A coating device, coating method and quartz tube for a quartz tube of a chemical vapor deposition tube furnace

Abstract

The present invention belongs to the technical field of plasma coating, and relates to a coating device, a coating method and a quartz tube for a quartz tube of a chemical vapor deposition tube furnace. The coating device includes a coating furnace body, an outer electrode provided on the inner wall of the coating furnace body, an inner electrode provided in the inner cavity of the coating furnace body, a radio frequency power supply electrically connected to the inner electrode and the outer electrode, a heating structure for providing heat to the inner cavity of the coating furnace body, a support structure provided in the inner cavity of the coating furnace body for supporting the quartz tube to be coated, and an air inlet structure and an air outlet structure provided at the end of the coating furnace body. A reaction region is formed between the outer electrode and the inner electrode. During coating, the quartz tube to be coated is sleeved outside the inner electrode and located in the reaction region. The film formed on the inner surface of the quartz tube in the present invention has good compactness and excellent thickness uniformity, and can effectively prevent the quartz tube from cracking during the chemical vapor deposition process.

Description

Technical Field

[0001] The present invention belongs to the technical field of plasma coating, and relates to a coating device, a coating method and a quartz tube for a quartz tube of a chemical vapor deposition tube furnace. Background Art

[0002] Improving efficiency and reducing costs is an eternal topic in the development of photovoltaics. With the development of solar cell technology, the efficiency limit caused by the structure of PERC solar cells can no longer meet the development needs of photovoltaic technology. TOPCon (Tunnel Oxide Passivated Contacts) cells have a theoretical limit efficiency of 28.7% (double-sided passivated contact structure) due to their excellent structure and have become the next-generation crystalline silicon solar cell structure to replace mass-produced PERC (Passivated Emitter and Rear Cell) solar cells. Chemical vapor deposition technology is indispensable in the preparation process of TOPCon cells. This technology requires a high-temperature environment. At present, in order to carry out the reaction smoothly, most use quartz tubes as the reaction chambers of chemical vapor deposition tube furnaces.

[0003] Quartz tubes are widely used in the field of photovoltaic equipment because of their excellent high-temperature resistance. However, during the production process of battery wafers, a vacuum environment, a high-temperature environment and corresponding reaction gases need to be introduced. Silane gas needs to be introduced during the low-pressure chemical vapor deposition reaction process. The single crystal silicon generated during the reaction process of silane will adhere to the quartz tube wall, resulting in a decline in the performance of the quartz tube. After a certain amount of impurities adhere, during the vacuum pumping process, it may cause the quartz tube to rupture, resulting in problems such as the quartz tube bursting and damaging the silicon wafers, affecting production.

[0004] Coating the quartz tube is a common method, which can isolate the direct contact between the quartz tube and impurities, reduce the influence of impurities on the quartz tube, and can improve the high-temperature resistance of the quartz tube. At present, the quartz tube coating method is not yet mature. Therefore, it is particularly important to study a convenient, fast and effective coating device and process. Summary of the Invention

[0005] The purpose of the present invention is to provide a coating device, a coating method and a quartz tube for a quartz tube of a chemical vapor deposition tube furnace. By using the method of plasma chemical vapor deposition, a protective film is formed on the inner surface of the quartz tube. The film is dense and has a uniform thickness, which can effectively avoid rupture during the chemical vapor deposition process.

[0006] The present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a coating device for a quartz tube of a chemical vapor deposition tube furnace, comprising a coating furnace body, an outer electrode provided on the inner wall of the coating furnace body, an inner electrode provided in the inner cavity of the coating furnace body, a radio frequency power supply electrically connected to the inner electrode and the outer electrode, a heating structure for providing heat to the inner cavity of the coating furnace body, a supporting structure provided in the inner cavity of the coating furnace body for supporting the quartz tube to be coated, and an air inlet structure and an air outlet structure provided at the end of the coating furnace body. A reaction area is formed between the outer electrode and the inner electrode. During coating, the quartz tube to be coated is sleeved outside the inner electrode and located in the reaction area.

[0008] In the above solution, for coating the inner surface of a cylindrical quartz tube, the inner wall of the coating furnace body is used as the outer electrode, and the inner electrode is arranged in the cavity. During coating, the quartz tube to be coated is sleeved outside the inner electrode, and the air inlet structure introduces a working gas between the quartz tube and the inner electrode. The working gas is electrolyzed into plasma under the action of the energization of the inner and outer electrodes, and then reacts to form a deposit on the inner wall of the quartz tube, realizing the coating of the inner wall of the quartz tube.

[0009] For coating the inner surface of a cylindrical quartz tube, in the coating device, the inner electrode and the outer electrode can also be arranged at both ends of the quartz tube, and a gas is introduced into the quartz tube. However, through experiments, for the coating device with this structure, the obtained film has poor compactness, and when used in the chemical vapor deposition process, the surface film will still be damaged, thus unable to protect the quartz tube.

[0010] Preferably, the coating device further comprises a sealing structure, which is in contact with the outer electrode and the outer wall of the quartz tube and is close to the end of the quartz tube. The sealing structure is provided to prevent the working gas from entering between the quartz tube and the inner wall of the coating furnace body. This can not only prevent the film from being deposited on the outer wall of the quartz tube, but also help to concentrate the working gas inside the quartz tube, which is beneficial to the coating of the inner wall of the quartz tube.

[0011] Preferably, the coating furnace body is of a multi-section type, and each section of the coating furnace body corresponds to an independent heating structure. Generally speaking, if the furnace body is controlled at a fixed temperature, usually the temperature in the middle section will be higher than that at both ends, resulting in uneven temperature distribution inside the furnace body. In this solution, a multi-section type furnace body is adopted to control the temperature of the coating furnace body in sections, which is more conducive to maintaining the uniform consistency of the temperature distribution in the inner cavity of the furnace body. The more uniform the temperature distribution is, the more conducive it is to form a dense and uniform-thickness film.

[0012] Preferably, the inner electrode is mounted at the end of the coating furnace body through a rotating base, and the inner electrode rotates driven by the rotating base. The present invention is directed to the coating of a quartz tube. Since the inner cavity of the quartz tube is cylindrical, after the working gas is introduced, it is difficult to be evenly distributed, resulting in uneven thickness of the formed thin film. Therefore, in this solution, by rotatably mounting the inner electrode, the inner electrode can not only serve as a power generation electrode, but also as a tool for making the working gas and plasma more evenly distributed. During the process, appropriately rotating the inner electrode is beneficial to significantly improve the uniformity of the thin film thickness.

[0013] Preferably, the reaction region includes a front region close to the opening and a rear region far from the opening. During coating, the quartz tube to be coated is located in the rear region of the reaction region. By setting the front region, in the front region, the working gas begins to be decomposed into active groups. Under the action of the gas flow, the active groups move forward to the rear region. In this region, although there is still some working gas being continuously decomposed into active groups, due to the existence of the front region, the concentration of active groups is relatively high. In the rear region, the active groups react on the surface of the quartz tube to form a silicon carbide thin film, which is more conducive to forming a denser thin film and also conducive to accelerating the formation efficiency of the thin film.

[0014] Preferably, the length of the front region is 1 / 2 or more of the length of the rear region.

[0015] Preferably, the lengths of the inner electrode and the outer electrode are equal and equal to or greater than the length of the quartz tube.

[0016] In a second aspect, the present invention provides a coating method for a quartz tube of a chemical vapor deposition tube furnace. Based on the above coating equipment, it at least includes the following steps:

[0017] S-1. Feed the quartz tube to be coated into the inner cavity of the coating furnace body, and the quartz tube to be coated is sleeved outside the inner electrode;

[0018] S-2. Evacuate the inner cavity of the coating furnace body and maintain the inner cavity in a vacuum state;

[0019] S-3. Raise the temperature of the inner cavity of the coating furnace body to T and adjust the pressure to P;

[0020] S-4. Introduce the working gas into the region between the inner electrode and the quartz tube to be coated, turn on the radio frequency power supply to generate plasma, and deposit a thin film on the inner surface of the quartz tube to be coated.

[0021] Preferably, in step S-4, the inner electrode is rotated at a speed of 5 rpm to 25 rpm, especially 10 rpm to 25 rpm.

[0022] Preferably, in step S-3, T is 400 °C to 600 °C and P is 1000 mtorr to 2500 mtorr.

[0023] Preferably, in step S-2, the vacuum degree is less than or equal to 15 mtorr.

[0024] Preferably, in step S-4, the working gases are methane and silane. The flow rate of the introduced methane is 1000 - 5000 sccm, and the flow rate of the introduced silane is 1000 - 2500 sccm.

[0025] Preferably, the power of the radio frequency power supply is 20 kW to 40 kW and the frequency is greater than 20 KHz.

[0026] Preferably, after the deposition is completed in step S-4, a low-temperature inert gas is introduced into the inner cavity of the coating furnace to rapidly reduce the temperature of the inner cavity, which is beneficial to improving the adhesion of the film.

[0027] In a third aspect, the present invention provides a quartz tube for a chemical vapor deposition tube furnace. Through the above coating method, a silicon carbide film is formed on the inner surface of the quartz tube.

[0028] By implementing the above technical solutions, the present invention has the following beneficial effects:

[0029] 1. By improving the internal structure of the coating furnace body, the present invention can coat the inner wall of the quartz tube.

[0030] 2. By further optimizing the internal structure of the coating furnace body, the present invention can make the thickness of the silicon carbide film formed on the inner wall of the quartz tube more uniform and the film more dense. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic plan view of the coating equipment shown in Embodiment 1 of the present invention;

[0032] Figure 2 is a schematic plan view of the coating equipment shown in Embodiment 2 of the present invention

[0033] Figure 3 is a schematic diagram of the selected positions when measuring the film thickness on the surface of the quartz tube. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0035] This specific embodiment is only an interpretation of the present invention and does not limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present invention, it is protected by the patent law.

[0036] Embodiment 1

[0037] This embodiment provides a coating device for coating the inner surface of a quartz tube. The coated quartz tube is used in a chemical vapor deposition tube furnace. By forming a protective film on the inner surface of the quartz tube, it is beneficial to reduce the breakage of the quartz tube during the chemical vapor deposition process.

[0038] See Figure 1 and Figure 2 As shown in and, the coating device provided in this embodiment includes a coating furnace body 200 with an opening on the side, which is sealed by a lid, and the inside is a cavity 201. The wall of the coating furnace body 200 has two layers, and a heating structure 300, such as a thermocouple, is arranged between the two layers to provide a thermal environment for the reaction in the cavity. In the cavity of the coating furnace body 200, a support structure 400 for carrying the quartz tube 100 is installed. The support structure 400 is installed through a track and can freely enter and exit from the opening to facilitate the insertion and removal of the quartz tube 100.

[0039] In this embodiment, the coating furnace body 200 is divided into three sections in the length direction. The walls of the three sections are the same. The difference is that each section is respectively provided with a heating structure 300, and the temperature can be controlled separately. Generally speaking, if a common heating structure is used, the temperature in the middle area of the coating furnace body 200 will be relatively high, while the temperature in the two end areas will be relatively low. Dividing the coating furnace body 200 into sections and controlling the middle section area to be slightly lower than the two end sections is beneficial to maintaining the temperature uniformity in the cavity 201.

[0040] An external electrode 501 is installed on the inner wall of the coating furnace body 200, and an internal electrode 502 extending into the middle of the cavity 201 is installed at the end of the coating furnace body 200 (the end opposite to the opening). The internal electrode 502 is fixed to the coating furnace body 200 by an insulating base 600. A reaction area is formed between the external electrode 501 and the internal electrode 502, and the length of the reaction area is equal to the length of the quartz tube to be coated. When coating, the quartz tube to be coated is sleeved outside the internal electrode 502 and located in the reaction area.

[0041] In this embodiment, the external electrode and the internal electrode are of equal length and equal to the length of the quartz tube.

[0042] A sealing structure 700 is also provided on the inner wall of the coating furnace body 200. The sealing structure is a high-temperature resistant sealing ring, which is sleeved on the quartz tube and close to the end of the quartz tube.

[0043] On the open side of the coating furnace body 200, an intake structure 10 and an exhaust structure 20 are installed. The intake structure 10 is an intake pipe, and the outlet of the intake pipe is located at the open end of the coating furnace body 200, flush with the end of the inner electrode 502. The exhaust structure 20 is an exhaust pipe, and the inlet of the exhaust pipe is close to the end of the coating furnace body 200 (the end opposite to the opening).

[0044] Example 2

[0045] This example provides a coating device. Refer to Figure 2 , based on Example 1, further structural improvements have been made. Specifically: The inner electrode 502 is rotatably installed on the coating furnace body 200 with an insulating base. The insulating base includes a chassis, a clamping member rotatably installed on the chassis, and a driving motor for driving the clamping member to rotate. The inner electrode 502 is clamped to the clamping member.

[0046] Example 3

[0047] This example provides a coating device. Refer to Figure 2 , based on Example 2, further structural improvements have been made. Specifically: The length of the reaction zone is greater than the length of the quartz tube to be coated. The reaction zone includes a prezone 201a and a postzone 201b. Moreover, the length of the prezone should ensure that it is 1 / 2 or more of the length of the postzone, and the length of the postzone is greater than or equal to the length of the quartz tube. When coating, the quartz tube to be coated is located in the postzone of the reaction zone.

[0048] Example 4

[0049] This example provides a coating device. The modification made on the basis of Example 2 is different from Example 2 in that the outer electrode is of the same length as the inner electrode, less than the length of the quartz tube, and only half of the length of the quartz tube.

[0050] Example 5

[0051] This example provides a method for coating a quartz tube. Using the coating devices of Example 1, Example 2, Example 3, and Example 4 respectively, a silicon carbide thin film is coated on the inner surface of the quartz tube.

[0052] The coating method includes the following steps:

[0053] S-1. Feed the quartz tube to be coated into the inner cavity of the coating furnace. The quartz tube to be coated is sleeved outside the inner electrode, ensuring that the quartz tube is completely placed within the reaction zone;

[0054] S-2. Evacuate the inner cavity of the coating furnace and maintain the inner cavity vacuum at less than 15 mtorr;

[0055] S-3. Raise the temperature of the inner cavity of the coating furnace to 500 °C and adjust the pressure to 1500 mtorr;

[0056] S-4. Introduce methane and silane gases into the reaction area between the inner electrode and the quartz tube to be coated.

[0057] Among them, methane is introduced at a flow rate of 2000 sccm, and silane is introduced at a flow rate of 1000 sccm. Turn on the RF power supply, adjust the power to 25 kW and the frequency to 25 KHz to generate plasma, and deposit a film on the inner surface of the quartz tube to be coated. The reaction time is 10 min.

[0058] Example 6

[0059] This example provides a method for coating a quartz tube. Using the coating equipment of Example 2 and Example 3, a layer of silicon carbide film is deposited on the inner surface of the quartz tube. The coating method includes the following steps:

[0060] S-1. Send the quartz tube to be coated into the inner cavity of the coating furnace. The quartz tube to be coated is sleeved outside the inner electrode to ensure that the quartz tube is completely placed in the rear area of the reaction area;

[0061] S-2. Evacuate the inner cavity of the coating furnace and maintain the inner cavity vacuum less than 15 mtorr;

[0062] S-3. Raise the temperature of the inner cavity of the coating furnace to 500 °C and adjust the pressure to 1500 mtorr;

[0063] S-4. Introduce methane and silane gases into the reaction area between the inner electrode and the quartz tube to be coated.

[0064] Among them, methane is introduced at a flow rate of 2000 sccm, and silane is introduced at a flow rate of 1000 sccm. Turn on the RF power supply, adjust the power to 25 kW and the frequency to 25 KHz to generate plasma, and deposit a film on the inner surface of the quartz tube to be coated. The reaction time is 10 min. During this period, the inner electrode rotates at a speed of 10 rpm.

[0065] Example 6

[0066] This example provides a method for coating a quartz tube. Using the coating equipment of Example 2 and Example 3, a layer of silicon carbide film is deposited on the inner surface of the quartz tube. The coating method includes the following steps:

[0067] S-1. Send the quartz tube to be coated into the inner cavity of the coating furnace. The quartz tube to be coated is sleeved outside the inner electrode to ensure that the quartz tube is completely placed in the rear area of the reaction area;

[0068] S-2. Evacuate the inner cavity of the coating furnace and maintain the inner cavity vacuum less than 15 mtorr;

[0069] S-3. Raise the temperature of the inner cavity of the coating furnace to 450 °C and adjust the pressure to 2000 mtorr;

[0070] S-4. Introduce methane and silane gases into the reaction zone between the inner electrode and the quartz tube to be coated.

[0071] Among them, methane is introduced at a flow rate of 3500 sccm, and silane is introduced at a flow rate of 2000 sccm. Turn on the RF power supply, adjust the power to 35 kW and the frequency to 25 KHz to generate plasma, deposit a film on the inner surface of the quartz tube to be coated, with a reaction time of 10 min. During this period, the inner electrode rotates at a speed of 10 rpm.

[0072] Detect the thickness uniformity of the film formed on the inner surface of the quartz tube by the methods of Examples 5 to 7.

[0073] Detection method: Select 5 points on the inner wall of the quartz tube (for the selection positions of the 5 points, see Figure 3 , in the middle, evenly select three points in the circumferential direction of the quartz tube, and randomly select one point at the front of the quartz tube and one point at the rear of the quartz tube (denoted as point 1, point 2, point 3, point 4, and point 5 respectively)), and use an ellipsometer to measure the film thickness.

[0074] The uniformity calculation formula is as follows:

[0075] Thickness uniformity = [(maximum film thickness - minimum film thickness) / (2 * average film thickness)] * 100%.

[0076] Detection results: See Table 1.

[0077] Table 1 Thickness of the silicon carbide films formed in each example

[0078]

[0079] It can be seen from Table 1 that by using the coating equipment and method of the present invention, the silicon carbide film formed on the inner surface of the quartz tube has good thickness uniformity.

[0080] Specifically, using the coating equipment of Examples 1-2 and implementing the coating method of Example 5, although the structure of the inner electrode in Example 2 can rotate, during the coating process, the inner electrode was not rotated, and the film uniformity obtained was comparable. Using the coating equipment of Example 3 and implementing the coating method of Example 5, due to the setting of the front zone and the rear zone, the film uniformity obtained is better than that of the coating equipment of Examples 1-2 without the front zone, indicating that the setting of the front zone is beneficial to improving the thickness uniformity of the silicon carbide film formed on the inner surface of the quartz tube to a certain extent.

[0081] Using the coating equipment of Embodiment 2-3, the coating method of Embodiment 6 was implemented. Compared with the method of Embodiment 5, in the reaction stage (i.e., Step S-4), the inner electrode rotates at a fixed speed. The obtained film has better uniformity, indicating that the rotation of the inner electrode is beneficial to improving the thickness uniformity of the silicon carbide film formed on the inner surface of the quartz tube to a certain extent. For the coating equipment of Embodiment 3, compared with the coating equipment of Embodiment 2, a pre-region is set, and the obtained film has better uniformity, indicating that the setting of the pre-region is beneficial to improving the thickness uniformity of the silicon carbide film formed on the inner surface of the quartz tube to a certain extent. Similarly, using the coating equipment of Embodiment 2-3 and implementing the coating method of Embodiment 7 can also illustrate the above effects.

[0082] To study the influence of the rotation speed of the inner electrode on the film properties, the present invention also uses the coating equipment of Embodiment 2 and coats the quartz tube by adjusting the different rotation speeds of the inner electrode and adopting the method of Embodiment 7. The results are shown in Table 2 (the rotation speeds are different, and other conditions are the same as those of Embodiment 7).

[0083] Table 2 Thickness of silicon carbide films formed under different rotation speeds of the inner electrode

[0084]

[0085] It can be seen from Table 2 that when the rotation speed of the inner electrode is controlled within the range of 5 rpm to 25 rpm, the thickness uniformity of the silicon carbide film formed on the inner surface of the quartz tube is better. When the rotation speed of the inner electrode exceeds 30 rpm, due to excessive disturbance, the thickness uniformity of the silicon carbide film becomes worse, and even has a negative effect, which is worse than the effect when the inner electrode is fixed and does not rotate.

Claims

1. A coating device for a quartz tube of a chemical vapor deposition tube furnace, characterized in that: The invention comprises a coating furnace body, an outer electrode arranged on the inner wall of the coating furnace body, an inner electrode arranged in the inner cavity of the coating furnace body, a radio frequency power supply electrically connected to the inner electrode and the outer electrode, a heating structure for providing heat to the inner cavity of the coating furnace body, a supporting structure arranged in the inner cavity of the coating furnace body for supporting a quartz tube to be coated, and an air inlet structure and an air outlet structure arranged at the end of the coating furnace body. A reaction area is formed between the outer electrode and the inner electrode. During coating, the quartz tube to be coated is sleeved outside the inner electrode and is located in the reaction area. The air inlet structure introduces working gas between the quartz tube to be coated and the inner electrode. The working gas is electrolyzed into plasma under the action of electricity supplied to the inner electrode and the outer electrode.

2. A quartz tube coating device according to claim 1, characterized in that: The coating furnace body adopts a multi-section type, and each section of the coating furnace body corresponds to an independent heating structure.

3. The quartz tube coating device according to claim 1, characterized in that: The inner electrode is installed at the end of the coating furnace body through a rotating base, and the inner electrode rotates under the drive of the rotating base.

4. The quartz tube coating device according to claim 3, characterized in that: The reaction area includes a front area close to the opening and a rear area far from the opening. During coating, the quartz tube to be coated is located in the rear area of ​​the reaction area. In the front area, the working gas begins to be decomposed into active groups, and the active groups move forward to the rear area under the action of the airflow.

5. The quartz tube coating device according to claim 4, characterized in that: The length of the pre-zone is 1 / 2 or more of the length of the post-zone.

6. A coating method using the coating device according to any one of claims 1 to 5, characterized in that: At least the following steps are included: S-1. The quartz tube to be coated is sent into the inner cavity of the coating furnace, and the quartz tube to be coated is sleeved outside the inner electrode; S-2. Evacuate the inner cavity of the coating furnace to maintain the inner cavity vacuum; S-3. Raise the temperature of the coating furnace cavity to T and adjust the pressure to P; S-4. Introduce working gas into the area between the inner electrode and the quartz tube to be coated, turn on the RF power supply to generate plasma, and deposit a thin film on the inner surface of the quartz tube to be coated.

7. The coating method according to claim 6, characterized in that: In step S-4, the inner electrode is rotated at a rotation speed of 10 rpm to 25 rpm.

8. The coating method according to claim 6, characterized in that: In step S-4, the working gases are methane and monosilane, the flow rate of methane is 1000-5000 sccm, and the flow rate of monosilane is 1000-2500 sccm.

9. The coating method according to claim 6, characterized in that: After the deposition is completed in step S-4, a low-temperature inert gas is introduced into the inner cavity of the coating furnace.

10. A quartz tube, characterized in that: By the coating method described in any one of claims 6 to 9, a silicon carbide film is formed on the inner surface of a quartz tube for use in a chemical vapor deposition tube furnace.

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