Indium phosphide substrate and method for manufacturing indium phosphide crystals

Abstract

This indium phosphide substrate has a principal surface. The diameter of the principal surface is 149–205 mm. The principal surface is formed by an outer peripheral region and a central region. The central region is divided into first square regions with sides 1 mm in length and arranged in a lattice formation. When a square shape that encloses nine of the first square regions and has sides 3 mm in length is moved 1 mm at a time in a first direction and in a second direction, regions specified by the square shape are considered a plurality of second square regions. The proportion of the number of the plurality of second square regions with a dislocation density of 0 / cm2 to the total number of the plurality of second square regions is at least 30%.

Description

Method for manufacturing indium phosphide substrates and indium phosphide crystals

[0001] This disclosure relates to a method for producing indium phosphide substrates and indium phosphide crystals.

[0002] Japanese Patent Publication No. 2023-516634 (Patent Document 1) describes an indium phosphide substrate having a diameter of 6 inches or more.

[0003] Special Publication No. 2023-516634

[0004] The indium phosphide substrate according to this disclosure comprises a main surface. The diameter of the main surface is 149 mm or more and 205 mm or less. The average dislocation density on the main surface is 0 / cm². ２ More than 50 / cm ２ The following is the case: The main surface is formed by an outer region within 5 mm of the outer edge and a central region surrounded by the outer region. The central region is divided by first square regions with a side length of 1 mm and arranged in a grid. When a square with a side length of 3 mm that surrounds nine first square regions is moved by 1 mm along the first direction in which the first side of the first square region extends and the second direction in which the second side connected to the first side extends, the region identified by the square is defined as multiple second square regions. When the dislocation density in each of the multiple second square regions is measured, the dislocation density relative to the total number of multiple second square regions is 0 / cm². ２ The proportion of the number of multiple second square regions that meet this condition is 30% or more.

[0005] Figure 1 is a schematic plan view showing the configuration of an indium phosphide substrate according to the first embodiment. Figure 2 is a schematic side view showing the configuration of an indium phosphide substrate according to the first embodiment. Figure 3 is a schematic plan view illustrating the first square region. Figure 4 is a schematic plan view illustrating the second square region. Figure 5 is a schematic plan view illustrating the third square region. Figure 6 is a schematic diagram illustrating the dislocation-free region ratio when dislocations are relatively uniformly distributed on the first main surface. Figure 7 is a schematic diagram illustrating the dislocation-free region ratio when dislocations are relatively concentrated on the first main surface. Figure 8 is a schematic plan view showing the measurement position of the carrier concentration. Figure 9 is a schematic diagram showing the configuration of a sample for measurement. Figure 10 is a schematic cross-sectional view showing the configuration of an indium phosphide crystal manufacturing apparatus according to the first embodiment. Figure 11 is a schematic plan view showing the configuration of the manufacturing apparatus viewed in the vertical downward direction. Figure 12 is a schematic plan view showing the configuration of a modified example of the manufacturing apparatus according to the first embodiment. Figure 13 is a schematic flow diagram illustrating the manufacturing method of an indium phosphide crystal according to the first embodiment. Figure 14 is a schematic cross-sectional view showing a crucible in which a seed crystal, indium phosphide raw material, and encapsulating material are arranged. Figure 15 is a schematic cross-sectional view showing the crystal growth process. Figure 16 is a schematic cross-sectional view showing the crystal growth process. Figure 17 is a schematic side view showing the structure of an indium phosphide crystal according to the first embodiment. Figure 18 is a schematic plan view showing the structure of a manufacturing apparatus according to the second embodiment. Figure 19 is a schematic first view showing the distribution of dislocations on the first main surface of an indium phosphide substrate relating to sample 1. Figure 20 is a schematic second view showing the distribution of dislocations on the first main surface of an indium phosphide substrate relating to sample 1. Figure 21 is a schematic first view showing the distribution of dislocations on the first main surface of an indium phosphide substrate relating to sample 6. Figure 22 is a schematic second view showing the distribution of dislocations on the first main surface of an indium phosphide substrate relating to sample 6.

[0006] [Problems this disclosure aims to solve] When semiconductor devices are manufactured using indium phosphide with a diameter of 6 inches or more, the dark current of the manufactured semiconductor device sometimes increases. In this case, the device yield decreases.

[0007] The purpose of this disclosure is to provide a method for manufacturing indium phosphide substrates and indium phosphide crystals that can improve device yield.

[0008] [Effects of this disclosure] According to this disclosure, it is possible to provide a method for manufacturing indium phosphide substrates and indium phosphide crystals that can improve device yield.

[0009] [Outline of Embodiments] First, an outline of the embodiments of the present disclosure (hereinafter also referred to as these embodiments) will be described.

[0010] (1) The indium phosphide substrate according to this disclosure has a main surface. The diameter of the main surface is 149 mm or more and 205 mm or less. The average dislocation density on the main surface is 0 / cm ２ More than 50 / cm ２ The following is the case: The main surface is formed by an outer region within 5 mm of the outer edge and a central region surrounded by the outer region. The central region is divided by first square regions with a side length of 1 mm and arranged in a grid. When a square with a side length of 3 mm that surrounds nine first square regions is moved by 1 mm along the first direction in which the first side of the first square region extends and the second direction in which the second side connected to the first side extends, the region identified by the square is defined as multiple second square regions. When the dislocation density in each of the multiple second square regions is measured, the dislocation density relative to the total number of multiple second square regions is 0 / cm². ２ The proportion of the number of multiple second square regions is 30% or more. This improves the device yield.

[0011] (2) In the case of the indium phosphide substrate described in (1) above, the dislocation density in the first square region is measured and the dislocation density is 0 / cm². ２ The first square region may be defined as a dislocation-free region. Among the regions formed by continuous dislocation-free regions along either the first or second direction, the region with the largest area may be defined as a continuous dislocation-free region. The ratio of the length of the continuous dislocation-free region in the longitudinal direction to the diameter of the main surface may be 70% or more and 90% or less. This can effectively improve device yield.

[0012] (3) According to the indium phosphide substrate according to (1) or (2) above, the carrier concentration at the center of the main surface may be 5.0×10 １８ / cm ３ or less. Thus, even when the carrier concentration is relatively low, the device yield can be improved.

[0013] (4) According to the indium phosphide substrate according to any one of (1) to (3) above, the carrier concentration at the center of the main surface may be 1.0×10 １８ / cm ３ or more. Thereby, an excessive increase in the dislocation density can be suppressed.

[0014] (5) The method for manufacturing an indium phosphide crystal according to the present disclosure uses the vertical boat method. The method for manufacturing an indium phosphide crystal has the following steps. A seed crystal and a raw material are arranged inside a crucible surrounded by a heating section. A raw material melt is prepared by melting a part of the seed crystal and the raw material using the heating section. An indium phosphide crystal grows on the remaining part of the seed crystal by solidifying the raw material melt. The direction perpendicular to the central axis of the crucible and the directions of 0°, 90°, 180°, and 270° as viewed from the central axis are defined as the 0° direction, 90° direction, 180° direction, and 270° direction, respectively. At least at the height where the solid-liquid interface is located, in the 0° direction, the thinnest part of the heating section in the radial direction of the crucible is located. At least at the height where the solid-liquid interface is located, the thickness of the heating section in the 180° direction is thinner than the thicknesses of the heating sections in the 90° and 270° directions, respectively. At least at the height where the solid-liquid interface is located, the value obtained by dividing the thickness of the thickest part of the heating section in the radial direction by the thickness of the thinnest part of the heating section in the radial direction is 1.05 or more and 1.5 or less. Thereby, when a semiconductor device is manufactured using the indium phosphide crystal, the device yield can be improved.

[0015] (6) According to the method for manufacturing an indium phosphide crystal according to (5) above, at least at the height where the solid-liquid interface is located, the thickness of the heating portion in the 0° direction may be the same as the thickness of the heating portion in the 180° direction. At least at the height where the solid-liquid interface is located, the thickness of the heating portion in the 90° direction may be the same as the thickness of the heating portion in the 270° direction. Thereby, when a semiconductor device is manufactured using an indium phosphide crystal, the device yield can be effectively improved.

[0016] [Details of Embodiment] Hereinafter, details of the embodiment of the present disclosure will be described based on the drawings. In the following drawings, the same or corresponding parts are given the same reference numerals, and the description thereof will not be repeated. In the crystallographic description of this specification, the aggregate orientation is indicated by <>, and the aggregate plane is indicated by {}. Also, for negative indices, in crystallography, a "-" (bar) is attached above the number, but in this specification, a negative sign is attached before the number.

[0017] (First Embodiment) <Indium Phosphide Substrate> First, the configuration of an indium phosphide substrate 100 according to the first embodiment will be described. Hereinafter, the indium phosphide substrate 100 is also referred to as an InP substrate 100. FIG. 1 is a schematic plan view showing the configuration of the InP substrate 100 according to the first embodiment. FIG. 2 is a schematic side view showing the configuration of the InP substrate 100 according to the first embodiment.

[0018] As shown in FIGS. 1 and 2, the InP substrate 100 has a first main surface 1, a second main surface 2, an outer peripheral surface 3, and an outer peripheral edge 8. The InP substrate 100 is formed of indium phosphide (InP). The crystal structure of the InP substrate 100 is cubic.

[0019] As shown in FIG. 2, the second main surface 2 is opposite to the first main surface 1. The outer peripheral surface 3 is continuous with each of the first main surface 1 and the second main surface 2. The outer peripheral edge 8 is a ridge line between the first main surface 1 and the outer peripheral surface 3.

[0020] The direction from the first major surface 1 to the second major surface 2 is parallel to the growth direction of the indium phosphide crystal when manufacturing the InP substrate 100. The thickness of the InP substrate 100 in the direction from the first major surface 1 to the second major surface 2 is, for example, less than 1 mm.

[0021] In FIG. 1, the configuration of the InP substrate 100 as viewed perpendicularly to the first major surface 1 is shown. As shown in FIG. 1, when viewed perpendicularly to the first major surface 1, the shape of the first major surface 1 is, for example, circular. The first major surface 1 has a first center A1. The first center A1 is, for example, the center of the outer peripheral edge 8.

[0022] The first major surface 1 is, for example, a {100} plane. The first major surface 1 may be inclined with respect to the {100} plane, for example. When the first major surface 1 is inclined with respect to the {100} plane, the inclination angle (off angle) of the first major surface 1 with respect to the {100} plane is, for example, 0° or more and 15° or less.

[0023] The diameter D of the first major surface 1 is 149 mm or more and 205 mm or less. The diameter D may be, for example, 6 inches (152.4 mm) or more. The diameter D may be, for example, 8 inches (203.2 mm) or less. The diameter D is the longest distance between two different points on the outer peripheral edge 8.

[0024] On the outer peripheral surface 3, at least one of a notch, an orientation flat (OF), or an index flat (IF) may be provided. When at least one of a notch, an OF, or an IF is provided on the outer peripheral surface 3, the center of the circle overlapping with the portion of the outer peripheral edge 8 that is arc-shaped when viewed perpendicularly to the first major surface 1 is taken as the first center A1.

[0025] (Dislocation density) In the InP substrate 100 according to the first embodiment, dislocations are present. In this specification, "dislocation" is an aspect of crystal defects, and in this technical field, a dislocation corresponds to an etch pit that is confirmed using the measurement method described later. Therefore, by measuring the number of these etch pits, the number of dislocations can be indirectly measured. In this specification, 1 cm ２The dislocation density is measured by determining the number of etch pits per unit area. The details of the measurement area where the dislocation density is measured are described below.

[0026] <First Square Region> Figure 3 is a schematic plan view illustrating the first square region 51. As shown in Figure 3, the first main surface 1 is formed by an outer peripheral region 18 and a central region 19. The outer peripheral region 18 is connected to the outer peripheral edge 8. The outer peripheral region 18 is the region within 5 mm of the outer peripheral edge 8. From another point of view, the distance between the boundary between the outer peripheral region 18 and the central region 19 and the outer peripheral edge 8 is 5 mm. The central region 19 is surrounded by the outer peripheral region 18. The central region 19 is connected to the outer peripheral region 18.

[0027] As shown in Figure 3, in the measurement of dislocation density, the central region 19 is divided into a plurality of first square regions 51. The plurality of first square regions 51 are arranged in a grid. Specifically, the plurality of first square regions 51 are arranged in a grid along a first direction 101 and a second direction 102. The first direction 101 is, for example, the <0-11> direction. The second direction 102 is perpendicular to the first direction 101. The second direction 102 is, for example, the <011> direction.

[0028] Multiple first square regions 51 may be arranged in the central region 19 such that the number of multiple first square regions 51 is maximized. Note that square regions (not shown) that intersect with the boundary between the outer region 18 and the central region 19 are not considered first square regions 51.

[0029] When viewed perpendicular to the first principal surface 1, each of the multiple first square regions 51 is square in shape. The length of one side (first length L1) of each of the multiple first square regions 51 is 1 mm. The first side of each of the multiple first square regions 51 extends along the first direction 101. The second side of each of the multiple first square regions 51 extends along the second direction 102. The second side is connected to the first side.

[0030] Dislocation density is 0 / cm ２ The first square region 51 is defined as the dislocation-free region 31. In other words, there are no dislocations in the dislocation-free region 31. The dislocation density is 0 / cm². ２The larger first square region 51 is designated as the dislocation region 32. In Figure 3, the hatched region is the dislocation region 32. Details of the dislocation density will be described later.

[0031] Among the regions formed by multiple dislocation-free regions 31 that are continuous along either the first direction 101 or the second direction 102, the region with the largest area is defined as the continuous dislocation-free region 30. Note that two dislocation-free regions 31 are continuous if one side of each adjacent dislocation-free region 31 is touching the other. In Figure 3, the outer edge of the continuous dislocation-free region 30 is shown using a thick line. The continuous dislocation-free region 30 is formed by multiple dislocation-free regions 31. Viewed perpendicular to the first direction 101, the shape of the continuous dislocation-free region 30 is rectangular. The longitudinal direction of the continuous dislocation-free region 30 is, for example, the first direction 101.

[0032] The length of the continuous dislocation-free region 30 in the longitudinal direction is defined as the second length L2. The second length L2 is, for example, 100 mm or more and 160 mm or less. The ratio of the second length L2 to the diameter D of the first main surface 1 is, for example, 70% or more and 90% or less. The ratio of the second length L2 to the diameter D may be, for example, 72% or more, 75% or more, or 80% or more. The ratio of the second length L2 to the diameter D may be 88% or less, or 86% or less.

[0033] Furthermore, within the continuous dislocation-free region 30, multiple dislocation-free regions 31 may be continuous along the second direction 102. In other words, the longitudinal direction of the continuous dislocation-free region 30 may be the second direction 102.

[0034] <Second Square Region> Figure 4 is a schematic plan view illustrating the second square region 52. As shown in Figure 4, multiple second square regions 52 are identified in the central region 19. Specifically, when the square X is moved 1 mm along the first direction 101 and the second direction 102, the regions identified by the square X are considered to be multiple second square regions 52.

[0035] In Figure 4, square X is shown using a thick line. For the sake of explanation, three overlapping squares X are shown in Figure 4, and one of the second square regions 52 identified by square X is hatched.

[0036] Square X encloses nine first square regions 51. The length of one side of square X (third length L3) is 3 mm. Multiple second square regions 52 are specified such that the number of multiple second square regions 52 is maximized.

[0037] Each of the multiple second square regions 52 contains nine first square regions 51. The centers (second centers A2) of each of the multiple second square regions 52 are arranged in a grid pattern at 1 mm intervals along the first direction 101 and the second direction 102. In other words, the distance between two adjacent second centers A2 (first distance E1) is 1 mm. The number of second centers A2 identified in the central region 19 is the same as the number of multiple second square regions 52.

[0038] When viewed perpendicular to the first principal surface 1, each of the multiple second square regions 52 is square in shape. The length of one side of each of the multiple second square regions 52 is 3 mm. Of the multiple second square regions 52, two adjacent second square regions 52 with the second center A2 overlap partially. The area of ​​the overlapping portion of two adjacent second square regions 52 with the second center A2 is 2 / 3 of the area of ​​one second square region 52.

[0039] <Third Square Region> Figure 5 is a schematic plan view illustrating the third square region 53. As shown in Figure 5, multiple third square regions 53 are identified in the central region 19. Each of the multiple third square regions 53 contains nine first square regions 51. When viewed perpendicular to the first principal plane 1, each of the multiple third square regions 53 is square in shape. The length of one side (fourth length L4) of each of the multiple third square regions 53 is 3 mm.

[0040] The centers (third centers A3) of each of the multiple third square regions 53 are arranged in a grid pattern at 3 mm intervals along the first direction 101 and the second direction 102. In other words, the distance between two adjacent third centers A3 (second distance E2) is 3 mm. The multiple third square regions 53 do not overlap each other. One side of each of two adjacent third square regions 53 touches each other.

[0041] <Method for Measuring Dislocation Density> Next, the method for measuring dislocation density will be explained. First, a Huber etching solution is prepared. The Huber etching solution contains phosphoric acid and hydrogen bromide. The mass ratio of phosphoric acid to hydrogen bromide in the Huber etching solution is 2:1. The temperature of the Huber etching solution is, for example, 20°C. For example, the InP substrate 100 is immersed in the Huber etching solution for a period of 2 to 7 minutes. This forms etch pits on the first main surface 1.

[0042] Next, the number of etch pits in each of the multiple first square regions 51 is measured using an optical microscope. The magnification of the optical microscope used for this measurement is, for example, between 25x and 100x. The value obtained by dividing the measured number of etch pits by the area of ​​the first square region 51 is defined as the dislocation density in the first square region 51. A dislocation density of 0 / cm² is considered to be the value obtained by this measurement. ２ The first square region 51 is identified as the dislocation-free region 31, where the dislocation density is 0 / cm². ２ A larger first square region 51 is identified as the dislocation region 32.

[0043] The dislocation density in the second square region 52 is determined by dividing the sum of the dislocation densities in each of the nine first square regions 51 contained within the second square region 52 by nine. Similarly, the dislocation density in the third square region 53 is determined by dividing the sum of the dislocation densities in each of the nine first square regions 51 contained within the third square region 53 by nine.

[0044] The average dislocation density on the first main surface 1 is obtained by dividing the sum of the dislocation densities in each of the multiple first square regions 51 by the number of the multiple first square regions 51. The average dislocation density on the first main surface 1 is 0 / cm². ２More than 50 / cm ２ The following applies: The average dislocation density on the first main surface 1 is, for example, 10 / cm³. ２ The above is also 20 / cm ２ The above may also be the case. The average dislocation density on the first main surface 1 is, for example, 48 / cm³. ２ The following may also be acceptable, or 46 / cm ２ The following is also acceptable.

[0045] The dislocation density relative to the total number of dislocations in the first square region 51 is 0 / cm². ２ The ratio of the number of multiple first square regions 51 is called the first dislocation-free region ratio. The first dislocation-free region ratio is, for example, 70% or more and 80% or less.

[0046] The dislocation density relative to the total number in the second square region 52 is 0 / cm². ２ The ratio of the number of multiple second square regions 52 is called the second dislocation-free region ratio. The second dislocation-free region ratio is lower than the first dislocation-free region ratio. The second dislocation-free region ratio is 30% or more. The second dislocation-free region ratio may be, for example, 31% or more, or 32% or more. The second dislocation-free region ratio may be, for example, 60% or less, or 50% or less.

[0047] The dislocation density relative to the total number of dislocations in the third square region 53 is 0 / cm². ２ The ratio of the number of multiple third square regions 53 is called the third dislocation-free region rate. The third dislocation-free region rate is lower than the second dislocation-free region rate. The third dislocation-free region rate is, for example, 20% or more and less than 30%.

[0048] Figure 6 is a schematic diagram illustrating the dislocation-free region ratio when dislocations are relatively uniformly distributed on the first main surface 1. Figure 7 is a schematic diagram illustrating the dislocation-free region ratio when dislocations are relatively concentrated on the first main surface 1. In Figures 6 and 7, as an example, the dislocation-free region ratio is shown when 14 dislocation regions 32 are included in a 12 × 12 first square region 51. In Figures 6 and 7, hatched areas indicate regions with dislocations. In Figures 6 and 7, for the sake of explanation, the second square region 52 is shown using a 1 mm × 1 mm square centered on the second center A2.

[0049] As shown in Figures 6 and 7, the first dislocation-free region ratio and the third dislocation-free region ratio are the same in both the example shown in Figure 6 and the example shown in Figure 7. On the other hand, the second dislocation-free region ratio in the example shown in Figure 7 is higher than the second dislocation-free region ratio in the example shown in Figure 6. Therefore, it can be understood that the second dislocation-free region ratio represents the size of the continuous dislocation-free region 31 in the InP substrate 100.

[0050] <Carrier Concentration> The InP substrate 100 contains at least one of the following as an impurity: sulfur (S), tin (Sn), or zinc (Zn). Specifically, the InP substrate 100 may contain at least one of S or Sn as an n-type impurity, for example. The InP substrate 100 may also contain Zn as a p-type impurity.

[0051] The carrier concentration at the center of the first main surface 1 (first center A1) is, for example, 1.0 × 10⁻⁶. １８ / cm ３ That concludes the explanation. The carrier concentration in the first center A1 is, for example, 1.5 × 10⁻⁶. １８ / cm ３ The above is also acceptable, or 2.0 x 10 １８ / cm ３ The above may also be the case. The carrier concentration in the first center A1 is, for example, 5.0 × 10⁻⁶. １８ / cm ３ The following applies: The carrier concentration in the first center A1 is, for example, 4.5 × 10⁻⁶. １８ / cm ３ The following is also acceptable, or 4.0 x 10 １８ / cm ３ The following is also acceptable.

[0052] <Method for Measuring Carrier Concentration> Next, the method for measuring the carrier concentration at the first center A1 will be explained. Figure 8 is a schematic plan view showing the measurement location of the carrier concentration. As shown in Figure 8, the measurement area 6 is identified on the first main surface 1. The measurement area 6 is centered on the first center A1. When viewed perpendicular to the first main surface 1, the measurement area 6 is a square. The length of one side of the measurement area 6 (fifth length L5) is 4 mm.

[0053] In the measurement area 6, the carrier concentration is measured using a Hall assay applying the Van der Pauw method. First, a rectangular section 70 is prepared by dividing the InP substrate 100 along the outer edge of the measurement area 6. Specifically, the rectangular section 70 is prepared by cutting the InP substrate 100 with a cleavage and dicing saw, for example. The size of the rectangular section 70 is, for example, 4 mm in length, 4 mm in width, and 600 μm in thickness.

[0054] Figure 9 is a schematic diagram showing the configuration of the measurement sample 77. As shown in Figure 9, measurement electrodes 78 are formed at the four corners of the rectangular section 70. The shape of the measurement electrodes 78 is, for example, rectangular. The measurement electrodes 78 are formed from an alloy containing gold, nickel, and germanium. In this way, the measurement sample 77 is prepared using the rectangular section 70. The shape of the measurement electrodes 78 may be fan-shaped or circular.

[0055] A Hall assay using the Van der Pauw method is performed on the measurement sample 77. The measurement temperature is set to room temperature (25°C). This determines the carrier concentration of the measurement sample 77. The carrier concentration of the measurement sample 77 is defined as the carrier concentration at the center of the first main surface 1.

[0056] (Indium phosphide crystal manufacturing apparatus) Next, the configuration of the indium phosphide crystal manufacturing apparatus 300 (hereinafter also simply referred to as the manufacturing apparatus 300) according to the first embodiment will be described. Figure 10 is a schematic cross-sectional view showing the configuration of the indium phosphide crystal manufacturing apparatus 300 according to the first embodiment. As shown in Figure 10, the manufacturing apparatus 300 mainly comprises a crucible 40, a crucible holder 49, a heating unit 48, and a high-pressure vessel (not shown).

[0057] The crucible 40 is made of a material that can withstand the heating required to melt the raw materials. Specifically, the crucible 40 is made of, for example, pyrolytic boron nitride (pBN). The crucible 40 has a seed crystal holding section 41 and a crystal growth section 42.

[0058] The crucible 40 has a cylindrical shape. The crucible 40 opens in a vertically upward direction 111. The vertically upward direction 111 is the same direction as the growth direction of the indium phosphide crystal 200, which will be described later. The direction opposite to the vertically upward direction 111 is the vertically downward direction 112. The central axis C of the crucible 40 extends along the vertically upward direction 111. The direction perpendicular to the central axis C and extending from the central axis C toward the crystal growth section 42 is the radial direction of the crucible 40.

[0059] The seed crystal holding section 41 has a bottomed cylindrical shape. The seed crystal holding section 41 holds the seed crystal. The seed crystal holding section 41 opens vertically upward 111. The crystal growth section 42 holds the raw material. The crystal growth section 42 is connected to the seed crystal holding section 41. The crystal growth section 42 is provided vertically upward 111 relative to the seed crystal holding section 41. The crystal growth section 42 has a diameter-increasing section 42a and a straight section 42b.

[0060] The diameter-increasing portion 42a is connected to the seed crystal holding portion 41. The diameter-increasing portion 42a has an annular shape. The diameter-increasing portion 42a surrounds the central axis C. As the diameter-increasing portion 42a moves away from the seed crystal holding portion 41 along the vertical upward direction 111, both the inner diameter and outer diameter of the diameter-increasing portion 42a increase.

[0061] The straight section 42b is connected to the diameter-increasing section 42a. The straight section 42b is positioned vertically upward 111 relative to the diameter-increasing section 42a. The shape of the straight section 42b is a hollow cylinder. When viewed vertically downward 112, the shape of the straight section 42b is circular. The straight section 42b surrounds the central axis C. The inner diameter of the straight section 42b is, for example, 100 mm or more. The inner diameter of the straight section 42b is the inner diameter of the crucible 40.

[0062] The heating unit 48 heats the crucible 40. Specifically, the heating unit 48 heats the crucible 40 when power is supplied to it. The heating unit 48 is, for example, a resistance heater. From another point of view, the crucible 40 is heated, for example, by a resistance heating method. The heating unit 48 may also be a coil. From another point of view, the crucible 40 may be heated by a high-frequency induction heating method.

[0063] The heating section 48 has a cylindrical shape. The heating section 48 surrounds the crucible 40. The heating section 48 is spaced apart from the crucible 40. The central axis of the heating section 48 may coincide with the central axis C of the crucible 40. From another perspective, the crucible 40 and the heating section 48 are arranged concentrically around the central axis C.

[0064] The heating section 48 includes, for example, an upper heating member 48a and a lower heating member 48b. The upper heating member 48a surrounds the crystal growth section 42. When viewed in the vertically downward direction 112, the shape of the upper heating member 48a is annular. The lower heating member 48b is provided vertically downward 112 relative to the upper heating member 48a. The lower heating member 48b surrounds the seed crystal holding section 41. When viewed in the vertically downward direction 112, the shape of the lower heating member 48b is annular.

[0065] The crucible holder 49 holds the crucible 40. The crucible holder 49 surrounds the seed crystal holding section 41 and the diameter increasing section 42a. A high-pressure vessel (not shown) surrounds the crucible 40 and the heating section 48.

[0066] Figure 11 is a schematic plan view showing the configuration of the manufacturing apparatus 300 as seen in the vertically downward direction 112. Hereinafter, the upper heating member 48a and the lower heating member 48b will be collectively referred to as the heating section 48. As shown in Figure 11, the thickness of the heating section 48 in the radial direction may vary along the circumferential direction R. When viewed in the vertically downward direction 112, the circumferential direction R is the direction of rotation clockwise around the central axis C.

[0067] The thinnest part of the heating section 48 in the radial direction is called the thinnest part. When viewed in the vertically downward direction 112, the direction from the central axis C toward the thinnest part is defined as 0°. Note that, as shown in Figure 11, the heating section 48 may have two thinnest parts (first thinnest part 61a, second thinnest part 61b). In this case, the direction from the central axis C toward any one of the two thinnest parts is defined as the 0° direction.

[0068] The directions perpendicular to the central axis C, and the directions at 0°, 90°, 180°, and 270° relative to the central axis C, are referred to as the 0° direction, 90° direction, 180° direction, and 270° direction, respectively. As shown in Figure 11, when viewed in the vertically downward direction 112, the 90° direction is the direction inclined 90° in the circumferential direction R relative to the 0° direction.

[0069] In the 0° direction, the first thinnest portion 61a is located. The thickness of the heating portion 48 in the 0° direction may be the same as, for example, the thickness of the heating portion 48 in the 180° direction. In other words, the second thinnest portion 61b is located in the 180° direction. From another point of view, the thickness of the heating portion 48 in the 180° direction is thinner than the thickness of the heating portion 48 in the 90° direction and the 270° direction, respectively. The central axis C is located between the first thinnest portion 61a and the second thinnest portion 61b.

[0070] The portion of the heating section 48 with the greatest thickness in the radial direction is referred to as the thickest part. The heating section 48 may have two thickest parts (a first thickest part 62a and a second thickest part 62b). The first thickest part 62a is located in the 90° direction. The second thickest part 62b is located in the 270° direction. From another point of view, the thickness of the heating section 48 in the 90° direction may be the same as the thickness of the heating section 48 in the 270° direction. The central axis C is located between the first thickest part 62a and the second thickest part 62b.

[0071] The value obtained by dividing the thickness of the thickest part 62 (second thickness T2) by the thickness of the thinnest part 61 (first thickness T1) is 1.05 or more and 1.5 or less. The value obtained by dividing the second thickness T2 by the first thickness T1 may be, for example, 1.10 or more, or 1.15 or more. The value obtained by dividing the second thickness T2 by the first thickness T1 may be, for example, 1.45 or less, or 1.40 or less.

[0072] When viewed vertically downward 112, the outer circumferential surface of the heating section 48 is, for example, circular. When viewed vertically downward 112, the inner circumferential surface of the heating section 48 is, for example, elliptical with its major axis extending along the 0° direction. As the circumferential direction R moves from the 0° direction to the 90° direction, the thickness of the heating section 48 in the radial direction increases, for example. As the circumferential direction R moves from the 90° direction to the 180° direction, the thickness of the heating section 48 in the radial direction decreases, for example.

[0073] As you move along the circumferential direction R from the 180° direction to the 270° direction, for example, the thickness of the heating portion 48 in the radial direction increases. As you move along the circumferential direction R from the 270° direction to the 0° direction, for example, the thickness of the heating portion 48 in the radial direction decreases.

[0074] When viewed in the vertically downward direction 112, the shape of the heating section 48 may be twice symmetrical about the central axis C. From another point of view, when viewed in the vertically downward direction 112, the outer shape of the heating section 48 may overlap with the outer shape of the heating section 48 rotated 180° about the central axis C.

[0075] <Modified Manufacturing Apparatus> Figure 12 is a schematic plan view showing a modified configuration of the manufacturing apparatus 300 according to the first embodiment. As shown in Figure 12, the heating section 48 may have a first section 66 and a second section 67. The first section 66 is a section whose thickness changes along the circumferential direction R. The first section 66 forms, for example, the thinnest section. From another point of view, the first section 66 is located, for example, in the 0° direction and the 180° direction. The first section 66 extends, for example, along the circumferential direction R from -30° (330°) to 30°. The first section 66 extends, for example, along the circumferential direction R from 150° to 210°.

[0076] The second portion 67 is a portion whose thickness does not change along the circumferential direction R. The second portion 67 is connected to the first portion 66. The second portion 67 forms, for example, the thickest part. From another point of view, the second portion 67 is located, for example, in the 90° direction and the 270° direction. Although not shown, the first portion 66 may form the thickest part and the second portion 67 may form the thinnest part.

[0077] (Method for manufacturing indium phosphide crystals) Next, a method for manufacturing indium phosphide crystals 200 according to the first embodiment will be described. The InP substrate 100 is manufactured using the vertical boat method. In this specification, the vertical boat method includes the Vertical Bridgeman (VB) method, the Vertical Gradient Freeze (VGF) method, and a hybrid method combining the VB method and the VGF method. Below, as an example, a method for manufacturing indium phosphide crystals 200 using the VB method will be described.

[0078] Figure 13 is a schematic flowchart showing the method for producing indium phosphide crystals 200 according to the first embodiment. As shown in Figure 13, the method for producing indium phosphide crystals 200 according to the first embodiment mainly comprises the steps of preparing a manufacturing apparatus (S10), arranging raw materials (S20), melting the raw materials (S30), growing crystals (S40), and cutting crystals (S50).

[0079] First, a step (S10) of preparing the manufacturing apparatus is carried out. Specifically, the manufacturing apparatus 300 according to the first embodiment described above (see Figures 10 and 11) is prepared. In the step (S10) of preparing the manufacturing apparatus, the crucible 40 is heated in an oxygen atmosphere, thereby coating the surface of the crucible 40 with boron oxide (B ２ O ３ A film (not shown) may be formed. The boron oxide film functions as a sealant.

[0080] Next, the process of arranging the raw materials (S20) is carried out. Figure 14 is a schematic cross-sectional view of the crucible 40 in which the seed crystal 84, indium phosphide raw material 85, and sealing material 86 are arranged.

[0081] As shown in Figure 14, a seed crystal 84 is placed inside the seed crystal holding section 41. The seed crystal 84 is formed of InP. The seed crystal 84 is positioned such that, when viewed in the vertical downward direction 112, the <0-11> direction of the seed crystal 84 is parallel to the 0° direction of the manufacturing apparatus 300 (see Figure 11).

[0082] The seed crystal 84 may contain elements that the InP substrate 100 described above contains as impurities. Multiple indium phosphide raw materials 85 are arranged on the seed crystal 84. Each of the multiple indium phosphide raw materials 85 is formed of polycrystalline indium phosphide.

[0083] Each of the multiple indium phosphide raw materials 85 has a shape, for example, that is cylindrical. The multiple indium phosphide raw materials 85 are stacked on a seed crystal 84. Impurity raw materials (not shown) are placed inside the crucible 40. The impurity raw materials are formed from elements that the InP substrate 100 described above contains as impurities.

[0084] As shown in Figure 14, the sealing material 86 may be arranged on a plurality of indium phosphide raw materials 85. The sealing material 86 is formed of, for example, boron oxide. The shape of the sealing material 86 is cylindrical. The sealing material 86 suppresses the dissociation of phosphorus from indium phosphide by the decomposition of indium phosphide.

[0085] Next, the process of melting the raw materials (S30) is carried out. The crucible 40 is heated by supplying power to the heating section 48. The power supplied to the upper heating member 48a is greater than the power supplied to the lower heating member 48b. Therefore, the temperature of the crucible 40 increases as you move away from the bottom of the crucible 40 along the vertically upward direction 111. As a result, a portion of the seed crystal 84 and the indium phosphide raw material 85 melt. The melted portion of the seed crystal 84 and the indium phosphide raw material 85 become the raw material melt 87. The raw material melt 87 comes into contact with the rest of the seed crystal 84. As the sealing material 86 melts, the sealing material 86 becomes a liquid sealing material 88. The liquid sealing material 88 covers the raw material melt 87. Thus, the raw material melt 87 is prepared.

[0086] Next, the crystal growth process (S40) is carried out. Figure 15 is a schematic first cross-sectional view showing the crystal growth process (S40). The cross-section shown in Figure 15 is a cross-section that includes the central axis C and is parallel to the 90° direction. As shown in Figure 15, for example, the crucible 40 is pulled down along the vertical downward direction 112. The temperature of the raw material melt 87 near the remainder of the seed crystal 84 decreases. As the raw material melt 87 in contact with the remainder of the seed crystal 84 solidifies, indium phosphide crystals 200 grow on the remainder of the seed crystal 84.

[0087] Figure 16 is a schematic diagram of a second cross-section showing the crystal growth process (S40). The cross-section shown in Figure 16 includes the central axis C and is parallel to the 0° direction. From another point of view, the cross-section shown in Figure 16 is perpendicular to the cross-section shown in Figure 15. As shown in Figures 15 and 16, the positions on the inner circumferential surface of the crucible 40 that are in the 0°, 90°, 180°, and 270° directions are designated as the first position P1, second position P2, third position P3, and fourth position P4, respectively.

[0088] As the cross-sectional area in the section parallel to the radial direction decreases, the amount of heat generated by the heating section 48 increases. Therefore, if the length of the heating section 48 in the vertically upward direction 111 does not change, as the thickness of the heating section 48 in the radial direction decreases, the amount of heat generated by the heating section 48 increases. For this reason, the amount of heat generated at the thinnest part is greater than the amount of heat generated at the thickest part.

[0089] As the thickness of the heating section 48 changes radially along the circumferential direction R, an uneven distribution of heat is created in the crucible 40 from the heating section 48. Consequently, in a cross-section perpendicular to the central axis C, the temperature of the raw material molten 87 near the thinnest part of the heating section 48 is higher than the temperature of the raw material molten 87 near the thickest part of the heating section 48.

[0090] Specifically, the temperature of the raw material melt 87 at the first position P1 is higher than the temperature of the raw material melt 87 at the second position P2 and the fourth position P4, respectively. Similarly, the temperature of the raw material melt 87 at the third position P3 is higher than the temperature of the raw material melt 87 at the second position P2 and the fourth position P4, respectively. The temperature of the raw material melt 87 at the third position P3 may be substantially the same as the temperature of the raw material melt 87 at the first position P1. The temperature of the raw material melt 87 at the second position P2 may be substantially the same as the temperature of the raw material melt 87 at the fourth position P4. The value obtained by subtracting the temperature of the raw material melt 87 at the second position P2 from the temperature of the raw material melt 87 at the first position P1 is, for example, 2.0°C.

[0091] The interface between either the indium phosphide crystal 200 or the seed crystal 84 and the raw material melt 87 is called the solid-liquid interface S. Normally, when the temperature is controlled so that the portion of the solid-liquid interface S near the central axis C is flat, the outer periphery of the solid-liquid interface S takes on a shape that rises vertically upward 111. For this reason, as shown in Figure 15, the portions of the solid-liquid interface S located at the second position P2 and the fourth position P4 are raised vertically upward 111.

[0092] On the other hand, as described above, the temperature of the raw material melt 87 at the first position P1 and the third position P3 is higher than the temperature of the raw material melt 87 at the second position P2 and the fourth position P4. For this reason, as shown in Figure 16, the portion of the solid-liquid interface S located at the first position P1 and the third position P3 is suppressed from rising vertically upward 111. From another point of view, in a cross section that includes the central axis C and is parallel to the 0° direction, the solid-liquid interface S is linear.

[0093] As the crucible 40 is continuously lowered, the growth of the indium phosphide crystal 200 continues. After the crystal growth is complete, the power supply to the heating unit 48 is reduced. Finally, the power supply to the heating unit 48 is stopped. As a result, the temperatures of the heating unit 48, the crucible 40, and the indium phosphide crystal 200 gradually decrease. In this way, the indium phosphide crystal 200 is produced. The maximum diameter of the indium phosphide crystal 200 is substantially the same as the inner diameter of the crucible 40.

[0094] Next, a crystal cutting process (S50) is performed. For example, a wire saw is used to cut the ends of the indium phosphide crystal 200 in the direction of growth. This processes the indium phosphide crystal 200 so that its shape becomes cylindrical.

[0095] Figure 17 is a schematic side view showing the structure of an InP crystal 200 according to the first embodiment. As shown in Figure 17, the InP crystal 200 has a first end face 21, a second end face 22, and a cylindrical surface 23. The InP crystal 200 is formed of InP. The second end face 22 is opposite the first end face 21. The direction from the first end face 21 to the second end face 22 is the same as the growth direction of the InP crystal 200. The thickness of the InP crystal 200 in the growth direction is, for example, greater than 1 mm.

[0096] An InP substrate 100 (see Figures 1 and 2) according to this disclosure can be manufactured by slicing the InP crystal 200 along a plane perpendicular to the growth direction of the InP crystal 200 and flattening the cut surface. In addition, the InP substrate 100 may be manufactured by cutting the InP crystal 200 with a band saw or the like in the crystal cutting step (S50). In this case, the first main surface 1 and the second main surface 2 of the InP substrate 100 may be flattened by grinding and polishing or the like.

[0097] Next, the effects and advantages of the manufacturing method for the InP substrate 100 and InP crystal 200 according to the first embodiment will be explained.

[0098] The InP substrate 100 is used in the manufacture of semiconductor devices such as photodetectors. The InP substrate 100 contains dislocations. When dislocations are present in semiconductor devices manufactured using the InP substrate 100, the dark current in the semiconductor device may increase. In this case, the device yield decreases during the manufacture of the semiconductor device.

[0099] When the diameter of the InP substrate 100 is relatively small, the region without dislocations is large, and the dislocation density in the region with dislocations is small. On the other hand, as the diameter of the InP substrate 100 increases, it becomes more difficult to reduce the dislocations contained in the InP substrate 100. Specifically, as the diameter of the InP substrate 100 increases, the region without dislocations becomes smaller, and the dislocation density in the region with dislocations increases. Therefore, as the diameter of the InP substrate 100 increases, dislocations are more likely to be included in semiconductor devices, and if dislocations are included in semiconductor devices, the number of dislocations included in the semiconductor device increases. This reduces the device yield. In particular, when the chip size of the semiconductor device is relatively large, the device yield tends to decrease. Therefore, in order to improve the device yield, the InP substrate 100 is required to have a larger continuous region without dislocations.

[0100] According to the InP substrate 100 of the first embodiment, when the dislocation density in each of the multiple second square regions 52 is measured, the dislocation density relative to the total number of the multiple second square regions 52 is 0 / cm². ２ The proportion of the number of multiple second square regions 52 is 30% or more. As a result, as described above (see Figures 6 and 7), the area of ​​the continuous dislocation-free region 31 is increased. This prevents dislocations from being included in semiconductor devices when semiconductor devices are manufactured using the InP substrate 100. As a result, device yield can be improved. In particular, device yield can be effectively improved when the chip size of the semiconductor device is relatively large (for example, 3 mm x 3 mm or larger).

[0101] When dislocations are present in a semiconductor device, an increase in dark current may occur during reliability testing. Consequently, the device's lifespan is shortened. According to the InP substrate 100 of the first embodiment, the device's lifespan can be extended by preventing the presence of dislocations in the semiconductor device.

[0102] According to the InP substrate 100 of the first embodiment, the diameter D of the first main surface 1 is 149 mm or more. In this way, even when the InP substrate 100 has a large diameter, the device yield can be improved.

[0103] According to the InP substrate 100 of the first embodiment, the ratio of the length of the continuous dislocation-free region 30 in the longitudinal direction (second length L2) to the diameter D of the first main surface 1 is 70% or more. In this way, the area of ​​the continuous dislocation-free region 31 is increased. This effectively improves the device yield.

[0104] As the carrier concentration in the InP substrate 100 decreases, the number of dislocations in the InP substrate 100 increases. According to the InP substrate 100 of the first embodiment, the carrier concentration at the center of the first main surface 1 is 5.0 × 10⁻¹⁴. １８ / cm ３ The following is true: Even when the carrier concentration is relatively low, the InP substrate 100 according to the first embodiment can improve the device yield.

[0105] According to the InP substrate 100 of the first embodiment, the carrier concentration at the first center A1 is 1.0 × 10⁻⁶. １８ / cm ３ That concludes the explanation. This prevents an excessive increase in dislocation density.

[0106] Typically, in an InP crystal manufacturing apparatus, the shape of the heating section 48 viewed in the vertically downward direction 112 is circular. In other words, the thickness of the heating section 48 in the radial direction does not change along the circumferential direction R. In this case, the temperature distribution of the raw material molten 87 is concentric in a cross section perpendicular to the central axis C. Therefore, around the entire circumference of the solid-liquid interface S, the outer periphery of the solid-liquid interface S rises vertically upward 111. From another perspective, the shape of the solid-liquid interface S is rotationally symmetric when viewed in the vertically downward direction 112. As a result, dislocations are distributed relatively uniformly across the entire surface of the first main surface 1 of the indium phosphide substrate 100.

[0107] According to the method for manufacturing the InP crystal 200 according to the first embodiment, the thickest part of the heating section 48 is located in the 0° direction. The thickness of the heating section 48 in the 180° direction is thinner than the thickness of the heating section 48 in the 90° direction and the 270° direction, respectively. The value obtained by dividing the thickness of the thickest part in the radial direction by the thickness of the thinnest part is 1.05 or more and 1.5 or less.

[0108] Therefore, the temperature of the solid-liquid interface S located in the 0° and 180° directions can be increased compared to the temperature of the solid-liquid interface S located in the 90° and 270° directions, respectively. This suppresses the upward movement of the outer periphery of the solid-liquid interface S in both the 0° and 180° directions. Consequently, the shape of the solid-liquid interface S located near the central axis C and extending along the 0° direction can be made flat. As a result, the generation of dislocations in the solid-liquid interface S can be suppressed. This increases the area of ​​the continuous dislocation-free region 31 when the InP substrate 100 is manufactured using the InP crystal 200. As a result, the device yield can be improved when the InP substrate 100 and semiconductor devices are manufactured using the InP crystal 200.

[0109] In the method for manufacturing the InP crystal 200 according to the first embodiment, the thickness of the heating portion 48 in the 0° direction is the same as the thickness of the heating portion 48 in the 180° direction. The thickness of the heating portion 48 in the 90° direction is the same as the thickness of the heating portion 48 in the 270° direction. Therefore, when viewed in the vertically downward direction 112, the shape of the solid-liquid interface S can be made closer to symmetrical with respect to a virtual straight line that intersects the central axis C and extends along the 0° direction. This makes it possible to make the shape of the portion of the solid-liquid interface S located near the central axis C and extending along the 0° direction flatter. The dislocation density on the first main surface 1 can be reduced.

[0110] In the above description, a configuration was described in which both the upper heating member 48a and the lower heating member 48b have varying thicknesses along the circumferential direction R. However, the configuration of the manufacturing apparatus 300 according to this disclosure is not limited to the above configuration. It is sufficient that the thickness of the heating section 48 changes along the circumferential direction R at least at the height where the solid-liquid interface S is located. Specifically, for example, the shape of the upper heating member 48a may be the shape of the heating section 48 described above (see Figure 11 or Figure 12), and the thickness of the lower heating member 48b does not have to change along the circumferential direction R. The thickest part of the heating section 48 is the portion of the heating section 48 at the height where the solid-liquid interface S is located and which has the thickest thickness in the radial direction.

[0111] The "height at which the solid-liquid interface S is located" refers to the height at which at least a portion of the solid-liquid interface S is located during the crystal growth process (S40). In the VGF method and the like, the position of the solid-liquid interface S relative to the heating section 48 changes during the crystal growth process. In this case, the height at which the solid-liquid interface S passes from the start to the end of the crystal growth process (S40) is defined as the "height at which the solid-liquid interface S is located".

[0112] In the above description, the heating section 48 was formed by two heating members, but the heating section 48 may be formed by three or more heating members. For example, the heating section 48 may be formed by four or fewer heating members. The heating members are arranged in a line along the vertically downward direction 112. The heating section 48 may also be formed by a single heating member. In other words, the heating section 48 may be a single component.

[0113] <Second Embodiment> Next, the configuration of the manufacturing apparatus 300 according to the second embodiment will be described. Figure 18 is a schematic plan view showing the configuration of the manufacturing apparatus 300 according to the second embodiment. As shown in Figure 18, the heating section 48 does not need to have a change in thickness in the radial direction along the circumferential direction R. The manufacturing apparatus 300 may have a main heating section 65, a first auxiliary heating section 68, and a second auxiliary heating section 69. The main heating section 65 is formed by the upper heating member 48a and the lower heating member 48b (see Figure 10) described above.

[0114] The first auxiliary heating section 68 and the second auxiliary heating section 69 are located between the crucible 40 and the main heating section 65. The first auxiliary heating section 68 is located in the 0° direction. The second auxiliary heating section 69 is located in the 180° direction. Neither the first auxiliary heating section 68 nor the second auxiliary heating section 69 are located in the 90° and 270° directions, respectively. In other words, in the 90° and 270° directions, the crucible 40 faces the main heating section 65.

[0115] According to the manufacturing apparatus 300 of the second embodiment, the same heat distribution of the raw material melt 87 as when using the manufacturing apparatus 300 of the first embodiment can be formed. Therefore, in the same way as with the manufacturing apparatus 300 of the first embodiment, the InP substrate 100 and InP crystal 200 of the first embodiment can be manufactured.

[0116] (Sample Preparation) First, InP substrates 100 corresponding to samples 1 to 10 were prepared. Samples 1 to 5 were comparative examples. Samples 6 to 10 were examples.

[0117] In samples 1 to 5, the InP substrates 100 were prepared using the manufacturing apparatus 300 according to the first embodiment described above, except that the shape of the heating section 48 was different. Specifically, the thickness of the heating section 48 did not change in the radial direction along the circumferential direction R. In samples 6 to 10, the InP substrates 100 were prepared using the manufacturing apparatus 300 according to the first embodiment described above.

[0118] In samples 1, 2, 4 through 7, 9, and 10, the diameter D of the first main surface 1 was 6 inches (152.4 mm). In samples 3 and 8, the diameter D of the first main surface 1 was 8 inches (203.2 mm).

[0119] In all samples, the carrier concentration in the first center A1 was measured using the measurement method described above. In samples 1, 3 to 6, and 8 to 10, the carrier concentration in the first center A1 was 4.5 × 10⁻⁶. １８ / cm ３ In samples 2 and 7, the carrier concentration at the first center A1 was 1.2 × 10⁻⁶. １８ / cm ３ That was the case.

[0120] In samples 1 to 3 and 6 to 8, the dopant was S. In samples 4 and 9, the dopant was Sn. In samples 5 and 10, the dopant was Zn.

[0121] Dislocation density was measured in all samples using the measurement method described above. The average dislocation density in all samples was 42.2 / cm³. ２ 45.2 / cm or more ２The following was observed: In all samples, the dislocation-free region ratio (first dislocation-free region ratio) in the first square region 51 was between 71.2% and 72.5%.

[0122] In samples 1 to 5, the dislocation-free region ratio (second dislocation-free region ratio) in the second square region 52 was between 22.3% and 23.7%. In samples 6 to 10, the second dislocation-free region ratio was between 32.0% and 33.2%.

[0123] In samples 1 to 5, the dislocation-free region ratio (third dislocation-free region ratio) in the third square region 53 was between 23.1% and 24.1%. In samples 6 to 10, the third dislocation-free region ratio was between 25.1% and 27.0%.

[0124] In samples 1 to 5, the length of the continuous dislocation-free region 30 (second length L2) was between 58 mm and 98 mm. The ratio of the second length L2 to the diameter D of the first main surface 1 was between 38.1% and 48.2%. In samples 6 to 10, the second length L2 was between 110 mm and 152 mm. The ratio of the second length L2 to the diameter D of the first main surface 1 was between 72.2% and 84.0%.

[0125] (Evaluation Method) For all samples, the device yield when fabricating semiconductor devices was calculated. Specifically, semiconductor devices (photodetectors) were manufactured using InP substrates 100. The chip size of the semiconductor devices was set to 3 mm x 3 mm. The dark current of the manufactured semiconductor devices was measured. Semiconductor devices with a dark current higher than the threshold were determined to be defective. When manufacturing semiconductor devices using one InP substrate 100, the ratio of the number of semiconductor devices determined to be defective to the total number of semiconductor devices was defined as the device yield.

[0126]

[0127]

[0128] (Evaluation Results) Tables 1 and 2 show the evaluation results for the InP substrate 100 for samples 1 to 10. As shown in Tables 1 and 2, for samples 1 to 5, where the second dislocation-free region ratio was 23.7% or less, the device yield was 82% or less. On the other hand, for samples 6 to 10, where the second dislocation-free region ratio was 32.0% or more, the device yield was 94% or more.

[0129] Based on the above, it was confirmed that the InP substrate 100 according to the example can improve device yield compared to the InP substrate 100 according to the comparative example. Furthermore, it was confirmed that the method for manufacturing the InP crystal 200 according to the present embodiment described above can improve device yield.

[0130] By comparing samples 3 and 8, it was confirmed that the InP substrate 100 according to the example can improve device yield even when the diameter D is 8 inches. Furthermore, by comparing samples 2 and 7, it was confirmed that the InP substrate 100 according to the example has a carrier concentration of 1.2 × 10⁻¹⁶. １８ / cm ３ It was confirmed that device yield can be improved even in this case. Furthermore, it was confirmed that device yield can be improved according to the InP substrate 100 of the embodiment, regardless of whether the dopant is S, Sn, or Zn.

[0131] Figure 19 is a first schematic diagram showing the distribution of dislocations on the first main surface 1 of the InP substrate 100 for sample 1. Figure 20 is a second schematic diagram showing the distribution of dislocations on the first main surface 1 of the InP substrate 100 for sample 1. Figure 21 is a first schematic diagram showing the distribution of dislocations on the first main surface 1 of the InP substrate 100 for sample 6. Figure 22 is a second schematic diagram showing the distribution of dislocations on the first main surface 1 of the InP substrate 100 for sample 6.

[0132] Figures 19 and 21 show the presence or absence of dislocations in each of the multiple first square regions 51. Specifically, the black regions indicate first square regions 51 with dislocations (dislocation regions 32). The white regions indicate first square regions 51 without dislocations (dislocation-free regions 31).

[0133] Figures 20 and 22 show the presence or absence of dislocations in each of the multiple second square regions 52. For ease of explanation, the presence or absence of dislocations in the second square regions 52 is shown using a 1 mm x 1 mm square centered on the second center A2. Specifically, the black areas indicate second square regions 52 where dislocations were present. The white areas indicate second square regions 52 where dislocations were not present.

[0134] As shown in Figures 19 and 20, it can be confirmed that in sample 1, dislocations are distributed relatively uniformly within the plane. On the other hand, as shown in Figures 21 and 22, it can be confirmed that in sample 6, the region without dislocations is concentrated in the center of the substrate. Specifically, in sample 6, it can be confirmed that the region without dislocations in the central part of the substrate extends along the vertical direction. The vertical direction in Figures 21 and 22 was the <0-11> direction.

[0135] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and all modifications within the scope of the claims are intended to be included in the meaning of equivalents and within the scope.

[0136] 1 First main surface, 2 Second main surface, 3 Outer peripheral surface, 6 Measurement area, 8 Outer peripheral area, 18 Outer peripheral area, 19 Central area, 21 First end face, 22 Second end face, 23 Cylindrical surface, 30 Continuous non-rotational area, 31 Non-rotational area, 32 Rotational area, 40 Crucible, 41 Crystallization holding section, 42 Crystallization growth section, 42a Diameter increase section, 42b Straight section, 48 Heating section, 48a Upper heating component, 48b Lower heating component, 49 Crucible holding stage, 51 First square area, 52 Second square area, 53 Third square area, 61 Thinnest part, 61a First thinnest part, 61b Second thinnest part, 62 Thickest part, 62a First thickest part, 62b 65. Thickest part 2, 66. Main heating part, 67. Part 2, 68. First auxiliary heating part, 69. Second auxiliary heating part, 70. Rectangular slice, 78. Electrode for measurement, 84. Crystallization, 85. Lined ethylene raw material, 86. Sealing material, 87. Raw material melt, 88. Liquid sealing material, 100. Lined ethylene substrate (InP substrate), 101. First direction, 102. Second direction, 110. Growth direction, 111. Vertical upward direction, 112. Vertical downward direction, 200. Lined ethylene crystal (InP crystal), 300. Manufacturing apparatus, A1. First center, A2. Second center, A3. Third center, C. Central axis, D. Diameter, E1. First distance, E2. Second distance, P1. First position, P2. Position 2, P3 Position 3, P4 Position 4, R Circumferential direction, S Solid-liquid interface, X Square.

Claims

1. It has a main surface, the diameter of which is 149 mm or more and 205 mm or less, and the average dislocation density on which is 0 / cm². ２ More than 50 / cm ２ The following is the case: The main surface is formed by an outer peripheral region within 5 mm from the outer edge and a central region surrounded by the outer peripheral region; the central region is divided by first square regions with a side length of 1 mm and arranged in a grid pattern; when a square with a side length of 3 mm that surrounds nine of the first square regions is moved 1 mm at a time along a first direction in which the first side of the first square region extends and a second direction in which the second side connected to the first side extends, the region specified by the square is determined to be a plurality of second square regions; when the dislocation density in each of the plurality of second square regions is measured, the dislocation density relative to the total number of the plurality of second square regions is 0 / cm². ２ An indium phosphide substrate in which the proportion of the number of the plurality of second square regions is 30% or more.

2. Measure the dislocation density in the first square region, and if the dislocation density is 0 / cm² ２ The indium phosphide substrate according to claim 1, wherein the first square region is defined as a dislocation-free region, and among the regions formed by the dislocation-free regions that are continuous along either the first or second direction, the region with the largest area is defined as a continuous dislocation-free region, and the ratio of the length of the continuous dislocation-free region in the longitudinal direction to the diameter of the main surface is 70% or more and 90% or less.

3. The carrier concentration at the center of the main surface is 5.0 × 10⁻⁶ １８ / cm ３ The indium phosphide substrate according to claim 1 or claim 2, which is as follows:

4. The carrier concentration at the center of the main surface is 1.0 × 10⁻⁶ １８ / cm ３ The indium phosphide substrate according to any one of claims 1 to 3.

5. A method for producing indium phosphide crystals using a vertical boat method, comprising: a step of arranging a seed crystal and raw materials inside a crucible surrounded by a heating section; a step of preparing a raw material melt by melting a part of the seed crystal and the raw materials using the heating section; and a step of growing an indium phosphide crystal on the remainder of the seed crystal by solidifying the raw material melt, wherein, when the directions perpendicular to the central axis of the crucible and viewed from the central axis are designated as the 0° direction, 90° direction, 180° direction, and 270° direction, respectively, at least at the height where the solid-liquid interface is located, the thinnest part of the heating section in the radial direction of the crucible is located in the 0° direction, and the thickness of the heating section in the 180° direction is thinner than the thickness of the heating section in the 90° direction and the 270° direction, respectively. A method for producing indium phosphide crystals, wherein the value obtained by dividing the thickness of the thickest portion of the heating part in the radial direction by the thickness of the thinnest portion of the heating part in the radial direction is 1.05 or more and 1.5 or less.

6. The method for producing indium phosphide crystals according to claim 5, wherein, at least at the height where the solid-liquid interface is located, the thickness of the heating portion in the 0° direction is the same as the thickness of the heating portion in the 180° direction, and the thickness of the heating portion in the 90° direction is the same as the thickness of the heating portion in the 270° direction.

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