Gas supply system for CVD and control method

Abstract

The application discloses a gas supply system and a control method for CVD. The gas supply system comprises a storage tank and a bubbling tank, the storage tank and the bubbling tank are communicated through a liquid inlet pipeline, the bubbling tank is further provided with a carrier gas pipeline and a gas outlet pipeline, the outlet of the carrier gas pipeline is located below the liquid level of the bubbling tank, and the inlet of the gas outlet pipeline is located above the liquid level of the bubbling tank. The gas supply system further comprises a supplementary tank, the supplementary tank is communicated with the storage tank through a supplementary pipeline, the supplementary tank and the bubbling tank are communicated through a gas supplement pipeline, the inlet of the gas supplement pipeline is located above the liquid level of the supplementary tank, and the outlet of the gas supplement pipeline is located above the liquid level of the bubbling tank. The supplementary tank is provided with a first heat preservation jacket, and the bubbling tank is provided with a second heat preservation jacket. The application can realize uninterrupted supply of liquid raw materials for a CVD process for a long time, is not limited by the length of the process time, and is especially suitable for a CVD process with a relatively thick coating.

Description

TECHNICAL FIELD

[0001] The present application relates to a gas supply system and control method for CVD, belonging to the technical field of chemical vapor deposition, in particular to a bubbling gas supply system of a chemical vapor deposition device. BACKGROUND

[0002] With the rapid development of photovoltaic and semiconductor markets, CVD (chemical vapor deposition) technology is increasingly applied. In particular, the market demand for CVD silicon carbide coated graphite products is increasing, and different use scenarios have great differences in the thickness of the CVD silicon carbide film on the surface of the graphite product, which is between 5 μm and 1000 μm. At present, the mainstream CVD silicon carbide process mainly uses methyltrichlorosilane (commonly known as MTS) system. At room temperature, MTS is a volatile liquid, and it will hydrolyze violently when it comes into contact with air, generating hydrogen chloride gas with strong corrosiveness. Therefore, in order to obtain high-purity silicon carbide film, the raw material needs to be continuously supplied in a clean and sealed system during the growth of CVD silicon carbide coating film. In particular, for the preparation of thick silicon carbide coating, chemical vapor deposition needs to be carried out for a long time without interruption. As the process time increases, the risk of instability of MTS liquid raw material delivery is greatly increased.

[0003] A Chinese invention patent with application number CN202011466959.6 discloses an MTS process gas flow automatic control method and equipment. It uses the method of bubbling carrier gas to carry out MTS raw gas, and an electronic scale is arranged at the bottom of the bubbling tank to link with the controller. The current MTS flow is judged by monitoring the electronic scale, and then the controller calculates the deviation value of the current MTS flow and the preset MTS flow to compensate the temperature of the mold temperature machine outside the MTS storage tank, so as to adjust the temperature of the MTS liquid in the storage tank, so that the adjusted MTS flow is equal to the preset MTS flow.

[0004] However, in this scheme, as the deposition time is prolonged, the liquid level of the MTS storage tank drops quickly, which inevitably leads to a continuous decrease in the output of MTS carried out by the overloading gas in the later stage, and the instability of raw material supply is fatal to the deposition process, which eventually leads to a large number of defects in the coating material and even abnormal surface. Moreover, since the MTS filling port directly supplements liquid MTS, there is no temperature compensation for the supplemented liquid. When doing long-time process, it is easy to cause the continuous decrease of the temperature of the bubbling tank, thereby affecting the vapor amount of the MTS raw material. SUMMARY

[0005] In order to overcome the problems in the prior art, the present application provides a gas supply system and control method for CVD to improve the stability of MTS raw material supply and improve the deposition quality of long-time uninterrupted chemical vapor deposition. The specific technical scheme is as follows.

[0006] The gas supply system for CVD comprises a storage tank and a bubbling tank, the storage tank and the bubbling tank are communicated through a liquid inlet pipeline, the bubbling tank is further provided with a carrier gas pipeline and a gas outlet pipeline, the outlet of the carrier gas pipeline is below the liquid level of the bubbling tank, and the inlet of the gas outlet pipeline is above the liquid level of the bubbling tank; a feeding tank is further provided, the feeding tank is communicated with the storage tank through a feeding pipeline, the feeding tank and the bubbling tank are communicated through a feeding gas pipeline, the inlet of the feeding gas pipeline is above the liquid level of the feeding tank, and the outlet of the feeding gas pipeline is above the liquid level of the bubbling tank; the feeding tank is provided with a first heat preservation jacket, and the bubbling tank is provided with a second heat preservation jacket.

[0007] Further, the gas outlet pipeline is provided with a gas pressure detection mechanism.

[0008] Further, the carrier gas pipeline, the gas outlet pipeline, the feeding pipeline, the liquid inlet pipeline and the feeding gas pipeline are all provided with valves.

[0009] Further, a first electronic scale is arranged below the storage tank, a second electronic scale is arranged below the feeding tank, and a third electronic scale is arranged below the bubbling tank. The electronic scales are used for measuring the total mass of the corresponding tanks, so as to facilitate the control of the remaining amount of raw materials in the tanks.

[0010] Further, the storage tank is provided with a first pressure gauge, and the storage tank is further provided with an inert gas pipeline. The liquid raw materials in the storage tank can be transported to the bubbling tank or the feeding tank through the liquid inlet pipeline or the feeding pipeline by increasing the pressure in the storage tank through the inert gas pipeline.

[0011] Further, the feeding tank is provided with a second pressure gauge. The second pressure gauge is used for detecting the pressure in the feeding tank, so that the pressure in the feeding tank is within a set range.

[0012] Based on the same inventive concept, the application further relates to a control method of the gas supply system for CVD, which adopts the above-mentioned gas supply system, the carrier gas in the carrier gas pipeline carries the liquid raw materials into the gas outlet pipeline in the form of bubbling, the gas pressure detection mechanism in the gas outlet pipeline continuously monitors the pressure in the gas outlet pipeline, when the pressure is less than a first set value, the controller opens the valve on the feeding gas pipeline, so that the liquid raw material steam in the feeding tank enters the bubbling tank through the feeding gas pipeline; when the pressure rises to be greater than a second set value, the controller closes the valve on the feeding gas pipeline.

[0013] Further, when the liquid raw materials in the feeding tank are less than a set value, the liquid raw materials in the storage tank are transported to the feeding tank through the feeding pipeline.

[0014] Compared with the prior art, the application has the following beneficial effects.

[0015] 1. The system can realize long-time uninterrupted supply of liquid raw material for CVD process, and is not limited by process time, and is especially suitable for CVD process with thick coating;

[0016] 2. The steam compensation of the bubble tank by the feed tank effectively solves the problem of unstable and inaccurate raw material supply caused by the temperature reduction of the liquid in the bubble tank after the conventional liquid supplement;

[0017] 3. The system has simple structure, can be directly improved in the existing bubble equipment, has low modification cost, and has good economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a schematic diagram of the gas supply system of the present application.

[0019] In the figure: the storage tank 100, the first electronic scale 101, the first pressure gauge 102, the feed tank 200, the first heat preservation jacket 201, the second electronic scale 202, the second pressure gauge 203, the bubble tank 300, the second heat preservation jacket 301, the third electronic scale 302, the liquid inlet pipeline 1, the carrier gas pipeline 2, the gas outlet pipeline 3, the feed pipeline 4, the air supplement pipeline 5, the valve 6, the air pressure detection mechanism 7, the controller 8, and the inert gas pipeline 9. DETAILED DESCRIPTION

[0020] The present application will be further described in detail below with reference to the accompanying drawings.

[0021] Reference Figure 1 A gas supply system for CVD includes a storage tank 100, a feed tank 200 and a bubble tank 300, the storage tank 100 and the bubble tank 300 are communicated through a liquid inlet pipeline 1, the bubble tank 300 is further provided with a carrier gas pipeline 2 and a gas outlet pipeline 3, the outlet of the carrier gas pipeline 2 is below the liquid level of the bubble tank 300, and the inlet of the gas outlet pipeline 3 is above the liquid level of the bubble tank 300; the feed tank 200 is communicated with the storage tank 100 through a feed pipeline 4, the feed tank 200 and the bubble tank 300 are communicated through an air supplement pipeline 5, the inlet of the air supplement pipeline 5 is above the liquid level of the feed tank 200, and the outlet of the air supplement pipeline 5 is above the liquid level of the bubble tank 300; the feed tank 200 is provided with a first heat preservation jacket 201, and the bubble tank 300 is provided with a second heat preservation jacket 301; the gas outlet pipeline 3 is provided with an air pressure detection mechanism 7 for detecting the outlet gas pressure of the bubble tank 300.

[0022] The first heat preservation jacket 201 is used for heat preservation of the material supplement tank 200, so that liquid raw materials (MTS) in the material supplement tank 200 are evaporated; the second heat preservation jacket 301 is used for heat preservation of the bubbling tank 300, so that the bubbling tank 300 is in a set, stable temperature range; the liquid inlet pipeline 1, the carrier gas pipeline 2, the gas outlet pipeline 3, the material supplement pipeline 4 and the air supplement pipeline 5 are all provided with valves 6, the valves 6 are used for controlling the communication and closing of the pipelines, the valves 6 can be manual valves or electric valves, and preferably are electric valves, so as to facilitate automatic control.

[0023] Preferably, the first electronic scale 101 is arranged below the material storage tank 100; the second electronic scale 202 is arranged below the material supplement tank 200; and the third electronic scale 302 is arranged below the bubbling tank 300. The electronic scales are used for measuring the total mass of the corresponding tanks, so as to facilitate control of the remaining amount of raw materials in the tanks.

[0024] The material storage tank 100 is provided with the first pressure gauge 102, and the material storage tank 100 is also provided with the inert gas pipeline 9. Through pressurization of the inert gas pipeline 9 to the material storage tank 100, liquid raw materials in the material storage tank 100 can be transported to the bubbling tank 300 or the material supplement tank 200 through the liquid inlet pipeline 1 or the material supplement pipeline 4.

[0025] Further, the material supplement tank 200 is provided with the second pressure gauge 203. The second pressure gauge is used for detecting the pressure in the material supplement tank 200, so that the pressure in the material supplement tank 200 is in a set range.

[0026] The control method of the gas supply system is as follows: the carrier gas in the carrier gas pipeline 2 is in the form of bubbling in the bubbling tank 300, so as to bring liquid raw materials into the gas outlet pipeline 3; the pressure detection mechanism in the gas outlet pipeline 3 continuously monitors the pressure in the gas outlet pipeline 3; when the pressure is less than a first set value, the controller 8 opens the valve 6 on the air supplement pipeline 5, so that raw material steam in the material supplement tank 200 enters the bubbling tank 300 through the air supplement pipeline 5; when the pressure rises to be greater than a second set value, the controller 8 closes the valve 6 on the air supplement pipeline 5. When the liquid raw materials in the material supplement tank 200 are less than a set value, the liquid raw materials in the material storage tank 100 are transported into the material supplement tank 200 through the material supplement pipeline 4.

[0027] The working principle of the gas supply system of the present application is as follows: the delivery amount of the carrier gas (usually hydrogen) in the carrier gas pipeline 2 is kept constant, the pressure in the gas outlet pipeline 3 of the bubbling tank 300 is mainly determined by the pressure of the hydrogen, the vapor pressure in the bubbling tank 300 and the amount of MTS carried out by bubbling, under the condition that the temperature of the bubbling tank 300 is kept constant by the second heat insulation jacket 301, as the liquid MTS in the bubbling tank 300 is continuously consumed, the liquid level is continuously lowered, resulting in the amount of MTS carried out by hydrogen being continuously reduced, the pressure detected by the gas pressure detection mechanism 7 is continuously lowered, when the pressure is less than the first set value (such as 95% of the target pressure), the controller 8 opens the valve 6 on the gas supplement pipeline 5, and the raw material vapor in the raw material tank 200 enters the bubbling tank 300 through the gas supplement pipeline 5, the vapor is directly supplemented into the gas outlet pipeline 3 on the one hand, and is supplemented into the liquid raw material of the bubbling tank 300 on the other hand, so that the liquid level of the bubbling tank 300 is continuously raised, thereby ensuring that the amount of MTS in the gas outlet pipeline 3 is in a proper and stable delivery state, and the temperature of the bubbling tank 300 will not be greatly lowered due to the entry of the raw material vapor, and will always be kept within a proper range. When the pressure detected by the gas pressure detection mechanism 7 rises to be greater than the second set value (such as 105% of the target pressure), the controller 8 closes the valve 6 on the gas supplement pipeline 5.

[0028] The embodiments of the present application are described above in combination with the drawings, the embodiments and the features in the embodiments in the present application can be combined with each other without conflict. The present application is not limited to the above-mentioned specific embodiments, the above-mentioned specific embodiments are only illustrative, but not limited, the ordinary skilled in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, which all belong to the protection scope of the present application.

Claims

1. A gas supply system for CVD, comprising a storage tank and a bubbling tank, the storage tank and the bubbling tank being connected by a liquid inlet pipe, the bubbling tank further comprising a carrier gas pipe and a gas outlet pipe, the outlet of the carrier gas pipe being located below the liquid surface of the bubbling tank, and the inlet of the gas outlet pipe being located above the liquid surface of the bubbling tank; characterized in that: It also includes a feed tank, which is connected to the storage tank via a feed pipe, and the feed tank and the bubbling tank are connected via a gas supply pipe. The inlet of the gas supply pipe is located above the liquid surface of the feed tank, and the outlet of the gas supply pipe is located above the liquid surface of the bubbling tank. The feed tank is provided with a first insulation jacket, and the bubbling tank is provided with a second insulation jacket. The air outlet pipe is equipped with an air pressure detection mechanism; Valves are installed on the carrier gas pipeline, gas outlet pipeline, material replenishment pipeline, liquid inlet pipeline, and gas replenishment pipeline.

2. The gas supply system for CVD according to claim 1, characterized in that, A first electronic scale is installed below the storage tank; a second electronic scale is installed below the replenishment tank; and a third electronic scale is installed below the bubbling tank.

3. A gas supply system for CVD according to claim 1, characterized in that, The storage tank is equipped with a first pressure gauge and also has an inert gas pipeline.

4. A gas supply system for CVD according to claim 1, characterized in that, The feed tank is equipped with a second pressure gauge.

5. A control method for a gas supply system for CVD, comprising using a gas supply system as described in any one of claims 1-4, characterized in that, The carrier gas in the carrier gas pipeline carries the liquid raw material into the outlet gas pipeline in the form of bubbles in the bubbling tank. The gas pressure detection mechanism in the outlet gas pipeline continuously monitors the pressure in the outlet gas pipeline. When the pressure is less than the first set value, the controller opens the valve on the replenishment gas pipeline, allowing the liquid raw material vapor in the replenishment tank to enter the bubbling tank through the replenishment gas pipeline. When the pressure rises to a value greater than the second set value, the controller closes the valve on the replenishment gas pipeline.

6. The control method according to claim 5, characterized in that, When the liquid raw material in the replenishment tank is less than the set value, the liquid raw material in the storage tank is transported to the replenishment tank through the replenishment pipeline.

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