CN115799383A - Silicon wafer diffusion method and solar cell - Google Patents
Silicon wafer diffusion method and solar cell Download PDFInfo
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- CN115799383A CN115799383A CN202211354790.4A CN202211354790A CN115799383A CN 115799383 A CN115799383 A CN 115799383A CN 202211354790 A CN202211354790 A CN 202211354790A CN 115799383 A CN115799383 A CN 115799383A
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- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 178
- 239000010703 silicon Substances 0.000 title claims abstract description 178
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 177
- 238000009792 diffusion process Methods 0.000 title claims abstract description 82
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 110
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 109
- 239000011574 phosphorus Substances 0.000 claims abstract description 108
- 230000008021 deposition Effects 0.000 claims abstract description 84
- 239000011521 glass Substances 0.000 claims abstract description 24
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 143
- 229910052757 nitrogen Inorganic materials 0.000 claims description 70
- 230000003647 oxidation Effects 0.000 claims description 64
- 238000007254 oxidation reaction Methods 0.000 claims description 64
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 40
- 239000001301 oxygen Substances 0.000 claims description 40
- 229910052760 oxygen Inorganic materials 0.000 claims description 40
- 239000007789 gas Substances 0.000 claims description 20
- 238000000034 method Methods 0.000 claims description 19
- 239000005360 phosphosilicate glass Substances 0.000 claims description 8
- 235000012431 wafers Nutrition 0.000 claims 18
- 238000005215 recombination Methods 0.000 abstract description 8
- 230000006798 recombination Effects 0.000 abstract description 8
- 125000004437 phosphorous atom Chemical group 0.000 abstract description 7
- 229910021419 crystalline silicon Inorganic materials 0.000 abstract description 5
- 238000000151 deposition Methods 0.000 description 73
- 239000010410 layer Substances 0.000 description 31
- 230000000052 comparative effect Effects 0.000 description 13
- 238000006243 chemical reaction Methods 0.000 description 8
- 238000001816 cooling Methods 0.000 description 7
- 238000011056 performance test Methods 0.000 description 7
- 239000000758 substrate Substances 0.000 description 6
- 238000005137 deposition process Methods 0.000 description 5
- 239000002344 surface layer Substances 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 125000004429 atom Chemical group 0.000 description 3
- 229910001873 dinitrogen Inorganic materials 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- HIVGXUNKSAJJDN-UHFFFAOYSA-N [Si].[P] Chemical compound [Si].[P] HIVGXUNKSAJJDN-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- XHXFXVLFKHQFAL-UHFFFAOYSA-N phosphoryl trichloride Chemical compound ClP(Cl)(Cl)=O XHXFXVLFKHQFAL-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 239000002019 doping agent Substances 0.000 description 1
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 239000011241 protective layer Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 150000003376 silicon Chemical class 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/547—Monocrystalline silicon PV cells
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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Abstract
The invention provides a silicon wafer diffusion method and a solar cell, wherein the silicon wafer diffusion method comprises the following steps: carrying out first phosphorus deposition on the silicon wafer in a first atmosphere; carrying out laser doping on the silicon wafer subjected to the first phosphorus deposition; removing the phosphorosilicate glass layer on the surface of the laser-doped silicon wafer; carrying out second phosphorus deposition on the silicon wafer with the phosphorosilicate glass layer removed in a second atmosphere; and carrying out junction pushing treatment on the silicon wafer subjected to the second phosphorus deposition. The diffusion method of the silicon wafer can effectively reduce the loss of phosphorus atoms in the surface diffusion of the silicon wafer, improve the effective doping concentration and the effective doping depth of the silicon wafer, and reduce the surface recombination, thereby prolonging the minority carrier lifetime of the diffused silicon wafer and improving the performance of a crystalline silicon solar cell adopting the silicon wafer.
Description
Technical Field
The invention relates to the technical field of solar cells, in particular to a silicon wafer diffusion method and a solar cell.
Background
In a crystalline silicon solar cell, a silicon wafer needs to be subjected to diffusion treatment so as to reduce the doping concentration on the surface of the silicon wafer and improve the doping concentration inside the silicon wafer, thereby improving the light conversion efficiency of the solar cell and reducing the attenuation rate of the solar cell.
However, the doped silicon wafer obtained by the conventional diffusion doping process has the problems of low effective doping concentration, shallow effective doping depth, serious surface recombination and the like, so that the minority carrier lifetime of the doped silicon wafer is short, and the performance of the crystalline silicon solar cell is influenced.
Therefore, how to develop a silicon wafer diffusion process capable of effectively increasing the doping depth and doping concentration of a silicon wafer and reducing surface recombination so as to improve the performance of a solar cell has become one of the research hotspots in the field.
Disclosure of Invention
Accordingly, there is a need for a method of diffusing a silicon wafer and a solar cell that can increase the doping depth and doping concentration and reduce surface recombination.
According to a first aspect of the present invention, there is provided a diffusion method for a silicon wafer, comprising the steps of:
carrying out first phosphorus deposition on a silicon wafer in a first atmosphere;
carrying out laser doping on the silicon wafer subjected to the first phosphorus deposition;
removing the phosphosilicate glass layer on the surface of the silicon wafer after laser doping;
carrying out second phosphorus deposition on the silicon wafer with the phosphorosilicate glass layer removed in a second atmosphere; and
and carrying out junction pushing treatment on the silicon wafer subjected to the second phosphorus deposition.
In some embodiments, the flow rate of the small nitrogen in the first atmosphere is 1000sccm to 1500sccm, the flow rate of the oxygen is 500sccm to 1000sccm, and the flow rate of the large nitrogen is 500sccm to 1000sccm.
In some embodiments, the first phosphorus is deposited for 400s to 600s at 780 ℃ to 790 ℃.
In some embodiments, the laser energy of the laser doping is 15 kJ-20 kJ, and the depth of the laser doping is 20 nm-50 nm.
In some embodiments, the flow rate of the small nitrogen in the second atmosphere is 300sccm to 500sccm, the flow rate of the oxygen is 300sccm to 600sccm, and the flow rate of the large nitrogen is 500sccm to 1500sccm.
In some of these embodiments, the second phosphorus is deposited for a time period of 50s to 100s at a temperature of 740 ℃ to 750 ℃.
In some embodiments, the temperature of the push-bonding treatment is 850-860 ℃ and the time is 5-15 min.
In some embodiments, before the first phosphorus deposition of the silicon wafer in the first atmosphere, the method further comprises the following steps:
carrying out first oxidation treatment on the silicon wafer in a third atmosphere;
optionally, the oxygen flow rate in the third atmosphere is 500sccm to 1500sccm, and the large nitrogen flow rate is 500sccm to 1500sccm;
optionally, the temperature of the first oxidation treatment is 750-780 ℃, the time is 3-10 min, and the gas pressure is 90-110 mbar.
In some embodiments, after performing the junction pushing treatment on the silicon wafer after the second phosphorus deposition, the method further comprises the following steps:
carrying out second oxidation treatment on the silicon wafer in a fourth atmosphere;
optionally, the oxygen flow rate in the fourth atmosphere is 500sccm to 1500sccm, and the large nitrogen flow rate is 500sccm to 1500sccm;
optionally, the temperature of the second oxidation treatment is 740-800 ℃, the time is 3-10 min, and the gas pressure is 70-150 mbar.
According to a second aspect of the present invention, there is provided a solar cell employing a silicon wafer produced by the diffusion method of the first aspect of the present invention.
Compared with the prior art, the invention has the following beneficial effects:
through carrying out first phosphorus deposit, laser doping, getting rid of phosphosilicate glass layer, second phosphorus deposit and push away the knot to the silicon chip in proper order, through first phosphorus deposit, laser doping, get rid of phosphosilicate glass layer, the mode that second phosphorus deposit and push away the knot and combine together, can reduce the loss of phosphorus atom when the silicon chip top layer diffuses effectively, promote the effective doping concentration and the effective doping degree of depth of silicon chip, and can reduce the surface recombination to can increase the minority carrier lifetime of the silicon chip after the diffusion, and then improve the performance of the crystal silicon solar cell who adopts this silicon chip.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings, which illustrate embodiments of the present invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
In the present invention, "macronitrogen" means pure nitrogen gas; "Small nitrogen" refers to nitrogen gas carrying a phosphorus source (e.g., phosphorus oxychloride). Small nitrogen is typically obtained by passing nitrogen gas through a phosphorus source liquid. In the process of phosphorus deposition, small nitrogen is introduced to provide a phosphorus source so that phosphorus can be deposited on the surface of the silicon wafer; the large nitrogen mainly plays a role in protection as a protective gas.
The traditional preparation process for depositing a phosphorus source on a silicon wafer and forming a doped silicon wafer by diffusion has the problems of low effective doping concentration, shallow effective doping depth, serious surface recombination and the like of the silicon wafer, so that the doped silicon wafer has short minority carrier lifetime and has great influence on the performance of a crystalline silicon solar cell.
In order to solve the above problem, an embodiment of the present invention provides a method for diffusing a silicon wafer, including steps S1 to S7:
step S1: subjecting the silicon wafer to a first oxidation treatment in a third atmosphere
Firstly, feeding the silicon wafer subjected to texturing treatment into a diffusion furnace, raising the furnace temperature, and checking whether a furnace tube of the diffusion furnace leaks gas or not; and then introducing a third atmosphere into the diffusion furnace to carry out first oxidation treatment on the silicon wafer.
In some embodiments, the flow rate of oxygen in the third atmosphere is 500sccm to 1500sccm, and the flow rate of the big nitrogen is 500sccm to 1500sccm; the temperature of the first oxidation treatment is 750-780 ℃, the time is 3-10 min, and the gas pressure is 90-110 mbar.
And oxidizing the silicon wafer under the third atmosphere condition and the first oxidation treatment process condition to form an oxide layer on the surface of the silicon wafer, so that the concentration of phosphorus doped on the surface of the silicon wafer after the subsequent first phosphorus deposition is reduced, and the uniformity of phosphorus diffusion is improved.
It is understood that the flow rate of oxygen in the third atmosphere can be, but is not limited to, 500sccm, 600sccm, 700sccm, 800sccm, 900sccm, 1000sccm, 1100sccm, 1200sccm, 1300sccm, 1400sccm, 1500sccm; the mass nitrogen flow can be, but is not limited to, 500sccm, 600sccm, 700sccm, 800sccm, 900sccm, 1000sccm, 1100sccm, 1200sccm, 1300sccm, 1400sccm, 1500sccm; the temperature of the first oxidation treatment can be, but is not limited to, 750 ℃, 755 ℃, 760 ℃, 765 ℃, 770 ℃, 775 ℃ and 780 ℃; the time of the first oxidation treatment can be, but is not limited to, 3min, 4min, 5min, 6min, 7min, 8min, 9min, 10min; the gas pressure of the first oxidation process may be, but is not limited to, 90mbar, 95mbar, 100mbar, 105mbar, 110mbar.
Step S2: carrying out first phosphorus deposition on a silicon wafer in a first atmosphere
The first phosphorus deposition treatment is performed on the silicon wafer after the first oxidation treatment, so that a phosphorus source can be deposited on the surface of the silicon wafer.
In some embodiments, the flow rate of the small nitrogen in the first atmosphere is 1000sccm to 1500sccm, the flow rate of the oxygen is 500sccm to 1000sccm, and the flow rate of the large nitrogen is 500sccm to 1000sccm; the time of the first phosphorus deposition is 400-600 s, and the temperature of the first phosphorus deposition is 780-790 ℃.
Thus, the introduction amount of the phosphorus source can be controlled by controlling the flow of the small nitrogen in the first atmosphere; the amount of the phosphorus source deposited on the surface of the silicon wafer in the first phosphorus deposition process can be controlled by regulating and controlling the small nitrogen flow, the first phosphorus deposition time and the temperature.
It is understood that in some embodiments, the flow rate of the small nitrogen in the first atmosphere can be, but is not limited to, 1000sccm, 1100sccm, 1200sccm, 1300sccm, 1400sccm, 1500sccm; the flow rate of oxygen can be, but is not limited to, 500sccm, 600sccm, 700sccm, 800sccm, 900sccm, 1000sccm; the flow rate of the large nitrogen can be, but is not limited to, 500sccm, 600sccm, 700sccm, 800sccm, 900sccm, 1000sccm; the time of the first phosphorus deposition may be, but is not limited to, 400s, 420s, 440s, 460s, 480s, 500s, 520s, 540s, 560s, 580s, 600s; the temperature of the first phosphorus deposition may be, but is not limited to, 780 ℃, 782 ℃, 784 ℃, 786 ℃, 788 ℃ and 790 ℃.
And step S3: performing laser doping on the silicon wafer after the first phosphorus deposition
After the first phosphorus deposition is finished, the furnace door is opened after the diffusion furnace is cooled, the silicon wafer is moved out of the diffusion furnace, and then laser doping treatment is carried out on the silicon wafer. Through laser doping treatment, a phosphosilicate glass (PSG) layer deposited on the surface of the silicon wafer can be pushed towards the interior of the silicon wafer through energy generated by laser, and phosphorus atoms on the surface of the silicon wafer are sent to the position below the surface layer of the silicon wafer, so that the loss of the phosphorus atoms in the surface layer of the silicon wafer during diffusion is reduced, and the effective doping concentration and the doping depth of the silicon wafer are improved.
In some of these embodiments, the laser energy used in the laser doping step is between 15kJ and 20kJ. Under the condition of the laser doping process, the phosphorus atoms on the surface of the silicon wafer can be effectively pushed to the inside of the silicon wafer by 20-50 nm. It is understood that the laser energy used for laser doping may be, but is not limited to, 15kJ, 16kJ, 17kJ, 18kJ, 19kJ, 20kJ.
And step S4: removing the phosphorosilicate glass layer on the surface of the laser-doped silicon wafer
After the silicon wafer is subjected to laser doping treatment, the phosphorosilicate glass layer on the surface of the silicon wafer is removed. By removing the phosphorosilicate glass layer on the surface of the silicon wafer, more phosphorus sources can enter the interior of the silicon wafer in the subsequent second phosphorus deposition and junction pushing steps, the energy required by phosphorus atoms to be pushed to a deeper part of the silicon wafer is reduced, and the effective doping depth of the silicon wafer is improved; meanwhile, the concentration of the phosphorus source on the surface of the silicon wafer is reduced, and the surface recombination is reduced.
In some embodiments, the phosphorosilicate glass layer with the thickness of 3nm to 6nm on the surface of the silicon wafer is removed by an HF acid etching method.
Step S5: carrying out second phosphorus deposition on the silicon wafer without the phosphorosilicate glass layer in a second atmosphere
After the phosphorosilicate glass layer on the surface of the silicon wafer is removed, the silicon wafer is sent into a diffusion furnace, a second atmosphere is introduced, the temperature is raised, and second phosphorus deposition treatment is continuously carried out. And a certain amount of phosphorus source can be formed on the surface of the silicon wafer through secondary phosphorus deposition, and the effective doping concentration and the doping depth of the silicon wafer can be further improved by combining the subsequent junction pushing step. By combining the first phosphorus deposition and the second phosphorus deposition, the phosphorus doping in the silicon wafer can be more uniform.
In some embodiments, the flow rate of the small nitrogen in the second atmosphere is 300sccm to 500sccm, the flow rate of the oxygen is 300sccm to 600sccm, and the flow rate of the large nitrogen is 500sccm to 1500sccm. The second phosphorus deposition time is 50 s-100 s, and the temperature is 740-750 ℃. In this way, the small nitrogen flow in the second phosphorus deposition process is lower than that in the first phosphorus deposition process, the deposition time and temperature are also lower than those in the first phosphorus deposition process, and a smaller amount of phosphorus source can be formed on the surface of the silicon wafer after the phosphorus-silicon glass layer is removed in a deposition mode to supplement the first phosphorus deposition process.
It is understood that the flow rate of the small nitrogen in the second atmosphere can be, but is not limited to, 300sccm, 320sccm, 340sccm, 360sccm, 380sccm, 400sccm, 420sccm, 440sccm, 460sccm, 480sccm, 500sccm; the oxygen flow rate can be, but is not limited to, 300sccm, 350sccm, 400sccm, 450sccm, 500sccm, 550sccm, 600sccm; the mass nitrogen flow can be, but is not limited to, 500sccm, 600sccm, 700sccm, 800sccm, 900sccm, 1000sccm, 1100sccm, 1200sccm, 1300sccm, 1400sccm, 1500sccm. The time for the second phosphorus deposition may be, but is not limited to, 50s, 60s, 70s, 80s, 90s, 100s; the temperature of the second phosphorus deposition can be, but is not limited to 740 deg.C, 742 deg.C, 744 deg.C, 746 deg.C, 748 deg.C, 750 deg.C.
Step S6: performing junction pushing treatment on the silicon wafer subjected to the second phosphorus deposition
After the second phosphorus deposition, the invention continues to carry out the junction pushing treatment on the silicon wafer at high temperature. Through junction pushing treatment, phosphorus sources gathered on the surface layer and inside the silicon wafer can enter deeper inside the silicon wafer, so that the effective doping depth and doping concentration of the silicon wafer are further improved, and the silicon wafer can obtain deeper junction depth.
In some embodiments, the temperature of the knot pushing treatment is 850-860 ℃, and the time of the knot pushing treatment is 5-15 min. Under the conditions of the push junction treatment process, the silicon wafer can obtain enough doping concentration and doping depth.
It is understood that the temperature of the knotting process can be, but is not limited to, 850 deg.C, 851 deg.C, 852 deg.C, 853 deg.C, 854 deg.C, 855 deg.C, 856 deg.C, 857 deg.C, 858 deg.C, 859 deg.C, 860 deg.C; the time of the knot pushing treatment can be, but is not limited to, 5min, 6min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, 14min, 15min.
Step S7: carrying out second oxidation treatment on the silicon wafer after the push junction treatment in a fourth atmosphere
After the junction pushing treatment is finished, the silicon wafer is placed in a fourth atmosphere, and second oxidation treatment is carried out on the silicon wafer, so that an oxidation protective layer is formed on the surface of the silicon wafer.
In some embodiments, the oxygen flow rate in the fourth atmosphere is 500sccm to 1500sccm, and the large nitrogen flow rate is 500sccm to 1500sccm. The temperature of the second oxidation treatment is 740-800 ℃, the time of the second oxidation treatment is 3-10 min, and the gas pressure of the second oxidation treatment is 70-150 mbar.
It is understood that the flow rate of oxygen in the fourth atmosphere can be, but not limited to, 500sccm, 600sccm, 700sccm, 800sccm, 900sccm, 1000sccm, 1100sccm, 1200sccm, 1300sccm, 1400sccm, 1500sccm; the flow rate of the large nitrogen in the fourth atmosphere can be, but is not limited to, 500sccm, 600sccm, 700sccm, 800sccm, 900sccm, 1000sccm, 1100sccm, 1200sccm, 1300sccm, 1400sccm, 1500sccm; the temperature of the second oxidation treatment may be, but is not limited to 740 ℃, 750 ℃, 760 ℃, 770 ℃, 780 ℃, 790 ℃, 800 ℃; the time of the second oxidation treatment can be, but is not limited to, 3min, 4min, 5min, 6min, 7min, 8min, 9min, 10min; the gas pressure of the second oxidation treatment may be, but is not limited to, 70mbar, 80mbar, 90mbar, 100mbar, 110mbar, 120mbar, 130mbar, 140mbar, 150mbar.
And after the second oxidation treatment is finished, adjusting the pressure in the diffusion furnace to atmospheric pressure, opening the furnace door after cooling, and removing the silicon wafer out of the diffusion furnace.
Generally speaking, the silicon wafer diffusion method of the invention sequentially carries out first phosphorus deposition, laser doping, phosphorosilicate glass layer removal, second phosphorus deposition and junction pushing on the silicon wafer, and through the mode of combining the first phosphorus deposition, the laser doping, the phosphorosilicate glass layer removal, the second phosphorus deposition and the junction pushing, the loss of phosphorus atoms in the surface layer of the silicon wafer during diffusion can be effectively reduced, the effective doping concentration and the effective doping depth of the silicon wafer can be improved, and the surface recombination can be reduced, so that the minority carrier lifetime of the diffused silicon wafer can be prolonged.
The open-circuit voltage and the short-circuit current of the solar cell are directly influenced by the minority carrier lifetime, so that the conversion efficiency of the solar cell is influenced; meanwhile, the increase or decrease of the minority carrier lifetime reflects the amount of impurities contained in the solar cell, and the increase of the minority carrier lifetime is also required for improving the quantum efficiency (IQE) in the solar cell in relation to the attenuation rate of the cell efficiency. The diffusion method of the invention combines the steps of first phosphorus deposition, laser doping, phosphorus-silicon glass layer removal, second phosphorus deposition and junction pushing, can effectively prolong the minority carrier lifetime of the diffused silicon wafer, and thus improves the performance of the crystalline silicon solar cell adopting the silicon wafer.
In addition, in the invention, in a one-time diffusion process, the operations of first phosphorus deposition, laser doping, phosphorosilicate glass layer removal, second phosphorus deposition, knot pushing and the like are sequentially carried out on a silicon wafer, wherein the first phosphorus deposition and the second phosphorus deposition can be regarded as an integral phosphorus deposition step in the diffusion process, and the operations of laser doping and phosphorosilicate glass layer removal are added in the integral phosphorus deposition step. Based on this, the diffusion method of the present invention is significantly different from the conventional method of preparing a doped silicon wafer through two complete diffusion processes.
The present invention will be further described with reference to specific examples and comparative examples, which should not be construed as limiting the scope of the present invention.
Example 1:
a diffusion method of a silicon wafer comprises the following steps:
1) First oxidation treatment
Sending the silicon wafer subjected to texturing treatment into a diffusion furnace, raising the furnace temperature, and checking whether a furnace tube of the diffusion furnace leaks gas or not; and introducing oxygen and large nitrogen into the diffusion furnace to perform first oxidation treatment.
Wherein the flow rate of oxygen is 500sccm, and the flow rate of large nitrogen is 500sccm; the temperature of the first oxidation treatment was 750 ℃, the time of the first oxidation treatment was 3min, and the pressure of the first oxidation treatment gas was 90mbar.
2) First phosphorus deposition
And introducing small nitrogen, oxygen and large nitrogen into the diffusion furnace to perform first phosphorus deposition treatment on the silicon wafer subjected to the first oxidation treatment. Wherein the flow rate of the small nitrogen is 1000sccm, the flow rate of the oxygen is 500sccm, and the flow rate of the large nitrogen is 500sccm; the time for the first phosphorus deposition was 400s and the temperature of the first phosphorus deposition was 780 ℃.
3) Laser doping
And after the first phosphorus deposition is finished, cooling the diffusion furnace, opening a furnace door, moving the silicon wafer out of the diffusion furnace, and then carrying out laser doping treatment on the silicon wafer. The laser energy used was 15kJ. The depth of laser doping was 20nm.
4) Removing phosphorosilicate glass layer on surface of silicon wafer
And after the silicon wafer is subjected to laser doping treatment, removing the phosphorosilicate glass layer on the surface of the silicon wafer by utilizing HF acid etching.
5) Second phosphorus deposition
And (3) feeding the silicon wafer into a diffusion furnace, introducing small nitrogen, oxygen and large nitrogen, heating, and performing second phosphorus deposition treatment on the silicon wafer. Wherein the flow rate of the small nitrogen is 300sccm, the flow rate of the oxygen is 300sccm, and the flow rate of the large nitrogen is 500sccm; the time for the second phosphorus deposition was 50s and the temperature for the second phosphorus deposition was 740 ℃.
6) Knot pushing treatment
And carrying out junction pushing treatment on the silicon wafer at high temperature. The temperature of the knot pushing treatment is 850 ℃, and the time of the knot pushing treatment is 5min.
7) Second oxidation treatment
And introducing oxygen and large nitrogen (not introducing small nitrogen) into the diffusion furnace, and carrying out second oxidation treatment on the silicon wafer. And after the second oxidation treatment is finished, adjusting the pressure in the diffusion furnace to the atmospheric pressure, cooling, opening the furnace door, and moving the silicon wafer out of the diffusion furnace.
Wherein the flow rate of the oxygen is 500sccm, and the flow rate of the big nitrogen is 500sccm; the temperature of the second oxidation treatment was 740 ℃, the time of the second oxidation treatment was 3min, and the gas pressure of the second oxidation treatment was 70mbar.
The silicon wafer prepared by diffusion in this example was used as a silicon wafer substrate, and a solar cell was prepared by passivation and electrode printing. The prepared solar cell was tested for various performances such as conversion efficiency (Eta), open-circuit voltage (Voc), short-circuit current (Isc), fill Factor (FF), series resistance (Rs), and parallel resistance (Rsh). The specific performance test results are shown in table 1.
Example 2:
a diffusion method of a silicon wafer comprises the following steps:
1) First oxidation treatment
Sending the silicon wafer subjected to texturing treatment into a diffusion furnace, raising the furnace temperature, and checking whether a furnace tube of the diffusion furnace leaks gas or not; and introducing oxygen and large nitrogen into the diffusion furnace to perform first oxidation treatment.
Wherein the flow rate of oxygen is 1000sccm, and the flow rate of large nitrogen is 1000sccm; the temperature of the first oxidation treatment was 765 deg.C, the time of the first oxidation treatment was 6min, and the pressure of the first oxidation treatment gas was 100mbar.
2) First phosphorus deposition
And introducing small nitrogen, oxygen and large nitrogen into the diffusion furnace to perform first phosphorus deposition treatment on the silicon wafer subjected to the first oxidation treatment. Wherein the flow rate of the small nitrogen is 1500sccm, the flow rate of the oxygen is 1000sccm, and the flow rate of the large nitrogen is 1000sccm; the time for the first phosphorus deposition was 600s and the temperature of the first phosphorus deposition was 790 ℃.
3) Laser doping
And after the first phosphorus deposition is finished, cooling the diffusion furnace, opening the furnace door, moving the silicon wafer out of the diffusion furnace, and then carrying out laser doping treatment on the silicon wafer. The laser energy used was 18kJ. The depth of laser doping was 30nm.
4) Removing phosphorosilicate glass layer on surface of silicon wafer
And after the silicon wafer is subjected to laser doping treatment, removing the phosphorosilicate glass layer on the surface of the silicon wafer.
5) Second phosphorus deposition
And (3) feeding the silicon wafer into a diffusion furnace, introducing small nitrogen, oxygen and large nitrogen, heating, and performing second phosphorus deposition treatment on the silicon wafer. Wherein the flow rate of the small nitrogen is 500sccm, the flow rate of the oxygen is 600sccm, and the flow rate of the large nitrogen is 1500sccm; the time for the second phosphor deposition was 100s and the temperature for the second phosphor deposition was 750 ℃.
6) Knot pushing treatment
And carrying out junction pushing treatment on the silicon wafer at high temperature. The temperature of the knot pushing treatment is 860 ℃, and the time of the knot pushing treatment is 10min.
7) Second oxidation treatment
And introducing oxygen and large nitrogen (not introducing small nitrogen) into the diffusion furnace, and carrying out second oxidation treatment on the silicon wafer. And after the second oxidation treatment is finished, adjusting the pressure in the diffusion furnace to the atmospheric pressure, cooling, opening the furnace door, and moving the silicon wafer out of the diffusion furnace.
Wherein the flow rate of oxygen is 1000sccm, and the flow rate of large nitrogen is 1000sccm; the temperature of the second oxidation treatment was 770 ℃, the time of the second oxidation treatment was 5min, and the gas pressure of the second oxidation treatment was 100mbar.
The silicon wafer prepared after diffusion in this example was used as a silicon wafer substrate, and a solar cell was prepared by the same method as in example 1. And testing the conversion efficiency, open-circuit voltage, short-circuit current, filling factor, series resistance, parallel resistance and other performances of the prepared solar cell. Specific performance test results are shown in table 1.
Example 3:
a diffusion method of a silicon wafer comprises the following steps:
1) First oxidation treatment
Sending the silicon wafer subjected to texturing into a diffusion furnace, raising the furnace temperature, and checking whether a furnace tube of the diffusion furnace leaks gas or not; and introducing oxygen and large nitrogen into the diffusion furnace to perform first oxidation treatment.
Wherein the flow rate of oxygen is 1500sccm, and the flow rate of large nitrogen is 1500sccm; the temperature of the first oxidation treatment was 780 ℃, the time of the first oxidation treatment was 8min, and the pressure of the first oxidation treatment gas was 100mbar.
2) First phosphorus deposition
And introducing small nitrogen, oxygen and large nitrogen into the diffusion furnace to perform first phosphorus deposition treatment on the silicon wafer subjected to the first oxidation treatment. Wherein the flow rate of the small nitrogen is 1500sccm, the flow rate of the oxygen is 1000sccm, and the flow rate of the large nitrogen is 1000sccm; the time for the first phosphorus deposition was 500s and the temperature for the first phosphorus deposition was 785 ℃.
3) Laser doping
And after the first phosphorus deposition is finished, cooling the diffusion furnace, opening the furnace door, moving the silicon wafer out of the diffusion furnace, and then carrying out laser doping treatment on the silicon wafer. The laser energy used was 19kJ. The depth of laser doping was 34nm.
4) Removing phosphorosilicate glass layer on surface of silicon wafer
And after the silicon wafer is subjected to laser doping treatment, removing the phosphorosilicate glass layer on the surface of the silicon wafer.
5) Second phosphorus deposition
And (3) feeding the silicon wafer into a diffusion furnace, introducing small nitrogen, oxygen and large nitrogen, heating, and performing second phosphorus deposition treatment on the silicon wafer. Wherein the flow rate of the small nitrogen is 500sccm, the flow rate of the oxygen is 600sccm, and the flow rate of the large nitrogen is 1500sccm; the time for the second phosphorus deposition was 100s and the temperature for the second phosphorus deposition was 750 ℃.
6) Knot pushing treatment
And carrying out junction pushing treatment on the silicon wafer at high temperature. The temperature of the knot pushing treatment is 860 ℃, and the time of the knot pushing treatment is 15min.
7) Second oxidation treatment
And introducing oxygen and large nitrogen (not introducing small nitrogen) into the diffusion furnace, and carrying out second oxidation treatment on the silicon wafer. And after the second oxidation treatment is finished, adjusting the pressure in the diffusion furnace to the atmospheric pressure, cooling, opening the furnace door, and moving the silicon wafer out of the diffusion furnace.
Wherein the flow rate of oxygen is 1500sccm, and the flow rate of large nitrogen is 1500sccm; the temperature of the second oxidation treatment was 790 ℃, the time of the second oxidation treatment was 8min, and the gas pressure of the second oxidation treatment was 120mbar.
The silicon wafer prepared after diffusion in this example was used as a silicon wafer substrate, and a solar cell was prepared by the same method as in example 1. And testing the conversion efficiency, open-circuit voltage, short-circuit current, filling factor, series resistance, parallel resistance and other performances of the prepared solar cell. Specific performance test results are shown in table 1.
Comparative example 1:
a diffusion method for a silicon wafer, which is substantially the same as that of example 1 except that: after the first phosphorus deposition, no laser doping step is performed before the phosphosilicate glass layer is removed.
The silicon wafer prepared after diffusion in this comparative example was used as a silicon wafer substrate, and a solar cell was prepared in the same manner as in example 1. And testing the conversion efficiency, open-circuit voltage, short-circuit current, filling factor, series resistance, parallel resistance and other performances of the prepared solar cell. The specific performance test results are shown in table 1.
Comparative example 2:
a diffusion method for a silicon wafer, which is substantially the same as that of example 1 except that: after laser doping, no step is performed to remove the phosphosilicate glass layer prior to the second phosphorous deposition.
The silicon wafer prepared after the diffusion of the comparative example was used as a silicon wafer substrate, and a solar cell was prepared in the same manner as in example 1. And testing the conversion efficiency, open-circuit voltage, short-circuit current, filling factor, series resistance, parallel resistance and other performances of the prepared solar cell. Specific performance test results are shown in table 1.
Comparative example 3:
a diffusion method for a silicon wafer, the diffusion method being substantially the same as in example 1 (or other examples) except that: the laser energy for laser doping was 25kJ.
The silicon wafer prepared after diffusion in this comparative example was used as a silicon wafer substrate, and a solar cell was prepared in the same manner as in example 1. And testing the conversion efficiency, open-circuit voltage, short-circuit current, filling factor, series resistance, parallel resistance and other performances of the prepared solar cell. The specific performance test results are shown in table 1.
Table 1 results of performance test of solar cells of each example and comparative example
As is clear from the data in table 1, in example 2, the temperature, time, and gas flow rate of the pre-oxidation treatment (first oxidation treatment) were increased as compared with example 1, so that the dopant atoms in the surface plug treatment were less, and the FF was lower; meanwhile, in embodiment 2, the junction push temperature and time are increased, the number of activated doping atoms is increased, and the Voc and the Isc are increased.
Comparative example 1 compared to example 1, the laser doping step was not performed and the doping atoms were not laser driven into the inner layer of the wafer, so comparative example 1 had a relatively low Voc, isc.
Compared with the embodiment 1, in the comparative example 2, the phosphorosilicate glass layer on the surface layer of the silicon wafer is not removed before the second phosphorus deposition, so that the phosphorosilicate glass layer and a phosphorus source deposited by the second phosphorus are activated and pushed into the silicon wafer together in the junction pushing process, the doping concentration is higher, the surface concentration is higher, the Voc and the Isc of the comparative example 2 are reduced, and the FF is improved.
Compared with the embodiment 1, in the comparative example 3, the laser energy in the laser doping step is higher, so that the whole doping concentration and depth are relatively higher, and the open-circuit voltage Voc of the cell is reduced; meanwhile, too high laser energy can damage the pyramid structure of the antireflection layer on the surface of the cell, so that light absorption is weakened, and the Isc is reduced.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A diffusion method of a silicon wafer is characterized by comprising the following steps:
carrying out first phosphorus deposition on a silicon wafer in a first atmosphere;
carrying out laser doping on the silicon wafer subjected to the first phosphorus deposition;
removing the phosphosilicate glass layer on the surface of the silicon wafer after laser doping;
carrying out second phosphorus deposition on the silicon wafer with the phosphorosilicate glass layer removed in a second atmosphere; and
and carrying out junction pushing treatment on the silicon wafer subjected to the second phosphorus deposition.
2. The diffusion method of a silicon wafer according to claim 1, wherein the flow rate of the small nitrogen in the first atmosphere is 1000sccm to 1500sccm, the flow rate of the oxygen is 500sccm to 1000sccm, and the flow rate of the large nitrogen is 500sccm to 1000sccm.
3. The diffusion method for the silicon wafer according to claim 1, wherein the first phosphorus deposition time is 400s to 600s, and the temperature is 780 ℃ to 790 ℃.
4. The silicon wafer diffusion method according to claim 1, wherein the laser energy of the laser doping is 15kJ to 20kJ, and the depth of the laser doping is 20nm to 50nm.
5. The method as claimed in claim 1, wherein the second atmosphere has a small nitrogen flow rate of 300 to 500sccm, an oxygen flow rate of 300 to 600sccm, and a large nitrogen flow rate of 500 to 1500sccm.
6. The diffusion method for the silicon wafer according to claim 1, wherein the second phosphorus deposition time is 50s to 100s, and the temperature is 740 ℃ to 750 ℃.
7. The diffusion method of the silicon wafer according to claim 1, wherein the temperature of the junction-pushing treatment is 850 to 860 ℃ and the time is 5 to 15min.
8. The diffusion method of silicon wafers according to any one of claims 1 to 7, further comprising the steps of, before the first phosphorus deposition of the silicon wafer in the first atmosphere:
carrying out first oxidation treatment on the silicon wafer in a third atmosphere;
optionally, the oxygen flow rate in the third atmosphere is 500sccm to 1500sccm, and the large nitrogen flow rate is 500sccm to 1500sccm;
optionally, the temperature of the first oxidation treatment is 750-780 ℃, the time is 3-10 min, and the gas pressure is 90-110 mbar.
9. The method for diffusing the silicon wafer according to any one of claims 1 to 7, wherein after the silicon wafer after the second phosphorus deposition is subjected to the push-junction treatment, the method further comprises the following steps:
carrying out second oxidation treatment on the silicon wafer in a fourth atmosphere;
optionally, the flow rate of oxygen in the fourth atmosphere is 500sccm to 1500sccm, and the flow rate of large nitrogen is 500sccm to 1500sccm;
optionally, the temperature of the second oxidation treatment is 740-800 ℃, the time is 3-10 min, and the gas pressure is 70-150 mbar.
10. A solar cell, characterized in that it uses a silicon wafer produced by the diffusion method according to any one of claims 1 to 9.
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| CN105070787A (en) * | 2015-08-18 | 2015-11-18 | 东莞南玻光伏科技有限公司 | Crystalline silicon solar cell and diffusion method therefor |
| CN110429157A (en) * | 2018-08-28 | 2019-11-08 | 协鑫集成科技股份有限公司 | The preparation method and solar battery of solar battery |
| CN113437182A (en) * | 2021-06-25 | 2021-09-24 | 东莞南玻光伏科技有限公司 | Diffusion process and preparation method of solar cell and silicon wafer |
| CN113571602A (en) * | 2021-07-23 | 2021-10-29 | 横店集团东磁股份有限公司 | Secondary diffusion selective emitter and preparation method and application thereof |
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| CN105070787A (en) * | 2015-08-18 | 2015-11-18 | 东莞南玻光伏科技有限公司 | Crystalline silicon solar cell and diffusion method therefor |
| CN110429157A (en) * | 2018-08-28 | 2019-11-08 | 协鑫集成科技股份有限公司 | The preparation method and solar battery of solar battery |
| CN113437182A (en) * | 2021-06-25 | 2021-09-24 | 东莞南玻光伏科技有限公司 | Diffusion process and preparation method of solar cell and silicon wafer |
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