LPCVD (Low Pressure Chemical Vapor Deposition) equipment for online cleaning of quartz tube and online cleaning method

Abstract

According to the LPCVD equipment for online cleaning of the quartz tube and the online cleaning method, a quartz boat is placed in the quartz tube, the quartz tube is embedded in the inner side of a heating furnace body, and the two ends of the quartz tube are connected with a furnace door and a furnace tail flange through a furnace opening door plate and a furnace tail door plate respectively; air inlet spraying pipes are arranged on the furnace mouth door plate and the furnace door; an exhaust pipe connected with a vacuum pump is arranged on the furnace tail flange; one end of the I CP electrode bar is fixed on the furnace tail flange and connected with the radio frequency power supply assembly, and the other end of the I CP electrode bar penetrates through the furnace tail flange and extends into the quartz tube, and a gap exists between the I CP electrode bar and the quartz boat; fluoride gas is introduced into the quartz tube, the radio frequency power supply assembly is turned on, under the action of the ICP electrode bar, the fluoride gas forms fluorine plasma in the quartz tube, the fluorine plasma reacts with amorphous silicon on the inner wall of the quartz tube and amorphous silicon on the quartz boat, and therefore synchronous online cleaning of the quartz tube and the quartz boat is achieved. The device has the advantages of compact structure, convenience in operation, high cleaning efficiency, low cost and the like.

Description

Technical Field

[0001] This invention belongs to the field of LPCVD equipment technology, specifically relating to an LPCVD device and online cleaning method for quartz tubes. Background Technology

[0002] TOPCon battery fabrication utilizes LPCVD to prepare tunneling silicon oxide and amorphous silicon. However, due to the significant difference in thermal expansion coefficients between the quartz tube in the LPCVD equipment and amorphous silicon, the quartz tube is prone to breakage under thermal stress when the amorphous silicon film on its wall is thick. This poses a significant safety risk, requiring regular replacement of the quartz tube, thus increasing the manufacturing cost of TOPCon batteries. Currently, battery manufacturers lack effective methods to prevent quartz tube breakage in LPCVD equipment, typically replacing them every 2-3 months. This greatly increases the amount of quartz tubes used, further raising the operating cost of the LPCVD equipment. Furthermore, the limited production capacity of high-purity quartz has led to a continuous rise in quartz tube prices. In addition, current LPCVD equipment generally employs a multi-tube integrated design, with LPCVD reactors containing 5 or 6 tubes per unit. Disassembling and reassembling the quartz tubes during replacement reduces equipment uptime and is also quite difficult.

[0003] Currently, in the photovoltaic industry, quartz tubes are replaced directly after reaching the end of their service life. However, in the semiconductor industry, the cleaning of quartz tubes primarily involves chemical solution cleaning. This involves immersing the quartz tube in acidic or alkaline solutions for an extended period to clean the thin film or contaminants on its surface, followed by rinsing and drying. This method requires removing the quartz tube from the equipment, and the cleaning, rinsing, and drying processes are time-consuming and lack timeliness.

[0004] Chinese patent application CN202320357616 discloses an LPCVD quartz tube cleaning device. This solution involves placing a capacitively coupled plasma discharge (VCP) device inside the quartz chamber to ionize fluoride gas into fluoride ions, thereby cleaning the quartz tube. While this method also employs dry plasma cleaning of the quartz tube, the VCP device is relatively large, requiring disassembly and reassembly. When cleaning is needed, the discharge device must be placed inside the quartz tube and electrode rods installed, making online cleaning impossible and impacting the LPCVD equipment's throughput. Furthermore, this solution uses VCP, which results in a relatively low plasma density, potentially leading to a slower cleaning speed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an LPCVD device and method for online cleaning of quartz tubes that is compact, easy to operate, highly efficient, and low-cost. This solves the problems in existing technologies where dry cleaning cannot achieve online cleaning, and where simultaneous cleaning of the quartz tube and quartz boat is impossible due to the need for a customized discharge system inside the quartz tube. To achieve the above objectives, this invention can adopt the following technical solution:

[0006] An online LPCVD device for cleaning quartz tubes includes: a heating furnace body, a quartz tube, an ICP electrode rod, a furnace door, and a furnace tail flange; a quartz boat is placed inside the quartz tube, and the quartz tube is nested inside the heating furnace body, which is used to heat the quartz tube; both ends of the quartz tube are connected to the furnace door and the furnace tail flange respectively through a furnace inlet door plate and a furnace tail door plate; the furnace inlet door plate and the furnace door are equipped with air inlet spray pipes to deliver process gas into the quartz tube; the furnace tail flange is equipped with a suction pipe connected to a vacuum pump to discharge gas from the quartz tube; one end of the ICP electrode rod is fixed to the furnace tail flange and connected to an RF power supply assembly, and the other end of the ICP electrode rod extends through the furnace tail flange into the quartz tube, with a gap between it and the quartz boat; by introducing fluoride gas into the quartz tube and turning on the RF power supply assembly, the process gas is heated. Under the action of the CP electrode rod, fluoride gas forms fluorine plasma in the quartz tube, which reacts with the amorphous silicon on the inner wall of the quartz tube and the quartz boat to achieve synchronous online cleaning of the quartz tube and the quartz boat.

[0007] As a further improvement of the present invention, multiple ICP electrode rods are evenly distributed on the inner edge of the quartz tube, and there are gaps between the ICP electrode rods and the inner wall of the quartz tube and the quartz boat, and every two ICP electrode rods share a radio frequency power supply assembly.

[0008] As a further improvement of the present invention, the ICP electrode rod includes: a support rod, a copper coil, and a sealing flange; one end of the support rod is fixed to the furnace tail flange through the sealing flange, and the other end of the support rod extends into the quartz tube; the copper coil is evenly wound on the support rod, the upper electrode of the copper coil passes through the sealing flange and is connected to the radio frequency power supply assembly, and the lower electrode of the copper coil passes through the sealing flange and is connected to the grounding wire.

[0009] As a further improvement of the present invention, a ceramic spacer is provided between the copper coil and the sealing flange, the ceramic spacer being used to achieve insulation separation between the copper coil and the sealing flange.

[0010] As a further improvement of the present invention, the upper electrode is provided with a terminal block for connecting to the radio frequency power supply assembly.

[0011] As a further improvement of the present invention, the copper coil is a hollow coil, and the end of the hollow coil is provided with a cooling water inlet and outlet to realize the circulation of cooling water into the copper coil.

[0012] As a further improvement of the present invention, the furnace tail flange is provided with an observation window for observing the glow discharge state inside the quartz tube.

[0013] As a further improvement of the present invention, a thermocouple is provided on the furnace tail flange for monitoring the temperature inside the quartz tube.

[0014] As a further improvement of the present invention, the air inlet spray pipe is located at the bottom of the quartz tube and extends from the furnace mouth of the quartz tube to the furnace tail; the air inlet spray pipe has a number of holes with a diameter of 0.5 to 1 mm evenly distributed on it, with the holes opening upwards.

[0015] As a further improvement of the present invention, the radio frequency power supply assembly includes a power matching unit and a radio frequency power supply.

[0016] As a general technical concept, the present invention also provides an online cleaning method for LPCVD equipment based on the above-mentioned online cleaning of quartz tubes, comprising the following steps:

[0017] Step S1: After the LPCVD equipment continuously deposits multiple layers of amorphous silicon thin films to >20μm, turn off the heating of the LPCVD equipment, close the furnace door and start vacuuming;

[0018] Step S2: When the pressure inside the quartz tube is pumped down to below 1 Pa, process gas is introduced to keep the pressure inside the quartz tube within 10 to 200 Pa.

[0019] Step S3: Apply an RF power supply to the ICP electrode rod. The power supply frequency is 13.56MHz and the power is 500-5000W. The process gas is ionized under the action of the RF power supply to generate high-energy disordered fluorine plasma, argon plasma and active fluorine radical plasma.

[0020] Step S4: Under the action of the vacuum pump, the active fluorine radical particles generated near the ICP electrode rod diffuse into the entire quartz tube and react chemically with the doped amorphous silicon thin film on the surface of the quartz tube to form SiF4 and volatile byproducts, thereby causing the pressure inside the quartz tube to rise rapidly and remain within a certain range.

[0021] Step S5: When the amorphous silicon film on the quartz tube wall is cleaned, the pressure inside the quartz tube drops rapidly, indicating that the etching and cleaning endpoint has been reached.

[0022] Step S6: Turn off the RF power supply and stop the process gas supply. After cleaning and vacuuming, fill the furnace with nitrogen to atmospheric pressure and open the furnace door to check the cleaning effect.

[0023] As a further improvement of the present invention, in step S2, the process gas is a mixture of CF4 and O2, or a mixture of SF6 and Ar, or a mixture of NF3 and Ar, and the total flow rate of the process gas is 500 to 5000 sccm.

[0024] Compared with the prior art, the advantages of the present invention are as follows:

[0025] 1. The LPCVD equipment for online cleaning of quartz tubes of the present invention, by nesting the quartz tube for placing the quartz boat inside the heating furnace body and heating the quartz tube using the heating furnace body, can perform the corresponding process; both ends of the quartz tube are connected to the furnace door and furnace tail flange respectively through the furnace inlet door plate and furnace tail door plate, respectively, and the process gas is delivered to the quartz tube by the gas inlet spray pipe, and the gas in the quartz tube is discharged by the gas extraction pipe connected to the vacuum pump; at the same time, one end of the ICP electrode rod is fixed to the furnace tail flange and connected to the radio frequency power supply assembly, and the other end of the ICP electrode rod extends through the furnace tail flange into the quartz tube, with a gap between it and the quartz boat, so as not to affect the normal entry and exit of the quartz boat, thereby realizing the online cleaning function of the quartz tube, and can also greatly improve the uniformity of the plasma, thereby reducing the over-etching problem in the quartz tube; by introducing fluoride gas into the quartz tube and turning on the radio frequency power supply assembly, in I Under the action of the ICP electrode rod, fluoride gas forms fluorine plasma in the quartz tube, which reacts with the amorphous silicon on the inner wall of the quartz tube and the quartz boat, achieving simultaneous online cleaning of the quartz tube and the quartz boat. This invention directly integrates the ICP electrode rod into the LPCVD equipment, and the high plasma density generated by the ICP discharge enables a faster cleaning rate. Because the ICP electrode rod is uniformly distributed along the edge of the quartz tube sidewall, the etching fluorine plasma is evenly distributed throughout the entire quartz tube. Furthermore, it does not affect the normal entry and exit of the quartz boat carrier, thus achieving the goal of simultaneously cleaning the quartz tube cavity wall and the quartz boat.

[0026] 2. The online cleaning method of the present invention is based on the fact that the reaction rate of fluorine radicals with amorphous silicon is faster than that of quartz. Therefore, after the amorphous silicon on the quartz tube wall is cleaned during the cleaning process, the amount of SiF4 gas generated decreases rapidly, resulting in a sudden change in pressure inside the quartz tube. The pressure change is used to determine whether the amorphous silicon film on the quartz tube wall has been etched and cleaned. This allows the plasma generator to be shut down in time, reducing its etching effect on the quartz tube and improving the service life of the quartz tube. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the main structural principle of the LPCVD equipment for online cleaning of quartz tubes in a specific embodiment of the present invention;

[0028] Figure 2This is a side view schematic diagram of the LPCVD equipment for online cleaning of quartz tubes in a specific embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of the main structural principle of the ICP electrode rod in a specific embodiment of the present invention;

[0030] Figure 4 This is a side view schematic diagram of the ICP electrode rod in a specific embodiment of the present invention;

[0031] Figure 5 This is a schematic diagram of the online etching and cleaning process in a specific embodiment of the present invention;

[0032] Figure 6 This is a schematic diagram of the pressure changes inside the quartz tube during the etching and cleaning process in a specific embodiment of the present invention;

[0033] Legend: 1. Heating furnace body; 2. Quartz tube; 3. ICP electrode rod; 4. Furnace opening insulation cotton ring; 5. Furnace opening door panel; 6. Furnace door; 7. Air inlet spray pipe; 8. Furnace tail insulation cotton ring; 9. Furnace tail door panel; 10. Furnace tail flange; 11. Power matching device; 12. RF power supply; 13. Grounding wire; 14. Evacuation pipe; 15. Observation window; 16. Thermocouple; 31. Support rod; 32. Copper coil; 33. Sealing flange; 34. Ceramic spacer; 35. Upper electrode; 36. Lower electrode; 37. Terminal block; 38. Nut. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0035] In the description of this invention, it should be understood that the terms "side", "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more unless otherwise explicitly specified.

[0037] Example

[0038] like Figures 1 to 4 As shown, the online cleaning LPCVD equipment for quartz tubes of the present invention includes: a heating furnace body 1, a quartz tube 2, an ICP electrode rod 3, a furnace door 6, and a furnace tail flange 10. A quartz boat is placed inside the quartz tube 2, and the quartz tube 2 is nested inside the heating furnace body 1, which is used to heat the quartz tube 2. The furnace opening of the quartz tube 2 is connected to the furnace door 6 via a furnace opening door plate 5, and the furnace tail of the quartz tube 2 is connected to the furnace tail flange 10 via a furnace tail door plate 9. An inlet spray pipe 7 is provided on the furnace opening door plate 5 and the furnace door 6 to deliver process gas into the quartz tube 2. A suction pipe 14 connected to a vacuum pump is provided on the furnace tail flange 10 to discharge gas from the quartz tube 2. One end of the ICP electrode rod 3 is fixed to the furnace tail flange 10 and connected to an RF power supply assembly. The other end of the ICP electrode rod 3 extends through the furnace tail flange 10 into the quartz tube 2, with a gap between it and the quartz boat. By introducing fluoride gas into the quartz tube 2 and turning on the radio frequency power supply assembly, under the action of the ICP electrode rod 3, the fluoride gas forms fluorine plasma in the quartz tube 2, which reacts with the amorphous silicon on the inner wall of the quartz tube 2 and the quartz boat, thereby achieving synchronous online cleaning of the quartz tube 2 and the quartz boat. In this embodiment, the radio frequency power supply assembly includes a power matching unit 11 and a radio frequency power supply 12, and the power frequency of the radio frequency power supply 12 is 13.56MHz.

[0039] like Figure 2 As shown, in this embodiment, there are four ICP electrode rods 3, distributed in the four directions (up, down, left, and right) inside the quartz tube 2. Gaps exist between the ICP electrode rods 3 and the inner wall of the quartz tube 2 and the quartz boat. This greatly improves the uniformity of the plasma, thereby preventing over-etching in certain parts of the quartz tube. Furthermore, every two ICP electrode rods 3 share one radio frequency power supply 12; therefore, two radio frequency power supplies 12 are required for the four ICP electrode rods.

[0040] In this embodiment, LPCVD can normally prepare amorphous silicon and tunneling silicon oxide thin films. Only when the amorphous silicon thin film on the quartz tube wall is relatively thick, periodically using the ICP electrode rod 3 to discharge and form fluorine plasma to clean the quartz tube 2 is required. During normal amorphous silicon processes, the ICP electrode rod 3 is not operational. High-density, high-energy, fluorine-containing active plasma is obtained by ionizing fluoride gas through inductively coupled plasma rod discharge. This plasma reacts with the amorphous silicon or silicon oxide thin film on the quartz tube wall to produce volatile gaseous substances, thus enabling rapid cleaning of the quartz tube. Simultaneously, a quartz boat can also be placed inside the quartz tube for synchronous cleaning.

[0041] In this embodiment, the heating furnace body 1 is cylindrical, filled with insulation material and evenly distributed heating wires, and encased in stainless steel. The length of the heating furnace body 1 is less than the length of the quartz tube 2. The excess portion of the quartz tube 2 is covered by furnace mouth insulation rings 4 and furnace tail insulation rings 8 to reduce heat loss within the furnace. The quartz tube 2 is then fixed in place by furnace mouth door plates 5 and furnace tail door plates 9. The furnace door 6 is controlled by a motor to open and close, providing a seal for the quartz tube 2. The furnace door 6 is a combination of a quartz furnace door and a stainless steel furnace door, joined together by a quartz furnace door pressure ring, with the quartz furnace door on the inside and the stainless steel furnace door on the outside, thus reducing metal contamination inside the furnace. The furnace tail of the quartz tube 2 is sealed by a furnace tail flange 10, with an opening in the center of the flange housing an extraction pipe 14. The extraction pipe 14 is connected to a butterfly valve and a vacuum pump. The butterfly valve controls the pressure inside the quartz tube 2, and the vacuum pump provides a vacuum environment inside the quartz tube 2. With the furnace tail flange 10 and furnace door 6 closed, a sealed environment is provided for the quartz tube 2. The air inlet spray pipe 7 is connected to the air inlet structure at the furnace mouth of the quartz tube 2. The air inlet spray pipe 7 is located at the bottom of the quartz tube 2 and extends from the furnace mouth of the quartz tube 2 to the furnace tail. The air inlet spray pipe 7 has several holes with a diameter of 0.5 to 1 mm evenly distributed on it. The holes open upwards and are used to evenly introduce fluoride gases such as NF3, CF4, SF6, NF3 / Ar, CH4 / O2, or SF6 / Ar, or a mixture of fluoride gases with Ar and O2 into the quartz tube 2, thereby forming a uniform gas field distribution inside the quartz tube 2.

[0042] like Figure 3 and Figure 4 As shown, in this embodiment, the ICP electrode rod 3 includes a support rod 31, a copper coil 32, and a sealing flange 33. One end of the support rod 31 is fixed to the furnace tail flange 10 via the sealing flange 33 and a nut 38, and the other end of the support rod 31 extends into the quartz tube 2. The copper coil 32 is evenly wound on the support rod 31. The upper electrode 35 of the copper coil 32 passes through the sealing flange 33 and is connected to the radio frequency power supply assembly, and the lower electrode 36 of the copper coil 32 passes through the sealing flange 33 and is connected to the grounding wire 13.

[0043] Furthermore, the upper electrode 35 is provided with a terminal 37 for connecting to the radio frequency power supply 12, and is rigidly connected to the back end of the power matching unit 11.

[0044] like Figure 4 As shown, in this embodiment, a ceramic spacer 34 is provided between the copper coil 32 and the sealing flange 33. The ceramic spacer 34 is used to achieve insulation separation between the copper coil 32 and the sealing flange 33.

[0045] In this embodiment, the copper coil 32 is a hollow coil, and the end of the hollow coil is provided with a cooling water inlet and outlet to allow circulating cooling water to flow into the copper coil 32. The cooling water can maintain a very steep temperature gradient around the coil and the discharge chamber, which is beneficial to extending the life of the coil and the discharge chamber.

[0046] In the LPCVD amorphous silicon thin film deposition process, the ICP electrode rod 3 is not in operation. However, when the amorphous silicon deposition on the inner wall of the quartz tube 2 is thick, online plasma cleaning of the quartz tube 2 can be performed without any equipment modifications. After closing the furnace door 6, the cleaning process can be started by evacuating the vacuum. Fluoride gases such as NF3, CF4, SF6, NF3 / Ar, CH4 / O2, or SF6 / Ar, or a mixture of fluorides with Ar and O2, are introduced into the quartz chamber through the air inlet spray pipe 7. After reaching the set pressure value, the RF power supply 12 is turned on. After the impedance and other parameters are matched by the power matching device 11, under the action of the RF power supply 12, the process gas is decomposed into NF3 near the ICP electrode rod 3 by the electric and magnetic fields. + ,NF 2 + ,F - ,F * ,NF * NF2 * Plasma and active groups diffuse to the entire inner wall of the quartz tube 2 under low pressure, reacting with amorphous silicon to form volatile gaseous products such as SiF4, which are then pumped away by a vacuum pump, thereby achieving the purpose of cleaning the quartz tube 2.

[0047] like Figure 2 As shown, in this embodiment, the furnace tail flange 10 is provided with an observation window 15 for observing the glow discharge state inside the quartz tube 2. At the same time, the discharge uniformity of the ICP electrode rod 3 can be adjusted through the observation window 15.

[0048] like Figure 2 As shown, in this embodiment, a thermocouple 16 is provided on the furnace tail flange 10 to monitor the temperature inside the quartz tube 2.

[0049] like Figure 5 As shown, in this embodiment, the online cleaning of quartz tube 2 alone includes the following steps:

[0050] Step S1: After the LPCVD equipment continuously deposits multiple layers of amorphous silicon thin films to >20μm, turn off the heating of the LPCVD equipment, close the furnace door 6, and start vacuuming.

[0051] Step S2: When the pressure inside the quartz tube 2 is pumped down to below 1 Pa, process gas is introduced to keep the pressure inside the quartz tube 2 within 10 to 200 Pa. The process gas is a mixture of CF4 and O2, or a mixture of SF6 and Ar, or a mixture of NF3 and Ar, etc., and the total gas flow rate is 500 to 5000 sccm.

[0052] Step S3: Apply an radio frequency power supply to the ICP electrode rod 3. The power supply frequency is 13.56MHz, and the power is 500-5000W. Select the preferred power within this range and use the power matching device 11 to achieve the best matching effect. The process gas will be ionized under the action of the radio frequency power supply 12 to generate high-energy disordered fluorine plasma, argon plasma, and active fluorine radical plasma.

[0053] Step S4: Under the action of the vacuum pump, the active fluorine radical particles generated near the ICP electrode rod 3 diffuse into the entire quartz tube 2 and react chemically with the doped amorphous silicon thin film on the surface of the quartz tube 2 to form SiF4 and other volatile byproducts, thereby causing the pressure inside the quartz tube 2 to rise rapidly and remain within a certain range.

[0054] Step S5: After a period of reaction, the amorphous silicon film on the quartz tube wall is completely cleaned. At this point, the pressure drops rapidly, indicating that the etching cleaning endpoint has been reached. Figure 6 As shown.

[0055] Step S6: Turn off the RF power supply 12 and stop the process gas flow. After cleaning and vacuuming, fill the furnace with nitrogen to atmospheric pressure and open the furnace door 6 to check the cleaning effect.

[0056] In this embodiment, the online cleaning of both the quartz tube 2 and the quartz boat includes the following steps:

[0057] Step Y1: After the LPCVD equipment deposits a single-layer amorphous silicon thin film (100-200nm), a cleaning step is added after the amorphous silicon thin film deposition process is completed.

[0058] Step Y2: After the quartz boat is launched, close the furnace door 6 and begin vacuuming.

[0059] Step Y3: When the pressure inside the quartz tube 2 is pumped down to below 1 Pa, process gas is introduced to keep the pressure inside the quartz tube 2 within 10 to 200 Pa. The process gas is a mixture of CF4 and O2, or a mixture of SF6 and Ar, or a mixture of NF3 and Ar, etc., with a total gas flow rate of 500 to 5000 sccm.

[0060] Step Y4: Apply a 13.56MHz radio frequency power supply to the ICP electrode rod 3. The power supply power is between 500 and 5000W, with the preferred power selected within this range. Use the power matching device 11 to achieve the best matching effect. The process gas will be ionized under the action of the radio frequency power supply 12 to generate high-energy disordered fluorine plasma, argon plasma, and active fluorine radical plasma.

[0061] Step Y5: Under the action of the vacuum pump, the active fluorine radical particles generated near the ICP electrode rod diffuse into the entire quartz tube and react chemically with the doped amorphous silicon thin film on the surface of the quartz tube to form SiF4 and other volatile byproducts, thereby causing the pressure inside the quartz tube 2 to rise rapidly and remain within a certain range.

[0062] Step Y6: When the amorphous silicon film on the quartz tube wall is cleaned, the pressure inside the quartz tube 2 drops rapidly, indicating that the etching and cleaning endpoint has been reached.

[0063] Step Y7: Turn off the RF power supply 12 and stop the process gas flow. After cleaning and evacuation, fill with nitrogen to atmospheric pressure and continue the amorphous silicon thin film deposition process and the quartz tube online cleaning process.

[0064] In this embodiment, dry cleaning is used to remove the amorphous silicon thin film coating on the inner wall surface of the quartz tube. Fluorinated gas (CF4, SF6, or NF3) or a mixture thereof with Ar, O2, or H2 is used as the process gas. Inductively coupled plasma (ICP) rods discharge to generate fluorine plasma and fluorine-containing active free radical particles inside the quartz tube. These particles react with the amorphous silicon thin film under low pressure to obtain volatile gaseous substances such as SiF4, thereby cleaning the coating on the inner wall of the quartz tube. Furthermore, since the ICP electrode rods in this embodiment are distributed at the edge of the quartz tube, they do not affect the normal entry and exit of the quartz boat carrier. When the quartz boat carrier is placed inside the quartz tube, the fluorine free radical particles diffuse onto the quartz boat due to the low-pressure cleaning environment, allowing for simultaneous online cleaning of the quartz boat. Its advantages are: 1) Quartz tubes do not need to be soaked in strong acid or alkali solutions, reducing cleaning time, industrial wastewater treatment, and production costs; 2) Regular cleaning of quartz tubes can greatly extend their service life; 3) Online cleaning can be achieved without any disassembly or assembly of the equipment, reducing disassembly and assembly risks and increasing the uptime of LPCVD equipment; 4) Simultaneous cleaning of quartz tubes and quartz boats can be achieved, reducing cleaning costs; 5) Pressure changes can be used to determine whether the amorphous silicon film on the quartz tube wall has been etched and cleaned thoroughly, allowing for timely shutdown of the plasma generator to reduce its etching of the quartz tube and extend its service life.

[0065] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the scope of protection of this technical solution.

Claims

1. An LPCVD device for online cleaning of quartz tubes, characterized in that, include: The furnace consists of a heating furnace body (1), a quartz tube (2), an ICP electrode rod (3), a furnace door (6), and a furnace tail flange (10). A quartz boat is placed inside the quartz tube (2), which is nested inside the heating furnace body (1). The heating furnace body (1) is used to heat the quartz tube (2). The two ends of the quartz tube (2) are connected to the furnace door (6) and the furnace tail flange (10) respectively through the furnace opening door plate (5) and the furnace tail door plate (9). The furnace opening door plate (5) and the furnace door (6) are equipped with air inlet spray pipes (7) to deliver process gas into the quartz tube (2). The furnace tail flange (10) is equipped with a vacuum pump connected to a vacuum pump. A gas tube (14) is used to discharge the gas inside the quartz tube (2); one end of the ICP electrode rod (3) is fixed to the furnace tail flange (10) and connected to the radio frequency power supply assembly, and the other end of the ICP electrode rod (3) extends through the furnace tail flange (10) into the quartz tube (2) and there is a gap between it and the quartz boat; by introducing fluoride gas into the quartz tube (2) and turning on the radio frequency power supply assembly, under the action of the ICP electrode rod (3), the fluoride gas forms fluorine plasma in the quartz tube (2) and reacts with the amorphous silicon on the inner wall of the quartz tube (2) and the quartz boat to achieve synchronous online cleaning of the quartz tube (2) and the quartz boat.

2. The LPCVD equipment for online cleaning of quartz tubes according to claim 1, characterized in that, Multiple ICP electrode rods (3) are evenly distributed on the inner edge of the quartz tube (2). There are gaps between the ICP electrode rods (3) and the inner wall of the quartz tube (2) and the quartz boat. Each pair of ICP electrode rods (3) shares a radio frequency power supply component.

3. The LPCVD equipment for online cleaning of quartz tubes according to claim 2, characterized in that, The ICP electrode rod (3) includes: a support rod (31), a copper coil (32), and a sealing flange (33); one end of the support rod (31) is fixed to the furnace tail flange (10) through the sealing flange (33), and the other end of the support rod (31) extends into the quartz tube (2); the copper coil (32) is evenly wound on the support rod (31), the upper electrode (35) of the copper coil (32) passes through the sealing flange (33) and is connected to the radio frequency power supply assembly, and the lower electrode (36) of the copper coil (32) passes through the sealing flange (33) and is connected to the grounding wire (13).

4. The LPCVD equipment for online cleaning of quartz tubes according to claim 3, characterized in that, A ceramic spacer (34) is provided between the copper coil (32) and the sealing flange (33), and the ceramic spacer (34) is used to achieve insulation separation between the copper coil (32) and the sealing flange (33).

5. The LPCVD equipment for online cleaning of quartz tubes according to claim 3, characterized in that, The upper electrode (35) is provided with a terminal (37), which is used to connect to the radio frequency power supply assembly.

6. The LPCVD equipment for online cleaning of quartz tubes according to claim 3, characterized in that, The copper coil (32) is a hollow coil, and the end of the hollow coil is provided with a cooling water inlet and outlet to allow circulating cooling water to flow into the copper coil (32).

7. The LPCVD equipment for online cleaning of quartz tubes according to any one of claims 1 to 6, characterized in that, The furnace tail flange (10) is provided with an observation window (15) and a thermocouple (16). The observation window (15) is used to observe the glow discharge state inside the quartz tube (2), and the thermocouple (16) is used to monitor the temperature inside the quartz tube (2).

8. The LPCVD equipment for online cleaning of quartz tubes according to any one of claims 1 to 6, characterized in that, The air inlet spray pipe (7) is located at the bottom of the quartz tube (2) and extends from the furnace mouth of the quartz tube (2) to the furnace tail; the air inlet spray pipe (7) has several holes with a diameter of 0.5 to 1 mm evenly distributed on it, with the holes opening upwards.

9. An online cleaning method for an LPCVD equipment based on the online cleaning of quartz tubes according to any one of claims 1 to 8, characterized in that, Includes the following steps: Step S1: After the LPCVD equipment continuously deposits multiple layers of amorphous silicon thin films to >20μm, turn off the heating of the LPCVD equipment, close the furnace door and start vacuuming; Step S2: When the pressure inside the quartz tube (2) is pumped down to below 1 Pa, process gas is introduced to keep the pressure inside the quartz tube (2) within 10 to 200 Pa. Step S3: Apply an RF power supply to the ICP electrode rod (3). The power supply frequency is 13.56MHz and the power supply power is 500~5000W. The process gas is ionized under the action of the RF power supply to generate high-energy disordered fluorine plasma, argon plasma and active fluorine free radical plasma. Step S4: Under the action of the vacuum pump, the active fluorine radical particles generated near the ICP electrode rod (3) diffuse into the entire quartz tube (2) and react chemically with the doped amorphous silicon thin film on the surface of the quartz tube (2) to form SiF4 and volatile byproducts, thereby causing the pressure inside the quartz tube (2) to rise rapidly and remain within a certain range. Step S5: When the amorphous silicon film on the quartz tube wall is cleaned, the pressure inside the quartz tube (2) drops rapidly, indicating that the etching cleaning endpoint has been reached. Step S6: Turn off the RF power supply and stop the process gas supply. After cleaning and vacuuming, fill the furnace with nitrogen to atmospheric pressure and open the furnace door (6) to check the cleaning effect.

10. The online cleaning method according to claim 9, characterized in that, In step S2, the process gas is a mixture of CF4 and O2, or a mixture of SF6 and Ar, or a mixture of NF3 and Ar, and the total flow rate of the process gas is 500 to 5000 sccm.

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