Method for producing indium phosphide substrate and indium phosphide crystal

Abstract

The indium phosphide substrate has a main surface. The diameter of the main surface is 149 mm or more and 205 mm or less. The main surface is formed by an outer peripheral region and a central region. The central region is divided into first square regions, each having a side length of 1 mm and arranged in a grid pattern. When a square having a side length of 3 mm and surrounding nine first square regions is moved by 1 mm in each of the first direction and the second direction, the regions specified by the squares are defined as a plurality of second square regions. The dislocation density relative to the total number of the plurality of second square regions is 0 / cm. 2 The proportion of the number of the second square regions in which the above expression is satisfied is 30% or more.

Description

[Technical Field]

[0001] The present disclosure relates to methods for manufacturing indium phosphide substrates and indium phosphide crystals. [Background technology]

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

[0003] [Patent Document 1] Special Publication No. 2023-516634 Summary of the Invention

[0004] The indium phosphide substrate according to the present disclosure has a primary surface. The diameter of the primary surface is 149 mm or more and 205 mm or less. The average dislocation density on the primary surface is 0 / cm 2 More than 50 / cm 2 The principal surface is formed by a peripheral region within 5 mm from the outer periphery and a central region surrounded by the peripheral region. The central region is divided into first square regions, each 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 first square regions is moved by 1 mm 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 regions specified by the squares are the second square regions. When the dislocation density in each of the second square regions is measured, the dislocation density relative to the total number of the second square regions is 0 / cm. 2 The proportion of the number of the second square regions in which the above expression is satisfied is 30% or more. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 is a plan view schematically illustrating the configuration of an indium phosphide substrate according to the first embodiment. [Figure 2] FIG. 2 is a side view schematically illustrating the configuration of the indium phosphide substrate according to the first embodiment. [Figure 3] FIG. 3 is a schematic plan view illustrating the first square region. [Figure 4] FIG. 4 is a schematic plan view illustrating the second square region. [Figure 5] FIG. 5 is a schematic plan view illustrating the third square region. [Figure 6] FIG. 6 is a schematic diagram illustrating the dislocation-free region rate when dislocations are distributed relatively uniformly on the first main surface. [Figure 7] FIG. 7 is a schematic diagram illustrating the dislocation-free region rate when dislocations are distributed in a relatively concentrated manner on the first main surface. [Figure 8] FIG. 8 is a schematic plan view showing the measurement positions of the carrier concentration. [Figure 9] FIG. 9 is a schematic diagram showing the configuration of the measurement sample. [Figure 10] FIG. 10 is a cross-sectional view schematically illustrating the configuration of an indium phosphide crystal manufacturing apparatus according to the first embodiment. [Figure 11] FIG. 11 is a schematic plan view showing the configuration of the manufacturing apparatus as viewed vertically downward. [Figure 12] FIG. 12 is a schematic plan view showing the configuration of a modified example of the manufacturing apparatus according to the first embodiment. [Figure 13] FIG. 13 is a flow diagram that schematically shows a method for producing indium phosphide crystal according to the first embodiment. [Figure 14] FIG. 14 is a schematic cross-sectional view showing a crucible in which a seed crystal, an indium phosphide raw material, and a sealing material are placed. [Figure 15] FIG. 15 is a first cross-sectional view showing a step of growing a crystal. [Figure 16] FIG. 16 is a second schematic cross-sectional view showing the step of growing a crystal. [Figure 17] FIG. 17 is a side view schematic diagram showing the configuration of indium phosphide crystal according to the first embodiment. [Figure 18] FIG. 18 is a schematic plan view showing the configuration of a manufacturing apparatus according to the second embodiment. [Figure 19] FIG. 19 is a first schematic diagram showing the distribution of dislocations on the first main surface of the indium phosphide substrate according to Sample 1. As shown in FIG. [Figure 20] FIG. 20 is a second schematic diagram showing the distribution of dislocations on the first main surface of the indium phosphide substrate according to Sample 1. As shown in FIG. [Figure 21] FIG. 21 is a first schematic diagram showing the distribution of dislocations on the first main surface of the indium phosphide substrate according to Sample 6. As shown in FIG. [Figure 22] FIG. 22 is a second schematic diagram showing the distribution of dislocations on the first main surface of the indium phosphide substrate according to Sample 6. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0006] [Problem to be solved by this disclosure] When semiconductor devices are manufactured using indium phosphide having a diameter of 6 inches or more, the dark current of the manufactured semiconductor devices increases, which reduces the device yield.

[0007] An object of the present disclosure is to provide a method for manufacturing an indium phosphide substrate and an indium phosphide crystal that can improve device yield.

[0008] [Effects of this disclosure] According to the present disclosure, it is possible to provide a method for manufacturing an indium phosphide substrate and an indium phosphide crystal that can improve device yield.

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

[0010] (1) An indium phosphide substrate according to the present disclosure has a primary surface. The primary surface has a diameter of 149 mm or more and 205 mm or less. The average dislocation density on the primary surface is 0 / cm 2 More than 50 / cm2 The principal surface is formed by a peripheral region within 5 mm from the outer periphery and a central region surrounded by the peripheral region. The central region is divided into first square regions, each 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 first square regions is moved by 1 mm 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 regions specified by the squares are the second square regions. When the dislocation density in each of the second square regions is measured, the dislocation density relative to the total number of the second square regions is 0 / cm. 2 The proportion of the number of the second square regions that satisfy the condition is 30% or more, which can improve the device yield.

[0011] (2) In the indium phosphide substrate according to (1) above, the dislocation density in the first square region is measured, and the dislocation density is 0 / cm 2 The first square region may be defined as a dislocation-free region. Of the regions formed by continuous dislocation-free regions along either the first direction or the 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), the carrier concentration at the center of the main surface is 5.0×10 18 / cm 3 In this way, 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), the carrier concentration at the center of the main surface is 1.0×10 18 / cm 3 This can prevent the dislocation density from increasing excessively.

[0014] (5) The method for producing indium phosphide crystal according to the present disclosure uses a vertical boat method. The method for producing indium phosphide crystal includes the following steps: a seed crystal and a raw material are placed inside a crucible surrounded by a heating unit; a raw material melt is prepared by melting a portion of the seed crystal and the raw material using the heating unit; an indium phosphide crystal grows on the remainder of the seed crystal by solidifying the raw material melt; directions perpendicular to the central axis of the crucible and at 0°, 90°, 180°, and 270° from the central axis are defined as the 0° direction, 90° direction, 180° direction, and 270° direction, respectively; at least at a height where the solid-liquid interface is located, the thinnest portion of the heating unit in the radial direction of the crucible is located in the 0° direction; at least at a height where the solid-liquid interface is located, the thickness of the heating unit in the 180° direction is thinner than the thickness of the heating unit in each of the 90° direction and the 270° direction. At least at the height where the solid-liquid interface is located, the value obtained by dividing the thickness of the portion of the heating part that is thickest in the radial direction by the thickness of the portion of the heating part that is thinnest in the radial direction is 1.05 or more and 1.5 or less, which enables an improvement in device yield when semiconductor devices are manufactured using indium phosphide crystals.

[0015] (6) According to the indium phosphide crystal manufacturing method pertaining to (5) above, 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, at least at the height where the solid-liquid interface is located. This makes it possible to effectively improve device yield when semiconductor devices are manufactured using indium phosphide crystal.

[0016] [Details of the embodiment] Hereinafter, details of embodiments of the present disclosure will be described with reference to the drawings. Note that the same or corresponding parts in the following drawings are given the same reference numerals, and their description will not be repeated. In the crystallographic description in this specification, a group orientation is indicated by <> and a group plane is indicated by {}. Furthermore, for negative indices, a "-" (bar) is placed above the number in crystallography, but in this specification, a negative sign is placed 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 will also be referred to as an InP substrate 100. Fig. 1 is a plan view schematic diagram showing the configuration of the InP substrate 100 according to the first embodiment. Fig. 2 is a side view schematic diagram showing the configuration of the InP substrate 100 according to the first embodiment.

[0018] 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 made of indium phosphide (InP). The InP substrate 100 has a cubic crystal structure.

[0019] 2, the second main surface 2 is opposite 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 the ridge line between the first main surface 1 and the outer peripheral surface 3.

[0020] The direction from the first main surface 1 toward the second main surface 2 is parallel to the growth direction of indium phosphide crystals during the manufacture of the InP substrate 100. The thickness of the InP substrate 100 in the direction from the first main surface 1 toward the second main surface 2 is, for example, less than 1 mm.

[0021] 1 shows the configuration of an InP substrate 100 viewed perpendicularly to a first main surface 1. As shown in FIG. 1, the shape of the first main surface 1 when viewed perpendicularly to the first main surface 1 is, for example, circular. The first main surface 1 has a first center A1. The first center A1 is, for example, the center of the outer periphery 8.

[0022] The first main surface 1 is, for example, a {100} plane. The first main surface 1 may be inclined with respect to the {100} plane. When the first main surface 1 is inclined with respect to the {100} plane, the inclination angle (off angle) of the first main surface 1 with respect to the {100} plane is, for example, not less than 0° and not more than 15°.

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

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

[0025] (dislocation density) Dislocations exist in the InP substrate 100 according to the first embodiment. In this specification, "dislocations" refers to one type of crystal defect, and in this technical field, dislocations correspond to etch pits confirmed using the measurement method described below. Therefore, the number of dislocations can be indirectly measured by measuring the number of etch pits. In this specification, the number of dislocations is defined as 1 cm 2 The dislocation density is measured by measuring the number of etch pits per 1000 μm. The measurement area where the dislocation density is measured will be described in detail below.

[0026] <First square area> FIG. 3 is a plan view schematic diagram illustrating the first square region 51. As shown in FIG. 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 continuous with the outer peripheral edge 8. The outer peripheral region 18 is a region within 5 mm from the outer peripheral edge 8. From another perspective, 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 continuous with the outer peripheral region 18.

[0027] As shown in FIG. 3, in measuring the 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 lattice pattern. Specifically, the plurality of first square regions 51 are arranged in a lattice pattern 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, <011> It is a direction.

[0028] The first square regions 51 may be arranged in the central region 19 so as to maximize the number of the first square regions 51. Note that a square region (not shown) that intersects with the boundary between the peripheral region 18 and the central region 19 is not considered to be a first square region 51.

[0029] When viewed perpendicularly to the first main surface 1, each of the multiple first square regions 51 has a square shape. The length of one side of each of the multiple first square regions 51 (first length L1) is 1 mm. The first side of each of the multiple first square regions 51 extends along a first direction 101. The second side of each of the multiple first square regions 51 extends along a second direction 102. The second side is continuous with the first side.

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

[0031] Of 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 that are continuous mean that one side of each of the adjacent dislocation-free regions 31 is in contact with each other. In FIG. 3 , the outer edge of the continuous dislocation-free region 30 is indicated by a thick line. The continuous dislocation-free region 30 is formed by multiple dislocation-free regions 31. When 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 its longitudinal direction is designated as a 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] In the continuous dislocation-free region 30, a plurality of 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 area> 4 is a schematic plan view illustrating the second square region 52. As shown in FIG. 4, a plurality of second square regions 52 are identified in the central region 19. Specifically, when the square X is moved by 1 mm in each of the first direction 101 and the second direction 102, the regions identified by the square X become the plurality of second square regions 52.

[0035] In Fig. 4, squares X are indicated by thick lines. For ease of explanation, three overlapping squares X are shown in Fig. 4, and one of the second square areas 52 identified by the squares X is hatched.

[0036] The square X surrounds nine first square regions 51. The length of one side of the square X (third length L3) is 3 mm. The plurality of second square regions 52 are identified so that the number of the plurality of second square regions 52 is maximized.

[0037] Each of the second square regions 52 includes nine first square regions 51. The centers (second centers A2) of the second square regions 52 are arranged in a grid pattern at intervals of 1 mm 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 the second square regions 52.

[0038] When viewed perpendicularly to the first main surface 1, each of the multiple second square regions 52 has a square 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 second square regions 52 whose second centers A2 are adjacent to each other partially overlap. The area of ​​the overlapping portion of the two second square regions 52 whose second centers A2 are adjacent to each other is 2 / 3 of the area of ​​one second square region 52.

[0039] <3rd square area> FIG. 5 is a schematic plan view illustrating the third square region 53. As shown in FIG. 5, a plurality of third square regions 53 are identified in the central region 19. Each of the plurality of third square regions 53 includes nine first square regions 51. When viewed perpendicularly to the first main surface 1, each of the plurality of third square regions 53 has a square shape. The length of one side of each of the plurality of third square regions 53 (fourth length L4) is 3 mm.

[0040] The centers (third centers A3) of the plurality of third square regions 53 are arranged in a grid pattern at intervals of 3 mm 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 plurality of third square regions 53 do not overlap one another. One side of each of two adjacent third square regions 53 among the plurality of third square regions 53 is in contact with one another.

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

[0042] Next, the number of etch pits in each of the plurality of first square regions 51 is measured using an optical microscope. The observation magnification of the optical microscope in this measurement is, for example, 25 times or more and 100 times or less. The value obtained by dividing the measured number of etch pits by the area of ​​the first square region 51 is taken as the dislocation density in the first square region 51. If the dislocation density is 0 / cm 2 The first square region 51 where the dislocation density is 0 / cm is identified as the dislocation-free region 31. 2 The larger first square region 51 is identified as the dislocation region 32 .

[0043] The sum of the dislocation densities in the nine first square regions 51 included in the second square region 52 divided by 9 is the dislocation density in the second square region 52. Similarly, the sum of the dislocation densities in the nine first square regions 51 included in the third square region 53 divided by 9 is the dislocation density in the third square region 53.

[0044] The sum of the dislocation densities in each of the plurality of first square regions 51 divided by the number of the plurality of first square regions 51 is defined as the average dislocation density on the first main surface 1. The average dislocation density on the first main surface 1 is 0 / cm 2 More than 50 / cm 2 The average dislocation density on the first main surface 1 is, for example, 10 / cm 2 May be more than 20 / cm 2 The average dislocation density on the first main surface 1 may be, for example, 48 / cm 2 May be less than 46 / cm 2 It may be the following:

[0045] The dislocation density relative to the total number of the first square regions 51 is 0 / cm 2 The ratio of the number of the plurality of first square regions 51 where the number satisfies the formula (1) is defined as a first dislocation-free region ratio. The first dislocation-free region ratio is, for example, not less than 70% and not more than 80%.

[0046] The dislocation density relative to the total number of the second square regions 52 is 0 / cm 2 The ratio of the number of the plurality of second square regions 52 that satisfy the condition (above) is defined as 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 the third square regions 53 is 0 / cm 2 The ratio of the number of the plurality of third square regions 53 where the number of dislocation-free regions is 0.01 to 0.01 is defined as a third dislocation-free region ratio. The third dislocation-free region ratio is lower than the second dislocation-free region ratio. The third dislocation-free region ratio is, for example, equal to or greater than 20% and less than 30%.

[0048] FIG. 6 is a schematic diagram illustrating the dislocation-free region ratio when dislocations are distributed relatively uniformly on the first main surface 1. FIG. 7 is a schematic diagram illustrating the dislocation-free region ratio when dislocations are distributed relatively concentratedly on the first main surface 1. As an example, FIGS. 6 and 7 show the dislocation-free region ratio when 14 dislocation regions 32 are included in a 12×12 first square region 51. In FIGS. 6 and 7, hatched regions indicate regions where dislocations exist. For ease of explanation, in FIGS. 6 and 7, the second square region 52 is shown as a 1 mm×1 mm square centered on the second center A2.

[0049] 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 Fig. 6 and the example shown in Fig. 7. On the other hand, the second dislocation-free region ratio in the example shown in Fig. 7 is higher than the second dislocation-free region ratio in the example shown in Fig. 6. Therefore, it can be understood that the second dislocation-free region ratio represents the size of the region where dislocation-free regions 31 are continuous in the InP substrate 100.

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

[0051] The carrier concentration at the center (first center A1) of the first main surface 1 is, for example, 1.0×10 18 / cm 3 The carrier concentration in the first center A1 is, for example, 1.5×10 18 / cm 3 It may be more than 2.0 x 10 18 / cm 3 The carrier concentration in the first center A1 may be, for example, 5.0×10 18 / cm 3The carrier concentration in the first center A1 is, for example, 4.5×10 18 / cm 3 It may be less than 4.0 x 10 18 / cm 3 It may be the following:

[0052] <Method for measuring carrier concentration> Next, a method for measuring the carrier concentration at the first center A1 will be described. FIG. 8 is a schematic plan view showing the measurement position of the carrier concentration. As shown in FIG. 8, a measurement region 6 is specified on the first main surface 1. The measurement region 6 is centered on the first center A1. When viewed perpendicularly to the first main surface 1, the measurement region 6 is square. The length of one side of the measurement region 6 (fifth length L5) is 4 mm.

[0053] In the measurement region 6, the carrier concentration is measured using Hall measurement applying the Van der Pauw method. First, the InP substrate 100 is divided along the outer edge of the measurement region 6 to prepare rectangular slices 70. Specifically, the InP substrate 100 is cleaved and cut with a dicing saw or the like to prepare the rectangular slices 70. The size of the rectangular slices 70 is, for example, 4 mm long x 4 mm wide x 600 μm thick.

[0054] FIG. 9 is a schematic diagram showing the configuration of a measurement sample 77. As shown in FIG. 9, measurement electrodes 78 are formed at the four corners of a rectangular piece 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 manner, the measurement sample 77 is produced using the rectangular piece 70. The shape of the measurement electrodes 78 may be fan-shaped or circular.

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

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

[0057] The crucible 40 is made of a material that can withstand the heat generated when melting the raw materials. Specifically, the crucible 40 is made of, for example, pyrolytic boron nitride (pBN). The crucible 40 has a seed crystal holding portion 41 and a crystal growth portion 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 described below. The direction opposite to the vertically upward direction 111 is a 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 portion 42 is the radial direction of the crucible 40.

[0059] The seed crystal holding portion 41 has a cylindrical shape with a bottom. The seed crystal holding portion 41 holds a seed crystal. The seed crystal holding portion 41 opens in a vertically upward direction 111. The crystal growth portion 42 holds a raw material. The crystal growth portion 42 is connected to the seed crystal holding portion 41. The crystal growth portion 42 is provided in the vertically upward direction 111 relative to the seed crystal holding portion 41. The crystal growth portion 42 has an increased diameter portion 42a and a straight body portion 42b.

[0060] The increased diameter portion 42a is continuous with the seed crystal holding portion 41. The increased diameter portion 42a has an annular shape. The increased diameter portion 42a surrounds the central axis C. As the increased diameter portion 42a moves away from the seed crystal holding portion 41 in the vertically upward direction 111, the inner diameter and the outer diameter of the increased diameter portion 42a each increase.

[0061] The body portion 42b is continuous with the increased diameter portion 42a. The body portion 42b is provided in the vertically upward direction 111 relative to the increased diameter portion 42a. The body portion 42b has a hollow cylindrical shape. When viewed in the vertically downward direction 112, the body portion 42b has a circular shape. The body portion 42b surrounds the central axis C. The inner diameter of the body portion 42b is, for example, 100 mm or more. The inner diameter of the body portion 42b is the same as 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 by supplying power to the heating unit 48. The heating unit 48 is, for example, a resistance heater. From another perspective, the crucible 40 is heated by, for example, a resistance heating method. The heating unit 48 may be a coil. From another perspective, the crucible 40 may be heated by a high-frequency induction heating method.

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

[0064] The heating section 48 has, 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 upper heating member 48a has a ring-shaped configuration. The lower heating member 48b is provided vertically downward in the direction 112 relative to the upper heating member 48a. The lower heating member 48b surrounds the seed crystal holder 41. When viewed in the vertically downward direction 112, the lower heating member 48b has a ring-shaped configuration.

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

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

[0067] The portion of the heating unit 48 that is thinnest in the radial direction is referred to as the thinnest portion. When viewed in the vertically downward direction 112, the direction from the central axis C toward the thinnest portion is defined as 0°. As shown in FIG. 11, the heating unit 48 may have two thinnest portions (a first thinnest portion 61a and a second thinnest portion 61b). In this case, the direction from the central axis C toward any one of the two thinnest portions is defined as the 0° direction.

[0068] The directions that are perpendicular to the central axis C and that are 0°, 90°, 180°, and 270° as viewed from the central axis C are defined as the 0° direction, 90° direction, 180° direction, and 270° direction, respectively. As shown in Fig. 11 , as viewed in a vertically downward direction 112, the 90° direction is a direction inclined by 90° in the circumferential direction R with respect to the 0° direction.

[0069] The first thinnest portion 61a is located in the 0° direction. The thickness of the heating portion 48 in the 0° direction may be the same as the thickness of the heating portion 48 in the 180° direction, for example. In other words, the second thinnest portion 61b is located in the 180° direction. From another perspective, the thickness of the heating portion 48 in the 180° direction is thinner than the thickness of the heating portion 48 in each of the 90° and 270° directions. 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 that is thickest in the radial direction is referred to as the thickest portion. The heating section 48 may have two thickest portions (a first thickest portion 62a and a second thickest portion 62b). The first thickest portion 62a is located in the 90° direction. The second thickest portion 62b is located in the 270° direction. From another perspective, 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 portion 62a and the second thickest portion 62b.

[0071] The value obtained by dividing the thickness of the thickest portion 62 (second thickness T2) by the thickness of the thinnest portion 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 in the vertically downward direction 112, the outer peripheral surface of the heating unit 48 is, for example, circular. When viewed in the vertically downward direction 112, the inner peripheral surface of the heating unit 48 is, for example, elliptical with its major axis extending along the 0° direction. The thickness of the heating unit 48, for example, in the radial direction, increases as it moves from the 0° direction to the 90° direction along the circumferential direction R. The thickness of the heating unit 48, for example, in the radial direction, decreases as it moves from the 90° direction to the 180° direction along the circumferential direction R.

[0073] For example, the thickness of the heated portion 48 in the radial direction increases as one moves from the 180° direction to the 270° direction along the circumferential direction R. For example, the thickness of the heated portion 48 in the radial direction decreases as one moves from the 270° direction to the 0° direction along the circumferential direction R.

[0074] When viewed in the vertically downward direction 112, the shape of the heating unit 48 may be two-fold symmetric about the central axis C. From another perspective, when viewed in the vertically downward direction 112, the outer shape of the heating unit 48 may overlap with the outer shape of the heating unit 48 rotated 180° about the central axis C.

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

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

[0077] (Method of manufacturing indium phosphide crystals) Next, a method for manufacturing an indium phosphide crystal 200 according to the first embodiment will be described. The InP substrate 100 is manufactured using a vertical boat method. In this specification, the vertical boat method includes a vertical Bridgman (VB) method, a vertical gradient freeze (VGF) method, and a hybrid method that combines the VB method and the VGF method. Below, a method for manufacturing an indium phosphide crystal 200 using the VB method will be described as an example.

[0078] Fig. 13 is a flow diagram that schematically shows a method for manufacturing indium phosphide crystal 200 according to the first embodiment. As shown in Fig. 13, the method for manufacturing indium phosphide crystal 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 the crystal (S40), and cutting the crystal (S50).

[0079] First, a step (S10) of preparing a manufacturing apparatus is performed. Specifically, the manufacturing apparatus 300 (see FIGS. 10 and 11) according to the first embodiment described above is prepared. In the step (S10) of preparing a manufacturing apparatus, a boron oxide (BO) film (not shown) may be formed on the surface of the crucible 40 by heating the crucible 40 in an oxygen atmosphere. The boron oxide film functions as a sealant.

[0080] Next, a step (S20) of placing the raw materials is performed. Fig. 14 is a cross-sectional view showing crucible 40 in which seed crystal 84, indium phosphide raw material 85, and sealing material 86 are placed.

[0081] 14, a seed crystal 84 is placed inside the seed crystal holder 41. The seed crystal 84 is made of InP. When viewed in the vertically downward direction 112, the seed crystal 84 is placed so that the <0-11> direction of the seed crystal 84 is parallel to the 0° direction of the manufacturing apparatus 300 (see FIG. 11).

[0082] The seed crystal 84 may contain elements contained as impurities in the above-described InP substrate 100. A plurality of indium phosphide raw materials 85 are placed on the seed crystal 84. Each of the plurality of indium phosphide raw materials 85 is formed of polycrystalline indium phosphide.

[0083] Each of the plurality of indium phosphide raw materials 85 has, for example, a cylindrical shape. The plurality of indium phosphide raw materials 85 are stacked on the seed crystal 84. An impurity raw material (not shown) is placed inside the crucible 40. The impurity raw material is made of elements contained as impurities in the above-mentioned InP substrate 100.

[0084] 14, a sealing material 86 may be disposed on the plurality of indium phosphide raw materials 85. The sealing material 86 is formed of, for example, boron oxide. The sealing material 86 has a cylindrical shape. The sealing material 86 prevents phosphorus from being dissociated from indium phosphide due to decomposition of the indium phosphide.

[0085] Next, the step (S30) of melting the raw material is performed. Crucible 40 is heated by supplying power to heating unit 48. The power supplied to upper heating member 48a is greater than the power supplied to lower heating member 48b. Therefore, the temperature of crucible 40 increases with increasing distance from the bottom of crucible 40 in vertically upward direction 111. This melts a portion of seed crystal 84 and indium phosphide raw material 85. The melted portion of seed crystal 84 and indium phosphide raw material 85 become raw material melt 87. Raw material melt 87 comes into contact with the remainder of seed crystal 84. As sealing material 86 melts, sealing material 86 becomes liquid sealing material 88. Liquid sealing material 88 covers raw material melt 87. In this manner, raw material melt 87 is prepared.

[0086] Next, the step of growing a crystal (S40) is carried out. Fig. 15 is a first cross-sectional schematic diagram showing the step of growing a crystal (S40). The cross section shown in Fig. 15 is a cross section that includes the central axis C and is parallel to the 90° direction. As shown in Fig. 15, for example, the crucible 40 is pulled down vertically in a downward direction 112. The temperature of the portion of the raw material melt 87 close to the remainder of the seed crystal 84 drops. The raw material melt 87 in contact with the remainder of the seed crystal 84 solidifies, causing an indium phosphide crystal 200 to grow on the remainder of the seed crystal 84.

[0087] Fig. 16 is a second cross-sectional schematic view showing the step (S40) of growing a crystal. The cross section shown in Fig. 16 is a cross section that includes central axis C and is parallel to the 0° direction. From another perspective, the cross section shown in Fig. 16 is perpendicular to the cross section shown in Fig. 15. As shown in Figs. 15 and 16, positions on the inner peripheral surface of crucible 40 that are in the 0° direction, 90° direction, 180° direction, and 270° direction are defined as first position P1, second position P2, third position P3, and fourth position P4, respectively.

[0088] The smaller the cross-sectional area in a cross section parallel to the radial direction, the greater the heat generation amount of the heating portion 48. Therefore, if the length of the heating portion 48 in the vertically upward direction 111 does not change, the thinner the thickness of the heating portion 48 in the radial direction, the greater the heat generation amount of the heating portion 48. Therefore, the heat generation amount at the thinnest portion is greater than the heat generation amount at the thickest portion.

[0089] The thickness of the heating part 48 varies in the radial direction along the circumferential direction R, which causes a bias in the amount of heat that the crucible 40 receives from the heating part 48. As a result, in a cross section perpendicular to the central axis C, the temperature of the part of the raw material melt 87 near the thinnest part of the heating part 48 is higher than the temperature of the part of the raw material melt 87 near the thickest part of the heating part 48.

[0090] Specifically, the temperature of the raw material melt 87 at the first position P1 is higher than the temperatures of the raw material melt 87 located at each of the second position P2 and the fourth position P4. Similarly, the temperature of the raw material melt 87 at the third position P3 is higher than the temperatures of the raw material melt 87 located at each of the second position P2 and the fourth position P4. 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 referred to as 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 has a shape that rises in the vertically upward direction 111. Therefore, as shown in FIG. 15 , the portions of the solid-liquid interface S located at the second position P2 and the fourth position P4 rise in the vertically upward direction 111.

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

[0093] As the crucible 40 continues to be lowered, the growth of the indium phosphide crystal 200 continues. After the crystal growth is completed, the power supply to the heating unit 48 is reduced. Finally, the power supply to the heating unit 48 is stopped. This causes the temperatures of the heating unit 48, the crucible 40, and the indium phosphide crystal 200 to 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 step (S50) of cutting the crystal is carried out. For example, a wire saw is used to cut the end of the indium phosphide crystal 200 in the growth direction. This processes the indium phosphide crystal 200 so that the shape of the indium phosphide crystal 200 becomes cylindrical.

[0095] 17 is a schematic side view showing the configuration of an InP crystal 200 according to the first embodiment. As shown in FIG. 17, the InP crystal 200 has a first end facet 21, a second end facet 22, and a cylindrical surface 23. The InP crystal 200 is formed of InP. The second end facet 22 is located opposite the first end facet 21. The direction from the first end facet 21 to the second end facet 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] The InP substrate 100 (see FIGS. 1 and 2) according to the present 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. Note that in the step (S50) of cutting the crystal, the InP substrate 100 may also be manufactured by cutting the InP crystal 200 with a band saw or the like. In this case, the first main surface 1 and the second main surface 2 of the InP substrate 100 may each be flattened by grinding, polishing, or the like.

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

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

[0099] When the diameter of the InP substrate 100 is relatively small, the dislocation-free region is large and the dislocation density in the dislocation-containing region is low. 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 dislocation-free region becomes smaller and the dislocation density in the dislocation-containing region increases. Therefore, as the diameter of the InP substrate 100 increases, semiconductor devices are more likely to contain dislocations, and if a semiconductor device contains dislocations, the number of dislocations contained in the semiconductor device increases. This reduces device yield. This is particularly true when the chip size of a semiconductor device is relatively large. Therefore, to improve device yield, the InP substrate 100 is required to have larger, continuous dislocation-free regions.

[0100] In the InP substrate 100 according to the first embodiment, when the dislocation density in each of the second square regions 52 is measured, the dislocation density relative to the total number of the second square regions 52 is 0 / cm 2 The proportion of the number of the plurality of second square regions 52 that are in this state is 30% or more. Therefore, as described above (see FIGS. 6 and 7), the area of ​​the continuous dislocation-free regions 31 is increased. This makes it possible to prevent dislocations from being included in semiconductor devices manufactured using the InP substrate 100. As a result, the device yield can be improved. In particular, when the chip size of the semiconductor devices is relatively large (for example, 3 mm × 3 mm or more), the device yield can be effectively improved.

[0101] If a semiconductor device contains dislocations, an increase in dark current may occur during reliability testing, thereby shortening the device's lifespan. The InP substrate 100 according to the first embodiment can prevent dislocations from being contained in the semiconductor device, thereby extending the device's lifespan.

[0102] According to the InP substrate 100 in accordance with 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] In the InP substrate 100 according to the first embodiment, the ratio of the length (second length L2) of the continuous dislocation-free region 30 in the longitudinal direction of the continuous dislocation-free region 30 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, which can effectively improve the device yield.

[0104] As the carrier concentration in the InP substrate 100 decreases, the number of dislocations in the InP substrate 100 increases. In the InP substrate 100 according to the first embodiment, the carrier concentration at the center of the first main surface 1 is 5.0×10 18 / cm 3 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 18 / cm 3 This makes it possible to prevent the dislocation density from increasing excessively.

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

[0107] According to the manufacturing method of InP crystal 200 according to the first embodiment, the thickest part of heating portion 48 is located in the 0° direction. The thickness of heating portion 48 in the 180° direction is thinner than the thickness of heating portion 48 in each of the 90° and 270° directions. 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 temperatures of the portions of the solid-liquid interface S located in the 0° and 180° directions can be made higher than the temperatures of the portions of the solid-liquid interface S located in the 90° and 270° directions. This prevents the outer periphery of the solid-liquid interface S from rising in the 0° and 180° directions. Therefore, the shape of the portion of the solid-liquid interface S located near the central axis C and extending along the 0° direction can be flattened. This prevents dislocations from occurring in the portion of the solid-liquid interface S. When an InP substrate 100 is manufactured using the InP crystal 200, the area of ​​the continuous dislocation-free region 31 can be increased. As a result, when an InP substrate 100 and a semiconductor device are manufactured using the InP crystal 200, the device yield can be improved.

[0109] According to the manufacturing method of the InP crystal 200 in 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 bilateral symmetry about an imaginary line that intersects with the central axis C and extends along the 0° direction. This makes it possible to further flatten the shape of the portion of the solid-liquid interface S that is located near the central axis C and extends along the 0° direction. The dislocation density in the first main surface 1 can be reduced.

[0110] Although the above describes a configuration in which both the upper heating member 48a and the lower heating member 48b have thicknesses that vary along the circumferential direction R, the configuration of the manufacturing apparatus 300 according to the present disclosure is not limited to the above configuration. It is sufficient that the thickness of the heating unit 48 varies 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 unit 48 described above (see FIG. 11 or 12), and the thickness of the lower heating member 48b may not vary along the circumferential direction R. The portion of the heating unit 48 that is at the height where the solid-liquid interface S is located and that has the greatest radial thickness is defined as the thickest portion of the heating unit 48.

[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 in the crystal growing step (S40). In the VGF method and the like, the position of the solid-liquid interface S relative to the heating unit 48 changes during the crystal growth process. In this case, the height passed by the solid-liquid interface S from the start to the end of the crystal growing step (S40) is defined as the "height at which the solid-liquid interface S is located."

[0112] In the above description, the heating unit 48 is formed by two heating elements, but the heating unit 48 may be formed by three or more heating elements. The heating unit 48 is formed by, for example, four or less heating elements. The heating elements are arranged side by side in the vertically downward direction 112. The heating unit 48 may be formed by a single heating element. In other words, the heating unit 48 may be an integrated part.

[0113] Second Embodiment Next, the configuration of a manufacturing apparatus 300 according to a second embodiment will be described. FIG. 18 is a schematic plan view showing the configuration of the manufacturing apparatus 300 according to the second embodiment. As shown in FIG. 18, the heating section 48 does not need to have a radial thickness that does not change 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 above-mentioned upper heating member 48a and lower heating member 48b (see FIG. 10).

[0114] The first auxiliary heating unit 68 and the second auxiliary heating unit 69 are each located between the crucible 40 and the main heating unit 65. The first auxiliary heating unit 68 is located in the 0° direction. The second auxiliary heating unit 69 is located in the 180° direction. The first auxiliary heating unit 68 and the second auxiliary heating unit 69 are not located in either the 90° direction or the 270° direction. In other words, the crucible 40 faces the main heating unit 65 in either the 90° direction or the 270° direction.

[0115] According to the manufacturing apparatus 300 of the second embodiment, it is possible to form the same thermal distribution of the raw material melt 87 as when the manufacturing apparatus 300 of the first embodiment is used. Therefore, it is possible to manufacture the InP substrate 100 and the InP crystal 200 of the first embodiment in the same way as the manufacturing apparatus 300 of the first embodiment. [Example]

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

[0117] For 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 unit 48 was different. Specifically, the heating unit 48 did not change in radial thickness along the circumferential direction R. For 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 to 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 at the first center A1 was measured using the above-mentioned measurement method. In samples 1, 3 to 6, and 8 to 10, the carrier concentration at the first center A1 was 4.5 × 10 18 / cm 3 In samples 2 and 7, the carrier concentration at the first center A1 was 1.2 × 10 18 / cm 3 It was.

[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] The dislocation density was measured for all samples using the above-mentioned measurement method. The average dislocation density for all samples was 42.2 / cm 2 More than 45.2 / cm 2 In all the samples, the dislocation-free region rate in the first square regions 51 (first dislocation-free region rate) was 71.2% or more and 72.5% or less.

[0122] In Samples 1 to 5, the dislocation-free region ratio in the second tetragonal regions 52 (second dislocation-free region ratio) was 22.3% or more and 23.7% or less. In Samples 6 to 10, the second dislocation-free region ratio was 32.0% or more and 33.2% or less.

[0123] In Samples 1 to 5, the dislocation-free region ratio in the third tetragonal regions 53 (third dislocation-free region ratio) was 23.1% or more and 24.1% or less. In Samples 6 to 10, the third dislocation-free region ratio was 25.1% or more and 27.0% or less.

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

[0125] (Evaluation method) For all samples, the device yield when semiconductor devices were fabricated was calculated. Specifically, semiconductor devices (photodetectors) were fabricated using an InP substrate 100. The chip size of the semiconductor devices was 3 mm × 3 mm. The dark current of the fabricated semiconductor devices was measured. Semiconductor devices with dark currents higher than a threshold were determined to be defective. When semiconductor devices were fabricated 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 determined to be the device yield.

[0126] [Table 1]

[0127] [Table 2]

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

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

[0130] By comparing Samples 3 and 8, it was confirmed that the InP substrate 100 according to the example can improve the 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 can improve the device yield even when the carrier concentration is 1.2×10 18 / cm 3 It was also confirmed that the device yield can be improved by using the InP substrate 100 according to the example, regardless of whether the dopant is S, Sn, or Zn.

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

[0132] 19 and 21 show the presence or absence of dislocations in each of the multiple first square regions 51. Specifically, black regions indicate first square regions 51 where dislocations exist (dislocation regions 32), and white regions indicate first square regions 51 where no dislocations exist (dislocation-free regions 31).

[0133] 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 × 1 mm square centered on the second center A2. Specifically, black regions indicate second square regions 52 in which dislocations were present. White regions indicate second square regions 52 in which no dislocations were present.

[0134] As shown in Figures 19 and 20, it can be seen that dislocations are distributed relatively uniformly within the surface of Sample 1. On the other hand, as shown in Figures 21 and 22, it can be seen that the dislocation-free region is concentrated in the center of the substrate in Sample 6. Specifically, it can be seen that the dislocation-free region in the center of the substrate in Sample 6 extends along the vertical direction. The vertical direction in Figures 21 and 22 is the <0-11> direction.

[0135] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above-described embodiments and examples, and is intended to include meanings equivalent to the claims and all modifications within the scope thereof. [Explanation of symbols]

[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, 66 Part 1, 67 Part 2, 68 First auxiliary heating part, 69 Second auxiliary heating part, 70 Rectangular slice, 78 Electrode for measurement, 84 Crystals, 85 Lined Indium raw material, 86 Sealing material, 87 Raw material melt, 88 Liquid sealing material, 100 Lined Indium substrate (InP substrate), 101 First direction, 102 Second direction, 110 Growth direction, 111 Vertical upward direction, 112 Vertical downward direction, 200 Lined Indium 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. A main surface is provided. 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 is as follows: the main surface is formed by an outer peripheral region within 5 mm from the outer peripheral edge and a central region surrounded by the outer peripheral region, the central region is divided into first square regions, each having a side length of 1 mm and arranged in a grid pattern; when a square that surrounds nine of the first square regions and has a side length of 3 mm is moved by 1 mm along a first direction in which a first side of the first square region extends and along a second direction in which a second side connected to the first side extends, the areas specified by the square are 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 / cm ２ the ratio of the number of the second square regions is 30% or more, An indium phosphide substrate, wherein the carrier concentration at the center of the main surface is 1.0×10 18 / cm 3 or more.

2. The dislocation density in the first square region is measured, and the dislocation density is 0 / cm ２ When the first square region is a dislocation-free region, a region having a maximum area among regions formed by the dislocation-free regions that are continuous along either the first direction or the second direction is defined as a continuous dislocation-free region, 2. The indium phosphide substrate according to claim 1, wherein the ratio of the length of the continuous dislocation-free region in the longitudinal direction of the continuous dislocation-free region 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 １８ / cm ３ 3. The indium phosphide substrate according to claim 1, wherein:

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

5. 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, The method for producing indium phosphide crystal according to claim 4 , wherein 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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