Indium phosphide single crystal substrate and fabrication process for an indium phosphide single crystal

Abstract

The indium phosphide single-crystal substrate has a circular main surface, which is virtually subdivided by a square lattice with a lattice spacing of 1 mm. The square lattice consists of several lattice points arranged along a first direction and a second direction orthogonal to the first. A set consisting of dislocation densities measured at the respective lattice points has a first total area mean (the mean of the set) and a first total area standard deviation (the standard deviation of the set), and each of the dislocation densities is classified as a first-order, second-order, and third-order density.The grid points, each determined to have a dislocation density classified as a second-order density, lie in a region between the outline of a first square region and the outline of a second square region, and a second mean, as the mean of a subset consisting of the dislocation densities each classified as a second-order density, is greater than or equal to 4.0 times and less than or equal to 10.0 times a first mean as the mean of a subset consisting of the dislocation densities each classified as a first-order density.

Description

Technical field

[0001] The present disclosure relates to an indium phosphide single crystal substrate and a manufacturing process for an indium phosphide single crystal. State of the art

[0002] The disclosed Japanese patent No. 06-227898 (PTL 1) discloses an indium phosphide single-crystal substrate (hereinafter also referred to as the “InP single-crystal substrate”) with a diameter of 2 inches or more, doped with zinc (Zn) to achieve a mean dislocation density of 2000 cm³ in the main surface. -2 or less. WO 2005 / 106083 (PTL 2) discloses an iron (Fe) doped or undoped InP single-crystal substrate in which an area comprising 70 area percent or more of the main surface has a dislocation density of 500 cm³ -2or less. The NPL 1 shown later reveals a single-crystal InP substrate with a diameter of 6 inches, doped with Fe to achieve a dislocation density of 4200 cm³. -2 or less. WO 2004 / 106597 (PTL 3) discloses an InP single-crystal substrate with a diameter of 75 mm or larger and doped with Fe, sulfur (S), tin (Sn) or Zn to achieve a mean dislocation density of 5000 cm³ in the main surface. -2 or to receive less. List of cited writings / patent literature PTL 1: Japanese Patent Publication No. 06-227898 PTL 2: WO 2005 / 106083 PTL 3: WO 2004 / 106597 Non-patented literature

[0003] NPL 1: T. Morishita et al., “Crystal Growth and Wafer Processing of 6-inch InP Substrate,” CS Man Tech Conf. (2016) Overview of the invention

[0004] An indium phosphide single-crystal substrate according to the present disclosure is an indium phosphide single-crystal substrate with a circular principal surface. The principal surface is a (100) plane of an indium phosphide single crystal that forms the indium phosphide single-crystal substrate. The principal surface is virtually subdivided into a square lattice with a lattice spacing of 1 mm. The square lattice is composed of several lattice points arranged along a first direction and a second direction orthogonal to the first direction. A set consisting of dislocation densities measured at the respective lattice points has a first total area mean as a mean of the set and a first total area standard deviation as a standard deviation of the set, and each of the dislocation densities is classified as a first-order, second-order, or third-order dislocation density.The grid points, each of which is determined to have a dislocation density classified as second level, are located in a region between the outline of a first square region and the outline of a second square region, and a second mean, as the mean of a subset consisting of the dislocation densities each classified as second level, is greater than or equal to 4 times and less than or equal to 10 times a first mean, which is considered to be the mean of a subset consisting of dislocation densities each classified as first level.

[0005] The dislocation densities, which are each classified as the first stage, are in the range of 0 cm. -2 or greater and less than X0.

[0006] The dislocation densities, which are each classified as second level, are in the range of X0 or greater and X1 or less.

[0007] The dislocation densities, each classified as the third level, are in the range greater than X1.

[0008] X0 is 1 / a, satisfies the relation X0 > 0 and has the unit cm. -2 . a in 1 / a is determined by approximating the frequency distribution of the set in a histogram with an ordinate showing the cumulative relative frequencies as y and an abscissa showing the class values ​​as x, using the expression I shown below.

[0009] X1 is a value resulting from the sum of the first total area mean and a value of the first total area standard deviation, multiplied by 3, which satisfies the relationship X1 > X0 and has the unit cm. -2 has.

[0010] x is a minimum value in each section of the histogram, where the width of each section is the quotient of x1 divided by 100, and the unit is cm. -2has, and y is a dimensionless number.

[0011] The first square region has a square shape centered on a midpoint of the main surface. The first square region has vertices as endpoints of first line segments of identical length extending from the midpoint in four directions corresponding to a

[011] direction of the indium phosphide single crystal. The length of each first line segment is 70% of the radius of the indium phosphide single crystal substrate. The second square region has a square shape centered on the midpoint. The second square region has vertices as endpoints of second line segments of identical length extending from the midpoint in four directions corresponding to a

[011] direction of the indium phosphide single crystal. The length of each second line segment is 130% of the radius of the indium phosphide single crystal substrate. y=(1−b)×{1−exp(−ax)}+b

[0012] In expression I, a satisfies the relation a > 0 and has the unit cm. 2 , and b is a dimensionless number that satisfies the relation 0 ≤ b < 1. Brief description of the drawings Fig. Figure 1 is a schematic representation of an indium phosphide single crystal substrate according to the present embodiment. Fig. Figure 2 is a clear diagram showing the virtual decomposition of a main surface of the indium phosphide single crystal substrate according to the present embodiment with a square lattice with a lattice interval of 1 mm for determining dislocation densities in the main surface. Fig.Figure 3 is an illustrative diagram for the indium phosphide single crystal substrate according to the present embodiment, wherein the diagram schematically shows dislocation densities at lattice points, each classified into a first stage, a second stage or a third stage, as a dislocation density distribution in the main surface with representation using hatching shading. Fig. Figure 4 is a clear diagram showing grid points, each of which has a dislocation density classified as second level, where the grid points were extracted from the dislocation density distribution taken from the main surface of the Fig. 3 indium phosphide single crystal substrate was obtained. Fig.Figure 5 is a graphical diagram that schematically represents an area in which lattice points, each of which has a dislocation density classified as second stage, are present in the main surface of the indium phosphide single crystal substrate according to the present embodiment. Fig. Figure 6 is a clear diagram showing an area (e.g., first division) extracted from four areas (first division, second division, third division, and fourth division) that are defined by the virtual division of the area in Fig. 4 indium phosphide single crystal substrate shown by two orthogonal straight lines that intersect at the center of the main surface. Fig. Figure 7 is a flowchart describing an example of a manufacturing process for an indium phosphide single crystal according to the present embodiment. Fig.Figure 8 is a clear cross-sectional view showing a single-crystal growth device to be used in the manufacturing process for an indium phosphide single crystal according to the present embodiment, and the internal state of a crucible of the single-crystal growth device during indium phosphide single-crystal production. Fig. Figure 9 is a clear diagram illustrating a characteristic part (interface shape) of Fig. 8. Detailed description [problem to be solved by the present disclosure]

[0013] For InP single-crystal substrates, as disclosed in PTLs 1 to 3 and NPL 1, tighter yields are required in some cases in a process for fabricating a semiconductor device by growing an epitaxial film on the main surface. In particular, during the growth of an epitaxial layer on the main surface of an InP single-crystal substrate, breakage or spalling of the substrate can occur, which is referred to as a fracture defect, and it has been required to reduce the probability of the occurrence of the fracture defect (hereinafter also referred to as the "fracture defect rate"). In such a situation, InP single-crystal substrates, as disclosed in PTLs 1 to 3 and NPL 1, are still capable of improvement with respect to reducing the fracture rate.

[0014] In view of these circumstances, it is an objective of the present disclosure to provide indium phosphide single-crystal substrates with a reduced fracture rate and a manufacturing process for an indium phosphide single crystal. [Beneficial effect of the present disclosure]

[0015] The present disclosure can provide indium phosphide single-crystal substrates with a reduced fracture rate and a manufacturing process for an indium phosphide single crystal. [Description of embodiments]

[0016] The following is an overview of embodiments of the present disclosure. The inventors have conducted a careful investigation to solve the aforementioned problems and have accordingly completed the present disclosure. In particular, for a method for growing an indium phosphide single crystal (hereinafter also referred to as the "InP single crystal") in a crucible of a single-crystal growth apparatus using a vertical boat method, we have focused on the following points relating to the components of the single-crystal growth apparatus and the growth of the InP single crystal. First, a heater, which is part of the single-crystal growth apparatus, was constructed with two components (hereinafter also referred to as the "first heating section" and the "second heating section"), the power outputs of which could each be adjusted independently.Furthermore, a structure was used in which the second heating region surrounds the boundary region of the first heating region, except for the inner edge. Additionally, an InP single crystal was grown by maintaining the interface between a growing InP single crystal and an indium phosphide melt in the crucible at a specific distance parallel to the axial direction of the crucible below a specific position of the first heating region. It was found that when InP single-crystal substrates are produced from an ingot of the InP single crystal obtained by such a method, and an epitaxial layer has grown on the main surface of each substrate, the substrates exhibit a reduced fracture defect rate, thus achieving the objective of the present disclosure.

[0017] The following is a list describing embodiments of the present disclosure.

[0018] [1] An indium phosphide single-crystal substrate according to one aspect of the present disclosure is an indium phosphide single-crystal substrate having a circular principal surface. The principal surface is a (100) plane of an indium phosphide single crystal that forms the indium phosphide single-crystal substrate. The principal surface is virtually subdivided by a square lattice with a lattice spacing of 1 mm. The square lattice consists of several lattice points arranged along a first direction and a second direction orthogonal to the first direction. A group or set consisting of dislocation densities measured at the respective lattice points has a first total area mean as the mean of the set and a first total area standard deviation as the standard deviation of the set, and each of the dislocation densities is classified as a first-order, second-order, or third-order dislocation density.The grid points, each of which is determined to have a dislocation density classified as second level, are located in a region between the outline of a first square region and the outline of a second square region, and a second mean, as the mean of a subset consisting of the dislocation densities each classified as second level, is 4.0 times or greater and 10.0 times or less than a first mean, which is the mean of a subset consisting of the dislocation densities each classified as first level.

[0019] The dislocation densities, which are classified as the first stage, are in the range of 0 cm. -2 or higher and less than X0.

[0020] The dislocation densities, which are each classified as the second level, are in the range of X0 or higher and X1 or less.

[0021] The dislocation densities, which are each classified as the third level, are in the range of more than X1.

[0022] X0 is 1 / a, satisfies the relation X0 > 0 and has the unit cm. -2 . a in 1 / a is determined by approximating the frequency distribution of the set in a histogram with an ordinate that shows the cumulative relative frequencies as y and an abscissa that shows the class values ​​as x, using the expression I shown below.

[0023] X1 is a value obtained by multiplying the sum of the first total area mean and a value of the first total area standard deviation by 3, which satisfies the relationship X1 > X0 and has the unit cm. -2 has.

[0024] x is a minimum value in each section of the histogram, where the width of each section is the quotient of x1 divided by 100, and the unit is cm. -2is, and y is a dimensionless number.

[0025] The first square region has a square shape centered around a center point of the main surface. The first square region has vertices as endpoints of first line segments of identical length extending from the center point in four directions corresponding to a

[011] direction of the indium phosphide single crystal. The length of each first line segment is 70% of the radius of the indium phosphide single crystal substrate. The second square region has a square shape centered around the center point. The second square region has vertices as endpoints of second line segments of identical length extending from the center point in four directions corresponding to a

[011] direction of the indium phosphide single crystal. The length of each second line segment is 130% of the radius of the indium phosphide single crystal substrate. y=(1−b)×{1−exp(−ax)}+b

[0026] In expression I, a satisfies the relation a > 0 and has the unit cm. 2 , and b is a dimensionless number that satisfies the relationship 0 ≤ b < 1. Indium phosphide single-crystal substrates with such features can exhibit lower fracture rates.

[0027] [2] The indium phosphide single crystal substrate preferably satisfies the following relationships: 0.8×N_20 / N_0≤N_21 / N_1≤1.2×N_20 / N_0; 0.8×N_20 / N_0≤N_22 / N_2≤1.2×N_20 / N_0; 0.8×N_20 / N_0≤N_23 / N_3≤1.2×N_20 / N_0; and 0.8×N_20 / N_0≤N_24 / N_4≤1.2×N_20 / N_0

[0028] in a first division, a second division, a third division and a fourth division, which are practically given by two orthogonal straight lines extending from the center in four directions corresponding to a

[011] direction of the indium phosphide single crystal.

[0029] N_20 is the total number of grid points, each of which has a dislocation density that is classified as second level.

[0030] N_0 is the total number of grid points that are subjected to the measurement of the dislocation density.

[0031] N_21, N_22, N_23 and N_24 are the total number of grid points, each classified as dislocation density according to the second level in the first division, in the second division, in the third division and in the fourth division.

[0032] N_1, N_2, N_3, and N_4 are the total number of grid points at which the dislocation density is measured in the first, second, third, and fourth divisions, respectively. These allow for a lower breakage rate.

[0033] [3] The second mean is preferably 4.3 times or more and 9.0 times or less than the first mean. Preferably, the following relationships are satisfied in the first, second, third, and fourth divisions: 0.90×N_20 / N_0≤N_21 / N_1≤1.07×N_20 / N_0; 0.90×N_20 / N_0≤N_22 / N_2≤1.07×N_20 / N_0; 0.90×N_20 / N_0≤N_23 / N_3≤1.07×N_20 / N_0; and 0.90×N_20 / N_0≤N_24 / N_4≤1.07×N_20 / N_0

[0034] In this way, lower breakage rates can be achieved.

[0035] [4] The indium phosphide single-crystal substrate preferably has a diameter of 75 mm or more and 76.5 mm or less. This allows lower breakage rates to be achieved for large indium phosphide single-crystal substrates with a diameter of 75 mm or more and 76.5 mm or less.

[0036] [5] The indium phosphide single crystal substrate contains one or more dopants selected from the group consisting of sulfur, tin, iron and zinc, and the atomic concentration of the dopants in the indium phosphide single crystal substrate is preferably 1.0 × 10 17 cm -3 or higher and 1.0 × 10 19 cm -3 or less. This allows indium phosphide single-crystal substrates containing dopants to achieve lower fracture rates.

[0037] [6] A manufacturing process for an indium phosphide single crystal substrate according to one aspect of the present disclosure is a manufacturing process for an indium phosphide single crystal which is to be produced by a vertical boat process.The manufacturing process comprises: providing a single-crystal growth apparatus comprising at least one cylindrical crucible and a heater arranged to surround an outer circumference of the crucible; placing a seed crystal in a lower part of the crucible and placing an indium phosphide bulk above the seed crystal in the crucible; generating an indium phosphide melt by melting the indium phosphide bulk and a portion of the seed crystal by heating the crucible with the heater and bringing the indium phosphide melt into contact with a remaining portion of the seed crystal; and obtaining an indium phosphide single crystal by growing a crystal on the remaining portion of the seed crystal from the indium phosphide melt.

[0038] The heating element has a first heating area and a second heating area, which is located axially to the crucible and supports the first heating area. The first heating area has a first surface and a second surface. The second heating area has a third surface and a fourth surface. The third surface faces the first surface, which is located on the upper side of the axial direction within the first heating area. The fourth surface faces the second surface, which is located on the lower side of the axial direction within the first heating area. An outer circumference of the first heating area is enclosed by the second heating area. A first side surface, forming an inner circumference of the first heating area, lies in a cylindrical plane that encloses a second side surface, which forms an inner circumference of the second heating area.The first heating zone is designed to heat the crucible with a power output that differs from that of the second heating zone. The distance from the center of a radial direction of the crucible to the first and second side faces is 60 mm or more and 65 mm or less, respectively.

[0039] In the production of the indium phosphide single crystal, in a plane of a first cross-section parallel to the axial direction and containing the center of the radial direction of the crucible, the inner circumferential edges of the first face, the second face, the third face, and the fourth face are defined in the radial direction as a first position, a second position, a third position, and a fourth position, respectively; a midpoint of the first position and the second position in the axial direction is defined as a fifth position; and temperatures at the third position, the fourth position, and the fifth position are defined as a first temperature, a second temperature, and a third temperature, respectively, and the heating is maintained using outputs in the first heating area and the second heating area. the third temperature at a value that is lower than that of the first temperature and lower than that of the second temperature; a difference between the second temperature and the third temperature of 1°C or more and 2°C or less; furthermore, the heater generates: a temperature gradient of 0.295°C / mm or more and 0.305°C / mm or less parallel to the axial direction in a range of 50 mm or more and 65 mm or less below the fifth position parallel to the axial direction; a temperature gradient of 0.235°C / mm or more and 0.245°C / mm or less parallel to the axial direction in a range of 25 mm or more and less than 50 mm below the fifth position parallel to the axial direction; a temperature gradient of 0.095°C / mm or more and 0.105°C / mm or less parallel to the axial direction in a range of 0 mm or more and less than 25 mm below the fifth position parallel to the axial direction; a temperature gradient of 0.055°C / mm or more and 0.065°C / mm or less parallel to the axial direction in a range of more than 0 mm and 35 mm or less above the fifth position parallel to the axial direction; and a temperature gradient of 0.035°C / mm or more and 0.045°C / mm or less parallel to the axial direction in a range of more than 35 mm and 85 mm or less above the fifth position parallel to the axial direction.

[0040] The production of the indium phosphide single crystal involves growing or pulling the crystal by maintaining a position of an interface between the indium phosphide melt and the crystal on an inner circumferential surface of the crucible within a range of 43 mm or more and 45 mm or less below the fifth position parallel to the axial direction. With these characteristics, the indium phosphide single crystal production process is capable of yielding a single crystal for the production of indium phosphide single-crystal substrates with reduced breakage rates.

[0041] [7] Preferably, the cross-sectional shape of the interface, which is to appear in the first cross-section, includes at least a curved line segment. The curved line segment has a local maximum point located in the middle of the curved line segment and two local minimum points located on either side of the local maximum point in the radial direction. In the axial direction, the positions of the two ends of the curved line segment are higher than the local minimum points. These make it possible to obtain an indium phosphide single crystal for the preparation of indium phosphide single-crystal substrates with reduced fracture rates and good yield.

[0042] [8] The curved line segment preferably satisfies the following relationships: R / √2−0.1R≤D1≤R / √2+0.1R; 0.1D1≤D2; and 0,1(R−D1)≤D3. R is the bore radius of the crucible and has the unit mm.

[0043] D1 is a distance between a point corresponding to the local maximum point on a first line segment and a point corresponding to one of the local minimum points on the first line segment, and has the unit mm, where the first line segment appears when the curved part of the line is virtually projected onto a straight line parallel to the radial direction.

[0044] D2 is a distance between a point corresponding to the local maximum point on a second line segment and a point corresponding to one of the local minimum points on the second line segment, and has the unit mm, where the second line segment appears when the curved part of the line is virtually projected onto a straight line parallel to the axial direction.

[0045] D3 is a distance between a point corresponding to a first local minimum on the second line segment and a point corresponding to a first endpoint on the second line segment, and has a unit of mm, where the first local minimum is one of the two local minimums and the first endpoint is the endpoint of the two ends that is closer to the first local minimum. This makes it possible to obtain an indium phosphide single crystal for the fabrication of indium phosphide single-crystal substrates with reduced fracture rates and good yield. [Details of embodiments]

[0046] One embodiment according to the present disclosure (hereinafter also referred to as "the present embodiment") is described in more detail below, but the present disclosure is by no means limited to it. While reference is occasionally made to drawings below, identical elements in the description and the drawings are identified by identical reference numerals, and redundant descriptions are omitted. In each drawing, the components are shown to a reasonable scale to facilitate understanding, and the scale of each component shown in each drawing need not necessarily correspond to the scale of the actual component.

[0047] Herein, a representation in the form "A to B" signifies the upper and lower limits of a range (i.e., A or more and B or less); if a unit is specified only for B and not for A, the unit of A and the unit of B are the same. Unless otherwise specified in this specification, the compound or the like may contain any conventionally known atomic ratio in the representation of a compound or the like as a chemical formula, and should not be restricted to those satisfying stoichiometry.

[0048] The term "main surface" for an indium phosphide single-crystal substrate refers here to the two circular faces of the indium phosphide single-crystal substrate. If at least one of the two faces of the indium phosphide single-crystal substrate satisfies one of the claims according to the present disclosure, the indium phosphide single-crystal substrate falls within the technical scope of the present disclosure. The term "plane" used in the phrase "in a plane" refers here to the "main face". The statement that the indium phosphide single-crystal substrate has a diameter of 3 inches means that the diameter is 75 to 76.5 mm. The diameter can be measured with a conventional measuring instrument for outside diameters, e.g., a caliper.

[0049] In this context, the terms "dislocation" and "dislocation density" refer accordingly to "etch pits" that are detected by applying a treatment described later to a main surface, and to "the number of etch pits per 1 cm²". 2 of the main surface (density). Although the term "etch pit" is not synonymous with the term "dislocation" in an academic sense, etch pits can be considered equivalent to dislocations in the scientific community. Furthermore, the term "dislocation" refers to a "filamentary dislocation" present within an indium phosphide single crystal, and the "filamentary dislocation" is known as a type of crystal defect.

[0050] In this context, a “fracture rate” can be defined as the rate of occurrence of fractures, chipping or similar phenomena in indium phosphide single-crystal substrates in a series of steps from the growth of an epitaxial layer on each substrate to the formation of a semiconductor layer or similar, up to the fabrication of a semiconductor device.

[0051] The "failure rate" can be expressed as a percentage. The term "processing yield" refers to the proportion of semiconductor devices that are successfully fabricated from indium phosphide single-crystal substrates without breakage, chipping, or similar defects occurring during processing. The "failure rate" is a factor in determining the "processing yield," and it fulfills the relationship 100% - "failure rate" = "processing yield."

[0052] In crystallographic descriptions within this specification, individual orientations are represented by [], collective orientations by <>, individual planes by (), and collective planes by {}. While a negative crystallographic index is usually represented by a "-" (bar) above a number, here a negative sign is placed before a number to indicate negativity. [Indium phosphide single crystal substrate]

[0053] The indium phosphide single-crystal substrate (InP single-crystal substrate) according to the present embodiment is an InP single-crystal substrate with a circular main surface. The main surface is a (100) plane of an indium phosphide single crystal (InP single-crystal) that forms the InP single-crystal substrate. The main surface is virtually subdivided by a square lattice at a spacing of 1 mm. The square lattice consists of several lattice points arranged along a first direction and a second direction orthogonal to the first. A set or group consisting of dislocation densities measured at the respective lattice points has a first total area mean as the mean of the set and a first total area standard deviation as the standard deviation of the set, and each of the dislocation densities is classified as a first stage, a second stage, or a third stage.The grid points for which a second-order dislocation density was determined lie in a region between the outline of a first square region and the outline of a second square region. A second mean, as the mean of a subset consisting of the dislocation densities classified as second order, is 4.0 times greater and 10.0 times less than a first mean, as the mean of a subset consisting of the dislocation densities classified as first order.

[0054] The dislocation densities, which are each classified as first-order densities, are in the range of greater than or equal to 0 cm. -2Dislocation densities, classified as second-order densities, range from greater than or equal to X0 to greater than or equal to X1. Dislocation densities, classified as third-order densities, range greater than X1.

[0055] X0 is 1 / a, satisfies the relation X0 > 0 and has the unit cm. -2 . a in 1 / a is determined by approximating the frequency distribution of the set in a histogram with an ordinate showing the cumulative relative frequencies as y and an abscissa showing the class values ​​as x, where the expression I is represented as follows. y=(1−b)×{1−exp(−ax)}+b

[0056] In expression I, a satisfies the relation a > 0 and has the unit cm. 2 , and b is a dimensionless number that satisfies the relation 0 ≤ b < 1.

[0057] X1 is a value obtained by multiplying the sum of the first total area mean and a value of the first total area standard deviation by 3, satisfying the relationship X1 > X0, and having the unit cm. -2 has.

[0058] x is a minimum value in each section of the histogram, where the width of each section is the quotient of X1 divided by 100, and the unit is cm. -2 has, and y is a dimensionless number.

[0059] The first square region has a square shape centered on a midpoint of the main surface. The first square region has vertices as endpoints of first line segments of identical length extending from the midpoint in four directions corresponding to a

[011] direction of the indium phosphide single crystal. The length of each first line segment is 70% of the radius of the indium phosphide single crystal substrate. The second square region has a square shape centered on the midpoint. The second square region has vertices as endpoints of second line segments of identical length extending from the midpoint in four directions corresponding to a

[011] direction of the indium phosphide single crystal. The length of each second line segment is 130% of the radius of the indium phosphide single crystal substrate.Indium phosphide single-crystal substrates with such features may exhibit a lower fracture rate.

[0060] The inventors have derived the reason why such an InP single-crystal substrate can achieve lower breakage rates as follows. First, the InP single-crystal substrate is formed from an InP single crystal. The InP single crystal is produced using a special indium phosphide single-crystal growth device (hereinafter also referred to simply as the "single-crystal growth device") based on a process described in the section [Process for Indium Phosphide Single Crystal] presented later. In particular, by using the single-crystal growth device, the InP single crystal is produced under strict control of the position and shape of an interface between an InP single crystal and an indium phosphide melt (hereinafter also referred to as the "InP melt") in a crucible.This allows the InP single crystal to grow under a heat distribution characteristic of the radial direction of the crucible, resulting in an InP single crystal block with a dislocation density distribution corresponding to the heat distribution.

[0061] The ingot has a circular shape, which in plan view corresponds to the inner circumferential surface of the crucible that is part of the single crystal growth device.Furthermore, the ingot has the property that a region with dislocation densities belonging to the second stage described later is concentrated between two square regions, one of which is centered at a center point of the circular shape and has vertices as endpoints of line segments extending from the center point in four directions corresponding to a

[011] direction of the InP single crystal, each having a length of 70% of the radius of the ingot, and the other is centered in a planar view on a center point of the ingot and has vertices as endpoints of line segments extending from the center point in four directions corresponding to a

[011] direction of the InP single crystal, each having a length of 130% of the radius of the InP single crystal.The inventors have discovered that InP single-crystal substrates produced from such an ingot exhibit high resistance to fracture, chipping, and similar damage caused by thermal fluctuations during the growth of an epitaxial layer on the main surface. This high resistance is achieved because the region with dislocation densities belonging to the second stage relieves the stress exerted on the substrate by the thermal variation during the growth of an epitaxial layer on the main surface. Probably for this reason, the InP single-crystal substrate according to the present embodiment can achieve lower fracture rates during the growth of an epitaxial layer on the main surface.The InP single-crystal substrate according to the present embodiment should not be restricted with respect to its fabrication method, as long as lower breakage rates can be achieved for the InP single-crystal substrate by means of the features described below. Accordingly, it should be noted that a fabrication method for an InP single crystal, as described in the section [Process for Indium Phosphide Single Crystal], is preferred with regard to the possibility of producing it in high yields, but is only one example of an InP single crystal that enables the fabrication of the InP single-crystal substrate according to the present embodiment. <durchmesser>

[0062] The diameter of the InP single-crystal substrate is preferably greater than or equal to 75 mm and less than or equal to 76.5 mm. In other words, an InP single-crystal substrate with a diameter greater than or equal to 75 mm and less than or equal to 76.5 mm is a 3-inch diameter InP single-crystal substrate. Lower breakage rates can be achieved for InP single-crystal substrates with such a larger diameter of 75 mm or more and 76.5 mm or less. Even if the main surface has a non-geometrically circular shape due to the influence of an orientation surface (hereinafter also referred to as "OF"), an index surface (hereinafter also referred to as "IF"), or the like, the diameter of the InP single-crystal substrate is determined to be circular before the formation of such an OF, IF, or the like.As already mentioned, the diameter of the InP single crystal substrate can be measured using a conventional measuring instrument for the outside diameter, such as a caliper. <Hauptoberfläche>

[0063] Fig. Figure 1 is a clear diagram that schematically illustrates an example of an indium phosphide single-crystal substrate according to the present embodiment. As shown in Fig. As shown in Figure 1, an InP single-crystal substrate 1 according to the present embodiment has a circular main surface 11. The meaning of the term "circular," which indicates the shape of the main surface, includes not only a geometrically circular shape but also a shape for the case where the main surface does not form a geometrically circular shape because at least one notch, OF, or IF is formed on the outer circumference of the main surface. Here, the "shape for the case where the main surface does not form a geometrically circular shape" is such that line segments extending from any point on the notch, OF, or IF to the center of the main surface are shorter than those extending from any point on the outer circumference of the main surface to the center of the main surface.Furthermore, the meaning of the expression "shape in the case that the main surface does not form a geometrically circular shape" includes a shape such that the lengths of all line segments extending from any point on the outer circumference of the main surface to the center of the main surface are not necessarily identical due to the shape of an InP single crystal as the raw material of the InP single-crystal substrate. In this case, the center of the main surface is the position of the centroid. The diameter of the InP single-crystal substrate is defined as the length of the longest line segment among those extending from any point on the outer circumference of the InP single-crystal substrate, through the center of the main surface, to any other point on the outer circumference. ((100)-plane of an indium phosphide single crystal)

[0064] The main surface 11 is a (100) plane of an InP single crystal that forms the InP single-crystal substrate 1. The (001) plane of the InP single crystal is known to be one of the crystal planes commonly used in the formation of a semiconductor layer for the InP single-crystal substrate 1 by the growth of an epitaxial layer. In the present disclosure, an accuracy error of ± 0.5° is permitted for the crystal plane of the main surface. The statement that the main surface is a “(100) plane” of the InP single crystal means that the main surface can only be the (100) plane or a plane inclined at an angle of -0.5° to +0.5° to the (100) plane. Whether the crystal plane of the main surface of the InP single-crystal substrate is the (100) plane can be determined using a conventionally known method for measuring crystal orientation. (Dislocation density or density of dislocations)

[0065] As described above, the main surface 11 of the InP single-crystal substrate 1 is equipped with a dislocation density distribution to contribute to reduced breakage rates. This is achieved by growing the InP single crystal as raw material under a heat distribution characteristic of the radial direction of the crucible using a method described in the section [Processing Method for Indium Phosphide Single Crystal]. The following section describes in detail the dislocation density distribution on the main surface 11 of the InP single-crystal substrate 1 that contributes to reducing the breakage rate. 1) Classification of the dislocation densities measured at the respective grid points as first-order, second-order or third-order density

[0066] Fig. Figure 2 is an illustrative diagram showing the virtual subdivision of the main surface of the indium phosphide single-crystal substrate according to the present embodiment with a square grid having a grid interval of 1 mm for determining the dislocation density in the main surface. As shown in Fig. As shown in Figure 2, the main surface 11 of the InP single-crystal substrate 1 is virtually subdivided by a square lattice G with a lattice spacing of 1 mm. The square lattice G consists of several lattice points P arranged along a first direction and a second direction, orthogonal to the first direction. The first and second directions can be defined along any crystal orientation of the InP single crystal, as long as the directions satisfy the orthogonal relationship on the main surface 11, which is designated as the (100) plane of the InP single crystal. This is because the first and second directions are used only to assemble the square lattice G in order to define the lattice points P as measurement points for determining the dislocation density on the main surface 11.A method for measuring dislocation densities at the respective lattice points P on the main surface 11 is described below.

[0067] A group or set consisting of dislocation densities measured at corresponding grid points P has a first total area mean as the mean of the set and a first total area standard deviation as the standard deviation of the set. Each of the dislocation densities is classified as a first-level, second-level, or third-level density. The first total area mean and first total area standard deviation are used to classify dislocation densities measured at corresponding grid points P as first-level, second-level, and third-level densities, as described below. In particular, the first total area mean and first total area standard deviation are used to determine X1, which serves as an index to determine which of the two levels a dislocation density should be assigned to.In particular, it is preferable that the first total area mean is greater than or equal to 30 cm. -2 and less than or equal to 500 cm -2 In particular, it is desirable that the first total area standard deviation be greater than or equal to 90 cm. -2 and less than or equal to 300 cm -2 amounts.

[0068] The dislocation density value increases in the following order: first level, second level, and third level. That is, the dislocation density values ​​satisfy the relationship: first level < second level < third level. Specifically, the dislocation densities of the first level are each greater than or equal to 0 cm. -2 and less than X0. The dislocation densities of the second level are each in the range greater than or equal to X0 and less than or equal to X1. The dislocation densities of the third level are each in the range greater than X1. X0 is 1 / a, satisfies a relationship X0 > 0, and has a unit of cm. -2 . a in 1 / a is determined by approximating the frequency distribution of the set in a histogram with an ordinate showing cumulative relative frequencies as y and an abscissa showing class values ​​as x, using the expression I as follows. y=(1−b)×{1−exp(−ax)}+b

[0069] In expression I, a satisfies the relation a > 0 and has the unit cm. 2 , and b is a dimensionless number that satisfies the relation 0 ≤ b < 1.

[0070] X1 is a value obtained by multiplying the sum of the first total area mean and a value of the first total area standard deviation by 3, satisfying the relationship X1 > X0 and having a unit of cm. -2 x is a minimum value in each section of the histogram, where the width of each section is the quotient of x1 and 100, and has the unit cm. -2 , and y is a dimensionless number.

[0071] In the InP single-crystal substrate 1, in such a situation, a second mean value, as the mean of a subset consisting of dislocation densities each classified as second-order densities, is 4.0 times or more and 10.0 times or less than a first mean value, as the mean of a subset consisting of dislocation densities each classified as first-order densities. It is preferable that the second mean value be greater than or equal to 4.3 times and less than or equal to 9.0 times the first mean value.

[0072] For this purpose, a method for measuring dislocation densities at a plurality of lattice points P on the main surface 11 is required with reference to Fig. 2. First, an InP single crystal is prepared, for example, using a fabrication method described later. The InP single crystal is subjected to a cutting process in a known manner and ground on its outer circumference, resulting in an InP single-crystal substrate 1 with a thickness of 1 mm for measurement. The InP single-crystal substrate 1 is then washed with water and highly polished with a solution containing a known polishing agent diluted in it. The highly polished InP single-crystal substrate 1 is then soaked in a Huber etching solution containing phosphoric acid and hydrogen bromide in a mass ratio of 2:1 at 20°C for 2 to 7 minutes to form pitting on the main surface 11. These pittings correspond to the etching depressions.

[0073] Next, 1 mm × 1 mm squares are distributed in a densest possible arrangement without overlap over the entire surface of the main surface 11 of the InP single-crystal substrate 1, which was extracted from the Huber etching solution, so that a virtual square lattice G with a grid spacing of 1 mm is formed. The main surface 11 is subdivided by this virtual square lattice G. The square lattice G consists of several grid points P arranged along a first direction and a second direction orthogonal to the first. Subsequently, a view of a 4 mm × 4 mm square centered on each grid point P is established, and the etch pits present in the view are observed using a known optical microscope, and the number of etch pits is counted. Finally, the number of etch pits present in each view is converted into the number per 1 cm². 2 converted. In this way, the number of etch pits per 1 cm can be determined. 2 The dislocation density, corresponding to the surface area of ​​the main surface 11, is determined for all lattice points P forming the square lattice G. If the outer edge and the outer surface of the main surface 11 appear in such a view, the view is excluded for calculating the dislocation density. The reason for this is that, in an InP single-crystal substrate 1, the number of etch pits varies greatly in the regions near the outer perimeter between the substrates, and such regions are generally not used as material for optical devices.

[0074] The described method for measuring dislocation densities can yield a set consisting of dislocation densities measured at corresponding lattice points P in the InP single-crystal substrate 1. Furthermore, a first total area mean can be calculated as the mean of the set, and a first total area standard deviation can be calculated as the standard deviation of the set. The dislocation densities measured at the respective lattice points P can each be classified as first-, second-, or third-order density based on the indices described above. 2) Area in which there are grid points, each of which has a dislocation density of level two

[0075] Fig. Figure 3 is a graphical diagram for the indium phosphide single crystal substrate according to the present embodiment, wherein the diagram schematically shows dislocation densities at lattice points, each dislocation density being classified as a first-level, second-level or third-level density, in the form of a dislocation density distribution in the main surface with representation using hatching shading. Fig. Figure 4 is a clear diagram showing lattice points, each of which has a dislocation density classified as a second-order density, where the lattice points were extracted from the dislocation density distribution taken from the main surface of the Fig. The 3 indium phosphide single-crystal substrates shown are obtained. Fig. Figure 3 shows the dislocation density distribution, based on dislocation densities measured at corresponding lattice points virtually fixed on the main surface of the InP single-crystal substrate, reproduced using hatching. Specifically, the dislocation density distribution is shown such that the hatching becomes thicker in the order of the lattice points L1, L2, and L3, which are classified as first stage, second stage, and third stage, respectively. Furthermore, it is shown that... Fig. 4. It is evident that the lattice points L2, each exhibiting a dislocation density classified as a second-order density, have a distribution like inequality signs (<, >) on the main surface of the InP single-crystal substrate. That is, in the InP single-crystal substrate, the lattice points L2, each exhibiting a dislocation density classified as a second order, are located in a region R between a contour F1 of a first square region S1 and a contour F2 of a second square region S2, as shown in Fig. 5 shown.

[0076] Fig. Figure 5 is a clear diagram schematically representing a region in which lattice points, each exhibiting a dislocation density classified as a second-order density, are present on the main surface of the indium phosphide single-crystal substrate according to the present embodiment. Fig. 5 is the region R in which grid points L2 are present, each exhibiting a dislocation density classified as second-order density, represented by hatching. The first square region S1 in Fig. 5 has a square shape centered at a midpoint O of the main surface 11. The first square region S1 has vertices as endpoints of first line segments M1 of identical lengths extending from the midpoint O in four directions corresponding to a

[011] direction of the InP single crystal. The length of each first line segment M1 is 70% of the radius of the InP single crystal substrate 1. The second square region S2 has a square shape centered at the midpoint O. The second square region S2 has vertices as endpoints of second line segments M2 of identical lengths extending from the midpoint O in four directions corresponding to a

[011] direction of the InP single crystal. The length of each second line segment M2 is 130% of the radius of the InP single crystal substrate 1.

[0077] Due to the presence of lattice points L2, each of which has a dislocation density classified as the second-order density in the region R, as in Fig. As shown in Figure 5, the stress exerted on the InP single-crystal substrate 1 by the thermal variation during the growth of an epitaxial layer is reduced in region R, and as a result, the InP single-crystal substrate 1 can exhibit high resistance to fracture, spalling, and the like caused by the thermal variation. Accordingly, the InP single-crystal substrate 1 can achieve a lower fracture rate during the growth of an epitaxial layer on the main surface. For the InP single-crystal substrate according to the present embodiment, a mode is not excluded in which lattice points, each exhibiting a dislocation density classified as a second-order density, are also present outside the region R described above.However, in the InP single crystal substrate, the lattice points that were each determined with a dislocation density classified as a second-level density and are located outside the region R described above preferably constitute 20% or less of all lattice points that were each determined with a dislocation density classified as a second-level density. 3) Fourfold symmetry of the dislocation density distribution

[0078] The InP single-crystal substrate according to the present embodiment preferably satisfies the following relationships: 0.8×N_20 / N_0≤N_21 / N_1≤1.2×N_20 / N_0; 0.8×N_20 / N_0≤N_22 / N_2≤1.2×N_20 / N_0; 0.8×N_20 / N_0≤N_23 / N_3≤1.2×N_20 / N_0; 0.8×N_20 / N_0≤N_24 / N_4≤1.2×N_20 / N_0 and accordingly in a first division section, a second division section, a third division section and a fourth division section, which are given by virtual division by two orthogonal straight lines extending from the center point in four directions corresponding to a

[011] direction of the InP single crystal substrate.

[0079] N_20 is the total number of lattice points, each of which has a dislocation density classified as a second-order density.

[0080] N_0 is the total number of grid points that are subjected to the measurement of the dislocation density.

[0081] N_21, N_22, N_23 and N_24 are accordingly the total number of grid points, each of which has a dislocation density that is classified as second level in the first partition, in the second partition, in the third partition and in the fourth partition.

[0082] N_1, N_2, N_3, and N_4 represent the total number of grid points at which the dislocation density is measured in the first, second, third, and fourth partition sections, respectively. This allows for a lower fracture rate. The first partition section is used as an example in the following description.

[0083] Fig. Figure 6 is a clear diagram showing an area (e.g., the first division section) extracted from four areas (first division section, second division section, third division section, and fourth division section) created by virtual division of the area in Fig. The indium phosphide single-crystal substrate shown in section 4 is defined by two orthogonal straight lines that intersect at the center of the main surface. As shown in Fig. As shown in Figure 6, a first division section B1 is one of four areas defined by virtual division by two orthogonal straight lines extending from the center of the main surface in four directions, corresponding to a

[011] direction of the Fig. The 4 InP single-crystal substrates 1 shown correspond to the first partition section B1. The first partition section preferably satisfies a relationship: 0.8 × N_20 / N_0 ≤ N_21 / N_1 ≤ 1.2 × N_20 / N_0. That is, as can be seen from the comparison between Fig. 4 and Fig. As can be seen in Figure 6, the ratio of the total number of lattice points L2, each classified as second level, to the total number of lattice points in the first division section B1 (N_21 / N_1) is almost the same as the ratio of the total number of lattice points L2, each classified as second level, to the total number of lattice points in the main surface of the InP single-crystal substrate (N_20 / N_0). In particular, N_21 / N_1 is a value greater than or equal to 0.8 times and less than or equal to 1.2 times N_20 / N_0.

[0084] Furthermore, it is advantageous if the InP single-crystal substrate in the second, third, and fourth division sections exhibits a similar mode to the first division section B1. That is, the second division section preferably satisfies a relationship: 0.8 × N_20 / N_0 ≤ N_22 / N_2 ≤ 1.2 × N_20 / N_0; the third division section preferably satisfies a relationship: 0.8 × N_20 / N_0 ≤ N_23 / N_3 ≤ 1.2 × N_20 / N_0; and the fourth division section preferably satisfies a ratio of 0.8 × N_20 / N_0 ≤ N_24 / N_4 ≤ 1.2 × N_20 / N_0. In particular, each value N_21 / N_1, N_22 / N_2, N_23 / N_3 and N_24 / N_4 is preferably greater than or equal to 0.90 times and less than or equal to 1.07 times N_20 / N_0.

[0085] If, in the region R described above, lattice points are present, each exhibiting a dislocation density classified as level two, and the first, second, third, and fourth partition sections each possess the mode or properties described above in the InP single-crystal substrate according to the present embodiment, the dislocation density distribution on the main surface of the InP single-crystal substrate is expected to have quadruple symmetry. In this case, the stress exerted on the InP single-crystal substrate by thermal variations during the growth of an epitaxial layer on the main surface can be effectively reduced in region R, where the dislocation density distribution is quadruple symmetric. In this way, the single-crystal InP substrate can achieve a lower fracture rate. <Dotierstoff: Schwefel, Zinn, Eisen oder Zink, und Atomkonzentration>

[0086] The InP single-crystal substrate preferably contains one or more dopants from the group consisting of sulfur (S), tin (Sn), iron (Fe), and zinc (Zn). The atomic concentration of the dopants in the InP single-crystal substrate is preferably greater than or equal to 1.0 × 10⁻⁶. 17 cm -3 and less than or equal to 1.0 × 10 19 cm -3 This allows the InP single-crystal substrate containing such a dopant to achieve lower breakage rates. In particular, n-type (electron-donating) InP single-crystal substrates containing at least one of the elements S, Sn, and Zn can achieve lower breakage rates. Alternatively, semi-insulating InP single-crystal substrates containing Fe or that are undoped can exhibit a lower breakage rate. In particular, the inclusion of dopants in a concentration within the aforementioned range enables the provision of an InP single-crystal substrate that is preferred for the fabrication of electronic or optical devices, for example, because of the ease of fabricating an n-type electrode or the ease of laminating a light-emitting layer.

[0087] The InP single-crystal substrate can incorporate S, Sn, Fe, or Zn by adding these materials at a specific atomic concentration along with an indium phosphide bulk (hereinafter also referred to as the "InP bulk") as the starting material for growing an InP single crystal using a crucible method described later. The atomic concentration of the dopants is measured in each case by glow discharge mass spectrometry (GDMS). [Manufacturing process for an indium phosphide single crystal substrate]

[0088] Although no restriction should be imposed, the following manufacturing process is preferred as a manufacturing process for an indium phosphide single crystal for obtaining the InP single-crystal substrate described above, for example, with regard to good production yield. In particular, the manufacturing process for an indium phosphide single crystal (the manufacturing process for an InP single crystal) according to the present embodiment is a manufacturing process for an InP single crystal that can be produced using a vertical boat process.The manufacturing process comprises: providing a single-crystal growth apparatus comprising at least one cylindrical crucible and a heater arranged to surround an outer circumference of the crucible; placing a seed crystal in a lower part of the crucible and placing an indium phosphide bulk (InP bulk) over the seed crystal in the crucible; generating an indium phosphide melt (hereinafter also referred to as the "InP melt") by heating the crucible with the heater to melt the InP bulk and part of the seed crystal and to bring the InP melt and a remaining part of the seed crystal into contact; and obtaining an InP single crystal by growing a crystal on the remaining part of the seed crystal from the InP melt.

[0089] The heating element has a first heating area and a second heating area, which is located axially to the crucible and supports the first heating area. The first heating area has a first surface and a second surface. The second heating area has a third surface and a fourth surface. The third surface faces the first surface, which is located on the upper side of the axial direction within the first heating area. The fourth surface faces the second surface, which is located on the lower side of the axial direction within the first heating area. An outer circumference of the first heating area is enclosed by the second heating area. A first side surface, forming an inner circumference of the first heating area, lies in a cylindrical plane that encloses a second side surface, which forms an inner circumference of the second heating area.The first heating zone is capable of heating the crucible with a power output that differs from that of the second heating zone. The distance from the center of a radial direction of the crucible to the first and second side faces is greater than or equal to 60 mm and less than or equal to 65 mm, respectively.

[0090] Here, during the extraction of the InP single crystal in a plane of a first cross-section parallel to the axial direction and encompassing the center of the crucible's radial direction, the inner circumferential edges of the first, second, third, and fourth faces in the radial direction are defined as a first position, a second position, a third position, and a fourth position, respectively. A midpoint of the first and second positions in the axial direction is defined as a fifth position, and the temperatures at the third, fourth, and fifth positions are defined as a first temperature, a second temperature, and a third temperature, respectively. The heating process, using output in the first and second heating regions, generates a temperature distribution as shown below. More precisely, the heating process maintains: the third temperature is at a temperature that is lower than the first temperature and lower than the second temperature; a difference between the second temperature and the third temperature of 1°C or more and 2°C or less; furthermore, the heater generates: a temperature gradient of greater than or equal to 0.295°C / mm and less than or equal to 0.305°C / mm parallel to the axial direction in a range of greater than or equal to 50 mm and less than or equal to 65 mm below the fifth position parallel to the axial direction; a temperature gradient of greater than or equal to 0.235°C / mm and less than or equal to 0.245°C / mm parallel to the axial direction in a range of greater than or equal to 25 mm and less than 50 mm below the fifth position parallel to the axial direction; a temperature gradient of greater than or equal to 0.095°C / mm and less than or equal to 0.105°C / mm parallel to the axial direction in a range greater than or equal to 0 mm and less than 25 mm below the fifth position parallel to the axial direction; a temperature gradient of greater than or equal to 0.055°C / mm and less than or equal to 0.065°C / mm parallel to the axial direction in a region of more than 0 mm and less than or equal to 35 mm above the fifth position parallel to the axial direction; and a temperature gradient of greater than or equal to 0.035°C / mm and less than or equal to 0.045°C / mm parallel to the axial direction in a range of more than 35 mm and less than or equal to 85 mm above the fifth position parallel to the axial direction.

[0091] Furthermore, in the InP single-crystal production process, the crystal is grown by maintaining the position of an interface between the InP melt and the crystal on an inner circumferential surface of the crucible within a range greater than or equal to 43 mm and less than or equal to 45 mm below the fifth position, parallel to the axial direction. With these features, the InP single-crystal production process is capable of providing InP single-crystal substrates with reduced breakage rates.

[0092] With the aim of obtaining InP single-crystal substrates with reduced breakage rates, the present inventors have developed a characteristic method for growing an InP single crystal in a crucible of a single-crystal growth apparatus using a vertical boat or container method. In particular, the inventors conceived the idea of ​​growing the InP single crystal under a heat distribution characteristic of the radial direction of the crucible, whereby the position and shape of an interface between an InP single crystal and an InP melt in the crucible are strictly controlled. To realize this idea, the heating element, which is part of the single-crystal growth apparatus, was designed to have a first heating zone and a second heating zone, the power of which can each be adjusted independently.Furthermore, a setup was used in which the second heating zone surrounded the perimeter of the first heating zone, except for its inner perimeter. Additionally, the interface between a growing InP single crystal and an InP melt in the crucible was held at a specific distance parallel to the crucible's axial direction, positioned below a specific location within the first heating zone. As a result, an InP single-crystal ingot with a dislocation density distribution corresponding to the thermal distribution was obtained. Due to this thermally determined dislocation density distribution, the InP single-crystal substrates produced from the ingot exhibited high resistance to fractures, spalling, and similar defects caused by thermal fluctuations during the growth of an epitaxial layer on the main surface.In this way, the inventors have developed a manufacturing process for InP single crystals, which yields InP single crystal substrates with reduced breakage rates.

[0093] The fabrication process for an InP single crystal according to the present embodiment is a vertical boat or vessel method. Examples of vertical boat methods include a vertical Bridgeman (VB) process, a vertical temperature gradient freezing (VGF) process, and a hybrid process combining the VB and VGF methods. For the purpose of producing InP single-crystal substrates with the properties and high yield described above, it is preferable, for example, that the fabrication process includes a process that can be represented as a flowchart in [reference to a specific diagram or diagram]. Fig. 7 is shown. Fig. Figure 7 is a flowchart describing an example of the manufacturing process for an indium phosphide single crystal according to the present embodiment. In particular, the flowchart includes Fig. 7. An InP single-crystal fabrication process S100 and an InP single-crystal substrate fabrication process S200 for the fabrication of an InP single-crystal substrate. The InP single-crystal fabrication process S100 comprises the fabrication process for an InP single-crystal substrate in Fig. 7: Preparing or providing a single-crystal growth apparatus comprising at least one cylindrical crucible and a heater arranged to surround an outer circumference of the crucible (preparation step S110); placing a seed crystal on a bottom part of the crucible and placing an InP bulk above the seed crystal in the crucible (raw material loading step S120); generating an InP melt by melting the InP bulk and part of the seed crystal by heating the crucible with the heater and bringing the InP melt into contact with a remaining part of the seed crystal (raw material melting step S130); and obtaining an InP single crystal by growing a crystal on the remaining part of the seed crystal from the InP melt (InP single-crystal obtaining step S140).The preparation step S110, the raw material loading step S120, the raw material melting step S130, and the InP single-crystal recovery step S140 are performed in this order. The flowchart also includes [details omitted]. Fig. 7. The fabrication of an InP single-crystal substrate with a circular major surface from the InP single crystal is described as InP single-crystal substrate fabrication process S200. The fabrication process S200 for an InP single-crystal substrate comprises: cutting to obtain a disk-shaped InP single-crystal substrate precursor by cutting an InP single crystal; and grinding the outer circumference to obtain an InP single-crystal substrate with a circular major surface by grinding an outer circumference of the InP single-crystal substrate precursor. For example, when carrying out the fabrication process for an InP single crystal, a Fig. 8 single crystal growth device100 shown, which has a crucible 5 and a heater 7. Fig. Figure 8 is an illustrative cross-sectional diagram depicting a single-crystal growth apparatus used in the fabrication process for an indium phosphide single crystal according to the present embodiment, and the internal state of a crucible of the single-crystal growth apparatus during indium phosphide single-crystal production. The steps of the fabrication process for an InP single crystal are described below with reference to Fig. 7 and Fig. 8 described. (Deployment step or preparation step S110)

[0094] In the manufacturing process for an InP single-crystal substrate, a single-crystal growth device is prepared, comprising at least one cylindrical crucible and a heater arranged to surround an outer circumference of the crucible (preparation step S110). In preparation step S110, the single-crystal growth device 100 is prepared or provided as described below. As in Fig. As shown in Figure 8, the crucible 5 in the single-crystal growth device 100 is cylindrical and has a seed crystal holder 51 and a crystal growth part 52 connected to the seed crystal holder 51. The crystal growth part 52 further comprises a truncated cone section 52A and a straight body section 52B. The crystal growth part 51 is a region with a cylindrical cavity section having an opening on the side to be connected to the crystal growth part 52 and a bottom wall on the opposite side. The seed crystal holder 51 is capable of holding a seed crystal 8a in the cavity section. The truncated cone section 52A of the crystal growth part 52 is in the shape of a truncated cone and is connected to the seed crystal holder 51 on the side with a smaller diameter. The straight fuselage section 52B has a hollow cylindrical shape and is connected to the large diameter side of the truncated cone section 52A.The crystal growth element 52 serves to hold a solid InP bulk within the crucible 5. Furthermore, the crystal growth element 52 of the crucible 5 serves to grow an InP single crystal 81 by solidifying an InP melt 82, which is a raw material heated to a molten state. The angle of inclination between the truncated cone section 52A and the straight body section 52B in the crucible 5 is preferably 40° or less, and more preferably 20° or less. Various materials can be used for the crucible 5 that are stable at the temperature at which the InP bulk melts. For example, it is advantageous to use pyrolytic boron nitride (pBN) as the material for the crucible 5. The single-crystal growth device 100 can also include a crucible support table 6 for receiving the crucible 5. For example, silicon carbide can be used as a material for the crucible holding table 6.

[0095] The heater 7 is arranged to surround the outer circumference of the cylindrical crucible 5 described above. The heater 7 has a first heating area 71 and a second heating area 72, which extends along the axial direction of the crucible 5 and supports the first heating area 71. The first heating area 71 is capable of heating the crucible 5 with a power output that differs from the power output in the second heating area 72. Preferably, the second heating area 72 is multi-stage, with several sections arranged perpendicular to the axial direction of the crucible 5. This arrangement allows the power output of the heating element in the second heating area 72 to be controlled independently for each section. Furthermore, the power output of the heating element in the second heating area 72 can, for example, be slightly reduced upwards along the axial direction of the crucible 5.The first heating area 71 and the second heating area 72 can contain heating elements made of the same material or heating elements made of different materials. For example, the first heating area 71 and the second heating area 72 can each contain a heating element made of silicon carbide or a heating element made of an alloy such as a nickel-chromium alloy or an iron-chromium-aluminum alloy.

[0096] The first heating area 71 has a first surface 71a and a second surface 71b. The second heating area 72 has a third surface 72a and a fourth surface 72b. The third surface 72a faces the first surface 71a, which is located on the upper side of the axial direction in the first heating area 71. The fourth surface 72b faces the second surface 71b, which is located on the lower side of the axial direction in the first heating area 71. An outer circumference of the first heating area 71 is enclosed by the second heating area 72. A first side surface 71c, which forms an inner circumference of the first heating area 71, lies in a cylindrical plane that encloses a second side surface 72c, which forms an inner circumference of the second heating area 72. The distance from the center of the radial direction of the crucible 5 to the first side face 71c and to the second side face 72c is 60 mm or more and 65 mm or less, respectively.Preferably, each of the distances is greater than or equal to 61 mm and less than or equal to 64 mm. (Raw material loading step S120)

[0097] In step S120, a seed crystal 8a is placed in the lower part of the crucible 5, and an InP bulk is positioned above the seed crystal in the crucible 5. The purpose of the raw material loading step S120 is to place raw materials for growing an InP single crystal in the single-crystal growth device 100, which was prepared in the preparation step S110. In the raw material loading step S120, the seed crystal 8a (InP crystal) is first loaded into the cavity of the seed crystal-holding part 51 of the crucible 5. Any conventionally known method can be used for inserting the seed crystal 8a into the seed crystal-holding part. Here, the cross-sectional area of ​​the seed crystal 8a is preferably set to 15% or more of the cross-sectional area of ​​the straight body part 52B of the crucible 5, preferably to greater than or equal to 50% thereof.The mean dislocation density of the seed crystal 8a is preferably 5000 cm. -2 or less, and even more preferably 2000 cm -2 or less. The addition of a trace amount of impurity atoms (S, Sn, Fe, or Zn) to the seed crystal 8a is also preferred. Several lumps consisting of InP polycrystals are loaded and stacked as InP bulk bodies in the crystal growth section 52 (truncated cone section 52A and straight body section 52B) of the crucible 5. In some cases, a certain amount of impurity atoms (S, Sn, Fe, or Zn) can be added along with the InP bulk body. A conventionally known sealing agent (e.g., a solid sealing agent consisting of B₂O₃ (boron oxide)) can additionally be placed on the InP bulk body. (Raw material melting step S130)

[0098] Step S130 of raw material melting consists of generating an InP melt 82 by heating the crucible 5 with the heater 7 to melt the InP bulk and part of the seed crystal 8a, and to bring the InP melt 82 and the remainder of the seed crystal 8a into contact. The purpose of raw material melting step S130 is to enable an InP single crystal to begin crystal growth in the single-crystal growth device 100, into which raw materials (seed crystal 8a and an InP bulk) are placed. In raw material melting step S130, an electric current is first applied to the heater 7, thereby heating the crucible 5, into which the seed crystal 8a, a solid InP bulk, and a solid sealant have been placed. As a result, the solid sealant melts into a liquid sealant 9, and the InP bulk and part of the seed crystal 8a melt into an InP melt 82.The InP melt 82 and a remaining portion of the seed crystal 8a then come into contact at an interface I. The crucible 5 is then gradually moved downwards in the axial direction (towards the side of the portion 51 holding the seed crystal) against the heater 7. This creates a temperature gradient in the crucible 5 with lower temperatures on the side of the seed crystal 8a and higher temperatures on the side of the InP melt 82, allowing the InP single crystal 81 to grow on the remaining portion of the seed crystal 8a in the next step. The downward axial movement of the crucible 5 is preferably 10 mm / hour or less, and more preferably 5 mm / hour or less. Furthermore, it is advantageous to move the crucible 5 downwards in the axial direction by rotating it about its axis at approximately 5 rpm. (InP single crystal recovery step S140)

[0099] Step S140 for obtaining an InP single crystal consists of producing an InP single crystal 81 by growing a crystal (InP single crystal 81) on the remainder of the seed crystal 8a from the InP melt 82. The purpose of step S140 for obtaining an InP single crystal is to grow the InP single crystal 81 under a heat distribution characteristic of the radial direction of the crucible 5. To achieve this purpose, in step S140 for obtaining an InP single crystal, a temperature atmosphere, as shown below, is created by independently controlling the output powers in the first heating area 71 and in the second heating area 72, which constitute the heater 7, and the InP single crystal 81 is grown under this temperature atmosphere.Furthermore, in step S140 for the recovery of InP single crystals, the InP single crystal 81 is grown by maintaining the position of the interface I between the InP melt 82 and the InP single crystal 81 on an inner circumferential surface of the crucible 5 in a range of 43 mm or more and 45 mm or less below a fifth position 71f parallel to the axial direction of the crucible 5.

[0100] Here, in a plane of a first cross-section that runs parallel to the axial direction of the crucible 5 and includes the midpoint of the radial direction of the crucible 5, the inner circumferential edges of the first surface 71a, the second surface 71b, the third surface 72a, and the fourth surface 72b are defined in the radial direction as a first position 71d, a second position 71e, a third position 72d, and a fourth position 72e, respectively. A midpoint of the first position 71d and the second position 71e in the axial direction is defined as a fifth position 71f, and the temperatures at the third position 72d, the fourth position 72e, and the fifth position 71f are defined as a first temperature, a second temperature, and a third temperature, respectively. The cross-sectional representation of Fig. The cross-section shown in Figure 8 corresponds to the "first cross-section". In this case, the heater 7, using the output powers in the first heating area 71 and in the second heating area 72, maintains the third temperature in the InP single-crystal recovery step S140 at a temperature lower than both the first and second temperatures. The heater 7 maintains the difference between the second and third temperatures at a level greater than or equal to 1°C and less than or equal to 2°C.

[0101] The heater 7 forms a temperature gradient of greater than or equal to 0.295°C / mm and less than or equal to 0.305°C / mm parallel to the axial direction of the crucible 5 in a region of greater than or equal to 50 mm and less than or equal to 65 mm below the fifth position 71f parallel to the axial direction of the crucible 5. Preferably, the temperature gradient is greater than or equal to 0.298°C / mm and less than or equal to 0.302°C / mm.

[0102] The heater 7 forms a temperature gradient of greater than or equal to 0.235°C / mm and less than or equal to 0.245°C / mm parallel to the axial direction of the crucible 5 in a region that is greater than or equal to 25 mm and less than 50 mm below the fifth position 71f parallel to the axial direction of the crucible 5. Preferably, the temperature gradient is greater than or equal to 0.238°C / mm and less than or equal to 0.242°C / mm.

[0103] The heater 7 forms a temperature gradient of greater than or equal to 0.095°C / mm and less than or equal to 0.105°C / mm parallel to the axial direction of the crucible 5 in a region of 0 mm or more and less than 25 mm below the fifth position 71f parallel to the axial direction of the crucible 5. Preferably, the temperature gradient is greater than or equal to 0.098°C / mm and less than or equal to 0.102°C / mm.

[0104] The heater 7 forms a temperature gradient of greater than or equal to 0.055°C / mm and less than or equal to 0.065°C / mm parallel to the axial direction of the crucible 5 in a region of more than 0 mm and 35 mm or less above the fifth position 71f parallel to the axial direction of the crucible 5. Preferably, the temperature gradient is greater than or equal to 0.058°C / mm and less than or equal to 0.062°C / mm.

[0105] The heater 7 forms a temperature gradient of greater than or equal to 0.035°C / mm and less than or equal to 0.045°C / mm parallel to the axial direction of the crucible 5 in a region of more than 35 mm and 85 mm or less above the fifth position 71f parallel to the axial direction of the crucible 5. Preferably, the temperature gradient is greater than or equal to 0.038°C / mm and less than or equal to 0.042°C / mm.

[0106] Preferably, the InP single crystal 81 is grown in step S140 of the InP single crystal growth process under the temperature atmosphere described above in order to provide the interface I between the InP melt 82 and the InP single crystal 81 in the crucible 5 with a shape (cross-sectional shape) that reflects the characteristic heat distribution in the radial direction of the crucible 5, as shown in Fig. 9 shown. Fig. Figure 9 is a clear diagram showing a specific part (interface shape) of Fig. Figure 8 shows. In particular, it is preferred that the cross-sectional shape of the interface I, which appears in the first cross-section as a shape reflecting the heat distribution characteristic in the radial direction of the crucible 5, at least partially comprises a curved line segment, as shown in Figure 8. Fig. Figure 9 illustrates this. In particular, it is preferred that the curved line segment has a local maximum point Q1 in the middle of the curved line segment and two local minimum points Q2 on either side of the local maximum point Q1 in the radial direction of the crucible 5. Furthermore, it is advantageous that the positions of the ends E of the curved line segment in the axial direction of the crucible 5 are higher than the local minimum points Q2. The positions of the ends E of the curved line segment correspond to the position of the interface I between the InP melt 82 and the InP single crystal 81 on an inner circumferential surface of the crucible 5.

[0107] Furthermore, the curved line segment preferably fulfills the following relationships: R / √2−0.1R≤D1≤R / √2+0.1R; 0.1D1≤D2; and 0,1(R−D1)≤D3.

[0108] R stands for the bore radius of the crucible 5 and has the unit mm. As in Fig. As shown in 9, D1, D2 and D3 denote the following distances.

[0109] D1 is a distance between a point corresponding to the local maximum point Q1 on a first line segment and a point corresponding to one of the local minimum points Q2 on the first line segment, and has the unit mm, where the first line segment appears when the curved line part is virtually projected onto a straight line parallel to the radial direction of the crucible 5.

[0110] D2 is a distance between a point corresponding to a local maximum point Q1 on a second line segment and a point corresponding to one of the local minimum points Q2 on the second line segment, and has the unit mm, where the second line segment appears when the curved part of the line is virtually projected onto a straight line parallel to the axial direction of the crucible 5.

[0111] D3 is a distance between a point corresponding to a first local minimum point Q21 on the second line segment and a point corresponding to a first end E1 on the second line segment, and has the unit mm, where the first local minimum point Q21 is one of two local minimum points Q2, and the first end E1 is one end of the two ends E that is closer to the first local minimum point Q21.

[0112] The curved line segment that satisfies the relations R / √2 - 0.1 R ≤ D1 ≤ R / √2 + 0.1 R, 0.1 D1 ≤ D2 and 0.1 (R - D1) ≤ D3 allows lattice points, each of which is to be determined such that they have a dislocation density classified as level two, to be located in the Fig. The region R shown in Figure 5 is concentrated in an InP single-crystal substrate consisting of the InP single crystal produced by the fabrication process. Specifically, if the relationship 0.1 D1 ≤ D2 is satisfied, dislocations present in a central part of the radial direction of the InP single crystal can be induced to move into region R of the InP single-crystal substrate in the InP single-crystal acquisition step S140. Furthermore, if the relationship 0.1 (R - D1) ≤ D3 is satisfied, dislocations present in an outer marginal part of the radial direction of the InP single crystal can be induced to move into region R of the InP single-crystal substrate in the InP single-crystal acquisition step S140.If the relationship R / √2 - 0.1 R ≤ D1 ≤ R / √2 + 0.1 R is satisfied, dislocations moving from a central part and an outer peripheral part of the radial direction of the InP single crystal into the region R can be retained in the InP single crystal detection step S140 in the region R.

[0113] In this way, an InP single-crystal block 81 can be grown under a heat distribution characteristic of the radial direction of the crucible 5 in the InP single-crystal acquisition step S140. In step S140 for obtaining InP single crystals, the crucible 5 can be moved continuously downwards along the axial direction against the heater 7, whereby the position of the interface I is raised towards the side of the liquid sealant 9 in order to solidify the InP melt 82 and thereby allow the InP single crystal 81 to grow upwards along the axial direction of the crucible 5. The growth of the InP single crystal 81 is continued until the solidification of the InP melt 82, which remains in the crystal-forming part 52 of the crucible 5, is complete.

[0114] For the InP single crystal 81 obtained by the fabrication process, the cross-sectional shape of the interface I between the InP melt 82 and the InP single crystal 81, which was formed in step S140 for obtaining the InP single crystal, can be verified using the following procedure. First, an InP single crystal 81 obtained by the fabrication process is cut in the direction perpendicular to the growth direction to obtain a disk-shaped indium phosphide wafer (hereinafter also referred to as the "InP wafer") with a thickness of 5 to 10 mm. The InP wafer is then cut parallel to the growth direction of the InP single crystal, including the center of the radial direction of the InP wafer, so that a rectangular cross-section is formed whose length corresponds to the diameter of the InP wafer and whose width corresponds to the thickness of the InP wafer.Furthermore, the rectangular cross-section is etched for 1 hour using an etching solution prepared with 100 g of chromium oxide, 16 ml of hydrofluoric acid, and 544 g of pure water, and a known lamp (power: 500 W). This produces a striped pattern on the rectangular cross-section. Each line forming the striped pattern corresponds to the cross-sectional shape of the interface I between the InP melt 82 and the InP single crystal 81, which was formed in step S140 of the InP single crystal growth process. Accordingly, the cross-sectional shape of the interface can be verified by viewing the striped pattern with an optical microscope as described above (e.g., product name: “ECLIPSE® ME600”, manufactured by Nikon Corporation). In this way, it can be confirmed, for example, whether an observed InP single crystal has grown with an interface whose shape reflects a heat distribution characteristic of the radial direction of the crucible, as in [reference missing]. Fig. 9 shown. <Funktionen und Wirkungen>

[0115] An InP single crystal for the production of InP single-crystal substrates with reduced fracture rates can be obtained by carrying out the steps described above. In particular, the production method for an InP single crystal according to the present embodiment allows the InP single crystal to grow under a heat distribution characteristic of the radial direction of the crucible, which is reflected in the cross-sectional shape of an interface that includes the curved line portion described above in the InP single-crystal production process. When InP single-crystal substrates are produced from an ingot of an InP single crystal obtained by the method, and an epitaxial layer has grown on the main surfaces of the substrates, the substrates successfully achieve a reduced fracture rate.

[0116] In the manufacturing process, the growth direction of the InP single crystal is preferably the <100> -direction. Furthermore, when preparing an InP single-crystal substrate from an ingot of the InP single crystal, it is preferred to cut the InP single crystal only along the {100} plane as the main surface in order to obtain a subsequently described InP single-crystal substrate precursor. [Manufacturing process for indium phosphide single crystal substrate]<InP-Einkristall-Substrat-Herstellungsverfahren S200>

[0117] The fabrication process for an InP single-crystal substrate according to the present embodiment comprises processing an InP single crystal obtained by the fabrication process for an InP single crystal to obtain an InP3 single-crystal substrate with a circular main face. As described in Fig. As shown in Figure 7, the fabrication process for an InP single-crystal substrate comprises the InP single-crystal substrate fabrication process S200. Specifically, the fabrication process S200 for an InP single-crystal substrate includes: cutting an InP single crystal to obtain a disk-shaped precursor of an InP single-crystal substrate; and grinding the outer circumference to obtain an InP single-crystal substrate with a circular major surface by grinding the outer circumference of the InP single-crystal substrate precursor. The fabrication process S200 for an InP single-crystal substrate includes cutting, grinding the outer circumference, and optional polishing, each described below, and an InP single-crystal substrate can be obtained by performing these steps in this order.

[0118] In the cutting process, an ingot consisting of an InP single crystal, removed from the crucible, is sliced ​​into wafers to obtain a wafer of a specific thickness, thus creating a disc-shaped InP single-crystal substrate precursor. Subsequent circumferential grinding involves grinding the outer perimeter of the InP single-crystal substrate precursor to obtain an InP single-crystal substrate with a circular main surface. Any conventional known cutting and circumferential grinding process can be used for both. Additional polishing involves high-gloss polishing of the main surface. Any conventional known polishing process can be used for this. Polishing can achieve a surface roughness (Ra) of, for example, 1 nm or less, as specified in JIS B 0681-2: 2018, on the main surface of the InP single-crystal substrate. Examples

[0119] The present disclosure is described in more detail below by means of examples, although the present disclosure is not limited thereto. In the present examples, InP single-crystal substrates were grown using a single-crystal growth device according to Fig. 8 in accordance with the in Fig. The process was carried out as shown in the flowchart shown in Figure 7. In the following description, samples 11 to 13 are examples, and samples 101 and 102 are comparison examples. [Production of InP single crystal substrates]<Beispiel 11> (InP single crystal fabrication process S100)1) Provisioning step S110

[0120] First, a single-crystal growth device 100, as described in Fig. 8 shown, manufactured, or provided. In this single-crystal growth device 100, the inner diameter of the straight body section 52B of the crucible 5 was 75 mm. The angle of inclination from the truncated cone section 52A to the straight body section 52B in the crucible 5 was 20°. The distances from the center of the radial direction of the crucible 5 to the first side surface 71c and to the second side surface 72c of the first heating area 71, which are part of the heating element 7, were each 63 mm. 2) Raw material loading step S120

[0121] A seed crystal 8a consisting of InP, prepared according to a conventional known method, was inserted into the seed crystal-holding part 51 of the crucible 5. The cross-sectional area of ​​this seed crystal 8a was 50% of the cross-sectional area of ​​the straight body part 52B of the crucible 5. A trace amount of sulfur (S) was added to the seed crystal 8a as an impurity. Several lumps consisting of InP polycrystals were loaded and stacked as InP bulk bodies into the crystal growth part 52 (truncated cone part 52A and straight body part 52B) of the crucible 5. A trace amount of S was added to the crucible 5 such that the atomic concentration of the dopant in the InP melt 82 at the end face of the straight body part 52B, as described later, was 2.5 × 10⁻⁵. 18 cm -3 achieved. Additionally, a solid sealant consisting of boron oxide (B2O3) was applied to the InP volume body. 3) Raw material melting step S130

[0122] Electric current was applied to the heater 7, heating the crucible 5 to convert the solid sealant into liquid sealant 9 and to melt the InP bulk and part of the seed crystal 8a in the crucible 5, forming InP melt 82. Furthermore, the InP melt 82 and a remaining portion of the seed crystal 8a were brought into contact. Subsequently, the crucible 5 was moved axially downwards (towards the side of the portion 51 containing the seed crystal) against the heater 7 to initiate the crystal growth of the InP single crystal 81. The downward movement of the crucible 5 along the axial direction was 3 mm / hour. During the continued downward movement of the crucible 5 along the axial direction, it was rotated about its axis at 5 rpm. 4) InP single crystal recovery step S140

[0123] Next, a temperature atmosphere, as shown below, was created by independently controlling the output powers in the first heating area 71 and in the second heating area 72, which are part of the heater 7, and the InP single crystal 81 was grown under the temperature atmosphere. At this time, the position of the interface I between the InP melt 82 and the InP single crystal 81 on an inner circumferential surface of the crucible 5 was maintained at a position 44 mm below the fifth position 71f parallel to the axial direction of the crucible 5.

[0124] The temperature atmosphere was as follows: First temperature: 954° C; second temperature: 950° C; third temperature: 953° C; Temperature gradient along the axial direction of the crucible 5 in the region of 50 mm or more and 65 mm or less below the fifth position 71f, parallel to the axial direction of the crucible 5: 0.301°C / mm; Temperature gradient along the axial direction of the crucible 5 in the region of 25 mm or more and less than 50 mm below the fifth position 71f, parallel to the axial direction of the crucible 5: 0.242°C / mm; Temperature gradient along the axial direction of the crucible 5 in the region of 0 mm or more and less than 25 mm below the fifth position 71f parallel to the axial direction of the crucible 5: 0.101 °C / mm; Temperature gradient along the axial direction of crucible 5 in the region of more than 0 mm and 35 mm or less above the fifth position 71f parallel to the axial direction of crucible 5: 0.059°C / mm; and Temperature gradient along the axial direction of the crucible 5 in the region of more than 35 mm and 85 mm or less above the fifth position 71f parallel to the axial direction of the crucible 5: 0.038°C / mm.

[0125] The crucible 5 was continuously moved downwards in the axial direction against the heater 7 to raise the interface I between the InP single crystal 81 and the InP melt 82 in the axial direction of the crucible 5, causing the InP single crystal 81 to grow upwards in the axial direction of the crucible 5. This was continued until the solidification of the InP melt 82 remaining in the crucible 5 was complete. The InP single crystal 81 was thus obtained. Subsequently, the InP single crystal 81 was removed from the crucible 5 using a known method. In this way, an InP single crystal ingot of sample 11 with a diameter of 75 mm was obtained.

[0126] The procedure described above was then carried out on the InP single-crystal ingot of sample 11 to examine the cross-sectional shape of the interface I between the InP melt 82 and the InP single crystal 81, which had been formed in step S140 for the production of the InP single crystal. Specifically, the InP single-crystal ingot was cut in the direction perpendicular to the growth direction to obtain a disk-shaped InP wafer with a thickness of 5 to 10 mm. Subsequently, a rectangular cross-section with a length equal to the diameter of the InP wafer and a width equal to the thickness of the InP wafer was prepared from the InP wafer, and the rectangular cross-section was further etched under the conditions described above using an etching solution and a lamp, resulting in a measurement specimen with a striped pattern on its surface.In addition, the stripe pattern was examined using a light microscope to identify the cross-sectional shape of interface I.

[0127] The cross-sectional shape of the interface I had a curved line segment, as in Fig. Figure 9 shows a local maximum point Q1 positioned in the middle of the curved line segment and two local minimum points Q2 positioned on either side of local maximum point Q1 in the radial direction of crucible 5. Furthermore, the positions of the ends E of the curved line segment were higher than the local minimum points Q2 in the axial direction of crucible 5. Additionally, D1 to D3 were as follows: D1: 26.3 mm; D2: 3.1 mm; and D3: 1.7 mm.

[0128] Here, D1 denotes a distance between a point corresponding to the local maximum point Q1 on a first line segment and a point corresponding to one of the local minimum points Q2 on the first line segment, the first line segment appearing when the curved line segment is virtually projected onto a straight line parallel to the radial direction of the crucible 5. D2 denotes a distance between a point corresponding to the local maximum point Q1 on a second line segment and a point corresponding to one of the local minimum points Q2 on the second line segment, the second line segment appearing when the curved line segment is virtually projected onto a straight line parallel to the axial direction of the crucible 5.D3 denotes a distance between a point corresponding to the first local minimum point Q21 on the second line segment and a point corresponding to the first end E1 on the second line segment, where the first local minimum point Q21 is one of two local minimum points Q2 and the first end E1 is one end of the two ends E that is closer to the first local minimum point Q21.

[0129] The cross-sectional shape of the interface I, which results from the ingot of the InP single crystal of sample 11, therefore satisfies all relationships: R / √2−0.1R≤D1≤R / √2+0.1R; 0.1D1≤D2; and 0,1(R−D1)≤D3.

[0130] The bore radius R of the crucible 5 was 37.5 mm. (InP single crystal substrate manufacturing process S200)

[0131] Using a conventionally known cutting method and a method for grinding the outer circumference, the ingot of the InP single crystal taken from crucible 5 was cut to obtain an InP single crystal substrate precursor, and an outer circumference of the InP single crystal substrate precursor was ground to produce an InP single crystal substrate with a circular main surface. In this way, an InP single crystal substrate of sample 11 with a diameter of 75 mm and a thickness of 900 µm was obtained. <Probe 12>

[0132] An InP single-crystal substrate of sample 12 with a diameter of 75 mm and a thickness of 910 µm was prepared in the same manner as for sample 11, except that the second temperature in the temperature atmosphere to be generated in the InP single-crystal recovery step S140 was changed to 949°C. The cross-sectional shape of interface I, identified from the InP single crystal of sample 12 using the method described above, had a curved line segment, as shown in Fig. Figure 9 shows a local maximum point Q1 positioned in the middle of the curved line segment and two local minimum points Q2 positioned accordingly on either side of local maximum point Q1 in the radial direction of crucible 5. Furthermore, the positions of the ends E of the curved line segment in the axial direction of crucible 5 were higher than the local minimum points Q2. Additionally, D1 to D3 were as follows: D1: 23.4 mm; D2: 3.2 mm ; and D3: 1.6 mm.

[0133] The cross-sectional shape of the interface I, which results from the ingot of the InP single crystal of sample 12, therefore satisfies all relationships: R / √2−0.1R≤D1≤R / √2+0.1R; 0.1D1≤D2; and 0,1(R−D1)≤D3. <Probe 13>

[0134] An InP single-crystal substrate of sample 13 with a diameter of 75 mm and a thickness of 900 µm was prepared in the same manner as for sample 11, except that the initial temperature in the temperature atmosphere to be generated in the InP single-crystal recovery step S140 was changed to 953°C. The cross-sectional shape of interface I, identified from the InP single crystal of sample 13 using the method described above, had a curved line portion, as shown in Fig. Figure 9 shows a local maximum point Q1 positioned in the middle of the curved line segment and two local minimum points Q2 positioned on either side of local maximum point Q1 in the radial direction of crucible 5. Furthermore, the positions of the ends E of the curved line segment in the axial direction of crucible 5 were higher than the local minimum points Q2. Additionally, D1 to D3 were as follows: D1: 26.3 mm; D2: 2.9 mm; and D3: 1.5 mm.

[0135] The cross-sectional shape of the interface I, which results from the ingot of the InP single crystal of sample 12, therefore satisfies all relationships: R / √2−0.1R≤D1≤R / √2+0.1R; 0.1D1≤D2; and 0,1(R−D1)≤D3. <Probe 101>

[0136] An InP single-crystal substrate of sample 101 with a diameter of 75 mm and a thickness of 910 µm was obtained in the same manner as for sample 11, except that the first, second, and third temperatures in the temperature atmosphere to be generated in the InP single-crystal recovery step S140 were each changed to 954°C. The cross-sectional shape of the interface identified from the ingot of the InP single crystal of sample 101 using the method described above had a curved line segment, but only one local maximum point in the middle of the curved line segment in the radial direction of the crucible 5. <Probe 102>

[0137] An InP single-crystal substrate of sample 102 with a diameter of 75 mm and a thickness of 920 µm was obtained in the same manner as for sample 11, except that the first, second, and third temperatures in the temperature atmosphere to be generated in the InP single-crystal recovery step S140 were each changed to 953°C. The cross-sectional shape of the interface, identified from the ingot of the InP single crystal of sample 102 using the method described above, had a curved line portion, but only one local maximum point in the middle of the curved line portion in the radial direction of the crucible 5. [Evaluation]<Versetzungsdichte bzw. Dislokationsdichte>

[0138] For each of the main surfaces of the InP single-crystal substrates of samples 11 to 13, 101, and 102, the dislocation densities at the respective lattice points were measured using the method described above. From a set consisting of the dislocation densities measured at the respective lattice points, a first total area mean was determined as the mean of the set, and a first total area standard deviation was determined as the standard deviation of the set. Furthermore, the dislocation densities measured at the respective grid points were classified as first-order, second-order, and third-order densities based on the aspects described above. It was then determined whether the lattice points exhibiting a second-order dislocation density were in the Fig. The area R shown in the diagram was present in 5. Furthermore, the ratio between a second mean (mean of a subset consisting of dislocation densities classified as second-order density) and a first mean (mean of a subset consisting of dislocation densities classified as first-order density) (second mean / first mean) was determined. These results are presented in Table 1.

[0139] Furthermore, each of the main surfaces of the InP single crystal substrates from sample 11 to sample 13, sample 101 and sample 102 was divided by two orthogonal straight lines extending from the center point in four directions corresponding to a

[011] direction of the InP single crystal to define a first division section, a second division section, a third division section and a fourth division section, and the ratio of the total number of lattice points exhibiting a dislocation density classified as second-order density to the total number of lattice points subjected to dislocation density measurement (N_2x / N_x) was determined in each division section.Subsequently, the ratio of the total number of lattice points exhibiting a dislocation density classified as second-order on the main surface to the total number of lattice points subjected to a measurement of dislocation densities on the main surface (N_20 / N_0) was also determined. From these results, the ratio [(N_2x / N_x) / (N_20 / N_0)] for determining whether the InP single-crystal substrate is quadruply symmetric was calculated. The results are presented in Table 1. For "Second mean / first mean" in Table 1, this was determined in the first, second, third, and fourth partition sections described above, and the maximum (Max), minimum (Min), and mean (Ave) are given. In Table 1, "random" means that the lattice points for which a second-order dislocation density was determined were scattered across the main surface, independent of region R. <prozessausbeute>

[0140] Using a special layer-forming furnace, an epitaxial layer 1.0 µm thick was formed on each of the main surfaces of the InP single-crystal substrates of samples 11 to 13, sample 101, and sample 102 via a metal-organic vapor deposition (MOVPE) process. The InP single-crystal substrates on which the epitaxial layers had formed were then cooled to room temperature in the furnace and subsequently removed. At this point, the number of broken substrates was divided by the number of substrates used for this evaluation, and the result was expressed as a percentage to determine the breakage rate. The breakage rate was then subtracted from 100% to determine the process yield (%). The results are presented in Table 1. [Table 1] Table 1 Sample 11 Sample 12 Sample 13 Sample 101 Sample 102 Diameter [mm] 75 75 75 75 75 Dopant concentration [cm³] -3 ] 2,0 × 10 18 2,0 × 10 18 2,0 × 10 18 2,0 × 10 18 2,0 × 10 18 First total area mean [cm²] -2 ] 98,8 125,7 163,6 13,6 318,0 Positions of grid points, each exhibiting a dislocation density of level two in the areaR in the areaR in the areaR randomly randomly Second mean / first mean Max 5,1 9,0 5,0 4,0 10,9 Min 4,3 5,7 4,4 3,2 8,6 Ave 4,7 7,1 4,7 3,7 10,4 (N_2x / N_x) / (N_20 / N_0) (*) Max 1,01 1,05 1,07 1,28 1,27 Min 0,99 0,91 0,90 0,77 0,76 Process yield [%] 94 96 93 80 78

[0141] (*) : X is an integer from 1 to 4. N_21, N_22, N_23, and N_24 denote the total number of grid points for which a dislocation density was determined, classified as a second-order density in the first, second, third, and fourth divisions, respectively. N_1, N_2, N_3, and N_4 denote the total number of grid points for which a dislocation density was measured in the first, second, third, and fourth divisions, respectively. N_20 denotes the total number of grid points for which a dislocation density was determined, classified as a second-order density in the main surface. N_0 denotes the total number of grid points for which a dislocation density was measured in the main surface. [Discussion]

[0142] According to Table 1, each of the InP single-crystal substrates of the samples contained 11 to 13 lattice points, for which a dislocation density classified as second-order density was determined, in a region between an outline or perimeter of the first square region and an outline of the second square region (see the in Fig. 5 (area R shown). Furthermore, the ratio of a second mean (mean of a subset of dislocation densities classified as second-level density) to a first mean (mean of a subset of dislocation densities classified as first-level density) (second mean / first mean) was in the range of 4.0 to 10.0 times. This resulted in a process yield of more than 90%. In contrast, in each of the InP single-crystal substrates of sample 101 and sample 102, random lattice points were present on the main surface, each exhibiting a dislocation density assigned to the second level.Furthermore, the ratio between a second mean (mean of a subset of dislocation densities classified as second-level density) and a first mean (mean of a subset of dislocation densities classified as first-level density) (second mean / first mean) was outside the range of 4.0 to 10.0 times. This resulted in a process yield of 80% or less. Therefore, it is assumed that the InP single-crystal substrates of samples 11 to 13 exhibited lower breakage rates than the InP single-crystal substrates of samples 101 and 102.

[0143] Although the embodiments and examples of the present disclosure are as described above, it was planned from the outset to combine the features of the embodiments and examples described above in a suitable manner.

[0144] The embodiments and examples disclosed herein are in every respect only examples and should be interpreted as non-limiting examples. The scope of the present invention is not represented by the embodiments and examples mentioned above, but by the claims, and is intended to include all modifications within the meaning and scope that correspond to the claims. List of reference numerals

[0145] 1 Indium phosphide single crystal substrate (InP single crystal substrate); 11 Main surface; G Square lattice; O Center point; P Lattice point; L1 Lattice point whose dislocation density is classified as first-order density; L2 Lattice point whose dislocation density is classified as second-order density; L3 Lattice point whose dislocation density is classified as third-order density; M1 First line segment; M2 Second line segment; S1 First square region; S2 Second square region; F1 Outline of the first square region; F2 Outline of the second square region; R Region; B1 First partition section; S100 InP single crystal fabrication process; S110 Preparation step; S120 Raw material loading step; S130 Raw material melting stepStep of melting raw material; S140 Step of InP single crystal growth; S200 InP single crystal substrate fabrication process; 100 Single crystal growth device; 5 Crucible; 51 Seed crystal holder; 52 Crystal growth part; 52A Truncated cone part; 52B Straight body part; 6 Crucible holding table; 7 Heater; 71 First heating area; 71a First face; 71b Second face; 71c First side face; 71d First position; 71e Second position; 71f Fifth position; 72 Second heating area; 72a Third face; 72b Fourth face; 72c Second side face; 72d Third position; 72e Fourth position; 8a Seed crystal; 81 Indium phosphide single crystal (InP single crystal); 82 Indium phosphide melt (InP melt); 9 Liquid sealant; I Interface; Q1 Local maximum point; Q2 Local minimum point; Q21 First local minimum point; E End; E1 First end. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 06-227898

[0002] WO 2005 / 106083

[0002] WO 2004 / 106597

[0002] Cited non-patent literature

[0000] JIS B 0681-2: 2018

[0118] < / prozessausbeute> < / durchmesser>

Claims

[1] An indium phosphide single crystal substrate with a circular main face, wherein the main surface is a (100) plane of an indium phosphide single crystal, which is part of the indium phosphide single crystal substrate, the main surface is virtually divided by a square grid with a grid spacing of 1 mm, the square grid is composed of several grid points that lie along a first direction and a second direction that is orthogonal to the first direction, a set consisting of dislocation densities measured at the respective grid points, having a first total area mean as the mean of the set and a first total area standard deviation as the standard deviation of the set, and each of the dislocation densities being classified as a first-level, second-level or third-level density, the grid points, for which a dislocation density is determined that is classified as a second-order density, lie in a region between the outline of a first square region and the outline of a second square region, and a second mean, as the mean of a subset consisting of dislocation densities each classified as second-order density, is greater than or equal to 4.0 times and less than or equal to 10.0 times a first mean, as the mean of a subset consisting of dislocation densities each classified as first-order density, the dislocation densities, each classified as first-order density, lie in a range greater than or equal to 0 cm -2 and is smaller than X0 the dislocation densities, each classified as second-order density, lie within a range greater than or equal to X0 and less than or equal to X1, the dislocation densities, each classified as third-order density, lie in a range greater than X1, X0 equals 1 / a, the relationship X0 > 0 is satisfied, and the unit is cm. -2 has, a in 1 / a by approximating a frequency distribution of the set in a histogram with an ordinate showing the cumulative relative frequencies as y and an abscissa showing the class values ​​as x, with the expression I shown below, X1 is a value that results from the sum of the first total area mean and a value of the first total area standard deviation multiplied by 3, which satisfies the relationship X1 > X0 and has the unit cm. -2 has, x is a minimum value in each section of the histogram, where the width of each section is a quotient of X1 divided by 100 and the unit is cm. -2 has, and y is a dimensionless number, the first square area has a square shape centered on a midpoint of the main area, the first square region has vertices as endpoints of first line segments of identical length, which extend from the center in four directions corresponding to a [011] direction of the indium phosphide single crystal, the length of each first line segment is 70% of the length of a radius of the indium phosphide single crystal substrate, the second square area has a square shape centered on the midpoint, the second square region has vertices as endpoints of second line segments of identical length extending from the center in four directions corresponding to a [011] direction of the indium phosphide single crystal, and The length of each second line segment is 130% of the length of the radius of the indium phosphide single crystal substrate: y=(1−b)×{1−exp(−ax)}+b where a satisfies the relation a > 0 and the unit cm 2 has, and b is a dimensionless number that satisfies the relation 0 ≤ b < 1. [2] The indium phosphide single crystal substrate according to claim 1, wherein the indium phosphide single crystal substrate satisfies the following relationships: 0.8×N_20 / N_0≤N_21 / N_1≤1.2×N_20 / N_0; 0.8×N_20 / N_0≤N_22 / N_2≤1.2×N_20 / N_0; 0.8×N_20 / N_0≤N_22 / N_2≤1.2×N_20 / N_0; and 0.8×N_20 / N_0≤N_24 / N_4≤1.2×N_20 / N_0 in a first partition section, a second partition section, a third partition section and a fourth partition section, which are given by virtual subdivision by two orthogonal straight lines extending from the center point in four directions corresponding to a [011] direction of the indium phosphide single crystal, wherein N_20 is the total number of lattice points, each of which has a dislocation density classified as second-order density, N_0 is the total number of lattice points that are subjected to a measurement of dislocation density, N_21, N_22, N_23 and N_24 are corresponding total numbers of lattice points, each of which is determined to have a dislocation density that is classified accordingly as second-order density in the first partition, in the second partition, in the third partition and in the fourth partition, and N_1, N_2, N_3 and N_4 are the total number of grid points that are subject to the measurement of the dislocation density in the first division section, in the second division section, in the third division section and in the fourth division section. [3] An indium phosphide single crystal substrate according to claim 2, wherein the second mean is greater than or equal to 4.3 times and less than or equal to 9.0 times the first mean, and Relationships: 0.90×N_20 / N_0≤N_21 / N_1≤1.07×N_20 / N_0; 0.90×N_20 / N_0≤N_22 / N_2≤1.07×N_20 / N_0; 0.90×N_20 / N_0≤N_23 / N_3≤1.07×N_20 / N_0; 0.90×N_20 / N_0≤N_24 / N_4≤1.07×N_20 / N_0 and are fulfilled in the first division section, the second division section, the third division section and the fourth division section. [4] An indium phosphide single crystal substrate according to any one of claims 1 to 3, wherein the indium phosphide single crystal substrate has a diameter greater than or equal to 75 mm and less than or equal to 76.5 mm. [5] An indium phosphide single-crystal substrate according to any one of claims 1 to 4, wherein the indium phosphide single-crystal substrate contains one or more dopants selected from the group consisting of sulfur, tin, iron and zinc, and an atomic concentration of the dopants in the indium phosphide single-crystal substrate greater than or equal to 1.0 × 10 17 cm -3 and less than or equal to 1.0 × 10 19 cm -3 is. [6] A manufacturing process for an indium phosphide single crystal to be produced by a vertical boat process, the process comprising: Providing a single-crystal growth apparatus comprising at least one cylindrical crucible and a heater arranged to surround an outer circumference of the crucible; Placing a seed crystal in a lower part of the crucible and placing an indium phosphide bulk above the seed crystal in the crucible; Generating an indium phosphide melt by melting the indium phosphide bulk and part of the seed crystal by heating the crucible with the heater and bringing the indium phosphide melt and a remaining part of the seed crystal into contact; and Obtaining an indium phosphide single crystal by growing a crystal on the remainder of the seed crystal from the indium phosphide melt, wherein The heater has a first heating area and a second heating area, which is arranged along an axial direction of the crucible and holds the first heating area. the first heating area has a first surface and a second surface the second heating area has a third and a fourth surface the third surface faces the first surface, which is located on an upper side of the axial direction in the first heating area, the fourth surface faces the second surface, which is located on a lower side in the axial direction in the first heating area, an outer perimeter of the first heating area is surrounded by the second heating area, a first side surface, which forms an inner circumference of the first heating area, lies in a cylindrical plane which contains a second side surface, which forms an inner circumference of the second heating area, the first heating zone is designed to heat the crucible with a power output that differs from the power output in the second heating zone, a distance from the center of a radial direction of the crucible to the first side surface and a distance from the center of the radial direction of the crucible to the second side surface are each greater than or equal to 60 mm and less than or equal to 65 mm, In the recovery of the indium phosphide single crystal in a plane of a first cross-section parallel to the axial direction and containing the center of the radial direction of the crucible, the inner circumferential edges of the first face, the second face, the third face, and the fourth face are defined in the radial direction as a first position, a second position, a third position, and a fourth position, respectively; a midpoint of the first position and the second position is defined in the axial direction as a fifth position; and temperatures at the third position, the fourth position, and the fifth position are defined as a first temperature, a second temperature, and a third temperature, respectively, and heating is carried out using output powers in the first heating area and the second heating area: The third temperature is maintained at a temperature that is lower than the first temperature and lower than the second temperature; a difference between the second temperature and the third temperature of 1°C or more and 2°C or less; and a temperature gradient of greater than or equal to 0.295°C / mm and less than or equal to 0.305°C / mm parallel to the axial direction in an area of ​​greater than or equal to 50 mm and less than or equal to 65 mm below the fifth position parallel to the axial direction; a temperature gradient of greater than or equal to 0.235°C / mm and less than or equal to 0.245°C / mm parallel to the axial direction of the crucible in an area greater than or equal to 25 mm and less than 50 mm below the fifth position parallel to the axial direction; a temperature gradient of greater than or equal to 0.095°C / mm and less than or equal to 0.105°C / mm parallel to the axial direction in an area greater than or equal to 0 mm and less than 25 mm below the fifth position parallel to the axial direction; a temperature gradient of greater than or equal to 0.055°C / mm and less than or equal to 0.065°C / mm parallel to the axial direction in an area greater than 0 mm and less than or equal to 35 mm above the fifth position parallel to the axial direction; and a temperature gradient of greater than or equal to 0.035°C / mm and less than or equal to 0.045°C / mm parallel to the axial direction in an area greater than 35 mm and less than or equal to 85 mm above the fifth position parallel to the axial direction is generated, and Obtaining the indium phosphide single crystal is achieved by maintaining a position of an interface between the indium phosphide melt and the crystal on an inner circumferential surface of the crucible in a region greater than or equal to 43 mm and less than or equal to 45 mm below the fifth position parallel to the axial direction. [7] The manufacturing process for an indium phosphide single crystal according to claim 6, wherein a cross-sectional shape of the interface appearing in the first cross-section contains at least partially a curved line segment, the curved line segment has a local maximum point, which is positioned in the middle of the curved line segment, and two local minimum points, which are positioned accordingly on both sides of the local maximum point in the radial direction, and In the axial direction, the positions of the two ends of the curved line segment are higher than the local minimum points. [8] The manufacturing process for an indium phosphide single crystal according to claim 7, wherein the curved line segment fulfills the relationships: R / √2−0.1 R≤D1≤R / √2+0.1 R; 0.1 D1≤D2; and 0,1(R−D1)≤D3 where R is the bore radius of the crucible and has the unit mm, D1 is a distance between a point corresponding to the local maximum point on a first line segment and a point corresponding to one of the local minimum points on the first line segment, and has the unit mm, where the first line segment appears when the curved part of the line is virtually projected onto a straight line parallel to the radial direction. D2 is a distance between a point corresponding to the local maximum point on a second line segment and a point corresponding to one of the local minimum points on the second line segment, and has the unit mm, where the second line segment appears when the curved part of the line is virtually projected onto a straight line parallel to the axial direction, and D3 is a distance between a point corresponding to a first local minimum point on the second line segment and a point corresponding to a first endpoint on the second line segment, and has the unit mm, where the first local minimum point is one of the two local minimum points and the first endpoint is one endpoint of the two endpoints that is closer to the first local minimum point.

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