CN114256382A - Texturing and cleaning method for silicon wafer and preparation method for crystalline silicon solar cell - Google Patents
Texturing and cleaning method for silicon wafer and preparation method for crystalline silicon solar cell Download PDFInfo
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Images
Classifications
-
- 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
- H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic System
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B08—CLEANING
- B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
- B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
- B08B3/04—Cleaning involving contact with liquid
- B08B3/08—Cleaning involving contact with liquid the liquid having chemical or dissolving effect
-
- 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
- H01L21/02068—Cleaning during device manufacture during, before or after processing of conductive layers, e.g. polysilicon or amorphous silicon layers
-
- 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
- H01L31/02—Details
- H01L31/0236—Special surface textures
- H01L31/02363—Special surface textures of the semiconductor body itself, e.g. textured active layers
-
- 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
-
- 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
Abstract
The invention relates to a texturing and cleaning method for a silicon wafer and a preparation method for a crystalline silicon solar cell, which comprises the following steps: carrying out rough polishing treatment, acid washing treatment, first alkali washing treatment, texturing treatment, second alkali washing treatment, smoothing treatment, passivation treatment and drying treatment on a silicon wafer in sequence; the pickling solution used for pickling treatment contains ozone, HCl and HF; the first alkaline washing solution used for the first alkaline washing treatment contains soluble alkali metal hydroxide salt and H2O2. According to the invention, acid washing treatment and first alkali washing treatment which are sequentially carried out are added between rough polishing treatment and texturing treatment; the combination of the two can greatly improve the cleaning effect, and further can omit subsequent smoothing treatment and passivationThe post-cleaning step between treatments greatly reduces the consumption of hydrogen peroxide and hydrochloric acid, saves the production cost and has no obvious difference in process flow efficiency.
Description
Technical Field
The invention relates to the technical field of crystalline silicon solar cells, in particular to a texturing and cleaning method for a silicon wafer and a preparation method for a crystalline silicon solar cell.
Background
The crystalline silicon solar cell is a solar cell with a silicon wafer as a base material. Texturing a silicon wafer is the first process for manufacturing a crystalline silicon battery, which is also called surface texturing, and an effective textured structure can enable incident light to be reflected and refracted on the surface of the silicon wafer for many times, so that the light absorption rate is increased, the reflectivity is reduced, and the performance of the battery is improved.
Heterojunction cells, also known as HJT cells (here-junction with Intrinsic Thin-layer), are known as perc (passive Emitter and reader cell) and are the most promising solar cell technology. Compared with the traditional crystal silicon technology, due to the introduction of the amorphous silicon film, the front and back surfaces of the crystal silicon substrate of the silicon heterojunction solar cell realize good passivation, so that the surface passivation is more perfect. And the amorphous silicon film isolates the direct contact between the metal electrode and the silicon material, the carrier recombination loss is further reduced, and the conversion efficiency can be improved.
HJT cells have the natural advantages of high efficiency and high power generation, and the biggest problem is cost compared to the current mainstream PERC technology. The HJT needs high production raw and auxiliary materials and equipment investment to become the most main factors for restricting the rapid development of the HJT, has no large-scale production cost performance temporarily, and is in a small-scale pilot-scale research and development stage at present. Therefore, the current industry is dedicated to continuously striving to improve the HJT conversion efficiency, and on the other hand, it is also the first task to reduce the manufacturing cost and improve the cost performance of the production.
Hydrogen peroxide (H) in the current etching and cleaning process2O2) And the unit consumption of chemicals such as hydrochloric acid (HCl) is high, which leads to high process cost, so the traditional technology still needs to be improved.
Disclosure of Invention
Therefore, it is necessary to provide a silicon wafer texturing and cleaning method and a crystalline silicon solar cell preparation method aiming at the problem of high unit consumption of chemicals such as hydrogen peroxide and hydrochloric acid in the prior art.
The invention is realized by the following technical scheme.
In one aspect of the invention, a silicon wafer texturing and cleaning method is provided, which comprises the following steps:
carrying out rough polishing treatment, acid washing treatment, first alkali washing treatment, texturing treatment, second alkali washing treatment, smoothing treatment, passivation treatment and drying treatment on a silicon wafer in sequence;
the pickling solution used for pickling treatment contains ozone, HCl and HF;
the first alkaline washing solution used for the first alkaline washing treatment contains soluble alkali metal hydroxide salt and H2O2。
In some of the embodiments, the concentration of ozone in the pickling solution is 30-50 ppm; and/or
In the pickling solution, the mass concentration of HCl is 0.02-0.05%, and the mass concentration of HF is 0.9-1.2%.
In some embodiments, the temperature of the acid washing treatment is 20-30 ℃, the time is 180-280 s, and the circulation flow rate is 30-40L/min.
In some embodiments, the first alkaline washing solution contains the soluble alkali metal hydroxide salt with a mass concentration of 0.9-1.2%, and H2O2The mass concentration of (A) is 4-5%.
In some embodiments, the temperature of the first alkali washing treatment is 60-70 ℃, the time is 210-280 s, and the circulation flow rate is 35-45L/min.
In some of these embodiments, the reagent used in the rough polishing process is an alkaline solution; and/or
The temperature of the rough polishing treatment is 75-90 ℃, the time is 120-200 s, and the circulation flow is 30-40L/min.
In some of the embodiments, the agent used in the texturing process is an alkaline solution; and/or
The temperature of the texturing treatment is 75-90 ℃, the time is 500-700 s, and the circulation flow is 20-30L/min.
In some of these embodiments, the second alkaline washing solution used in the second alkaline washing treatment comprises a soluble alkali metal hydroxide salt and H2O2。
In some of these embodiments, the second alkaline washing solution has a mass concentration of the soluble alkali metal hydroxide salt of 0.9% to 1.2%, and H2O2The mass concentration of (A) is 4-5%.
In some embodiments, the temperature of the second alkali washing treatment is 60-70 ℃, the time is 210-280 s, and the circulation flow rate is 35-45L/min.
In some embodiments, the reagents used for the rounding process include HCl and HF; and/or
The temperature of the smoothing treatment is 20-30 ℃, the time is 180-240 s, and the circulation flow is 35-45L/min.
In some of the embodiments, the passivation treatment employs a hydrofluoric acid solution as a reagent; and/or
The passivation treatment temperature is 20-30 ℃, the time is 180-240 s, and the circulation flow is 50-70L/min.
In another aspect of the present invention, a method for preparing a crystalline silicon solar cell is provided, which comprises the following steps:
texturing the silicon wafer by adopting any one of the texturing and cleaning methods;
and sequentially carrying out the steps of depositing an amorphous silicon film, depositing a transparent conductive oxide film and manufacturing a metal electrode on the textured silicon wafer.
According to the texturing and cleaning method for the silicon wafer, the silicon wafer is subjected to rough polishing treatment, acid washing treatment, first alkali washing treatment, texturing treatment, second alkali washing treatment, smoothing treatment, passivation treatment and drying treatment in sequence, and particularly the acid washing treatment and the first alkali washing treatment which are sequentially carried out are added between the rough polishing treatment and the texturing treatment; the acid cleaning treatment utilizes ozone to oxidize the surface of the silicon wafer after the rough polishing treatment, and compact SiO can be formed on the surface of the silicon wafer2The oxide film can be removed at the same timeAnd a part of metal impurities are removed, HCl has double effects of adjusting the pH value of the pickling solution and removing heavy metal ions, and HF can effectively corrode the silicon oxide layer, so that the silicon oxide layer, organic matters and metal stains are removed. Followed by a first alkaline washing treatment with a mixture of a soluble alkali metal hydroxide salt and H2O2The aqueous solution is subjected to alkaline washing, the cleaning effect can be greatly improved by combining the aqueous solution and the alkaline washing, and the post-cleaning step between subsequent smoothing treatment and passivation treatment can be omitted, so that the consumption of hydrogen peroxide and hydrochloric acid is greatly reduced, the production cost is saved, and meanwhile, the process flow efficiency has no obvious difference.
Drawings
FIG. 1 is a photomicrograph and PL diagram of the silicon wafer obtained in example 1;
FIG. 2 is an SEM photograph of the silicon wafer obtained in example 1;
FIG. 3 is a photomicrograph and PL-picture of the silicon wafer obtained in comparative example 5;
FIG. 4 is an SEM image of a silicon wafer obtained in comparative example 5;
FIG. 5 is a photomicrograph and PL-picture of the silicon wafer obtained in comparative example 6;
FIG. 6 is an SEM image of the silicon wafer obtained in comparative example 6.
Detailed Description
In order that the invention may be more fully understood, a more particular description of the invention will now be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is to be understood that these embodiments are provided so that this disclosure will be thorough and complete.
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. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
An embodiment of the present invention provides a silicon wafer texturing and cleaning method, including the following steps S1 to S8.
S1: and roughly polishing the silicon wafer.
The rough polishing treatment is used for removing a damaged layer on the surface of the silicon wafer. In a specific example, the single-side etching depth of the silicon wafer is about 4 μm.
In some of these embodiments, the reagent used in the rough polishing process is an alkaline solution, such as an aqueous solution of a soluble alkali metal hydroxide salt, e.g., sodium hydroxide, potassium hydroxide, etc.
Further, the aqueous solution of the soluble alkali metal hydroxide salt has a mass concentration of the soluble alkali metal hydroxide salt of 5% to 10%.
Further, the agent used for the rough polishing treatment is an aqueous solution of at least one of sodium hydroxide and potassium hydroxide.
In some embodiments, the temperature of the rough polishing treatment is 75-90 ℃, the time is 120-200 s, and the circulation flow is 30-40L/min. Further, the temperature may be 75 ℃, 80 ℃, 85 ℃, 90 ℃, the time may be 120s, 130s, 140s, 150s, 160s, 170s, 180s, 190s, 200s, and the circulation flow rate may be 30L/min, 35L/min, 40L/min. In a specific example, the temperature of the rough polishing treatment is 80 ℃, the time is 180s, and the circulation flow rate is 35L/min.
S2: and (4) carrying out acid washing treatment on the silicon wafer obtained in the step S1. Wherein the pickling solution used for pickling treatment contains ozone, HCl and HF.
Step S2 acid-washing and ozone-cleaning the silicon wafer obtained in step S1 with ozone (O)3) The surface of the roughly polished silicon chip is oxidized to form compact SiO on the surface of the silicon chip2Oxide film ofA considerable amount of metal impurities can be removed. The HCl contained in the pickling solution has the double functions of adjusting the pH value of the pickling solution and removing heavy metal ions, and the HF contained in the pickling solution can effectively corrode the silicon oxide layer, so that the silicon oxide layer, organic matters and metal stains are removed. The whole process generates a chemical reaction equation:
2O3+3Si＝3SiO2；
SiO2+4HF＝SiF4+2H2O；
SiO2+6HF＝H2SiF6+2H2o (in excess of HF).
In some of these embodiments, the concentration of ozone in the pickle liquor is 30 to 50ppm, such as 30ppm, 32ppm, 35ppm, 38ppm, 40ppm, 45ppm, 50 ppm. The ozone with the optimal concentration has extremely strong oxidation potential, so that the ozone has extremely strong capability of removing organic matters and metal pollution, and simultaneously has better oxidation effect on the surface of the roughly polished silicon wafer.
Further, the pickling solution contains 0.02 to 0.05% by mass of HCl, for example, 0.02%, 0.03%, 0.04%, 0.05%; the mass concentration of HF is 0.9% to 1.2%, for example, 0.9%, 1.0%, 1.1%, 1.2%.
In some embodiments, the temperature of the acid washing treatment is 20-30 ℃, the time is 180-280 s, and the circulation flow rate is 30-40L/min. Further, the temperature may be 20 ℃, 25 ℃, 30 ℃, the time may be 180s, 190s, 200s, 210s, 220s, 230s, 240s, 250s, 260s, 270s, 280s, and the circulation flow rate may be 30L/min, 35L/min, 40L/min. In a specific example, the temperature of the pickling treatment is 25 ℃, the time is 240s, and the circulation flow rate is 35L/min.
S3: the silicon wafer obtained in step S2 was subjected to a first alkali washing treatment.
The step S3 is for removing organic contamination, particles, metals, etc. on the surface of the silicon wafer.
Further, the first alkali wash used in the first alkali washing treatment contains a soluble alkali metal hydroxide salt and H2O2In particular soluble alkali metal hydroxides and H2O2Is dissolved in waterAnd (4) liquid. After the step S2 of using ozone and acid washing, the step S3 of using a solution containing soluble alkali metal hydroxide salt and H2O2The aqueous solution of (A) is subjected to alkaline washing due to H2O2The organic matter on the surface of the silicon wafer is decomposed into CO2、H2O is removed and the surface of the silicon wafer is H2O2Oxidation to form an oxide film, which is corroded by soluble alkali metal hydroxide such as KOH, and the oxide film is oxidized immediately after corrosion, and the oxidation and corrosion are repeated, so that particles attached to the surface of the silicon wafer fall into the cleaning solution along with the corrosion layer to be removed; the combination of step S2 and step S3 greatly enhances the cleaning ability of the silicon wafer surface, and further omits the post-cleaning step between the smoothing treatment of step S6 and the surface passivation treatment of step S7, so that hydrogen peroxide (H) can be used2O2) And the consumption of hydrochloric acid (HCl) is greatly reduced, and the production cost is saved.
In some embodiments, the first alkaline washing solution contains soluble alkali metal hydroxide salt with a mass concentration of 0.9-1.2%, and H2O2The mass concentration of (A) is 4-5%. Further, the soluble alkali metal hydroxide salt may be at least one of sodium hydroxide and potassium hydroxide, preferably sodium hydroxide.
In some embodiments, the temperature of the first alkali washing treatment is 60-70 ℃, the time is 210-280 s, and the circulation flow rate is 35-45L/min. Further, the temperature can be 60 ℃, 65 ℃ and 70 ℃, the time can be 210s, 220s, 230s, 240s, 250s, 260s, 270s and 280s, and the circulating flow rate is 35L/min, 40L/min and 45L/min. In a specific example, the temperature of the first alkaline washing treatment is 65 ℃, the time is 240s, and the circulation flow rate is 40L/min.
S4: and (4) performing texturing treatment on the silicon wafer obtained in the step S3.
The texturing treatment refers to the treatment of concave-convex surfaces (pyramid textured surfaces) on the surfaces of the silicon wafers, so that the refraction times of light on the surfaces of the solar cells are increased, the absorption of the solar cells on the light is facilitated, and the maximum utilization rate of the solar cells on the solar value is achieved.
For HJT cells, the texturing process is performed using an alkaline solution. The action principle of texture surface making is that when a monocrystalline silicon piece is corroded in an alkaline solution with a certain concentration, the monocrystalline silicon piece is anisotropic, the corrosion rates in different crystal directions are different, and the monocrystalline silicon piece is put into the alkaline solution to be corroded, so that a plurality of fine pyramid-shaped texture surfaces can be generated on the surface of the silicon piece. The chemical reaction equation for this process is:
Si+2KOH+H2O＝K2SiO3+2H2↑。
the texturing treatment can improve the light trapping effect of the silicon wafer, reduce reflection, increase absorption of light and reduce the surface reflectivity of the silicon wafer. In a specific example, a KOH etching solution is used to perform anisotropic etching on an N-type silicon wafer, so as to etch a Si (100) crystal face into a tetragonal pyramid structure ("pyramid structure") of a Si (111) crystal face, that is, a textured surface is formed on the surface of the silicon wafer, which can reduce the reflectivity of the surface of the silicon wafer to below 12.5%, thereby generating more photon-generated carriers and forming a clean silicon wafer surface.
In a specific example, the silicon wafer obtained in step S4 has a single-side etch depth increased to about 4 μm, and the reflectivity is about 9%.
Further, the alkali solution may be an aqueous solution of a soluble alkali metal hydroxide salt such as sodium hydroxide or potassium hydroxide. Further, the mass concentration of the soluble alkali metal hydroxide salt in the alkali solution is 1.1% to 1.5%, for example, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%. Furthermore, the alkali solution also contains an additive, and the mass concentration of the additive is 0.5-0.6%.
In some embodiments, the texturing treatment temperature is 75-90 ℃, the time is 500-700 s, and the circulation flow rate is 20-30L/min. Further, the temperature may be 75 ℃, 80 ℃, 85 ℃, 90 ℃, the time may be 500s, 530s, 550s, 580s, 600s, 630s, 650s, 680s, 700s, and the circulation flow rate may be 30L/min, 35L/min, 40L/min. In a specific example, the temperature of the texturing treatment is 80 ℃, the time is 600s, and the circulation flow rate is 25L/min.
S5: the silicon wafer obtained in step S4 was subjected to a second alkali washing treatment.
The step S5 is for removing organic contamination, particles, metals, etc. on the surface of the silicon wafer.
In some of these embodiments, the second alkaline washing solution used in the second alkaline washing treatment comprises a soluble alkali metal hydroxide salt and H2O2In particular soluble alkali metal hydroxides and H2O2An aqueous solution of (a).
Further, in the second alkali wash, the mass concentration of the soluble alkali metal hydroxide salt is 0.9% to 1.2%, and H is2O2The mass concentration of (A) is 4-5%.
In some embodiments, the second alkali washing treatment is performed at a temperature of 60-70 ℃ for 210-280 s, and the circulation flow rate is 35-45L/min. Further, the temperature can be 60 ℃, 65 ℃ and 70 ℃, the time can be 210s, 220s, 230s, 240s, 250s, 260s, 270s and 280s, and the circulating flow rate is 35L/min, 40L/min and 45L/min. In a specific example, the temperature of the second alkali washing treatment was 65 ℃, the time was 240s, and the circulation flow rate was 40L/min.
S6: the silicon wafer obtained in step S5 is subjected to a rounding process.
The smoothing step of step S6 is to polish the bottom and tip of the pyramid to smooth the top and bottom of the pyramid, facilitating the subsequent CVD deposition.
In some of these embodiments, the reagents used for the rounding process include HCl and HF. Furthermore, in the reagent used for the smoothing treatment, the mass concentration of HCl is 0.02-0.05%, and the mass concentration of HF is 0.2-0.5%.
Further, the reagent used for the smoothing treatment also contains ozone. Further, the concentration of ozone in the reagent is 40-50 ppm, such as 40ppm, 45ppm, 50 ppm.
Furthermore, the temperature of the smoothing treatment is 20-30 ℃, the time is 180-240 s, and the circulation flow is 35-45L/min. Further, the temperature can be 20 ℃, 25 ℃ and 30 ℃, the time can be 180s, 190s, 200s, 210s, 220s, 230s and 240s, and the circulating flow rate can be 35L/min, 40L/min and 45L/min. In a specific example, the temperature of the rounding off is 25 ℃, the time is 200s, and the circulation flow rate is 40L/min.
S7: and (4) carrying out surface passivation treatment on the silicon wafer obtained in the step S6.
In some of these embodiments, the agent used for the passivation process is a hydrofluoric acid solution. The step S7 mainly has the effect that HF treatment removes the oxide layer of silicon, and dangling bonds on the surface of the silicon wafer are saturated by hydrogen, so that the silicon wafer obtains good passivation performance.
Further, the mass concentration of HF in the hydrofluoric acid solution is 4.5-5.5%.
In some embodiments, the passivation temperature is 20-30 ℃, the time is 180-240 s, and the circulation flow rate is 50-70L/min. Further, the temperature can be 20 ℃, 25 ℃ and 30 ℃, the time can be 180s, 190s, 200s, 210s, 220s, 230s and 240s, and the circulating flow rate can be 50L/min, 55L/min, 60L/min, 65L/min and 70L/min. In a specific example, the passivation temperature is 25 ℃, the time is 210s, and the circulation flow rate is 60L/min.
Further, the step of acid cleaning or alkali cleaning is not included between the step of rounding at step S6 and the step of passivation at step S7.
S8: the silicon wafer obtained in step S7 is subjected to a drying treatment.
Further, the drying treatment can adopt drying at the temperature of 55-75 ℃ for 800-1000 s.
It is understood that, in addition to step S8, any of the above separate steps may be followed by a water rinsing step to remove residues of reagents used in a process on the surface of the silicon wafer. Preferably, the cleaning is performed using a pure water or deionized water machine.
According to the texturing and cleaning method for the silicon wafer, the silicon wafer is subjected to rough polishing treatment, acid washing treatment, first alkali washing treatment, texturing treatment, second alkali washing treatment, smoothing treatment, passivation treatment and drying treatment in sequence, and particularly the acid washing treatment and the first alkali washing treatment which are sequentially carried out are added between the rough polishing treatment and the texturing treatment; acid cleaning treatment silicon after rough polishing treatment by ozoneThe oxidation of the surface of the silicon chip can form compact SiO on the surface of the silicon chip2The oxide film can remove a part of metal impurities, HCl has double functions of adjusting the pH value of the pickling solution and removing heavy metal ions, and HF can effectively corrode the silicon oxide layer, so that the silicon oxide layer, organic matters and metal stains are removed. Followed by a first alkaline washing treatment with a mixture of a soluble alkali metal hydroxide salt and H2O2The aqueous solution is subjected to alkaline washing, the combination of the aqueous solution and the alkaline washing can greatly improve the cleaning effect, and further, the post-cleaning step between the subsequent smoothing treatment and the passivation treatment can be omitted, so that hydrogen peroxide (H) is obtained2O2) And the consumption of hydrochloric acid (HCl) is greatly reduced, the production cost is saved, and meanwhile, the process flow efficiency has no obvious difference.
The invention also provides a preparation method of the crystal silicon solar cell, which comprises the steps of the texturing and cleaning method of the silicon wafer, and also comprises the steps of depositing an amorphous silicon film, depositing a transparent conductive oxide film and manufacturing a metal electrode which are sequentially carried out after texturing and cleaning.
In some embodiments, the crystalline silicon solar cell is an HJT cell. Specifically, the crystalline silicon solar cell comprises the following steps:
depositing a very thin intrinsic amorphous silicon film (i-a-Si: H) and a p-type amorphous silicon film (p-a-Si: H) on the front surface of an N-type monocrystalline silicon wafer (c-Si), and then depositing a very thin intrinsic amorphous silicon film (i-a-Si: H) and an N-type amorphous silicon film (N-a-Si: H) on the back surface of the silicon wafer to form a back surface field; depositing transparent oxide conductive thin films (TCO) on two sides of the silicon wafer, wherein the TCO can reduce series resistance during current collection and can also play a role in reducing reactions like a silicon nitride layer on a crystalline silicon cell; and finally, manufacturing a metal electrode on the TCO.
In order to make the objects, technical solutions and advantages of the present invention more concise and clear, the present invention is described with the following specific embodiments, but the present invention is by no means limited to these embodiments. The following described examples are only preferred embodiments of the present invention, which can be used to describe the present invention and should not be construed as limiting the scope of the present invention. It should be understood that any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
In order to better illustrate the invention, the following examples are given to further illustrate the invention. The following are specific examples.
In each of the examples and comparative examples, a YAC machine was used to texture silicon wafers of HJT heterojunction solar cells.
Example 1
S1: and (6) rough polishing. The reagent used for rough polishing is KOH aqueous solution with the mass concentration of 5%, the temperature is set to 80 ℃, the time is 180s, and the circulating flow is kept at about 35L/min. The method has the function of removing a damaged layer on the surface of the silicon wafer, and the single-side corrosion depth of the silicon wafer is about 4 mu m.
S2: acid washing (ozone cleaning). The acid wash had a HCl mass concentration of 0.02%, a HF mass concentration of 1%, and ozone (O)3) The concentration was set at 30ppm, the temperature at 25 ℃ and the time at 240s, 35L/min.
S3: precleaning (first caustic wash). The first alkaline washing solution is KOH or H2O2Wherein the KOH mass concentration is 1.1%, H2O2The mass concentration of (A) is 4.5%, the temperature is set to 65 ℃, the time is set to 240s, and the circulating flow is kept at about 40L/min. The function is to remove organic dirt, particles, metal and the like on the surface of the silicon chip.
S4: and (5) making wool. The adopted reagent is an aqueous solution of KOH and an additive, wherein the mass concentration of the KOH is 1.5 percent, the mass concentration of ADD (additive) is 0.6 percent, the temperature is set to 80 ℃, the time is set to 600s, and the circulating flow is kept at about 25L/min. In this step, the etching depth of the single surface of the silicon wafer is deepened by about 4 μm, and the reflectivity is about 9%.
S5: pre-wash (second alkaline wash). The second alkaline washing solution is KOH or H2O2Wherein the KOH mass concentration is 1.1%, H2O2The mass concentration of the silicon wafer is 4.5 percent, the temperature is set to be 65 ℃, the time is set to be 240s, the circulating flow is kept to be about 40L/min, and the silicon wafer surface cleaning agent is used for removing organic dirt, particles, metals and the like on the silicon wafer surface.
S6: round (T-shaped)And (4) performing slipping treatment. The mass concentration of HCl in the used reagent is 0.02%, the mass concentration of HF is 0.3%, and ozone (O)3) The concentration is set to be 45ppm, the temperature is set to be 25 ℃, the time is set to be 200s, and the circulating flow is set to be about 40L/min; the function of the method is to polish the bottom and the tip of the pyramid, thereby facilitating the subsequent CVD coating deposition.
S7: and (5) surface passivation. The used reagent is HF aqueous solution, the mass concentration of HF is 5%, the temperature is set at 25 ℃, the time is 210s, and the circulating flow is kept at about 60L/min. The method mainly has the function of removing the oxide layer of silicon, and the saturated dangling bond plays a role in surface passivation.
And S8, dewatering and drying. The drying temperature is 65 ℃ and the drying time is 800 s.
It is understood that, in addition to step S8, any of the above separate steps may be followed by a water rinsing step to remove residues of reagents used in a process on the surface of the silicon wafer. Preferably, the cleaning is performed using a pure water or deionized water machine.
Through the steps, the silicon wafer with uniform texture surface, the weight of which is reduced to about 0.85g and the reflectivity of which is about 9.5 percent, is obtained.
Examples 2 to 4
Examples 2 to 4 are the same as example 1 except that the concentration of the reagent used in each step and the temperature, time and flow rate of the treatment were adjusted, as shown in table 1.
Comparative example 1
Comparative example 1 is essentially the same as example 1 except that: the step of pickling of step S2 in example 1 was omitted, while a post-cleaning step was added between the steps of rounding and surface passivation.
The specific procedure of comparative example 1 was as follows:
s1: and (6) rough polishing. The reagent used for rough polishing is KOH aqueous solution with the mass concentration of 5%, the temperature is set to 80 ℃, the time is 180s, and the circulating flow is kept at about 35L/min. The method has the function of removing a damaged layer on the surface of the silicon wafer, and the single-side corrosion depth of the silicon wafer is about 4 mu m.
S2: and (4) pre-cleaning. The first alkaline washing solution is KOH or H2O2In which the KOH has a massConcentration 1.1%, H2O2The mass concentration of (A) is 4.5%, the temperature is set to 65 ℃, the time is set to 240s, and the circulating flow is kept at about 40L/min. The function is to remove organic dirt, particles, metal and the like on the surface of the silicon chip.
S3: and (5) making wool. The adopted reagent is an aqueous solution of KOH and an additive, wherein the mass concentration of the KOH is 1.5 percent, the mass concentration of ADD (additive) is 0.6 percent, the temperature is set to 80 ℃, the time is set to 600s, and the circulating flow is kept at about 25L/min. In this step, the etching depth of the single surface of the silicon wafer is deepened by about 4 μm, and the reflectivity is about 9%.
S4: and (6) cleaning. The second alkaline washing solution is KOH or H2O2Wherein the KOH mass concentration is 1.1%, H2O2The mass concentration of the silicon wafer is 4.5 percent, the temperature is set to be 65 ℃, the time is set to be 240s, the circulating flow is kept to be about 40L/min, and the silicon wafer surface cleaning agent is used for removing organic dirt, particles, metals and the like on the silicon wafer surface.
S5: and (6) smoothing treatment. The mass concentration of HCl in the used reagent is 0.02%, the mass concentration of HF is 0.3%, and ozone (O)3) The concentration is set to be 45ppm, the temperature is set to be 25 ℃, the time is set to be 200s, and the circulating flow is set to be about 40L/min; the function of the method is to polish the bottom and the tip of the pyramid, thereby facilitating the subsequent CVD coating deposition.
S6: and (5) cleaning. The reagents used are HCl and H2O2In which HCl has a mass concentration of 6%, H2O2The mass concentration of (A) is 5%, the temperature is set to 65 ℃, the time is set to 240s, and the circulating flow is about 40L/min. The purpose is to remove some of the metal ions.
S7: and (5) surface passivation. The used reagent is HF aqueous solution, the mass concentration of HF is 5%, the temperature is set at 25 ℃, the time is 210s, and the circulating flow is kept at about 60L/min. The method mainly has the function of removing the oxide layer of silicon, and the saturated dangling bond plays a role in surface passivation.
And S8, dewatering and drying. The drying temperature is 65 ℃ and the drying time is 800 s. It is understood that, in addition to step S8, any of the above separate steps may be followed by a water rinsing step to remove residues of reagents used in a process on the surface of the silicon wafer. Preferably, the cleaning is performed using a pure water or deionized water machine.
Through the steps, the silicon wafer with uniform texture surface, the weight of which is reduced to about 0.85g and the reflectivity of which is about 9.5 percent, is obtained.
Comparative examples 2 to 4
The method is respectively basically the same as the embodiments 2-4, and the differences are only that: the step of pickling of step S2 in example 1 was omitted, while a post-cleaning step was added between the steps of rounding and surface passivation. The conditions of the post-cleaning step therein were the same as in comparative example 1.
Comparative example 5
Comparative example 5 is essentially the same as example 1, except that: the ozone cleaning of step S2 in example 1 is exchanged with the pre-cleaning of step S3; namely: comparative example 5 after the rough polishing treatment, the preliminary cleaning step was performed using the same conditions as in example 1, and then the ozone cleaning step was performed using the same conditions as in example 1.
Comparative example 6
Comparative example 6 is essentially the same as example 1, except that: the reagent for ozone cleaning in step S2 contains no HF.
Some of the process parameters of the above examples and comparative examples are shown in table 1 below:
TABLE 1
The production efficiency of the texturing cleaning process of each embodiment and the comparative example is counted, and no obvious difference exists; further, the total consumption of the chemical agents used in each example and comparative example was counted, and the unit consumption of a single wafer corresponding to each chemical was obtained based on the number of wafers produced correspondingly, as shown in table 2 below.
Wherein hydrogen peroxide and saltThe acid is the H used in each step2O2Total amount of starting materials corresponding to HCl, wherein H2O2The mass concentration of the initial raw material hydrogen peroxide is 30%, and the mass concentration of the initial raw material hydrochloric acid corresponding to HCl is 37%. The unit consumption in table 2 is the unit consumption corresponding to the maximum productivity (5000 pcs per hour) of a single shift.
TABLE 2
From the above table, compared with the process flow of the comparative example 1, the unit consumption of hydrogen peroxide of the example 1 is reduced from 7.3832mL/pcs to 4.1390mL/pcs, and the reduction amplitude is up to 43.9%; the unit consumption of hydrochloric acid is reduced from 1.2857mL/pcs to 0.0658 mL/pcs; the reduction amplitude is as high as 94.9%.
Compared with the process flow of the comparative example 2, the unit consumption of the hydrogen peroxide in the example 2 is reduced from 7.8168mL/pcs to 4.5600mL/pcs, and the reduction amplitude is up to 41.6 percent; the unit consumption of hydrochloric acid is reduced from 1.2898mL/pcs to 0.3798 mL/pcs; the reduction amplitude is up to 70.5%.
Compared with the process flow of the comparative example 3, the unit consumption of the hydrogen peroxide in the example 3 is reduced from 7.5702mL/pcs to 4.3133mL/pcs, and the reduction amplitude is up to 43 percent; the unit consumption of hydrochloric acid is reduced from 1.0408mL/pcs to 0.1308 mL/pcs; the reduction amplitude is up to 87.4%.
Compared with the process flow of the comparative example 4, the unit consumption of the hydrogen peroxide of the example 4 is reduced from 7.7518mL/pcs to 4.4950mL/pcs, and the reduction amplitude is up to 42%; the unit consumption of the hydrochloric acid is reduced from 1.2275mL/pcs to 0.3175 mL/pcs; the reduction amplitude is as high as 74.1%.
Therefore, the method for cleaning wool can make hydrogen peroxide (H) be used2O2) And the consumption of hydrochloric acid (HCl) is greatly reduced, and the production cost is saved.
The actual photographs, PL diagrams and SEM diagrams of the silicon wafers prepared in example 1 and comparative examples 5 to 6 are shown in FIGS. 1 to 6, respectively. In fig. 1, 3 and 5, a is a photograph of a real object and b is a PL diagram.
Photoluminescence (PL) is a luminescence phenomenon of a semiconductor material, and refers to a process in which electrons in a semiconductor are excited after absorbing external photons, the electrons in an excited state are unstable and can jump to a lower energy level to release energy in the form of light radiation, and the frequency, phase, amplitude, direction, polarization state and the like of luminescence carry a large amount of basic information of the material, so that the PL is a very important method for detecting an electronic structure of the material. In the photovoltaic industry, PL is used for detecting defects such as scratches, subfissure of a cell, surface pollution, black spots and black spots in the production process of the cell, and the defects limit the photoelectric conversion efficiency and the service life of the cell.
As can be seen from fig. 1 and 2, the appearance and PL of example 1 were normal, and the pile surface was uniform.
As can be seen from fig. 3 and 4, comparative example 5 had a dirty appearance and had a pile surface abnormality at the edge position.
As can be seen from FIGS. 5 and 6, in the appearance of comparative example 6, the contact part of the silicon wafer and the flower basket carrier has latch marks, the PL latch marks are obvious, and the suede of the latch positions is abnormal. In comparative example 6, since the reagent for ozone cleaning in step S2 contains no HF, a thick oxide layer formed on the surface of the silicon wafer after the ozone oxidation in step S2 is not removed in time, and since the reaction space at the contact position of the silicon wafer and the basket is narrow, a small amount of oxide at the contact position of the silicon wafer and the basket is not completely removed and attached to the surface when a series of steps are performed subsequently, a latch mark occurs, the appearance is not easily seen, but PL is significant, and the conversion efficiency of the cell is affected.
In conclusion, the cleaning effect of example 1 is the best.
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 patent of the invention is subject to the appended claims, and the description can be used for explaining the contents of the claims.
Claims (13)
1. The texturing and cleaning method for the silicon wafer is characterized by comprising the following steps:
carrying out rough polishing treatment, acid washing treatment, first alkali washing treatment, texturing treatment, second alkali washing treatment, smoothing treatment, passivation treatment and drying treatment on a silicon wafer in sequence;
the pickling solution used for pickling treatment contains ozone, HCl and HF;
the first alkaline washing solution used for the first alkaline washing treatment contains soluble alkali metal hydroxide salt and H2O2。
2. The method according to claim 1, wherein the concentration of ozone in said pickling solution is 30 to 50 ppm; and/or
In the pickling solution, the mass concentration of HCl is 0.02-0.05%, and the mass concentration of HF is 0.9-1.2%.
3. The method according to claim 1, wherein the pickling is performed at a temperature of 20 to 30 ℃ for 180 to 280 seconds, and a circulation flow rate of 30 to 40L/min.
4. The method according to claim 1, wherein the first alkaline solution contains the soluble alkali metal hydroxide salt in a mass concentration of 0.9% to 1.2% and H2O2The mass concentration of (A) is 4-5%.
5. The method according to claim 1, wherein the first alkali washing treatment is performed at a temperature of 60 to 70 ℃ for 210 to 280 seconds, and a circulation flow rate is 35 to 45L/min.
6. The etching cleaning method according to any one of claims 1 to 5, wherein the agent for the rough polishing treatment is an alkali solution; and/or
The temperature of the rough polishing treatment is 75-90 ℃, the time is 120-200 s, and the circulation flow is 30-40L/min.
7. The method according to any one of claims 1 to 5, wherein the agent used in the texturing treatment is an alkaline solution; and/or
The temperature of the texturing treatment is 75-90 ℃, the time is 500-700 s, and the circulation flow is 20-30L/min.
8. The method according to any one of claims 1 to 5, wherein the second alkali washing solution used in the second alkali washing treatment contains a soluble alkali metal hydroxide salt and H2O2。
9. The method according to claim 8, wherein the second alkaline washing solution contains the soluble alkali metal hydroxide salt in a concentration of 0.9 to 1.2% by mass, and H2O2The mass concentration of (A) is 4-5%.
10. The etching cleaning method according to any one of claims 1 to 5, wherein the second alkali washing treatment is carried out at a temperature of 60 to 70 ℃ for 210 to 280 seconds and at a circulation flow rate of 35 to 45L/min.
11. The method according to any one of claims 1 to 5, wherein the agent used for the smoothing treatment comprises HCl and HF; and/or
The temperature of the smoothing treatment is 20-30 ℃, the time is 180-240 s, and the circulation flow is 35-45L/min.
12. The etching cleaning method according to any one of claims 1 to 5, wherein the agent used for the passivation treatment is a hydrofluoric acid solution; and/or
The passivation treatment temperature is 20-30 ℃, the time is 180-240 s, and the circulation flow is 50-70L/min.
13. A preparation method of a crystalline silicon solar cell is characterized by comprising the following steps:
texturing a silicon wafer by the texturing cleaning method according to any one of claims 1 to 12;
and sequentially carrying out the steps of depositing an amorphous silicon film, depositing a transparent conductive oxide film and manufacturing a metal electrode on the textured silicon wafer.
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| CN114823951A (en) * | 2022-06-28 | 2022-07-29 | 晶科能源(海宁)有限公司 | Solar cell and photovoltaic module |
| CN114812121A (en) * | 2022-04-15 | 2022-07-29 | 通威太阳能（安徽）有限公司 | Silicon wafer drying device and drying method, and texturized silicon wafer post-treatment system and method |
| CN115312626A (en) * | 2022-08-31 | 2022-11-08 | 通威太阳能（安徽）有限公司 | Solar cell and preparation method thereof |
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| CN114812121A (en) * | 2022-04-15 | 2022-07-29 | 通威太阳能（安徽）有限公司 | Silicon wafer drying device and drying method, and texturized silicon wafer post-treatment system and method |
| CN114823951A (en) * | 2022-06-28 | 2022-07-29 | 晶科能源(海宁)有限公司 | Solar cell and photovoltaic module |
| CN115312626A (en) * | 2022-08-31 | 2022-11-08 | 通威太阳能（安徽）有限公司 | Solar cell and preparation method thereof |
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