Vacuum pressure control system of PVT method SiC single crystal growth furnace
By adopting a variety of vacuum gauges and flow rate adjustment devices in the PVT method SiC single crystal growth furnace, the precise control of the full pressure range is achieved, the problem of poor control accuracy is solved, and the crystal growth quality is improved.
Patent Information
- Application Number
- CN202421478946.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-26
- Publication Date
- 2025-03-25
- Estimated Expiration
- 2034-06-26
AI Technical Summary
The existing PVT method SiC single crystal growth furnace vacuum pressure control system has poor control accuracy in the low pressure range, which has problems such as large pressure fluctuations and blind adjustment areas, which affects the growth rate and quality of the crystal.
A first vacuum gauge with a small range and a second vacuum gauge with a large range are used to measure the pressure in the single crystal growth furnace, covering the full vacuum range, and by adjusting the intake and outlet air flow, the vacuum pressure is controlled with a manual variable pressure relief valve and an electric needle valve with high precision.
The pressure control range in the single crystal growth furnace is effectively expanded, the vacuum pressure control accuracy and stability of the low-pressure range are improved, and the high-quality growth of the crystal is ensured.
Smart Images
Figure CN222666103U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of new material preparation, relates to SiC, and particularly relates to a vacuum pressure control system of a SiC single crystal growth furnace using a PVT method. Background Art
[0002] With the development of energy conservation and emission reduction, new energy grid connection, and smart grid, the performance indicators and reliability requirements of power semiconductor devices in these fields are increasing day by day, requiring devices to have higher operating voltage, greater current carrying capacity, higher operating frequency, higher efficiency, higher operating temperature, stronger heat dissipation capacity and higher reliability. Therefore, the development of third-generation semiconductor materials represented by silicon carbide (SiC) has begun to receive attention.
[0003] At present, the growth of silicon carbide (SiC) single crystals generally adopts the physical vapor transport method (PVT). Figure 1 This is a typical curve of pressure change over time in the growth process of silicon carbide (SiC) single crystal. With the increase in the size requirements and the improvement of the quality rate of silicon carbide single crystals, the requirements for vacuum pressure control in the single crystal growth furnace are also gradually increasing. The pressure change of the process gas has a great impact on the growth rate and crystal quality of silicon carbide (SiC) crystals, and the pressure change is complex during the entire process. In order to achieve high-quality and large-size silicon carbide single crystal growth, the accuracy and stability of vacuum pressure control are crucial.
[0004] The existing vacuum pressure control system of PVT SiC single crystal growth furnace is as follows: Figure 2 As shown in the figure, a flow controller is installed on the inlet pipe at the upstream inlet end to control the inlet flow rate to a constant flow rate, and a throttle valve (ball valve or butterfly valve) and a mechanical vacuum pump are installed on the outlet pipe at the downstream outlet end to control the outlet flow rate. The PID pressure controller relies on the furnace pressure data collected by the vacuum gauge to adjust the opening of the electric butterfly valve to control the downstream outlet rate, so that the pressure in the single crystal growth furnace reaches a dynamic balance. However, in the low-pressure control process, the effect of the pumping rate on the low-pressure change is relatively slow, and there is a certain hysteresis, which makes the 1×10 -1 The control accuracy of the low-pressure range of ~1×10Torr is poor, and the pressure fluctuation in the crystal growth furnace is large (about ±8%). In addition, the range of the vacuum gauge is difficult to cover the pressure variation range in the entire process of single crystal growth, thus forming a pressure adjustment blind area in the range not covered by the range (the pressure control range in the single crystal growth furnace is small), so that the pressure in the adjustment blind area cannot be effectively adjusted, thereby affecting the growth rate and growth quality of the crystal. Summary of the invention
[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present utility model is to provide a vacuum pressure control system for a PVT method SiC single crystal growth furnace. The control system can effectively expand the pressure control range in the single crystal growth furnace, improve the vacuum pressure control accuracy and stability in the low-pressure range, thereby ensuring the growth rate and growth quality of the crystal.
[0006] The technical solution of the utility model is achieved in this way:
[0007] A vacuum pressure control system for a PVT method SiC single crystal growth furnace comprises a single crystal growth furnace, wherein the air inlet end of the single crystal growth furnace is connected to an air inlet pipe, and the air outlet end of the single crystal growth furnace is connected to an air outlet pipe, the air inlet pipe is provided with a flow regulating mechanism for regulating the air inlet flow, and the air outlet pipe is provided with a regulating valve and a vacuum pump for regulating the air outlet flow.
[0008] The single crystal growth furnace is provided with a first vacuum gauge and a second vacuum gauge for measuring the pressure inside the single crystal growth furnace. The first vacuum gauge is a vacuum gauge in the low pressure range, and the second vacuum gauge is a vacuum gauge in the high pressure range, and the first vacuum gauge and the second vacuum gauge cover the full vacuum range.
[0009] It also includes a controller, which is connected to the first vacuum gauge and the second vacuum gauge and is used to obtain pressure data in the single crystal growth furnace. At the same time, the controller is connected to the flow regulating mechanism and the regulating valve to facilitate controlling the opening of the flow regulating mechanism and the regulating valve according to the pressure data in the single crystal growth furnace to adjust the pressure in the single crystal growth furnace.
[0010] Furthermore, the flow regulating mechanism comprises a manual variable pressure relief valve and an electric needle valve which are sequentially arranged along the gas flow direction, and the electric needle valve is connected to the controller.
[0011] Furthermore, the regulating valve is one of a ball valve, an electric butterfly valve and a throttle valve.
[0012] Compared with the prior art, the utility model has the following beneficial effects:
[0013] 1. The utility model adopts a first vacuum gauge with a small range and a second vacuum gauge with a large range to measure the pressure in the single crystal growth furnace. At the same time, the first vacuum gauge and the second vacuum gauge cover the full vacuum range, that is, the entire process pressure variation range of crystal growth, thereby effectively expanding the pressure control range in the single crystal growth furnace and effectively adjusting the pressure of the entire crystal growth process.
[0014] 2. The utility model adjusts the pressure of the single crystal growth furnace under low pressure by adjusting the air intake flow rate. Since the low pressure is very sensitive to the air intake flow rate, the vacuum pressure in the single crystal growth furnace in the low-pressure range can be controlled with high precision. At the same time, by adjusting the air outlet flow rate, the pressure in the single crystal growth furnace can be efficiently adjusted without hysteresis, so that the vacuum pressure in the single crystal growth furnace in the high-pressure range can be controlled with high precision, and then the vacuum pressure in the single crystal growth furnace in the low-pressure range and the high-pressure range can be controlled with high precision.
[0015] 3. The utility model adopts a manual variable pressure relief valve and an electric needle valve to control the air intake flow rate with high precision, which can further improve the vacuum pressure control accuracy in the low-pressure range of the single crystal growth furnace. The prices of the manual variable pressure relief valve and the electric needle valve are relatively low, which is conducive to reducing the cost investment of the control system. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 -The pressure variation with time in a typical silicon carbide (SiC) single crystal growth process.
[0017] Figure 2 -Schematic diagram of the vacuum pressure control system of the existing PVT method SiC single crystal growth furnace.
[0018] Figure 3 - Schematic diagram of the utility model. DETAILED DESCRIPTION
[0019] The utility model is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.
[0020] See also Figure 3 A vacuum pressure control system for a PVT method SiC single crystal growth furnace comprises a single crystal growth furnace, wherein the air inlet end of the single crystal growth furnace is connected with an air inlet pipe, and the air outlet end of the single crystal growth furnace is connected with an air outlet pipe, wherein a flow regulating mechanism is arranged on the air inlet pipe for regulating the air inlet flow, and a regulating valve and a vacuum pump are arranged on the air outlet pipe for regulating the air outlet flow.
[0021] The single crystal growth furnace is provided with a first vacuum gauge and a second vacuum gauge for measuring the pressure inside the single crystal growth furnace. The first vacuum gauge is a vacuum gauge in the low pressure range, and the second vacuum gauge is a vacuum gauge in the high pressure range, and the first vacuum gauge and the second vacuum gauge cover the full vacuum range.
[0022] It also includes a controller, which is connected to the first vacuum gauge and the second vacuum gauge and is used to obtain pressure data in the single crystal growth furnace. At the same time, the controller is connected to the regulating mechanism and the regulating valve to facilitate controlling the opening of the flow regulating mechanism and the regulating valve according to the pressure data in the single crystal growth furnace to adjust the pressure in the single crystal growth furnace.
[0023] Here, a first vacuum gauge with a small range and a second vacuum gauge with a large range are used together to measure the pressure in the single crystal growth furnace. At the same time, the first vacuum gauge and the second vacuum gauge cover the full vacuum range, that is, cover the entire process pressure variation range of crystal growth, thereby effectively expanding the pressure control range in the single crystal growth furnace and effectively adjusting the pressure of the entire crystal growth process.
[0024] In this embodiment, the measuring range of the first vacuum gauge is 0.1-650 Torr, and the measuring range of the second vacuum gauge is 1-1000 Torr.
[0025] In a specific implementation, the flow regulating mechanism includes a manual variable pressure relief valve and an electric needle valve which are sequentially arranged along the gas flow direction, and the electric needle valve is connected to a controller.
[0026] In a specific implementation, the regulating valve includes but is not limited to one of a ball valve, an electric butterfly valve and a throttle valve.
[0027] In specific applications, the controller is a dual-channel high-precision PID pressure controller. Here, the regulating valve, the single crystal growth furnace and the controller constitute a first closed-loop control loop, and the electric needle valve, the single crystal growth furnace and the controller constitute a second closed-loop control loop.
[0028] Use the above control system to control the vacuum pressure of the single crystal growth furnace:
[0029] When the pressure setting value is less than or equal to the low pressure range of 7.5 Torr, the controller adjusts the downstream regulating valve to a constant opening and performs PID automatic adjustment on the electric needle valve, and measures the pressure data in the single crystal growth furnace through the first vacuum gauge, and then adjusts the opening of the electric needle valve to make the pressure measurement value in the single crystal growth furnace quickly equal to the set value. The pressure of the single crystal growth furnace under low pressure is adjusted by adjusting the intake flow rate, because low pressure is very sensitive to the intake flow rate, so the vacuum pressure in the single crystal growth furnace in the low pressure range can be controlled with high precision.
[0030] When the pressure setting value is greater than the high pressure range of 7.5 Torr, the controller adjusts the electric needle valve to a constant opening and performs PID automatic adjustment on the downstream electric butterfly valve, and measures the pressure data in the single crystal growth furnace through the second vacuum gauge, and then adjusts the opening of the electric butterfly valve to make the pressure measurement value in the single crystal growth furnace quickly equal to the set value. In this way, the pressure in the single crystal growth furnace can be efficiently adjusted by adjusting the outlet gas flow rate without hysteresis, so that the vacuum pressure in the single crystal growth furnace in the high pressure range can be controlled with high precision.
[0031] In this way, the pressure of the single crystal growth furnace is controlled by the upstream and downstream two-way control mode (adjusting the inlet flow rate and the outlet flow rate), and the vacuum pressure in the single crystal growth furnace in the low-pressure range and the high-pressure range can be controlled with high precision.
[0032] Here, a manual variable pressure relief valve and an electric needle valve are used to control the intake flow rate with high precision to ensure the control accuracy of the low pressure of the single crystal growth furnace. During the control process, the manual variable pressure relief valve is first adjusted to a suitable position to maintain a constant intake flow rate. Then the controller automatically adjusts the electric needle valve PID according to the pressure data in the single crystal growth furnace and the set value. Since the vacuum leakage rate of the electric needle valve itself is small, the opening of the electric needle valve is a further adjustment of the intake flow rate of the manual variable pressure relief valve, so that the intake flow rate can be adjusted with high precision, thereby effectively improving the low pressure control accuracy. In addition, the price of manual variable pressure relief and electric needle valves is relatively low, which is conducive to reducing the cost investment of the control system.
[0033] Finally, it should be noted that the above embodiments of the present invention are only examples for illustrating the present invention, and are not intended to limit the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes and modifications can be made based on the above description. It is impossible to list all implementation methods here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.
Claims
1. A vacuum pressure control system for a SiC single crystal growth furnace using a PVT method, comprising a single crystal growth furnace, wherein the air inlet end of the single crystal growth furnace is connected to an air inlet pipe, and the air outlet end of the single crystal growth furnace is connected to an air outlet pipe, wherein the air inlet pipe is provided with a flow regulating mechanism for regulating the air inlet flow, and the air outlet pipe is provided with a regulating valve and a vacuum pump for regulating the air outlet flow; characterized in that: The single crystal growth furnace is provided with a first vacuum gauge and a second vacuum gauge for measuring the pressure inside the single crystal growth furnace, wherein the first vacuum gauge is a vacuum gauge in a low pressure range, and the second vacuum gauge is a vacuum gauge in a high pressure range, and the first vacuum gauge and the second vacuum gauge cover the full vacuum range; It also includes a controller, which is connected to the first vacuum gauge and the second vacuum gauge and is used to obtain pressure data in the single crystal growth furnace. At the same time, the controller is connected to the flow regulating mechanism and the regulating valve to facilitate controlling the opening of the flow regulating mechanism and the regulating valve according to the pressure data in the single crystal growth furnace to adjust the pressure in the single crystal growth furnace.
2. A vacuum pressure control system for a PVT SiC single crystal growth furnace according to claim 1, characterized in that: The flow regulating mechanism comprises a manual variable pressure relief valve and an electric needle valve which are sequentially arranged along the gas flow direction, and the electric needle valve is connected to a controller.
3. A vacuum pressure control system for a PVT SiC single crystal growth furnace according to claim 1, characterized in that: The regulating valve is one of a ball valve, an electric butterfly valve and a throttle valve.