Sublimation Growth Device

Abstract

To make temperature distribution in a vessel uniform while securing a sufficient heat capacity, even when a vessel for housing a raw material is made large.SOLUTION: In a sublimation growth device 1 for sublimating a raw material having sublimation temperature of 2000°C or more and single-crystal growing it into a seed crystal, a heating source for heating a raw material B includes plural induction heating sources 41-43 spaced from each other, and at least one resistance heating source 44 arranged at a portion separate from the induction heating sources 41-43. A control device 50 is configured to simultaneously energize the plural induction heating sources 41-43 and the resistance hearing source 44.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a sublimation growth apparatus for growing a single crystal on a seed crystal by sublimating a source material such as silicon carbide. [Background technology]

[0002] Silicon carbide (SiC) can control large amounts of power more efficiently than silicon (Si), and is therefore used in a wide range of devices, including semiconductor elements. To ensure uniformity in the characteristics of various devices, it is preferable to grow silicon carbide as a single crystal. A method known as sublimation recrystallization is used to produce silicon carbide single crystals. This method involves heating silicon carbide powder, which serves as a raw material, in a container to a high temperature of 2000°C or higher to sublimate it, and growing the powder on a seed crystal located away from the raw material, thereby producing a silicon carbide single crystal (see, for example, Patent Document 1).

[0003] In Patent Document 1, a container containing raw materials is placed inside a quartz tube, and multiple induction heating coils are provided at intervals in the axial direction of the tube so as to surround the outer surface of the quartz tube. By passing a current through each induction heating coil, the raw materials in the container are heated to the sublimation temperature. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-255693 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in order to improve the productivity of semiconductor devices, it is necessary to increase the diameter of the silicon carbide substrates used for semiconductor devices. To manufacture substrates with a large diameter, it is necessary to increase the size of the container in which the raw material is stored, particularly the diameter of the container.

[0006] If the container is made larger, the heat capacity of the heat source must be increased, and furthermore, the temperature distribution within the container becomes non-uniform, which in turn makes it difficult to stably produce high-quality silicon carbide single crystals.

[0007] The present disclosure has been made in consideration of such points, and its purpose is to ensure sufficient heat capacity even when the container in which the raw material is stored is enlarged, and to achieve uniform temperature distribution within the container. [Means for solving the problem]

[0008] To achieve the above object, one aspect of the present disclosure can be a sublimation growth apparatus including a container for containing a source material having a sublimation temperature of 2000°C or higher, a heat source for heating the container, and a control device for controlling the heat source, the container being heated by the heat source to sublimate the source material and grow a single crystal on a seed crystal. The heat sources include a plurality of induction heating sources arranged at intervals from each other and at least one resistance heating source arranged at a location separate from the induction heating sources, and the control device is configured to simultaneously energize the plurality of induction heating sources and the resistance heating source.

[0009] According to this configuration, since the heat capacity is increased by providing multiple induction heating sources that are energized simultaneously, it is possible to heat the raw material inside even in a large container to 2000°C or higher and sublimate it. In addition, since the multiple induction heating sources are arranged at intervals from each other, multiple locations on the container are heated simultaneously by the multiple induction heating sources, and other locations on the container are also heated simultaneously by resistance heating sources arranged in other locations. This makes it possible to achieve a more uniform temperature distribution inside the container. The number of induction heating sources may be three or more.

[0010] The sublimation growth apparatus may also include one or more temperature sensors that acquire the temperature state of the container and output the acquired temperature state to the control device. In this case, the control device can control the multiple induction heating sources and the resistance heating sources by performing PID (Proportional-Integral-Differential) control based on a preset temperature and the temperature state of the container output from the temperature sensor. This improves the stability of the heating temperature, enabling automatic growth of high-quality single crystals.

[0011] The multiple induction heating sources may include a first induction heating source and a second induction heating source. In this case, the control device has a first power supply circuit that supplies current to the first induction heating source and a second power supply circuit that supplies current to the second induction heating source, and can zero the difference in phase between the voltage applied to the first induction heating source and the voltage applied to the second induction heating source. This reduces magnetic field interference between the first induction heating source and the second induction heating source, improving heating efficiency.

[0012] The multiple induction heating sources may be arranged to surround the peripheral wall of the container from the outside. In this case, the resistance heating source may be arranged to protrude from the bottom wall of the container into the space surrounded by the peripheral wall. This allows the interior of the container to be heated as well, making the temperature distribution within the container more uniform. The resistance heating source may be arranged in the center of the container in a plan view, or may be arranged radially offset from the center.

[0013] The plurality of induction heating sources may include a lower induction heating source disposed outside the peripheral wall near the lower end and an upper induction heating source disposed outside the peripheral wall near the upper end, in which case the heating capacity per unit time of the lower induction heating source can be set higher than the heating capacity per unit time of the upper induction heating source.

[0014] The multiple induction heating sources may also include an intermediate induction heating source disposed outside the peripheral wall between the lower induction heating source and the upper induction heating source. In this case, the heating capacity per unit time of the lower induction heating source can be set higher than the heating capacity per unit time of the intermediate induction heating source. This allows the raw material remaining below the vessel to be efficiently sublimated and grown into a single crystal while maintaining a uniform temperature distribution. [Effects of the Invention]

[0015] As described above, it is possible to simultaneously energize multiple induction heating sources arranged at intervals from one another and at least one resistance heating source arranged in a location separate from the induction heating sources, so that even if the container in which the raw material is stored is enlarged, sufficient heat capacity can be ensured and the temperature distribution within the container can be made uniform. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a block diagram showing the configuration of a sublimation growth apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view of the container seen from above. [Figure 3] FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. [Figure 5] FIG. 2 is a perspective view showing a state in which a raw material pot is placed on the bottom wall portion. [Figure 6] FIG. [Figure 7] 4 is a flowchart showing an example of a control procedure performed by the control device. [Figure 8A] FIG. 10 is a diagram schematically illustrating the flow of a thermal fluid near a seed crystal when there is no gas outlet. [Figure 8B] FIG. 10 is a diagram schematically illustrating the flow of a thermal fluid near a seed crystal when a gas outlet is provided. [Figure 9]9A and 9B show a container and a resistance heating source according to a first modified example of the embodiment, in which (A) is a plan view and (B) is a cross-sectional view taken along line IX-IX. [Figure 10] 10A and 10B show a container and a resistance heating source according to a second modified example of the embodiment, in which (A) is a plan view and (B) is a cross-sectional view taken along line XX. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present invention, its applications, or its uses.

[0018] FIG. 1 is a block diagram showing the configuration of a sublimation growth apparatus 1 according to an embodiment of the present invention. The sublimation growth apparatus 1 is an apparatus for heating powdered raw material B to a sublimation temperature to sublimate it, and then attaching the sublimated raw material to a seed crystal A to grow a single crystal. Raw material B is, for example, silicon carbide (SiC) powder. Silicon carbide powder can be made into powder having an average particle size within a predetermined range by, for example, disintegration or classification. The sublimation temperature of silicon carbide is 2000°C or higher, for example, 2100°C to 2400°C. The single crystal silicon carbide obtained in the sublimation growth apparatus 1 is processed into, for example, wafers and used as a material for semiconductor devices.

[0019] Sublimation growth apparatus 1 includes single crystal generation unit 10 for growing silicon carbide single crystals to obtain large-diameter single crystals, control unit 50 for controlling single crystal generation unit 10, operation panel 60, and memory unit 61. Single crystal generation unit 10 and control unit 50 are spaced apart so that control unit 50 is not affected by heat radiated from single crystal generation unit 10. "Large diameter" refers to a large diameter of the silicon carbide single crystal; for example, single crystals with diameters of 6 inches or more or 8 inches or more can be produced using sublimation growth apparatus 1. Therefore, sublimation growth apparatus 1 can also be called a manufacturing apparatus for producing silicon carbide single crystals, and a method for producing silicon carbide single crystals can be carried out using this sublimation growth apparatus 1.

[0020] (Configuration of single crystal generating unit 10) The single crystal growing unit 10 includes a chamber 11, a container 20 containing raw material B, a support member 30 supporting a seed crystal A, induction heating sources 41-43, and a resistance heating source 44. The induction heating sources 41-43 and the resistance heating source 44 heat the raw material B contained in the container 20 to its sublimation temperature. The resistance heating source 44 can be used as a first heating source, and the induction heating sources 41-43 can be used as a second heating source. The chamber 11 is a water-cooled chamber made of, for example, quartz, and is airtight enough to maintain a vacuum state inside. A vacuum device (high vacuum exhaust device) for vacuuming is connected to the chamber 11 (not shown), and the inside of the chamber 11 is evacuated by the vacuum device before starting single crystal production. The chamber 11 also includes a water channel (not shown) through which cooling water flows.

[0021] Container 20 is a source container for use in sublimation growth apparatus 1, and is entirely housed within chamber 11. As shown in FIGS. 2 to 4, container 20 has bottom wall 21 and peripheral wall 22. Bottom wall 21 is made of bottom plate material 21A that is circular in plan view, and is installed within chamber 11 so that bottom plate material 21A is horizontal. A vertical line passing through the radial center of bottom plate material 21A becomes axis 200 of container 20, and container 20 has a rotationally symmetrical shape with axis 200 as the axis of symmetry.

[0022] 4, an annular portion 21a that protrudes upward and extends continuously in the circumferential direction is integrally formed on the peripheral edge of the bottom plate material 21A. The integral formation of the annular portion 21a improves the rigidity of the bottom plate material 21A. A lower protrusion 21b that protrudes upward and extends continuously in the circumferential direction is formed on the outer peripheral side of the upper part of the annular portion 21a.

[0023] A through-hole 21c is formed in the center of the bottom plate material 21A, penetrating in the up-down direction, which is the thickness direction of the bottom plate material 21A. The through-hole 21c is circular, and the radial center of the through-hole 21c coincides with the radial center of the bottom plate material 21A. A recess 21d is provided on the upper surface (inner surface of the container) of the bottom plate material 21A. This recess 21d extends in an annular shape so as to surround the through-hole 21c. In addition, a protrusion 21e that protrudes downward is formed on the lower surface (outer surface of the container) of the bottom plate material 21A. The protrusion 21e also extends in an annular shape so as to surround the through-hole 21c.

[0024] As shown in Fig. 1, peripheral wall 22 is disposed on bottom plate 21A and is arranged within annular induction heating sources 41-43. As shown in Figs. 2-4, peripheral wall 22 has an annular shape in plan view and is configured by connecting a plurality of peripheral wall constituent members 22A-22G made of a conductive material in the vertical direction. In this embodiment, seven peripheral wall constituent members 22A-22G are combined to form cylindrical peripheral wall 22, but the number of peripheral wall constituent members is not limited to seven and may be any number of six or less, or any number of eight or more.

[0025] Of the peripheral wall constituent members 22A to 22G, the lowest one is designated as the first peripheral wall constituent member 22A, the one connected to the first peripheral wall constituent member 22A while overlapping it is designated as the second peripheral wall constituent member 22B, the one connected to the second peripheral wall constituent member 22B while overlapping it is designated as the third peripheral wall constituent member 22C, the one connected to the third peripheral wall constituent member 22C while overlapping it is designated as the fourth peripheral wall constituent member 22D, the one connected to the fourth peripheral wall constituent member 22D while overlapping it is designated as the fifth peripheral wall constituent member 22E, the one connected to the fifth peripheral wall constituent member 22E while overlapping it is designated as the sixth peripheral wall constituent member 22F, and the one connected to the sixth peripheral wall constituent member 22F while overlapping it is designated as the seventh peripheral wall constituent member 22G. The first to seventh peripheral wall constituent members 22A to 22G are members of the same shape and size, i.e., the same members. This allows the peripheral wall components 22A to 22G to be constructed using common materials, thereby reducing costs.

[0026] As shown in Fig. 4, a first recess 22a is formed on the outer peripheral side of the lower portion of the first peripheral wall component 22A, and receives the lower protrusion 21b of the bottom plate material 21A. The first recess 22a extends continuously in the circumferential direction of the first peripheral wall component 22A. When the lower protrusion 21b of the bottom plate material 21A is received in the first recess 22a, the two are fitted together, and relative radial movement of the first peripheral wall component 22A with respect to the bottom plate material 21A is prevented. This recess-protrusion fit also improves the airtightness of the container 20. The same applies to the joining structure of the peripheral wall components 22A to 22G.

[0027] A first protruding portion 22b that protrudes upward and extends in the circumferential direction is formed on the outer peripheral side of the upper portion of the first peripheral wall component 22A. The shape and size of this first protruding portion 22b are the same as the shape and size of the lower protruding portion 21b of the bottom plate material 21A.

[0028] A second recess 22c is formed on the outer peripheral side of the lower part of the second peripheral wall component 22B, and receives the first protrusion 22b of the first peripheral wall component 22A. The shape and size of the second recess 22c are the same as those of the first recess 22a. When the first protrusion 22b of the first peripheral wall component 22A is received in the second recess 22c of the second peripheral wall component 22B, they are fitted together, and radial movement of the second peripheral wall component 22B relative to the first peripheral wall component 22A is prevented.

[0029] Similarly, a second protruding portion 22d that protrudes upward and extends circumferentially is formed on the outer peripheral side of the upper portion of the second peripheral wall component member 22B, and a third recessed portion 22e that accommodates the second protruding portion 22d of the second peripheral wall component member 22B is formed on the outer peripheral side of the lower portion of the third peripheral wall component member 22C. The same is true for the third to seventh peripheral wall component members 22C to 22G. This prevents the first to seventh peripheral wall component members 22A to 22G from moving radially relative to each other, thereby forming the peripheral wall portion 22 having a predetermined shape.

[0030] The bottom plate material 21A and the first to seventh peripheral wall constituent members 22A to 22G are made of a conductive material. The conductive material is made of, for example, high-purity graphite with an extremely small amount of impurities. The resistivity of this conductive material is 10 -5 Ωcm or more 10 -2 The non-resistivity is Ωcm or less. By setting the non-resistivity value within this range, eddy currents can be efficiently generated during induction heating by the induction heating sources 41 to 43 described below, thereby increasing the heating efficiency of the raw material B. Graphite may contain trace amounts of impurities, such as B, Na, K, Si, Mg, Al, Fe, and Ca. Even if trace amounts of these elements are contained, this does not significantly affect the heating efficiency.

[0031] In this embodiment, the first to seventh peripheral wall constituent members 22A-22G are made of the same material, but this is not limiting. For example, the peripheral wall portion 22 may be formed by vertically connecting the first to seventh peripheral wall constituent members 22A-22G that have different thicknesses or vertical dimensions. That is, if the first to seventh peripheral wall constituent members 22A-22G have different thicknesses or vertical dimensions, the eddy current density during induction heating by the induction heating sources 41-43 will change, and it will become possible to control the heating temperature depending on the location of the container 20.

[0032] Furthermore, because the container 20 is made up of the bottom plate material 21A and the plurality of peripheral wall constituent members 22A-22G, each part is smaller than when they are integrally molded, making manufacturing easier. Furthermore, if any of the bottom plate material 21A or the plurality of peripheral wall constituent members 22A-22G is damaged, only the damaged member needs to be replaced, reducing maintenance costs.

[0033] The container 20 is provided with a cover member 23 for covering the resistance heating source 44 and a plurality of raw material pods 24. The cover member 23 has a cylindrical portion 23a and an upper plate portion 23b, and is entirely made of the above-mentioned conductive material. A flange portion 23c is formed at the lower end of the cylindrical portion 23a, protruding radially outward and extending continuously in the circumferential direction. This flange portion 23c is adapted to fit into a recessed portion 21d in the bottom plate material 21A. With the flange portion 23c fitted into the recessed portion 21d, the cover member 23 is prevented from moving radially relative to the bottom plate material 21A.

[0034] The inner diameter of the cylindrical portion 23a is set to be the same as the inner diameter of the through-hole 21c of the bottom plate material 21A. The axis of the cylindrical portion 23a coincides with the axis 200 of the container 20, and the cylindrical portion 23a is disposed in the center of the container 20 in a plan view. The height of the cylindrical portion 23a is set to be the same as or higher than the height of the raw material pod 24. The upper plate portion 23b is provided at the upper end of the cylindrical portion 23a, and the upper end opening of the cylindrical portion 23a is closed by the upper plate portion 23b. On the other hand, the lower end of the cylindrical portion 23a opens downward, and as a result, the cover member 23 is only open downward.

[0035] The raw material pods 24 are components that contain the raw material B, and are placed on the upper surface of the bottom plate material 21A as shown in FIG. 5. In this embodiment, six raw material pods 24 are arranged at equal intervals around the through-hole 21c, i.e., around the axis 200 of the container 20. The number of raw material pods 24 is not limited to six, and may be any number of five or less, or any number of seven or more. Furthermore, the raw material pods 24 do not have to be arranged at equal intervals, and may also be arranged at uneven intervals.

[0036] All six raw material pods 24 are constructed from materials of the same shape and size, which allows the raw material pods 24 to be constructed from common materials, thereby reducing costs and making it possible to uniformly heat the raw material B in each raw material pod 24.

[0037] 6, each raw material pod 24 includes a pod body 24a and a lid member 24b. The pod body 24a and the lid member 24b are entirely made of the conductive material. The pod body 24a has a cylindrical shape with a bottom, and its outer diameter is set to be smaller than the outer diameter of the cylindrical portion 23a of the cover member 23. The outer diameter of the pod body 24a may be the same as the outer diameter of the cylindrical portion 23a of the cover member 23, or may be larger than the outer diameter of the cylindrical portion 23a.

[0038] The height of the pod body 24a is set to be approximately the same as the height of the cylindrical portion 23a of the cover member 23. In other words, the height dimensions of the pod body 24a and the cylindrical portion 23a are set so that the height of the pod body 24a and the height of the cylindrical portion 23a are approximately the same. Note that the height of the pod body 24a may be higher or lower than the height of the cylindrical portion 23a of the cover member 23.

[0039] The lid member 24b is provided to cover the upper end of the pod body 24a and is composed of a circular plate-shaped member. The lid member 24b is provided with an exhaust port 24c that penetrates the lid member 24b in the vertical direction and is used to exhaust sublimation gas generated by sublimation of the raw material B in the pod body 24a. In other words, by providing the exhaust port 24c in the upper part of the raw material pod 24, the sublimation gas generated in the pod body 24a can be efficiently released to the outside of the raw material pod 24. The exhaust port 24c opens at the upper end of the raw material pod 24, and is therefore an upper-end opening. Note that the lid member 24b may be provided as needed, and the lid member 24b may be omitted.

[0040] The exhaust port 24c is located at a position radially eccentric from the center of the lid member 24b. In this embodiment, the exhaust port 24c is located on the side of the lid member 24b that is closer to the axis 200 of the container 20. The exhaust port 24c may be located at the center of the lid member 24b, or may be located on the side away from the axis 200 of the container 20. The lid member 24b may have only one exhaust port 24c, or two or more exhaust ports 24c.

[0041] The exhaust port 24c has a circular shape. The diameter of the exhaust port 24c is set in the range of 1 mm to 30 mm. That is, if the diameter of the exhaust port 24c is smaller than 1 mm, the exhaust port 24c is likely to become clogged, hindering the growth of the single crystal. On the other hand, if the diameter of the exhaust port 24c is larger than 30 mm, large vapors are likely to be released from the raw material pod 24, which is likely to deteriorate the quality of the single crystal. Therefore, by setting the diameter of the exhaust port 24c in the above range, stable growth of the single crystal and improved quality can be achieved.

[0042] In this embodiment, the heat sources for heating raw material B include a plurality of induction heating sources 41 to 43 arranged at intervals from one another, and at least one resistance heating source 44 arranged at a location separate from the induction heating sources 41 to 43. Details of the heat sources will be described below.

[0043] The induction heating sources 41 to 43 include an upper induction heating source (first induction heating source) 41, an intermediate induction heating source (second induction heating source) 42, and a lower induction heating source 43. The upper induction heating source 41, the intermediate induction heating source 42, and the lower induction heating source 43 each have an induction heating coil made of a conductor formed in a circular ring shape with a diameter larger than the outer diameter of the chamber 11, and are configured so that induction heating can be applied to the inner members by passing a current through the induction heating coil. The upper induction heating source 41, the intermediate induction heating source 42, and the lower induction heating source 43 can be fixed to the chamber 11 by fixing members (not shown).

[0044] The upper induction heating source 41 is disposed outside the peripheral wall 22 of the container 20 near the upper end, and is disposed so as to surround the peripheral wall 22 from the outside (outside the chamber 11). The height (vertical position) of the upper induction heating source 41 is higher than the upper end of the raw material pod 24 and the upper end of the cover member 23, and is substantially the same height as the seventh peripheral wall constituent member 22G. The lower induction heating source 43 is disposed outside the peripheral wall 22 of the container 20 near the lower end, and is disposed so as to surround the peripheral wall 22 from the outside (outside the chamber 11). The height of the lower induction heating source 43 is substantially the same height as the lower end of the raw material pod 24 and the lower end of the cover member 23, and is substantially the same height as the first peripheral wall constituent member 22A. The intermediate induction heating source 42 is disposed outside the peripheral wall 22 between the lower induction heating source 43 and the upper induction heating source 41. The height of the intermediate induction heating source 42 is set to be approximately the same as the upper end of the raw material pod 24 and the upper end of the cover member 23 .

[0045] A gap is formed between the upper induction heating source 41 and the intermediate induction heating source 42, and the upper induction heating source 41 and the intermediate induction heating source 42 are arranged vertically apart by a first predetermined distance. A gap is also formed between the intermediate induction heating source 42 and the lower induction heating source 43, and the intermediate induction heating source 42 and the lower induction heating source 43 are arranged vertically apart by a second predetermined distance. The first predetermined distance and the second predetermined distance may be the same or different.

[0046] The heating capacity per unit time of the upper induction heating source 41, the intermediate induction heating source 42, and the lower induction heating source 43 can be set as desired depending on the diameter and number of turns of the conductor wires used, the value of the current flowing through the conductor wires, and other factors. The heating capacity per unit time of the lower induction heating source 43 is set higher than that of the upper induction heating source 41, and the heating capacity per unit time of the lower induction heating source 43 is set higher than that of the intermediate induction heating source 42. In other words, of the upper induction heating source 41, the intermediate induction heating source 42, and the lower induction heating source 43, the lower induction heating source 43 has the highest heating capacity. The heating capacity of the upper induction heating source 41 and the intermediate induction heating source 42 may be the same, or the upper induction heating source 41 or the intermediate induction heating source 42 may be higher.

[0047] The number of induction heating sources is not limited to three, but may be two or less, or may be four or more.

[0048] The resistance heating source 44 is disposed so as to protrude from the bottom wall 21 of the container 20 into the space surrounded by the peripheral wall 22. Specifically, the resistance heating source 44 has a conductor that generates Joule heat, and the conductor is formed so as to extend vertically. The vertical dimension of the resistance heating source 44 is set to be longer than the combined vertical dimensions of the multiple peripheral wall components 22A-22G. The resistance heating source 44 is disposed so that its longitudinal direction faces the vertical direction and extends from within the through-hole 21c of the bottom plate 21A to the cylindrical portion 23a of the cover member 23. The resistance heating source 44 is fixed to the chamber 11 or the like by a fixing member (not shown) so that the resistance heating source 44 is located in the radial center of the cylindrical portion 23a. As a result, the resistance heating source 44 is disposed in the central portion of the container 20 in a plan view. Furthermore, the positional relationship between the plurality of raw material pods 24 and the resistance heating source 44 is such that the plurality of raw material pods 24 are arranged to surround the resistance heating source 44 .

[0049] The upper end of the resistance heating source 44 arranged as described above is positioned at the same height as the upper portion of the raw material pod 24, and the lower end of the resistance heating source 44 is positioned below the lower portion of the raw material pod 24. This allows heat radiated from the resistance heating source 44 to be transmitted from the upper portion to the lower portion of the raw material pod 24 via the cover member 23. The resistance heating source 44 is also configured to radiate heat in any horizontal direction. This allows multiple raw material pods 24 to be heated in the same manner.

[0050] As shown in Fig. 1, the support member 30 is a member that supports the seed crystal A facing downward at the upper part of the vessel 20 inside the vessel 20. Specifically, the support member 30 is contained in the upper part of the chamber 11 and is made of a circular plate material arranged so as to cover the upper end opening of the vessel 20, and the seed crystal A is provided on the lower surface of the support member 30. Therefore, the exhaust port 24c of each raw material pod 24 is arranged below the seed crystal A, and the seed crystal A and each exhaust port 24c are positioned opposite each other in the vertical direction. The growth direction of the seed crystal A is downward.

[0051] The single crystal generating section 10 is equipped with a rotation mechanism 45 that rotates the support member 30 around an axis extending in the vertical direction. The rotation mechanism 45 is equipped with an electric motor 45a and a rotation shaft 45b to which the output of the electric motor 45a is transmitted. The rotation shaft 45b extends vertically and is disposed so as to penetrate the upper wall of the chamber 11 in the vertical direction, with the lower portion of the rotation shaft 45b fixed to the radial center of the support member 30. A bearing member 11a that rotatably supports the rotation shaft 45b is provided on the upper wall of the chamber 11. This bearing member 11a has a sealing mechanism that can maintain a vacuum state within the chamber 11 and is configured to withstand heat radiated from a heat source.

[0052] The output of the electric motor 45a is transmitted to the rotation shaft 45b via a transmission gear 45c, a transmission chain (not shown), etc. As a result, the support member 30 rotates above the exhaust port 24c of each ingredient pod 24. The rotation speed of the support member 30 can be changed by controlling the electric motor 45a with the control device 50, and the rotation direction of the support member 30 and the timing of starting and stopping the rotation can also be changed by controlling the electric motor 45a with the control device 50. Note that the support member 30 may be driven directly by the electric motor 45a without using the transmission gear 45c, transmission chain, etc.

[0053] A gas outlet 25 for discharging sublimation gas of the raw material is provided in a portion of the container 20 above the seed crystal A. Positioning the gas outlet 25 above the seed crystal A allows sublimation gas generated below the seed crystal A to flow upward and be guided to the seed crystal A. The gas outlet 25 is formed between the periphery of the support member 30 and the peripheral edge of the upper opening of the container 20. Although not shown, the gas outlet 25 may be formed around the seed crystal A on the support member 30. Alternatively, multiple gas outlets 25 may be formed. In this case, it is preferable to arrange the multiple gas outlets 25 at intervals in the circumferential direction of the container 20. The diameter of the gas outlet 25 can be set to the same diameter as the exhaust port 24c of the raw material pod 24. Alternatively, the gas outlet 25 may be a slit-like opening that is long in the circumferential direction of the container 20.

[0054] The single crystal growing unit 10 includes an upper temperature sensor (first temperature sensor) 46 and a lower temperature sensor (second temperature sensor) 47 that acquire the temperature of the container 20 and output the acquired temperature data to the control device 50. The upper temperature sensor 46 and the lower temperature sensor 47 are infrared thermometers that measure the temperature based on infrared radiation emitted from an object without contacting the object. The upper temperature sensor 46 is disposed opposite the upper wall of the chamber 11 and directly measures the temperature of the upper wall of the chamber 11. However, since the upper wall of the chamber 11 and the upper part of the container 20 are close to each other, the temperature of the upper part of the container 20 can be acquired by measuring the temperature of the upper wall of the chamber 11. For example, by determining the temperature relationship between the upper wall of the chamber 11 and the upper part of the container 20 in advance through experiments, the temperature of the upper part of the container 20 can be estimated simply by measuring the temperature of the upper wall of the chamber 11. The estimated temperature is used as the temperature of the upper part of the container 20 in the PID control described below.

[0055] The lower temperature sensor 47 is disposed so as to face the lower wall of the chamber 11, and directly measures the temperature of the lower wall of the chamber 11, but similarly to the upper temperature sensor 46, by determining the relationship between the lower wall of the chamber 11 and the lower part (bottom wall 21) of the container 20 in advance through experiments or the like, it becomes possible to estimate the temperature of the lower part of the container 20 simply by measuring the temperature of the lower wall of the chamber 11. The estimated temperature is used in PID control, which will be described later, as the temperature state of the lower part of the container 20.

[0056] If a temperature sensor capable of directly measuring the temperature of the container 20 is available, the temperature state of the container 20 can be accurately obtained by using that temperature sensor. Even when the temperature state is obtained by estimation using the upper temperature sensor 46 and the lower temperature sensor 47, it is possible to control each heat source so that the raw material B can be sublimated as intended. The number of temperature sensors is not limited to two, but may be one, or three or more. The upper temperature sensor 46 and the lower temperature sensor 47 are positioned to measure temperatures at locations distant from the induction heating sources 41-43, thereby ensuring accurate temperature estimation of the container 20. Heating control of the upper induction heating source 41 may be performed based on the output value of the upper temperature sensor 46, or heating control of the induction heating sources 41-43 and the resistance heating source 44 may be performed based on the output values ​​of both the upper temperature sensor 46 and the lower temperature sensor 47. A temperature sensor may also be provided to obtain the temperature state of the side surface of the container 20.

[0057] (Configuration of control device 50) The control device 50 is a device for controlling the induction heating sources 41 to 43, the resistance heating source 44, and the rotation mechanism 45, and includes a vacuum pressure sensor 51, a gas flow sensor 52, a PID control unit 53, a phase control unit 54, a power control module 55, and power supply circuits 56 to 58. The PID control unit 53 and the phase control unit 54 are configured by a combination of hardware such as a microcomputer and software executable by the hardware. The phase control unit 54, the power control module 55, and the power supply circuits 56 to 58 are connected to the PID control unit 53.

[0058] The vacuum pressure sensor 51 is a sensor that detects the pressure inside the chamber 11, that is, whether the pressure inside the chamber 11 is equal to or lower than a predetermined pressure (a pressure that creates a vacuum state). In this embodiment, the vacuum state does not have to be a complete vacuum, but only needs to be a vacuum that allows high-quality single crystals to be obtained stably. In this example, for example, 10 -3 It is possible to maintain a vacuum level of less than 100 Pa.

[0059] The gas flow sensor 52 is a sensor that measures the flow rate of the gas inside the chamber 11. The vacuum pressure sensor 51 and the gas flow sensor 52 are connected to a PID control unit 53.

[0060] The power supply circuits 56-58 include an upper power supply circuit (first power supply circuit) 56 that supplies current to the upper induction heating source 41, an intermediate power supply circuit (second power supply circuit) 57 that supplies current to the intermediate induction heating source 42, and a lower power supply circuit 58 that supplies current to the lower induction heating source 43. The upper power supply circuit 56, the intermediate power supply circuit 57, and the lower power supply circuit 58 are each composed of independent inverter circuits or the like, and the lower power supply circuit 58 is configured to be able to supply greater power than the upper power supply circuit 56 and the intermediate power supply circuit 57. For example, the lower power supply circuit 58 is configured to be able to supply approximately 40 kW to 60 kW of power to the lower induction heating source 43, and the upper power supply circuit 56 and the intermediate power supply circuit 57 are configured to be able to supply approximately 20 kW to 35 kW of power to the upper induction heating source 41 and the intermediate induction heating source 42. This makes it possible to produce large-diameter single crystals.

[0061] Here, if the power supplied to the induction heating sources 41-43 is large as described above, the heat generation capacity increases, which in turn increases the electrical capacity of the power supply and matching box, placing a limit on the output frequency of the power supply, which may result in a deterioration in the efficiency of energy transmission to the container 20 and a drop in heating efficiency. In response to this, in this embodiment, the phase difference between the voltages of the power output from the multiple independent power supply circuits 56-58 is set to zero, thereby suppressing magnetic field interference between the induction heating sources 41-43.

[0062] That is, the control device 50 is configured to zero the difference in phase between the voltage applied to the upper induction heating source 41 by the upper power supply circuit 56, the voltage applied to the intermediate induction heating source 42 by the intermediate power supply circuit 57, and the voltage applied to the lower induction heating source 43 by the lower power supply circuit 58. To achieve this, the upper power supply circuit 56, the intermediate power supply circuit 57, and the lower power supply circuit 58 are connected to a phase control unit 54 of the control device 50 so as to be able to send and receive signals. The phase control unit 54 has a phase synchronization circuit. The phase synchronization circuit is configured as a phase-locked loop (PLL) that matches the phase of an input signal with the phase of an output signal, and performs control to zero the phase difference in the voltages output from the upper power supply circuit 56, the intermediate power supply circuit 57, and the lower power supply circuit 58 based on signals input from the upper power supply circuit 56, the intermediate power supply circuit 57, and the lower power supply circuit 58. The power control module 55 is used to supply power to the resistance heating source 44.

[0063] The PID control unit 53 is connected to the upper temperature sensor 46, the lower temperature sensor 47, the vacuum pressure sensor 51, and the gas flow sensor 52. The PID control unit 53 can obtain the current temperature state of the container 20 based on the values ​​output from the upper temperature sensor 46 and the lower temperature sensor 47. Since the container 20 contains raw material B and is made of a material with good thermal conductivity, the temperature state of the container 20 is approximately the same as the temperature state of raw material B. Therefore, the PID control unit 53 can also indirectly obtain the temperature state of raw material B.

[0064] The PID control unit 53 determines whether a vacuum state exists inside the chamber 11 based on the value output from the vacuum pressure sensor 51. The PID control unit 53 also acquires the gas flow rate inside the chamber 11 based on the value output from the gas flow sensor 52. A control panel 60 is connected to the PID control unit 53. The control panel 60 is provided with operation switches 60a for performing various settings and an operation switch 60a for starting / stopping operation. A user can set the target temperature (set temperature) of the container 20, the temperature rise rate of the container 20, the heating time of the container 20, etc. by operating the operation switch 60a of the control panel 60. The set target temperature, temperature rise rate, heating time, etc. are stored in the control device 50, memory unit 61, etc. The target temperature is a temperature at which silicon carbide powder can be sublimated, and is set to, for example, 2000°C or higher.

[0065] The control device 50 is configured to simultaneously energize the induction heating sources 41-43 and the resistance heating source 44. When controlling the energization, the control device 50 controls the induction heating sources 41-43 and the resistance heating source 44 by executing PID control based on a preset set temperature and the temperature state of the container 20 output from the temperature sensors 46, 47. That is, the control device 50 determines the deviation between the set temperature and the temperature state of the container 20, and calculates the control amount by combining proportional control, integral control, and differential control. The output values ​​of the upper temperature sensor 46 and the lower temperature sensor 47, the power control value, etc. are stored and managed in a memory unit 61 as time-series data.

[0066] The control procedure by the control device 50 will be described below based on the flowchart shown in Fig. 7. This flow starts when the user operates the operation switch 60a on the operation panel 60 to set the target temperature, heating rate, heating time, etc., and the production of a single crystal is started. The elapsed time from the start is measured, and the above flow is interrupted or terminated when the heating time set by the user has elapsed. The above flow is also interrupted or terminated when the user performs an operation to stop heating (operation to stop production).

[0067] In step S1 after starting, a current temperature measurement process is performed. In the current temperature measurement process, the PID control unit 53 reads the current measurement values ​​measured by the upper temperature sensor 46 and the lower temperature sensor 47. The current measurement value indicates the temperature of the container 20 (estimated temperature of the container), i.e., the temperature of the raw material B (estimated temperature of the raw material). In step S2, settings such as the target temperature, heating rate, and heating time set by the user on the operation panel 60 are read. The order of steps S1 and S2 may be reversed, or steps S1 and S2 may be performed simultaneously.

[0068] In step S3, the PID control unit 53 reads the output set values ​​of the upper, middle, and lower power supply circuits 56 to 58. In step S4, the PID control unit 53 reads the output set value of the power control module 55. Each output set value is set to a larger value the higher the target temperature is relative to the current temperature acquired in step S1, for example, and the faster the temperature rise rate is, the larger the value is. Each output set value can be stored in the memory unit 61 or the like. The order of steps S3 and S4 may be reversed, or steps S3 and S4 may be executed simultaneously.

[0069] In step S5, PID control unit 53 executes PID control. In step S6 of the initial flow after start, PID control unit 53 controls upper, middle, and lower power supply circuits 56-58 so as to output the power of the output set value read in step S3, and also controls power control module 55 so as to output the power of the output set value read in step S4.

[0070] As a result, current flows through the upper induction heating source 41, the intermediate induction heating source 42, and the lower induction heating source 43, generating eddy currents in the peripheral wall 22 of the container 20 and generating heat. At this time, the phase difference between the voltages output from the power supply circuits 56-58 is zero, suppressing magnetic field interference between the induction heating sources 41-43 and improving heating efficiency. Furthermore, because the peripheral wall constituent members 22A-22G and the induction heating sources 41-43 are all annular, eddy currents generated in each of the peripheral wall constituent members 22A-22G can be confined within the peripheral wall constituent members 22A-22G, making the eddy currents uniform in the circumferential direction. This results in a uniform temperature distribution within the container 20.

[0071] The heat generated in the peripheral wall portion 22 is transferred to the raw material pod 24 accommodated therein, thereby heating the raw material pod 24. As the raw material pod 24 is heated, the raw material B in the raw material pod 24 is heated.

[0072] Simultaneously with the supply of power to the induction heating sources 41 to 43, power is also supplied from the power control module 55 to the resistance heating source 44. When the resistance heating source 44 generates heat, the heat radiated from the resistance heating source 44 is transferred to the plurality of raw material pods 24 via the cover member 23, and the raw material B in the raw material pod 24 is heated.

[0073] In step S8, similarly to step S1, a measurement process of the current temperature is performed, and the PID control unit 53 acquires the measurement result. In step S9, the PID control unit 53 performs a comparison process to compare the target temperature read in step S2 with the measured temperature measured in step S8. If the comparison process in step S9 shows a deviation between the target temperature and the measured temperature, the process proceeds to step S6, and the PID control unit 53 controls the upper, middle, and lower power supply circuits 56 to 58 and the power control module 55 so as to continue outputting power of the current output command value.

[0074] On the other hand, if the result of the comparison process in step S9 shows that there is no deviation between the target temperature and the measured temperature, the process proceeds to step S5, where the PID control unit 53 executes PID control to control the upper, middle, and lower power supply circuits 56 to 58 and the power control module 55.

[0075] Before the target temperature is reached, the control device 50 activates the electric motor 45a of the rotation mechanism 45. This allows the seed crystal A to rotate before the raw material B starts to sublimate. Since the resistance heating source 44 is located directly below the seed crystal A, heat radiated from the resistance heating source 44 is also transmitted to the seed crystal A via the upper plate portion 23b of the cover member 23. This allows the temperature of the seed crystal A to be maintained within a temperature range that promotes the growth of a single crystal.

[0076] Since the raw material B is housed in multiple raw material pods 24, the raw material B can be heated on the inner wall surface of each raw material pod 24. This increases the area over which the raw material B is heated. When the temperature of the raw material B in the raw material pod 24 reaches the sublimation temperature, the raw material B sublimes, generating sublimation gas within the raw material pod 24. The sublimation gas generated within the raw material pod 24 is exhausted upward through an exhaust port 24c provided in the upper portion of the raw material pod 24. The sublimation gas exhausted from the raw material pod 24 flows toward the seed crystal A located directly above. At this time, since a gas exhaust port 25 is located around the seed crystal A at the top of the container 20, the flow of the sublimation gas is directed toward the gas exhaust port 25, making it more likely to hit the seed crystal A. This allows a silicon carbide single crystal to grow. The silicon carbide single crystal may have, for example, a columnar shape.

[0077] This will be explained with reference to Figures 8A and 8B. Figure 8A is a diagram showing the results of a simulation of the flow of thermal fluid near the seed crystal A when there is no gas outlet. In this case, fluid compression occurs near the seed crystal A due to a large temperature difference, causing turbulence. The generation of turbulence hinders stable growth of a single crystal.

[0078] 8B is a diagram schematically illustrating the results of a simulation of the flow of the thermal fluid near the seed crystal A when the gas outlet 25 is provided. In this case, the gas outlet 25 is located to the side of the seed crystal A, so the thermal fluid (sublimation gas) flowing from below the seed crystal A to above flows along the surface of the seed crystal A while maintaining a laminar flow state, and reaches the gas outlet 25. This allows the single crystal to grow stably. Furthermore, because the seed crystal A is rotating at this time, the temperature difference near the seed crystal A is reduced, which also makes it easier to maintain a laminar flow state.

[0079] (Variation) The above-described embodiment is merely illustrative in all respects and should not be construed as limiting. Furthermore, various modifications and variations within the scope of equivalents of the claims are all within the scope of the present invention. The size and shape of the vessel 20 can be set arbitrarily, and the present invention can also be applied to the production of small-diameter single crystals of less than 6 inches. The heating range of the induction heating source is not limited to the illustrated range; for example, the bottom wall 21 of the vessel 20 may be heated by the induction heating source. The heating range of the resistance heating source is not limited to the illustrated range; for example, the peripheral wall 22 of the vessel 20 may be heated by the resistance heating source.

[0080] For example, as in Modification 1 of the embodiment shown in FIG. 9, a plurality of cover members 23 may be provided. The cover members 23 are provided at intervals in the circumferential direction so as to surround the axis 200 of the container 20. A resistance heating source 44 is housed inside each cover member 23. This makes the temperature distribution inside the container 20 even more uniform. In other words, the number of resistance heating sources 44 is not limited to one, and a plurality of resistance heating sources 44 can be provided for one container 20. When a plurality of resistance heating sources 44 are provided, they can be arranged in point symmetry with the axis 200 of the container 20 as the center of symmetry.

[0081] 10 , the cover member 23 may be radially offset from the axis 200 of the container 20. Since the resistance heating source 44 is housed inside the cover member 23, the resistance heating source 44 is also radially offset from the axis 200 of the container 20.

[0082] (Effects of the embodiment) As described above, according to this embodiment, the provision of multiple induction heating sources 41-43 that are energized simultaneously increases the heat capacity, so that even in a large vessel 20 capable of growing a single crystal, such as one with a 6-inch or 8-inch diameter, the raw material B inside can be heated to 2000°C or higher and sublimated. In addition, since the multiple induction heating sources 41-43 are arranged at intervals from one another, multiple locations on the vessel 20 are heated simultaneously by the multiple induction heating sources 41-43, and the vessel 20 is also heated simultaneously from the inside by the resistance heating source 44 arranged corresponding to the interior of the vessel 20. This makes it possible to achieve a more uniform temperature distribution inside the vessel 20.

[0083] Furthermore, since induction heating sources 41-43 are arranged to surround the outside of peripheral wall 22 of container 20, when current is applied to induction heating sources 41-43, eddy currents are generated in peripheral wall constituent members 22A-22G that make up peripheral wall 22, causing each peripheral wall constituent member 22A-22G to generate heat and heat raw material B. At this time, because peripheral wall constituent members 22A-22G and induction heating sources 41-43 are both annular, the eddy currents generated in each peripheral wall constituent member 22A-22G can be confined within the peripheral wall constituent members 22A-22G, making the eddy currents uniform in the circumferential direction. This also uniforms the temperature distribution inside container 20.

[0084] Furthermore, because the seed crystal A is supported facing downward by the support member 30, the growth direction of the single crystal coincides with the direction of gravity, and gravity does not hinder the growth of the single crystal. Furthermore, the seed crystal A can be rotated by rotating the support member 30 using the rotation mechanism 45. This suppresses turbulence in the thermal fluid near the seed crystal A, resulting in a laminar flow of the thermal fluid, making it less likely for defects to be included in the single crystal.

[0085] Furthermore, because raw material B is divided and stored in multiple raw material pods 24 and heated on the inner wall surface of each raw material pod 24, the area over which raw material B is heated is larger than when raw material B is stored directly in a large-diameter container 20. This allows raw material B to be sublimated efficiently and the sublimation state to be stabilized, and more raw material B can be heated to the sublimation temperature, thereby increasing the utilization rate of raw material B. [Industrial Applicability]

[0086] As described above, the present disclosure can be used when growing a single crystal on a seed crystal by sublimating a raw material such as silicon carbide. [Explanation of symbols]

[0087] 1 Sublimation growth device 20 containers 24 ingredient pods 24c exhaust port 25 Gas outlet 30 Support member 41 Upper induction heating source 42 Intermediate induction heating source 43 Lower induction heating source 44 Resistance heating source 45 Rotation mechanism 46, 47 Temperature sensor 50 Control device A seed crystal B Raw materials

Claims

1. A sublimation growth apparatus comprising: a chamber; a container housed in said chamber and containing raw material with a sublimation temperature of 2000°C or higher; a support member for supporting a seed crystal facing downwards at an upper part of said container inside said container; a heat source for heating said container; and a control device for controlling said heat source, wherein said container is heated by said heat source, and said raw material is sublimated to grow a single crystal on said seed crystal, the heating source includes a plurality of induction heating sources spaced apart from one another and at least one resistance heating source located separately from the induction heating sources; The plurality of induction heating sources are arranged so as to surround the peripheral wall portion constituting the container from the outside, the plurality of induction heating sources include a lower induction heating source disposed outside the peripheral wall portion near a lower end thereof, an upper induction heating source disposed outside the peripheral wall portion near an upper end thereof, and an intermediate induction heating source disposed outside the peripheral wall portion between the lower induction heating source and the upper induction heating source; a heating capacity per unit time of the lower induction heating source is set higher than a heating capacity per unit time of the upper induction heating source and a heating capacity per unit time of the intermediate induction heating source; the resistance heating source is disposed so as to protrude from a bottom wall portion constituting the container into a space surrounded by the peripheral wall portion, a cover member for covering the resistance heating source and a plurality of raw material pods for accommodating the raw material are provided inside the container; the control device includes a lower power supply circuit that supplies current to the lower induction heating source, an upper power supply circuit that supplies current to the upper induction heating source, and an intermediate power supply circuit that supplies current to the intermediate induction heating source, and is configured to set a difference between a phase of a voltage applied to the lower induction heating source by the lower power supply circuit, a phase of a voltage applied to the upper induction heating source by the upper power supply circuit, and a phase of a voltage applied to the intermediate induction heating source by the intermediate power supply circuit to zero, and to simultaneously energize the plurality of induction heating sources and the resistance heating source.

2. 2. The sublimation growth apparatus according to claim 1, a temperature sensor that acquires the temperature state of the container and outputs the acquired temperature state to the control device; the control device is configured to control the plurality of induction heating sources and the resistance heating source by performing PID control based on a preset temperature and the temperature state of the container output from the temperature sensor.

3. 2. The sublimation growth apparatus according to claim 1, The sublimation growth apparatus is characterized in that the resistance heating source is disposed in the center of the container in a plan view.

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