A method for preparing a back contact n-poly passivated battery by double-layer tunneling and poly

Abstract

The present invention belongs to the technical field of back contact passivated battery, and provides a method for preparing a back contact n-poly passivated battery by double-layer tunneling and poly. The thickness of the first layer of tunneling of the present invention is 1.25-1.35nm, and the thickness of the first layer of poly is 125-135nm; the thickness of the second layer of tunneling is 0.95-1.05nm, and the thickness of the second layer of poly is 115-125nm. The present invention selects low-pressure and high-temperature deposition, and deposits dense polycrystalline as much as possible, so as to obtain a film layer with good film thickness within and between sheets, and also reduce the contact resistance; through the process method of stacked tunneling + poly, combined with the diffusion doping temperature matching of phosphorus diffusion, a back contact battery with better contact can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of back contact passivation batteries, and in particular to a method for preparing a back contact n-poly passivation battery through double-layer tunneling and poly. Background Art

[0002] BC cell, which refers to the back contact cell, is an advanced design for improving the efficiency of solar cells. Its core design concept is to place all the metal electrodes of the cell on the back of the cell, so as to ensure that the front of the cell is not blocked by any metal grid lines, thereby maximizing the area of ​​the cell absorbing sunlight, reducing optical losses, and improving photoelectric conversion efficiency. Under the premise of constantly seeking high-efficiency cell conversion rates, BC back contact passivation has become the key to the process, and it must start with p-poly and n-poly. The previous passivation process also needs innovation, which requires low back contact, higher electrical performance and higher efficiency.

[0003] Therefore, it is of great significance to obtain a novel doped polysilicon back contact n-poly passivated cell which can reduce the back contact resistance and improve the efficiency. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing a back contact n-poly passivated cell by double-layer tunneling and poly in order to overcome the shortcomings of the prior art.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a back contact n-poly passivated battery by double-layer tunneling and poly.

[0007] The thickness of the first tunneling layer is 1.25-1.35 nm, and the thickness of the first poly layer is 125-135 nm;

[0008] The thickness of the second tunneling layer is 0.95-1.05 nm, and the thickness of the second poly layer is 115-125 nm.

[0009] Preferably, in the preparation of the double-layer tunneling, the temperature is independent at 595-625° C., and the pressure is independent at 750-770 torr; in the preparation of the poly layer, the temperature is independent at 590-620° C., and the pressure is independent at 175-185 mtorr.

[0010] Preferably, in the preparation of the first layer of tunneling, the oxygen flow rate is 19000-21000sccm, the time is 570-630s, in the preparation of the first layer of poly, the furnace mouth SiH4 flow rate is 290-330sccm, the furnace tail SiH4 flow rate is 950-1030sccm, and the time is 1500-1600s;

[0011] In the preparation of the second layer of tunneling, the oxygen flow rate is 14000~16000sccm, and the time is 950~1050s. In the preparation of the second layer of poly, the SiH4 flow rate at the furnace mouth is 300~320sccm, and the SiH4 flow rate at the furnace tail is 950~1050sccm, and the time is 1400~1500s.

[0012] Preferably, the method for preparing a back-contact n-poly passivated battery by double-layer tunneling and poly comprises the following steps: opening the furnace door at normal pressure, entering the boat, vacuuming once, picking up leaks once, heating once, constant temperature once, oxidizing at normal pressure, sealing the tank, vacuuming twice, constant temperature twice, purging once, constant temperature three times, picking up leaks twice, constant pressure, diffusion deposition, vacuuming three times, purging twice, breaking vacuum, and leaving the boat;

[0013] The above steps are completed to complete one layer of tunneling and poly. The double layers of tunneling and poly are completed by repeating the above steps twice. The first atmospheric pressure oxidation is used to prepare the first layer of tunneling, and the first diffusion deposition is used to prepare the first layer of poly; the second atmospheric pressure oxidation is used to prepare the second layer of tunneling, and the second diffusion deposition is used to prepare the second layer of poly.

[0014] As a preferred embodiment, the time for entering the boat is 60 to 90 seconds; the vacuum is evacuated once to a vacuum degree of 0 mtorr, and the time for evacuating once is 300 seconds;

[0015] The leakage rate of one leak detection is ≤25mtorr, and the time of one leak detection is 30 to 60s.

[0016] Preferably, the time from the first heating to the first constant temperature is 300 to 600 seconds, the temperature of the first constant temperature is 600 to 650° C., and the time is 300 to 600 seconds;

[0017] The temperature of the jar is 600-650℃, and the time is 600-1000s;

[0018] Evacuate the tube a second time until the gas pressure in the tube is 0 mtorr.

[0019] Preferably, the temperature of the secondary constant temperature is 600-650°C, and the holding time is 1560-2000s;

[0020] During the primary purge, nitrogen is introduced until the tube is completely filled with nitrogen. The temperature of the primary purge is 600-650°C and the time is 30-60s.

[0021] The temperature of the three constant temperatures is 600-650°C, and the holding time is 300-600s;

[0022] Evacuate to 0mtorr for secondary leak detection, the leakage rate of the secondary leak detection is ≤10mtorr, the time of the secondary leak detection is 30-60s, and the temperature is 600-650℃.

[0023] Preferably, the constant pressure is 200 mtorr, and the constant pressure time is 300 to 600 s;

[0024] After poly is prepared by diffusion deposition, phosphorus diffusion is performed, which includes doping and push-junction oxidation. The doping temperature is 780-810°C and the pressure is 130-150 mbar. The push-junction oxidation temperature is 850-890°C and the pressure is 130-150 mbar.

[0025] Preferably, the vacuum is pumped three times to a vacuum degree of 0 to 10 mtorr, the temperature of the three vacuum pumpings is 580 to 600° C., and the time is 200 to 300 s;

[0026] Nitrogen is introduced during the secondary purge until the tube is completely filled with nitrogen. The temperature of the secondary purge is 580-600° C. and the time is 30-60 seconds.

[0027] The beneficial effects of the present invention include the following:

[0028] 1) The method of the present invention selects low-pressure and high-temperature deposition to deposit dense polycrystalline as much as possible, so as to obtain film layers with good film thickness within and between sheets and reduce contact resistance; through the process method of stacked tunneling + poly, combined with the diffusion doping temperature matching of phosphorus diffusion, a back contact battery with better contact can be obtained; the back contact battery of the present invention has better passivation structure performance, improved passivation effect, lower back contact resistance and high conversion efficiency, and avoids the risk of high-doping over-penetration.

[0029] 2) The present invention only changes the process mode on the original equipment with unchanged battery structure, and uses a double-layer "tunneling + poly" process method to perform high-doping deep junction, and phosphorus diffusion to achieve in-situ doping with high surface concentration, effectively preventing internal diffusion, and improving minority carrier lifetime. It can also achieve lower ohmic contact, and ultimately improve the conversion efficiency of the back contact battery. DETAILED DESCRIPTION

[0030] The present invention provides a method for preparing a back contact n-poly passivated battery by double-layer tunneling and poly.

[0031] The thickness of the first tunneling layer is 1.25-1.35 nm, and the thickness of the first poly layer is 125-135 nm;

[0032] The thickness of the second tunneling layer is 0.95-1.05 nm, and the thickness of the second poly layer is 115-125 nm.

[0033] The thickness of the first tunneling layer of the present invention is preferably 1.27 to 1.33 nm, more preferably 1.3 nm, and the thickness of the first poly layer is preferably 127 to 133 nm, more preferably 130 nm;

[0034] The thickness of the second tunnel layer is preferably 0.97 to 1.03 nm, more preferably 1 nm, and the thickness of the second poly layer is preferably 117 to 123 nm, more preferably 120 nm.

[0035] In the present invention, in the preparation of double-layer tunneling, the temperature is preferably independent of 595-625°C, more preferably 600-620°C, more preferably 605-610°C, and the pressure is preferably independent of 750-770torr, more preferably 755-765torr, more preferably 760torr; in the preparation of the poly layer, the temperature is preferably independent of 590-620°C, more preferably 595-615°C, more preferably 600-605°C, and the pressure is preferably independent of 175-185mtorr, more preferably 178-182mtorr, more preferably 180mtorr.

[0036] In the present invention, in the preparation of the first layer of tunneling, the oxygen flow rate is preferably 19000-21000sccm, more preferably 19500-20500sccm, more preferably 20000sccm, and the time is preferably 570-630s, more preferably 580-620s, and more preferably 600s; in the preparation of the first layer of poly, the furnace mouth SiH4 flow rate is preferably 290-330sccm, more preferably 300-320sccm, and more preferably 310sccm, and the furnace tail SiH4 flow rate is preferably 950-1030sccm, more preferably 970-1010sccm, and more preferably 990sccm, and the time is preferably 1500-1600s, more preferably 1530-1570s, and more preferably 1550-1560s;

[0037] In the preparation of the second layer of tunneling, the oxygen flow rate is preferably 14000-16000sccm, further preferably 14500-15500sccm, more preferably 15000sccm, and the time is preferably 950-1050s, further preferably 980-1020s, more preferably 1000s. In the preparation of the second layer of poly, the SiH4 flow rate at the furnace mouth is preferably 300-320sccm, further preferably 305-315sccm, more preferably 310sccm, and the SiH4 flow rate at the furnace tail is preferably 950-1050sccm, further preferably 980-1020sccm, more preferably 990-1000sccm. The time is preferably 1400-1500s, further preferably 1420-1480s, more preferably 1440-1450s.

[0038] In the present invention, the method for preparing a back contact n-poly passivated battery by double-layer tunneling and poly preferably comprises the following steps: opening the furnace door at normal pressure, entering the boat, vacuuming once, checking for leaks once, heating once, constant temperature once, oxidizing at normal pressure, sealing the tank, vacuuming twice, constant temperature twice, purging once, constant temperature three times, checking for leaks twice, constant pressure, diffusion deposition, vacuuming three times, purging twice, breaking the vacuum, and exiting the boat;

[0039] The above steps are completed to complete one layer of tunneling and poly. The double layers of tunneling and poly are completed by repeating the above steps twice. The first atmospheric pressure oxidation is used to prepare the first layer of tunneling, and the first diffusion deposition is used to prepare the first layer of poly; the second atmospheric pressure oxidation is used to prepare the second layer of tunneling, and the second diffusion deposition is used to prepare the second layer of poly.

[0040] In the present invention, the time for entering the boat is preferably 60 to 90 seconds, more preferably 70 to 80 seconds, and more preferably 75 seconds; the vacuum is preferably drawn once to a vacuum degree of 0 mtorr, and the time for drawing the vacuum once is preferably 300 seconds;

[0041] The leakage rate of one leak detection is preferably ≤25mtorr, more preferably ≤20mtorr, and the time of one leak detection is preferably 30 to 60s, more preferably 40 to 50s, and more preferably 45s.

[0042] In the present invention, the time from the first heating to the first constant temperature is preferably 300 to 600 s, more preferably 400 to 500 s, more preferably 450 s, the temperature of the first constant temperature is preferably 600 to 650° C., more preferably 610 to 640° C., more preferably 620 to 630° C., and the time is preferably 300 to 600 s, more preferably 400 to 500 s, more preferably 450 s;

[0043] The temperature of the simmering tank is preferably 600-650°C, more preferably 610-640°C, more preferably 620-630°C, and the time is preferably 600-1000s, more preferably 700-900s, more preferably 800s;

[0044] The second vacuuming is preferably performed until the gas in the tube reaches 0 mtorr.

[0045] In the present invention, the temperature of the secondary thermostat is preferably 600-650°C, more preferably 610-640°C, more preferably 620-630°C, and the holding time is preferably 1560-2000s, more preferably 1660-1900s, more preferably 1760-1800s;

[0046] Preferably, nitrogen is introduced during the primary purge until the tube is completely filled with nitrogen. The primary purge temperature is preferably 600-650° C., more preferably 610-640° C., more preferably 620-630° C., and the time is preferably 30-60 s, more preferably 40-50 s, more preferably 45 s.

[0047] The temperature of the three constant temperatures is preferably 600-650°C, more preferably 610-640°C, more preferably 620-630°C, and the time is preferably 300-600s, more preferably 400-500s, more preferably 450s;

[0048] The vacuum is evacuated to 0 mtorr for secondary leak detection. The leakage rate of the secondary leak detection is preferably ≤10 mtorr, and more preferably ≤5 mtorr. The time for secondary leak detection is preferably 30 to 60 s, and more preferably 40 to 50 s, and more preferably 45 s. The temperature is preferably 600 to 650°C, and more preferably 610 to 640°C, and more preferably 620 to 630°C.

[0049] In the present invention, the constant pressure is preferably 200 mtorr, and the constant pressure time is preferably 300 to 600 s, more preferably 400 to 500 s, and more preferably 450 s; the purpose of the constant pressure is to better deposit poly;

[0050] After poly is prepared by diffusion deposition, phosphorus diffusion is performed. The phosphorus diffusion preferably includes doping and push-up oxidation. The doping temperature is preferably 780-810°C, further preferably 785-805°C, more preferably 795°C, the pressure is preferably 130-150mbar, further preferably 135-145mbar, more preferably 140mbar, the push-up oxidation temperature is preferably 850-890°C, further preferably 860-880°C, more preferably 870°C, the pressure is preferably 130-150mbar, further preferably 135-145mbar, more preferably 140mbar.

[0051] In the present invention, the vacuum is preferably pumped three times to a vacuum degree of 0 to 10 mtorr, more preferably 3 to 7 mtorr, the temperature of the three vacuum pumpings is preferably 580 to 600° C., more preferably 590° C., the time is preferably 200 to 300 s, more preferably 220 to 280 s, and more preferably 240 to 250 s;

[0052] Nitrogen is preferably introduced during the secondary purge until the tube is completely filled with nitrogen. The temperature of the secondary purge is preferably 580-600°C, more preferably 590°C, and the time is preferably 30-60s, more preferably 40-50s, and more preferably 45s.

[0053] In the present invention, the atmospheric pressure oxidation and diffusion deposition method is low pressure chemical vapor deposition, plasma enhanced chemical vapor deposition or physical vapor deposition.

[0054] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0055] In the embodiment, an N-type C-Si silicon wafer is used as a substrate.

[0056] Example 1

[0057] The method for preparing a back contact n-poly passivated cell by double-layer tunneling and poly comprises the following steps:

[0058] S01: Start at normal pressure and open the furnace door;

[0059] S02: Enter the boat, time set to 75s;

[0060] S03: vacuum to 0 mtorr under normal pressure, vacuum time is 300 s;

[0061] S04: Check for leaks after evacuation, ensuring the leak rate is within 25mtorr, and the leak checking time is 45s;

[0062] S05: heating to process temperature 620°C for 450s;

[0063] S06: constant temperature 620℃, constant temperature time 450s;

[0064] S07: prepare SiO2 layer by atmospheric pressure oxidation (first tunneling oxygen deposition): pressure is 760 torr, oxidation temperature is 610°C, oxygen flow rate is 20000 sccm, oxidation time is 600 s, and the thickness of the first tunneling SiO2 layer is 1.3 nm;

[0065] S08: 620℃ jar-warming for 800s;

[0066] S09: Evacuate at 620℃ until the gas in the tube is 0 mtorr;

[0067] S10: constant temperature 620℃, holding time 1760s;

[0068] S11: Purge the furnace tube with N2 at 620°C to remove other gases from the tube for 45 seconds;

[0069] S12: constant temperature 620°C, holding time 450s;

[0070] S13: Evacuate the tube until the gas in the tube is 0 mtorr and check for leaks, ensuring that the leak rate is within 10 mtorr, the leak detection time is 45 seconds, and the temperature is 620°C;

[0071] S14: 200 mtorr pressure for 450 s to better deposit poly;

[0072] S15: low pressure chemical vapor deposition method is used for diffusion deposition (first layer of poly): temperature is 605°C, pressure is 180mtorr, SiH4 flow rate at furnace inlet is 310sccm, SiH4 flow rate at furnace tail is 990sccm, and SiH4 introduction time is 1560s; the thickness of the first layer of poly is 130nm;

[0073] After poly is prepared by diffusion deposition, phosphorus diffusion is performed, and phosphorus diffusion is performed at a pressure of 140 mbar and 795°C for doping, and junction oxidation is performed at a pressure of 140 mbar and 870°C;

[0074] S16: at a temperature of 590°C, evacuate to 3 mtorr for 250 s;

[0075] S17: Purge the furnace tube with N2 at 590°C to remove other gases from the tube for 45 seconds;

[0076] S18: Fill with N2 to bring the internal pressure to normal pressure;

[0077] S19: After the atmospheric pressure is finished, the furnace door is opened to take out the boat, and one layer of tunneling and poly is completed.

[0078] In the second tunneling and poly, only the S07 and S15 steps are changed, and the other conditions are the same as the first time; S07: atmospheric pressure oxidation (second tunneling oxygen deposition) to prepare SiO2 layer: pressure is 760torr, oxidation temperature is 610℃, oxygen flow rate is 15000sccm, oxidation time is 1000s, and the thickness of the second tunneling SiO2 layer is 1nm;

[0079] S15: Use low-pressure chemical vapor deposition for diffusion deposition (second layer of poly): temperature is 605°C, pressure is 180mtorr, SiH4 flow rate at the furnace mouth is 310sccm, SiH4 flow rate at the furnace tail is 990sccm, and SiH4 introduction time is 1440s; the thickness of the second layer of poly is 120nm, and the phosphorus diffusion process remains unchanged.

[0080] Example 2

[0081] The method for preparing a back contact n-poly passivated cell by double-layer tunneling and poly comprises the following steps:

[0082] S01: Start at normal pressure and open the furnace door;

[0083] S02: Enter the boat, time set to 60s;

[0084] S03: vacuum to 0 mtorr under normal pressure, vacuum time is 300 s;

[0085] S04: Check for leaks after evacuation, ensuring the leak rate is within 20mtorr, and the leak checking time is 30s;

[0086] S05: heating to process temperature 600°C for 300s;

[0087] S06: constant temperature 600℃, constant temperature time 300s;

[0088] S07: prepare SiO2 layer by atmospheric pressure oxidation (first tunneling oxygen deposition): pressure is 760 torr, oxidation temperature is 600°C, oxygen flow rate is 19500 sccm, oxidation time is 580 s, and the thickness of the first tunneling SiO2 layer is 1.27 nm;

[0089] S08: 600℃ jar-stifling for 1000s;

[0090] S09: Evacuate at 600℃ until the gas in the tube is 0 mtorr;

[0091] S10: constant temperature 600°C, holding time 1560s;

[0092] S11: Purge the furnace tube with N2 at 600°C to remove other gases from the tube for 30 seconds;

[0093] S12: constant temperature 600°C, holding time 300s;

[0094] S13: Evacuate the tube until the gas in the tube is 0 mtorr and check for leaks, ensuring that the leak rate is within 5 mtorr, the leak detection time is 30 seconds, and the temperature is 600°C;

[0095] S14: 200 mtorr pressure for 300 s to better deposit poly;

[0096] S15: low pressure chemical vapor deposition method is used for diffusion deposition (first layer of poly): temperature is 595°C, pressure is 175mtorr, SiH4 flow rate at the furnace mouth is 300sccm, SiH4 flow rate at the furnace tail is 970sccm, and SiH4 introduction time is 1530s; the thickness of the first layer of poly is 133nm;

[0097] After poly is prepared by diffusion deposition, phosphorus diffusion is performed, and phosphorus diffusion is performed at a pressure of 135 mbar and 785°C, and junction oxidation is performed at a pressure of 135 mbar and 860°C;

[0098] S16: vacuuming to 0 mtorr at 580°C for 200 s;

[0099] S17: Purge the furnace tube with N2 at 580°C to remove other gases from the tube for 30 seconds;

[0100] S18: Fill with N2 to bring the internal pressure to normal pressure;

[0101] S19: After the atmospheric pressure is finished, the furnace door is opened to take out the boat, and one layer of tunneling and poly is completed.

[0102] In the second tunneling and poly expansion, only the S07 and S15 steps are changed, and the other conditions are the same as the first time; S07: atmospheric pressure oxidation (second tunneling oxygen deposition) to prepare SiO2 layer: pressure is 760torr, oxidation temperature is 600℃, oxygen flow rate is 14500sccm, oxidation time is 980s, and the thickness of the second tunneling SiO2 layer is 0.97nm;

[0103] S15: Use low-pressure chemical vapor deposition for diffusion deposition (second layer of poly): temperature is 595°C, pressure is 175mtorr, SiH4 flow rate at the furnace mouth is 305sccm, SiH4 flow rate at the furnace tail is 980sccm, and SiH4 introduction time is 1420s; the thickness of the second layer of poly is 123nm, and the phosphorus diffusion process remains unchanged.

[0104] Example 3

[0105] The method for preparing a back contact n-poly passivated cell by double-layer tunneling and poly comprises the following steps:

[0106] S01: Start at normal pressure and open the furnace door;

[0107] S02: Enter the boat, time set to 90s;

[0108] S03: vacuum to 0 mtorr under normal pressure, vacuum time is 300 s;

[0109] S04: Check for leaks after evacuation, ensuring the leak rate is within 25mtorr, and the leak checking time is 60s;

[0110] S05: heating to process temperature 650°C for 600s;

[0111] S06: constant temperature 650℃, constant temperature time 600s;

[0112] S07: prepare SiO2 layer by atmospheric pressure oxidation (first tunneling oxygen deposition): pressure is 760 torr, oxidation temperature is 620°C, oxygen flow rate is 20500 sccm, oxidation time is 620 s, and the thickness of the first tunneling SiO2 layer is 1.33 nm;

[0113] S08: 650℃ jarring for 600s;

[0114] S09: Evacuate at 650℃ until the gas in the tube is 0 mtorr;

[0115] S10: constant temperature 650°C, holding time 2000s;

[0116] S11: Purge the furnace tube with N2 at 650°C to remove other gases from the tube for 60 seconds;

[0117] S12: constant temperature 650°C, holding time 600s;

[0118] S13: Evacuate the tube until the gas in the tube is 0 mtorr and check for leaks, ensuring that the leak rate is within 10 mtorr, the leak detection time is 60 seconds, and the temperature is 650°C;

[0119] S14: 200 mtorr pressure for 600 s to better deposit poly;

[0120] S15: low pressure chemical vapor deposition method is used for diffusion deposition (first layer of poly): temperature is 615°C, pressure is 185mtorr, SiH4 flow rate at the furnace mouth is 320sccm, SiH4 flow rate at the furnace tail is 1010sccm, and SiH4 introduction time is 1570s; the thickness of the first layer of poly is 127nm;

[0121] After poly is prepared by diffusion deposition, phosphorus diffusion is performed, and phosphorus diffusion is performed at a pressure of 145 mbar and 805°C for doping, and junction oxidation is performed at a pressure of 145 mbar and 880°C;

[0122] S16: at 600°C, evacuate to 10 mtorr for 300 s;

[0123] S17: Purge the furnace tube with N2 at 600°C to remove other gases from the tube for 60 seconds;

[0124] S18: Fill with N2 to bring the internal pressure to normal pressure;

[0125] S19: After the atmospheric pressure is over, the furnace door is opened to take out the boat, and a layer of tunneling and phosphorus expansion is completed.

[0126] In the second tunneling and poly, only the S07 and S15 steps are changed, and the other conditions are the same as the first time; S07: atmospheric pressure oxidation (second tunneling oxygen deposition) to prepare the SiO2 layer: pressure is 760torr, oxidation temperature is 620℃, oxygen flow rate is 15500sccm, oxidation time is 1020s, and the thickness of the second tunneling SiO2 layer is 1.03nm;

[0127] S15: Use low-pressure chemical vapor deposition for diffusion deposition (second layer of poly): temperature is 615°C, pressure is 185mtorr, SiH4 flow rate at the furnace mouth is 315sccm, SiH4 flow rate at the furnace tail is 1020sccm, and SiH4 introduction time is 1480s; the thickness of the second layer of poly is 117nm, and the phosphorus diffusion process remains unchanged.

[0128] The effect values ​​of multiple tests of the back contact n-poly passivated battery prepared in Example 1 are shown in Table 1, where each row in Table 1 represents the effect of a battery cell.

[0129] Table 1 Effect of back contact n-poly passivated battery prepared in Example 1

[0130]

[0131]

[0132] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a back contact n-poly passivated cell by double-layer tunneling and poly, characterized in that: The thickness of the first tunneling layer is 1.25-1.35 nm, and the thickness of the first poly layer is 125-135 nm; The thickness of the second tunneling layer is 0.95-1.05 nm, and the thickness of the second poly layer is 115-125 nm.

2. The method according to claim 1, characterized in that In the preparation of the double-layer tunneling, the temperature is independent of 595-625°C, and the pressure is independent of 750-770 torr; in the preparation of the poly layer, the temperature is independent of 590-620°C, and the pressure is independent of 175-185 mtorr.

3. The method according to claim 1 or 2, characterized in that: In the preparation of the first layer of tunneling, the oxygen flow rate is 19000-21000sccm, the time is 570-630s, in the preparation of the first layer of poly, the SiH4 flow rate at the furnace mouth is 290-330sccm, the SiH4 flow rate at the furnace tail is 950-1030sccm, and the time is 1500-1600s; In the preparation of the second layer of tunneling, the oxygen flow rate is 14000~16000sccm, and the time is 950~1050s. In the preparation of the second layer of poly, the SiH4 flow rate at the furnace mouth is 300~320sccm, and the SiH4 flow rate at the furnace tail is 950~1050sccm, and the time is 1400~1500s.

4. The method according to claim 3, characterized in that: The method for preparing a back-contact n-poly passivated battery by double-layer tunneling and poly comprises the following steps: opening a furnace door at normal pressure, entering a boat, vacuuming once, checking for leaks once, heating once, maintaining a constant temperature once, oxidizing at normal pressure, sealing the tank, vacuuming twice, maintaining a constant temperature twice, purging once, maintaining a constant temperature three times, checking for leaks twice, maintaining a constant pressure, diffusion deposition, vacuuming three times, purging twice, breaking the vacuum, and exiting the boat; The above steps are completed to complete one layer of tunneling and poly. The double layers of tunneling and poly are completed by repeating the above steps twice. The first atmospheric pressure oxidation is used to prepare the first layer of tunneling, and the first diffusion deposition is used to prepare the first layer of poly; the second atmospheric pressure oxidation is used to prepare the second layer of tunneling, and the second diffusion deposition is used to prepare the second layer of poly.

5. The method according to claim 4, characterized in that The time for entering the boat is 60 to 90 seconds; the vacuum is pumped once to a vacuum degree of 0 mtorr, and the time for the vacuum is 300 seconds; The leakage rate of one leak detection is ≤25mtorr, and the time of one leak detection is 30 to 60s.

6. The method according to claim 4 or 5, characterized in that: The time from the first heating to the first constant temperature is 300-600s, the temperature of the first constant temperature is 600-650°C, and the time is 300-600s; The temperature of the jar is 600-650℃, and the time is 600-1000s; Evacuate the tube a second time until the gas in the tube is 0 mtorr.

7. The method according to claim 6, characterized in that The temperature of the secondary constant temperature is 600-650°C, and the holding time is 1560-2000s; During the primary purge, nitrogen is introduced until the tube is completely filled with nitrogen. The temperature of the primary purge is 600-650°C and the time is 30-60s. The temperature of the three constant temperatures is 600-650°C, and the holding time is 300-600s; Evacuate to 0mtorr for secondary leak detection, the leakage rate of the secondary leak detection is ≤10mtorr, the time of the secondary leak detection is 30-60s, and the temperature is 600-650℃.

8. The method according to claim 7, characterized in that The constant pressure is 200 mtorr, and the constant pressure time is 300 to 600 s; After poly is prepared by diffusion deposition, phosphorus diffusion is performed, which includes doping and push-junction oxidation. The doping temperature is 780-810°C and the pressure is 130-150 mbar. The push-junction oxidation temperature is 850-890°C and the pressure is 130-150 mbar.

9. The method according to claim 8, characterized in that The vacuum is pumped three times to a vacuum degree of 0 to 10 mtorr, the temperature of the three vacuum pumpings is 580 to 600°C, and the time is 200 to 300 seconds; Nitrogen is introduced during the secondary purge until the tube is completely filled with nitrogen. The temperature of the secondary purge is 580-600° C. and the time is 30-60 seconds.

Images