LPCVD furnace body structure and silicon layer preparation method

Abstract

The invention relates to the technical field of photovoltaics, in particular to an LPCVD furnace body structure and a silicon layer preparation method, and aims to reduce the temperature of a boron doping process, shorten the duration of the boron doping process and reduce the production cost of a photovoltaic cell. The LPCVD furnace body structure comprises a furnace tube and a plasma generating device, the furnace tube is provided with a process chamber and a gas inlet, the process chamber is configured to contain a sheet carrying boat carrying sheets, the gas inlet is communicated with the process chamber, and the gas inlet is configured to allow process gas to enter; the plasma generating device comprises a discharge structure, the discharge structure is configured to ionize the process gas to generate plasma diffused into the furnace tube, and the plasma is used for deposition on the surface of the sheet. According to the method, a certain boron content is kept in the silicon layer, and higher source introduction amount, longer source introduction time and higher reaction temperature are not needed in the subsequent boron diffusion process, so that the production cost of the photovoltaic cell is reduced.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular to an LPCVD furnace structure and a method for preparing silicon layers. Background Technology

[0002] Semiconductor and photovoltaic materials are widely used in industries such as electronics and new energy. These materials typically require chemical processing before application to products. Chemical vapor deposition (CVD) is one such chemical processing method and is now widely used in semiconductor and photovoltaic material processing. Common equipment used for CVD includes LPCVD (Low Pressure Chemical Vapor Deposition), PECVD (Plasma Enhanced Chemical Vapor Deposition), and APCVD (Atmosphere Pressure Chemical Vapor Deposition). Besides CVD, diffusion processes are also widely used in semiconductor and photovoltaic material processing, such as phosphorus diffusion and boron diffusion, both of which utilize gas diffusion to process semiconductor or photovoltaic materials. Currently, in the P-junction fabrication process for photovoltaic cells, the high temperature and long processing time of boron doping result in high production costs. Summary of the Invention

[0003] In view of this, embodiments of this application provide an LPCVD furnace structure and a phosphorus diffusion furnace to reduce the temperature and shorten the time of the boron doping process, thereby reducing the production cost of photovoltaic cells.

[0004] In a first aspect, one embodiment of this application provides an LPCVD furnace structure configured to perform surface deposition diffusion on sheets. The LPCVD furnace structure includes: a furnace tube having a process chamber and an inlet, the process chamber being configured to accommodate a sheet carrier boat carrying the sheets, the inlet being connected to the process chamber and configured to allow process gas to enter; and a plasma generating device including a discharge structure configured to ionize the process gas to generate plasma that diffuses into the furnace tube, the plasma being used for deposition on the sheet surface.

[0005] In conjunction with the first aspect, in some implementations of the first aspect, at least a portion of the discharge structure is disposed inside the process chamber to ionize the process gas inside the process chamber.

[0006] In conjunction with the first aspect, in some implementations of the first aspect, the discharge structure includes a discharge tube, the interior of which is provided with a coolant; or, the discharge structure includes a first electrode and a second electrode, the first electrode and the second electrode being arranged at a distance to form an electrode gap between the first electrode and the second electrode.

[0007] In conjunction with the first aspect, in some implementations of the first aspect, the interior of the process chamber is provided with a placement area, which is configured to place a wafer carrier boat, and the discharge structure is located outside the placement area along the radial direction of the furnace tube.

[0008] In conjunction with the first aspect, in some implementations of the first aspect, there are multiple discharge structures, which are evenly arranged at intervals along the circumference of the furnace tube.

[0009] In conjunction with the first aspect, in some implementations of the first aspect, the discharge structure extends along the length of the furnace tube, and along the length of the furnace tube, the two ends of the discharge structure pass through both ends of the furnace tube.

[0010] In conjunction with the first aspect, in some implementations of the first aspect, at least a portion of the discharge structure is disposed outside the process chamber and connected to the gas inlet to ionize the process gas before it enters the process chamber.

[0011] In conjunction with the first aspect, in some implementations of the first aspect, the LPCVD furnace structure further includes a heating device disposed on the outer periphery of the furnace tube; the heating device is used to heat the plasma and / or the wafer carrier in the process chamber.

[0012] In conjunction with the first aspect, in some implementations of the first aspect, the LPCVD furnace structure further includes a controller electrically connected to the heating device and the plasma generator, the controller being configured to have a plasma deposition mode; in the plasma deposition mode, the controller controls the heating device and the plasma generator to be turned on simultaneously so that plasma is deposited on the surface of the heated sheet.

[0013] Secondly, one embodiment of this application provides a method for preparing a silicon layer, applied to the LPCVD furnace structure of any of the above claims. The method includes: step S1, placing a silicon wafer into a process chamber and evacuating the process chamber; step S2, raising the temperature inside the process chamber to the oxidation temperature and introducing oxygen into the process chamber to oxidize the silicon wafer and form a tunneling oxide layer; step S3, evacuating the process chamber; step S4, setting the temperature inside the process chamber to a first preset temperature and introducing silane into the process chamber to deposit the silicon wafer and form a first silicon film layer; step S5, evacuating the process chamber; step S6, setting the temperature inside the process chamber to a second preset temperature and introducing oxygen, a boron-carrying source gas, and an inert gas into the process chamber to perform a first boron diffusion deposition to form a first boron-doped silicon layer, wherein the boron-carrying source gas is ionized using a plasma generator to generate plasma; wherein both the first preset temperature and the second preset temperature are less than or equal to 800°C.

[0014] In conjunction with the second aspect, in some implementations of the second aspect, the silicon layer preparation method further includes: step S7, evacuating the process chamber; step S8, setting the temperature inside the process chamber to a third preset temperature, introducing silane into the process chamber to deposit silicon wafers and form a second silicon film layer; step S9, evacuating the process chamber; step S10, setting the temperature inside the process chamber to a fourth preset temperature, introducing oxygen, a boron-carrying source gas, and an inert gas into the process chamber to perform a second boron diffusion deposition and form a second boron-doped silicon layer, wherein the boron-carrying source gas is ionized using a plasma generator to generate plasma; wherein the third preset temperature and the fourth preset temperature are both less than or equal to 800°C.

[0015] In conjunction with the second aspect, in steps S8 and S10, the pressure inside the process chamber is 100 mTorr to 400 mTorr; and / or, the third preset temperature is 400℃ to 700℃, and the fourth preset temperature is 550℃ to 650℃.

[0016] In conjunction with the second aspect, in some implementations of the second aspect, step S2 includes: step S21, maintaining a vacuum in the process chamber, raising the temperature inside the process chamber to a first oxidation temperature, and introducing oxygen into the process chamber to oxidize the silicon wafer and form a first oxide layer; step S22, after oxygen has been introduced into the process chamber until the process chamber is at atmospheric pressure, controlling the process chamber at a second oxidation temperature to oxidize the silicon wafer and form a second oxide layer; step S23, controlling the process chamber at a third oxidation temperature, and introducing a mixed oxidizing gas into the process chamber to oxidize the silicon wafer and form a third oxide layer. Wherein, a plasma generator is used to ionize the mixed oxidizing gas to generate plasma, and the tunneling oxide layer includes a first oxide layer, a second oxide layer, and a third oxide layer, wherein the first oxidation temperature, the second oxidation temperature, and the third oxidation temperature are all less than or equal to 800°C.

[0017] In conjunction with the second aspect, in some implementations of the second aspect, in steps S2, S4 and S6, the pressure inside the process chamber is 100 mTor ~ 400 mTor; and / or, the first preset temperature is 400℃ ~ 700℃, and the second preset temperature is 550℃ ~ 650℃.

[0018] In the LPCVD furnace structure of this application embodiment, during surface deposition diffusion of the wafer, the wafer is first placed in the process chamber of the furnace tube; then, oxygen is introduced into the process chamber to form a tunneling oxide layer on the wafer surface; subsequently, silane is introduced into the process chamber to form a silicon layer on the wafer surface; finally, a process gas including a boron-carrying gas is introduced into the process chamber, wherein the boron-carrying gas is ionized by the discharge structure of the plasma generator to form plasma, and the boron-carrying gas diffuses and deposits on the wafer surface to form a first boron-doped silicon layer. This ensures that the silicon layer retains a certain boron content, eliminating the need for higher source flux, longer source flux time, and higher reaction temperature in subsequent boron diffusion processes, thereby reducing the production cost of photovoltaic cells. Attached Figure Description

[0019] The above and other objects, features, and advantages of this application will become more apparent from the more detailed description of the embodiments of this application in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same components or steps.

[0020] Figure 1 The diagram shown is a structural schematic of an LPCVD furnace body provided in an embodiment of this application.

[0021] Figure 2 As shown Figure 1A magnified view of a portion of point A in the middle.

[0022] Figure 3 As shown Figure 1 A magnified view of a section at point B.

[0023] Figure 4 The image shown is a side view of an LPCVD furnace structure provided in an embodiment of this application.

[0024] Figure 5 The image shown is a plasma effect diagram during silicon layer preparation using an LPCVD furnace structure provided in an embodiment of this application.

[0025] Figure 6 The diagram shown is a connection diagram of the plasma generator, heating device and controller of an LPCVD furnace structure provided in an embodiment of this application.

[0026] Figure 7 The image shown is a side view of an LPCVD furnace structure provided in another embodiment of this application.

[0027] Figure 8 The image shown is an effect diagram of plasma during silicon layer preparation using an LPCVD furnace structure provided in another embodiment of this application.

[0028] Figure 9 The image shown is a side view of an LPCVD furnace structure provided in another embodiment of this application.

[0029] Figure 10 The image shown is an effect diagram of plasma during silicon layer preparation using an LPCVD furnace structure provided in another embodiment of this application.

[0030] Figure 11 The image shown is a side view of the LPCVD furnace structure provided in another embodiment of this application.

[0031] Figure 12 The image shown is an illustration of the plasma effect during silicon layer fabrication using an LPCVD furnace structure provided in another embodiment of this application.

[0032] Figure 13 The diagram shown is a flowchart of a silicon layer fabrication method provided in an embodiment of this application.

[0033] Figure 14 The diagram shown is a flowchart of a silicon layer fabrication method provided in another embodiment of this application.

[0034] Figure 15 The diagram shown is a flowchart of a silicon layer fabrication method provided in another embodiment of this application.

[0035] Figure label: 10. LPCVD furnace structure; 1. Furnace tube; 11. Process chamber; 111. Placement area; 12. Furnace opening; 13. Furnace tail; 2. Plasma generator; 21. Discharge structure; 211. Discharge tube; 22. Radio frequency power supply; 3. Sheets; 4. Exhaust pipe; 5. Heating device; 6. Controller. Detailed Implementation

[0036] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] In related technologies, the traditional method for fabricating P-type junctions in photovoltaic cells involves growing a tunneling oxide layer (SiO2) and a poly layer using LPCVD (Liquid-Pulse Chemical Vapor Deposition), followed by boron diffusion doping using BCl3 gas within a high-temperature tubular apparatus. To achieve higher doping concentrations, the deposition temperature for the poly layer during LPCVD furnace fabrication is typically between 550°C and 580°C, aiming to enhance boron penetration in subsequent processes. The boron doping process involves placing the sample to be doped in a high-temperature tubular apparatus, introducing BCl3 gas at a relatively high temperature (e.g., 800°C to 900°C) for long-duration surface boron source deposition, followed by deep diffusion doping within the silicon layer at an even higher temperature (e.g., 900°C to 980°C) over a prolonged period. The high temperature and long processing time of the boron doping process result in high production costs.

[0038] To address the aforementioned issues, this application incorporates a plasma generator into the LPCVD furnace structure. This plasma generator ionizes the process gas, allowing the silicon layer to retain a certain boron content through plasma discharge diffusion during deposition. This eliminates the need for higher flux levels, longer flux times, and higher reaction temperatures in the subsequent boron diffusion process, thereby reducing the production cost of photovoltaic cells. In this configuration, the silicon layer is a mixture of amorphous and polycrystalline silicon. However, the subsequent boron diffusion process converts the amorphous silicon into polycrystalline silicon, resulting in finer grains in the polycrystalline silicon produced within the LPCVD furnace and improved conductivity of the silicon layer.

[0039] Figure 1 The diagram shown is a structural schematic of the LPCVD furnace body structure 10 provided in an embodiment of this application. Figure 2 As shown Figure 1 A magnified view of a portion of point A in the middle. Figure 3 As shown Figure 1 A magnified view of a section at point B. Figure 4 The image shown is a side view of an LPCVD furnace structure 10 provided in an embodiment of this application. Figure 5 The image shown is a plasma effect diagram of the LPCVD furnace structure 10 provided in an embodiment of this application during silicon layer preparation.

[0040] like Figures 1 to 5 As shown, the LPCVD furnace structure 10 provided in this application is configured to perform surface deposition diffusion on sheet 3. The LPCVD furnace structure 10 includes a furnace tube 1 and a plasma generator 2. The furnace tube 1 has a process chamber 11 and an inlet. The process chamber 11 is configured to accommodate a wafer carrier boat, which carries the sheet 3. The inlet communicates with the process chamber 11 and is configured to allow process gas to enter. The plasma generator 2 includes a discharge structure 21, which is configured to ionize the process gas to generate plasma. Plasma diffuses into the furnace tube and enters the interior of the wafer carrier boat, where it is deposited on the surface of the sheet 3 within the boat.

[0041] In this embodiment of the LPCVD furnace structure 10, when performing surface deposition diffusion on the sheet 3, the carrier boat carrying the sheet 3 is first placed in the process chamber 11 of the furnace tube 1; then, oxygen is introduced into the process chamber 11 to form a tunneling oxide layer on the surface of the sheet 3; subsequently, silane is introduced into the process chamber 11 to form a silicon layer on the surface of the sheet 3; finally, a process gas including a boron source gas is introduced into the process chamber 11, wherein the boron source gas is ionized by the discharge structure 21 of the plasma generator 2 to form plasma, and the boron source gas diffuses and deposits on the surface of the sheet 3 to form a first boron-doped silicon layer. This ensures that the silicon layer retains a certain boron content, eliminating the need for higher source flow rates, longer source flow times, and higher reaction temperatures in subsequent boron diffusion processes, thereby reducing the production cost of photovoltaic cells.

[0042] For example, the sheet 3 can be a silicon sheet 3; the boron source gas can be BCl3 gas.

[0043] For example, the air intake method of furnace tube 1 is the same as that of related technologies. The air inlet can be located at furnace opening 12, i.e., air intake is achieved through furnace opening 12. Alternatively, a spray air intake pipe connected to the air inlet can be installed to supply process gas to the process chamber 11. When air intake is achieved through furnace opening 12, the flow direction of the process gas is as follows: Figure 1 The arrow m in the diagram is shown.

[0044] Among them, and / or, In some embodiments, at least a portion of the discharge structure 21 is disposed inside the process chamber 11 to ionize the process gas inside the process chamber 11.

[0045] Wherein, at least a portion of the discharge structure 21 is disposed inside the process chamber 11, which can be understood as: a portion of the discharge structure 21 is disposed inside the process chamber 11, and another portion of the discharge structure 21 is disposed outside the process chamber 11; or, the discharge structure 21 is disposed entirely inside the process chamber 11.

[0046] When at least a portion of the discharge structure 21 is disposed inside the process chamber 11, the process gas enters the process chamber 11 through the inlet, and the discharge structure 21 disposed inside the process chamber 11 ionizes the process gas inside the process chamber 11 to generate plasma.

[0047] By discharging at least a portion of the discharge structure 21 inside the process chamber 11, the process gas entering the process chamber 11 can be ionized using the discharge structure 21 to form plasma, which is then deposited on the surface of the sheet 3.

[0048] In some embodiments, at least a portion of the discharge structure 21 is disposed outside the process chamber 11 and connected to the air inlet to ionize the process gas before it enters the process chamber 11.

[0049] Wherein, at least a portion of the discharge structure 21 is disposed outside the process chamber 11, which can be understood as: a portion of the discharge structure 21 is disposed outside the process chamber 11, and another portion of the discharge structure 21 is disposed inside the process chamber 11; or, the discharge structure 21 is disposed entirely outside the process chamber 11.

[0050] When at least a portion of the discharge structure 21 is disposed outside the process chamber 11, the discharge structure 21 disposed outside the process chamber 11 ionizes the process gas before it enters the process chamber 11 to generate plasma, which then enters the interior of the process chamber 11 through the gas inlet.

[0051] By distributing at least a portion of the discharge structure 21 outside the process chamber 11, the process gas before entering the process chamber 11 can be ionized using the discharge structure 21 to generate plasma. The generated plasma then enters the process chamber 11 and is deposited on the surface of the sheet 3.

[0052] Of course, a portion of the discharge structure 21 can be placed outside the process chamber 11, and the other portion of the discharge structure 21 can be placed inside the process chamber 11, so that the process gas is ionized once before entering the process chamber 11 and ionized again after entering the process chamber 11, which is beneficial to increase the plasma concentration and improve the utilization rate of the process gas.

[0053] Figure 6 The diagram shown is a connection diagram of the plasma generator, heating device and controller of an LPCVD furnace structure provided in an embodiment of this application.

[0054] In some embodiments, such as Figure 6 As shown, the LPCVD furnace structure also includes a heating device 5, which is disposed on the outer periphery of the furnace tube 1. Optionally, the heating device 5 is a heating wire, which is arranged in a loop on the outer periphery of the furnace tube 1. When the heating wire is energized, the furnace tube 1 can be heated. The heating device 5 can also be an infrared heater, which can directly heat the furnace tube 1 and the wafer carrier boat inside the furnace tube 1.

[0055] By incorporating heating device 5, the temperature of the process gas within furnace tube 11 and the temperature of the substrate carrier boat and the sheet 3 within it can be increased. When plasma deposition is not required, heating device 5 heats the process gas and sheet, enabling the process gas to undergo pyrolysis deposition, thereby improving the uniformity of deposition on the surface of sheet 3. When plasma deposition is required, heating device 5 heats the substrate carrier boat and sheet 3, causing the temperature of sheet 3 in each region to rise uniformly, improving the adhesion between the plasma and sheet 3, and enhancing the stability of plasma deposition. Furthermore, heating device 5 can also heat the plasma, increasing the plasma collision intensity on the surface of sheet 3 and increasing the deposition rate. Compared to pyrolysis deposition, plasma deposition has a lower temperature, offering advantages such as reduced fragmentation rate and lower production costs.

[0056] In some embodiments, such as Figure 7 As shown, the LPCVD furnace structure also includes a controller 6. The controller 6 is electrically connected to the heating device 5 and the plasma generator 2, and the controller 6 is configured to have a plasma deposition mode. In the plasma deposition mode, the controller 6 controls the heating device 5 and the plasma generator 2 to be turned on simultaneously, so that plasma is deposited on the surface of the heated sheet 3.

[0057] The controller 6 includes a temperature control module, which controls the heating device 5 to ensure that each area of ​​the heating device 5 can heat the furnace tube 1 separately along the furnace body's extension direction. During the process, the furnace tube 1 needs to maintain a high temperature in the middle region and compensate for heat loss due to the reaction; therefore, it needs to be at a higher temperature in the middle and lower temperatures at both ends, ensuring that the substrate boats and the sheets 3 within them are at approximately the same temperature along the furnace tube 1's extension direction. By controlling the heating device 5 and the plasma generator 2 to be turned on simultaneously using the controller 6 in plasma deposition mode, the plasma can more easily adhere to the heated sheet 3, enhancing the adhesion between the deposited film and the sheet 3.

[0058] In some embodiments, the discharge structure 21 includes a discharge tube 211, and the interior of the discharge tube 211 is provided with a coolant.

[0059] For example, the discharge tube 211 is a copper tube. The coolant can be cooling water. The flow direction of the cooling water can be as follows: Figure 1 As shown by arrow k in the diagram.

[0060] The discharge structure 21 is an ICP (inductively coupled plasma) structure. When the plasma is used, the discharge tube 211 is electrically connected to the radio frequency power supply 22, so that radio frequency current is generated in the discharge tube 211. The radio frequency current ionizes the process gas to form plasma.

[0061] By designating the discharge structure 21 as a discharge tube 211, the plasma concentration ionized by the discharge structure 21 is higher, which is beneficial for increasing the concentration of the boron source within the silicon layer. This allows for increased doping concentration of the P-type junction in the subsequent boron diffusion process, thereby improving the conversion efficiency of the photovoltaic cell. Furthermore, the discharge tube 211 can stabilize the process under lower pressure, ensuring reliable operation even when the discharge structure 21 is located inside the process chamber 11, which is beneficial for improving the quality of the silicon layer. The partial silicon layer formed by plasma deposition contains both polycrystalline and amorphous silicon. However, in the subsequent boron diffusion process, all or most of the amorphous silicon is converted into polycrystalline silicon.

[0062] By placing a coolant inside the discharge tube 211, the coolant can be used to cool and dissipate heat from the discharge tube 211, ensuring the stability of the discharge tube 211 during operation and improving the quality of the silicon layer.

[0063] In some embodiments, the discharge structure 21 further includes a protective shell that surrounds the discharge tube 211.

[0064] For example, the protective shell is made of silicon carbide or the like.

[0065] By wrapping the discharge tube 211 with a protective shell, the ionized substances emitted by the discharge tube 211 itself can be prevented from contacting the sheet 3, thus avoiding affecting the quality of the silicon layer on the sheet 3. In addition, when the discharge tube 211 is placed inside the process chamber 11, it can prevent crystalline silicon and other materials inside the process chamber 11 from adhering to the discharge tube 211, thereby affecting the conductivity and service life of the discharge tube 211.

[0066] In other embodiments, the discharge structure 21 includes a first electrode and a second electrode, which are arranged at a distance to form an electrode gap between the first electrode and the second electrode.

[0067] For example, both the first and second electrodes are electrode plates, and the discharge structure 21 is a CCP (capacitively coupled plasma) structure. When the plasma generator 2 is in use, the first and second electrodes are electrically connected to the radio frequency power supply 22, thereby generating a radio frequency voltage between the first and second electrodes, thus establishing a radio frequency electric field. The process gas is ionized in the radio frequency electric field to form plasma.

[0068] By setting the discharge structure 21 to include a first electrode and a second electrode, with an electrode gap formed between the first electrode and the second electrode, the discharge structure 21 is simple in structure and low in cost, thereby further reducing the production cost of photovoltaic cells.

[0069] For example, the number of the first electrode and the second electrode is one; or, the discharge structure 21 includes multiple electrode groups, each electrode group including a first electrode and a second electrode, the first electrode and the second electrode in the same electrode group are arranged opposite to each other, and the multiple electrode groups are arranged at intervals along the length direction of the furnace tube 1.

[0070] In some embodiments, the interior of the process chamber 11 is provided with a placement area 111, which is configured to place a sheet carrier boat. The sheet carrier boat carries the sheet 3, and along the radial direction of the furnace tube 1, the discharge structure 21 is disposed outside the placement area 111.

[0071] In the plane perpendicular to the centerline of the furnace tube 1, the direction closer to the centerline of the furnace tube 1 is inward, and the direction farther from the centerline of the furnace tube 1 is outward. The discharge structure 21 is located outside the placement area 111, which means that in the plane perpendicular to the centerline of the furnace tube 1, the discharge structure 21 is located further away from the centerline of the furnace tube 1 relative to the placement area 111.

[0072] By placing the discharge structure 21 on the outside of the placement area 111, interference between the discharge structure 21 and the sheet 3 can be avoided, preventing the discharge structure 21 from moving when the sheet 3 enters or exits the process chamber 11, thus improving the ease of use of the LPCVD furnace structure 10. Furthermore, placing the discharge structure 21 on the outside of the placement area 111 ensures that the plasma ionized by the discharge structure 21 is closer to the sheet 3, which is beneficial for improving the utilization rate of the boron source gas and further reducing the production cost of photovoltaic cells.

[0073] In other embodiments, the LPCVD furnace structure 10 may also include a support boat and a paddle, the support boat being used to support the sheet 3, the paddle being used to push the support boat into or out of the process chamber 11, and the discharge structure 21 being connected to the paddle.

[0074] By connecting the discharge structure 21 to the propeller, the discharge structure 21 can enter and exit the process chamber 11 together with the propeller, and the discharge structure 21 can be fixed on the propeller.

[0075] In some embodiments, such as Figure 1 As shown, the discharge structure 21 extends along the length of the furnace tube 1, and both ends of the discharge structure 21 penetrate both ends of the furnace tube 1 along the length of the furnace tube 1.

[0076] For example, the furnace tube 1 has a furnace opening 12 and a furnace tail 13. The furnace opening 12 is provided with a furnace opening 12 flange, and the furnace tail 13 is provided with a furnace tail 13 flange. The two ends of the discharge structure 21 are respectively fixed on the furnace opening 12 flange and the furnace tail 13 flange.

[0077] By passing the two ends of the discharge structure 21 through the two ends of the furnace tube 1, it is not only convenient to install and fix the discharge structure 21, but also to increase the plasma concentration ionized by the discharge structure 21 in the furnace tube 1. This is beneficial to increase the concentration of boron source in the silicon layer, so as to increase the doping concentration of the P-type junction in the subsequent collision diffusion process and improve the conversion efficiency of photovoltaic cells.

[0078] In other embodiments, the discharge structure 21 may also be integrally disposed inside the process chamber 11, and a support structure may be provided inside the process chamber 11 to fix the discharge structure 21. The support structure may have a slot, into which the discharge structure 21 engages.

[0079] Figure 7 The image shown is a side view of an LPCVD furnace structure 10 provided in another embodiment of this application. Figure 8 The image shown is a plasma effect diagram during silicon layer preparation using the LPCVD furnace structure 10 provided in another embodiment of this application. Figure 9 The image shown is a side view of the LPCVD furnace structure 10 provided in another embodiment of this application. Figure 10The image shown is an effect diagram of plasma during silicon layer preparation using the LPCVD furnace structure 10 provided in another embodiment of this application. Figure 11 The image shown is a side view of the LPCVD furnace structure 10 provided in another embodiment of this application. Figure 12 The image shown is an illustration of the plasma effect during silicon layer fabrication using the LPCVD furnace structure 10 provided in another embodiment of this application. Figure 5 , Figure 8 , Figure 10 and Figure 12 The gray area in the diagram represents the plasma ionized by the discharge structure 21. The darker the gray area, the higher the plasma concentration.

[0080] In some embodiments, such as Figures 7 to 12 As shown, there are multiple discharge structures 21, which are evenly arranged at intervals along the circumference of the furnace tube 1.

[0081] For example, such as Figures 7 to 10 As shown, there are two discharge structures 21, which are arranged on both radial sides of the furnace tube 1. Figure 11 and Figure 12 As shown, there are four discharge structures 21, which are evenly arranged along the circumference of the furnace tube 1.

[0082] By setting the number of discharge structures 21 to multiple, the plasma concentration in the process chamber 11 is higher, which is beneficial to increasing the concentration of boron source in the silicon layer. This allows for an increase in the doping concentration of the P-type junction in the subsequent impact diffusion process, thereby improving the conversion efficiency of the photovoltaic cell. In addition, the multiple discharge structures 21 are evenly arranged at circumferential intervals along the furnace tube 1, which can increase the plasma concentration in the process chamber 11 and improve the quality consistency of the sheet 3.

[0083] In other embodiments, such as Figures 1 to 5 As shown, the number of discharge structures 21 can also be set to only one.

[0084] Figure 13 The diagram shown is a flowchart of a silicon layer fabrication method provided in an embodiment of this application.

[0085] like Figure 13 As shown, the silicon layer fabrication method provided in this application, applied to the LPCVD furnace structure 10 of any of the above embodiments, includes the following: Step S1: Place the silicon wafer 3 into the process chamber 11 and evacuate the process chamber 11. Step S2: The temperature inside the process chamber 11 is raised to the oxidation temperature, and oxygen is introduced into the process chamber 11 to oxidize the silicon wafer 3 and form a tunnel oxide layer. Step S3: Evacuate the process chamber 11; Step S4: The temperature inside the process chamber 11 is the first preset temperature. Silane is introduced into the process chamber 11 to deposit silicon wafer 3 and form the first silicon film layer. Step S5: Evacuate the process chamber 11; Step S6: The temperature inside the process chamber 11 is the second preset temperature. Oxygen, boron source gas and inert gas are introduced into the process chamber 11 to perform the first boron diffusion deposition and form the first boron-doped silicon layer. Plasma generator 2 is used to ionize the boron source gas to generate plasma. The first preset temperature and the second preset temperature are both less than or equal to 800℃.

[0086] Exemplarily, the furnace tube 1 also includes a heating device 5 configured to heat the process chamber 11, such that the temperature within the process chamber 11 can be a first preset temperature and a second preset temperature. The process chamber 11 can be provided with multiple temperature zones, arranged sequentially along the direction from the furnace opening 12 to the furnace tail 13. For example, the process chamber 11 may have six temperature zones, arranged sequentially along the direction from the furnace opening 12 to the furnace tail 13. The controller 6 controls the heating device 5 located in the middle temperature zone to have a higher temperature, and the heating devices located in the two end temperature zones to have a lower temperature. This ensures that the temperature of the sheets 3 in each sheet carrier boat is approximately the same.

[0087] For example, the furnace tube 1 includes a tail gas pipe 4 disposed at the furnace tail 13. The tail gas pipe 4 is connected to a vacuum pump, which evacuates the process chamber 11. When the vacuum pump evacuates the process chamber 11, the gas flow direction within the process chamber 11 is as follows: Figure 1 As indicated by arrow n in the diagram.

[0088] The silicon layer fabrication method of this application involves sequentially forming a tunneling oxide layer and a first silicon film layer. Then, a plasma generator 2 is used to ionize a boron-carrying source gas to generate plasma. Using oxygen, the boron-carrying source gas, and an inert gas, a first boron diffusion deposition is performed to form a first boron-doped silicon layer. This ensures that the silicon layer retains a certain boron content, eliminating the need for higher source flux, longer source flux time, and higher reaction temperatures in subsequent boron diffusion processes, thereby reducing the production cost of photovoltaic cells.

[0089] In addition, both the first preset temperature and the second preset temperature are less than or equal to 800℃, which ensures that the process temperature of the entire process will not be too high, reducing damage to the LPCVD furnace body structure 10 and helping to extend the service life of the LPCVD furnace body structure 10.

[0090] For example, in step S2, the process chamber 11 is first heated using a heating structure to raise the temperature inside the process chamber 11 to the oxidation temperature, and then the temperature of the process chamber 11 is maintained at a certain value.

[0091] For example, the inert gas can be nitrogen.

[0092] In some embodiments, the pressure inside the process chamber 11 in steps S2, S4 and S6 is 100 mTor to 400 mTor.

[0093] For example, in step S2, oxygen is introduced into the process chamber 11 to bring the pressure inside the process chamber 11 to atmospheric pressure, and then a tunnel oxide layer is grown on the silicon wafer under atmospheric pressure.

[0094] By setting the pressure inside the process chamber 11 to 100 mTor ~ 400 mTor in steps S2, S4, and S6, the quality of the first boron-doped silicon layer can be effectively guaranteed, thus ensuring the conversion efficiency of the photovoltaic cell. The first boron-doped silicon layer is mainly composed of amorphous silicon, with some polycrystalline silicon also present.

[0095] In some embodiments, the first preset temperature is 400℃~700℃, and the second preset temperature is 550℃~650℃.

[0096] For example, the first preset temperature is 500℃~600℃, and the second preset temperature is 550℃~650℃.

[0097] By setting the first preset temperature to 400℃~700℃ and the second preset temperature to 550℃~650℃, the quality of the first silicon film layer is ensured while the overall process temperature remains low, reducing damage to the LPCVD furnace structure 10 and further extending its service life. The first silicon film layer is mainly composed of polycrystalline silicon, with some amorphous silicon also present.

[0098] Figure 14 The diagram shown is a flowchart of a silicon layer fabrication method provided in another embodiment of this application.

[0099] In some embodiments, the silicon layer fabrication method further includes: Step S7: Evacuate the process chamber 11; In step S8, the temperature inside the process chamber 11 is set to a third preset temperature. Silane is introduced into the process chamber 11 to deposit silicon wafer 3, forming a second silicon film layer. The second silicon film layer is mainly composed of polycrystalline silicon, but also contains some amorphous silicon.

[0100] Step S9: Evacuate the process chamber 11; In step S10, the temperature inside the process chamber 11 is set to the fourth preset temperature. Oxygen, a boron-carrying source gas, and an inert gas are introduced into the process chamber 11 to perform a second boron diffusion deposition, forming a second boron-doped silicon layer. Plasma generator 2 is used to ionize the boron-carrying source gas to generate plasma. The second boron-doped silicon layer is primarily composed of amorphous silicon, but also contains some polycrystalline silicon.

[0101] The third and fourth preset temperatures are both less than or equal to 800℃.

[0102] The first boron-doped silicon layer and the second boron-doped silicon layer are both boron-doped silicon layers of silicon wafer 3.

[0103] Steps S7 to S10 form a second boron-doped silicon layer, which helps to increase the depth and concentration of the boron source within the layer. This allows for further reduction of the source flux and shortening of the flux time in subsequent boron diffusion processes, thereby further lowering the production cost of photovoltaic cells. Furthermore, it increases the carrier concentration in the boron-doped silicon layer, improving the conversion efficiency of the photovoltaic cells.

[0104] In addition, the third and fourth preset temperatures are both less than or equal to 800℃, which ensures that the process temperature of the entire process will not be too high, reducing damage to the LPCVD furnace body structure 10 and helping to extend the service life of the LPCVD furnace body structure 10.

[0105] In some embodiments, in steps S8 and S10, the pressure inside the process chamber 11 is 100 mTor ~ 400 mTor.

[0106] By setting the pressure in the process chamber 11 to 100 mTor ~ 400 mTor in steps S8 and S10, the quality of the first boron-doped silicon layer can be effectively guaranteed, thus ensuring the conversion efficiency of the photovoltaic cell.

[0107] In some embodiments, the third preset temperature is 400℃~700℃, and the fourth preset temperature is 550℃~650℃.

[0108] For example, the third preset temperature is 500℃~600℃, and the fourth preset temperature is 550℃~650℃.

[0109] By setting the third preset temperature to 500℃~600℃ and the fourth preset temperature to 550℃~650℃, the quality of the second silicon film layer is ensured while the process temperature of the entire process is kept low, reducing damage to the LPCVD furnace structure 10 and further extending the service life of the LPCVD furnace structure 10.

[0110] Figure 15The diagram shown is a flowchart of a silicon layer fabrication method provided in another embodiment of this application.

[0111] In some embodiments, step S2 includes: Step S21: Maintain the vacuum in the process chamber 11, raise the temperature inside the process chamber 11 to the first oxidation temperature, and introduce oxygen into the process chamber 11 to oxidize the silicon wafer 3 and form the first oxide layer. Step S22: After oxygen is introduced into the process chamber 11 until the process chamber 11 is at atmospheric pressure, the process chamber 11 is controlled at the second oxidation temperature to oxidize the silicon wafer 3 and form the second oxide layer; here, atmospheric pressure refers to atmospheric pressure. In reality, due to actual equipment limitations or process requirements, the pressure may fluctuate by 70 torr above or below atmospheric pressure.

[0112] Step S23: Control the process chamber 11 at the third oxidation temperature, maintain the temperature inside the process chamber 11, and introduce a mixed oxidizing gas into the process chamber 11 to oxidize the silicon wafer 3 to form a third oxide layer. Oxygen is ionized using a plasma generator 2 to generate plasma. The tunneling oxide layer includes a first oxide layer, a second oxide layer, and a third oxide layer. Optionally, the mixed oxidizing gas may include a mixture of nitrous oxide and oxygen.

[0113] The first oxidation temperature, the second oxidation temperature, and the third oxidation temperature are all less than or equal to 800℃.

[0114] By performing steps S21 and S22, the tunneling oxide layer achieves good density. By performing step S23, a thicker tunneling oxide layer can be formed in a shorter time. Thus, while forming the tunneling oxide layer in a short time, the thickness and density of the tunneling oxide layer are ensured, improving the quality of the tunneling oxide layer. This, in turn, improves the quality of the doped silicon layer and ensures the conversion efficiency of the photovoltaic cell.

[0115] In some embodiments, the silicon layer fabrication method further includes: Step S11: Evacuate the process chamber 11; Step S12: Purge and cool the process chamber 11; Step S13: Break the vacuum in process chamber 11; Step S14: Remove the silicon wafer 3 from the process chamber 11.

[0116] Steps S2 to S11 above do not require cooling the process chamber. That is, in step S2, the process chamber is heated to the post-oxidation temperature, and in steps S3 to S11, the process chamber is kept at the temperature, or the process chamber is heated slightly to increase the temperature.

[0117] In summary, the process flow for doped silicon layers can be as follows: boat loading → vacuuming → heating → isothermal control → oxidation → oxidation → discharge oxidation → vacuuming → leak detection → isothermal control → pre-ventilation → thermal diffusion → vacuuming → discharge diffusion → vacuuming → thermal diffusion → vacuuming → purging → vacuum breaking → boat unloading.

[0118] The oxidation process involves introducing oxygen into the process chamber to form a tunneling oxide layer; the discharge oxidation process involves introducing oxygen into the process chamber and using a plasma generator to ionize the oxygen to form plasma, thereby forming a tunneling oxide layer; the pre-gas process involves introducing silane into the process chamber; the thermal diffusion process involves introducing silane into the process chamber to form a silicon layer; and the discharge diffusion process involves introducing oxygen into the process chamber, carrying boron source gas and inert gas, to form a doped silicon layer.

[0119] The method for preparing a boron-doped silicon layer according to this application embodiment adds ionization diffusion to the thermal diffusion process when forming the tunneling oxide layer, which can increase the thickness of the tunneling oxide layer. By using a plasma generator 2 to ionize the boron-carrying gas to generate plasma, a boron-doped silicon layer is formed during the LPCVD process, achieving integrated film formation and doping in the LPCVD process. Boron source diffusion is completed during film formation, increasing the boron carrier concentration within the silicon layer by 10%. 19 cm −3 ~10 20 cm −3 In the post-boron diffusion process, not only can the source quantity, time, and process temperature required for boron diffusion be reduced, thus lowering the production cost of photovoltaic cells, but the doping concentration of the P-type junction can also be increased, thereby improving the conversion efficiency of photovoltaic cells. Specifically, in the post-boron diffusion process, the process temperature can be lowered to below 900℃, for example, to 870℃, thereby reducing the lattice damage caused by high temperatures to the boron diffusion process, as well as damage to the furnace tube 1 and the carrier (e.g., boat), thus reducing the production cost of photovoltaic cells.

[0120] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not restrict the application from being implemented using the specific details described above.

[0121] The block diagrams of devices, apparatuses, devices, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “featuring,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0122] It should also be noted that in the apparatus, equipment, and methods of this application, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of this application.

[0123] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this application. Therefore, this application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0124] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. An LPCVD furnace body structure, characterized in that, The LPCVD furnace structure is configured to perform surface deposition diffusion on sheets and includes: A furnace tube has a process chamber and an air inlet, the process chamber being configured to accommodate a sheet carrier boat carrying sheets, the air inlet being connected to the process chamber and configured to allow process gas to enter; A plasma generating apparatus includes a discharge structure configured to ionize the process gas to generate plasma that diffuses into the furnace tube, the plasma being used for deposition on the surface of the sheet.

2. The LPCVD furnace structure according to claim 1, characterized in that, At least a portion of the discharge structure is disposed inside the process chamber to ionize the process gas inside the process chamber.

3. The LPCVD furnace structure according to claim 2, characterized in that, The discharge structure includes a discharge tube, and the discharge tube is filled with coolant. or, The discharge structure includes a first electrode and a second electrode, which are arranged at a distance to form an electrode gap between them.

4. The LPCVD furnace structure according to claim 2, characterized in that, The process chamber has a placement area inside, which is configured to place the wafer carrier boat. Along the radial direction of the furnace tube, the discharge structure is located outside the placement area.

5. The LPCVD furnace structure according to claim 4, characterized in that, The number of discharge structures is multiple, and the multiple discharge structures are evenly arranged at intervals along the circumference of the furnace tube.

6. The LPCVD furnace structure according to claim 2, characterized in that, The discharge structure extends along the length of the furnace tube, and both ends of the discharge structure penetrate both ends of the furnace tube along the length of the furnace tube.

7. The LPCVD furnace structure according to claim 1, characterized in that, At least a portion of the discharge structure is disposed outside the process chamber and connected to the air inlet to ionize the process gas before it enters the process chamber.

8. The LPCVD furnace structure according to any one of claims 1 to 7, characterized in that, The LPCVD furnace body structure also includes a heating device, which is disposed on the outer periphery of the furnace tube; The heating device is used to heat the plasma and / or the wafer carrier boat in the process chamber.

9. The LPCVD furnace structure according to any one of claims 8, characterized in that, The LPCVD furnace structure also includes a controller, which is electrically connected to the heating device and the plasma generating device, and the controller is configured to have a plasma deposition mode; In the plasma deposition mode, the controller controls the heating device and the plasma generator to be turned on simultaneously, so that the plasma is deposited on the surface of the heated sheet.

10. A method for preparing a silicon layer, characterized in that, Applied to the LPCVD furnace structure as described in any one of claims 1-9, the silicon layer fabrication method comprises: Step S1: Place the silicon wafer into the process chamber and evacuate the process chamber; Step S2: The temperature inside the process chamber is raised to the oxidation temperature, and oxygen is introduced into the process chamber to oxidize the silicon wafer and form a tunnel oxide layer. Step S3: Evacuate the process chamber; Step S4: The temperature inside the process chamber is a first preset temperature. Silane is introduced into the process chamber to deposit the silicon wafer and form a first silicon film layer. Step S5: Evacuate the process chamber; Step S6: The temperature inside the process chamber is a second preset temperature. Oxygen, boron-carrying source gas and inert gas are introduced into the process chamber to perform the first boron diffusion deposition to form a first boron-doped silicon layer. In this process, the boron-carrying source gas is ionized using a plasma generator to generate plasma. Wherein, both the first preset temperature and the second preset temperature are less than or equal to 800℃.

11. The method for preparing a silicon layer according to claim 10, characterized in that, Also includes: Step S7: Evacuate the process chamber; Step S8: The temperature inside the process chamber is a third preset temperature. Silane is introduced into the process chamber to deposit the silicon wafer and form a second silicon film layer. Step S9: Evacuate the process chamber; Step S10: The temperature inside the process chamber is a fourth preset temperature. Oxygen, boron-carrying source gas and inert gas are introduced into the process chamber to perform a second boron diffusion deposition to form a second boron-doped silicon layer. In this process, the boron-carrying source gas is ionized using a plasma generator to generate plasma. The third preset temperature and the fourth preset temperature are both less than or equal to 800°C.

12. The method for preparing a silicon layer according to claim 11, characterized in that, In steps S8 and S10, the pressure within the process chamber is 100 mTorr to 400 mTorr; and / or, The third preset temperature is 400℃~700℃, and the fourth preset temperature is 550℃~650℃.

13. The method for preparing a silicon layer according to claim 10, characterized in that, Step S2 includes: Step S21: Maintain the vacuum in the process chamber, raise the temperature inside the process chamber to the first oxidation temperature, and introduce oxygen into the process chamber to oxidize the silicon wafer and form a first oxide layer; Step S22: After oxygen is introduced into the process chamber until the process chamber is at atmospheric pressure, the process chamber is controlled at the second oxidation temperature to oxidize the silicon wafer and form a second oxide layer. Step S23: Control the process chamber at the third oxidation temperature, and introduce a mixed oxidation gas into the process chamber to oxidize the silicon wafer and form a third oxide layer. The mixed oxidation gas is ionized by a plasma generator to generate plasma. The tunneling oxide layer includes the first oxide layer, the second oxide layer and the third oxide layer. The first oxidation temperature, the second oxidation temperature, and the third oxidation temperature are all less than or equal to 800°C.

14. The method for preparing a silicon layer according to any one of claims 10-13, characterized in that, In steps S4 and S6, the pressure within the process chamber is 100 mTorr to 400 mTorr; and / or, The first preset temperature is 400℃~700℃, and the second preset temperature is 550℃~650℃.

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