Device and method for growing silicon carbide single crystals by PVT method

Abstract

The invention discloses a device and a method for growing silicon carbide single crystals by a PVT method, and belongs to the technical field of silicon carbide single crystal growth. The device for growing the silicon carbide single crystals by the PVT method 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 communicated with the crystal growth crucible and the raw material crucible; the number of the raw material crucibles is at least two, the raw material crucibles are used for containing silicon carbide powder, and each raw material crucible is controlled by adopting an independent heater; the included angle between the central axis of the raw material crucible and the gravity direction is smaller than or equal to 90 degrees. According to the device disclosed by the invention, the silicon carbide single crystal with larger thickness can be obtained through growth, and meanwhile, the silicon carbide single crystal obtained through growth has higher quality stability.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide single crystal growth, and in particular to a device and method for growing silicon carbide single crystals using a PVT method. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance the understanding of the overall background of the invention and should not be necessarily regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] The third generation semiconductors have the characteristics of large bandgap, high thermal conductivity, strong radiation resistance, high electron saturation drift rate, etc. Compared with the first and second generation semiconductors, they are more suitable for making high temperature, high frequency, radiation resistant and high power electronic devices, and have important application value. Silicon carbide (SiC) is the main representative of the third generation semiconductors. The preparation of high-quality and large-sized silicon carbide single crystals is the prerequisite for the industrial application of silicon carbide.

[0004] The main existing growth methods for silicon carbide single crystals include physical vapor transport (PVT), chemical vapor deposition (CVD), liquid phase epitaxy (LPE) and high-temperature solution method. Among them, the PVT method 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 setting of the internal structure of the crucible will directly affect the size and quality of the grown silicon carbide single crystal. Figure 1 It is a typical growth chamber for growing silicon carbide crystals by the PVT method at present. A seed crystal 1 is arranged at the bottom of the crucible cover 7, and a raw material powder 102 is arranged in the growth crucible 101. Under the temperature gradient provided by the external heater which gradually decreases 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, the silicon carbide single crystals prepared using this crucible structure generally have the problem of low thickness. This is mainly because there is a graphitization phenomenon in the growth process of the silicon carbide single crystal, which causes the process of growing the single crystal to terminate. In order to further increase the size of the silicon carbide single crystal, the prior art adopts a method of increasing the diameter of the raw material crucible to carry more silicon carbide powder and thus increase the sublimation area. However, this method will cause the raw material crucible to be heated unevenly, making it difficult to obtain silicon carbide single crystals of uniform quality.

[0006] Therefore, how to provide a device and method for growing silicon carbide single crystals using the PVT method that can grow silicon carbide single crystals of greater thickness and higher quality is an issue that needs to be addressed urgently. Summary of the invention

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

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

[0009] The crystal growth crucible is arranged vertically, and a seed crystal is arranged 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 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 gravity direction is less than or equal to 90°.

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

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

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

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

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

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

[0018] In a second aspect, the present invention provides a method for growing a silicon carbide single crystal by a PVT method, the method utilizing the above-mentioned device, comprising the following steps:

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

[0020] Step 2: vacuuming the raw material crucible, the crucible connector and the interior of the crystal growth crucible;

[0021] Step 3: heating all the raw material crucibles to a first preset temperature at the same time, and then maintaining the temperature constant;

[0022] Step 4: heating one of the raw material crucibles to the sublimation temperature, keeping the temperature constant for a set time, and then repeating the steps of "heating to the sublimation temperature, 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 sublimates;

[0023] Step 5: Cooling to obtain a silicon carbide single crystal.

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

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

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

[0027] The present invention improves the structure of the silicon carbide growth crucible, sets at least two raw material crucibles, and each raw material crucible is controlled by an independent heater, so that a thicker silicon carbide single crystal can be grown, and the grown silicon carbide single crystal has higher quality stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute an improper limitation of the present invention. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative work.

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

[0030] Figure 2 1 is a schematic top view of a device for growing a silicon carbide single crystal using a PVT method provided in an embodiment of the present invention;

[0031] Figure 3 It is a cross-sectional view of the device for growing silicon carbide single crystal by the PVT method provided by an embodiment of the present invention, wherein the raw material crucible is arranged horizontally;

[0032] Figure 4 It is a cross-sectional view of the device for growing silicon carbide single crystal by the PVT method provided in an embodiment of the present invention, wherein the raw material crucible is arranged at an angle;

[0033] In the figure, 101, growth crucible; 102, raw material powder; 103, silicon carbide single crystal; 1, seed crystal; 2, crystal growth crucible; 3, raw material crucible; 4, crucible connector; 5, silicon carbide powder; 6, heater; 7, crucible cover. DETAILED DESCRIPTION

[0034] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0035] The commonly used PVT growth crucibles generally have the problem of low thickness of grown silicon carbide single crystals. There is an existing technology that increases the diameter of the raw material crucible to increase the sublimation area, but this improvement has the problem of uneven heating of the raw material, which affects the quality of single crystal growth.

[0036] In order to overcome the above problems, the present invention provides a device for growing silicon carbide single crystals by PVT method, please refer to Figure 2 to Figure 4 The device for growing silicon carbide single crystal by PVT method comprises a crystal growth crucible 2, a crucible connector 4, a raw material crucible 3 and a heater 6. The crystal growth crucible 2 is arranged vertically, and a seed crystal 1 is arranged on the top of the crystal growth crucible for growing silicon carbide single crystal.

[0037] The crucible connector 4 connects the crystal growth crucible 2 and the raw material crucible 3. The crucible connector 4 is 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 the silicon carbide powder 5, and at least two of them are provided, and 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 continue to grow on the surface of the grown silicon carbide single crystal, thereby preparing a high-thickness silicon carbide single crystal.

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

[0040] The angle between the central axis of the raw material crucible 3 of the present invention and the direction of gravity is less than or equal to 90°, that is, the raw material crucible 3 can be connected to the crucible connector 4 horizontally or at a certain tilt angle. When the angle is equal to 90°, the opening of the raw material crucible 3 is horizontal and points to the crucible connector 4, such as Figure 3 When the angle is less than 90°, the raw material crucible 3 opens obliquely upward, as shown in FIG. Figure 4 shown.

[0041] In the present 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 or detachably connected to the crystal growth crucible 2. The present invention does not impose any special restrictions on the detachable connection method, and a detachable connection method commonly used in the art, such as a threaded connection, can be used.

[0042] A crucible cover 7 is arranged on the top of the crystal growth crucible 2 of the present invention, and a seed crystal 1 is arranged on the bottom of the crucible cover 7 .

[0043] The angle between the central axis of the raw material crucible 3 and the gravity direction is 45 to 90 degrees, more preferably 60 to 90 degrees. The central axis of the raw material crucible 3 intersects with the central axis of the crystal growth crucible 2, which 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 paths of each raw material crucible 3 are the same, thereby ensuring the quality stability of the grown silicon carbide single crystal.

[0044] In the present invention, 2 to 5 raw material crucibles 3 are provided, for example, Figure 3 and Figure 4 , a device containing four raw material crucibles 3 is shown.

[0045] In the present invention, a plurality of heaters 6 (not shown) may also be disposed outside the crystal growth crucible 2 to provide a suitable temperature gradient for the growth of the silicon carbide single crystal 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 using a PVT method, the method utilizing the above device and comprising the following steps:

[0047] Step 1: Place the silicon carbide powder 5 in the raw material crucible 3, fix the seed crystal 1 on the top of the crystal growth crucible 2, and connect the raw material crucible 3, the crucible connector 4 and the crystal growth crucible 2 in sequence. In order to ensure that the subsequent silicon carbide single crystal growth steps can be carried out smoothly, the airtightness of the connected device needs to be tested to ensure that the device is airtight. In order 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 the raw material crucible 3, the crucible connector 4 and the crystal growth crucible 2. It should be noted that the pressure control method in the device is the same as the pressure control unit used in the prior art, and the vacuum degree is also the same as the vacuum degree used in the prior art to grow silicon carbide single crystals, which will not be described in detail in the present invention.

[0049] Step 3: All raw material crucibles 3 are heated to a first preset temperature at the same time, and then kept at a constant temperature; the first preset temperature is 50-100° C. below the sublimation temperature. Heating all raw material crucibles 3 to a temperature close to the sublimation temperature at the same time is conducive to the continuous growth of silicon carbide single crystals, and further 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, set the time at a constant temperature, and then repeat the steps of "heating to the sublimation temperature, setting the time at a constant temperature" for the remaining raw material crucibles 3 in sequence until the silicon carbide powder 5 in all the raw material crucibles 3 no longer sublimates. In this process, the raw material crucible 3 that has completed sublimation is still kept at a constant temperature to avoid adversely affecting the growth temperature field of the silicon carbide single crystal. The present invention does not impose any special restrictions on the setting time of the constant temperature. Since the amount of silicon carbide powder 5 will affect the growth time of the silicon carbide single crystal, those skilled in the art can set it according to the specific device size and the carrying capacity of the silicon carbide powder 5, and the graphitization phenomenon of the silicon carbide powder 5 of a single raw material crucible 3 is used as a sign that the next raw material crucible 3 begins to heat up 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 cool down simultaneously, and finally a silicon carbide single crystal with a relatively large thickness is obtained.

[0052] The present invention improves the structure of the silicon carbide growth crucible, sets the raw material crucible 3 to at least two, and each raw material crucible 3 is controlled by an independent heater, so that a thicker silicon carbide single crystal can be grown. At the same time, the operation process is simple and does not involve mechanical operations such as lifting and pulling. The quality stability of the obtained silicon carbide single crystal is higher.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A device for growing silicon carbide single crystals by PVT method, characterized in that: It includes a crystal growth crucible, a crucible connector, a raw material crucible and a heater; The crystal growth crucible is arranged vertically, and a seed crystal is arranged on the top of the crystal growth crucible; The crucible connector connects the crystal growth crucible and the raw material crucible; The raw material crucible is used to hold silicon carbide powder and at least two 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 gravity direction is less than or equal to 90°.

2. The device according to claim 1, characterized in that The side portion of the crucible connector is detachably connected to the raw material crucible.

3. The device according to claim 1, characterized in that A crucible cover is arranged on the top of the crystal growth crucible, and the seed crystal is arranged on the bottom of the crucible cover.

4. The device according to claim 1, characterized in that The top of the crucible connector is integrally connected to the crystal growth crucible or is detachably connected to the crucible.

5. The device according to claim 1, characterized in that The angle between the central axis of the raw material crucible and the gravity direction is 45-90°.

6. The device according to claim 1, characterized in that The central axis of the raw material crucible intersects with the central axis of the crystal growth crucible.

7. The device according to claim 1, characterized in that The number of the raw material crucibles is 2 to 5.

8. A method for growing silicon carbide single crystals by PVT method, characterized in that: The method uses the device according to any one of claims 1 to 7, and comprises the following steps: Step 1: Place silicon carbide powder in a raw material crucible, fix a seed crystal on the top of the crystal growth crucible, connect the raw material crucible, the crucible connector and the crystal growth crucible in sequence, and load the furnace; Step 2: vacuuming the raw material crucible, the crucible connector and the interior of the crystal growth crucible; Step 3: heating all the raw material crucibles to a first preset temperature at the same time, and then maintaining the temperature constant; Step 4: heating one of the raw material crucibles to the sublimation temperature, keeping the temperature constant for a set time, and then repeating the steps of "heating to the sublimation temperature, 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 sublimates; Step 5: Cooling to obtain a silicon carbide single crystal.

9. The method according to claim 8, characterized in that The first preset temperature is 50-100° C. below the sublimation temperature.

10. The method according to claim 8, characterized in that The heating rate from the heating to the sublimation temperature is 0.8 to 2°C / min.

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