A method for preparing a back contact passivated battery using three-layer tunneling and poly

Abstract

The present invention belongs to the technical field of back contact batteries, and provides a method for preparing a back contact passivated battery with three layers of tunneling and poly. The thickness of the first layer of tunneling of the present invention is 0.75-0.85nm, and the thickness of the first layer of poly is 115-125nm; the thickness of the second layer of tunneling is 0.75-0.85nm, and the thickness of the second layer of poly is 95-105nm; the thickness of the third layer of tunneling is 0.95-1.05nm, and the thickness of the third layer of poly is 170-190nm. The method of the present invention selects low-pressure deposition, and deposits dense amorphous as much as possible, so as to obtain a film layer with good film thickness within and between sheets, and can also reduce contact resistance, thereby improving battery conversion efficiency.

Description

Technical Field

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

[0002] Under the premise of constantly seeking high conversion rate of cells, a new cell technology, namely BC cell, has been derived from Topcon and PERC technology. BC cell refers to back contact cell, which is an advanced design used to improve the efficiency of solar cells. Its core design concept is to maximize the area of ​​solar light absorbed by the cell on the front side, increase optical absorption, and improve photoelectric conversion efficiency.

[0003] BC cells have both the mature technology of Topcon and PERC, as well as stable yields, and higher cell conversion efficiency than the two. They have made breakthroughs in the passivation and cell structure of Topcon and PERC, and therefore have higher electrical performance. Combining these advantages, BC has a broad space for efficiency development, and can pursue an extreme efficiency of 29.1%.

[0004] Therefore, it is of great significance to obtain a new type of doped back contact passivated battery with lower back contact resistance and high conversion efficiency. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a back contact passivation cell by three-layer tunneling and poly in order to overcome the shortcomings of the prior art.

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

[0007] The present invention provides a method for preparing a back contact passivation battery by three-layer tunneling and poly.

[0008] The thickness of the first tunneling layer is 0.75-0.85 nm, and the thickness of the first poly layer is 115-125 nm;

[0009] The thickness of the second tunneling layer is 0.75-0.85 nm, and the thickness of the second poly layer is 95-105 nm;

[0010] The thickness of the third tunneling layer is 0.95-1.05 nm, and the thickness of the third poly layer is 170-190 nm.

[0011] Preferably, in the preparation of the three-layer tunneling, the temperature is independent of 590-630° C., and the pressure is independent of 750-770 torr; in the preparation of the poly layer, the temperature is independent of 530-570° C., and the pressure is independent of 175-185 mtorr.

[0012] As a preference, in the preparation of the first layer of tunneling, the oxygen flow rate is 9000-11000sccm, the time is 550-650s, and in the preparation of the first layer of poly, the furnace port SiH 4 The flow rate is 340~360sccm, SiH 4 The flow rate is 1100-1300 sccm and the time is 2800-3200 s;

[0013] In the preparation of the second layer of tunneling, the oxygen flow rate is 14000~16000sccm, the time is 900~1100s, and in the preparation of the second layer of poly, the furnace port SiH 4 The flow rate is 300~320sccm, SiH 4 The flow rate is 900-1100 sccm and the time is 2400-2800 s;

[0014] In the third layer tunneling preparation, the oxygen flow rate is 18000~20000sccm, the time is 900~1100s, and in the third layer poly preparation, the furnace port SiH 4 The flow rate is 300~320sccm, SiH 4 The flow rate is 900-1100 sccm and the time is 3800-4200 s.

[0015] Preferably, the method for preparing a back contact passivated battery by three-layer tunneling and poly comprises the following steps: opening the furnace door at normal pressure, entering the boat, vacuuming once, vacuuming twice, picking up leaks once, heating, constant temperature once, oxidizing at normal pressure, sealing the tank, vacuuming three times, cooling, purging once, constant temperature twice, picking up leaks twice, constant pressure, diffusion deposition, vacuuming four times, purging twice, breaking vacuum, and exiting the boat;

[0016] The above steps are completed to complete one layer of tunneling and poly. Three layers of tunneling and poly are completed by repeating the above steps three times. The first normal pressure oxidation is to prepare the first layer of tunneling, and the first diffusion deposition is to prepare the first layer of poly; the second normal pressure oxidation is to prepare the second layer of tunneling, and the second diffusion deposition is to prepare the second layer of poly; the third normal pressure oxidation is to prepare the third layer of tunneling, and the third diffusion deposition is to prepare the third layer of poly.

[0017] Preferably, the time for entering the boat is 60 to 90 seconds; the vacuum is evacuated once to a vacuum degree of 0 to 700 mtorr, and the time for the first vacuum is 50 seconds; the vacuum is evacuated twice to a vacuum degree of 0 to 10 mtorr, and the time for the second vacuum is 200 to 300 seconds; the leakage rate of the first leak detection is ≤25 mtorr, and the time for the first leak detection is 30 to 60 seconds.

[0018] Preferably, the time for heating to a constant temperature is 300 to 600 seconds, the temperature of the constant temperature is 580 to 650° C., and the time is 300 to 600 seconds;

[0019] The temperature of the can is 580-650°C and the time is 600-1000s.

[0020] Preferably, the tube is vacuumed three times until the gas in the tube is 0 mtorr; the temperature is lowered to 500-550° C., and the cooling time is 3000-6000 s;

[0021] The temperature of the secondary constant temperature is 500-550°C and the 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 500-550℃.

[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, boron diffusion is performed. Boron diffusion includes doping and push-junction oxidation. The doping temperature is 825-845°C and the pressure is 130-150 mbar. The push-junction oxidation temperature is 940-960°C and the pressure is 390-410 mbar.

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

[0026] Nitrogen is introduced into the primary purge and the secondary purge until the tube is completely filled with nitrogen. The time of the primary purge and the secondary purge is independently 30 to 60 seconds.

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

[0028] 1) The method of the present invention selects low-pressure deposition and deposits dense amorphous materials as much as possible, so as to obtain film layers with good film thickness within and between sheets, and a good passivation structure, which can reduce contact resistance and improve battery conversion efficiency.

[0029] 2) The method of the present invention only changes the process mode on the original equipment with unchanged battery structure; high doping and deep junction are achieved through the poly stacking process method to solve the risk of high doping over-punchthrough. The back contact battery of the present invention has lower back contact resistance and high conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the overall structure of a back contact passivation battery prepared by the method of the present invention. DETAILED DESCRIPTION

[0031] The present invention provides a method for preparing a back contact passivation battery by three-layer tunneling and poly.

[0032] The thickness of the first tunneling layer is 0.75-0.85 nm, and the thickness of the first poly layer is 115-125 nm;

[0033] The thickness of the second tunneling layer is 0.75-0.85 nm, and the thickness of the second poly layer is 95-105 nm;

[0034] The thickness of the third tunneling layer is 0.95-1.05 nm, and the thickness of the third poly layer is 170-190 nm.

[0035] The thickness of the first tunneling layer of the present invention is preferably 0.78-0.82nm, more preferably 0.8nm, and the thickness of the first poly layer is preferably 118-122nm, more preferably 120nm; the thickness of the second tunneling layer is preferably 0.78-0.82nm, more preferably 0.8nm, and the thickness of the second poly layer is preferably 98-102nm, more preferably 100nm; the thickness of the third tunneling layer is preferably 0.98-1.02nm, more preferably 1nm, and the thickness of the third poly layer is preferably 175-185nm, more preferably 180nm.

[0036] In the present invention, in the preparation of the three-layer tunneling, the temperature is independent and preferably 590-630°C, more preferably 600-620°C, more preferably 610°C, and the pressure is independent and preferably 750-770torr, more preferably 760torr; in the preparation of the poly layer, the temperature is independent and preferably 530-570°C, more preferably 540-560°C, more preferably 550°C, and the pressure is independent and preferably 175-185mtorr, more preferably 180mtorr.

[0037] In the present invention, the three-layer tunneling and poly are preferably deposited by low pressure chemical vapor deposition, plasma enhanced chemical vapor deposition or physical vapor deposition.

[0038] In the present invention, in the preparation of the first layer of tunneling, the oxygen flow rate is preferably 9000-11000sccm, more preferably 9500-10500sccm, more preferably 10000sccm, the time is preferably 550-650s, more preferably 580-620s, more preferably 600s, in the preparation of the first layer of poly, the furnace port SiH 4 The flow rate is preferably 340-360 sccm, more preferably 345-355 sccm, and more preferably 350 sccm. 4The flow rate is preferably 1100-1300 sccm, more preferably 1150-1250 sccm, more preferably 1200 sccm, and the time is preferably 2800-3200 s, more preferably 2900-3100 s, more preferably 3000 s;

[0039] In the preparation of the second layer of tunneling, the oxygen flow rate is preferably 14000-16000sccm, more preferably 14500-15500sccm, more preferably 15000sccm, the time is preferably 900-1100s, more preferably 950-1050s, more preferably 1000s, in the preparation of the second layer of poly, the furnace port SiH 4 The flow rate is preferably 300-320 sccm, more preferably 305-315 sccm, and more preferably 310 sccm. 4 The flow rate is preferably 900-1100 sccm, more preferably 950-1050 sccm, more preferably 1000 sccm, and the time is preferably 2400-2800 s, more preferably 2500-2700 s, more preferably 2600 s;

[0040] In the preparation of the third layer of tunneling, the oxygen flow rate is preferably 18000-20000sccm, more preferably 18500-19500sccm, more preferably 19000sccm, the time is preferably 900-1100s, more preferably 950-1050s, more preferably 1000s, in the preparation of the third layer of poly, the furnace port SiH 4 The flow rate is preferably 300-320 sccm, more preferably 305-315 sccm, and more preferably 310 sccm. 4 The flow rate is preferably 900 to 1100 sccm, more preferably 950 to 1050 sccm, and more preferably 1000 sccm. The time is preferably 3800 to 4200 s, more preferably 3900 to 4100 s, and more preferably 4000 s.

[0041] In the present invention, the method for preparing a back contact passivated battery by three-layer tunneling and poly comprises the following steps: opening the furnace door at normal pressure, entering a boat, vacuuming once, vacuuming twice, picking up leaks once, heating, constant temperature once, oxidizing at normal pressure, sealing the tank, vacuuming three times, cooling, purging once, constant temperature twice, picking up leaks twice, constant pressure, diffusion deposition, vacuuming four times, purging twice, breaking vacuum, and exiting the boat;

[0042] The above steps are completed to complete one layer of tunneling and poly. Three layers of tunneling and poly are completed by repeating the above steps three times. The first normal pressure oxidation is to prepare the first layer of tunneling, and the first diffusion deposition is to prepare the first layer of poly; the second normal pressure oxidation is to prepare the second layer of tunneling, and the second diffusion deposition is to prepare the second layer of poly; the third normal pressure oxidation is to prepare the third layer of tunneling, and the third diffusion deposition is to prepare the third layer of poly.

[0043] In the present invention, the time for entering the boat is preferably 60 to 90 s, more preferably 70 to 80 s, and more preferably 75 s; the first vacuuming is preferably to a vacuum degree of 0 to 700 mtorr, more preferably 200 to 400 mtorr, and the time for the first vacuuming is preferably 50 s; the second vacuuming is preferably to a vacuum degree of 0 to 10 mtorr, more preferably 3 to 7 mtorr, and the time for the second vacuuming is preferably 200 to 300 s, more preferably 220 to 280 s, and more preferably 250 s; the leakage rate of the first leak detection is preferably ≤25 mtorr, and the time for the first leak detection is preferably 30 to 60 s, more preferably 40 to 50 s.

[0044] In the present invention, the time for heating to a constant temperature is preferably 300 to 600 s, more preferably 400 to 500 s, more preferably 450 s, the temperature for a constant temperature is preferably 580 to 650° C., more preferably 600 to 630° C., more preferably 610 to 620° C., and the time is preferably 300 to 600 s, more preferably 400 to 500 s, more preferably 450 s;

[0045] The temperature of the steaming pot is preferably 580 to 650° C., more preferably 600 to 630° C., more preferably 610 to 620° C., and the time is preferably 600 to 1000 s, more preferably 700 to 900 s, more preferably 800 s.

[0046] In the present invention, the three vacuumings are preferably performed until the gas in the tube is 0 mtorr; the temperature is preferably lowered to 500-550°C, more preferably to 520-530°C, and the cooling time is preferably 3000-6000s, more preferably 4000-5000s, and more preferably 4500s;

[0047] The temperature of the secondary thermostat is preferably 500-550°C, more preferably 520-530°C, and the time is preferably 300-600s, more preferably 400-500s, and 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. The time for the secondary leak detection is preferably 30 to 60 s, more preferably 40 to 50 s, and more preferably 45 s. The temperature is preferably 500 to 550°C, and more preferably 520 to 530°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] In the present invention, after poly is prepared by diffusion deposition, boron diffusion is performed. The boron diffusion preferably includes doping and push-junction oxidation. The doping temperature is preferably 825-845°C, further preferably 830-840°C, and more preferably 835°C. The pressure is preferably 130-150 mbar, further preferably 135-145 mbar, and more preferably 140 mbar. The push-junction oxidation temperature is preferably 940-960°C, further preferably 945-955°C, and more preferably 950°C. The pressure is preferably 390-410 mbar, further preferably 395-405 mbar, and more preferably 400 mbar. Boron diffusion achieves in-situ doping with high surface concentration, effectively prevents internal diffusion, and can also achieve lower ohmic contact, thereby ultimately achieving high conversion efficiency of back-contact batteries.

[0051] In the present invention, the vacuum is pumped four times to 0-10 mtorr, the temperature of the four vacuum pumpings is preferably 580-600°C, more preferably 590°C, the time is preferably 200-300s, more preferably 220-280s, and more preferably 250s;

[0052] Nitrogen is introduced into the primary purge and the secondary purge until the tube is completely filled with nitrogen. The time for the primary purge and the secondary purge is independently preferably 30 to 60 seconds, and more preferably 40 to 50 seconds. The temperature of the primary purge is preferably 500 to 550°C, and more preferably 520 to 530°C. The temperature of the secondary purge is preferably 580 to 600°C, and more preferably 590°C.

[0053] 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.

[0054] In the embodiment, an N-type C-Si silicon wafer is used as a substrate.

[0055] Example 1

[0056] The method for preparing a back contact passivated cell by three-layer tunneling and poly comprises the following steps:

[0057] S01: Start at normal pressure and open the furnace door;

[0058] S02: Enter the boat, the time is set to 80s;

[0059] S03: vacuum to 200 mtorr at normal pressure, vacuum time 50 s;

[0060] S04: Secondary vacuuming to 2mtorr, vacuuming time 250s;

[0061] S05: Check for leaks after secondary vacuuming, ensuring the leak rate is within 25mtorr, and the leak checking time is 40s;

[0062] S06: heating to process temperature 610°C, heating time 400s;

[0063] S07: constant temperature 610℃, constant temperature time 400s;

[0064] S08: Preparation of SiO by atmospheric oxidation (first layer tunneling oxygen deposition) 2 Layer: pressure 760torr, oxidation temperature 610℃, oxygen flow rate 10000sccm, oxidation time 600s, first layer tunneling SiO 2 The thickness of the layer is 0.8 nm;

[0065] S09: 610℃ jar-warming for 800s;

[0066] S10: Evacuate at 610°C until the gas in the tube is 0 mtorr;

[0067] S11: Cool down to 520°C, cooling time 4000s;

[0068] S12: N2 at 520℃ 2 Purge the furnace tube to make sure there is no other gas in the tube. The purge time is 45 seconds.

[0069] S13: constant temperature 520℃, stabilization time 400s;

[0070] S14: 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 40 seconds, and the temperature is 520°C;

[0071] S15: 200 mtorr pressure for 450 s to better deposit poly;

[0072] S16: Diffusion deposition (first layer of poly) using low pressure chemical vapor deposition: temperature 550°C, pressure 180mtorr, furnace mouth SiH 4 The flow rate is 350sccm, the furnace tail SiH 4 The flow rate is 1200sccm, SiH4 The flow time is 3000s; the thickness of the first poly layer is 120nm;

[0073] After the poly is prepared by diffusion deposition, boron diffusion is performed, and the boron diffusion is doped at a pressure of 140mbar and 835℃, and the junction is pushed and oxidized at a pressure of 400mbar and 950℃;

[0074] S17: At a temperature of 590°C, evacuate to 2 mtorr for 250 seconds;

[0075] S18: N2 at 590℃ 2 Purge the furnace tube to make sure there is no other gas in the tube. The purge time is 45 seconds.

[0076] S19: Charge N 2 Bring the internal pressure to normal pressure;

[0077] S20: 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 layer, only steps S08 and S16 are changed, and the other conditions are the same as the first time; S08: atmospheric pressure oxidation (second tunneling oxygen deposition) to prepare SiO 2 Layer: pressure 760torr, oxidation temperature 610℃, oxygen flow rate 15000sccm, oxidation time 1000s, second layer tunneling SiO 2 The thickness of the layer is 0.8 nm;

[0079] S16: Diffusion deposition (second layer of poly) using low pressure chemical vapor deposition: temperature 550°C, pressure 180mtorr, furnace mouth SiH 4 The flow rate is 310sccm, the furnace tail SiH 4 The flow rate is 1000sccm, SiH 4 The injection time is 2600s; the thickness of the second poly layer is 100nm, and the boron diffusion process remains unchanged;

[0080] In the third layer of tunneling and poly, only steps S08 and S16 are changed, and the other conditions are the same as the first time; S08: atmospheric pressure oxidation (third layer of tunneling oxygen deposition) to prepare SiO 2 Layer: pressure 760torr, oxidation temperature 610℃, oxygen flow rate 19000sccm, oxidation time 1000s, third layer tunneling SiO 2 The thickness of the layer is 1 nm;

[0081] S16: Diffusion deposition (third layer poly) using low pressure chemical vapor deposition: temperature 550°C, pressure 180mtorr, furnace mouth SiH 4The flow rate is 310sccm, the furnace tail SiH 4 The flow rate is 1000sccm, SiH 4 The injection time is 4000s; the thickness of the third poly layer is 180nm, and the boron diffusion process remains unchanged.

[0082] Example 2

[0083] The method for preparing a back contact passivated cell by three-layer tunneling and poly comprises the following steps:

[0084] S01: Start at normal pressure and open the furnace door;

[0085] S02: Enter the boat, the time is set to 60s;

[0086] S03: vacuum to 700 mtorr at normal pressure, vacuum time 50 s;

[0087] S04: Secondary vacuuming to 10 mtorr, vacuuming time 300 s;

[0088] S05: Check for leaks after secondary vacuuming, ensuring the leak rate is within 25mtorr, and the leak checking time is 30s;

[0089] S06: heating to process temperature 580°C, heating time 300s;

[0090] S07: constant temperature 580℃, constant temperature time 300s;

[0091] S08: Preparation of SiO by atmospheric oxidation (first layer tunneling oxygen deposition) 2 Layer: pressure 760torr, oxidation temperature 600℃, oxygen flow 9500sccm, oxidation time 580s, first layer tunneling SiO 2 The thickness of the layer is 0.8 nm;

[0092] S09: 580℃ jar-warming for 1000s;

[0093] S10: Evacuate at 580°C until the gas in the tube is 0 mtorr;

[0094] S11: Cool down to 500°C, cooling time 3000s;

[0095] S12: N2 at 500℃ 2 Purge the furnace tube to make sure there is no other gas in the tube. The purge time is 30 seconds.

[0096] S13: constant temperature 500°C, stabilization time 300s;

[0097] S14: 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 30 seconds, and the temperature is 500°C;

[0098] S15: 200 mtorr pressure for 300 s to better deposit poly;

[0099] S16: Diffusion deposition by low pressure chemical vapor deposition (first layer of poly): In the first tunneling poly layer, the temperature is 540°C, the pressure is 175mtorr, and the furnace port SiH 4 The flow rate is 345sccm, and the furnace tail SiH 4 The flow rate is 1150sccm, SiH 4 The injection time is 2900s; the thickness of the first poly layer is 122nm;

[0100] After the poly is prepared by diffusion deposition, boron diffusion is performed, and the boron diffusion is doped at a pressure of 135mbar and 830℃, and the junction is pushed and oxidized at a pressure of 390mbar and 945℃;

[0101] S17: At a temperature of 580°C, evacuate to 0 mtorr for 300 seconds;

[0102] S18: N2 at 580℃ 2 Purge the furnace tube to make sure there is no other gas in the tube. The purge time is 60s.

[0103] S19: Charge N 2 Bring the internal pressure to normal pressure;

[0104] S20: 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.

[0105] In the second tunneling and poly layer, only steps S08 and S16 are changed, and the other conditions are the same as the first time; S08: atmospheric pressure oxidation (second tunneling oxygen deposition) to prepare SiO 2 Layer: pressure 760torr, oxidation temperature 600℃, oxygen flow rate 14500sccm, oxidation time 950s, second layer tunneling SiO 2 The thickness of the layer is 0.75 nm;

[0106] S16: Diffusion deposition (second layer of poly) using low pressure chemical vapor deposition: temperature 540°C, pressure 175mtorr, furnace mouth SiH 4 The flow rate is 305sccm, the furnace tail SiH 4 The flow rate is 950sccm, SiH 4 The injection time is 2500s; the thickness of the second poly layer is 102nm, and the boron diffusion process remains unchanged;

[0107] In the third layer of tunneling and poly, only steps S08 and S16 are changed, and the other conditions are the same as the first time; S08: atmospheric pressure oxidation (third layer of tunneling oxygen deposition) to prepare SiO 2 Layer: pressure 760torr, oxidation temperature 600℃, oxygen flow rate 18500sccm, oxidation time 950s, third layer tunneling SiO 2 The thickness of the layer is 0.95 nm;

[0108] S16: Diffusion deposition (third layer poly) using low pressure chemical vapor deposition: temperature 540°C, pressure 175mtorr, furnace mouth SiH 4 The flow rate is 305sccm, and the furnace tail SiH 4 The flow rate is 950sccm, SiH 4 The injection time is 3900s; the thickness of the third poly layer is 185nm, and the boron diffusion process remains unchanged.

[0109] Example 3

[0110] The method for preparing a back contact passivated cell by three-layer tunneling and poly comprises the following steps:

[0111] S01: Start at normal pressure and open the furnace door;

[0112] S02: Enter the boat, the time is set to 90s;

[0113] S03: vacuum to 100 mtorr at normal pressure, vacuum time 50 s;

[0114] S04: vacuumize twice to 0 mtorr, vacuum time 200 s;

[0115] S05: Check for leaks after secondary vacuuming, ensuring the leak rate is within 25mtorr, and the leak checking time is 60s;

[0116] S06: heating to process temperature 650°C, heating time 600s;

[0117] S07: constant temperature 650℃, constant temperature time 600s;

[0118] S08: Preparation of SiO by atmospheric oxidation (first layer tunneling oxygen deposition) 2 Layer: pressure 760torr, oxidation temperature 620℃, oxygen flow rate 10500sccm, oxidation time 620s, first layer tunneling SiO 2 The thickness of the layer is 0.85 nm;

[0119] S09: 650℃ jarring for 600s;

[0120] S10: Evacuate at 650°C until the gas in the tube is 0 mtorr;

[0121] S11: Cooling to 550°C, cooling time 6000s;

[0122] S12: N2 at 550℃ 2 Purge the furnace tube to make sure there is no other gas in the tube. The purge time is 60s.

[0123] S13: constant temperature 550℃, stabilization time 600s;

[0124] S14: 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 550°C;

[0125] S15: 200 mtorr pressure for 600 s to better deposit poly;

[0126] S16: Diffusion deposition (first layer of poly) using low pressure chemical vapor deposition: temperature 560°C, pressure 185mtorr, furnace mouth SiH 4 The flow rate is 355sccm, the furnace tail SiH 4 The flow rate is 1250sccm, SiH 4 The injection time is 3100s; the thickness of the first poly layer is 115nm;

[0127] After the poly is prepared by diffusion deposition, boron diffusion is performed, and the boron diffusion is doped at a pressure of 145mbar and 840℃, and the junction is pushed and oxidized at a pressure of 410mbar and 955℃;

[0128] S17: at 600°C, evacuate to 10 mtorr for 200 s;

[0129] S18: N2 at 600℃ 2 Purge the furnace tube to make sure there is no other gas in the tube. The purge time is 30 seconds.

[0130] S19: Charge N 2 Bring the internal pressure to normal pressure;

[0131] S20: 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.

[0132] In the second tunneling and poly layer, only steps S08 and S16 are changed, and the other conditions are the same as the first time; S08: atmospheric pressure oxidation (second tunneling oxygen deposition) to prepare SiO 2 Layer: pressure 760torr, oxidation temperature 620℃, oxygen flow rate 15500sccm, oxidation time 1050s, second layer tunneling SiO2 The thickness of the layer is 0.85 nm;

[0133] S16: Diffusion deposition (second layer of poly) using low pressure chemical vapor deposition: temperature 560°C, pressure 185mtorr, furnace mouth SiH 4 The flow rate is 315sccm, the furnace tail SiH 4 The flow rate is 1050sccm, SiH 4 The injection time is 2700s; the thickness of the second poly layer is 98nm, and the boron diffusion process remains unchanged;

[0134] In the third layer of tunneling and poly, only steps S08 and S16 are changed, and the other conditions are the same as the first time; S08: atmospheric pressure oxidation (third layer of tunneling oxygen deposition) to prepare SiO 2 Layer: pressure 760torr, oxidation temperature 620℃, oxygen flow rate 19500sccm, oxidation time 1050s, the third layer tunneling SiO 2 The thickness of the layer is 1.05 nm;

[0135] S16: Diffusion deposition (third layer poly) using low pressure chemical vapor deposition: temperature 560°C, pressure 150mtorr, furnace mouth SiH 4 The flow rate is 315sccm, the furnace tail SiH 4 The flow rate is 1050sccm, SiH 4 The injection time is 4100s; the thickness of the third poly layer is 175nm, and the boron diffusion process remains unchanged.

[0136] 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 passivated battery using three-layer tunneling and poly, characterized in that: The thickness of the first tunneling layer is 0.75-0.85 nm, and the thickness of the first poly layer is 115-125 nm; The thickness of the second tunneling layer is 0.75-0.85 nm, and the thickness of the second poly layer is 95-105 nm; The thickness of the third tunneling layer is 0.95-1.05 nm, and the thickness of the third poly layer is 170-190 nm.

2. The method according to claim 1, characterized in that: In the preparation of the three-layer tunneling, the temperature is independent of 590-630°C, and the pressure is independent of 750-770 torr; in the preparation of the poly layer, the temperature is independent of 530-570°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 9000-11000sccm, the time is 550-650s, in the preparation of the first layer of poly, the SiH4 flow rate at the furnace mouth is 340-360sccm, the SiH4 flow rate at the furnace tail is 1100-1300sccm, and the time is 2800-3200s; In the preparation of the second layer of tunneling, the oxygen flow rate is 14000-16000sccm, the time is 900-1100s, and in the preparation of the second layer of poly, the SiH4 flow rate at the furnace mouth is 300-320sccm, the SiH4 flow rate at the furnace tail is 900-1100sccm, and the time is 2400-2800s; In the preparation of the third layer of tunneling, the oxygen flow rate is 18000-20000sccm, and the time is 900-1100s. In the preparation of the third layer of poly, the SiH4 flow rate at the furnace mouth is 300-320sccm, and the SiH4 flow rate at the furnace tail is 900-1100sccm, and the time is 3800-4200s.

4. The method according to claim 3, characterized in that The method for preparing a back contact passivated battery by three-layer tunneling and poly comprises the following steps: opening the furnace door at normal pressure, entering a boat, vacuuming once, vacuuming twice, checking for leaks once, heating, constant temperature once, oxidation at normal pressure, sealing the tank, vacuuming three times, cooling, purging once, constant temperature twice, checking for leaks twice, constant pressure, diffusion deposition, vacuuming four times, purging twice, breaking vacuum, and exiting the boat; The above steps are completed to complete one layer of tunneling and poly. Three layers of tunneling and poly are completed by repeating the above steps three times. The first normal pressure oxidation is to prepare the first layer of tunneling, and the first diffusion deposition is to prepare the first layer of poly; the second normal pressure oxidation is to prepare the second layer of tunneling, and the second diffusion deposition is to prepare the second layer of poly; the third normal pressure oxidation is to prepare the third layer of tunneling, and the third diffusion deposition is to prepare the third 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 to 700 mtorr, and the time for the first vacuum is 50 seconds; the vacuum is pumped twice to a vacuum degree of 0 to 10 mtorr, and the time for the second vacuum is 200 to 300 seconds; the leakage rate of the first leak detection is ≤25 mtorr, and the time for the first leak detection is 30 to 60 seconds.

6. The method according to claim 4 or 5, characterized in that: The time for heating to a constant temperature is 300-600s, the temperature of the constant temperature is 580-650°C, and the time is 300-600s; The temperature of the can is 580-650°C and the time is 600-1000s.

7. The method according to claim 6, characterized in that Evacuate the tube three times until the gas in the tube is 0 mtorr; cool down to 500-550°C for 3000-6000 seconds; The temperature of the secondary constant temperature is 500-550°C and the 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 500-550℃.

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, boron diffusion is performed. Boron diffusion includes doping and push-junction oxidation. The doping temperature is 825-845°C and the pressure is 130-150 mbar. The push-junction oxidation temperature is 940-960°C and the pressure is 390-410 mbar.

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

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