Silicon wafer pretreatment method of monocrystalline silicon solar cell

Abstract

The invention belongs to the technical field of monocrystalline silicon solar cell silicon wafer cleaning, and relates to a silicon wafer pretreatment method of a monocrystalline silicon solar cell. The silicon wafer pretreatment method comprises the following steps: (1) primary water washing: putting a silicon wafer before texturing into water for primary water washing; (2) SC1 cleaning: soaking the silicon wafer subjected to primary water washing in an SC1 cleaning solution, and carrying out SC1 cleaning; (3) secondary water washing: putting the silicon wafer after SC1 cleaning into deionized water for secondary water washing; and (4) cleaning with an acidic ozone aqueous solution: soaking the silicon wafer subjected to secondary water washing in the acidic ozone aqueous solution for cleaning. According to the silicon wafer pre-cleaning method provided by the invention, the surface cleanliness of the silicon wafer before texturing is greatly improved under the condition of low hydrogen peroxide consumption, and the problem that the appearance reject ratio is high after texturing of a current rough polishing-free one-step texturing process is further solved.

Description

Technical Field

[0001] The invention belongs to the technical field of cleaning silicon slices of a monocrystalline silicon solar cell and relates to a silicon slice pretreatment method of a monocrystalline silicon solar cell. Background Art

[0002] In the manufacturing process of monocrystalline silicon solar cells, the process of alkali texturing on the surface of silicon wafers aims to form a pyramid-structured velvet surface on the surface of silicon wafers to improve the light absorption rate. In the process of cutting the upstream silicon ingots into silicon wafers, in addition to the mechanical damage to the surface of the silicon wafer caused by the cutting line, there will also be residual organic solvents such as degumming agents and coolants, as well as grease and metal ions. The influence of dust and particulate matter in the packaging process is also inevitable. Therefore, the cleanliness of the silicon wafer itself is poor, which directly restricts the consistency of the alkali texturing corrosion reaction in the manufacturing process of solar cells, and it is very easy to cause the local pyramid structure of the silicon wafer to be not formed, resulting in poor appearance.

[0003] In the existing conventional pretreatment method for silicon wafers, the first step is mostly a rough polishing process. This step mainly relies on the reaction of NaOH with silicon wafers to remove part of the raw material dirt. During the process, the silicon wafer is corroded and thinned, which will lead to a reduction in the overall thickness of the battery cell and affect the conversion efficiency of the battery cell. Based on this, the current one-step texturing process without rough polishing is being widely promoted and applied because of its advantages of low alkali consumption and high production efficiency, but the one-step texturing process without rough polishing has higher requirements for the cleanliness of the raw silicon wafer. The existing cleaning of silicon wafers mainly adopts the SC1 cleaning process. The SC1 cleaning process is a widely used wet chemical cleaning method, which is mainly used to remove particles, organic impurities and other pollution on the surface of silicon wafers. The SC1 cleaning solution is composed of NH4OH, H2O2 and H2O. Under the action of H2O2, a natural oxide film (SiO2) will be formed on the surface of the silicon wafer, making it hydrophilic, so that the cleaning solution can penetrate into the surface of the silicon wafer and between the particles. The natural oxide layer and Si on the surface of the silicon wafer are corroded by NH4OH, and the particles attached to the surface of the silicon wafer fall into the cleaning solution, thereby achieving the purpose of removing particles. However, silicon wafers pretreated with the existing SC1 cleaning process have appearance problems such as fingerprints and white spots after texturing, and the existing SC1 cleaning process has a high consumption of hydrogen peroxide, which has a negative impact on the biochemical system during wastewater treatment. Summary of the invention

[0004] The object of the present invention is to provide a silicon wafer pretreatment method for a monocrystalline silicon solar cell.

[0005] According to a first aspect of the present invention, the present invention provides a silicon wafer pretreatment method, the silicon wafer pretreatment method comprising the following steps:

[0006] (1) One water wash: Place the silicon wafer before texturing in water for one water wash;

[0007] (2) SC1 cleaning: immersing the silicon wafer after the first water washing in an SC1 cleaning solution for SC1 cleaning;

[0008] (3) Secondary water washing: placing the silicon wafer after cleaning with SC1 in water for secondary water washing;

[0009] (4) Cleaning with an acidic ozone aqueous solution: After the second water washing, the silicon wafer is immersed in an acidic ozone aqueous solution for cleaning.

[0010] Based on the existing SC1 cleaning process pre-treatment of silicon wafers with a one-step texturing process without rough polishing, which has problems with poor appearance after texturing such as fingerprints and white spots, and the high consumption of hydrogen peroxide in the SC1 cleaning process, the present application provides a silicon wafer pretreatment method for monocrystalline silicon solar cells, which is subjected to a series cleaning method including a primary water wash, SC1 wash, a secondary water wash and an acidic ozone aqueous solution wash before texturing, and the pre-cleaning method provided by the present application is used to pre-clean the silicon wafers before texturing with a one-step texturing process without rough polishing. Under the condition of low hydrogen peroxide usage, the surface cleanliness of the silicon wafers before texturing is greatly improved, thereby solving the problem of high appearance defect rate after texturing with the current one-step texturing process without rough polishing.

[0011] Specifically, in the pre-cleaning method provided in the present application, first, a water washing is performed on the silicon wafer before texturing, which helps to dissolve and remove pollutants such as grease and large particles of dust on the surface of the silicon wafer, and can remove part of the surface contamination of the silicon wafer; after the first water washing, the silicon wafer is further subjected to SC1 cleaning, and an oxidation corrosion reaction can be performed on the relatively clean surface of the silicon wafer, which is more helpful to remove various stubborn pollutants such as residual grease, metal ions, organic pollution, etc. attached to the silicon wafer; the silicon wafer after SC1 cleaning is subjected to a second water washing, and the alkaline solution carried by the silicon wafer in the SC1 cleaning process and the flower basket can be cleaned and diluted; the silicon wafer after the second water washing is cleaned with an acidic ozone aqueous solution, and the metal ions and organic pollution remaining or adsorbed on the surface during the SC1 oxidation corrosion reaction can be further cleaned by ozone oxidation, thereby finally achieving an excellent pre-cleaning effect on the silicon wafer before texturing in the one-step texturing process without rough polishing, and significantly improving the problem of a high appearance defective rate of silicon wafers after texturing in the one-step texturing process without rough polishing.

[0012] In some embodiments of the present invention, in step (1), the step of placing the silicon wafer before texturing in water for a water wash comprises: placing the silicon wafer before texturing in water for a water wash while turning on nitrogen bubbling. Turning on nitrogen bubbling helps to improve the uniformity of solution distribution and increase the flushing force of water, thereby improving the cleaning effect of the silicon wafer surface.

[0013] In some embodiments of the present invention, the temperature of the first water washing is 60-70°C. Specifically, the temperature of the first water washing can be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, 70°C or a range consisting of any two of the above values. In the pre-cleaning method provided in the present application, a temperature condition of 60-70°C is used for cleaning during the first water washing, which can pre-remove some stains and impurities carried on the surface of the silicon wafer to a certain extent. When the temperature is too low, the surface dirt cleaning effect is affected. When the temperature is too high, the temperature stability of the silicon wafer with liquid entering the SC1 tank in step (2) is affected, and the SC1 cleaning effect is reduced.

[0014] In some embodiments of the present invention, the time of the single water washing is 100-180 s. Specifically, the time of the single water washing can be 100 s, 110 s, 120 s, 130 s, 140 s, 150 s, 160 s, 170 s, 180 s or a range consisting of any two of the above values.

[0015] In some embodiments of the present invention, in step (1), in the one-time water washing step, the first amount of water added is 350±10L or 580L-620L. Specifically, in the one-time water washing step, the first amount of water added can be 340L, 345L, 350L, 355L, 360L, or a range consisting of any two of the above values. Or the first amount of water added can be 580L, 585L, 590L, 595L, 600L, 605L, 610L, 615L, 620L, or a range consisting of any two of the above values.

[0016] In some embodiments of the present invention, in the one water washing step, the water is preferably pure water or deionized water.

[0017] In some embodiments of the present invention, the single water washing step further includes: as the number of cleaning times increases, the water in the single water washing step needs to be supplemented, and the amount of water added in each round is determined according to the actual liquid level of the tank body to ensure that the water level is in a high liquid level state of the tank body.

[0018] In some embodiments of the present invention, in step (2), the SC1 cleaning solution comprises: an alkaline solution, a hydrogen peroxide solution and water; the initial volume ratio of the alkaline solution to the hydrogen peroxide solution and water is alkaline solution: hydrogen peroxide solution: water = 0.5-1.5:1.3-3:85-95. Specifically, the initial volume ratio of the alkaline solution to the hydrogen peroxide solution and water can be 0.5:1.3:85, 0.5:1.4:85, 0.5:1.5:85, 0.5:1.6:85, 0.5:1.7:85, 0.5:1.8:85, 0.5:1.9:85, 0.5:2.0:85, 0.5:2.1:85, 0.5:2.2:85, 0.5:2.25:85, 0.5:2.3:85, 0.5:2.35:85, 0.5:2.4:85, 0.5:2.45:85, 0.5:2.5:85, 0.5:2.6:85, 0.5:2.7:85 5, 0.5:2.8:85, 0.5:2.9:85, 0.5:3:85, 0.5:2.25:86, 0.5:2.25:87, 0.5:2.25:88, 0.5:2.25:89, 0.5:2.25:90, 0.5:2.25:91, 0.5:2.25:92, 0.5:2.25:93, 0.5:2.25:94, 0.5:2.25:95, 1:1.3:85, 1:1.4:85, 1:1.5:85, 1:1.6:85, 1:1.7:85, 1:1.8:85, 1:1.9:85, 1:2.0:85, 1 :2.1:85, 1:2.2:85, 1:2.25:85, 1:2.3:85, 1:2.35:85, 1:2.4:85, 1:2.45:85, 1:2.5:85, 1:2.6:85, 1:2.7:85, 1:2.8:85, 1:2.9:85, 1:3:85, 1:2.25:86, 1:2.25:87, 1:2.25:88, 1:2.25:89, 1:2.25:90, 1:2.25:91, 1:2.25:92, 1:2.25:93, 1:2.25:94, 1:2.25:95, 1.5:1.3: 85, 1.5:1.4:85, 1.5:1.5:85, 1.5:1.6:85, 1.5:1.7:85, 1.5:1.8:85, 1.5:1.9:85, 1.5:2.0:85, 1.5:2.1:85, 1.5:2.2:85, 1.5:2.25:85, 1.5:2.3:85, 1.5:2.35:85, 1.5:2.4:85, 1.5:2.45:85, 1.5:2.5:85, 1.5:2.6:85, 1.5:2.7:85, 1.5:2.8:85, 1.5:2.9:85, 1.5:3:85, 1.5:2.25:86, 1.5:2.25:87, 1.5:2.25:88, 1.5:2.25:89, 1.5:2.25:90, 1.5:2.25:91, 1.5:2.25:92, 1.5:2.25:93, 1.5:2.25:94, 1.5:2.25:95 or a range consisting of any two of the above values. .

[0019] In some embodiments of the present invention, the concentration of the alkaline solution is 40-50wt%, and the concentration of the hydrogen peroxide solution is 30-40wt%. Specifically, the concentration of the alkaline solution can be 40wt%, 41wt%, 42wt%, 43wt%, 44wt%, 45wt%, 46wt%, 47wt%, 48wt%, 49wt%, 50wt% or a range consisting of any two of the above values. Specifically, the concentration of the hydrogen peroxide solution can be 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, 40wt% or a range consisting of any two of the above values.

[0020] In some embodiments of the present invention, the alkaline solution is selected from at least one of NaOH, KOH or ammonia water.

[0021] In some embodiments of the present invention, in the SC1 cleaning step, the water is preferably pure water or deionized water.

[0022] In the SC1 solution system provided in the present application, an alkaline solution is mixed with hydrogen peroxide and water in a specific ratio to form an SC1 solution to clean the silicon wafer after a water wash. In this process, hydrogen peroxide as a strong oxidant can oxidize particles and organic contaminants on the surface of the silicon wafer, and the hydroxide in the solution can slightly corrode the oxide layer containing the contaminants, thereby further removing the contamination source on the surface of the silicon wafer.

[0023] In some embodiments of the present invention, in step (2), the SC1 cleaning step further comprises: in order to ensure the stability of the solution concentration in the tank as the number of cleaning times increases, it is necessary to add SC1 solution in the subsequent rounds of SC1 cleaning steps, and when the SC1 solution is added, the volume concentration ratio of hydrogen peroxide in the SC1 solution is higher than the concentration ratio at the time of initial addition.

[0024] In some embodiments of the present invention, when supplementing, the volume ratio of the alkali solution to the hydrogen peroxide solution and water in the SC1 solution is 0.5 to 1.5:3-7:60-70. Specifically, when supplementing, the volume ratio of the alkali solution to the hydrogen peroxide solution and water in the SC1 solution can be 0.5:3:60, 0.5:3.3:60, 0.5:3.5:60, 0.5:3.7:60, 0.5:3.9:60, 0.5:4.0:60, 0.5:4.5:60, 0.5:5.0:60, 0.5:5.5:60, 0.5:6:60, 0.5:6 .5:60、0.5:7:60、0.5:3.3:65、0.5:3.3:66、0.5:3.3:67、0.5:3.3:68、0.5:3.3:69、0.5:3.3:70、1:3:60、1:3.3:60、1:3.5:60、1:3.7:60、1:3.9:60、1:4.0:60、1:4.5:60、1:5.0: 60, 1:5.5:60, 1:6:60, 1:6.5:60, 1:7:60, 1:3.3:65, 1:3.3:66, 1:3.3:67, 1:3.3:68, 1:3.3:69, 1:3.3:70, 1.5:3:60, 1.5:3.3:60, 1.5:3.5:60, 1.5:3.7:60, 1.5:3.9:60, 1.5:4. 0:60, 1.5:4.5:60, 1.5:5.0:60, 1.5:5.5:60, 1.5:6:60, 1.5:6.5:60, 1.5:7:60, 1.5:3.3:65, 1.5:3.3:66, 1.5:3.3:67, 1.5:3.3:68, 1.5:3.3:69, 1.5:3.3:70 or a range consisting of any two of the above values. In the above scheme provided in the present application, the volume concentration of hydrogen peroxide is increased compared with the initial volume ratio during the addition because, in addition to the amount consumed by the chemical reaction, the easy decomposition property of hydrogen peroxide requires an increase in its supplementary amount, thereby achieving a corresponding cleaning effect.

[0025] In some embodiments of the present invention, the temperature of the SC1 cleaning is 60-75°C; the time of the SC1 cleaning is 100-180s. Specifically, the temperature of the SC1 cleaning can be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, 71°C, 72°C, 73°C, 74°C, 75°C or a range consisting of any two of the above values. The time of the SC1 cleaning can be 100s, 115s, 110s, 115s, 120s, 125s, 130s, 135s, 140s, 145s, 150s, 155s, 160s, 165s, 170s, 175s, 180s or a range consisting of any two of the above values.

[0026] In some embodiments of the present invention, in step (3), the temperature of the secondary water washing is room temperature. Specifically, the range of room temperature can be a room temperature range recognized based on common knowledge in the art, preferably, the range of room temperature can be 20-25°C. In the pre-cleaning method provided in the present application, room temperature conditions are used for cleaning during the secondary water washing, mainly to dilute and remove the hydrogen peroxide and sodium hydroxide solution carried on the surface of the silicon wafer, and to prevent the alkaline solution carried on the surface of the silicon wafer from further reacting with the silicon wafer under high temperature, thereby affecting the subsequent texturing effect of the silicon wafer.

[0027] In some embodiments of the present invention, the secondary washing time is 100-180s. Specifically, the secondary washing time is 100s, 105s, 110s, 115s, 120s, 125s, 130s, 135s, 140s, 145s, 150s, 155s, 160s, 165s, 170s, 175s, 180s or a range consisting of any two of the above values.

[0028] In some embodiments of the present invention, in the secondary water washing step, the water is preferably pure water or deionized water.

[0029] In some embodiments of the present invention, in step (4), the acidic ozone aqueous solution comprises an acid solution, ozone and water.

[0030] In some embodiments of the present invention, the volume ratio of the acid solution to water is 0.5-1.5:1500-2000. Specifically, the volume ratio of the acid solution to water can be 0.5:1500, 0.5:1600, 0.5:1700, 0.5:1800, 0.5:1900, 0.5:2000, 1:1500, 1:1600, 1:1700, 1:1800, 1:1900, 1:2000, 1.5:1500, 1.5:1600, 1.5:1700, 1.5:1800, 1.5:1900, 1.5:2000 or a range consisting of any two of the above values.

[0031] In some embodiments of the present invention, the concentration of the acid solution is 30-40wt%. Specifically, the concentration of the acid solution can be 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt%, 36wt%, 37wt%, 38wt%, 39wt%, 40wt% or a range consisting of any two of the above values.

[0032] In some embodiments of the present invention, the acid solution is an HCl solution.

[0033] In some embodiments of the present invention, the concentration of ozone in the acidic ozone aqueous solution is 20±10ppm. Specifically, the concentration of ozone in the acidic ozone aqueous solution is 10ppm, 11ppm, 12ppm, 13ppm, 14ppm, 15ppm, 16ppm, 17ppm, 18ppm, 19ppm, 20ppm, 21ppm, 22ppm, 23ppm, 24ppm, 25ppm, 26ppm, 27ppm, 28ppm, 29ppm, 30ppm or a range consisting of any two of the above values.

[0034] In the acidic ozone aqueous solution system provided in the present application, the acid solution, ozone and water are mixed in a specific ratio to form an acidic ozone aqueous solution to clean the silicon wafer after the second water washing, which can further remove the organic pollution residue on the surface of the silicon wafer, so as to provide a clean silicon surface for the subsequent texturing process and ensure a good texturing appearance effect. Ozone has better oxidizing properties than hydrogen peroxide, but its solubility in water is limited. The addition of an appropriate amount of hydrochloric acid can provide an acidic environment for ozone to increase its solubility in the aqueous solution, so as to achieve the effect of ozone oxidation to further remove organic pollution.

[0035] In some embodiments of the present invention, the acidic ozone aqueous solution is prepared by the following steps: adding an acidic solution to water to obtain a weak acid solution, and then introducing ozone gas into the weak acid solution to form the acidic ozone aqueous solution.

[0036] In some embodiments of the present invention, in the acidic ozone aqueous solution cleaning step, the water is preferably pure water or deionized water.

[0037] In summary, the present application includes at least one of the following beneficial technical effects:

[0038] Based on the existing SC1 cleaning process pre-treatment of silicon wafers with a one-step texturing process without rough polishing, which has problems with poor appearance after texturing such as fingerprints and white spots, and the high consumption of hydrogen peroxide in the SC1 cleaning process, the present application provides a silicon wafer pretreatment method for monocrystalline silicon solar cells, which is subjected to a series cleaning method including a primary water wash, SC1 wash, a secondary water wash and an acidic ozone aqueous solution wash before texturing, and the pre-cleaning method provided by the present application is used to pre-clean the silicon wafers before texturing with a one-step texturing process without rough polishing. Under the condition of low hydrogen peroxide usage, the surface cleanliness of the silicon wafers before texturing is greatly improved, thereby solving the problem of high appearance defect rate after texturing with the current one-step texturing process without rough polishing. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A process flow chart of pre-cleaning a silicon wafer before texturing provided in one embodiment of the present invention.

[0040] Figure 2 The appearance of a silicon wafer touched by hand before loading after the silicon wafer before texturing is pre-cleaned using the pre-cleaning method in one embodiment of the present invention.

[0041] Figure 3 The appearance of the silicon wafer touched by hand before loading after the silicon wafer before texturing is pre-cleaned by the pre-cleaning method in Comparative Example 1 of the present invention.

[0042] Figure 4 The appearance of the silicon wafer touched by hand before loading after the silicon wafer before texturing was pre-cleaned by the pre-cleaning method in Comparative Example 2 of the present invention.

[0043] Figure 5 The appearance of the silicon wafer touched by hand before loading after the silicon wafer before texturing was pre-cleaned by the pre-cleaning method in Comparative Example 3 of the present invention.

[0044] Figure 6 The appearance of the silicon wafer touched by hand before loading after the silicon wafer before texturing was pre-cleaned by the pre-cleaning method in Comparative Example 4 of the present invention.

[0045] Figure 7 The appearance of the silicon wafer touched by hand before loading after the silicon wafer before texturing was pre-cleaned by the pre-cleaning method in Comparative Example 5 of the present invention.

[0046] Figure 8The appearance of the silicon wafer touched by hand before loading after the silicon wafer before texturing was pre-cleaned by the pre-cleaning method in Comparative Example 6 of the present invention. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described below by specific embodiments, which do not limit the protection scope of the present invention. Some non-essential modifications and adjustments made by others based on the concept of the present invention still fall within the protection scope of the present invention.

[0048] Example 1

[0049] This embodiment provides a silicon wafer pretreatment method for a monocrystalline silicon solar cell, which is used for pre-cleaning the silicon wafer before texturing, and includes the following steps:

[0050] The first step is to provide the original single crystal silicon wafers, and the staff wearing PVC gloves take the wafers and put them into the flower basket;

[0051] The second step is hot water cleaning: the original silicon wafer is placed in 60℃ deionized water for 120s, while nitrogen bubbling is turned on for hot water cleaning. The first addition of deionized water is 580L, and then 5L is added each time. The clean state of the solution is ensured by replacing the old solution with the new solution. This step helps to dissolve and remove pollutants such as grease and large particles of dust on the surface of the silicon wafer, and can remove part of the surface contamination of the silicon wafer;

[0052] The third step is SC1 cleaning: the silicon wafers washed with hot water are immersed in a 65°C SC1 cleaning solution for 120 seconds for SC1 cleaning, and oxidation corrosion reaction is carried out on the relatively clean silicon wafer surface to remove various stubborn pollutants such as residual grease, metal ions, organic pollution, etc. attached to the silicon wafer; the SC1 cleaning solution used in this embodiment includes 48wt% NaOH, 37wt% hydrogen peroxide (H2O2), and deionized water (DI), wherein the initial volume ratio of NaOH:H2O2:DI is 1:2.25:90, and the volume ratio of NaOH:H2O2:DI in each round of SC1 cleaning solution added thereafter is 1:3.3:66, so as to ensure the stability of the solution concentration in the tank as the number of cleaning times increases;

[0053] Step 4: Wash with water at room temperature: Soak the silicon wafers cleaned by SC1 in a water tank at room temperature for 120 seconds to wash and dilute the alkaline solution carried by the silicon wafers in the SC1 cleaning process and the flower basket;

[0054] Step 5, HCl / DI / O3 cleaning: the silicon wafer washed with normal temperature water is placed in an acidic ozone aqueous solution (i.e., HCl / DI / O3 solution) at room temperature and soaked for 120 seconds. The metal ions and organic pollution remaining or adsorbed on the surface during the SC1 oxidation corrosion reaction are further cleaned by ozone oxidation. The cleaning solution is set to add a small amount of 37% HCl solution to pure water to obtain a weak acid solution, and then ozone gas is introduced into the solution to form an acidic ozone water mixture, wherein the volume ratio of HCl:DI is 1:1800; the O3 concentration is maintained at 20±3ppm;

[0055] Step 6: After cleaning with HCl / DI / O3, the silicon wafer is subjected to conventional alkali texturing, water washing, post-cleaning, acid washing, water washing and drying to obtain the silicon wafer after texturing. The appearance of the silicon wafer touched by hand before loading is as follows: Figure 2 As shown, Figure 2 The results shown show that the silicon wafer has no appearance defects such as fingerprints, white spots, etc.

[0056] Comparative Example 1

[0057] This comparative example is based on Example 1 and provides a silicon wafer pretreatment method for a monocrystalline silicon solar cell, which is used for pre-cleaning of silicon wafers before texturing. The difference from Example 1 is that the hot water cleaning in the second step and the HCl / DI / O3 cleaning in the fifth step in Example 1 are removed at the same time, and the remaining steps and parameters are the same. The specific steps are as follows:

[0058] The first step is to provide the original single crystal silicon wafers, and the staff wearing PVC gloves take the wafers and put them into the flower basket;

[0059] Step 2: Hot water cleaning: None;

[0060] The third step is SC1 cleaning: the original silicon wafer provided in the first step is not cleaned with hot water, but is directly placed in a 65°C SC1 cleaning solution and soaked for 120 seconds for SC1 cleaning; wherein the SC1 cleaning solution used includes 48wt% NaOH, 37wt% H2O2, and DI, wherein the initial volume ratio of NaOH:H2O2:DI is 1:2.25:90, and the volume ratio of NaOH:H2O2:DI in each round of SC1 cleaning solution added thereafter is 1:3.3:66, to ensure the stability of the solution concentration in the tank as the number of cleaning times increases;

[0061] The fourth step is to wash with water at room temperature. Soak the silicon wafer cleaned by SC1 in a water tank at room temperature for 120 seconds.

[0062] Step 5, HCl / DI / O3 cleaning: None;

[0063] Step 6: The silicon wafer obtained after washing with normal warm water is directly subjected to subsequent conventional alkali texturing, water washing, post-cleaning, acid washing, water washing, and drying without HCl / DI / O3 cleaning to obtain the silicon wafer after texturing. The appearance of the silicon wafer touched by hand before loading is as follows: Figure 3 As shown, Figure 3 As shown in the results, the white fingerprints on the silicon wafer are obvious and cannot be effectively removed.

[0064] Comparative Example 2

[0065] This comparative example is based on Example 1, and provides a silicon wafer pretreatment method for a monocrystalline silicon solar cell, which is used for pretreatment and cleaning of silicon wafers before texturing. The difference from Example 1 is that the second step (hot water cleaning) in Example 1 is removed, and the remaining steps and parameters are the same as those in Example 1. The specific steps are as follows:

[0066] The first step is to provide the original single crystal silicon wafers, and the staff wearing PVC gloves take the wafers and put them into the flower basket;

[0067] Step 2: Hot water cleaning: None;

[0068] Step 3: SC1 cleaning: The original single crystal silicon wafer provided in the first step is directly placed in a 65°C SC1 cleaning solution for 120 seconds without hot water cleaning for SC1 cleaning;

[0069] Step 4: Wash with water at room temperature: Soak the silicon wafers cleaned by SC1 in a water tank at room temperature for 120 seconds to wash and dilute the alkaline solution carried by the silicon wafers in the SC1 cleaning process and the flower basket;

[0070] Step 5: HCl / DI / O3 cleaning: Place the silicon wafer after washing with normal temperature water in a normal temperature HCl / DI / O3 solution and soak for 120 seconds;

[0071] Step 6: After cleaning with HCl / DI / O3, the silicon wafer is subjected to conventional alkali texturing, water washing, post-cleaning, acid washing, water washing and drying to obtain the silicon wafer after texturing. The appearance of the silicon wafer touched by hand before loading is as follows: Figure 4 As shown, Figure 4 As shown in the results, the degree of white fingerprints on the silicon wafer appearance has been reduced, but it is still obvious and cannot be effectively removed.

[0072] Comparative Example 3

[0073] This comparative example is based on Example 1, and provides a silicon wafer pretreatment method for a monocrystalline silicon solar cell, which is used for pretreatment and cleaning of silicon wafers before texturing. The difference from Example 1 is that the fifth step (HCl / DI / O3 cleaning) in Example 1 is removed, and the remaining steps and parameters are the same as those in Example 1. The specific steps are as follows:

[0074] The first step is to provide the original single crystal silicon wafers, and the staff wearing PVC gloves take the wafers and put them into the flower basket;

[0075] The second step is hot water cleaning: the original silicon wafer is placed in 60°C deionized water for 120 seconds, while nitrogen bubbling is turned on for hot water cleaning;

[0076] Step 3: SC1 cleaning: the silicon wafer obtained after hot water cleaning is placed in a 65°C SC1 cleaning solution and soaked for 120 seconds for SC1 cleaning;

[0077] Step 4: Wash with water at room temperature: Soak the silicon wafer cleaned with SC1 in a water tank at room temperature for 120 seconds;

[0078] Step 5, HCl / DI / O3 cleaning: None;

[0079] Step 6: The silicon wafer obtained after washing with normal warm water is directly subjected to subsequent conventional alkali texturing, water washing, post-cleaning, acid washing, water washing, and drying without HCl / DI / O3 cleaning to obtain the silicon wafer after texturing. The appearance of the silicon wafer touched by hand before loading is as follows: Figure 5 As shown, Figure 5 The results shown show that without HCl / DIO3 ozone cleaning, the double decontamination effect cannot be achieved and the fingerprints are still obvious on the surface.

[0080] Comparative Example 4

[0081] This comparative example is based on Example 1 and provides a silicon wafer pretreatment method for a monocrystalline silicon solar cell, which is used for pretreatment and cleaning of silicon wafers before texturing. The difference from Example 1 is that the normal temperature in the fourth step of normal temperature water washing in Example 1 is adjusted to 60°C water washing, and the remaining steps and parameters are the same as those in Example 1. The specific steps are as follows:

[0082] The first step is to provide the original single crystal silicon wafers, and the staff wearing PVC gloves take the wafers and put them into the flower basket;

[0083] The second step is hot water cleaning: the original silicon wafer is placed in 60°C deionized water for 120 seconds, while nitrogen bubbling is turned on for hot water cleaning;

[0084] Step 3: SC1 cleaning: the silicon wafer obtained after hot water cleaning is placed in a 65°C SC1 cleaning solution and soaked for 120 seconds for SC1 cleaning;

[0085] Step 4: Hot water cleaning: Soak the silicon wafer cleaned by SC1 in a 60°C water tank for 120 seconds;

[0086] Step 5: HCl / DI / O3 cleaning: After cleaning with 60°C hot water, place the silicon wafer in a room temperature HCl / DI / O3 solution and soak for 120 seconds.

[0087] Step 6: After cleaning with HCl / DI / O3, the silicon wafer is subjected to conventional alkali texturing, water washing, post-cleaning, acid washing, water washing and drying to obtain the silicon wafer after texturing. Figure 6 As shown, Figure 6 The results shown show obvious fingerprints on the outside. Hot water carries liquid into the HCl / DI / O3 tank, causing the temperature of the solution in the HCl / DI / O3 tank to rise and the ozone decomposition rate to accelerate, resulting in solution failure and weakened cleaning ability.

[0088] Comparative Example 5

[0089] This comparative example is based on Example 1, and provides a silicon wafer pretreatment method for a monocrystalline silicon solar cell, which is used for pretreatment and cleaning of silicon wafers before texturing. The difference from Example 1 is that the SC1 cleaning step in the second step and the HCl / DI / O3 cleaning step in the fifth step in Example 1 are exchanged in order, that is, room temperature cleaning + HCl / DI / O3 cleaning + hot water cleaning + SC1 cleaning + hot water cleaning steps, and the other parameters are the same as those in Example 1. The specific steps are as follows:

[0090] The first step is to provide the original single crystal silicon wafers, and the staff wearing PVC gloves take the wafers and put them into the flower basket;

[0091] The second step is room temperature water washing: the original silicon wafer is placed in room temperature ionized water for cleaning for 120 seconds, while nitrogen bubbling is turned on for room temperature water washing;

[0092] Step 3: HCl / DI / O3 cleaning: Place the silicon wafer after cleaning at room temperature in a room temperature HCl / DI / O3 solution and soak for 120 seconds;

[0093] Step 4: Hot water cleaning: Soak the silicon wafer cleaned with HCl / DI / O3 in a 60°C water tank for 120 seconds;

[0094] Step 5: SC1 cleaning: Soak the silicon wafers obtained after hot water cleaning in a 65°C SC1 cleaning solution for 120 seconds for SC1 cleaning; Soak the silicon wafers obtained after SC1 cleaning in a 60°C water tank for 120 seconds for a second hot water cleaning;

[0095] Step 6: After the silicon wafers are washed with hot water twice, they are subjected to conventional alkali texturing, water washing, post-cleaning, acid washing, water washing, and drying to obtain the silicon wafers after texturing. The appearance of the silicon wafers touched by hand before loading is as follows: Figure 7 As shown, Figure 7 The results shown have obvious air flow water mark problems.

[0096] Comparative Example 6

[0097] This comparative example is based on Example 1, and provides a silicon wafer pretreatment method for a monocrystalline silicon solar cell, which is used for pretreatment and cleaning of silicon wafers before texturing. The difference from Example 1 is that the ratio of NaOH to H2O2 and DI in the third step SC1 cleaning step in Example 1 is changed, and the rest is the same as Example 1. The specific steps are as follows:

[0098] The first step is to provide the original single crystal silicon wafers, and the staff wearing PVC gloves take the wafers and put them into the flower basket;

[0099] The second step is hot water cleaning: the original silicon wafer is placed in 60°C deionized water for 120 seconds, while nitrogen bubbling is turned on for hot water cleaning;

[0100] The third step is SC1 cleaning: the silicon wafer obtained after hot water cleaning is placed in a 65°C SC1 cleaning solution and soaked for 120 seconds for SC1 cleaning; wherein the SC1 cleaning solution used includes 48wt% NaOH, 37wt% H2O2, and DI, wherein the initial volume ratio of NaOH:H2O2:DI is 2:3:86 / or 5:8:95, and the volume ratio of NaOH:H2O2:DI in each round of SC1 cleaning solution added thereafter is 1:3.3:66, to ensure the stability of the solution concentration in the tank as the number of cleaning times increases;

[0101] Step 4: Wash with water at room temperature: Soak the silicon wafer cleaned with SC1 in a water tank at room temperature for 120 seconds;

[0102] Step 5: HCl / DI / O3 cleaning: Place the silicon wafer after washing with normal temperature water in a normal temperature HCl / DI / O3 solution and soak for 120 seconds;

[0103] Step 6: After cleaning with HCl / DI / O3, the silicon wafer is subjected to conventional alkali texturing, water washing, post-cleaning, acid washing, water washing and drying to obtain the silicon wafer after texturing. The appearance of the silicon wafer touched by hand before loading is as follows: Figure 8 As shown, Figure 8 As shown in the results, white fingerprints still remain on some parts of the silicon wafer.

[0104] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A silicon wafer pretreatment method, characterized in that: The silicon wafer pretreatment method comprises the following steps: (1) One water wash: Place the silicon wafer before texturing in water for one water wash; (2) SC1 cleaning: immersing the silicon wafer after the water washing in a SC1 cleaning solution for SC1 cleaning; (3) Secondary water washing: placing the silicon wafer after cleaning with SC1 in water for secondary water washing; (4) Cleaning with an acidic ozone aqueous solution: The silicon wafer after the second water washing is immersed in an acidic ozone aqueous solution for cleaning.

2. The silicon wafer pretreatment method according to claim 1, characterized in that: In step (1), the step of placing the silicon wafer before texturing in water for washing once comprises: placing the silicon wafer before texturing in water for washing once, while turning on nitrogen bubbling.

3. The silicon wafer pretreatment method according to claim 1, characterized in that: The temperature of the first water washing is 60-70°C; Preferably, the time of the single water washing is 100-180s.

4. The silicon wafer pretreatment method according to claim 1, characterized in that: In step (1), in the first water washing step, the first amount of water added is 350±10L or 580L-620L; Preferably, the one-time water washing step further comprises: as the number of cleaning times increases, the water in the one-time water washing step needs to be supplemented, and the amount of water added in each round is determined according to the actual liquid level of the tank body to ensure that the water level is in a high liquid level state of the tank body.

5. The silicon wafer pretreatment method according to claim 1, characterized in that: In step (2), the SC1 cleaning solution comprises: an alkaline solution, a hydrogen peroxide solution and water; the initial volume ratio of the alkaline solution to the hydrogen peroxide solution and water is alkaline solution: hydrogen peroxide solution: water = 0.5-1.5: 1.3-3: 85-95; Preferably, the concentration of the alkaline solution is 40-50wt%, and the concentration of the hydrogen peroxide solution is 30-40wt%; The alkaline solution is selected from at least one of NaOH, KOH or ammonia water.

6. The silicon wafer pretreatment method according to claim 1, characterized in that: In step (2), the SC1 cleaning step further includes: in order to ensure the stability of the solution concentration in the tank as the number of cleaning times increases, it is necessary to add the SC1 solution in the subsequent round of the SC1 cleaning step, and when the SC1 solution is added, the volume concentration ratio of the hydrogen peroxide in the SC1 solution is higher than the concentration ratio during the initial addition; preferably, when adding, the volume ratio of the alkaline solution to the hydrogen peroxide solution and water in the SC1 solution is 0.5-1.5:3-7:60-70.

7. The silicon wafer pretreatment method according to claim 1, characterized in that: The temperature of the SC1 cleaning is 60-75°C; The SC1 cleaning time is 100-180s.

8. The silicon wafer pretreatment method according to claim 1, characterized in that: In step (3), the temperature of the secondary water washing is room temperature; and the time of the secondary water washing is 100-180s.

9. The silicon wafer pretreatment method according to claim 1, characterized in that: In step (4), the acidic ozone aqueous solution comprises an acid solution, ozone and water; the volume ratio of the acid solution to water is 0.5-1.5:1500-2000; the concentration of the acid solution is 30-40wt%; and the concentration of ozone in the acidic ozone aqueous solution is 20±10ppm.

10. The silicon wafer pretreatment method according to claim 1, characterized in that: The acidic ozone aqueous solution is prepared by the following steps: adding an acidic solution into water to obtain a weak acid solution, and then introducing ozone gas into the weak acid solution to form the acidic ozone aqueous solution.

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