Method of manufacturing crystal, hexagonal semiconductor crystal and element

Abstract

To provide a method of manufacturing a crystal that can make crystal defect density different between mutually different plane directions, and a hexagonal semiconductor crystal.SOLUTION: A method of manufacturing a crystal includes the processes of: preparing a hexagonal semiconductor single crystal; and pressing the hexagonal semiconductor single crystal at a temperature which is 1,000°C or higher and lower than the fusion point or sublimation point of the hexagonal semiconductor single crystal so as to cause the hexagonal semiconductor crystal to deform in at least one or more directions. The hexagonal semiconductor single crystal is characterized in that an in-plane average of a spread of X-ray diffraction intensity measured in at least one crystal plane among crystal planes parallel with a main axis is different from an in-plane average of a spread of X-ray diffraction intensity measured in a crystal plane perpendicular to the main axis.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a method for producing a crystal, a hexagonal semiconductor crystal, and an element. [Background technology]

[0002] Bulk semiconductor single crystals having a hexagonal crystal structure, such as gallium nitride (GaN), aluminum nitride (AlN), aluminum gallium nitride (AlGaN) or silicon carbide (SiC) (hereinafter referred to as "hexagonal semiconductor single crystals"), are widely used as substrates for electronic devices, millimeter wave or terahertz wave filters and transceivers, light emitting elements such as light emitting diodes or semiconductor lasers, or as optical components, heat transfer devices, etc.

[0003] Hexagonal semiconductor single crystals are manufactured by crystal growth methods such as sublimation, vapor phase growth, or ammonothermal. For example, Patent Document 1 discloses a method for manufacturing bulk AlN single crystals. Hexagonal semiconductor single crystals manufactured by conventional manufacturing methods have a substantially uniform crystal defect density distribution throughout the entire crystal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2006-511432 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional crystal manufacturing methods cannot manufacture hexagonal semiconductor single crystals so as to intentionally include many crystal defects only in a specific crystallographically defined plane orientation. Therefore, it is not possible to selectively transmit electric current, heat, light, sound waves, elastic waves, etc., only in a specific direction of the hexagonal semiconductor single crystal. Therefore, it is difficult to realize highly efficient electronic devices, filters, resonators, optical components, etc.

[0006] An object of the present disclosure is to provide a method for producing a crystal that can intentionally vary the crystal defect densities of different plane orientations, a hexagonal semiconductor crystal, and an element. [Means for solving the problem]

[0007] In order to achieve the above object, one aspect of the present disclosure is a method for producing a crystal, comprising: a step of preparing a hexagonal semiconductor single crystal; and a step of deforming the hexagonal semiconductor single crystal in at least one direction by applying pressure to the hexagonal semiconductor single crystal at a temperature of 1000° C. or higher and lower than the melting point or sublimation point of the hexagonal semiconductor single crystal.

[0008] Another aspect of the present disclosure is a hexagonal semiconductor single crystal in which the in-plane average of the spread of X-ray diffraction intensity measured in at least one crystal plane parallel to the principal axis is different from the in-plane average of the spread of X-ray diffraction intensity measured in a crystal plane perpendicular to the principal axis.

[0009] Yet another aspect of the present disclosure is an element having a substrate made of a hexagonal semiconductor single crystal, in which the in-plane average of the spread of X-ray diffraction intensity measured in at least one crystal plane parallel to the principal axis differs from the in-plane average of the spread of X-ray diffraction intensity measured in a crystal plane perpendicular to the principal axis. Effect of the Invention

[0010] According to the present disclosure, it is possible to provide a manufacturing method of a crystal that can intentionally make the crystal defect densities of different plane orientations different from each other, and a hexagonal semiconductor crystal and element. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a crystal manufacturing apparatus according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a perspective view of a crystal before compression according to an embodiment of the present disclosure. [Diagram 3]FIG. 13 is a perspective view of a crystal after compression according to an embodiment of the present disclosure. [Figure 4] 1 is a graph showing a stress curve during compression at 2000° C. of the crystal according to the first example. [Diagram 5] 13 is a graph showing a stress curve when the crystal according to the second example is compressed at 1000° C. [Figure 6] 1 is a graph showing a stress curve of a crystal according to a comparative example when compressed at room temperature. [Figure 7] FIG. 2 is a perspective view showing a method for measuring X-ray diffraction intensity according to an embodiment of the present disclosure. [Figure 8] FIG. 2 is a side view illustrating a method for measuring X-ray diffraction intensity according to an embodiment of the present disclosure. [Figure 9] FIG. 2 is a plan view illustrating a method for measuring X-ray diffraction intensity according to an embodiment of the present disclosure. [Figure 10] 4 is a graph showing the measurement results of the X-ray diffraction intensity of the (0001) plane at measurement point a of the crystal according to the first example. [Figure 11] 4 is a graph showing the measurement results of the X-ray diffraction intensity of the (0001) plane at measurement point b of the crystal according to the first example. [Figure 12] 1 is a graph showing the measurement results of the X-ray diffraction intensity of the (0001) plane at measurement point c of the crystal according to the first example. [Figure 13] 1 is a graph showing the measurement results of the X-ray diffraction intensity of the (0001) plane at measurement point d of the crystal according to the first example. [Figure 14] 1 is a graph showing the measurement results of the X-ray diffraction intensity of the (0001) plane at measurement point e of the crystal according to the first example. [Figure 15] 1 is a graph showing the measurement results of the X-ray diffraction intensity of the (0001) plane of an uncompressed crystal according to a comparative example. [Figure 16] 4 is a graph showing the measurement results of the X-ray diffraction intensity of the (1-100) plane at measurement point a of the crystal according to the first example. [Figure 17] 4 is a graph showing the measurement results of the X-ray diffraction intensity of the (1-100) plane at measurement point b of the crystal according to the first example. [Figure 18]1 is a graph showing the measurement results of the X-ray diffraction intensity of the (1-100) plane at measurement point c of the crystal according to the first example. [Figure 19] 1 is a graph showing the measurement results of the X-ray diffraction intensity of the (1-100) plane at measurement point d of the crystal according to the first example. [Figure 20] 1 is a graph showing the measurement results of the X-ray diffraction intensity of the (1-100) plane at measurement point e of the crystal according to the first example. [Figure 21] 1 is a graph showing the measurement results of the X-ray diffraction intensity of the (1-100) plane of an uncompressed crystal according to a comparative example. [Figure 22] 1 is a table showing the results of tabulating the spread of diffraction intensity for the crystal of Example 1 and the uncompressed crystal of the comparative example. [Diagram 23] FIG. 1 is a conceptual diagram of a crystal before compression according to an embodiment of the present disclosure. [Figure 24] FIG. 1 is a conceptual diagram of a crystal after compression according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the description of the drawings referred to in the following description, the same or similar parts are denoted with the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each layer, etc., differ from the actual ones. Therefore, the specific thickness and dimensions should be determined with reference to the following description. In addition, it goes without saying that the drawings include parts with different dimensional relationships and ratios.

[0013] In addition, in the notation of Miller indices in this disclosure, "-" refers to a bar attached to the index immediately following it, and placing "-" before an index represents a negative index.

[0014] <Crystal manufacturing equipment> Fig. 1 shows a schematic configuration of a crystal manufacturing apparatus (compression processing apparatus) according to an embodiment of the present disclosure. As shown in Fig. 1, the crystal manufacturing apparatus according to an embodiment of the present disclosure includes a lower punch 11, which is a pressurizing jig, and a lower spacer 12, which is a contact body provided on the upper surface of the lower punch 11. A workpiece such as a crystal 1x can be placed on the upper surface of the lower spacer 12.

[0015] An upper spacer 13, which is a contact body, is provided above the lower spacer 12 so that the upper and lower surfaces of the lower spacer 12 face each other. An upper punch 14, which is a pressing tool, is provided on the upper surface of the upper spacer 13. A crosshead 15 is provided on the upper surface of the upper punch 14. The crosshead 15 measures the amount of displacement of the upper punch 14. Here, the amount of displacement of the upper punch 14 is the amount of displacement of the upper surface of the upper punch 14 with respect to the lower surface of the lower punch 11.

[0016] A load cell 16 is provided on the upper surface of the crosshead 15. The load cell 16 measures the amount of load applied to a workpiece such as the crystal 1x, and controls the amount of load.

[0017] A heater 17, which is a heating element for heating a workpiece such as a crystal 1x, is provided around the lower spacer 12 and the upper spacer 13. The heater 17 can be composed of a resistance heater such as a metal heating element made of tungsten (W) or molybdenum (Mo) or a non-metal heating element made of graphite.

[0018] A heat insulating material 19 is provided around the heater 17. By providing the heat insulating material 19, the workpiece such as the crystal 1x can be efficiently heated by the heater 17. A temperature detection element 18 is provided so as to be in contact with the lower spacer 12. The temperature detection element 18 is formed of, for example, a thermocouple.

[0019] <Crystal manufacturing method> Next, an example of a method for producing a crystal according to an embodiment of the present disclosure using the crystal production apparatus according to the embodiment of the present disclosure shown in FIG. 1 will be described.

[0020] First, a crystal 1x as shown in Fig. 2 is prepared. The crystal 1x is manufactured by any crystal growth method such as vapor phase growth or ammonothermal method. The crystal growth method for manufacturing the crystal 1x is not particularly limited. The crystal 1x is not compressed and has a substantially uniform crystal defect density distribution throughout the crystal.

[0021] Crystal 1x is composed of, for example, a hexagonal nitride semiconductor crystal such as aluminum nitride (AlN), gallium nitride (GaN), or aluminum gallium nitride (AlGaN), or a hexagonal semiconductor single crystal such as silicon carbide (SiC). Crystal 1x may contain about 90% or more of AlN, GaN, AlGaN, or SiC as a main component, with the remainder being unavoidable impurities. Crystal 1x may contain about 99% or more of AlN, GaN, AlGaN, or SiC as a main component, or may contain about 99.9% or more of AlN, GaN, AlGaN, or SiC as a main component.

[0022] The crystal 1x has a substantially rectangular parallelepiped shape. The shape of the crystal 1x is not particularly limited, and may be, for example, a flat plate shape, a cylindrical shape, a disk shape, or the like. The crystal 1x may be cut out from a crystal ingot and processed. The width W1, depth L1, and height H1 of the crystal 1x are not particularly limited, and can be appropriately adjusted. For example, the width W1 of the crystal 1x may be about 1 mm or more and 20 mm or less, the depth L1 may be about 1 mm or more and 20 mm or less, and the height H1 may be about 1 mm or more and 20 mm or less.

[0023] In Fig. 2, the direction parallel to the width W1 of the crystal 1x (left-right direction in Fig. 2) is defined as the X-axis direction, the direction parallel to the depth L1 of the crystal 1x and perpendicular to the X-axis direction (diagonal direction in Fig. 2) is defined as the Y-axis direction, and the direction parallel to the height H1 of the crystal 1x and perpendicular to the X-axis and Y-axis directions (up-down direction in Fig. 2) is defined as the Z-axis direction. The same directions are defined in Fig. 3.

[0024] As shown in Figure 2, the

[0001] axis, which is the principal axis (c-axis) of crystal 1x, is parallel to the Y-axis direction. The (0001) plane, which is a crystal plane perpendicular to the principal axis of crystal 1x, is parallel to the X-axis direction and the Z-axis direction. The [11-20] axis of crystal 1x is perpendicular to the principal axis of crystal 1x and forms a 45 degree angle with the Z-axis direction. The crystal plane parallel to the principal axis and the [11-20] axis of crystal 1x is the (1-100) plane.

[0025] Next, the crystal 1x shown in FIG. 2 is placed on the upper surface of the lower spacer 12 of the crystal manufacturing apparatus according to the embodiment of the present disclosure shown in FIG.

[0026] Next, the heater 17 heats the crystal 1x to a predetermined target temperature while measuring the temperature with the temperature detection element 18. The target temperature is, for example, 1000°C or higher and lower than the melting point or sublimation point of the crystal 1x. It is more preferable that the target temperature is 2000°C or higher and lower than the melting point or sublimation point of the crystal 1x. The higher the target temperature, the less likely the crystal 1x is to break when compressed, and the easier it is for the crystal 1x to deform.

[0027] After the target temperature is reached, in order to make the temperature inside the crystal 1x uniform, the temperature is maintained for a certain period of time while maintaining the output of the heater 17 so that the temperature measured by the temperature detection element 18 remains at the target temperature. This holding time is, for example, about 1 minute or more and 1 hour or less, and can be appropriately adjusted depending on the material and size of the crystal 1x, the distance between the temperature measurement point by the temperature detection element 18 and the crystal 1x, etc.

[0028] Next, while maintaining the temperature at the target temperature, the upper punch 14 is displaced toward the lower punch 11, and a load is applied to the crystal 1x, pressurizing it, thereby deforming the crystal 1x in at least one direction. Here, the crystal 1x is compressed and deformed in at least one direction, that is, in the direction in which the upper punch 14 and the lower punch 11 face each other (the vertical direction in FIG. 1). The target amount of displacement is, for example, about a compression ratio of the crystal 1x in one direction of 10% or more and 80% or less. The amount of displacement of the crystal 1x is measured by the crosshead 15, and when the amount of displacement reaches the target amount, the driving of the upper punch 14 is stopped.

[0029] At this time, it is preferable to control the crosshead 15 so that the displacement of the crystal 1x changes at a constant speed. The speed of the displacement of the crystal 1x is, for example, about 0.01 mm / min or more and 1 mm / min or less, and can be adjusted as appropriate. By making the displacement of the crystal 1x at a constant speed, it is possible to prevent the crystal 1x from being cracked due to a large load being applied to the crystal 1x. The pressure applied to the crystal 1x is, for example, 1×10 7 Pa or more, 1×10 9 This is about Pa or less and can be adjusted appropriately.

[0030] In FIG. 2, the pressure direction (compression direction) of the crystal 1x is shown by arrows D1 and D2. Here, the case where the crystal 1x is compressed by applying a load in the Z-axis direction in FIG. 2, that is, in a direction perpendicular to the main axis of the crystal 1x, parallel to the (0001) plane, and at an angle of 45° with the (1-100) plane, is illustrated. The pressure direction of the crystal 1x is not particularly limited. For example, the crystal 1x may be compressed by applying pressure in the X-axis direction in FIG. 2, or may be compressed by applying pressure in the Y-axis direction in FIG. 2.

[0031] After the application of the load is terminated, the compressed crystal 1x is cooled and taken out. The cooling may be natural cooling, or may be performed by gradually lowering the heater output, or may be performed by using a forced cooling means, for a shorter period of time than natural cooling.

[0032] As described above, according to the method for producing a crystal according to the embodiment of the present disclosure, a hexagonal semiconductor single crystal, crystal 1x, is pressurized to deform crystal 1x in at least one direction. This allows crystal defects to be intentionally introduced in a direction parallel to the pressure direction of crystal 1x, so that crystal defect distributions in different plane orientations can be made different from each other. For example, as shown in FIG. 2, by applying pressure from a direction perpendicular to the main axis of crystal 1x, crystal defects in a direction perpendicular to the main axis of crystal 1x can be increased more than crystal defects in a direction parallel to the main axis of crystal 1x. In addition, since the compression direction and crystal orientation of crystal 1x can be set arbitrarily, crystal defects can be intentionally introduced only in an arbitrary direction of crystal 1x.

[0033] Furthermore, according to the method for producing a crystal according to an embodiment of the present disclosure, by pressurizing the crystal 1x at a temperature of 1000° C. or higher, cracking of the crystal 1x can be suppressed and the crystal 1x can be easily deformed.

[0034] <Hexagonal semiconductor crystal> Next, a crystal according to an embodiment of the present disclosure manufactured by the manufacturing method of a crystal according to an embodiment of the present disclosure will be described. Here, a case will be illustrated in which the crystal according to an embodiment of the present disclosure is manufactured by compressing and deforming the crystal 1x shown in FIG. 2 in the manufacturing method of a crystal according to an embodiment of the present disclosure. The crystal 1 according to an embodiment of the present disclosure has a substantially rectangular parallelepiped shape as shown in FIG. 3. The shape of the crystal 1 according to an embodiment of the present disclosure is not particularly limited, and may be, for example, a flat plate shape, a cylindrical shape, a disk shape, or the like. The shape of the crystal 1 according to an embodiment of the present disclosure may be a non-uniform three-dimensional shape due to compression deformation. The shape of the crystal 1 according to an embodiment of the present disclosure may be a rectangular parallelepiped shape processed after compression deformation.

[0035] The crystal 1 according to the embodiment of the present disclosure may have a size and shape that can be applied to various products, with the crystal 1 according to the embodiment of the present disclosure being used as a substrate or the like as it is. The crystal 1 according to the embodiment of the present disclosure may be applied to various products after being shaped into a predetermined size and shape by processing such as grinding and cutting. A plurality of parts may be formed from the crystal 1 according to the embodiment of the present disclosure.

[0036] The crystal 1 according to the embodiment of the present disclosure is composed of, for example, a hexagonal nitride semiconductor crystal such as aluminum nitride (AlN), gallium nitride (GaN) or aluminum gallium nitride (AlGaN), or a hexagonal semiconductor single crystal such as silicon carbide (SiC). The crystal 1 according to the embodiment of the present disclosure may contain about 90% or more of AlN, GaN, AlGaN or SiC as a main component, with the remainder being unavoidable impurities. The crystal 1x may contain about 99% or more of AlN, GaN, AlGaN or SiC as a main component, or about 99.9% or more.

[0037] The width W2, depth L2 and height H2 of the crystal 1 according to the embodiment of the present disclosure are not particularly limited and can be appropriately adjusted within a range applicable to various products. The width W2 of the crystal 1 according to the embodiment of the present disclosure may be larger than the width W1 of the crystal 1x before compression, the depth L2 of the crystal 1 according to the embodiment of the present disclosure may be larger than the depth L1 of the crystal 1x before compression, and the height H2 of the crystal 1 according to the embodiment of the present disclosure may be smaller than the height H1 of the crystal 1x before compression. The height H2 of the crystal 1 according to the embodiment of the present disclosure may be about 20% or more and 90% or less of the height H1 of the crystal 1x before compression.

[0038] The crystal 1 according to the embodiment of the present disclosure has two different crystal planes with different in-plane averages of the spread of the X-ray diffraction intensity measured. The two different crystal planes may be a (0001) plane perpendicular to the main axis, and a (1-100) plane, (11-20) plane, (10-10) plane, etc. parallel to the main axis. Alternatively, they may be any two of the (1-100) plane, (11-20) plane, (10-10) plane, etc. parallel to the main axis. The two different crystal planes may be a crystal plane parallel to the pressing direction in the manufacturing method of the crystal according to the embodiment of the present disclosure, and a crystal plane perpendicular to the pressing direction.

[0039] Here, the "spread of X-ray diffraction intensity" refers to a range in which an intensity of 1 / 100 or more of the maximum peak intensity is detected in the X-ray diffraction intensity distribution of an arbitrary crystal plane measured by X-ray diffraction (XRD). The range of the spread of X-ray diffraction intensity may include a plurality of peaks. The spread of X-ray diffraction intensity does not necessarily have to be a continuous range of intensity of 1 / 100 or more of the maximum peak intensity. When a region of less than 1 / 100 of the maximum peak intensity sandwiched between regions of 1 / 100 or more of the maximum peak intensity is 0.1° or less, the spread of X-ray diffraction intensity also includes the region of 1 / 100 or more of the maximum peak intensity outside the region.

[0040] For example, in the crystal 1 according to the embodiment of the present disclosure, the in-plane average of the spread of the X-ray diffraction intensity measured on at least one crystal plane among the (1-100) plane, (11-20) plane, (10-10) plane, etc., which are crystal planes parallel to the principal axis, is different from the in-plane average of the spread of the X-ray diffraction intensity measured on the (0001) plane, which is a crystal plane perpendicular to the principal axis. In the crystal 1 according to the embodiment of the present disclosure, the in-plane average of the spread of the X-ray diffraction intensity measured on at least one crystal plane among the (1-100) plane, (11-20) plane, (10-10) plane, etc., which are crystal planes parallel to the principal axis, may be larger than the in-plane average of the spread of the X-ray diffraction intensity measured on the (0001) plane, which is a crystal plane perpendicular to the principal axis.

[0041] The in-plane average of the spread of X-ray diffraction intensity measured in at least one crystal plane among the (1-100) plane, (11-20) plane, (10-10) plane, etc., which are crystal planes parallel to the principal axis of the crystal 1 according to an embodiment of the present disclosure, is, for example, at least 2 times and at most 100 times, optionally at least 10 times, optionally at least 20 times, or optionally at least 30 times, of the in-plane average of the spread of X-ray diffraction intensity measured in the (0001) plane, which is a crystal plane perpendicular to the principal axis.

[0042] The in-plane average of the spread of X-ray diffraction intensity measured in at least one crystal plane among the (1-100) plane, (11-20) plane, (10-10) plane, etc., which are crystal planes parallel to the principal axis of the crystal 1 according to an embodiment of the present disclosure, is larger than the in-plane average of the spread of X-ray diffraction intensity measured in the (0001) plane, which is a crystal plane perpendicular to the principal axis, by, for example, about 1° or more and about 50° or less, and may be larger by about 10° or more, by about 20° or more, or by about 30° or more.

[0043] The in-plane average spread of the X-ray diffraction intensity measured in at least one crystal plane among the (1-100) plane, (11-20) plane, (10-10) plane, etc., which are crystal planes parallel to the main axis of the crystal 1 according to an embodiment of the present disclosure, is, for example, about 1° or more and about 50° or less, optionally about 5° or more, optionally about 10° or more, optionally about 20° or more, or optionally about 30° or more.

[0044] The in-plane average spread of the X-ray diffraction intensity measured on the (0001) plane, which is a crystal plane perpendicular to the main axis of the crystal 1 according to an embodiment of the present disclosure, is, for example, about 0.01° or more and about 10° or less, optionally about 5° or less, optionally about 2° or less, optionally about 1° or less, or optionally about 0.1° or less.

[0045] Furthermore, when the X-ray diffraction intensities of the crystal 1 according to the embodiment of the present disclosure and the crystal 1x before compression are compared, the in-plane average of the spread of the X-ray diffraction intensity measured in at least one plane orientation of the crystal 1 according to the embodiment of the present disclosure is larger than the in-plane average of the spread of the X-ray diffraction intensity measured in the corresponding at least one plane orientation of the crystal 1x before compression. The at least one plane orientation may be a (0001) plane that is a crystal plane perpendicular to the main axis of the crystal 1, or a (1-100) plane, a (11-20) plane, or a (10-10) plane that is a crystal plane parallel to the main axis of the crystal 1.

[0046] The in-plane average of the spread of the X-ray diffraction intensity measured on the (0001) plane, which is a crystal plane perpendicular to the principal axis of the crystal 1 according to the embodiment of the present disclosure, is, for example, about 2 times or more, may be about 10 times or more, may be about 20 times or more, may be about 40 times or more, or may be about 100 times or more, of the in-plane average of the spread of the X-ray diffraction intensity measured on the (0001) plane, which is a crystal plane perpendicular to the principal axis of the crystal 1x before compression of the crystal 1 according to the embodiment of the present disclosure. The in-plane average of the spread of the X-ray diffraction intensity measured on the (0001) plane, which is a crystal plane perpendicular to the principal axis of the crystal 1x before compression, is, for example, about 1° or less, may be about 0.5° or less, or may be about 0.05° or less.

[0047] For example, the in-plane average of the spread of X-ray diffraction intensity measured on at least one crystal plane among the (1-100) plane, (11-20) plane, (10-10) plane, etc., which are crystal planes parallel to the principal axis of crystal 1 according to an embodiment of the present disclosure, is, for example, about 2 times or more, optionally about 10 times or more, optionally about 20 times or more, optionally about 40 times or more, or optionally about 100 times or more, of the in-plane average of the spread of X-ray diffraction intensity measured on a crystal plane corresponding to crystal 1 according to an embodiment of the present disclosure among the (1-100) plane, (11-20) plane, (10-10) plane, etc., which are crystal planes parallel to the principal axis of crystal 1x before compression. The in-plane average of the spread of X-ray diffraction intensity measured in at least one crystal plane among the (1-100) plane, the (11-20) plane, the (10-10) plane, etc., which are crystal planes parallel to the principal axis of the crystal 1x before compression, is, for example, about 1° or less, may be about 0.5° or less, or may be about 0.05° or less.

[0048] The crystal 1 according to the embodiment of the present disclosure has different in-plane averages of the spreads of X-ray diffraction intensity measured on two different crystal planes, and thus exhibits directional dependency in the crystallinity quantified by the spread of X-ray diffraction intensity, and can selectively transmit electric current, heat, light, sound waves, elastic waves, etc. in a specific direction. This makes it possible to realize highly efficient semiconductor electronic devices, millimeter wave or terahertz wave filters and transceivers, light emitting elements, optical components, heat transfer devices, etc., such as various elements having substrates made of the crystal 1 according to the embodiment of the present disclosure.

[0049] <Example of crystal manufacturing method> Next, a first example of a method for producing a crystal according to an embodiment of the present disclosure will be described. First, a pre-compressed crystal 1x as shown in FIG. 2 was prepared. The pre-compressed crystal 1x is made of aluminum nitride (AlN) single crystal and has a rectangular parallelepiped shape with a width W1 of 6 mm, a depth L1 of 5 mm, and a height H1 of 10 mm. The crystal orientation of the pre-compressed crystal 1x is such that the

[0001] axis, which is the main axis (c-axis), is perpendicular to the X-axis direction, and the [11-20] axis forms an angle of 45° with the Z-axis direction.

[0050] As the crystal manufacturing apparatus according to the embodiment of the present disclosure, MTS-808 manufactured by MTS Corporation, in which the lower punch 11, the upper punch 14, the crosshead 15, and the load cell 16 are integrated, as shown in FIG. 1, was used. As the lower spacer 12 and the upper spacer 13, cylindrical ones made of silicon nitride (SiN) and having a diameter of 25 mm were prepared. In the lower spacer 12, a thermocouple temperature measuring part was installed as the temperature detection element 18. As the heater 17, a cylindrical resistance heater made of tungsten mesh was installed so as to cover a part of the lower punch 11, the lower spacer 12, the crystal 1x, the upper spacer 13, and a part of the upper punch 14. Furthermore, the heater 17 was covered around and above and below with a heat insulating material 19, thereby preparing the crystal manufacturing apparatus according to the embodiment of the present disclosure.

[0051] Next, the crystal 1x was sandwiched between a lower spacer 12 and an upper spacer 13, and further the lower spacer 12 and the upper spacer 13 were sandwiched between a lower punch 11 and an upper punch 14. At this time, the crystal 1x was arranged so that two faces facing each other in the Z-axis direction of the crystal 1x in Fig. 2 were in contact with the lower spacer 12 and the upper spacer 13. That is, as shown in Fig. 2, the crystal 1x was arranged so that the pressure direction was perpendicular to the

[0001] axis of the crystal 1x and the angle between the pressure direction and the [11-20] axis of the crystal 1x was 45°.

[0052] Next, the heater 17 was used to heat the crystal 1x at a target temperature of 2000°C. After the temperature measured by the temperature detection element 18 reached 2000°C, the crystal 1x was held for 30 minutes while maintaining the heated state in order to make the temperature of the entire crystal 1x uniform. After holding for 30 minutes, the upper punch 14 was driven toward the lower punch 11 while maintaining the temperature at 2000°C, and a load was applied to the crystal 1x. At this time, the displacement speed of the upper punch 14 was controlled to be 0.5 mm / min. The displacement amount of the upper punch 14 was measured at the crosshead 15, and the upper punch 14 was stopped when the compression ratio became 50% of the compression axis length of the crystal 1x before processing, that is, when the upper punch 14 was displaced 5 mm. After stopping the drive of the upper punch 14, the compressed crystal 1x was cooled to room temperature by natural cooling, and then the compressed crystal 1x was taken out from between the lower spacer 12 and the upper spacer 13.

[0053] Further, as a second example of the method for manufacturing a crystal according to an embodiment of the present disclosure, the target temperature when compressing crystal 1x was made different from that of the first example by setting it to 1000 °C, and other conditions were the same as those of the first example, and crystal 1x was compression-deformed. Further, as a comparative example of the method for manufacturing a crystal according to an embodiment of the present disclosure, when compressing crystal 1x, it was made different from the first example by setting it to room temperature without heating, and other conditions were the same as those of the first example, and crystal 1x was compression-deformed.

[0054] Figures 4 to 6 show the correlation between the displacement amount of the upper punch 14 and the load applied to crystal 1x in the first example, the second example, and the comparative example. As shown in Figure 4, in the first example, until the displacement amount of the upper punch 14 reached about 0.1 mm, the load and displacement changed linearly, and it was estimated that crystal 1x underwent elastic displacement. After the displacement amount exceeded about 0.1 mm, it showed a non-linear monotonic increase up to the displacement target of 5 mm. From this, it can be seen that crystal 1x underwent plastic deformation without reaching fracture. As shown in Figure 5, in the second example, crystal 1x was deformed up to the displacement target of 5 mm without reaching fracture. As shown in Figure 6, in the comparative example, cracking occurred and the processing stopped when the displacement amount exceeded 1.1 mm before reaching the displacement target of 5 mm.

[0055] <Measurement method of X-ray diffraction method> Next, the X-ray diffraction method (XRD) for measuring the spread of the X-ray diffraction intensity of crystal 1 and crystal 1x before compression according to an embodiment of the present disclosure will be described. As shown in Figure 7, the X-ray diffractometer for performing XRD measurement includes a sample stage 21, an X-ray generator 22 and a detector 23 arranged above the sample stage 21. On the sample stage 21, crystal 1 according to an embodiment of the present disclosure is arranged as the object to be measured.

[0056] The XRD measurement method selects either Out-of-Plane measurement or In-Plane measurement based on the relative positional relationship between the measurement plane and the crystal surface (X-ray irradiation surface) irradiated with X-rays. When the plane for measuring crystallinity (diffraction plane) is parallel to the X-ray irradiation surface, Out-of-Plane measurement is performed. When the X-ray irradiation surface and the diffraction plane are perpendicular, In-Plane measurement is performed.

[0057] First, the out-of-plane measurement will be described. As shown in Fig. 8, in the out-of-plane measurement, the angle between the X-ray irradiation surface and the incident X-ray 31 is defined as ω, and the angle between the incident X-ray 31 and the diffracted light 32 (the optical axis of the detector 23) is defined as 2θ.

[0058] In the out-of-plane method, the X-ray generator 22 and the detector 23 are scanned concentrically around the X-ray irradiation point 33 within a plane including the X-ray generator 22, the detector 23, and the crystal 1, to identify the position at which the intensity of the diffracted light 32 is maximum. Next, the positions of the X-ray generator 22 and the detector 23 are scanned concentrically so that only the value of the angle ω changes while maintaining the value of the angle 2θ at the identified position, and the spread of the diffraction intensity is measured.

[0059] In addition, when changing only the angle ω, it is not necessary to move the positions of the X-ray generator 22 and the detector 23. The crystal 1 may be rotated around the X-ray irradiation point 33 as the center and an axis perpendicular to the plane including the X-ray generator 22, crystal 1, and detector 23.

[0060] Next, the in-plane measurement will be described. In the in-plane measurement, as shown in Fig. 8, the crystal 1, the X-ray generator 22, and the detector 23 are arranged so that the angle ω between the incident X-ray 31 and the X-ray irradiation surface is 1° or less, and the angle 2θ between the incident X-ray 31 and the diffracted light 32 is 2° or less. Also, as shown in Fig. 9, the angle between the incident X-ray 31 and the diffracted light 32 when viewed from directly above the X-ray irradiation surface is defined as "2θχ", and the angle when the crystal 1 is rotated horizontally to the X-ray irradiation surface around the X-ray irradiation point 33 is defined as "φ".

[0061] Next, in order to identify the position where the intensity of the diffracted light 32 is maximum, the rotation angle of the crystal 1 and the position of the detector 23, i.e., the angle φ and the angle 2θχ, are scanned. At this time, the detector 23 scans in a plane approximately parallel to the X-ray irradiation surface, concentrically around the X-ray irradiation point 33. If necessary, the angle ω and the angle 2θ may be scanned in the range of 0 to 1°, respectively, for fine adjustment.

[0062] Next, while keeping the position of the detector 23 at the identification position, the rotation φ of the crystal is scanned back and forth around the identification position. That is, the angle 2θχ is fixed and only the angle φ is changed before and after the identification position, and the spread of the diffraction intensity is measured. Note that as a method of fixing the angle 2θχ and changing only the angle φ, it is not necessarily required to rotate only the crystal 1, and the positions of the X-ray generator 22 and the detector 23 may be moved while fixing the position of the crystal 1.

[0063] The scanning amount Δω of the angle ω and the scanning amount Δφ of the angle φ from the peak identification position need to be appropriately selected according to the degree of variation in the crystal orientation introduced by the crystal compression process. When measuring the crystal plane introducing the variation in the crystal orientation, it is desirable to scan in as wide a range as possible.

[0064] <Example of Measurement of Spread of X-ray Diffraction Intensity> For the crystal manufactured in the first embodiment, in order to evaluate the anisotropy of the variation in the crystal orientation, the spread of the X-ray diffraction intensity was measured using the X-ray diffraction method (XRD). As the X-ray diffractometer, SmartLab manufactured by Rigaku Corporation was used. Cu-Kα was used as the X-ray source. The excitation voltage was set to 45 kV and the emission current was 200 mA. The measurement was performed on two planes, the (0001) plane and the (1 - 100) plane.

[0065] As shown in FIG. 7, since X-rays are irradiated to the crystal surface perpendicular to the

[0001] axis, the (0001) plane was measured out-of-plane, and the (1-100) plane was measured in-plane. In the out-of-plane measurement of the (0001) plane, the X-ray generator 22 and the detector 23 were scanned concentrically around the X-ray irradiation point 33 in the plane including the X-ray generator 22, the detector 23, and the crystal, to identify the position where the intensity of the diffracted light 32 is maximum. Next, while maintaining the value of the angle 2θ at the identified position, the positions of the X-ray generator 22 and the detector 23 were scanned concentrically so that only the value of the angle ω changed, and the spread of the diffraction intensity was measured. The amplitude of the angle ω at this time was ±1.25°. Using this procedure, measurements were performed at five different measurement points a to e in the crystal. As a comparative example, the same measurement was performed on a crystal that had the same shape and crystal orientation as the crystal in Example 1 and was not compressed.

[0066] In addition, in the in-plane measurement of the (1-100) plane, the crystal, the X-ray generator 22, and the detector 23 were arranged so that the angle ω between the incident X-ray 31 and the X-ray irradiation surface was 1° or less, and the angle 2θ between the incident X-ray 31 and the diffracted light 32 was 2° or less. Next, in order to identify the position where the intensity of the diffracted light 32 is maximum, the angle of the crystal and the position of the detector 23, i.e., the angle φ and the angle 2θχ, were scanned. Then, the angle ω and the angle 2θ were scanned in the range of 0° or more and 1° or less, respectively, for fine adjustment. Next, while keeping the position of the detector 23 at the identified position, the angle of the crystal was scanned back and forth around the identified position, and only the angle φ was changed before and after the identified position. The swing width of the angle φ at this time was ±30°. Using this procedure, measurements were performed at five different measurement points a to e in the crystal. The measurement points a to e are the same as the measurement points a to e in the in-plane measurement. In addition, as a comparative example, the in-plane measurement was also performed on a crystal having the same shape and crystal orientation as the crystal in Example 1, which was not compressed.

[0067] 10 to 14 show the profiles of X-ray diffraction intensity versus angle ω obtained by out-of-plane measurement of the (0001) plane at measurement points a to e for the crystal according to the first embodiment. As shown in FIGS. 10 to 14, the spectrum of the crystal according to the first embodiment has some peaks observed at measurement points a to e, but the spread of the X-ray diffraction intensity is 1.5° or less at all of measurement points a to e, and the in-plane average of measurement points a to e is 1.22°. Meanwhile, FIG. 15 shows the profile of X-ray diffraction intensity versus angle ω obtained by out-of-plane measurement of the (0001) plane for the uncompressed crystal according to the comparative example. For the uncompressed crystal according to the comparative example, the spread of the X-ray diffraction intensity was 0.05°, which is the lower detection limit of the detector 23.

[0068] 16 to 20 show profiles of X-ray diffraction intensity versus angle φ obtained by in-plane measurement of the (1-100) plane at measurement points a to e for the crystal according to the first embodiment. As shown in FIGS. 16 to 20, the spectrum of the crystal according to the first embodiment has some peaks observed at fixed points a to e, but the spread of the X-ray diffraction intensity is 17° or more at all of measurement points a to e, and the in-plane average of measurement points a to e is 25°. Meanwhile, FIG. 21 shows a profile of X-ray diffraction intensity versus angle φ obtained by in-plane measurement of the (1-100) plane for the uncompressed crystal according to the comparative example. In the uncompressed crystal according to the comparative example, the spread of the X-ray diffraction intensity was 0.6°, which is the lower detection limit of the detector 23.

[0069] Fig. 22 shows the results of out-of-plane measurements of the (0001) plane and in-plane measurements of the (1-100) plane for the crystal according to the first embodiment and the uncompressed crystal according to the comparative example. In Fig. 22, the crystal according to the first embodiment is referred to as "compressed crystal," and the uncompressed crystal according to the comparative example is referred to as "uncompressed crystal."

[0070] As shown in Fig. 22, in the crystal according to the first embodiment, it was found that the in-plane average of the spread of the X-ray diffraction intensity in the (1-100) plane was 20 times or more larger than the in-plane average of the spread of the X-ray diffraction intensity in the (0001) plane. The spread of the X-ray diffraction intensity correlates with the measured variation of the crystal orientation, and the larger the spread of the X-ray diffraction intensity, the more the crystal orientation varies. Therefore, it is found that in the crystal according to the first embodiment, the variation of the crystal orientation is selectively introduced in the (1-100) plane compared to the (0001) plane.

[0071] <About the concept of crystal deformation process> Next, the concept of the crystal deformation process will be described with reference to Figures 23 and 24. Figure 23 shows a schematic diagram of a crystal ingot 41 before pressure deformation. As shown in Figure 23, the crystal ingot 41 before pressure deformation has the same hexagonal crystal plane orientation 51 throughout the crystal ingot 41. Almost no dislocation defects are formed in the crystal ingot 41 before pressure deformation.

[0072] Consider the case where the crystal ingot 41 shown in Fig. 23 is pressed in the directions of the arrows D3 and D4. Fig. 24 shows a schematic diagram of the shape of the crystal ingot 41 shown in Fig. 23 after pressure deformation. As shown in Fig. 24, in the crystal ingot 41 after pressure deformation, the plane orientation 51 of the basal plane of the hexagonal crystal has a large variation in the rotation direction. Therefore, many dislocation defects 42 are formed in the crystal ingot 41 after pressure deformation.

[0073] <Application Examples> The crystal 1 according to the embodiment of the present disclosure, for example in the configuration shown in FIG. 3, has a crystal plane orientation in the (0001) direction over almost the entire volume when observed from a direction perpendicular to the (0001) plane of the hexagonal system, i.e., a direction parallel to the c-axis (principal axis). On the other hand, the crystal 1 according to the embodiment of the present disclosure has a large variation in crystal plane orientation when observed from a direction perpendicular to the c-axis, such as a direction perpendicular to the (1-100) plane. Therefore, heat, sound waves, and light have anisotropy in that they easily flow in a direction parallel to the c-axis and do not easily flow in a direction perpendicular to the c-axis. That is, the propagation directions of heat, sound waves, and light within the crystal can be made non-uniform. Therefore, the crystal can be applied to various elements such as highly efficient light-emitting elements, electric elements such as transistors and diodes, or surface acoustic wave elements.

[0074] For example, the crystal 1 according to the embodiment of the present disclosure has substantially the same crystal plane orientation in the (0001) plane direction, and has a large variation in the (1-100) plane direction, for example. Therefore, for example, the crystal 1 according to the embodiment of the present disclosure is made of a crystal mainly composed of aluminum nitride (AlN), processed to become a substrate having a (0001) plane as a main surface, and a surface acoustic wave (SAW) filter is formed. As a result, sound waves are transmitted only to the (0001) plane, which is the surface of the filter, and sound waves are difficult to transmit inside the bulk crystal, so that a filter with an extremely large S / N ratio can be efficiently realized. Such a filter can be applied to high-speed digital communication technology of 5G, 6G generation or later, communication using millimeter waves or terahertz waves, high-precision foreign object detection, analysis of chemical substances or biomolecules, and the like.

[0075] Moreover, the crystal 1 according to the embodiment of the present disclosure is manufactured by deforming the crystal 1x grown by any crystal growth method by applying mechanical compressive stress at high temperature. Therefore, many grain boundaries are built in because only the crystallographically slippery plane orientation selectively slides. Therefore, the crystal 1 according to the embodiment of the present disclosure is composed of a crystal mainly composed of aluminum nitride (AlN) having a large piezoelectric effect, processed to become a substrate with the (0001) plane as the main surface, and a thin film bulk acoustic resonator (FBAR) is formed using a known semiconductor processing process. As a result, on the same AlN substrate, for example, an elastic wave traveling parallel to the <1-100> direction and an elastic wave traveling perpendicular to the <1-100> direction show different frequency characteristics.

[0076] By utilizing such frequency characteristics, for example, by making an elastic wave incident parallel to the <1-100> direction and outputting it in a direction parallel to and perpendicular to the <1-100> direction, it is possible to extract an elastic wave having output peaks at two frequencies, a first frequency and a second frequency, from a single element. In this case, the second frequency may be configured to mainly include harmonic components that are, for example, an integer multiple or an integer fraction of the first frequency. By configuring in this way, it becomes possible to extract harmonic components using only a single FBAR element without providing a frequency multiplier or divider using a known semiconductor integrated circuit or the like.

[0077] In addition, the crystal 1 according to the embodiment of the present disclosure has many dislocations in a specific direction defined by crystallography, and therefore can selectively transfer heat mainly in a specific direction. Therefore, if the crystal 1 according to the embodiment of the present disclosure is used as a substrate for light-emitting elements such as lasers and light-emitting diodes (LEDs), and electric elements such as transistors and diodes, heat can be efficiently transferred in a desired direction, and the substrate can be used as a component of a highly efficient heat sink.

[0078] Furthermore, the crystal 1 according to the embodiment of the present disclosure can selectively transmit light only in a specific direction defined by crystallography. Therefore, if the crystal 1 according to the embodiment of the present disclosure is used as a substrate for a visible light semiconductor laser, an ultraviolet laser, a light emitting diode (LED), or the like, it can be used as a highly efficient optical waveguide capable of transmitting light mainly only in a desired direction.

[0079] (Other embodiments) Although the embodiment has been described above, the description and drawings forming a part of this disclosure should not be understood as limiting the present disclosure. From this disclosure, various alternative embodiments, examples and operating techniques will become apparent to those skilled in the art. Of course, the present disclosure includes various embodiments not described here. Therefore, the technical scope of the present disclosure is defined only by the invention-specific matters related to the scope of the appropriate claims from the above description. [Explanation of symbols]

[0080] 1,1x…Crystal 11...Lower punch 12…Lower spacer 13…Upper spacer 14...upper punch 15…Crosshead 16…Load cell 17…Heater 18...Temperature detection element 19…Insulation material 21...Sample stage 22…X-ray generator 23…Detector 31...Incoming X-ray 32...Diffraction light 33...X-ray irradiation point 41...Crystal ingot 42...Dislocation defect

Claims

1. Providing a hexagonal semiconductor crystal; a step of applying pressure to the hexagonal semiconductor crystal at a temperature of 1000° C. or higher and lower than the melting point or sublimation point of the hexagonal semiconductor crystal, thereby deforming the hexagonal semiconductor crystal in at least one direction; A method for producing a crystal comprising the steps of:

2. The step of pressurizing the hexagonal semiconductor crystal is carried out at a temperature of 2000° C. or higher. A method for producing the crystal described in claim 1.

3. In the step of applying pressure to the hexagonal semiconductor crystal, the hexagonal semiconductor crystal is deformed in the one direction at a constant speed. A method for producing the crystal according to claim 1 or 2.

4. The one direction is a direction perpendicular to the principal axis of the hexagonal semiconductor crystal. A method for producing the crystal according to claim 1 or 2.

5. In the step of applying pressure to the hexagonal semiconductor crystal, the compression rate of the hexagonal semiconductor crystal in the one direction is 10% or more. A method for producing the crystal according to claim 1 or 2.

6. the in-plane average spread of X-ray diffraction intensity measured in at least one plane orientation of the hexagonal semiconductor crystal before the pressure is applied is 1° or less; A method for producing the crystal according to claim 1 or 2.

7. The in-plane average of the spread of X-ray diffraction intensity measured in at least one plane orientation of the hexagonal semiconductor crystal after the pressure is applied is larger than the in-plane average of the spread of X-ray diffraction intensity measured in the at least one plane orientation of the hexagonal semiconductor crystal before the pressure is applied. A method for producing the crystal according to claim 1 or 2.

8. an in-plane average of the spread of X-ray diffraction intensity measured in at least one plane orientation of the hexagonal semiconductor crystal after the pressure application is at least twice as large as an in-plane average of the spread of X-ray diffraction intensity measured in the at least one plane orientation of the hexagonal semiconductor crystal before the pressure application; A method for producing the crystal according to claim 7.

9. The in-plane average of the spread of X-ray diffraction intensity measured in at least one plane orientation of the hexagonal semiconductor crystal after the pressure application is larger by 1° or more than the in-plane average of the spread of X-ray diffraction intensity measured in the at least one plane orientation of the hexagonal semiconductor single crystal before the pressure application. A method for producing the crystal according to claim 7.

10. The at least one plane orientation is a crystal plane perpendicular to a principal axis of the hexagonal semiconductor crystal. A method for producing the crystal according to claim 7.

11. The at least one plane orientation is a crystal plane parallel to a principal axis of the hexagonal semiconductor crystal. A method for producing the crystal according to claim 7.

12. The hexagonal semiconductor crystal includes gallium nitride, aluminum nitride, aluminum gallium nitride, or silicon carbide. A method for producing the crystal according to claim 1 or 2.

13. The in-plane average of the spread of the X-ray diffraction intensity measured on at least one of the crystal planes parallel to the principal axis is different from the in-plane average of the spread of the X-ray diffraction intensity measured on a crystal plane perpendicular to the principal axis. Hexagonal semiconductor crystal.

14. The in-plane average of the spread of the X-ray diffraction intensity measured on at least one of the crystal planes parallel to the principal axis is larger than the in-plane average of the spread of the X-ray diffraction intensity measured on a crystal plane perpendicular to the principal axis. The hexagonal semiconductor crystal according to claim 13.

15. The in-plane average of the spread of the X-ray diffraction intensity measured on at least one of the crystal planes parallel to the principal axis is at least twice as large as the in-plane average of the spread of the X-ray diffraction intensity measured on a crystal plane perpendicular to the principal axis. The hexagonal semiconductor crystal according to claim 14.

16. The in-plane average of the spread of the X-ray diffraction intensity measured on at least one of the crystal planes parallel to the principal axis is larger by 10° or more than the in-plane average of the spread of the X-ray diffraction intensity measured on a crystal plane perpendicular to the principal axis. The hexagonal semiconductor crystal according to claim 14.

17. The hexagonal semiconductor crystal is gallium nitride, aluminum nitride, aluminum gallium nitride, or silicon carbide. The hexagonal semiconductor crystal according to claim 13 or 14.

18. An element having a substrate made of a hexagonal semiconductor crystal, in which an in-plane average of the spread of X-ray diffraction intensity measured on at least one crystal plane among crystal planes parallel to a principal axis differs from an in-plane average of the spread of X-ray diffraction intensity measured on a crystal plane perpendicular to the principal axis.

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