Cleaning method for reducing silicon material acid spots

Abstract

The invention discloses a cleaning method for reducing acid spots of a silicon material, which comprises the following steps: acid pickling: the silicon material is subjected to acid pickling, the acid liquor used in the acid pickling comprises hydrofluoric acid, nitric acid and water in a mass ratio of 1: (18-20): (9-10), the acid pickling temperature is 20-24 DEG C, and the acid pickling time is 40-200 seconds; and rinsing with warm water: rinsing the pickled silicon material with warm water at 25-80 DEG C, and then drying. In the application, the composition of the pickling solution is optimized, the pickling temperature is controlled, a complex is formed on the surface of the silicon material, and the complex is promoted to be separated from the silicon material during warm water rinsing, so that the acid consumption is reduced and the cost of the pickling solution per unit volume is reduced; after cleaning, the surface of the silicon material is glossy and free of acid spots, the one-time cleaning yield of the oxide layer is improved, the oxide layer removal efficiency is improved, and the surface quality of the silicon material is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of solar cells, and in particular to a cleaning method for reducing acid spots of silicon materials. Background Art

[0002] Currently, a mixed acid of hydrofluoric acid and nitric acid is usually used to chemically react with pollutants to clean the pollutants on the surface of silicon materials. The chemical reaction equation includes:

[0003] SiO2+6HF=H2SiF6+2H2O;

[0004] Si+4HNO3+18HF=3H2SiF6+4NO+8H2O;

[0005] In the pickling process, the volume ratio of hydrofluoric acid (electron pole, concentration 49%) and nitric acid (electron pole, concentration 69%) in the mixed acid is 1:7-9. The initial reaction time is long, the volume is relatively small, and the temperature is high. Under the current equipment status, in the initial stage of mixed acid configuration, the silicon material will react rapidly and violently when it contacts the mixed acid, and all kinds of oxides attached to the surface will be completely removed. After the process is completed, the silicon material needs to be taken out. The moment the silicon material is taken out of the acid tank, acid spots are easily generated on the surface, causing new oxide impurities to form on the surface. Therefore, each time the mixed acid is configured, a large amount of unqualified materials need to be reworked. The rework will result in a low cleaning pass rate, and the rework will increase production. The cost and manufacturing cost, and thus the cost of raw materials (silicon material loss) and auxiliary materials (water, electricity, compressed air, auxiliary tooling loss) also increase accordingly; at the same time, the surface quality of silicon materials is usually inspected manually, which is highly dependent on personnel. If the materials are not strictly selected and flow into the next process and then broken into the crystal pulling end, it will affect the quality of the crystal rod, reduce the minority carrier lifetime, increase the oxygen content, and affect the yield and crystal yield; during rework and transmission, the mutual friction between silicon materials and the contact with equipment may cause tiny damage and dust, resulting in certain losses. Repeated cleaning reaction and drying process, if the drying temperature of finely crushed materials is too high or the drying time is too long, it may also cause a small amount of silicon material to sublimate or pyrolyze and lose.

[0006] Therefore, a silicon material pickling method that can reduce acid spots and improve the cleaning pass rate is particularly necessary. Summary of the invention

[0007] The object of the present invention is to provide a cleaning method for reducing acid spots of silicon materials.

[0008] The present invention is achieved in that:

[0009] In a first aspect, the present invention provides a cleaning method for reducing acid spots on silicon materials, comprising:

[0010] Pickling: pickling the silicon material, wherein the acid solution used for pickling includes hydrofluoric acid, nitric acid and water in a mass ratio of 1: (18-20): (9-10), the pickling temperature is 20°C-30°C, and the pickling time is 40s-200s;

[0011] Rinse with warm water: use warm water at 25℃-80℃ to rinse the acid-washed silicon material with warm water, and then dry it.

[0012] In an optional embodiment, when the mass volume ratio of the pickled silicon material to the acid solution is 33kg / L-35kg / L, a hydrofluoric acid solution is added to the acid solution, and the mass fraction of hydrofluoric acid in the hydrofluoric acid solution is 45%-50%.

[0013] In an optional embodiment, the ratio of the volume of the added hydrofluoric acid solution to the volume of the acid solution is 0.33-0.35.

[0014] In an optional embodiment, when the mass volume ratio of the silicon material after pickling to the acid solution reaches 33kg / L-35kg / L, a mixed acid is added to the acid solution, wherein the mixed acid includes hydrofluoric acid, nitric acid and water in a mass ratio of 1:(5-6):(3-4).

[0015] In an optional embodiment, 0.9 ml-1.1 ml of mixed acid is added for every 0.3 kg of silicon material washed with acid.

[0016] In an optional embodiment, the silicon material is exposed to the air for less than 1 minute between acid washing and warm water rinsing.

[0017] In an optional embodiment, the pickling is carried out in a pickling tank, which is provided with a circulating liquid inlet and a circulating liquid outlet, a circulating pipe is connected between the circulating liquid inlet and the circulating liquid outlet, and a cooling water machine is provided on the circulating pipe, which cools the liquid passing through it to 14°C-18°C.

[0018] In an optional embodiment, after the warm water rinsing, the silicon material is also sequentially subjected to pure water rinsing, selective treatment and drying, and the selective treatment includes at least one of bubbling rinsing, wind shear drying and high-temperature drainage.

[0019] In an optional embodiment, the temperature of the drying step is 70°C-85°C and the pressure is less than 80 MPa.

[0020] In an optional embodiment, the method further includes monitoring the thinning amount of the silicon material after drying relative to the silicon material before pickling:

[0021] If the thinning amount is less than 5μm and the silicon material surface is white or atomized, add nitric acid to the acid solution;

[0022] If the thinning amount is less than 5μm and the cut surface of the silicon material has non-silicon substances attached, darkening or obvious diamond wire marks, add hydrofluoric acid to the acid solution;

[0023] If the thinning amount is greater than 10μm and there are acid spots on the surface of the silicon material, reduce the concentration of hydrofluoric acid in the acid solution.

[0024] The present invention has the following beneficial effects:

[0025] In the present application, by optimizing the composition of the pickling solution and controlling the pickling temperature, a complex is formed on the surface of the silicon material, and the complex is caused to separate from the silicon material during warm water rinsing, which is beneficial to reducing acid consumption and lowering the cost of the pickling solution per unit volume; after cleaning, the surface of the silicon material is glossy and no acid spots are generated, the yield of the oxide layer is improved after one cleaning, the efficiency of oxide layer removal is improved, and the surface quality of the silicon material is effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 This is a photo of the white surface of the silicon material in Example 1;

[0028] Figure 2 This is a photo of non-silicon substances attached to the cut surface of the silicon material in Example 1 (the surface appears to be similar to oil stains);

[0029] Figure 3 This is a photo of acid spots on the surface of the silicon material in Example 1;

[0030] Figure 4 This is a photo of the silicon material after cleaning in Example 1;

[0031] Figure 5 This is a photo of the silicon material after cleaning in Comparative Example 1;

[0032] Figure 6 The temperature in the pickling tank in the early stage of pickling in Example 1 and Comparative Example 1 varies with the amount of silicon material cleaned. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0034] The embodiment of the present invention provides a cleaning method for reducing acid spots of silicon materials, comprising:

[0035] Pickling: pickling the silicon material, wherein the acid solution used for pickling includes hydrofluoric acid, nitric acid and water in a mass ratio of 1: (18-20): (9-10), the pickling temperature is 20°C-30°C, and the pickling time is 40s-200s;

[0036] Rinse with warm water: use warm water at 25℃-80℃ to rinse the acid-washed silicon material with warm water, and then dry it.

[0037] In the early stage of pickling, a chemical reaction Si+4HNO3+18HF=3H2SiF6+4NO+8H2O will occur. This chemical reaction is relatively violent, and the pickling temperature rises sharply. The high temperature further aggravates the intensity of the reaction, which reduces the controllability of pickling. At the same time, a large amount of nitrogen oxides will be generated, and acid spots will be generated on the surface of the silicon material. In this application, in order to reduce acid spots, the concentration of hydrofluoric acid in the pickling solution is first reduced, and the pickling temperature is controlled to ensure that the pickling temperature is between 20°C and 24°C, so as to reduce the reduction in pickling controllability caused by the temperature rise, and then cause the generation of acid spots.

[0038] Specifically, in the embodiment of the present application, the acid solution used for pickling includes hydrofluoric acid, nitric acid and water in a mass ratio of 1: (16-18): (10-13), wherein the acid solution can be prepared by mixing hydrofluoric acid (electron pole, concentration 49%) and nitric acid (electron pole, concentration 69%) in a mass ratio. After the pickling step, warm water is used to rinse the pickled silicon material. As the rinsing water temperature increases, the residue on the surface of the silicon material can be dissolved and detached faster, which is beneficial to improving the cleaning efficiency, reducing the formation of acid spots, and thus helping to improve the pickling pass rate.

[0039] The water used for warm water rinsing can come from the water generated by subsequent drying, wind shearing, and high-temperature drainage. In some embodiments, the water temperature used for warm water rinsing is about 30°C-50°C, which is more conducive to ensuring the cleaning effect of the silicon material; in some embodiments, the rinsing time can be 630s-1080s.

[0040] In some embodiments, in order to ensure sufficient contact between the solid and the liquid during pickling or rinsing, a bubbling device may be introduced to fully stir the liquid.

[0041] In an optional embodiment, when the mass volume ratio of the silicon material after pickling to the acid solution is 33kg / L-35kg / L, a hydrofluoric acid solution is added to the acid solution, and the mass fraction of hydrofluoric acid in the hydrofluoric acid solution is greater than 45%.

[0042] As the pickling of silicon material proceeds, the hydrofluoric acid in the pickling solution is continuously consumed. To ensure the pickling effect, hydrofluoric acid needs to be added. The added hydrofluoric acid should have a higher concentration. In some embodiments, electronically charged hydrofluoric acid with a concentration of 49% can be added.

[0043] In an optional embodiment, the ratio of the volume of the added hydrofluoric acid solution to the volume of the acid solution is 0.33-0.35.

[0044] If the volume of hydrofluoric acid solution added is too much, the risk of acid spots may still increase. However, if the volume of hydrofluoric acid solution added is too low, the silicon material cannot be cleaned completely. Therefore, the volume of hydrofluoric acid solution added needs to be appropriate.

[0045] In an optional embodiment, when the mass volume ratio of the silicon material after pickling to the acid solution reaches 33kg / L-35kg / L, a mixed acid is added to the acid solution, wherein the mixed acid includes hydrofluoric acid, nitric acid and water in a mass ratio of 1:(5-6):(3-4).

[0046] As the pickling of silicon materials proceeds, the hydrofluoric acid and nitric acid in the pickling solution will be continuously consumed, so it is necessary to add hydrofluoric acid and nitric acid. At this time, since the solution in the pickling tank can dilute the mixed acid, in order to ensure the effect of silicon material pickling, the concentration of hydrofluoric acid in the mixed acid can be slightly increased compared to the initial concentration of the pickling solution.

[0047] In an optional embodiment, 0.9 ml-1.1 ml of mixed acid is added for every 0.3 kg of silicon material washed with acid.

[0048] In an optional embodiment, the silicon material is exposed to the air for less than 1 minute between acid washing and warm water rinsing.

[0049] The longer the silicon material is exposed to the air, the longer the acid spot reaction time will be, thereby reducing the pickling pass rate.

[0050] In an optional embodiment, the pickling is carried out in a pickling tank, which is provided with a circulating liquid inlet and a circulating liquid outlet, a circulating pipe is connected between the circulating liquid inlet and the circulating liquid outlet, and a cooling water machine is provided on the circulating pipe, which cools the liquid passing through it to 14°C-18°C.

[0051] A cooling water machine is used to cool the pickling solution to control the temperature of the pickling solution in the pickling tank to be stable between 20°C and 24°C, which is beneficial to improving the controllability of the pickling step.

[0052] In an optional embodiment, after the warm water rinsing, the silicon material is also sequentially subjected to pure water rinsing, selective treatment and drying, and the selective treatment includes at least one of bubbling rinsing, wind shear drying and high-temperature drainage.

[0053] After warm water rinsing, the silicon material can be transferred to a pure water rinsing tank for pure water rinsing; it can also directly enter the wind shear drying or high temperature drainage step for preliminary drying, and then transferred to the drying step. The wind shear drying can use a blower to increase the air flow speed on the surface of the silicon material to promote the drying rate of the silicon material; in some embodiments, the temperature can also be appropriately increased to further increase the drying rate of the silicon material; in the high temperature drainage step, the temperature can be set at about 85°C.

[0054] It should be noted that, in the method of the present application, except for the water derived from nitric acid or hydrofluoric acid, all other water is pure water with a resistivity greater than 15 megohms.

[0055] In an optional embodiment, the temperature of the drying step is 70° C.-85° C., the pressure is less than 80 MPa, and vacuum drying is beneficial to increase the drying rate.

[0056] In an optional embodiment, the method further includes monitoring the thinning amount of the silicon material after drying relative to the silicon material before pickling:

[0057] If the thinning amount is less than 5μm and the surface of the silicon material is visually white or atomized, add nitric acid to the acid solution;

[0058] If the thinning amount is less than 5μm and the cut surface of the silicon material is dark or the diamond wire marks are obvious, add hydrofluoric acid to the acid solution;

[0059] If the thinning amount is greater than 10μm and there are acid spots on the surface of the silicon material, reduce the concentration of hydrofluoric acid in the acid solution.

[0060] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0061] Example 1

[0062] This embodiment provides a cleaning method for reducing acid spots on silicon materials, comprising:

[0063] Pickling, transfer the monocrystalline silicon recycling material to the pickling tank for pickling, the pickling time is 60s, 41L hydrofluoric acid (electronic pole, mass fraction 49%) and 550L nitric acid (electronic pole, mass fraction 69%) are added to the pickling tank, the initial temperature of the pickling solution is 22°C, the pickling tank is provided with a circulating liquid inlet and a circulating liquid outlet, a circulating pipe is connected between the circulating liquid inlet and the circulating liquid outlet, a cooling water machine is provided on the circulating pipe, and the cooling water machine cools the liquid passing through it to 14°C-18°C.

[0064] Warm water rinsing: After pickling, the silicon material is taken out of the pickling tank and transferred to the warm water rinsing tank. The silicon material is exposed to the air for 30 seconds. The pickled silicon material is rinsed with warm water at 40℃-45℃, rinsed with pure water, drained at high temperature and dried. The temperature of the drying step is 80℃ and the pressure is 80MPa.

[0065] Wherein, silicon material is added into the pickling tank according to about 150 kg per batch. After the pickling of 20 tons of silicon material is completed, 20 L of electron pole and 49% hydrofluoric acid by mass are added into the pickling tank. Meanwhile, 300 mL of hydrofluoric acid (electron pole, 49% by mass) and 1200 mL of nitric acid (electron pole, 69% by mass) are added into the pickling tank for every 3 batches of silicon material pickled.

[0066] It also includes monitoring the thinning amount of the silicon material after drying relative to the silicon material before pickling:

[0067] If the thinning amount is less than 5μm and the silicon material surface is visually white or atomized, Figure 1 As shown, nitric acid is gradually added to the acid solution until the surface of the silicon material turns white or the atomization disappears;

[0068] If the thinning amount is less than 5μm and the cut surface of the silicon material is visually adhered to non-silicon substances, darkened or with obvious diamond wire marks, such as Figure 2 As shown, gradually add hydrofluoric acid to the acid solution until the cut surface of the silicon material is no longer dark or the diamond line marks are not obvious;

[0069] If the thinning amount is greater than 10μm and there are acid spots on the surface of the silicon material, such as Figure 3 As shown, the concentration of hydrofluoric acid in the acid solution is reduced until the acid spots on the surface of the silicon material disappear.

[0070] The pickling temperature can be kept stable until 170t of silicon material is cleaned. Figure 4 As shown, no acid spots are visible to the naked eye, the cleaning effect is good, and the silicon material thinning amount is 5-10μm. Under this value, the cleaning effect is guaranteed while the raw material loss is low.

[0071] Comparative Example 1

[0072] This comparative example provides a method for pickling a silicon material, comprising:

[0073] Pickling: transfer the single crystal silicon recycled material to the pickling tank for pickling according to each batch of about 150 kg. The pickling time is 50 seconds. Add 60L hydrofluoric acid (electronic pole, mass fraction 49%) and 530L nitric acid (electronic pole, mass fraction 69%) into the pickling tank.

[0074] After warm water rinsing and pickling, the silicon material is taken out of the pickling tank and transferred to the rinsing tank. During this period, the silicon material is exposed to the air for 30 seconds. The pickled silicon material is rinsed with 22°C water, rinsed with pure water, drained at high temperature and dried. The temperature of the drying step is 80°C and the pressure is 80MPa.

[0075] The silicon material is pickled by this comparative method. The temperature rises in the early stage of pickling. The unqualified rate of the first 5T single crystal silicon recycling material is 65%, the unqualified rate of the 5-15T single crystal silicon recycling material is 80%, and the unqualified rate of the 15-20T single crystal silicon recycling material is 70%. Figure 5 As shown, the arrow indicates the acid spot.

[0076] The temperature of the pickling solution in the pickling tank in the pickling method of the silicon material in Example 1 and Comparative Example 1 was monitored, and the results were as follows: Figure 6 As shown. Figure 6 In the early stage of pickling, the temperature of the pickling solution in the pickling tank will not rise significantly, and the temperature of the pickling solution is relatively stable.

[0077] Comparative Example 2

[0078] This comparative example provides a cleaning method for reducing acid spots on silicon materials. The only difference from Example 1 is that the cooling water machine is turned off and the initial acid washing liquid temperature is 25°C.

[0079] After warm water rinsing and pickling, the silicon material is taken out of the pickling tank and transferred to the rinsing tank. The silicon material is exposed to the air for 30 seconds. The pickled silicon material is rinsed with 22°C water, rinsed with pure water, drained at high temperature and dried. The temperature of the drying step is 80°C and the pressure is 80MPa.

[0080] After the cooling water machine is turned off, the temperature of the acid solution rises sharply during the reaction. The temperature increase accelerates the reaction speed, increases the amount of acid volatilization, and reacts with a large amount of NO. The unqualified rate of the first 20T single crystal silicon circulating material reaches 90%. The volatilization of the acid solution increases, and the hydrofluoric acid and nitric acid in the tank are diluted. The dilution has a reverse effect on the subsequent acid replenishment and concentration adjustment.

[0081] Comparative Example 3

[0082] This comparative example provides a cleaning method for reducing acid spots on silicon materials, which is different from Example 1 only in that 30L of hydrofluoric acid (electron pole, mass fraction 49%) and 550L of nitric acid (electron pole, mass fraction 69%) are added to the pickling tank.

[0083] Comparative Example 4

[0084] This comparative example provides a cleaning method for reducing acid spots on silicon materials, which is different from Example 1 only in that 50L of hydrofluoric acid (electron pole, mass fraction 49%) and 550L of nitric acid (electron pole, mass fraction 69%) are added to the pickling tank.

[0085] Comparative Example 5

[0086] This comparative example provides a cleaning method for reducing acid spots on silicon materials. The only difference from Example 1 is that after the pickling of 20t of silicon materials is completed, only 20L of electron pole and 49% hydrofluoric acid by mass are added to the pickling tank, and 300mL of hydrofluoric acid (electron pole, 49% by mass) and 1200mL of nitric acid (electron pole, 69% by mass) are not added to the pickling tank for every 3 batches of silicon materials pickled.

[0087] Comparative Example 6

[0088] This comparative example provides a cleaning method for reducing acid spots on silicon materials. The only difference from Example 1 is that after the pickling of 20t of silicon materials is completed, only 300mL of hydrofluoric acid (electronic pole, mass fraction 49%) and 1200mL of nitric acid (electronic pole, mass fraction 69%) are added to the pickling tank for every 3 batches of silicon materials pickled, and 20L of electronic pole and 49% mass fraction of hydrofluoric acid are not added to the pickling tank.

[0089] The average thinning amount of the silicon material obtained by the pickling method in the above-mentioned embodiments and comparative examples and the unqualified rate caused by acid spots were statistically analyzed, and the results are shown in the following table.

[0090]

[0091]

[0092] Remark:

[0093] The eligibility criteria are:

[0094] ①. There is no non-silicon material attached to the surface of the monocrystalline silicon recycling material and no acid spots; the whitening and atomization area of ​​a single piece does not exceed 5CM 2 1. In a single silicon material, the total whitening area and the total atomization area are both less than 5% of the area of ​​a single silicon material;

[0095] ②, Thinning amount 5-10um (thinning amount test and calculation method: from a single piece of silicon material, take 4 samples with an area of ​​30-50mm and a thickness of 3mm for cleaning, calculate the weight difference before and after cleaning, and calculate the specific value of thinning amount through the mass, volume, and surface area formula conversion);

[0096] ③. Diamond wire marks are not obvious: The specific standards are: crush the cleaned silicon material, take a sample with a side length of 3-8mm, and the total content of metal elements is ≤20ppbw; or take a sample with a side length of 8-50mm, and the total content of metal elements is ≤10ppbw; the detected elements include Fe, Cr, Ni, Cu, Zn, Na, Ca, Mg, K and Al.

[0097] In the embodiments of the present application, by optimizing the composition of the pickling solution, a complex is formed on the surface of the silicon material, and the complex is caused to separate from the silicon material during warm water rinsing, which is beneficial to reducing acid consumption and reducing the cost of the pickling solution per unit volume; after cleaning, the surface of the silicon material is glossy and no acid spots are generated, and the yield of the oxide layer is increased to 100% after one cleaning, thereby improving the efficiency of oxide layer removal, and the surface quality of the silicon material is improved. The quality, crystallization rate, and yield rate of the crystal rod prepared therefrom are also improved, thereby reducing the rework cost, and the silicon loss can be reduced by 0.02%; the requirements for quality inspectors are reduced, and the operation is convenient. At the same time, the amount of acid mist generated in the initial stage of pickling is small, which is beneficial to the improvement of the working environment.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A cleaning method for reducing acid spots on silicon materials, characterized in that: include: Pickling: pickling the silicon material, wherein the acid solution used for pickling includes hydrofluoric acid, nitric acid and water in a mass ratio of 1: (18-20): (9-10), the pickling temperature is 20°C-30°C, and the pickling time is 40s-200s; Rinse with warm water: use warm water at 25℃-80℃ to rinse the acid-washed silicon material with warm water, and then dry it.

2. The cleaning method for reducing silicon acid spots according to claim 1, characterized in that: When the mass volume ratio of the pickled silicon material to the acid solution is 33kg / L-35kg / L, a hydrofluoric acid solution is added to the acid solution, and the mass fraction of the hydrofluoric acid in the hydrofluoric acid solution is 45%-50%.

3. The cleaning method for reducing silicon acid spots according to claim 2, characterized in that: The ratio of the volume of the added hydrofluoric acid solution to the volume of the acid solution is 0.33-0.

35.

4. The cleaning method for reducing silicon acid spots according to claim 1, characterized in that: When the mass volume ratio of the pickled silicon material to the acid solution reaches 33kg / L-35kg / L, a mixed acid is added to the acid solution, wherein the mixed acid includes hydrofluoric acid, nitric acid and water in a mass ratio of 1:(5-6):(3-4).

5. The cleaning method for reducing silicon acid spots according to claim 4, characterized in that: For every 0.3kg of silicon material to be acid washed, add 0.9ml-1.1ml of mixed acid.

6. The cleaning method for reducing silicon acid spots according to claim 1, characterized in that: After pickling and before rinsing with warm water, the silicon material is exposed to the air for less than 1 minute.

7. The cleaning method for reducing silicon acid spots according to claim 1, characterized in that: The pickling is carried out in a pickling tank, which is provided with a circulating liquid inlet and a circulating liquid outlet, a circulating pipe is connected between the circulating liquid inlet and the circulating liquid outlet, and a cooling water machine is provided on the circulating pipe, which cools the liquid passing through it to 14°C-18°C.

8. The cleaning method for reducing silicon acid spots according to claim 1, characterized in that: After the warm water rinsing, the silicon material is also subjected to pure water rinsing, selective treatment and drying in sequence, wherein the selective treatment includes at least one of bubbling rinsing, wind shear drying and high-temperature drainage.

9. The cleaning method for reducing silicon acid spots according to claim 1, characterized in that: The temperature of the drying step is 70°C-85°C and the pressure is less than 80 MPa.

10. The cleaning method for reducing silicon acid spots according to claim 1, characterized in that: It also includes monitoring the thinning amount of the silicon material after drying relative to the silicon material before pickling: If the thinning amount is less than 5μm and the silicon material surface is white or atomized, add nitric acid to the acid solution; If the thinning amount is less than 5μm and the cut surface of the silicon material has non-silicon substances attached, darkening or obvious diamond wire marks, add hydrofluoric acid to the acid solution; If the thinning amount is greater than 10μm and there are acid spots on the surface of the silicon material, reduce the concentration of hydrofluoric acid in the acid solution.

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