Control method of coating equipment, method for preparing film layer, solar cell

Abstract

The application discloses a control method of a tubular PECVD film coating device, a solar cell film layer preparation method and a solar cell. The control method of the tubular PECVD film coating device comprises the following steps: during the common operation of a first radio frequency power supply and a second radio frequency power supply, the first radio frequency power supply and the second radio frequency power supply work in a pulse mode, a part of rising edges of the first radio frequency power supply does not coincide with at least a part of rising edges of the second radio frequency power supply, the transient electric field between two graphite boats can be avoided from being too large, and the process gas can be prevented from being ionized to form powder in the too large transient electric field, on the basis, the pulse width of the first radio frequency power supply and the pulse width of the second radio frequency power supply are partially overlapped, and the synergistic effect is enhanced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a control method based on a tubular PECVD coating equipment, a method for preparing solar cell film layers, and a solar cell. Background Technology

[0002] In tubular PECVD coating equipment, in order to improve production efficiency, two or more graphite boats are placed horizontally inside the furnace tube. Silicon wafers are loaded into the graphite boats. Taking two graphite boats as an example, the graphite boat closer to the furnace door is called the front boat, and the graphite boat closer to the furnace tail is called the rear boat.

[0003] During the operation of the tubular PECVD coating equipment, the radio frequency power supply operates in pulse mode to ionize the process gas. After being ionized, the process gas is deposited on the surface of the silicon wafer to form a thin film.

[0004] At the rising edge, the instantaneous output power of the RF power supply is often much higher than the set value. When the rising edges of the two RF power supplies coincide, the transient power superposition effect is significantly enhanced, resulting in a strong local electric field at the junction of the front and rear boats. Under the action of this strong electric field, an unexpected gas phase reaction occurs in the junction area of ​​the front and rear boats, generating dust that falls onto the graphite boat and silicon wafer. If all rising edges coincide, after several pulse cycles, the amount of dust on the graphite boat and silicon wafer exceeds the expectation, resulting in dust pollution. When all pulse widths of the two RF power supplies do not overlap at all, a synergistic effect cannot be formed. Summary of the Invention

[0005] Firstly, the purpose of this invention is to provide a control method based on tubular PECVD coating equipment to reduce dust generation and ensure production efficiency.

[0006] A control method based on a tubular PECVD coating equipment, wherein the tubular PECVD coating equipment includes a furnace tube, a first radio frequency (RF) power supply, and a second RF power supply. The furnace tube has a first end and a second end at its two ends along its axial direction. A first graphite boat and a second graphite boat are sequentially and spaced apart inside the furnace tube along the direction from the first end to the second end. Both the first and second graphite boats are loaded with silicon substrates. The first graphite boat corresponds to the first RF power supply, and the second graphite boat corresponds to the second RF power supply. The control method includes:

[0007] During joint operation, both the first and second RF power supplies operate in pulse mode. At least a portion of the rising edges of the first RF power supply do not coincide with a portion of the rising edges of the second RF power supply, and the pulse widths of the first and second RF power supplies partially overlap.

[0008] As an optional technical solution, when a portion of the rising edge of the first RF power supply does not coincide with a portion of the rising edge of the second RF power supply, and another portion of the rising edge of the first RF power supply coincides with another portion of the rising edge of the second RF power supply, the number of times the rising edges coincide is less than the number of times the rising edges do not coincide.

[0009] As an optional technical solution, the process gas inlet is located at the first end, and the process gas outlet is located at the second end;

[0010] The operating power of the first RF power supply is greater than the operating power of the second RF power supply.

[0011] As an optional technical solution, the operating power of the first RF power supply is set to 5000-20000W, and the operating power of the second RF power supply is set to 3000-18000W.

[0012] As an optional technical solution, the pulse width of the second radio frequency power supply is greater than the pulse width of the first radio frequency power supply.

[0013] As an optional technical solution, the duty cycle of the second RF power supply is greater than the duty cycle of the first RF power supply.

[0014] As an optional technical solution, the pulse width of the first RF power supply is 10-60ms, and the pulse width of the second RF power supply is 20-100ms.

[0015] As an optional technical solution, in a single pulse cycle, the pulse off duration of the first RF power supply is 300-1500ms, and the pulse off duration of the second RF power supply is 300-2000ms.

[0016] As an optional technical solution, the process gas inlet is located between the first graphite boat and the second graphite boat, and both the first end and the second end are provided with process gas outlets. Alternatively, the process gas inlet is located on one side of the first graphite boat and the second graphite boat, and the process gas outlet is located on the other side of the first graphite boat and the second graphite boat.

[0017] The rising edge of the first RF power supply and the rising edge of the second RF power supply do not coincide. The operating power of the first RF power supply and the operating power of the second RF power supply are equal. The pulse width of the first RF power supply and the pulse width of the second RF power supply are equal. The duty cycle of the first RF power supply and the duty cycle of the second RF power supply are equal.

[0018] Secondly, another objective of this invention is to propose a method for preparing solar cell film layers, which uses the above-mentioned control method to prepare doped amorphous silicon layers, thereby reducing dust generation and improving production efficiency.

[0019] A method for preparing a solar cell film includes the following steps:

[0020] S10. Load the second graphite boat and the first graphite boat, which are loaded with silicon substrates, into the furnace tube;

[0021] S20. Grow or deposit an interface passivation layer on the silicon substrate;

[0022] S30. A doped amorphous silicon layer is deposited on the interface passivation layer using the control method described above.

[0023] Thirdly, another objective of this invention is to propose a solar cell in which a doped amorphous silicon layer is prepared using the above-mentioned solar cell film preparation method, thereby reducing pollution and ensuring product quality.

[0024] A solar cell includes a silicon substrate, and along the thickness direction of the silicon substrate, an interface passivation layer and a doped polycrystalline silicon layer are sequentially disposed on the surface of the silicon substrate. The doped polycrystalline silicon layer is formed by annealing a doped amorphous silicon layer. The solar cell is characterized in that the doped amorphous silicon layer is prepared by the solar cell film preparation method described above.

[0025] Beneficial effects

[0026] During the joint operation of the first and second RF power supplies, both operate in pulse mode. A portion of the rising edge of the first RF power supply does not coincide with a portion of the rising edge of the second RF power supply, which can avoid excessive transient electric field between the two graphite boats and prevent the process gas from ionizing and forming powder under excessive transient electric field. On this basis, another portion of the rising edge of the first RF power supply coincides with another portion of the rising edge of the second RF power supply, and the pulse width of the first RF power supply partially overlaps with the pulse width of the second RF power supply, enhancing the synergistic effect. Attached Figure Description

[0027] The present invention will now be described in detail with reference to the embodiments and accompanying drawings, wherein:

[0028] Figure 1 This is a schematic diagram of a tubular PECVD coating equipment.

[0029] Figure 2 This is another structural schematic diagram of a tubular PECVD coating equipment.

[0030] Figure 3 This is another structural schematic diagram of a tubular PECVD coating equipment.

[0031] Figure 4This is a schematic diagram showing that all rising edges of RF power supply one and RF power supply two coincide.

[0032] Figure 5 This is a schematic diagram showing that the pulse widths of RF power supply one and RF power supply two are completely non-overlapping.

[0033] Figure 6 This is a pulse diagram of the first and second radio frequency power supplies of the present invention.

[0034] Figure 7 This is a schematic diagram of the structure of a solar cell according to an embodiment of the present invention.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1. Furnace tube; 11. Furnace door; 12. Furnace tail; 2. First RF power supply; 3. Second RF power supply; 4. First graphite boat; 5. Second graphite boat; 6. Process gas inlet; 7. Process gas outlet.

[0037] 10. Back antireflection layer; 20. Doped polysilicon layer; 30. Tunneling oxide layer; 40. Silicon substrate; 50. Emitter; 60. Front passivation layer; 70. Front antireflection layer. Detailed Implementation

[0038] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0039] Therefore, a feature pointed out in this specification is used to describe one feature of one embodiment of the invention, and does not imply that every embodiment of the invention must have the described feature. Furthermore, it should be noted that this specification describes many features. Although certain features may be combined to illustrate possible system designs, these features may also be used in other combinations not explicitly stated. Therefore, unless otherwise stated, the described combinations are not intended to be limiting.

[0040] PECVD (Plasma Enhanced Chemical Vapor Deposition) is a semiconductor manufacturing technology that uses radio frequency (RF) power to excite plasma and achieve thin film deposition at low temperatures. The basic working principle is to create an electric field inside the furnace tube by using RF power, which ionizes the process gas into active particles. The active particles are deposited on the substrate surface and undergo chemical reactions to form a thin film.

[0041] The tubular PECVD coating equipment includes a furnace tube 1, a first radio frequency (RF) power supply 2, and a second RF power supply 3. The furnace tube 1 has a first end and a second end along its axial direction. A first graphite boat 4 and a second graphite boat 5 are sequentially arranged at intervals inside the furnace tube 1, pointing from the first end to the second end. Both the first graphite boat 4 and the second graphite boat 5 are loaded with a silicon substrate 40. The first graphite boat 4 corresponds to the first RF power supply 2, and the second graphite boat 5 corresponds to the second RF power supply 3; that is, plasma is excited by their respective RF power supplies to promote thin film deposition. The first end is one of the furnace door 11 and the furnace tail 12, and the second end is the other of the furnace door 11 and the furnace tail 12.

[0042] The RF power supply is an existing product with continuous wave mode and pulse mode. Continuous wave mode is the basic operating mode, outputting a continuous and constant RF sine wave with continuous and uninterrupted power and a stable waveform. When the built-in pulse modulation or an external pulse module is used, it switches to pulse mode, periodically turning on and off. The waveform has a sine wave in the high-level segment and no waveform in the low-level segment. In the high-level segment of each pulse cycle, there are rising and falling edges, and the high-level segment corresponds to the pulse width. The ratio of the high-level segment to the pulse cycle is the duty cycle. The RF power supply has response delays due to inductors, capacitors, and matching networks, and the edges of the characteristic diagram have slight slopes or rounded corners. Therefore, in actual circuits, the power switching (rising and falling edges) is not absolutely vertical. However, for the sake of drawing convenience, this application idealizes it and forms a vertical mode. In short, after the RF power supply is started, it performs periodic pulse operation with multiple pulse cycles. Each pulse cycle has one rising edge and one falling edge. Therefore, multiple pulse cycles include multiple rising edges and multiple falling edges. The main body of the radio frequency power supply is usually located outside the furnace tube 1, and the electrodes are located inside the furnace tube 1. The electrodes are considered part of the radio frequency power supply. For example, the radio frequency power supply corresponding to the front boat connects the positive and negative terminals to the diagonal positions at both ends of the front boat, and the radio frequency power supply corresponding to the rear boat connects the positive and negative terminals to the same end of the rear boat. The first radio frequency power supply 2 and the second radio frequency power supply 3 referred to in this application can be independent radio frequency power supplies, or one radio frequency power supply can be divided into two radio frequency power supply signals. The first radio frequency power supply 2 and the second radio frequency power supply 3 each represent one radio frequency power supply signal. It is also the prior art for one radio frequency power supply to output two radio frequency power supply signals. The specific principles will not be elaborated in this application.

[0043] like Figure 1As shown, in one embodiment of a tubular PECVD coating equipment, the process gas inlet 6 is located at the furnace door 11, and the process gas outlet 7 is located at the furnace tail 12. A continuously supplied process gas flows from the furnace door 11 to the furnace tail 12. The process gas is ionized and deposited onto the silicon wafers. Therefore, during the flow, the concentration of the process gas gradually decreases along the axial direction of the furnace tube 1. The process gas concentration is higher in the area near the first graphite boat 4 near the furnace door 11, and lower in the area near the second graphite boat 5 near the furnace tail 12. The process gas blows the dust generated between the first graphite boat 4 and the second graphite boat 5 towards the furnace tail 12. Due to gravity, the dust falls to the end of the second graphite boat 5 near the first graphite boat 4, and the silicon wafers in this area are also contaminated by dust.

[0044] In some other tubular PECVD coating equipment, the process gas inlet 6 is located at the furnace tail 12, and the process gas outlet 7 is located at the furnace door 11.

[0045] like Figure 2 As shown, in another embodiment of the tubular PECVD coating equipment, the process gas inlet 6 is located between the first graphite boat 4 and the second graphite boat 5, and the furnace door 11 and the furnace tail 12 are both provided with process gas outlets 7. Process gases are transported from the middle of furnace tube 1 to both ends, namely furnace door 11 and furnace tail 12. The concentration of process gases in the area where the first graphite boat 4 is located is equal to the concentration of process gases in the area where the second graphite boat 5 is located. Since the process gases are ionized and deposited on the silicon wafers, the concentration of process gases in the area where the first graphite boat 4 is closer to the second graphite boat 5 is greater than the concentration of process gases in the area where the first graphite boat 4 is farther from the second graphite boat 5. Similarly, the concentration of process gases in the area where the second graphite boat 5 is closer to the first graphite boat 4 is greater than the concentration of process gases in the area where the second graphite boat 5 is farther from the first graphite boat 4. When the process gases are transported between the first graphite boat 4 and the second graphite boat 5, the furnace door 11 and the furnace tail 12 simultaneously extract the gas. A portion of the process gases flows towards the furnace door 11, and another portion flows towards the furnace tail 12. The ends of the first graphite boat 4 and the second graphite boat 5 that are closer to the first graphite boat 4 are both contaminated with dust, and the silicon wafers in these two areas are also contaminated with dust.

[0046] like Figure 3As shown, in another embodiment of the tubular PECVD coating equipment, the process gas inlet 6 is located on one side of the first graphite boat 4 and the second graphite boat 5, and the process gas outlet 7 is located on the other side of the first graphite boat 4 and the second graphite boat 5. For example, the furnace tube 1 has multiple process gas inlets 6 arranged at equal intervals at the bottom, and multiple process gas outlets 7 arranged at equal intervals at the top. Alternatively, the process gas inlets 6 and process gas outlets 7 are respectively located on both sides of the horizontal direction of the furnace tube 1. The process gas is transported from the bottom to the top of the furnace tube 1. The concentration of the process gas in the area where the first graphite boat 4 is located is equal to the concentration of the process gas in the area where the second graphite boat 5 is located. However, due to the fluidity of the process gas and the obstruction of the graphite boats and silicon wafers themselves, some of the process gas will flow to the area between the first graphite boat 4 and the second graphite boat 5. Although the flow rate of the process gas passing through the area between the first graphite boat 4 and the second graphite boat 5 is less than that of the first graphite boat 5, the process gas will flow to the area between the first graphite boat 4 and the second graphite boat 5. Figure 1 and Figure 2 The flow rate of the process gas in the structure shown is low, but it still causes dust to be generated between the first graphite boat 4 and the second graphite boat 5, contaminating the graphite boat and the silicon wafer.

[0047] As attached Figure 4 As shown, if all rising edges of RF power supply one coincide with all rising edges of RF power supply two, then after multiple pulse cycles, excessive dust will be generated between the first graphite boat 4 and the second graphite boat 5, and the contamination of the graphite boat and silicon wafer will exceed the acceptable range.

[0048] like Figure 5 As shown, if the pulse width of RF power supply one is completely offset from the pulse width of RF power supply two, when RF power supply one is in the pulse width phase, RF power supply two is in the pulse off phase, and when RF power supply one is in the pulse off phase, RF power supply two is in the pulse width phase. That is, RF power supply one and RF power supply two are completely offset and have no overlapping pulse widths. For tubular PECVD coating equipment with two or more graphite boats loaded inside furnace tube 1, furnace tube 1 has a relatively long axial length. The completely offset pulse discharge of RF power supply one and RF power supply two means that RF power supply one and RF power supply two do not work together, and the plasma region formed is small.

[0049] This embodiment proposes the following control method, which includes:

[0050] During the joint operation of the first RF power supply 2 and the second RF power supply 3, both operate in pulse mode. At least a portion of the rising edges of the first RF power supply 2 do not coincide with a portion of the rising edges of the second RF power supply 3, and the pulse width of the first RF power supply 2 partially overlaps with the pulse width of the second RF power supply 3.

[0051] The period during which the first RF power supply 2 and the second RF power supply 3 operate in pulse mode refers to the time period during which both the first RF power supply 2 and the second RF power supply 3 are powered on and running as a whole. During this period, both the first RF power supply 2 and the second RF power supply 3 operate in pulse mode, with multiple pulse cycles. Each pulse cycle consists of a high-level segment and a low-level segment. The two ends of the high-level segment are the rising edge and the falling edge, respectively. During this period, the first RF power supply 2 has multiple rising edges and multiple falling edges, and the second RF power supply 3 also has multiple rising edges and multiple falling edges.

[0052] At least a portion of the rising edges of the first RF power supply 2 do not coincide with a portion of the rising edges of the second RF power supply 3. This means that the transient power generated by a single RF power supply at its rising edge does not further create a superposition effect, and the electric field between the first graphite boat 4 and the second graphite boat 5 will not be too strong, reducing dust generation. While some rising edges coincide, another portion do not, and the pulse widths partially overlap. For example, the pulse width of the first RF power supply 2 is smaller than the pulse width of the second RF power supply 3. When the first RF power supply 2 is at its rising edge, the second RF power supply 3 is not yet at its rising edge. After 10-60ms, the first RF power supply 2 is at its falling edge, and at this time, the second RF power supply 3 is at its pulse width. That is, the pulse widths partially overlap. The pulse widths of the first RF power supply 2 and the second RF power supply 3 are not completely staggered. The pulse widths of the first RF power supply 2 and the second RF power supply 3 partially overlap. During the overlap, the first RF power supply 2 and the second RF power supply 3 work together. The two plasma regions share the cavity potential of the furnace tube 1. The plasma regions of the first graphite boat 4 and the second graphite boat 5 expand. The plasmas inside the furnace tube 1 form a plasma background. The process gas located between the first graphite boat 4 and the second graphite boat 5 is also ionized and activated. In the axial direction of the furnace tube 1, the plasma distribution is relatively uniform, ensuring production efficiency and improving the uniformity between and within wafers.

[0053] like Figure 6 As shown, using the control method proposed in this embodiment, the rising edges of the first RF power supply 2 and the second RF power supply 3 coincide in the first pulse cycle. In the subsequent multiple pulse cycles, the rising edges of the first RF power supply 2 and the second RF power supply 3 do not coincide. Since both the first RF power supply 2 and the second RF power supply 3 are in periodic pulse operation mode, the rising edges will coincide again after multiple pulse cycles.

[0054] The control method of the present invention will be described in detail below with reference to different gas flow layouts.

[0055] Optionally, during the operation of the first RF power supply 2 and the second RF power supply 3 in pulse mode, the number of times the rising edges coincide is less than the number of times the rising edges do not coincide. That is, there are fewer times when transient output power is superimposed, and fewer times dust is generated, which means less pollution, thereby ensuring the coating effect.

[0056] for Figure 1 The airflow layout is such that the operating power of the first RF power supply 2 is greater than that of the second RF power supply 3. The operating power of the first RF power supply 2 is set to 5000-20000W, and the operating power of the second RF power supply 3 is set to 3000-18000W. For example, the first RF power supply 2 is 18000W and the second RF power supply 3 is 16000W. When depositing the doped amorphous silicon layer, the concentration of the process gas is higher in the region where the first graphite boat 4 is located, and lower in the region where the second graphite boat 5 is located. The power of the RF power supply is matched with the concentration of the process gas, and the region with higher concentration is matched with a higher power RF power supply.

[0057] The operating power of the first RF power supply 2 can be selected as 5000W, 8000W, 12000W, 15000W, or 20000W, and the operating power of the second RF power supply 3 can be selected as 3000W, 4000W, 5000W, 8000W, 12000W, or 15000W. The operating power of the first RF power supply 2 and the operating power of the second RF power supply 3 are selected according to the actual situation, and the operating power of the first RF power supply 2 is kept greater than the operating power of the second RF power supply 3.

[0058] for Figure 1 The airflow layout is such that the duty cycle of the second RF power supply 3 is greater than that of the first RF power supply 2. Since the process gas concentration is higher in the region where the first graphite boat 4 is located, and the operating power of the first RF power supply 2 is also higher, in order to ensure that the ionization intensity of the process gas in the region where the first graphite boat 4 is located is approximately equal to that in the region where the second graphite boat 5 is located, it is preferable that the duty cycle of the second RF power supply 3 is greater than that of the first RF power supply 2. This ensures that the deposition rate of the silicon wafer in the first graphite boat 4 is consistent with that in the second graphite boat 5, ultimately allowing for simultaneous material feeding.

[0059] for Figure 1 The airflow layout is such that the pulse width of the first RF power supply 2 is 10-60ms, and the pulse width of the second RF power supply 3 is 20-100ms. For example, the pulse width of the first RF power supply 2 is 10ms, 20ms, 30ms, 40ms, 50ms, and 60ms, and the pulse width of the second RF power supply 3 is 20ms, 30ms, 40ms, 50ms, 60ms, 70ms, 80ms, 90ms, and 100ms.

[0060] for Figure 1The airflow layout is such that, in a single pulse cycle, the pulse off-time of the first RF power supply 2 is 300-1500ms, and the pulse off-time of the second RF power supply 3 is 300-2000ms. For example, the pulse off-time of the first RF power supply 2 is 300ms, 400ms, 500ms, 600ms, 700ms, 800ms, 900ms, 1000ms, 1100ms, 1200ms, 1300ms, 1400ms, and 1500ms, and the pulse off-time of the second RF power supply 3 is 300ms, 400ms, 500ms, 600ms, 700ms, 800ms, 900ms, 1000ms, 1100ms, 1200ms, 1300ms, 1400ms, 1500ms, 1600ms, 1700ms, 1800ms, 1900ms, and 2000ms.

[0061] As one embodiment, the pulse width of the first RF power supply 2 is 10ms, the pulse off duration is 300ms, and the duty cycle of the first RF power supply 2 is 1:31. The pulse width of the second RF power supply 3 is 20ms, the pulse off duration is 300ms, and the duty cycle of the second RF power supply 3 is 2:32. The pulse period of the first RF power supply 2 is 310ms, and the pulse period of the second RF power supply 3 is 320ms. The least common multiple is 9920ms. Assuming that the rising edge of the first RF power supply 2 and the rising edge of the second RF power supply 3 coincide at the initial moment, then the rising edge coincides once every 9920ms. Within 9920ms, the first RF power supply 2 has 32 pulse periods, with only 1 rising edge coinciding and the other 31 rising edges not coinciding. The second RF power supply 3 has 31 pulse periods, with only 1 rising edge coinciding and the other 30 rising edges not coinciding. Therefore, the number of rising edge coinciding times is far less than the number of rising edge non-coinciding times, reducing dust generation.

[0062] In another embodiment, the pulse width of the first RF power supply 2 is 40ms, the pulse off duration is 400ms, and the duty cycle of the first RF power supply 2 is 1:11. The pulse width of the second RF power supply 3 is 80ms, the pulse off duration is 600ms, and the duty cycle of the second RF power supply 3 is 2:17. The least common multiple is 7480ms. Assuming that at the initial moment, the rising edge of the first RF power supply 2 and the rising edge of the second RF power supply 3 coincide, then the rising edge coincides once every 7480ms. Within 7480ms, the first RF power supply 2 has 17 pulse cycles, with only 1 rising edge coinciding and the other 16 rising edges not coinciding. The second RF power supply 3 has 11 pulse cycles, with only 1 rising edge coinciding and the other 10 rising edges not coinciding. Therefore, the number of rising edge coinciding times is far less than the number of rising edge non-coinciding times, reducing dust generation.

[0063] for Figure 2 and Figure 3 The airflow layout is such that the gas environment in the area where the first graphite boat 4 is located is basically the same as that in the area where the second graphite boat 5 is located. Therefore, the rising edge of the first RF power supply 2 and the rising edge of the second RF power supply 3 do not coincide. The pulse width of the first RF power supply 2 and the pulse width of the second RF power supply 3 partially overlap. The operating power of the first RF power supply 2 and the operating power of the second RF power supply 3 are equal. The pulse width of the first RF power supply 2 and the pulse width of the second RF power supply 3 are equal. The duty cycle of the first RF power supply 2 and the duty cycle of the second RF power supply 3 are equal.

[0064] In addition to the air intake and exhaust methods listed above, those skilled in the art can also configure the air intake and exhaust ports as needed.

[0065] This embodiment, based on the control method of the tubular PECVD coating equipment described above, further proposes a method for preparing solar cell film layers. This method includes the following steps:

[0066] S10. The second graphite boat 5 and the first graphite boat 4, each containing a silicon substrate 40, are loaded into the furnace tube 1. In actual operation, a robotic arm places the graphite boats onto a pusher paddle and sends them into the reaction chamber of the furnace tube 1.

[0067] S20, An interface passivation layer is grown or deposited on the silicon substrate 40.

[0068] The interface passivation layer can be selected from silicon oxide, silicon nitride, intrinsic amorphous silicon, or intrinsic polycrystalline silicon. For example, when the object being prepared is a TOPCon cell, the interface passivation layer is silicon oxide, and a thin silicon oxide layer constitutes a tunneling oxide layer 30. When the object being prepared is an HJT cell, the interface passivation layer is an intrinsic amorphous silicon layer.

[0069] Under normal pressure, the internal temperature of furnace tube 1 is adjusted to the preset deposition temperature (e.g., 430-450℃) and maintained at a constant temperature. Vacuuming and leak detection are then performed. After confirming the airtightness is acceptable, the process gas (e.g., nitrous oxide) required for the tunneling oxide layer 30 is introduced into the furnace tube 1, and the internal pressure of furnace tube 1 is adjusted to the required deposition pressure (e.g., 1800-2200 mtorr). Since nitrous oxide does not form dust, in step S20, the first RF power supply 2 and the second RF power supply 3 operate with the same process parameters. Specific process parameters can be: power 12000-16000W, pulse on-time 10ms, pulse off-time 300ms, and overall deposition time 90-120s. The overall deposition time refers to the time from the initial power-on of the RF power supply to its final power-off. The tunneling oxide layer 30 is formed on the surface of the silicon substrate 40 using plasma-enhanced chemical vapor deposition.

[0070] S30. Deposit a doped amorphous silicon layer on the tunnel oxide layer using the control method based on the tubular PECVD coating equipment in any of the foregoing embodiments.

[0071] For example, after evacuating the furnace tube 1, process gases required for the doped amorphous silicon layer, such as silane, hydrogen, and phosphine, are introduced and adjusted to the required pressure (e.g., 2500-3500 mtorr). Then, using the aforementioned control method based on the tubular PECVD coating equipment, a doped amorphous silicon layer is deposited on the tunneling oxide layer.

[0072] Step S30 can be performed once or multiple times depending on the doping concentration or thickness requirements to form one or more doped amorphous silicon layers.

[0073] In a further embodiment, the method for preparing the solar cell film layer further includes the following steps.

[0074] S40. After evacuating the reaction chamber, introduce the process gas required for the mask layer (such as silane and nitrous oxide), adjust it to the preset pressure (e.g., 1000-2000 mtorr), and turn on the corresponding RF power supply for each graphite boat to discharge. Deposit the mask layer on the doped amorphous silicon layer using plasma-enhanced chemical vapor deposition. For example, specific process parameters could be: power 10000-18000W, pulse on-time 10ms, off-time 300ms, and deposition time 30-90s. Since the mask layer is used to protect the doped amorphous silicon during annealing, and needs to be removed after the doped amorphous silicon anneals to form doped polycrystalline silicon, the control method of the tubular PECVD coating equipment described above can be used to prepare the mask layer according to actual needs.

[0075] The method for preparing the solar cell film layer of the present invention may further include the following steps:

[0076] S50. After deposition is completed, the inside of furnace tube 1 is evacuated to a low pressure state, and an inert gas (such as nitrogen) is introduced for purging and cleaning. Then, the pressure is restored to normal pressure, and the graphite boat with deposition completed is sent out of furnace tube 1.

[0077] The method for preparing the solar cell film layer of the present invention will be described in detail below based on specific process data. In this embodiment, there are two graphite boats in the furnace tube 1. The graphite boat near the furnace door 11 is called the front boat, and the graphite boat near the furnace tail 12 is called the rear boat. The values ​​in this embodiment are only specific values ​​for a certain batch of processes and are not intended to limit the scope of protection of the present invention. The specific values ​​of different batches of processes are different, and those skilled in the art can make adjustments according to the needs of the batch.

[0078] The paddle operation on the boat will complete the loading of the graphite boat with silicon substrate 40. The robotic arm will grab the graphite boat from the docking platform and place it onto the boat propeller.

[0079] The boat-entry operation involves sending the graphite boat on the paddle into the heating furnace tube. The specific actions are as follows: open the furnace door 11 → the paddle moves from the upper position to the front position → the paddle moves from the upper position to the lower position → the paddle moves from the lower position to the rear position → close the furnace door 11. The step time for this step is set to 120 seconds, the furnace temperature is set to 430-450℃, the nitrogen gas in the furnace is set to 10000 sccm, and the furnace pressure is set to 10000 mtorr.

[0080] The graphite boat is kept at a constant temperature in the furnace under normal pressure until it reaches the set temperature. The step time for this step is set to 360 seconds, the furnace temperature is set to 430-450℃, the furnace gas is set to 0 sccm, the furnace pressure is set to 10000 mtorr, and the auxiliary heating is set to turn on for 360 seconds at a temperature of 420℃.

[0081] Vacuuming operation: Open the main evacuation valve to evacuate the furnace to a low vacuum pressure state; the step time for this step is set to 720 seconds, the furnace temperature is set to 430-450℃, the furnace gas is set to 0 sccm, the furnace pressure is set to 0 mtorr, and the auxiliary heating is set to turn on for 240 seconds and at 420℃.

[0082] For leak detection, close the main extraction valve and check if the rate of pressure recovery from the bottom pressure in the furnace is normal (leakage rate standard ≤ 60 mtorr / min). The step time for this step is set to 30 seconds, the furnace temperature is set to 430-450℃, the furnace gas is set to 0 sccm, and the furnace pressure is set to 10000 mtorr.

[0083] The vacuuming operation is performed by opening the main vacuum valve and drawing the furnace pressure back to a low vacuum state. The step time for this step is set to 30 seconds, the furnace temperature is set to 430-450℃, the furnace gas temperature is set to 0 sccm, and the furnace pressure is set to 0 mtorr.

[0084] For constant pressure operation, open the main extraction valve and introduce the gas required for the deposition step into the furnace, maintaining the pressure required for the deposition step to provide the atmosphere required for the deposition step; the step time for this step is set to 30 seconds, the furnace temperature is set to 430-450℃, the nitrous oxide content in the furnace is set to 8000-12000 sccm, and the furnace pressure is set to 1800-2200 mtorr.

[0085] For the tunneling layer deposition operation, the main extraction valve is opened, and the gas required for the deposition step is introduced into the furnace and kept constant at the pressure required for the deposition step to provide the necessary atmosphere field. The radio frequency power supplies corresponding to each graphite boat are turned on in sequence to deposit thin films with glow discharge photoionized mixed gas. The step time for this step is set to 90-120 s, the furnace temperature is set to 430-450 ℃, the nitrous oxide gas in the furnace is set to 8000-12000 sccm, the furnace pressure is set to 1800-2200 mtorr, the power is set to 12000-16000 W, the pulse on is set to 10 ms, and the pulse off is set to 300 ms.

[0086] The vacuuming operation is performed by opening the main vacuum valve and drawing the furnace pressure back to a low vacuum state. The step time for this step is set to 30 seconds, the furnace temperature is set to 430-450℃, the furnace gas temperature is set to 0 sccm, and the furnace pressure is set to 0 mtorr.

[0087] Under constant pressure operation, open the main extraction valve and introduce the gas required for the deposition step into the furnace, maintaining the pressure at which the deposition step is required to provide the necessary atmosphere. The step time for this step is set to 30 seconds, the furnace temperature is set to 430-450℃, the furnace silane is set to 2500-3500 sccm, the hydrogen is set to 8000-10000 sccm, the phosphine is set to 150-350 sccm, and the furnace pressure is set to 2500-3500 mtorr.

[0088] For the preparation of the first polysilicon doped layer, the main extraction valve is opened, and the gas required for the deposition step is introduced into the furnace at the required pressure, providing the necessary atmosphere for the deposition step. The RF power supply is then turned on to ionize the mixed gas, and the thin film is deposited. The step time for this step is set to 120-240 seconds, the furnace temperature to 430-450°C, the furnace pressure to 2500-3500 sccm for silane, 8000-10000 sccm for hydrogen, and 150-350 sccm for phosphine, with the furnace pressure set to 2500-350 sccm. 0mtorr, the first power is set to 18000W, the first pulse on is set to 40ms, and the first pulse off is set to 400ms; the second power is set to 16000W, the second pulse on is set to 80ms, and the second pulse off is set to 480ms. The first power, first pulse, and first pulse off settings correspond to the operating power, pulse width, and pulse off duration of the pulse power supply corresponding to the preceding vessel. The second power, second pulse on, and second pulse off settings correspond to the operating power, pulse width, and pulse off duration of the pulse power supply corresponding to the following vessel. The RF power supply operates in pulse mode. After the RF power supply is started, the pulse on and pulse off cycles periodically. After the RF power supply is turned off, the periodic operation of pulse on and pulse off ceases.

[0089] The deposition logic for the second and third doped poly silicon layers below is the same as that for the first doped poly silicon layer, and both refer to the fabrication method of the first doped poly silicon layer mentioned above.

[0090] Under constant pressure operation, open the main extraction valve and introduce the gas required for the deposition step into the furnace, maintaining the pressure at which the deposition step is required, thus providing the necessary atmosphere for the deposition step. The step time for this step is set to 30 seconds, the furnace temperature is set to 430-450℃, the furnace gas flow rate for silane is set to 2500-3500 sccm, for hydrogen to 8000-10000 sccm, for phosphine to 150-350 sccm, and for the furnace pressure to 2500-4000 mtorr.

[0091] Preparation of the second doped poly silicon layer: Open the main extraction valve, introduce the gas required for the deposition step into the furnace, maintain the pressure required for the deposition step, and provide the atmosphere required for the deposition step; turn on the RF power supply to ionize the mixed gas and deposit the thin film; the step time of this step is set to 60-120S, the furnace temperature is set to 430-450℃, the furnace silane is set to 2500-3500sccm, the hydrogen is set to 8000-10000sccm, the phosphine is set to 150-350sccm, the furnace pressure is set to 2500-4000mtorr, the first power is set to 18000W, the first pulse on is set to 40ms, the first pulse off is set to 480ms, the second power is set to 16000W, the second pulse on is set to 80ms, and the second pulse off is set to 800ms.

[0092] Under constant pressure operation, open the main extraction valve and introduce the gas required for the deposition step into the furnace, maintaining the pressure at which the deposition step is required, thus providing the necessary atmosphere for the deposition step. The step time for this step is set to 30 seconds, the furnace temperature is set to 430-450℃, the furnace gas flow rate for silane is set to 2500-3500 sccm, for hydrogen to 8000-10000 sccm, for phosphine to 150-350 sccm, and for the furnace pressure to 2500-4000 mtorr.

[0093] For the preparation of the third doped poly silicon layer, the main extraction valve is opened, and the gas required for the deposition step is introduced into the furnace and kept constant at the pressure required for the deposition step to provide the atmosphere required for the deposition step. The radio frequency power supply is turned on to ionize the mixed gas and deposit the thin film. The step time of this step is set to 240-300 s, the furnace temperature is set to 430-450 ℃, the furnace silane is set to 2500-3500 sccm, the hydrogen is set to 8000-10000 sccm, the phosphine is set to 150-350 sccm, the furnace pressure is set to 2500-4000 mtorr, the first power is set to 18000 W, the first pulse on is set to 40 ms, the first pulse off is set to 480 ms, the second power is set to 16000 W, the second pulse on is set to 80 ms, and the second pulse off is set to 800 ms.

[0094] Perform a vacuuming operation by opening the main extraction valve to reduce the pressure inside the furnace after deposition to a low vacuum state. The step time for this step is set to 30 seconds, the furnace temperature is set to 430-450°C, all gases inside the furnace are set to 0 sccm, and the furnace pressure is set to 0 mtorr.

[0095] For constant pressure operation, open the main extraction valve and introduce the gas required for the deposition step into the furnace, maintaining the pressure at the required level to provide the necessary atmosphere for the deposition step. The step time for this step is set to 30 seconds, the furnace temperature to 430-450℃, the silane concentration to 1500-2500 sccm, the nitrous oxide concentration to 5000-10000 sccm, and the furnace pressure to 1000-2000 mtorr.

[0096] For mask layer preparation, the main extraction valve is opened, and the gas required for the deposition step is introduced into the furnace and kept constant to the pressure required for the deposition step to provide the atmosphere required for the deposition step. The radio frequency power supplies corresponding to each graphite boat are turned on in sequence to deposit thin films by photoionizing the mixed gas. The step time of this step is set to 30-90 s, the furnace temperature is set to 430-450℃, the furnace silane is set to 1500-2500 sccm, the nitrous oxide is set to 5000-10000 sccm, the furnace pressure is set to 1000-2000 mtorr, the power is set to 10000-18000 W, the pulse on is set to 3 ms, and the pulse off is set to 60 ms.

[0097] Perform a vacuuming operation by opening the main extraction valve to reduce the pressure inside the furnace after deposition to a low vacuum state. The step time for this step is set to 30 seconds, the furnace temperature is set to 430-450°C, all gases inside the furnace are set to 0 sccm, and the furnace pressure is set to 0 mtorr.

[0098] For the cleaning operation, open the main extraction valve and purge the furnace tubes with nitrogen under vacuum and low pressure. The step time for this step is set to 30 seconds, the furnace temperature is set to 430-450℃, the nitrogen level in the furnace is set to 10000-30000 sccm, and the furnace pressure is set to 0 mtorr.

[0099] Perform a vacuuming operation by opening the main vacuum valve and evacuating the pressure inside the cleaned furnace to a low vacuum state. The step time for this step is set to 30 seconds, the furnace temperature is set to 430-450℃, all gases inside the furnace are set to 0 sccm, and the furnace pressure is set to 0 mtorr.

[0100] For the backpressure operation, close the main extraction valve and introduce nitrogen gas to restore the pressure to atmospheric pressure under vacuum low pressure. The step time for this step is set to 60-120 seconds, the furnace temperature is set to 430-450℃, the nitrogen gas in the furnace is set to 50000 sccm, and the furnace pressure is set to 10000 mtorr.

[0101] The unloading operation involves removing the deposited graphite boat from the heating furnace tube onto the paddle. The specific actions are as follows: open the furnace door 11 → move the paddle from the lower position to the front position → move the paddle from the lower position to the upper position → move the paddle from the upper position to the rear position → close the furnace door 11. The step time for this step is set to 120 seconds, the furnace temperature is set to 430-450℃, the nitrogen gas in the furnace is set to 10000 sccm, and the furnace pressure is set to 10000 mtorr.

[0102] The paddles are used to lift the graphite boat loaded with silicon substrate 40 after deposition, and the robotic arm picks it up from the paddles and places it on the docking platform.

[0103] In this detailed embodiment, during the fabrication of the poly layer, the radio frequency power supply corresponding to each graphite boat is sequentially controlled to start discharging, thereby ensuring that there is a certain interval between the discharge start times of each radio frequency power supply and avoiding dust contamination.

[0104] This invention also protects the corresponding solar cells, such as Figure 7As shown, the solar cell includes a silicon substrate 40. The front side of the silicon substrate 40 is provided with an emitter 50, a front passivation layer 60, and a front antireflection layer 70. The back side of the silicon substrate 40 is provided with a tunneling oxide layer 30, a doped polycrystalline silicon layer 20, and a back antireflection layer 10. Along the direction from the back side of the solar cell to the front side, the back antireflection layer 10, the doped polycrystalline silicon layer 20, the tunneling oxide layer 30, the silicon substrate 40, the emitter 50, the front passivation layer 60, and the front antireflection layer 70 are arranged sequentially. The back side of the solar cell refers to the side facing away from sunlight, and the front side refers to the side facing sunlight. The doped polycrystalline silicon layer 20 is formed by annealing a doped amorphous silicon layer, which is prepared using the aforementioned solar cell film preparation method. The above description is only a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method based on a tubular PECVD coating equipment, wherein the tubular PECVD coating equipment includes a furnace tube (1), a first radio frequency power supply (2), and a second radio frequency power supply (3), wherein the two ends of the furnace tube (1) along the axial direction are a first end and a second end, respectively, and a first graphite boat (4) and a second graphite boat (5) are arranged sequentially and spaced apart inside the furnace tube (1) along the direction from the first end to the second end, wherein both the first graphite boat (4) and the second graphite boat (5) are loaded with a silicon substrate (40), the first graphite boat (4) corresponds to the first radio frequency power supply (2), and the second graphite boat (5) corresponds to the second radio frequency power supply (3), characterized in that, The control method includes: During the operation of the first RF power supply (2) and the second RF power supply (3), both operate in pulse mode. At least a portion of the rising edge of the first RF power supply (2) does not coincide with a portion of the rising edge of the second RF power supply (3), and the pulse width of the first RF power supply (2) partially overlaps with the pulse width of the second RF power supply (3).

2. The control method based on the tubular PECVD coating equipment according to claim 1, characterized in that, When a portion of the rising edge of the first RF power supply does not coincide with a portion of the rising edge of the second RF power supply (3), and another portion of the rising edge of the first RF power supply (2) coincides with another portion of the rising edge of the second RF power supply (3), the number of times the rising edges coincide is less than the number of times the rising edges do not coincide.

3. The control method for a tubular PECVD coating equipment according to claim 1 or 2, characterized in that, The process gas inlet (6) is located at the first end, and the process gas outlet (7) is located at the second end; The operating power of the first RF power supply (2) is greater than the operating power of the second RF power supply (3).

4. The control method based on the tubular PECVD coating equipment according to claim 3, characterized in that, The operating power of the first RF power supply (2) is set to 5000-20000W, and the operating power of the second RF power supply (3) is set to 3000-18000W.

5. The control method for a tubular PECVD coating equipment according to claim 3, characterized in that, The pulse width of the second RF power supply (3) is greater than the pulse width of the first RF power supply (2).

6. The control method for a tubular PECVD coating equipment according to claim 5, characterized in that, The duty cycle of the second RF power supply (3) is greater than the duty cycle of the first RF power supply (2).

7. The control method based on the tubular PECVD coating equipment according to claim 6, characterized in that, The pulse width of the first RF power supply (2) is 10-60ms, and the pulse width of the second RF power supply (3) is 20-100ms.

8. The control method for a tubular PECVD coating equipment according to claim 6, characterized in that, In a single pulse cycle, the pulse off duration of the first RF power supply (2) is 300-1500ms, and the pulse off duration of the second RF power supply (3) is 300-2000ms.

9. The control method based on the tubular PECVD coating equipment according to claim 1, characterized in that, The process gas inlet (6) is located between the first graphite boat (4) and the second graphite boat (5), and both the first end and the second end are provided with process gas outlets (7). Alternatively, the process gas inlet (6) is located on one side of the first graphite boat (4) and the second graphite boat (5), and the process gas outlet (7) is located on the other side of the first graphite boat (4) and the second graphite boat (5). The rising edge of the first RF power supply (2) does not coincide with the rising edge of the second RF power supply (3). The operating power of the first RF power supply (2) is equal to the operating power of the second RF power supply (3). The pulse width of the first RF power supply (2) is equal to the pulse width of the second RF power supply (3). The duty cycle of the first RF power supply (2) is equal to the duty cycle of the second RF power supply (3).

10. A method for preparing a solar cell film layer, characterized in that, Includes the following steps: S10. The second graphite boat (5) and the first graphite boat (4) loaded with silicon substrate (40) are loaded into the furnace tube (1). S20. An interface passivation layer is grown or deposited on the silicon substrate (40); S30. A doped amorphous silicon layer is deposited on the interface passivation layer using the control method based on the tubular PECVD coating equipment as described in any one of claims 1-9.

11. A solar cell, comprising a silicon substrate (40), wherein along the thickness direction of the silicon substrate (40), an interface passivation layer and a doped polycrystalline silicon layer (20) are sequentially disposed on the surface of the silicon substrate (40), the doped polycrystalline silicon layer (20) being formed by annealing a doped amorphous silicon layer, characterized in that, The doped amorphous silicon layer is prepared using the solar cell film preparation method as described in claim 10.

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