CN115207167A - Method for cleaning silicon polished surface - Google Patents
Method for cleaning silicon polished surface Download PDFInfo
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- CN115207167A CN115207167A CN202211125312.6A CN202211125312A CN115207167A CN 115207167 A CN115207167 A CN 115207167A CN 202211125312 A CN202211125312 A CN 202211125312A CN 115207167 A CN115207167 A CN 115207167A
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- 238000004140 cleaning Methods 0.000 title claims abstract description 80
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 62
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 62
- 239000010703 silicon Substances 0.000 title claims abstract description 62
- 238000000034 method Methods 0.000 title claims abstract description 37
- 239000007864 aqueous solution Substances 0.000 claims abstract description 56
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 54
- 239000007788 liquid Substances 0.000 claims abstract description 31
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 30
- 239000002253 acid Substances 0.000 claims abstract description 29
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims abstract description 28
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims abstract description 27
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 24
- 230000001590 oxidative effect Effects 0.000 claims abstract description 23
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 15
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims abstract description 15
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 15
- 238000001035 drying Methods 0.000 claims abstract description 10
- 238000011282 treatment Methods 0.000 claims abstract description 10
- 238000011221 initial treatment Methods 0.000 claims abstract description 3
- 239000000243 solution Substances 0.000 claims description 35
- 238000005498 polishing Methods 0.000 claims description 16
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 13
- RILZRCJGXSFXNE-UHFFFAOYSA-N 2-[4-(trifluoromethoxy)phenyl]ethanol Chemical compound OCCC1=CC=C(OC(F)(F)F)C=C1 RILZRCJGXSFXNE-UHFFFAOYSA-N 0.000 claims description 11
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 6
- 239000002585 base Substances 0.000 claims description 5
- 239000003513 alkali Substances 0.000 claims description 3
- IDGUHHHQCWSQLU-UHFFFAOYSA-N ethanol;hydrate Chemical compound O.CCO IDGUHHHQCWSQLU-UHFFFAOYSA-N 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 abstract description 11
- 229910021645 metal ion Inorganic materials 0.000 abstract description 7
- 238000002161 passivation Methods 0.000 abstract description 7
- 238000007517 polishing process Methods 0.000 abstract description 6
- 230000003746 surface roughness Effects 0.000 abstract description 6
- 239000002245 particle Substances 0.000 abstract description 3
- 230000000052 comparative effect Effects 0.000 description 10
- 238000004519 manufacturing process Methods 0.000 description 7
- 238000000151 deposition Methods 0.000 description 5
- 239000006227 byproduct Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000011259 mixed solution Substances 0.000 description 4
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 4
- 238000005530 etching Methods 0.000 description 3
- 239000011859 microparticle Substances 0.000 description 3
- 238000002310 reflectometry Methods 0.000 description 3
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 2
- 229910052581 Si3N4 Inorganic materials 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 239000010419 fine particle Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 2
- 238000007747 plating Methods 0.000 description 2
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 2
- 229910052814 silicon oxide Inorganic materials 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 1
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000007650 screen-printing Methods 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02041—Cleaning
- H01L21/02057—Cleaning during device manufacture
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
- H01L21/30604—Chemical etching
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
- H01L31/042—PV modules or arrays of single 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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- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- General Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Computer Hardware Design (AREA)
- Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Electromagnetism (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Mechanical Treatment Of Semiconductor (AREA)
- Cleaning Or Drying Semiconductors (AREA)
- Weting (AREA)
Abstract
The invention relates to the technical field of solar cells, and particularly discloses a method for cleaning a polished silicon surface. The cleaning method comprises the following steps: cleaning the silicon wafer by sequentially adopting mixed acid liquid and pure water respectively to obtain a primary processing wafer, wherein the mixed acid liquid is an aqueous solution containing phosphoric acid, fluoboric acid and nitric acid; sequentially adopting alkaline mixed liquor and pure water to respectively clean the primary treatment piece to obtain a secondary treatment piece, wherein the alkaline mixed liquor is an aqueous solution containing strong base and ethanol; and respectively cleaning and drying the secondary processing piece by sequentially adopting oxidizing liquid and pure water to obtain the polished silicon wafer, wherein the oxidizing liquid is an aqueous solution comprising hydrofluoric acid and hydrogen peroxide. The cleaning method provided by the invention can effectively remove the residual tiny particles in the polishing process, reduce the surface roughness and improve the surface morphology; and residual organic matters and metal ions on the surface can be removed, so that the subsequent passivation process is facilitated, and the photoelectric conversion efficiency can be improved.
Description
Technical Field
The invention relates to the technical field of solar cells, in particular to a method for cleaning a polished silicon surface.
Background
In the solar cell production process, a back polishing treatment is usually adopted for either the P-type cell or the N-type cell to reduce the composite area of the back surface and improve the back reflectivity, thereby improving the cell performance. The back polishing is single-side polishing, namely back polishing and front retaining suede. The single-side polishing process specifically comprises the following steps: one side is protected by a mask, and the other side is etched at high temperature by adopting high-concentration polishing solution to realize the polishing corrosion effect of the side without the mask. In the polishing and etching process, as the reaction proceeds, fine particles or micro protrusions exist on the local surface of the polished silicon wafer due to the concentration deviation of the polishing solution, the increase of byproducts, the uniformity of the previous process and other factors, the overall flatness is affected, the specific surface area is increased, the subsequent passivation effect is affected, and the further improvement of the efficiency and yield of the battery is not facilitated.
At present, the existing surface defects are generally used as initial reaction points, and relatively uniform surface defects are utilized to realize isotropic corrosion effects, but the surface roughness of a polished surface is increased, and the flatness of the polished surface cannot meet the use requirements. Therefore, there is a need to develop a cleaning method after polishing a silicon wafer, which is very important for effectively removing the micro particles left in the polishing process, improving the surface morphology, and removing the residual organic matters on the surface.
Disclosure of Invention
Aiming at the problems of high roughness, low flatness and the like of the polished surface of the polished silicon wafer in the prior art, the invention provides the method for cleaning the polished surface of the silicon wafer, which can effectively remove tiny particles remained in the polishing process, reduce the surface roughness and improve the surface morphology; and residual organic matters and metal ions on the surface can be removed, so that the subsequent passivation process is facilitated, and the photoelectric conversion efficiency can be improved.
In order to achieve the purpose of the invention, the embodiment of the invention adopts the following technical scheme:
a method for cleaning a silicon polished surface, the method comprising the steps of
Step one, respectively cleaning a silicon wafer by sequentially adopting mixed acid liquid and pure water to obtain a primary processing wafer, wherein the mixed acid liquid is an aqueous solution containing phosphoric acid, fluoroboric acid and nitric acid;
step two, respectively cleaning the primary treatment piece by sequentially adopting alkaline mixed liquor and pure water to obtain a secondary treatment piece, wherein the alkaline mixed liquor is an aqueous solution containing strong base and ethanol;
and step three, respectively cleaning and drying the secondary processing wafer by sequentially adopting oxidizing liquid and pure water to obtain the polished silicon wafer, wherein the oxidizing liquid is an aqueous solution comprising hydrofluoric acid and hydrogen peroxide.
Compared with the prior art, the cleaning method for the silicon polished surface has the following advantages:
firstly, cleaning by using mixed acid liquor containing fluoboric acid, nitric acid and phosphoric acid, oxidizing the surface of the silicon by using the nitric acid, and oxidizing possibly residual metals and organic matters; the method comprises the following steps of (1) carrying out slow etching on a surface oxide by using fluoboric acid and phosphoric acid, and adjusting the activity of the fluoboric acid and the overall reaction rate by using temperature to realize the finishing of surface flatness and reduce the surface roughness; removing reaction byproducts possibly remaining on the surface by using strong alkali and ethanol to ensure that the surface is clean; and finally, removing metal ions by hydrofluoric acid, and covering a thin silicon oxide layer on the surface by hydrogen peroxide to protect the surface of the silicon wafer and ensure that the cleaned polished silicon wafer is not polluted by the environment in the process of transferring to the subsequent process.
The cleaning method is mainly used for cleaning the polished silicon wafer, and can effectively remove residual tiny particles in the polishing process, reduce the surface roughness and improve the surface morphology; and residual organic matters and metal ions on the surface can be removed, so that the subsequent passivation process is facilitated, and the photoelectric conversion efficiency is obviously improved.
Optionally, the mixed acid solution comprises the following components in percentage by volume: phosphoric acid aqueous solution: 50% -60%, fluoroboric acid aqueous solution: 5% -10%, nitric acid aqueous solution: 2-5% of water, and the balance of water.
Optionally, the concentration of the phosphoric acid aqueous solution is 80wt% to 90wt%.
Further optionally, the concentration of the aqueous phosphoric acid solution is 85wt%.
Optionally, the concentration of the fluoroboric acid aqueous solution is 45wt% -52 wt%.
Further optionally, the concentration of the aqueous fluoroboric acid solution is 49wt%.
Optionally, the concentration of the nitric acid aqueous solution is 60wt% to 68wt%.
Further optionally, the concentration of the aqueous nitric acid solution is 63wt%.
Through the preferred proportion of each component in the mixed acid liquid, the silicon wafer polishing agent can effectively remove micro particles on the polished surface of the silicon wafer in the cleaning process, improves the surface flatness and is beneficial to subsequent passivation.
Optionally, the alkaline mixed solution includes the following components by volume percent: strong alkaline aqueous solution: 1% -5%, ethanol aqueous solution: 5-10% of water, and the balance of water.
Optionally, the concentration of the strong alkali aqueous solution is 45wt% -55 wt%.
Further optionally, the concentration of the aqueous strong base solution is 50wt%.
Optionally, the strong base is sodium hydroxide or potassium hydroxide.
Optionally, the concentration of the ethanol aqueous solution is 90wt% to 95wt%.
Further optionally, the concentration of the aqueous ethanol solution is 95wt%.
By the optimal proportion of the components in the alkaline mixed solution, the by-products and organic matters possibly remaining in the mixed acid solution cleaning process can be effectively removed, and the surface cleanness is ensured.
Optionally, the oxidizing solution comprises the following components in percentage by volume: hydrofluoric acid aqueous solution: 3% -10%, hydrogen peroxide aqueous solution: 2% -10% and the balance of water.
Optionally, the concentration of the hydrofluoric acid aqueous solution is 40wt% to 50wt%.
Further optionally, the concentration of the hydrofluoric acid aqueous solution is 49%.
Optionally, the concentration of the hydrogen peroxide aqueous solution is 28-30 wt%.
Further optionally, the concentration of the hydrogen peroxide solution is 30wt%.
Through the optimized proportion of each component in the oxidizing liquid, organic matters and metal ions remained on the surface of the silicon wafer can be effectively removed, an extremely thin silicon oxide film is formed on the surface of the silicon wafer, and the pollution of micro-particles in the air or drying to the surface can be effectively prevented.
Optionally, in the first step, the conditions of the mixed acid cleaning are as follows: the temperature is 10-50 ℃, and the time is 1 min-10 min.
Optionally, in the second step, the cleaning time of the alkaline mixed solution is 1min to 5min.
Optionally, in the third step, the cleaning time of the oxidizing solution is 2min to 6min.
Through the optimized cleaning conditions, the flatness of the polished surface can be effectively improved, the surface morphology is improved, organic matters, byproducts and metal ions remained on the surface can be effectively removed, the subsequent passivation process is facilitated, and the photoelectric conversion efficiency of the cell is further improved.
Optionally, in the first step, the second step and the third step, the cleaning conditions of the pure water are as follows: the temperature is 20-50 ℃, and the time is 2min-8min.
And ensuring that no mixed acid liquid, alkaline mixed liquid and oxidizing liquid remain on the surface of the silicon wafer by the optimized cleaning condition of pure water.
Optionally, the drying conditions are as follows: the temperature is 60-100 ℃, and the time is 5-20min.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
Example 1
The embodiment of the invention provides a preparation process of an N-type solar cell, which comprises the following steps:
s1, texturing is carried out on an N-type monocrystalline silicon wafer with the resistivity of 1 omega cm, and the reflectivity is 10%;
s2, carrying out boron diffusion doping on the textured N-type silicon wafer, wherein the square resistance is 120 omega;
s3, carrying out single-side etching and single-side polishing on the N-type silicon wafer subjected to boron diffusion, wherein the back reflectivity is 36%;
cleaning the polished silicon wafer by adopting the following cleaning method:
cleaning the silicon wafer for 5min at 40 ℃ by using mixed acid liquid, wherein the mixed acid liquid comprises the following components in percentage by volume: phosphoric acid aqueous solution with a concentration of 85 wt%: 50% aqueous solution of fluoroboric acid at a concentration of 49% by weight: 7% aqueous nitric acid solution with a concentration of 63 wt%: 2 percent of water, and the balance of water;
cleaning the cleaned silicon wafer for 5min at 40 ℃ by adopting pure water to obtain a first-stage treatment wafer;
cleaning the first-stage processing sheet for 3min at normal temperature by using alkaline mixed liquor; the alkaline mixed liquor comprises the following components in percentage by volume: 50wt% strength aqueous potassium hydroxide solution: 2.5%, 95wt% aqueous ethanol solution: 6 percent of water, and the balance of water;
cleaning the cleaned silicon wafer for 8min at 20 ℃ by using pure water to obtain a secondary treatment wafer;
and (2) cleaning the secondary treatment sheet for 5min at normal temperature by using an oxidizing solution, wherein the oxidizing solution comprises the following components in percentage by volume: hydrofluoric acid aqueous solution having a concentration of 49 wt%: 4% of hydrogen peroxide aqueous solution with the concentration of 30 wt%: 6 percent of water, and the balance of water;
cleaning the cleaned silicon wafer for 5min at 30 ℃ by using pure water, and drying for 10min at 60 ℃ to obtain a cleaned polished silicon wafer;
s4, depositing polycrystalline silicon on the cleaned N-type silicon wafer, wherein the thickness of the polycrystalline silicon is 120nm;
s5, performing winding plating removal cleaning on the N-type silicon wafer after the polycrystalline silicon is deposited;
s6, depositing aluminum oxide with the thickness of 4nm on the silicon wafer after the winding plating removal and cleaning by adopting ALD;
s7, depositing 80nm silicon nitride on the silicon wafer after depositing the aluminum oxide by adopting a PECVD method;
s8, forming electrodes on the front side and the back side of the cell on the silicon wafer subjected to silicon nitride deposition by adopting a screen printing technology, and forming good contact between metal and polycrystalline silicon through high-temperature sintering;
and S9, carrying out electrical property test and sorting on the sintered cell.
Example 2
The present embodiment provides a process for preparing an N-type solar cell, which is different from embodiment 1 in that: and S3, cleaning the polished silicon wafer by adopting the following cleaning method:
cleaning a silicon wafer for 1min at 50 ℃ by using a mixed acid solution, wherein the mixed acid solution comprises the following components in percentage by volume: phosphoric acid aqueous solution with concentration of 90 wt%: 55%, aqueous fluoroboric acid solution with a concentration of 52% by weight: 5% aqueous solution of nitric acid with a concentration of 68 wt%: 5 percent of water, and the balance of water;
cleaning the cleaned silicon wafer for 2min at 50 ℃ by adopting pure water to obtain a first-stage treatment wafer;
cleaning the primary-stage processing sheet for 1min at normal temperature by using alkaline mixed liquor; the alkaline mixed liquor comprises the following components in percentage by volume: 55wt% strength aqueous potassium hydroxide solution: 5%, 93wt% aqueous ethanol solution: 10 percent, and the balance being water;
cleaning the cleaned silicon wafer for 5min at 35 ℃ by using pure water to obtain a secondary processing wafer;
and (3) cleaning the secondary processing sheet for 2min at normal temperature by using an oxidizing solution, wherein the oxidizing solution comprises the following components in percentage by volume: aqueous hydrofluoric acid solution having a concentration of 45 wt%: 10% of hydrogen peroxide aqueous solution with the concentration of 28 wt%: 2 percent of water, and the balance of water;
and cleaning the cleaned silicon wafer for 6min at 25 ℃ by adopting pure water, and drying for 5min at 100 ℃ to obtain the cleaned polished silicon wafer.
Example 3
The present embodiment provides a process for preparing an N-type solar cell, which is different from embodiment 1 in that: and S3, cleaning the polished silicon wafer by adopting the following cleaning method:
cleaning a silicon wafer at 10 ℃ for 10min by using a mixed acid liquid, wherein the mixed acid liquid comprises the following components in percentage by volume: phosphoric acid aqueous solution with a concentration of 80 wt%: 60% aqueous fluoroboric acid solution having a concentration of 45% by weight: 10%, 60wt% aqueous nitric acid solution: 3 percent of water, and the balance of water;
cleaning the cleaned silicon wafer for 6min at 20 ℃ by using pure water to obtain a first-stage treatment wafer;
cleaning the primary-stage processing sheet for 5min at normal temperature by using alkaline mixed liquor; the alkaline mixed liquor comprises the following components in percentage by volume: 45wt% strength aqueous potassium hydroxide solution: 1%, 90wt% aqueous ethanol solution: 5 percent, and the balance being water;
cleaning the cleaned silicon wafer for 8min at 20 ℃ by using pure water to obtain a secondary processing wafer;
and (3) cleaning the secondary processing sheet for 6min at normal temperature by using an oxidizing solution, wherein the oxidizing solution comprises the following components in percentage by volume: hydrofluoric acid aqueous solution having a concentration of 40 wt%: 3% of hydrogen peroxide aqueous solution with the concentration of 29 wt%: 10 percent, and the balance being water;
and cleaning the cleaned silicon wafer for 4.5min at 32 ℃ by adopting pure water, and drying for 20min at 85 ℃ to obtain the cleaned polished silicon wafer.
In order to better illustrate the technical solution of the present invention, further comparison is made below by comparing examples of the present invention with comparative examples.
Comparative example 1
This comparative example provides a process for preparing an N-type solar cell, which is different from example 1 in that: and in the S3 cleaning step, replacing the phosphoric acid aqueous solution with the concentration of 85wt% in the mixed acid liquid with hydrofluoric acid with the concentration of 49wt%.
Comparative example 2
This comparative example provides a process for preparing an N-type solar cell, which is different from example 1 in that: and in the S3 cleaning step, replacing the nitric acid aqueous solution with the concentration of 63wt% in the mixed acid liquid with the hydrogen peroxide aqueous solution with the concentration of 30wt%.
Comparative example 3
This comparative example provides a process for preparing an N-type solar cell, which is different from example 1 in that: and in the S3 cleaning step, replacing the potassium hydroxide aqueous solution with the concentration of 50wt% in the alkaline mixed solution with an ammonia aqueous solution with the concentration of 28 wt%.
Comparative example 4
This comparative example provides a process for preparing an N-type solar cell, which is different from example 1 in that: s3, in the cleaning step, the polished silicon wafer is cleaned by adopting the following cleaning method, and the cleaning sequence of the mixed acid liquid and the oxidizing liquid is changed, specifically as follows:
cleaning a silicon wafer for 5min at 40 ℃ by using an oxidizing solution, wherein the oxidizing solution comprises the following components in percentage by volume: hydrofluoric acid aqueous solution having a concentration of 49 wt%: 4% of hydrogen peroxide aqueous solution with the concentration of 30 wt%: 6 percent, and the balance being water;
cleaning the cleaned silicon wafer for 5min at 40 ℃ by adopting pure water to obtain a first-stage treatment wafer;
cleaning the primary-stage processing sheet for 3min at normal temperature by using alkaline mixed liquor; the alkaline mixed liquor comprises the following components in percentage by volume: 50wt% strength aqueous potassium hydroxide solution: 2.5%, 95wt% aqueous ethanol solution: 6 percent, and the balance being water;
cleaning the cleaned silicon wafer for 8min at 20 ℃ by using pure water to obtain a secondary processing wafer;
and cleaning the secondary processing sheet for 5min at normal temperature by using mixed acid liquid, wherein the mixed acid liquid comprises the following components in percentage by volume: phosphoric acid aqueous solution with a concentration of 85 wt%: 50% aqueous solution of fluoroboric acid at a concentration of 49% by weight: 7% aqueous nitric acid solution with a concentration of 63 wt%: 2 percent of water, and the balance of water;
and cleaning the cleaned silicon wafer for 5min at 30 ℃ by adopting pure water, and drying for 10min at 60 ℃ to obtain the cleaned polished silicon wafer.
In order to better illustrate the characteristics of the N-type solar cell provided in the example of the present invention, the N-type solar cell prepared in example 1~3 and comparative example 1~4 was tested for performance, and the results are shown in table 1 below.
TABLE 1
Voc is open circuit voltage in mV;
jsc is current density in mA/cm 2 ；
The FF is a filling factor and has a unit of%;
eta above is the conversion efficiency in%.
As can be seen from table 1, the N-type solar cell provided by the present application has higher conversion efficiency due to the specific components and the specific cleaning sequence, which indicates that the cleaning method using the specific components and the specific sequence can effectively remove the residual fine particles in the polishing process, reduce the surface roughness, and improve the surface morphology; and residual organic matters and metal ions on the surface can be removed, so that the subsequent passivation process is facilitated, and the photoelectric conversion efficiency can be improved.
The above description is intended to be illustrative of the preferred embodiment of the present invention and should not be taken as limiting the invention, but rather, the invention is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.
Claims (6)
1. A method for cleaning a polished silicon surface is characterized in that: the cleaning method comprises the following steps:
step one, respectively cleaning a silicon wafer by sequentially adopting mixed acid liquid and pure water to obtain a primary processing wafer, wherein the mixed acid liquid is an aqueous solution containing phosphoric acid, fluoroboric acid and nitric acid, and the mixed acid liquid comprises the following components in percentage by volume: phosphoric acid aqueous solution: 50% -60%, fluoroboric acid aqueous solution: 5% -10%, nitric acid aqueous solution: 2% -5% of water, and the balance of water; the concentration of the phosphoric acid aqueous solution is 80-90 wt%; the concentration of the fluoroboric acid aqueous solution is 45-52 wt%; the concentration of the nitric acid aqueous solution is 60-68 wt%;
step two, respectively cleaning the primary treatment piece by sequentially adopting alkaline mixed liquor and pure water to obtain a secondary treatment piece, wherein the alkaline mixed liquor is an aqueous solution containing strong base and ethanol;
and step three, respectively cleaning and drying the secondary processing wafer by sequentially adopting oxidizing liquid and pure water to obtain the polished silicon wafer, wherein the oxidizing liquid is an aqueous solution comprising hydrofluoric acid and hydrogen peroxide.
2. The method for cleaning a silicon polishing surface according to claim 1, wherein: the alkaline mixed liquor comprises the following components in percentage by volume: strong alkaline aqueous solution: 1% -5%, ethanol aqueous solution: 5% -10% of water, and the balance of water; the concentration of the strong alkali aqueous solution is 45-55 wt%; the strong base is sodium hydroxide or potassium hydroxide; the concentration of the ethanol water solution is 90wt% -95 wt%.
3. The method for cleaning a silicon polishing surface according to claim 1, wherein: the oxidizing solution comprises the following components in percentage by volume: hydrofluoric acid aqueous solution: 3% -10%, hydrogen peroxide aqueous solution: 2% -10% of water, and the balance of water; the concentration of the hydrofluoric acid aqueous solution is 40-50 wt%; the concentration of the hydrogen peroxide aqueous solution is 28-30 wt%.
4. The method for cleaning a silicon polishing surface according to claim 1, wherein: in the first step, the conditions of the mixed acid liquid cleaning are as follows: the temperature is 10-50 ℃, and the time is 1-10 min; and/or
In the second step, the cleaning time of the alkaline mixed liquid is 1min to 5min; and/or
In the third step, the cleaning time of the oxidizing liquid is 2min to 6min.
5. The method for cleaning a silicon polishing surface according to claim 1, wherein: in the first step, the second step and the third step, the cleaning conditions of the pure water are as follows: the temperature is 20-50 ℃, and the time is 2min-8min.
6. The method for cleaning a silicon polishing surface according to claim 1, wherein: the drying conditions are as follows: the temperature is 60-100 ℃, and the time is 5-20min.
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