. When the temperature of the base substrate reached 1100° C., the HCl gas was started to flow again, and the HCl gas was flowed for 330 minutes to grow a GaN crystal (second step). At this time, the flow rate of HCl gas was 0.80 slm and the flow rate of NH ₃ gas was 8.0 slm (V/III ratio=10).

Subsequently, when the supply time of HCl gas reached 330 minutes, the supply of HCl gas was stopped, and the temperature of the underlying substrate was lowered to 1000° C. while continuously supplying H ₂ gas and NH ₃ gas. When the temperature of the base substrate reached 1000° C., the HCl gas was started to flow again, and the HCl gas was flowed for 30 minutes to grow a GaN crystal (third step). At this time, the flow rate of HCl gas was 0.26 slm and the flow rate of NH ₃ gas was 8.0 slm (V/III ratio=30).

When the supply time of HCl gas reached 30 minutes, the supply of HCl gas was stopped, and the temperature of the underlying substrate was lowered to 300° C. while continuously supplying H ₂ gas and NH ₃ gas. When the temperature of the base substrate reached 300° C., the H ₂ gas and NH ₃ gas were stopped, and the N ₂ gas was started to flow, and the substrate was cooled to room temperature.

As a result of the GaN crystal growth in the first to third steps, as shown in FIG. 9, the underlying substrate has a flat surface including a small triangular facet structure, a large triangular facet structure, and first and second thick film growth layers. A fine GaN layer was formed. The crystal growth conditions in the first step are suitable for forming a small triangular facet structure and a large triangular facet structure, and the crystal growth conditions in the second and third steps are those for the first and second thick film growth layers. It is suitable for flattening the surface by forming a

<Example 2>
As shown in FIG. 7B, the width _w2 of the short-period mask 13 is 5 μm, the interval _W2 between the short-period masks 13 is 36 μm, and the interval _W1 between the long-period masks 12 is equally divided into five by the short-period mask 13. A GaN layer was formed in the same manner as in Example 1, except that a divided base substrate 10 was used.

<Example 3>
As shown in FIG. 7C, the width _w2 of the short-period mask 13 is 4 μm, the interval _W2 between the short-period masks 13 is 47 μm, and the interval _W1 between the long-period masks 12 is divided into four by the short-period masks 13. A GaN layer was formed in the same manner as in Example 1, except that a divided base substrate 10 was used.

<Comparative example>
A GaN layer was formed in the same manner as in Examples 1 to 3, except that only the long-period mask was provided and the underlying substrate was not provided with the short-period mask. In this comparative example, a GaN layer with a flat surface including a large triangular facet structure and first and second thick film growth layers was formed on the base substrate by the GaN crystal growth in the first to third steps. .

(Dislocation density distribution)
On the surface of the GaN layer obtained in each of Examples 1 to 3 and Comparative Example, as shown in FIG. It was divided equally into 21 μm×60 μm rectangular regions A, B, C, D, and E, respectively. Then, for each of the A to E regions, the dislocation density was obtained from the dark spot density of the CL image of the surface. Also, the average dislocation density in the A to E regions was calculated.

FIG. 11 shows the distribution of dislocation densities in the A to E regions. 7A to 7C, a base substrate 10 having a long-period mask 12 and a short-period mask 13 provided on a substrate body 11 is used to form a small triangular facet structure and a large triangular facet structure to form GaN crystals. In Examples 1 to 3, in which layers were formed, no large variation in dislocation density was observed between the A to E regions, and therefore it can be seen that the dislocations are dispersed. On the other hand, in the comparative example in which the GaN layer was formed by forming only the large triangular facet structure using the base substrate in which only the long-period mask was provided on the substrate main body, a large variation in dislocation density was observed between the A to E regions. , dislocations are unevenly distributed.

Table 2 shows the average dislocation densities of Examples 1-3 and Comparative Example. According to this, the average dislocation density of Examples 1 to 3 is lower than that of the comparative example. Therefore, in Examples 1 to 3, the dislocations are dispersed and the dislocations are reduced as a whole. I know there is.

INDUSTRIAL APPLICABILITY The present invention is useful in the technical field of methods for manufacturing semiconductor substrates and underlying substrates used therefor.

10 base substrate 11 substrate body 12 long period mask 13 short period mask 20 GaN layer 21 small triangular facet structure 22 large triangular facet structure 23 first thick film growth layer 24 second thick film growth layer

Claims (10)

a substrate main body, a plurality of striped long-period masks provided on the substrate main body at regular intervals, and a fixed period of 15 μm to 80 μm between the adjacent long-period masks on the substrate main body. A base substrate is prepared which includes a plurality of striped short-period masks having different widths from the long-period masks provided at the following intervals, and the substrate main body is exposed between the short-period masks adjacent to each other. and
By crystal-growing a semiconductor starting from the substrate body exposed between the plurality of short-period masks in the underlying substrate, the cross-sectional shapes along the width direction of the long-period mask and the short-period mask are changed relative to each other. forming a plurality of small triangular facet structures in which the semiconductor is crystal-grown so as to form small triangles in the width direction so that they are arranged side by side in the width direction of the long-period mask and the short-period mask;
Two or more of the plurality of small triangular facet structures are incorporated between the plurality of long-period masks on the underlying substrate, and cross-sectional shapes along the width direction of the long-period mask and the short-period mask are opposite to each other. a step of forming a plurality of large triangular facet structures in which the semiconductor is crystal-grown so as to form a relatively large triangle so that they are arranged side by side in the width direction of the long-period mask and the short-period mask; ,
A method of manufacturing a semiconductor substrate comprising: In the method for manufacturing a semiconductor substrate according to claim 1,
forming a first thick film growth layer so that the semiconductor epitaxially laterally grows from the slanted facet surfaces of each of the plurality of large triangular facet structures to fill recesses between the adjacent large triangular facet structures; ,
On each of the plurality of large triangular facet structures, the semiconductor is the same as the bottom surface of the large triangular facet structure so that cross-sectional shapes along the width direction of the long-period mask and the short-period mask form an inverted triangle. forming a crystal-grown second thick film growth layer on the crystal growth surface of
further comprising
A method of manufacturing a semiconductor substrate, wherein the plurality of second thick film growth layers on the plurality of large triangular facet structures are merged to bury the first thick film growth layer. In the method for manufacturing a semiconductor substrate according to claim 1 or 2,
A method for manufacturing a semiconductor substrate, wherein the semiconductor is GaN. In the method for manufacturing a semiconductor substrate according to claim 1,
A method for manufacturing a semiconductor substrate, wherein the distance between the long-period masks adjacent to each other is 100 μm or more and 3000 μm or less. In the method for manufacturing a semiconductor substrate according to claim 1,
A method for manufacturing a semiconductor substrate, wherein the plurality of long-period masks are provided on the substrate body at a period of 100 μm or more and 1000 μm or less. In the method for manufacturing a semiconductor substrate according to claim 1,
A method of manufacturing a semiconductor substrate, wherein the ratio of the width of the short-period mask to the width of the long-period mask is 1/10 or more and 1/2 or less. In the method for manufacturing a semiconductor substrate according to claim 1,
A method of manufacturing a semiconductor substrate, wherein the ratio of the interval between the short-period masks adjacent to each other to the interval between the long-period masks adjacent to each other is 1/10 or more and 1/2 or less. In the method for manufacturing a semiconductor substrate according to claim 1,
A method of manufacturing a semiconductor substrate, wherein the distance between the short-period masks adjacent to each other is larger than the width of the short-period masks. In the method for manufacturing a semiconductor substrate according to claim 8,
A method for manufacturing a semiconductor substrate, wherein the ratio of the distance between the short-period masks adjacent to each other to the width of the short-period mask is 2 or more and 20 or less. A base substrate used for manufacturing a semiconductor substrate,
a substrate body;
a plurality of striped long-period masks provided on the substrate body at regular intervals;
a plurality of striped short-period masks having a width different from that of the long-period masks, provided on the substrate main body with a constant interval of 15 μm or more and 80 μm or less between the adjacent long-period masks;
with
A base substrate in which the substrate body is exposed between the short-period masks adjacent to each other.

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