Apparatus and method for growing silicon carbide single crystal by pvt method

Abstract

The application discloses a device and method for growing silicon carbide single crystal by PVT method, and belongs to the technical field of silicon carbide single crystal growth. The device for growing silicon carbide single crystal by PVT method comprises a crystal growth crucible, a crucible connecting body, a raw material crucible and a heater. The crystal growth crucible is vertically arranged, and a seed crystal is arranged at the top of the crystal growth crucible. The crucible connecting body is connected with the crystal growth crucible and the raw material crucible. The raw material crucible is used for containing silicon carbide powder and at least two raw material crucibles are arranged, and each raw material crucible is controlled by an independent heater. The angle between the central axis of the raw material crucible and the gravity direction is less than or equal to 90 DEG. The device can grow silicon carbide single crystal with a larger thickness, and the grown silicon carbide single crystal has higher quality stability.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide single crystal growth technology, and in particular to an apparatus and method for growing silicon carbide single crystals by the PVT method. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Third-generation semiconductors possess characteristics such as large bandgap, high thermal conductivity, strong radiation resistance, and high electron saturation drift velocity. Compared to first- and second-generation semiconductors, they are more suitable for fabricating high-temperature, high-frequency, radiation-resistant, and high-power electronic devices, and have significant application value. Silicon carbide (SiC) is the main representative of third-generation semiconductors, and the preparation of high-quality, large-size silicon carbide single crystals is a prerequisite for the industrial application of silicon carbide.

[0004] The main existing methods for growing silicon carbide single crystals include physical vapor transport (PVT), chemical vapor deposition (CVD), liquid phase epitaxy (LPE), and high-temperature solution methods. Among them, PVT has gradually become the standard method for growing silicon carbide single crystals due to its high growth rate, relatively stable growth process, and cost advantages.

[0005] The internal structure of the crucible directly affects the size and quality of the grown silicon carbide single crystals. Figure 1 This is a typical growth chamber for growing silicon carbide crystals using the PVT method. A seed crystal 1 is placed at the bottom of the crucible lid 7, and raw material powder 102 is placed inside the growth crucible 101. Under a temperature gradient provided by an external heater, gradually decreasing from the raw material powder 102 to the seed crystal 1, the raw material powder 102 sublimates and deposits on the seed crystal to form a silicon carbide single crystal 103. However, silicon carbide single crystals prepared using this crucible structure generally suffer from low thickness. This is mainly due to graphitization during the silicon carbide single crystal growth process, which causes the growth process to terminate. To further increase the size of the silicon carbide single crystal, existing technologies use a method of increasing the diameter of the raw material crucible to hold more silicon carbide powder, thereby increasing the sublimation area. However, this method leads to uneven heating of the raw material crucible, making it difficult to obtain silicon carbide single crystals of uniform quality.

[0006] Therefore, how to provide an apparatus and method for growing silicon carbide single crystals with large thickness and high quality using the PVT method is an urgent problem to be solved. Summary of the Invention

[0007] In view of this, the present invention provides an apparatus and method for growing silicon carbide single crystals by the PVT method, which solves the problems of thin silicon carbide single crystal growth and high operating costs in the prior art.

[0008] In a first aspect, the present invention provides an apparatus for growing silicon carbide single crystals by the PVT method, comprising a crystal growth crucible, a crucible connector, a raw material crucible, and a heater;

[0009] The crystal growth crucible is set vertically, and a seed crystal is set on the top of the crystal growth crucible;

[0010] The crucible connector connects the crystal growth crucible and the raw material crucible;

[0011] The raw material crucible is used to hold silicon carbide powder and at least two crucibles are provided. Each raw material crucible is controlled by an independent heater. The angle between the central axis of the raw material crucible and the direction of gravity is less than or equal to 90°.

[0012] Preferably, the side of the crucible connector is detachably connected to the raw material crucible.

[0013] Preferably, the crystal growth crucible is provided with a crucible cover on top, and the seed crystal is provided at the bottom of the crucible cover.

[0014] Preferably, the top of the crucible connector is integrally connected to or detachably connected to the crystal growth crucible.

[0015] Preferably, the angle between the central axis of the raw material crucible and the direction of gravity is 45° to 90°.

[0016] Preferably, the central axis of the raw material crucible intersects the central axis of the crystal growth crucible.

[0017] Preferably, there are 2 to 5 raw material crucibles.

[0018] Secondly, the present invention provides a method for growing silicon carbide single crystals using the PVT method, the method utilizing the above-mentioned apparatus and comprising the following steps:

[0019] Step 1: Place silicon carbide powder in the raw material crucible, fix the seed crystal on the top of the crystal growth crucible, and connect the raw material crucible, crucible connector and crystal growth crucible in sequence, and load the furnace;

[0020] Step 2: Vacuum treatment is performed inside the raw material crucible, crucible connector, and crystal growth crucible;

[0021] Step 3: Simultaneously heat all raw material crucibles to the first preset temperature, and then maintain the temperature.

[0022] Step 4: Heat one of the raw material crucibles to the sublimation temperature and hold it at that temperature for a set time. Then repeat the steps of "heating to the sublimation temperature and holding at that temperature for a set time" for the remaining raw material crucibles until the silicon carbide powder in all the raw material crucibles no longer sublimates.

[0023] Step 5: Cool down to obtain silicon carbide single crystals.

[0024] Preferably, the first preset temperature is 50 to 100°C below the sublimation temperature.

[0025] Preferably, the heating rate to the sublimation temperature is 0.8–2 °C / min.

[0026] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0027] This invention improves the structure of the silicon carbide growth crucible by setting at least two raw material crucibles, each of which is controlled by an independent heater. This allows for the growth of thicker silicon carbide single crystals with higher quality stability. Attached Figure Description

[0028] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation thereof. Obviously, those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0029] Figure 1 This is a schematic diagram of a typical growth chamber for growing silicon carbide crystals using the PVT method.

[0030] Figure 2 This is a top view schematic diagram of the apparatus for growing silicon carbide single crystals by the PVT method provided in an embodiment of the present invention;

[0031] Figure 3 This is a cross-sectional view (AA) of the apparatus for growing silicon carbide single crystals by the PVT method provided in an embodiment of the present invention, wherein the raw material crucible is set horizontally;

[0032] Figure 4 This is a cross-sectional view (AA) of the apparatus for growing silicon carbide single crystals by PVT method provided in an embodiment of the present invention, wherein the raw material crucible is tilted.

[0033] In the figure, 101 is the growth crucible; 102 is the raw material powder; 103 is the silicon carbide single crystal; 1 is the seed crystal; 2 is the crystal growth crucible; 3 is the raw material crucible; 4 is the crucible connector; 5 is the silicon carbide powder; 6 is the heater; and 7 is the crucible lid. Detailed Implementation

[0034] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0035] Currently, commonly used PVT growth crucibles generally suffer from the problem of low thickness of grown silicon carbide single crystals. Existing technologies can increase the sublimation area by increasing the diameter of the raw material crucible, but this improvement results in uneven heating of the raw material, which affects the quality of single crystal growth.

[0036] To overcome the above problems, this invention provides an apparatus for growing silicon carbide single crystals using the PVT method. Please refer to [reference needed]. Figures 2-4 The apparatus for growing silicon carbide single crystals using the PVT method includes a crystal growth crucible 2, a crucible connector 4, a raw material crucible 3, and a heater 6. The crystal growth crucible 2 is vertically arranged, and a seed crystal 1 is provided on the top of the crystal growth crucible for the growth of silicon carbide single crystals.

[0037] The crucible connector 4 connects the crystal growth crucible 2 and the raw material crucible 3. The crucible connector 4 has a hollow structure, and the present invention does not impose any special restrictions on its shape.

[0038] The raw material crucible 3 is used to hold silicon carbide powder 5, and at least two crucibles are provided. Each raw material crucible 3 is controlled by an independent heater 6. The above design is to ensure that after the silicon carbide powder 5 in a single raw material crucible 3 undergoes graphitization, the remaining raw material crucibles 3 can continue to sublimate and grow on the surface of the already grown silicon carbide single crystal, thereby preparing a high-thickness silicon carbide single crystal.

[0039] It should be noted that heater 6 can not only heat the raw material crucible 3, but also ensure that the temperature of the raw material crucible 3 remains constant.

[0040] In this invention, the angle between the central axis of the raw material crucible 3 and the direction of gravity is less than or equal to 90°. That is, the raw material crucible 3 can be horizontally connected to the crucible connector 4, or connected at a certain inclined angle. When the angle is 90°, the opening of the raw material crucible 3 is horizontal and points towards the crucible connector 4, such as... Figure 3 As shown; when the included angle is less than 90°, the opening of the raw material crucible 3 is angled upwards, as shown. Figure 4 As shown.

[0041] In this invention, the side of the crucible connector 4 is detachably connected to the raw material crucible 3, and the top of the crucible connector 4 is integrally connected to or detachably connected to the crystal growth crucible 2. This invention does not impose special limitations on the detachable connection method; commonly used detachable connection methods in the art, such as threaded connections, are acceptable.

[0042] The crystal growth crucible 2 of the present invention is provided with a crucible cover 7 on the top, and the seed crystal 1 is provided at the bottom of the crucible cover 7.

[0043] The angle between the central axis of the raw material crucible 3 and the direction of gravity is 45° to 90°, more preferably 60° to 90°. The central axis of the raw material crucible 3 intersects with the central axis of the crystal growth crucible 2. This is to ensure that the central axis of the raw material crucible 3 and the central axis of the crystal growth crucible 2 are on the same plane, and to ensure that the crystal growth path of each raw material crucible 3 is the same, thus guaranteeing the quality stability of the grown silicon carbide single crystal.

[0044] In this invention, 2 to 5 raw material crucibles 3 are provided, for example, Figure 3 and Figure 4 The diagram shows an apparatus containing four raw material crucibles 3.

[0045] In this invention, multiple heaters 6 (not shown in the figure) can also be provided outside the crystal growth crucible 2 to provide a suitable temperature gradient for silicon carbide single crystal growth and ensure that the grown silicon carbide single crystal has good quality.

[0046] The present invention also provides a method for growing silicon carbide single crystals by PVT, the method utilizing the above-mentioned apparatus and comprising the following steps:

[0047] Step 1: Place silicon carbide powder 5 in raw material crucible 3, fix seed crystal 1 on top of crystal growth crucible 2, and connect raw material crucible 3, crucible connector 4, and crystal growth crucible 2 in sequence. To ensure smooth subsequent silicon carbide single crystal growth steps, the airtightness of the connected device needs to be tested to ensure good airtightness. To simplify the subsequent temperature control procedure, the amount of silicon carbide powder 5 added to each raw material crucible 3 is preferably the same.

[0048] Step 2: Vacuum treatment is performed inside the raw material crucible 3, crucible connector 4, and crystal growth crucible 2. It should be noted that the pressure control method in this device is the same as that used in the pressure control unit in the prior art, and the vacuum degree is also the same as that used in the prior art for growing silicon carbide single crystals; therefore, it will not be elaborated further here.

[0049] Step 3: Simultaneously heat all raw material crucibles 3 to the first preset temperature, and then maintain the temperature; the first preset temperature is 50-100°C below the sublimation temperature. Simultaneously heating all raw material crucibles 3 to near the sublimation temperature is beneficial for the continuous growth of silicon carbide single crystals, and thus helps to ensure the overall consistency of the grown silicon carbide single crystals.

[0050] Step 4: Heat one of the raw material crucibles 3 to the sublimation temperature and hold it at that temperature for a set time. Then, repeat the "heat to sublimation temperature, hold at that temperature for a set time" steps sequentially for the remaining raw material crucibles 3 until the silicon carbide powder 5 in all raw material crucibles 3 no longer sublimates. During this process, the raw material crucibles 3 that have completed sublimation are kept at a constant temperature to avoid adversely affecting the growth temperature field of the silicon carbide single crystal. This invention does not impose special limitations on the set time for the constant temperature. Since the amount of silicon carbide powder 5 affects the growth time of the silicon carbide single crystal, those skilled in the art can set the time according to the specific device size and the load capacity of the silicon carbide powder 5. The occurrence of graphitization of the silicon carbide powder 5 in a single raw material crucible 3 serves as the marker for the next raw material crucible 3 to begin heating to the sublimation temperature. The heating rate to the sublimation temperature is 0.8–2 °C / min, more preferably 0.8–1.5 °C / min; the sublimation temperature is 2300–2370 °C.

[0051] Step 5: Multiple heaters are used to cool the silicon carbide single crystal at the same time, and finally a silicon carbide single crystal with a large thickness is obtained.

[0052] This invention improves the structure of the silicon carbide growth crucible by setting at least two raw material crucibles 3, and each raw material crucible 3 is controlled by an independent heater. This allows for the growth of silicon carbide single crystals with greater thickness. At the same time, the operation process is simple and does not involve mechanical operations such as lifting or pulling, resulting in higher quality stability of the obtained silicon carbide single crystals.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for growing a silicon carbide single crystal by the PVT method, characterized by, The application discloses a device for growing silicon carbide single crystal by PVT method, which comprises a crystal growth crucible, a crucible connector, a raw material crucible and a heater. The crystal growth crucible is vertically arranged, and a seed crystal is arranged at the top of the crystal growth crucible. The crucible connector is connected with the crystal growth crucible and the raw material crucible. The raw material crucible is used for containing silicon carbide powder and is provided with at least two raw material crucibles, and each raw material crucible is controlled by an independent heater. The angle between the central axis of the raw material crucible and the direction of gravity is less than or equal to 90°. The method for growing silicon carbide single crystal by PVT method comprises the following steps: Step one: placing silicon carbide powder in the raw material crucible, fixing the seed crystal at the top of the crystal growth crucible, connecting the raw material crucible, the crucible connector and the crystal growth crucible in sequence, and loading the furnace; Step two: performing vacuumizing treatment on the inside of the raw material crucible, the crucible connector and the crystal growth crucible; Step three: simultaneously heating all the raw material crucibles to a first preset temperature, and then keeping the temperature constant; Step four: heating one of the raw material crucibles to a sublimation temperature, keeping the temperature constant for a set time, then repeating the steps of "heating to a sublimation temperature and keeping the temperature constant for a set time" for the remaining raw material crucibles in sequence until the silicon carbide powder in all the raw material crucibles no longer sublimes; 2. The method of claim 1, wherein, Step five: cooling to obtain silicon carbide single crystal.

3. The method of claim 1, wherein, The side of the crucible connector is detachably connected with the raw material crucible.

4. The method of claim 1, wherein, The top of the crystal growth crucible is provided with a crucible cover, and the seed crystal is arranged at the bottom of the crucible cover.

5. The method of claim 1, wherein, The top of the crucible connector is integrally connected or detachably connected with the crystal growth crucible.

6. The method of claim 1, wherein, The angle between the central axis of the raw material crucible and the direction of gravity is 45-90°.

7. The method of claim 1, wherein, The central axis of the raw material crucible intersects with the central axis of the crystal growth crucible.

8. The method of claim 1, wherein, The raw material crucible is provided with 2-5 raw material crucibles.

9. The method of claim 1, wherein, The first preset temperature is 50-100℃ lower than the sublimation temperature. The heating rate for heating to the sublimation temperature is 0.8-2℃ / min.

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