Silicon carbide crystal growth device and growth method

Abstract

The invention provides a silicon carbide crystal growing device and method.The silicon carbide crystal growing device comprises a crucible, a collecting box and a lifting rod, specifically, the crucible comprises a raw material area and a growing area, a first through hole is formed in the bottom end face of the raw material area, and a seed crystal support used for fixing seed crystals is arranged on the top wall of the growing area; the collecting box is arranged at the bottom of the crucible, a second through hole is formed in the top end face of the collecting box, the lifting rod is connected with the crucible, and the lifting rod can drive the crucible to rotate so that the second through hole can coincide with or be staggered from the first through hole. Compared with the prior art, the silicon carbide crystal growing device can reduce carbon particles mingled in upflow in the raw material area in the silicon carbide crystal growing process, and effectively improves the crystal quality.

Description

Technical Field

[0001] The present invention belongs to the technical field of crystal growth equipment, and in particular relates to a silicon carbide crystal growth device and a growth method. Background Art

[0002] As a third-generation semiconductor material, silicon carbide has characteristics such as wider modern width, higher thermal conductivity, and greater electron saturation drift rate, and has obvious advantages in the fields of new energy vehicles, photovoltaic power generation, rail transportation, smart grid, etc. Silicon carbide has a complex crystal structure and has multiple crystal forms such as 3C-SiC, 4H-SiC, 6H-SiC, and 15R-SiC. Among them, 4H-SiC is widely used in power devices due to its high breakdown field strength, high saturation electron drift rate and high temperature stability.

[0003] The growth technologies of silicon carbide crystals mainly include physical vapor transport (PVT), high temperature chemical vapor deposition (HTCVD) and liquid phase deposition (LPE). Among them, the PVT method is the mainstream technology for growing SiC single crystals. The PVT method mostly uses induction or resistance heating of graphite crucibles to sublimate silicon carbide raw materials into gaseous substances at high temperatures, and then recrystallizes at the seed crystal to form SiC crystals. Although this method has the advantages of simple equipment and low cost, the silicon carbide raw material will decompose during the heating process to form gaseous and solid carbon such as Si, Si2C, and SiC2, resulting in carbonization of the polycrystalline powder. Since the edge temperature of the crucible is relatively high, the edge carbonization is more serious. Some fine carbon particles are easily carried to the crystal growth interface with the airflow, resulting in increased carbon inclusions in the later stages of crystal growth. In addition, the decomposed silicon vapor escapes first, causing the crystal growth chamber to be in a silicon-rich state at the initial stage. The silicon vapor is corrosive and can etch the graphite parts it contacts. The corroded graphite dust is easily carried to the surface of the seed crystal by the airflow to form carbon inclusions, resulting in increased carbon inclusions in the later stages of crystal growth.

[0004] Carbon inclusion is one of the common defects in crystals and is also a highly harmful defect. The main harm of carbon inclusion is that it will cause the generation of crystal structure defects, such as micropipes, polymorphic phase transitions, and screw dislocations. In addition, carbon inclusions will also cause defects such as triangular defects in the homoepitaxial layer, further affecting the performance of SiC-based devices.

[0005] Therefore, how to overcome the above technical defects is a problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0006] In view of this, an object of the present invention is to provide a silicon carbide crystal growth device that can reduce the carbon powder ratio in the raw material area, reduce carbon wrapping, and improve crystal quality.

[0007] The core of the present invention is also to provide a method for growing silicon carbide crystals.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A silicon carbide crystal growth device, comprising:

[0010] The crucible comprises a raw material area and a growth area, wherein a first through hole is provided on the bottom end surface of the raw material area, and a seed crystal holder for fixing a seed crystal is provided on the top wall of the growth area;

[0011] A collecting box is arranged at the bottom of the crucible, and a second through hole is opened on the top surface of the collecting box;

[0012] A lifting rod is connected to the crucible, and the lifting rod can drive the crucible to rotate so that the second through hole overlaps with or staggers with the first through hole.

[0013] Optionally, a tray is further included, and the tray is fixedly connected to the collection box.

[0014] Optionally, a groove is provided at the bottom of the collection box, and a protrusion which is plugged and connected to the groove is provided on the tray.

[0015] Optionally, the first through holes are multiple and are evenly arranged in a circular shape along the bottom end surface of the raw material area;

[0016] There are a plurality of second through holes, which are evenly arranged in a circular shape along the top surface of the collecting box.

[0017] Optionally, the central angle of the arc between any two adjacent first through holes is 30°-60°, and the central angle of the arc between any two adjacent second through holes is 30°-60°.

[0018] Optionally, the first through hole is opened in an edge area close to the collection box;

[0019] The second through hole is opened in an edge area close to the raw material area.

[0020] Optionally, the height of the collection box is 10 mm-60 mm, and / or,

[0021] The diameters of the first through hole and the second through hole are both 1 mm-10 mm.

[0022] A method for growing a silicon carbide crystal, applied to a silicon carbide crystal growing device as described in any one of the above, comprising:

[0023] S100: placing silicon carbide raw materials in a raw material zone of a crucible and heating them, and when the temperature of the raw material zone is within a first preset temperature range, the first through hole of the raw material zone and the second through hole of the collecting box are in a staggered state;

[0024] S200: The temperature of the raw material zone continues to rise. When the temperature of the raw material zone is within a second preset temperature range, the lifting rod is rotated, the first through hole and the second through hole are aligned, and the carbon powder falls into the collection box under the action of gravity and airflow.

[0025] Optionally, in step S200, the second preset temperature range is 2200°C-2500°C, and the radial temperature gradient from the middle to the edge of the raw material zone increases by 0.5°C / mm.

[0026] Optionally, in step S200, the temperature range of the collection box is 2200°C-2500°C, the axial temperature gradient from the lower part to the upper part of the collection box decreases by 2°C / mm, and / or,

[0027] The rotation speed of the lifting rod is 0.1° / h-3° / h.

[0028] It can be seen from the above technical scheme that, first, the silicon carbide raw material is placed in the raw material area 101 of the crucible. When the temperature of the raw material area is within the first preset temperature range, the first through hole in the raw material area and the second through hole in the collecting box are in a staggered state. At this time, the raw material area and the collecting box are isolated, and the carbonization degree of the raw material is low; after heating for a period of time, the temperature of the raw material area continues to rise. When the temperature of the raw material area reaches within the second preset temperature range, the silicon carbide raw material in the raw material area is gradually carbonized, and the carbon powder gradually increases. At this time, the lifting rod is rotated. Under the rotation action of the lifting rod, the first through hole in the raw material area and the second through hole in the collecting box gradually align and overlap until they are connected. At this time, the carbon powder in the raw material area falls into the collecting box through the overlapping first and second through holes under the action of gravity and airflow, so that the carbon powder in the raw material area is reduced. Such a reciprocating cycle can control the proportion of carbon powder in the raw material area, thereby reducing the carbon particles mixed in the rising airflow in the raw material area during the growth of silicon carbide crystals, and effectively improving the crystal quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0030] Figure 1 It is a schematic structural diagram of a silicon carbide crystal growth device disclosed in an embodiment of the present invention;

[0031] Figure 2 A schematic diagram of the structure of the first through hole distribution disclosed in an embodiment of the present invention;

[0032] Figure 3 A schematic diagram of the structure of the second through hole distribution disclosed in an embodiment of the present invention;

[0033] Figure 4 A schematic diagram of a structure in which a first through hole and a second through hole are misaligned according to an embodiment of the present invention;

[0034] Figure 5 A schematic diagram of the structure in which the first through hole and the second through hole are aligned and overlapped according to an embodiment of the present invention;

[0035] Figure 6 This is a diagram showing the encapsulation state of the grown silicon carbide crystal disclosed in the first embodiment of the present invention;

[0036] Figure 7 This is a diagram of the wrapping state of the grown silicon carbide crystal disclosed in the second embodiment of the present invention.

[0037] Description of reference numerals:

[0038] 100, crucible; 101, raw material area; 102, growth area; 103, seed crystal tray; 104, first through hole; 200, collection box; 201, second through hole; 300, lifting rod; 400, tray; 500, seed crystal. DETAILED DESCRIPTION

[0039] In view of this, the core of the present invention is to provide a silicon carbide crystal growth device, which can reduce the carbon particles contained in the rising air flow in the raw material zone during the silicon carbide crystal growth process, thereby effectively improving the crystal quality.

[0040] The core of the present invention is also to provide a method for growing silicon carbide crystals.

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Please refer to Figure 1 and Figure 7 .

[0042] Please refer to Figures 1 to 5The silicon carbide crystal growth device disclosed in the embodiment of the present invention includes a crucible 100, a collecting box 200 and a lifting rod 300, wherein the crucible 100 includes a raw material area 101 and a growth area 102, a first through hole 104 is provided on the bottom end surface of the raw material area 101, a seed crystal holder 103 for fixing a seed crystal 500 is provided on the top wall of the growth area 102, the collecting box 200 is arranged at the bottom of the crucible 100, a second through hole 201 is provided on the top surface of the collecting box 200, the lifting rod 300 is connected to the crucible 100, and the lifting rod 300 can drive the crucible 100 to rotate so that the second through hole 201 overlaps or staggers with the first through hole 104.

[0043] First, place the silicon carbide raw material in the raw material area 101 of the crucible 100. When the temperature of the raw material area 101 is within the first preset temperature range, the first through hole 104 of the raw material area 101 and the second through hole 201 of the collecting box 200 are in a staggered state. At this time, the raw material area 101 and the collecting box 200 are isolated, and the carbonization degree of the raw material is low. After heating for a period of time, the temperature of the raw material area 101 continues to rise. When the temperature of the raw material area 101 reaches the second preset temperature range, the silicon carbide raw material in the raw material area 101 is gradually carbonized, and the carbon powder gradually increases. At this time, the lifting rod is rotated 300. Under the rotation of the lifting rod 300, the first through hole 104 of the raw material area 101 and the second through hole 201 of the collecting box 200 are gradually aligned and overlapped until they are connected. At this time, the carbon powder in the raw material area 101 falls into the collecting box 200 through the overlapping first through hole 104 and second through hole 201 under the action of gravity and airflow, so that the carbon powder in the raw material area 101 is reduced. Such a reciprocating cycle can control the proportion of carbon powder in the raw material area 101, thereby reducing the carbon particles mixed in the rising airflow in the raw material area 101 during the growth of silicon carbide crystals, and effectively improving the crystal quality.

[0044] As a further embodiment, the silicon carbide crystal growth device disclosed in the embodiment of the present invention further includes a tray 400, wherein the tray 400 is fixedly connected to the collection box 200. In this way, the collection box 200 can be fixed when the crucible 100 rotates to ensure that the crucible 100 can rotate smoothly.

[0045] The embodiment of the present invention does not limit the specific connection method between the tray 400 and the collection box 200, wherein the tray 400 and the collection box 200 can be threadedly connected, can be snapped together, or can be plugged together. As long as the structure meets the use requirements of the present invention, it is within the protection scope of the present invention.

[0046] As a specific embodiment of the present invention, please continue to refer to Figure 1 The bottom of the collection box 200 disclosed in the embodiment of the present invention is provided with a groove, and the tray 400 is provided with a protrusion connected to the groove. The protrusion is adapted to be connected with the groove, so that the tray 400 can fix the collection box 200 on the tray 400.

[0047] It should be noted that the first through holes 104 can be arranged in various shapes on the bottom surface of the raw material area 101, and the second through holes 201 can be arranged in various shapes on the top surface of the collecting box 200. Of course, the first through holes 104 can be evenly or unevenly arranged on the bottom surface of the raw material area 101, and the second through holes 201 can be evenly or unevenly arranged on the top surface of the collecting box 200. As long as the second through holes 201 and the first through holes 104 are overlapped or staggered, technical personnel in this field can make arrangements according to actual needs.

[0048] As a specific embodiment of the present invention, please continue to refer to Figure 2 and Figure 3 The first through holes 104 disclosed in the embodiment of the present invention are multiple and are evenly arranged in a ring shape along the bottom end surface of the raw material area 101; the second through holes 201 are multiple and are evenly arranged in a ring shape along the top end surface of the collection box 200.

[0049] As a further embodiment, in the silicon carbide crystal growth device disclosed in the embodiment of the present invention, the central angle of the arc between any two adjacent first through holes 104 is 30°-60°, and the central angle of the arc between any two adjacent second through holes 201 is 30°-60°.

[0050] It should be emphasized that any one of the first through hole 104 and the second through hole 201 can be aligned and overlapped, so that the carbon powder can fall from the channel formed by the first through hole 104 and the second through hole 201 .

[0051] It should be further emphasized that the area between any two adjacent first through holes 104 can block the second through hole 201, or the area between any two adjacent second through holes 201 can block the first through hole 104. In this way, when the crucible 100 is in the initial heating stage, the raw material area 101 and the collection box 200 can be in an isolated state.

[0052] Since the bottom edge of the raw material area 101 is seriously carbonized and contains a lot of carbon powder, as a preferred embodiment of the present invention, the first through hole 104 disclosed in the embodiment of the present invention is opened at the edge area close to the collection box 200, and the second through hole 201 is opened at the edge area close to the raw material area 101. In this way, the carbon powder in the edge area of ​​the raw material area 101 can fall into the collection box 200, and the reciprocating cycle can effectively control the proportion of carbon powder in the raw material area 101.

[0053] The embodiment of the present invention does not limit the height of the collection box 200. As long as the height meets the use requirements of the present invention, it is within the protection scope of the present invention.

[0054] As one embodiment, the height of the collection box 200 disclosed in the embodiment of the present invention is 10 mm-60 mm.

[0055] The embodiment of the present invention does not specifically limit the apertures of the first through hole 104 and the second through hole 201 . As long as the apertures meet the use requirements of the present invention, they are within the protection scope of the present invention.

[0056] As one embodiment, the first through hole 104 and the second through hole 201 disclosed in the embodiment of the present invention have a hole diameter of 1 mm-10 mm.

[0057] The embodiment of the present invention further discloses a silicon carbide crystal growth method, which is applied to the silicon carbide crystal growth device disclosed in any one of the above embodiments, and specifically includes:

[0058] S100: Place silicon carbide raw material in the raw material area 101 of the crucible 100 and heat it. When the temperature of the raw material area 101 is within a first preset temperature range, the first through hole 104 of the raw material area 101 and the second through hole 201 of the collection box 200 are in a staggered state; S200: The temperature of the raw material area 101 continues to rise. When the temperature of the raw material area 101 is within the second preset temperature range, rotate the lifting rod 300, the first through hole 104 and the second through hole 201 are aligned and overlapped, and the carbon powder falls into the collection box 200 under the action of gravity and airflow.

[0059] First, place the silicon carbide raw material in the raw material area 101 of the crucible 100. When the temperature of the raw material area 101 is within the first preset temperature range, the first through hole 104 of the raw material area 101 and the second through hole 201 of the collecting box 200 are in a staggered state. At this time, the raw material area 101 and the collecting box 200 are isolated, and the carbonization degree of the raw material is low. After heating for a period of time, the temperature of the raw material area 101 continues to rise. When the temperature of the raw material area 101 reaches the second preset temperature range, the silicon carbide raw material in the raw material area 101 is gradually carbonized, and the carbon powder gradually increases. At this time, the lifting rod is rotated 300. Under the rotation of the lifting rod 300, the first through hole 104 of the raw material area 101 and the second through hole 201 of the collecting box 200 are gradually aligned until they are connected. At this time, the carbon powder in the raw material area 101 falls into the collecting box 200 through the overlapping first through hole 104 and second through hole 201 under the action of gravity and airflow, so that the carbon powder in the raw material area 101 is reduced. Such a reciprocating cycle can control the proportion of carbon powder in the raw material area 101, thereby reducing the carbon particles mixed in the rising airflow in the raw material area 101 during the growth of silicon carbide crystals, and effectively improving the crystal quality.

[0060] As a further embodiment, in step S200, the second preset temperature range is 2200°C-2500°C, and the radial temperature gradient from the middle to the edge of the raw material zone 101 increases by 0.5°C / mm.

[0061] As a further embodiment, in step S200, the temperature range of the collection box 200 is 2200°C-2500°C, and the axial temperature gradient from the lower part to the upper part of the collection box 200 decreases by 2°C / mm.

[0062] As a further embodiment, in step S200, the rotation speed of the lifting rod 300 is 0.1° / h-3°. This arrangement can ensure that the second through hole 201 of the collecting box 200 can be connected with the first through hole 104 of the raw material area 101 after a period of time, so that the carbon powder after carbonization of the silicon carbide raw material falls into the collecting box 200, thereby reducing the carbon particles mixed in the rising air flow in the raw material area 101 during the entire growth process of the silicon carbide crystal.

[0063] As the first specific embodiment of the present invention:

[0064] In the silicon carbide crystal growth device disclosed in the embodiment of the present invention, the outer diameters of the crucible 100 and the collecting box 200 are equal, and no specific requirements are made on the inner diameter, wherein the height of the collecting box 200 is set to 25 mm, the diameter of the unperforated area on the top surface of the collecting box 200 is set to 100 mm, the aperture of the second through hole 201 is 2 mm, and the central angle of the arc between any two adjacent second through holes 201 is 30°;

[0065] The diameter of the unperforated area on the bottom end surface of the raw material zone 101 is 150 mm, and the aperture of the first through hole 104 is 2 mm, wherein the distribution of the second through holes 201 is the same as that of the first through holes 104, the temperature of the seed crystal 500 in the growth zone 102 is 2200°C, and the radial temperature gradient from the middle to the edge of the raw material zone increases by 0.5°C / mm.

[0066] Among them, the raw material area 101 is in the high temperature zone with a temperature of 2400°C, the collecting box 200 is in the secondary high temperature zone with a temperature of 2300°C, the axial temperature gradient from the bottom to the top of the collecting box decreases by 1°C / mm, the growth pressure is 600Pa, and the rotation speed of the lifting rod 300 is 0.5° / h to ensure that the collecting box 200 can be connected with the raw material area 101 every time a certain period of time has passed.

[0067] The silicon carbide crystal grown by the silicon carbide crystal growth device and growth process disclosed in the above embodiment is cut and then observed under a dark field microscope to observe the internal package of the wafer. It can be concluded that: Figure 6 As shown, there is no package in a large area of ​​the wafer, and there is a phenomenon of one package in a single field of view ( Figure 6 The black dots in the figure are packages), where the package size is 2.428um.

[0068] As the second specific embodiment of the present invention:

[0069] In the silicon carbide crystal growth device disclosed in the embodiment of the present invention, the outer diameters of the crucible 100 and the collecting box 200 are equal, and no specific requirements are made on the inner diameter, wherein the height of the collecting box 200 is set to 25 mm, the diameter of the unperforated area on the top surface of the collecting box 200 is set to 100 mm, the aperture of the second through hole 201 is 2 mm, and the central angle of the arc between any two adjacent second through holes 201 is 30°;

[0070] The diameter of the unperforated area on the bottom end surface of the raw material zone 101 is 150 mm, and the aperture of the first through hole 104 is 2 mm, wherein the distribution of the second through holes 201 is the same as that of the first through holes 104, the temperature of the seed crystal 500 in the growth zone 102 is 2200°C, and the radial temperature gradient from the middle to the edge of the raw material zone increases by 0.5°C / mm.

[0071] Among them, the raw material area 101 is in a high temperature zone with a temperature of 2400°C, the collecting box 200 is in a sub-high temperature zone with a temperature of 2300°C, the axial temperature gradient from the bottom to the top of the collecting box 200 decreases by 1°C / mm, the growth pressure is 600Pa, and the rotation speed of the lifting rod 300 is 0.5° / h to ensure that the collecting box 200 can be connected with the raw material area 101 every time a certain period of time has passed.

[0072] In addition, some high-purity silicon is added into the collection box 200 .

[0073] The silicon carbide crystal grown by the silicon carbide crystal growth device and growth process disclosed in the above embodiment is cut and then observed under a dark field microscope to observe the internal package of the wafer. It can be concluded that: Figure 7 As shown, there is no package in a large area of ​​the wafer, and there is a phenomenon of one package in a single field of view ( Figure 7 The black dot in the figure is the package), where the package size is 3.399um.

[0074] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprises" or any other variation thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0075] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0076] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A silicon carbide crystal growth device, characterized in that: include: The crucible comprises a raw material area and a growth area, wherein a first through hole is provided on the bottom end surface of the raw material area, and a seed crystal holder for fixing a seed crystal is provided on the top wall of the growth area; A collecting box is arranged at the bottom of the crucible, and a second through hole is opened on the top surface of the collecting box; A lifting rod is connected to the crucible, and the lifting rod can drive the crucible to rotate so that the second through hole overlaps with or staggers with the first through hole.

2. The silicon carbide crystal growth device according to claim 1, characterized in that: It also includes a tray, which is fixedly connected to the collection box.

3. The silicon carbide crystal growth device according to claim 2, characterized in that: A groove is provided at the bottom of the collection box, and a protrusion connected to the groove by plugging is provided on the tray.

4. The silicon carbide crystal growth device according to claim 1, characterized in that: There are a plurality of first through holes, which are evenly arranged in a circular shape along the bottom end surface of the raw material area; There are a plurality of second through holes, which are evenly arranged in a circular shape along the top surface of the collecting box.

5. The silicon carbide crystal growth device according to claim 4, characterized in that: The central angle of the arc between any two adjacent first through holes is 30°-60°, and the central angle of the arc between any two adjacent second through holes is 30°-60°.

6. The silicon carbide crystal growth device according to claim 4, characterized in that: The first through hole is opened in an edge area close to the collection box; The second through hole is opened in an edge area close to the raw material area.

7. The silicon carbide crystal growth device according to claim 1, characterized in that: The height of the collecting box is 10 mm to 60 mm, and / or, The diameters of the first through hole and the second through hole are both 1 mm-10 mm.

8. A method for growing a silicon carbide crystal, applied to the silicon carbide crystal growing device according to any one of claims 1 to 7, characterized in that: include: S100: placing silicon carbide raw materials in a raw material zone of a crucible and heating them, and when the temperature of the raw material zone is within a first preset temperature range, the first through hole of the raw material zone and the second through hole of the collecting box are in a staggered state; S200: The temperature of the raw material zone continues to rise. When the temperature of the raw material zone is within a second preset temperature range, the lifting rod is rotated, the first through hole and the second through hole are aligned, and the carbon powder falls into the collection box under the action of gravity and airflow.

9. The method for growing silicon carbide crystals according to claim 8, characterized in that: In step S200, the second preset temperature range is 2200°C-2500°C, and the radial temperature gradient from the middle to the edge of the raw material zone increases by 0.5°C / mm.

10. The method for growing silicon carbide crystal according to claim 8, characterized in that: In step S200, the temperature range of the collection box is 2200°C-2500°C, the axial temperature gradient from the lower part to the upper part of the collection box decreases by 2°C / mm, and / or, The rotation speed of the lifting rod is 0.1° / h-3° / h.

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