Novel polycrystalline silicon thin film structure for field effect passivation of crystalline silicon cell and PECVD (Plasma Enhanced Chemical Vapor Deposition) equipment

Abstract

The invention discloses a novel polycrystalline silicon thin film structure for field effect passivation of a crystalline silicon cell and PECVD (plasma enhanced chemical vapor deposition) equipment, and relates to the technical field of production of crystalline silicon photovoltaic cells, the polycrystalline silicon (Poly-Si) thin film structure comprises two low-concentration doped regions and two high-concentration doped regions, and the low-concentration doped regions and the high-concentration doped regions are stacked layer by layer. The low-concentration doped region and the high-concentration doped region are stacked layer by layer, free carriers in the high-concentration doped region are diffused to the low-concentration doped region, fixed ions with charges are left, the high-concentration doped region becomes a high net charge region, the low-concentration doped region is high in crystallinity and carrier mobility, impurity atom diffusion is inhibited, and the performance of the device is improved. By arranging the high net charge region, the enhanced field effect passivation effect is realized, so that the efficiency of the crystalline silicon photovoltaic cell is improved.

Description

Technical Field

[0001] The invention relates to the technical field of crystalline silicon photovoltaic cell production, in particular to a novel polycrystalline silicon thin film structure and PECVD equipment for field effect passivation of crystalline silicon cells. Background Art

[0002] Tunneling oxide passivation contact (TOPCon) crystalline silicon photovoltaic cells have occupied a major share of the photovoltaic market, and back-contact crystalline silicon photovoltaic cells based on TOPCon technology are also the mainstream research and development direction. The core of TOPCon technology is that silicon oxide is bonded to the surface of the silicon wafer, and then the net charge in the silicon oxide and doped polysilicon attracts free carriers of opposite signs, which is called field effect passivation. The necessary method to enhance TOPCon technology is to increase the net charge concentration in the doped polysilicon. In terms of flexible design of polysilicon film doping structure, the PECVD route has advantages over LPCVD. The doping structure refers to the structure in which the electrical properties of semiconductor materials are changed by intentionally introducing impurity atoms (called dopants). PECVD technology can adjust the amount of dopants in real time during the deposition of polysilicon films, which means that PECVD technology can deposit a new type of polysilicon (Poly-Si) structure with periodic increase and decrease of doping concentration, thereby creating a Poly-Si layer with unique structural characteristics.

[0003] The patent publication number of the existing patent application is: CN111575680B, and the publication date is May 3, 2022. The name of the patent is "A plasma chemical vapor deposition device". Since there are multiple electrode areas with different wear rates on the lower electrode, this patent divides the insulating layer of the lower electrode into multiple insulating areas. The multiple insulating areas correspond to the multiple electrode areas with different wear rates and the insulation properties of the multiple insulating areas are different. That is, insulating areas with corresponding insulation properties are set according to the wear rates of the multiple electrode areas to minimize the difference in wear degree of the multiple electrode areas of the lower electrode, thereby improving the wear consistency of the lower electrode and avoiding the occurrence of spots and other defects caused by excessive local wear. At the same time, it can also effectively extend the service life of the lower electrode and avoid the cost increase caused by frequent replacement of the lower electrode.

[0004] The above application has shortcomings. In traditional crystalline silicon photovoltaic cells, due to the limitations of the doping process, a gradient distribution of carrier concentration is often formed inside the cell. This uneven distribution will lead to an increase in the recombination loss of carriers during the transmission process, thereby reducing the photoelectric conversion efficiency of the cell. At the same time, when using the equipment, in order to ensure the stability of the wafer process results, the tray needs to rotate at high speed through the support shaft to homogenize the airflow field, and at the same time use the heating element to heat the tray. However, due to the presence of the support shaft, the center of the tray will cause uneven heating, and the temperature of the center point will be lower than other parts. At this time, it is generally achieved by setting multiple layers of heating elements in the inner circle to increase the temperature of the support shaft, thereby indirectly increasing the temperature of the center of the tray. However, this method will cause the temperature of the tray above the inner circle heating element to be too high, and the overall temperature cannot be uniformed. Summary of the invention

[0005] The purpose of the present invention is to provide a novel polycrystalline silicon thin film structure and PECVD equipment for field effect passivation of crystalline silicon cells to solve the deficiencies in the above-mentioned prior art.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The invention discloses a novel polysilicon film structure for field effect passivation of a crystalline silicon cell. The polysilicon (Poly-Si) film structure comprises two low-concentration doping regions and two high-concentration doping regions.

[0008] Preferably, the low-concentration doping region and the high-concentration doping region are stacked layer by layer and prepared by a plasma enhanced chemical vapor deposition (PECVD) method, comprising the following steps:

[0009] S1, placing the processed silicon wafer in the reaction chamber 1, and introducing boron or phosphorus dopant and reaction gas through the gas inlet pipe 8;

[0010] S2, forming plasma through high-frequency electric field activation, causing chemical reaction between dopant and reaction gas, controlling the flow rate and partial pressure of dopant during deposition, completing low-high-low-high change cycle, and forming polysilicon film with periodic gradient of doping concentration;

[0011] S3. Annealing the deposited doped polysilicon film.

[0012] Preferably, the free carriers in the high-concentration doping region will diffuse to the low-concentration doping region, leaving charged fixed ions, making the high-concentration doping region a high net charge region, and the low-concentration doping region has high crystallinity, high carrier mobility, and inhibits the diffusion of impurity atoms.

[0013] Preferably, when the deposited doped polysilicon film is annealed, a method of gradually increasing the temperature and then gradually decreasing the temperature is adopted, and an inert gas is introduced as a protective gas.

[0014] A PECVD device for preparing the above-mentioned novel polycrystalline silicon thin film structure for field effect passivation of crystalline silicon cells includes a reaction chamber and a sleeve inserted at the bottom of the reaction chamber, a rotating column is installed in the sleeve, a lower electrode plate is installed on the top of the rotating column, a shielding cover covering the lower electrode plate is installed on the top of the sleeve, a plurality of annular heating elements centered on the rotating column are installed below the shielding cover, and a suppression ring is installed between the sleeve and the rotating column. The interior of the sleeve is divided into a heat storage chamber and a heat dissipation chamber for storing coolant by the suppression ring, a turbulent opening and closing piece matched with the suppression ring is rotatably installed in the heat storage chamber, and while the shielding cover disperses the heat of the annular heating element, the rotating column drives the turbulent opening and closing piece to rotate, so that the coolant in the heat storage chamber and the heat dissipation chamber are intermittently mixed.

[0015] Preferably, an upper electrode plate is installed above the lower electrode plate inside the reaction chamber, an air inlet pipe connected to the outside of the reaction chamber is fixedly connected to the top of the upper electrode plate, and a spray plate is embedded at the bottom of the upper electrode plate.

[0016] Preferably, a guide ring is installed at the exhaust end of the air intake pipe, an annular groove is formed between the guide ring and the air intake pipe, and a circle of inclined air discharge holes connected to the annular groove is provided at the bottom of the air intake pipe.

[0017] Preferably, the spoiler opening and closing component includes a cover ring rotatably connected to the inner wall of the heat storage chamber, the cover ring is provided with an upper through hole, the suppression ring is provided with a lower through hole corresponding to the upper through hole, and a plurality of spoiler paddles are distributed in a ring on the top of the cover ring.

[0018] Preferably, a reflective plate is installed outside the sleeve, the reflective plate is located below the annular heating element, and the diameter of the reflective plate is larger than the outer diameter of any of the annular heating elements. A plurality of heat-conducting fins are distributed in an annular shape on the outer wall of the sleeve, and the upper and lower ends of the heat-conducting fins are respectively in contact with the shielding cover and the reflective plate.

[0019] Preferably, a plug rod is fixedly connected to the bottom of the lower pole plate, a docking joint for inserting the plug rod is fixedly connected to the top of the rotating column, a push plate is fixedly connected to the outer side wall of the docking joint, and the push plate is in abutment with the spoiler paddle.

[0020] Preferably, a heat distribution net is placed inside the shielding cover, and a gap is reserved between the heat distribution net and the lower electrode plate.

[0021] In the above technical solution, free carriers in the high-concentration doping area will diffuse to the low-concentration doping area, leaving fixed ions with charge, making the high-concentration doping area a high net charge area. Through the high net charge area, an enhanced field effect passivation effect is achieved, thereby improving the efficiency of the crystalline silicon photovoltaic cell. The low-concentration doping area has high crystallinity, high carrier mobility, and inhibits the diffusion of impurity atoms.

[0022] A shielding cover is provided to disperse the heat of the annular heating element, thereby achieving uniform heating of the lower electrode plate and the substrate above it, and improving the uniformity of the deposition layer. At the same time, when the rotating column drives the lower electrode plate to rotate and homogenize the air flow field, the turbulent opening and closing piece in the heat storage chamber is driven to rotate together, so that the coolant in the heat storage chamber and the heat dissipation chamber are intermittently mixed, which not only avoids the heat loss in the heat storage chamber too fast, but also uses the heat storage chamber to heat the end of the rotating column to achieve the increase of the center temperature of the upper electrode plate, and prevents the temperature difference between the edge and the center of the tray on the upper plate from being too large. The turbulent opening and closing piece can also be used to regularly exchange the coolant in the heat storage chamber and the heat dissipation chamber, which promotes the mixing and flow of the coolant, thereby ensuring that the temperature of the rotating column itself will not continue to rise after absorbing heat, avoiding excessive heating of the lower electrode plate above the rotating column, ensuring the uniformity of the overall temperature above the lower plate, and avoiding the problem of uneven tray temperature caused by setting multiple layers of heating elements in the inner circle in the traditional method, thereby ensuring the stability of the deposition process results.

[0023] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

[0024] This application document provides an overview of various implementations or examples of the technology described in the present disclosure, and is not a comprehensive disclosure of the entire scope or all features of the disclosed technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0026] Figure 1 Schematic diagram of the new PolySi structure deposited by PECVD before annealing;

[0027] Figure 2 Schematic diagram of the new PolySi structure deposited by PECVD after annealing;

[0028] Figure 3 It is a schematic diagram of the overall structure of a PECVD device of the present invention;

[0029] Figure 4 It is an overall cross-sectional view of a PECVD device of the present invention;

[0030] Figure 5 For the present invention Figure 4 A magnified view of the structure at A;

[0031] Figure 6 This is a schematic diagram of the internal structure of a reaction chamber in a PECVD device of the present invention;

[0032] Figure 7 A top view of a shielding cover in a PECVD device of the present invention;

[0033] Figure 8 A partial cross-sectional view of a sleeve in a PECVD device of the present invention;

[0034] Fig. 9 A schematic diagram of the connection between the lower electrode plate and the rotating column in a PECVD device of the present invention;

[0035] Fig.10 A top view of a sleeve in a PECVD device of the present invention;

[0036] Fig.11 A partial cross-sectional view of an air inlet pipe in a PECVD device according to the present invention.

[0037] Description of reference numerals:

[0038] 1. Reaction chamber; 2. Sleeve; 201. Shielding cover; 202. Annular heating element; 203. Heat storage chamber; 204. Heat dissipation chamber; 205. Reflection plate; 206. Heat-conducting fins; 3. Rotating column; 301. Connector; 302. Push plate; 4. Lower plate; 401. Insert rod; 5. Suppression ring; 501. Lower through hole; 6. Disturbing opening and closing piece; 601. Cover ring; 602. Upper through hole; 603. Disturbing paddle; 7. Upper plate; 8. Inlet pipe; 801. Guide ring; 802. Annular groove; 803. Air discharge inclined hole; 9. Spray plate; 10. Heat distribution network. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0040] Example 1: Please refer to Figure 1-2A novel polysilicon thin film structure for field effect passivation of a crystalline silicon cell is provided in an embodiment of the present invention. The polysilicon (PolySi) thin film structure includes two low-concentration doping regions and two high-concentration doping regions.

[0041] In a further embodiment of the present invention, the low-concentration doped region and the high-concentration doped region are stacked layer by layer and prepared by a plasma enhanced chemical vapor deposition (PECVD) method, comprising the following steps:

[0042] S1. Pre-treat the silicon wafer to be deposited to ensure that there are no impurities and oxide residues on the surface, and then generate a silicon oxide film with a thickness of 1 to 2 nanometers on the surface of the silicon wafer;

[0043] S2, placing the pre-treated silicon wafer in the PECVD reaction chamber 1, and introducing phosphorus dopant and reaction gas through the gas inlet pipe 8;

[0044] S3, through the high frequency electric field activation to form plasma, the dopant and the reaction gas to chemically react, in the deposition process, by precisely controlling the dopant gas partial pressure, RF power and deposition time and other parameters, a polysilicon (Poly-Si) film with a periodic gradient of doping concentration is formed, such as Figure 1 As shown;

[0045] S4, annealing the deposited doped polysilicon (Poly-Si) film;

[0046] S5. Phosphorus atoms doped in polysilicon thin film ionize free electrons, and the free electrons in the high-concentration doping area diffuse to the low-concentration doping area, leaving behind positively charged fixed phosphorus ions, making the high-concentration doping area a high net charge area, such as Figure 2 shown.

[0047] Specifically, Figure 1-2 As shown, Figure 1 and 2 The height of the black line in the figure indicates the doping concentration. Figure 2 The plus sign area in the middle indicates a high net charge area. By precisely controlling the reaction conditions to grow a Poly-Si film with a periodic gradient of doping concentration, annealing treatment is performed to improve the crystal quality and activate the dopant, and the diffusion behavior of free electrons under the doping concentration gradient is used to prepare a Poly-Si film with a high net charge concentration for crystalline silicon photovoltaic cells. When a high-concentration doping area is adjacent to a low-concentration doping area, there is a concentration gradient for the free electrons ionized by the doped phosphorus atoms, and the free electrons will spontaneously diffuse from the high-concentration area to the low-concentration area. This diffusion behavior causes a reduction in the free electrons in the high-concentration doping area, which is insufficient to shield the phosphorus ions, and becomes a high net charge area (such as Figure 2As shown), that is, the charge density (or net charge) in this area is relatively high. Field effect passivation refers to the phenomenon of suppressing or weakening certain electrical effects by changing the charge distribution on the semiconductor surface. In the high net charge area, due to the increase in charge density, the electric field on the semiconductor surface is enhanced. This change can more effectively suppress or weaken undesirable electrical effects, such as leakage current, recombination current, etc. Therefore, the high net charge area created by PECVD technology helps to enhance the field effect passivation effect, thereby improving the performance and stability of crystalline silicon photovoltaic cells. Combined with Figure 2 Further description, wherein SiO x Region 1 blocks the diffusion of doped atoms into the single crystal silicon wafer, region 2 has a high doping concentration, and region 3 has a low doping concentration, so the free electrons in region 2 will diffuse into region 3, and the fixed phosphorus ions in region 2 will lose the shielding of free electrons and become a net charge. Region 4 has a high doping concentration and can form an ohmic contact with the metal gate line. Figure 2 Region 2 is the high net charge region, which can enhance the field effect passivation effect. Region 3 is the high crystallinity region, which can achieve low resistivity by lower doping concentration and better block the inward erosion of metal atoms.

[0048] Compared with the prior art, the present invention stacks low-concentration doping regions and high-concentration doping regions layer by layer, allowing free carriers in the high-concentration doping regions to diffuse to the low-concentration doping regions, leaving charged fixed ions, so that the high-concentration doping regions become high net charge regions. Through the high net charge regions provided, enhanced field effect passivation is achieved, thereby improving the efficiency of crystalline silicon photovoltaic cells. The low-concentration doping regions have high crystallinity, high carrier mobility, and inhibit the diffusion of impurity atoms.

[0049] In a further embodiment of the present invention, the free carriers in the high-concentration doping area will diffuse to the low-concentration doping area, leaving charged fixed ions, making the high-concentration doping area a high net charge area. The low-concentration doping area has high crystallinity, high carrier mobility, and inhibits the diffusion of impurity atoms. Specifically, the strong electric field generated by the high net charge area in the phosphorus-doped polysilicon film attracts free electrons and repels free holes, greatly reducing the recombination of free electrons and holes on the surface of the silicon wafer, reducing the recombination current, and thus improving the photoelectric conversion efficiency of the crystalline silicon photovoltaic cell.

[0050] In a further embodiment of the present invention, when the deposited doped PolySi film is annealed, a method of gradually heating up and then gradually cooling down is adopted. By accurately controlling parameters such as the heating rate, annealing temperature, holding time and cooling rate during the annealing process, the annealing effect can be optimized, so that the stress and defects in the doped PolySi film can be more thoroughly eliminated, and the crystallization quality and stability of the film can be improved. Gradually heating up helps the atoms in the film gradually adapt to temperature changes and avoid damage caused by thermal shock, while gradually cooling down helps the atoms in the film gradually recover to a stable lattice structure, thereby further improving the quality of the film.

[0051] In a further embodiment of the present invention, an inert gas is introduced as a protective gas during the annealing process, which can create an oxygen-free and water vapor-free environment, effectively preventing oxidation and hydrolysis of the film at high temperatures, ensuring the positive impact of the annealing process on the quality of the film, and ultimately obtaining a doped PolySi film with more stable performance and higher quality, providing a key film quality guarantee for the manufacture of high-efficiency crystalline silicon photovoltaic cells.

[0052] Example 2: Please refer to Figure 3-11 A PECVD device for preparing a novel polycrystalline silicon thin film structure for field effect passivation of crystalline silicon cells provided in an embodiment of the present invention comprises a reaction chamber 1 and a sleeve 2 which is inserted at the bottom of the reaction chamber 1, a rotating column 3 is installed in the sleeve 2, a lower electrode plate 4 is installed at the top of the rotating column 3, a shielding cover 201 covering the lower electrode plate 4 is installed at the top of the sleeve 2, a plurality of annular heating elements 202 centered on the rotating column 3 are installed below the shielding cover 201, and a suppression ring 5 is installed between the sleeve 2 and the rotating column 3. The interior of the sleeve 2 is divided into a heat storage chamber 203 for storing coolant and a heat dissipation chamber 204 by the suppression ring 5, a turbulent opening and closing member 6 which cooperates with the suppression ring 5 is rotatably installed in the heat storage chamber 203, and while the shielding cover 201 disperses the heat of the annular heating element 202, the rotating column 3 drives the turbulent opening and closing member 6 to rotate, so that the coolant in the heat storage chamber 203 and the heat dissipation chamber 204 are intermittently mixed.

[0053] Specifically, the lower electrode plate 4 is a circular flat plate for placing a tray carrying silicon wafer substrate materials, and is connected to the negative electrode of the power supply through a wire to form an electric field during the plasma vapor deposition process. The shielding cover 201 is an annular structure with a diameter slightly larger than the lower electrode plate 4, and is fixed to the top of the sleeve 2 by bolts or welding to ensure that it stably covers the lower electrode plate 4. The shielding cover 201 is made of a material that is resistant to high temperatures and has good thermal conductivity. The annular heating element 202 is an annular structure composed of a number of resistance wires or electric heating tubes, which are evenly distributed below the shielding cover 201. The heat generated by the annular heating element 202 is effectively dispersed through the dispersing effect of the shielding cover 201, and the heat is prevented from directly It is transferred to the lower electrode plate 4 to uniformly heat the gas in the reaction chamber 1, providing the required temperature conditions for plasma vapor deposition. The heat storage chamber 203 and the heat dissipation chamber 204 are respectively located on the upper and lower sides of the suppression ring 5, and are both surrounded by the inner wall of the sleeve 2 and the outer wall of the rotating column 3. The heat storage chamber 203 is filled with a high-heat-capacity coolant for storing the heat generated by the annular heating element 202. The heat dissipation chamber 204 is also filled with a coolant, but it is mainly used to extract the excess heat in the heat storage chamber 203 for external cooling. In the present invention, during the plasma vapor deposition process, the heat generated by the annular heating element 202 is dispersed by the shielding cover 201 to uniformly heat the gas in the reaction chamber 1. At the same time, when the rotating column 3 drives the rotating column 3 to drive the lower pole plate 4 to rotate to homogenize the airflow field, it will also drive the turbulence opening and closing member 6 to rotate, so that the coolant in the heat storage chamber 203 and the heat dissipation chamber 204 are intermittently mixed, thereby achieving uniform distribution and effective dissipation of heat. This design not only improves the thermal efficiency of the equipment, but also ensures the stability and reliability of the crystalline silicon photovoltaic cell production process.

[0054] Compared with the prior art, the embodiment of the present invention disperses the heat of the annular heating element 202 by setting a shielding cover 201, thereby achieving uniform heating of the lower electrode plate 4 and the substrate above it, and improving the uniformity of the deposition layer. At the same time, when the rotating column 3 drives the lower electrode plate 4 to rotate and homogenize the airflow field, it drives the turbulent opening and closing member 6 in the heat storage chamber 203 to rotate together, so that the coolant in the heat storage chamber 203 and the heat dissipation chamber 204 are intermittently mixed, which not only avoids the heat loss in the heat storage chamber 203 too fast, but also uses the heat storage chamber 203 to heat the end of the rotating column 3 to achieve the heat dissipation in the upper electrode plate 7. The core temperature is increased to prevent the temperature difference between the edge and the center of the tray on the upper plate from being too large, and the coolant in the heat storage chamber 203 and the heat dissipation chamber 204 can be regularly exchanged through the spoiler opening and closing part 6, which promotes the mixing and flow of the coolant, thereby ensuring that the temperature of the rotating column 3 itself will not continue to rise after absorbing heat, avoiding excessive heating of the lower plate 4 above the rotating column 3, ensuring the uniformity of the overall temperature above the lower plate, and avoiding the problem of uneven tray temperature caused by setting multiple layers of heating elements in the inner circle in the traditional method, thereby ensuring the stability of the chip process results.

[0055] In a further embodiment of the present invention, an upper electrode plate 7 is installed above the lower electrode plate 4 inside the reaction chamber 1, and an air inlet pipe 8 connected to the outside of the reaction chamber 1 is fixedly connected to the top of the upper electrode plate 7, and a spray plate 9 is embedded at the bottom of the upper electrode plate 7. Specifically, during the vapor deposition process, the upper electrode plate 7 and the lower electrode plate 4 are energized by a radio frequency power supply (RF power supply), and the high-frequency alternating current generated by the radio frequency power supply forms an electric field between the upper electrode plate 7 and the lower electrode plate 4, thereby exciting the raw material gas to generate plasma. This electric field effect not only ionizes and excites the raw material gas molecules, but also promotes the progress of chemical reactions and the deposition of thin films. At the same time, the air inlet pipe 8 on the upper electrode plate 7 is connected to the outside of the reaction chamber 1. , which is used to introduce process gas into the reaction chamber. The design of the air inlet pipe 8 takes into account the uniform distribution and flow control of the gas to ensure that a stable and uniform gas atmosphere can be formed in the reaction chamber during the plasma vapor deposition process. A spray plate 9 is embedded at the bottom of the upper electrode plate 7. The spray plate 9 is composed of a plurality of tiny nozzles, which are evenly distributed at the bottom of the upper electrode plate 7 to form a spray surface. During the plasma vapor deposition process, after the process gas enters the reaction chamber 1 through the air inlet pipe 8, it will be evenly sprayed through the nozzles of the spray plate 9. This design not only improves the utilization rate of the process gas, but also enables a more uniform and stable plasma environment to be formed in the reaction chamber.

[0056] In a further embodiment of the present invention, a guide ring 801 is installed at the exhaust end of the air inlet pipe 8, and an annular groove 802 is formed between the guide ring 801 and the air inlet pipe 8. A circle of inclined gas discharge holes 803 connected to the annular groove 802 is opened at the bottom of the air inlet pipe 8. Specifically, during the plasma vapor deposition process, the raw gas enters the reaction chamber 1 through the air inlet pipe 8. When reaching the exhaust end of the air inlet pipe 8, part of the gas will be guided by the guide ring 801 and distributed in the annular groove 802. Subsequently, these process gases enter the reaction chamber 1 in a more uniform and dispersed manner through a circle of inclined gas discharge holes 803. Under the spraying action of the spray plate 9, these process gases can accurately cover the silicon wafer substrate material on the lower electrode 4 and react with the substrate material.

[0057] In a further embodiment of the present invention, the spoiler opening and closing member 6 includes a cover ring 601 rotatably connected to the inner wall of the heat storage chamber 203, the inner wall of the heat storage chamber 203 is provided with a limiting ring groove matching the edge of the cover ring 601, an upper through hole 602 is provided on the cover ring 601, and a lower through hole 501 corresponding to the upper through hole 602 is provided on the suppression ring 5. A plurality of spoiler paddles 603 are distributed in an annular shape on the top of the cover ring 601, and the bottom of the cover ring 601 is in close contact with the suppression ring 5. Specifically, the upper through hole 602 on the cover ring 601 corresponds to the lower through hole 501 on the suppression ring 5. When the rotating column 3 drives the cover ring 601 to rotate to a certain specific position, the upper through hole 602 and the lower through hole 501 will completely overlap, thereby allowing The coolant in the heat storage chamber 203 and the coolant in the heat dissipation chamber 204 are mixed to reduce the continuously increasing heat in the heat storage chamber 203. When the cover ring 601 rotates to other positions, the upper through hole 602 and the lower through hole 501 will be partially or completely staggered, thereby reducing or completely avoiding the coolant in the heat storage chamber 203 from flowing into the heat dissipation chamber 204, so as to ensure that the heat storage chamber 203 can continuously absorb the heat generated by the annular heating element 202, and transfer enough heat to the central area of ​​the lower plate 4 through the rotating column 3, thereby ensuring the consistency of its overall temperature. At the same time, the coolant in the heat dissipation chamber 204 can also play a cooling role at an appropriate time to avoid continuous heating of the rotating column 3.

[0058] In a further embodiment of the present invention, a reflective plate 205 is installed outside the sleeve 2, and the reflective plate 205 is located below the annular heating element 202, and the diameter of the reflective plate 205 is larger than the outer diameter of any of the annular heating elements 202. A plurality of heat-conducting fins 206 are distributed in an annular manner on the outer wall of the sleeve 2, and the upper and lower ends of the heat-conducting fins 206 are in contact with the shielding cover 201 and the reflective plate 205, respectively. Specifically, these annular heating elements 202 are arranged in a concentric circle manner and are connected to an external power source through wires, respectively. The reflective plate 205 installed on the outer wall can ensure that all generated heat can be effectively reflected and concentrated on the shielding cover 201. In addition, the multiple heat-conducting fins 206 distributed in an annular shape on the outer wall of the sleeve 2 extend in the vertical direction, and the upper part thereof contacts the bottom of the shielding cover 201, and the lower part fits tightly with the top of the reflective plate 205, forming an efficient heat conduction path, which can more comprehensively absorb excess heat and enter the heat storage chamber 203, thereby further ensuring that the heat in the middle of the lower plate 4 is within the corresponding value.

[0059] In a further embodiment of the present invention, a plug rod 401 is fixedly connected to the bottom of the lower pole plate 4, and a docking joint 301 for inserting the plug rod 401 is fixedly connected to the top of the rotating column 3, the docking joint 301 and the rotating column 3 rotate coaxially, and a push plate 302 is fixedly connected to the outer wall of the docking joint 301, and the push plate 302 abuts and cooperates with the spoiler paddle 603. Specifically, when the docking joint 301 at the top of the rotating column 3 abuts against the top of the inner wall of the sleeve 2, the push plate 302 on the docking joint 301 is higher than the spoiler paddle 603. At this time, when the rotating column 3 drives the upper pole plate 7 to rotate, the entire spoiler opening and closing member 6 will not be driven by it. That is to say, if the heat storage chamber 203 is not connected with the heat dissipation chamber 204 at this time, the heat storage chamber 203 can continue to absorb heat in the chamber. After the center temperature of the upper pole plate 7 is sufficient, the rotating column 3 is lowered to drive the spoiler opening and closing member 6 during rotation, so that the heat in the heat storage chamber 203 is maintained within a stable range.

[0060] In a further embodiment of the present invention, a heat distribution net 10 is placed inside the shielding cover 201, and a gap is reserved between the heat distribution net 10 and the lower pole plate 4. Specifically, the heat distribution net 10 is made of a material that is resistant to high temperatures and has good thermal conductivity, and its shape and size can fit tightly against the inner wall of the shielding cover 201. At the same time, a certain gap is reserved between the heat distribution net 10 and the lower pole plate 4. The gap is to ensure that the heat distribution net 10 can evenly distribute heat and avoid excessive concentration of heat on the lower pole plate 4, thereby improving the uniformity and efficiency of heating. In addition, the introduction of the heat distribution net 10 also increases the path and area of ​​heat transfer, so that the heat generated by the annular heating element 202 can be transferred to the air inside the shielding cover 201 and the lower pole plate 4 more quickly. At the same time, since a gap is reserved between the heat distribution net 10 and the lower pole plate 4, this gap can also serve as a buffer zone to reduce the direct impact of heat on the lower pole plate 4, thereby extending the service life of the lower pole plate 4.

[0061] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A novel polycrystalline silicon thin film structure for field effect passivation of crystalline silicon cells, characterized in that: The polysilicon film structure includes two low-concentration doping regions and two high-concentration doping regions.

2. The novel polycrystalline silicon thin film structure for field effect passivation of a crystalline silicon cell according to claim 1, characterized in that: The low-concentration doping region and the high-concentration doping region are stacked layer by layer and prepared by a plasma enhanced chemical vapor deposition method, including the following steps: S1, placing the processed silicon wafer in a reaction chamber (1), and introducing a boron or phosphorus dopant and a reaction gas through an air inlet pipe (8); S2, through the high frequency electric field activation to form plasma, so that the dopant and the reaction gas chemical reaction, During the deposition process, the flow rate and partial pressure of the dopant are controlled to complete the low-high-low-high change cycle. forming a polysilicon film having a periodic gradient of doping concentration; S3. Annealing the deposited doped polysilicon film.

3. The novel polycrystalline silicon thin film structure for field effect passivation of a crystalline silicon cell according to claim 2, characterized in that: The free carriers in the high-concentration doping area will diffuse to the low-concentration doping area, leaving charged fixed ions, making the high-concentration doping area a high net charge area. The low-concentration doping area has high crystallinity, high carrier mobility, and inhibits the diffusion of impurity atoms.

4. The novel polycrystalline silicon thin film structure for field effect passivation of a crystalline silicon cell according to claim 2, characterized in that: When the deposited doped polysilicon film is annealed, a method of gradually increasing the temperature and then gradually decreasing the temperature is adopted, and an inert gas is introduced as a protective gas.

5. A PECVD device for preparing a novel polycrystalline silicon thin film structure for field effect passivation of a crystalline silicon cell as claimed in any one of claims 1 to 4, comprising a reaction chamber (1), characterized in that: Also includes: A sleeve (2) is inserted into the bottom of the reaction chamber (1), a rotating column (3) is installed in the sleeve (2), a lower electrode plate (4) is installed at the top of the rotating column (3), a shielding cover (201) covering the lower electrode plate (4) is installed at the top of the sleeve (2), and a plurality of annular heating elements (202) centered on the rotating column (3) are installed below the shielding cover (201); A flow suppression ring (5) is installed between the sleeve (2) and the rotating column (3); the interior of the sleeve (2) is divided into a heat storage chamber (203) for storing coolant and a heat dissipation chamber (204) by the flow suppression ring (5); a flow turbulence opening and closing member (6) that cooperates with the flow suppression ring (5) is rotatably installed in the heat storage chamber (203); While the shielding cover (201) disperses the heat of the annular heating element (202), the rotating column (3) drives the turbulent opening and closing member (6) to rotate, so that the coolant in the heat storage chamber (203) and the heat dissipation chamber (204) are intermittently mixed.

6. A PECVD device according to claim 5, characterized in that: An upper electrode plate (7) is installed above the lower electrode plate (4) inside the reaction chamber (1); an air intake pipe (8) communicating with the outside of the reaction chamber (1) is fixedly connected to the top of the upper electrode plate (7); and a spray plate (9) is embedded at the bottom of the upper electrode plate (7).

7. A PECVD device according to claim 6, characterized in that: A guide ring (801) is installed at the exhaust end of the air intake pipe (8), an annular groove (802) is formed between the guide ring (801) and the air intake pipe (8), and a circle of inclined air discharge holes (803) connected to the annular groove (802) is formed at the bottom of the air intake pipe (8).

8. A PECVD device according to claim 5, characterized in that: The spoiler opening and closing member (6) comprises a cover ring (601) rotatably connected to the inner wall of the heat storage chamber (203), an upper through hole (602) is provided on the cover ring (601), a lower through hole (501) corresponding to the upper through hole (602) is provided on the flow suppression ring (5), and a plurality of spoiler paddles (603) are distributed in an annular shape on the top of the cover ring (601).

9. A PECVD device according to claim 5, characterized in that: A reflective disk (205) is installed outside the sleeve (2), the reflective disk (205) is located below the annular heating elements (202), and the diameter of the reflective disk (205) is greater than the outer diameter of any one of the annular heating elements (202). A plurality of heat-conducting fins (206) are distributed in an annular pattern on the outer wall of the sleeve (2), and the upper and lower ends of the heat-conducting fins (206) are in contact with the shielding cover (201) and the reflective disk (205), respectively.

10. A PECVD device according to claim 8, characterized in that: The bottom of the lower pole plate (4) is fixedly connected with an insertion rod (401), the top of the rotating column (3) is fixedly connected with a docking joint (301) for inserting the insertion rod (401), the outer side wall of the docking joint (301) is fixedly connected with a push plate (302), and the push plate (302) is in abutment with the spoiler paddle (603).

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