CN115116842B - Application of perfluorinated substituent-containing polyvinylamine copolymer in monocrystalline silicon piece alkali polishing - Google Patents

Abstract

The invention discloses an application of a perfluorinated-substituent-containing polyvinylamine copolymer in alkali polishing of monocrystalline silicon wafers, wherein the perfluorinated-substituent-containing polyvinylamine copolymer is prepared into an alkali polishing solution for polishing monocrystalline silicon wafers. According to the method for copolymerizing the acid-alkali-resistant perfluoroalkyl chain into the main chain of the water-soluble polyvinylamine cationic polymer, the perfluoroalkyl group-containing polyvinylamine copolymer contains the hydrophilic-NH ³⁺ functional group and the hydrophobic acid-alkali-resistant perfluoroalkyl chain, when monocrystalline silicon is subjected to alkali polishing, ammonia ions interact with silicon oxide, and the perfluoroalkyl chain-containing polyethyleneimine copolymer is used as an additive for the alkali polishing of the monocrystalline silicon to be used as a protective agent for a front silicon oxide layer, when the monocrystalline silicon is subjected to back polishing, the copolymer is effectively assembled on the front silicon oxide surface, the acid-alkali-resistant functional groups are uniformly distributed in the copolymer self-assembled film, the front PN junction of the monocrystalline silicon is protected from being damaged, and the polishing effect of the back surface of the monocrystalline silicon is improved.

Description

Application of polyvinylamine copolymers containing perfluorinated groups in alkaline polishing of single crystal silicon wafers

Technical Field

The invention belongs to the technical field of polymer materials and solar cells, and particularly relates to application of a polyvinylamine copolymer containing a perfluorinated substituent in alkali polishing of a single crystal silicon wafer.

Background Art

Solar photovoltaic power generation has a good application prospect. The current development trend of the photovoltaic industry is to improve efficiency and reduce costs. However, the efficiency of conventional structure batteries has no room for improvement. The research and development hotspot is high-efficiency monocrystalline silicon solar cells. Among the various P-type high-efficiency batteries currently on the market, only the rear passivation technology (PERC) can maximize the performance of the battery on the basis of cost parity. The products involved in this technology have high efficiency, high opening voltage, low packaging loss, and better weak light response. It is a strategic product to seize the mainstream market.

At present, the production process of PERC cells is as follows: wet alkaline texturing, low-pressure diffusion junction, etching and back polishing, ALD aluminum oxide coating, PECVD positive/reverse silicon nitride coating, printing and sintering, and testing and sorting. The PERC cell back passivation technology is to deposit a layer of Al ₂ O _{3 film on the back surface of the cell. The Al 2 O 3 film mainly} uses the negative charge characteristic to achieve a good passivation effect on the back surface of the cell. By printing electrodes on the passivation film, the metal electrode and silicon can form an ohmic contact, so that the photogenerated carriers can be effectively collected. In the preparation process of PERC solar cells, polishing the back of the silicon wafer can more effectively improve the performance of solar cells.

The back-side polishing process of silicon wafers is to polish the back side of the silicon wafer before coating. After polishing, the back surface is flat, which increases the reflection of long-wave light in the solar spectrum on the back surface of the silicon wafer, increases the secondary absorption of transmitted light returning to the silicon wafer, improves IQE, and increases output current; at the same time, the specific surface area of the back surface of the silicon wafer is reduced after polishing, thereby reducing the recombination of photogenerated carriers on the back side, increasing the life of the silicon wafer, and improving the passivation effect; after polishing, the aluminum agglomerates produced after the back field printing and sintering of the silicon wafer are more likely to contact with silicon, increasing the effective area of the back field alloy layer.

At present, three types of polishing agents are mainly used in the polishing steps of industrialized monocrystalline silicon cell production: 1. Etching liquid composed of nitric acid and hydrofluoric acid. The disadvantage is that the reflectivity of the silicon wafer after polishing is low, the production cost is high, and the environmental pollution is serious; 2. Tetramethylammonium hydroxide. The reflectivity of the silicon wafer treated with this type of polishing agent is high, but the disadvantage is that the cost of the polishing liquid is high, the environmental pollution is serious, and the polishing cost is high; 3. Concentrated alkali, using high-concentration potassium hydroxide and sodium hydroxide inorganic alkali for polishing, the disadvantage is that the process is unstable and the reaction process is difficult to control. At the same time, the alkali will corrode the silicon oxide on the front of the silicon wafer, thereby destroying the front PN junction and causing the battery to fail. In this case, using alkali polishing additives to protect the front silicon oxide layer can play a role in leveraging strengths and avoiding weaknesses. Based on this, the protective effect of monocrystalline silicon alkali polishing additives has become the key to improving the performance of monocrystalline silicon solar cells.

Summary of the invention

The object of the present invention is to provide a method for synthesizing a polyvinylamine copolymer having a perfluorinated substituent. Another object of the present invention is to provide an application of the polyvinylamine copolymer having a perfluorinated substituent in a perovskite resistive random access memory.

Based on the above purpose, the present invention adopts the following technical solutions:

Application of polyvinylamine copolymers containing perfluorinated substituents in alkaline polishing of single crystal silicon wafers.

The polyvinylamine copolymer with a perfluorinated substituent is configured into an alkaline polishing liquid to polish a single crystal silicon wafer.

The polishing process of single crystal silicon wafers includes the following steps:

1) Cleaning and pre-treating the single crystal silicon wafer;

2) placing the single crystal silicon wafer pretreated in step 1) in an alkaline polishing solution to polish the back of the single crystal silicon wafer; the alkaline polishing solution comprises by weight: 0.5-3.5% additive, 1-3% alkaline agent, and the balance water, wherein the additive is a polyvinylamine copolymer with a perfluorinated substituent;

3) Purify the single crystal silicon wafer after polishing in step 2).

The preparation method of the alkaline polishing liquid is as follows: firstly, the additive is dissolved in a part of water to obtain a perfluoro-substituted polyvinylamine copolymer solution; then, the alkaline agent is dissolved in another part of water to obtain a dilute alkaline solution; and the perfluoro-substituted polyvinylamine copolymer solution and the dilute alkaline solution are mixed to obtain the polishing liquid.

In step 1), the cleaning pretreatment method of the single crystal silicon wafer is: the single crystal silicon wafer is cleaned with ethanol solution and water in sequence, and then dried; in step 2), the polishing temperature is 40-80°C, and the polishing time is 2-16min; the alkaline agent is sodium hydroxide or potassium hydroxide, and the water is deionized water.

The method for synthesizing a polyvinylamine copolymer having a perfluorinated substituent comprises the following steps:

1) under nitrogen protection, adding N-vinylformamide, perfluorosubstituted α-olefin and initiator into a reaction vessel containing an organic solvent to carry out free radical copolymerization reaction, and after the reaction is completed, separating and purifying to obtain a preliminary product; the molar ratio of N-vinylformamide to perfluorosubstituted α-olefin is (4-99):1;

2) subjecting the preliminary product of step 1) to a hydrolysis reaction under the action of alkalinity, and separating and purifying the hydrolyzate;

3) subjecting the hydrolysis product of step 2) to protonation reaction, and separating and purifying again to obtain the target product.

In step 1), the perfluoro-substituted α-olefin is 1H, 1H, 2H-perfluoro-1-hexene, heptene, octene, nonene, decene, undecene or dodecene; the initiator is azobisisobutyronitrile, and the ratio of the mass of azobisisobutyronitrile to the mass of N-vinylformamide and the perfluoro-substituted α-olefin is 0.1%-5%; in steps 1) and 2), the organic solvent is tetrahydrofuran.

In step 2), the hydrolysis reaction process is as follows: the preliminary product of step 1) and sodium hydroxide are added to a reaction vessel containing anhydrous ethanol, and the hydrolysis reaction is carried out at 60-80° C. for 24-48 hours under nitrogen protection; the separation and purification step is as follows: the solution after the reaction is evaporated to remove the anhydrous ethanol, and the solution is added to tetrahydrofuran to generate a black precipitate, which is filtered, and the black precipitate is washed with tetrahydrofuran and dried to obtain a hydrolysis product.

In step 2), the molar ratio of N-vinylformamide to sodium hydroxide is (0.25-1):1, and the mass concentration of the preliminary product in the solution of the preliminary product, sodium hydroxide and anhydrous ethanol is 5-20%.

In step 3), the protonation reaction process is as follows: under nitrogen protection, the hydrolysis product of step 2) is dissolved in anhydrous ethanol, and then hydroiodic acid is added to carry out a protonation reaction; the second separation and purification step is as follows: the solution after the reaction is added to dichloromethane to produce a brown precipitate, which is filtered, and the brown precipitate is washed with dichloromethane and dried to obtain the target product.

In step 3), the mass concentration of the hydrolyzate in the solution of the hydrolyzate, hydroiodic acid and anhydrous ethanol is 5-20%, the mass concentration of the hydroiodic acid is 57%, and n(hydrolyzate)/n(HI)=0.25-1.

Compared with the prior art, the present invention has the following beneficial effects:

1) The present invention provides a method for copolymerizing an acid- and alkali-resistant perfluoroalkyl chain into a main chain of a water-soluble polyvinylamine cationic polymer, so that the polyvinylamine copolymer with a perfluoro-substituted group contains a hydrophilic -NH ³⁺ functional group and a hydrophobic acid- and alkali-resistant perfluoroalkyl chain. During the alkali polishing of single-crystalline silicon, there is an interaction between the ammonia ion and the silicon oxide. The copolymer is used as an additive for the alkali polishing of the single-crystalline silicon wafer as a protective agent for the front silicon oxide layer. When the single-crystalline silicon wafer is back-polished, the copolymer is effectively assembled on the front silicon oxide surface and the acid- and alkali-resistant functional groups are uniformly distributed in the copolymer self-assembled film, thereby protecting the front PN junction of the single-crystalline silicon wafer from being destroyed and improving the polishing effect of the back of the single-crystalline silicon wafer.

2) When the polyvinylamine copolymer with perfluorinated substituents is applied to the polishing of single crystal silicon wafers, excellent polishing effect can be obtained without using nitric acid, hydrofluoric acid or tetramethylammonium hydroxide in the traditional process. At the same time, the concentration of alkali and copolymer is much lower than that of the conventional polishing process. There is no volatilization in the production process, and the subsequent addition amount is small, which saves processing costs and does not pollute the environment.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

Figure 1 is the FTIR spectra of PNVF, P(NVF-co-HDFD) and P(VAm-co-HDFD);

FIG2 is the ¹ H-NMR spectrum of P(VAm·HI-co-HDFD);

FIG3 is a SEM image of the front side (a) and back side (b) of an unpolished single crystal silicon wafer;

FIG4 is a SEM image of the front side (c) and back side (d) of a single crystal silicon wafer obtained by soda ash polishing;

FIG5 is a SEM image of the front side (e) and back side (f) of the single crystal silicon wafer obtained after using the additive.

DETAILED DESCRIPTION

In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention is described in detail below, but the following embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

Example 1

A method for synthesizing a polyvinylamine copolymer having a perfluorinated substituent comprises the following steps:

1) Under nitrogen protection, N-vinylformamide (NVF), 1H,1H,2H-perfluoro-1-decene (HDFD) and azobisisobutyronitrile (AIBN) were added to a Shrek bottle containing tetrahydrofuran (w(NVF+HDFD)/w(solute)=10%), and condensed and refluxed at 65°C with stirring for 9h (as the reaction proceeded, the solution gradually changed from colorless and transparent to white, and the white color deepened with time, and finally there was no obvious color change). The reaction results were as follows: After the reaction, the solution was allowed to stand to generate a large amount of white precipitate, which was filtered to obtain a precipitate product. The precipitate product was washed three times with tetrahydrofuran (to remove the residual unreacted monomers), and dried in a vacuum drying oven at 40°C for 24 hours (to remove tetrahydrofuran) to obtain a preliminary product (P(NVF-co-HDFD)); the molar ratio of N-vinylformamide to HDFD was 10:1; the mass ratio of azobisisobutyronitrile to the mass sum of N-vinylformamide and HDFD was 3%;

2) The preliminary product of step 1) and sodium hydroxide are added to a Shrek bottle containing anhydrous ethanol, and under nitrogen protection, condensed and refluxed at 70° C. with stirring for 24 hours (as the reaction proceeds, the solution gradually changes from turbid white to brown, and becomes black as time goes by, and finally there is no obvious color change). After the reaction is completed, the solution after the reaction is rotary evaporated to remove the anhydrous ethanol, and then dissolved in a small amount of anhydrous ethanol, and added dropwise to four times the volume of tetrahydrofuran to produce a black precipitate, which is filtered, and the black precipitate is washed three times with tetrahydrofuran (to remove unreacted NaOH and by-product sodium formate), and placed in a vacuum oven at 40° C. to dry for 24 hours to obtain a hydrolysis product (P(VAm-co-HDFD)); the molar ratio of N-vinylformamide to sodium hydroxide is 1:4, and the mass concentration of the preliminary product in the solution of the preliminary product, sodium hydroxide and anhydrous ethanol is 10%;

3) under nitrogen protection, the hydrolysis product of step 2) is added to a Shrek bottle containing anhydrous ethanol, stirred for 24 hours to fully dissolve the hydrolysis product, and then hydroiodic acid is added. Under the condition of light-proof nitrogen protection, the reaction is carried out at 0° C. for 24 hours. The solution after the reaction is added dropwise into dichloromethane to produce a brown precipitate, which is filtered. The brown precipitate is ultrasonically washed three times with dichloromethane, placed in a vacuum oven at 40° C., and dried for 24 hours to obtain the target product, a perfluorosubstituted polyethyleneamine copolymer (P(VAm·HI-co-HDFD)); the mass concentration of the hydrolysis product in the solution of the hydrolysis product, hydroiodic acid, and anhydrous ethanol is 10%, the mass concentration of the hydroiodic acid is 57%, and n(hydrolysis product)/n(HI)=0.5.

Wherein: w(NVF+HDFD) is the sum of the masses of NVF and HDFD, and w(solution) is the sum of the solution masses of NVF, HDFD, AIBN and tetrahydrofuran.

Synthesis route of P(VAm·HI-co-HDFD) copolymer

The copolymer product of Example 1 was analyzed and tested.

(1) Nuclear Magnetic Resonance (NMR)

In this study, a Bruker DPX-400 nuclear magnetic resonance spectrometer was used to analyze the polymers by 1H-NMR using DMSO-d6 as solvent.

(2) Infrared spectrometer (FTIR)

In this study, TENSOR-27 infrared spectrometer from Bruker was used to analyze the polymer using infrared spectra in total reflection mode with a test range of 400 cm ^-1 to 4000 cm ^-1 .

(3) X-ray diffractometer (XRD)

The X-ray diffractometer model used in this experiment is RINT-2500, which is used to analyze the phase of the perovskite film. Cu Kα is used as the radiation source in the experiment. The scanning speed was 10°/min.

(4) Field emission scanning electron microscopy (FESEM)

In this experiment, a field emission scanning electron microscope (FESEM) model JSM-7001F produced in Japan was used to observe the surface morphology of the perovskite material.

(5) Contact angle tester

In this study, the contact angle of distilled water on the film surface was measured using the JC2000C1 contact angle meter produced by Shanghai Zhongchen Technology Equipment Co., Ltd.

Figure 1 is the FTIR spectrum of P(NVF-co-HDFD), and the FTIR spectrum of PNVF is attached for comparison. According to the infrared spectra of P(NVF-co-HDFD) and PNVF, 3500-3100 cm ^-1 is the stretching vibration peak of amine and amide NH, 1652 cm ^-1 is the stretching vibration absorption peak of C=O in the amide group, 1537 cm ^-1 is the in-plane bending vibration absorption peak of amide group NH, 1386 cm ^-1 is the intra-bond bending vibration peak of methine CH, and 1250 cm ^-1 is the stretching vibration peak of amide group CN bond, which are the common structural features of the two polymers. However, the characteristic absorption peak of CF bond appears in the spectrum of P(NVF-co-HDFD), among which the absorption peak at 1204 cm ^-1 belongs to the asymmetric stretching vibration of CF ₂ , and the absorption peak at 1146 cm ^-1 belongs to the symmetric stretching vibration mode of CF _3. These data fully prove the successful synthesis of P(NVF-co-HDFD).

Figure 1 is the FTIR spectrum of P(VAm-co-HDFD). The stretching vibration absorption peak of C=O in the amide group at 1652 cm ^-1 disappears, and the stretching vibration absorption peak of _-NH3 ⁺ appears at 1588 cm ^-1 , which fully proves that P(NVF-co-HDFD) is completely hydrolyzed under alkaline conditions to obtain P(VAm-co-HDFD).

Figure 2 is the ¹ H-NMR spectrum of P(VAm·HI-co-HDFD). The chemical shift at 1.99 ppm is the proton peak of the methylene -CH ₂ - on the main chain, the signal peak at 3.85 ppm is the proton peak of the methine -CH- on the main chain, the signal peak at 2.51 ppm is attributed to the proton peak of the deuterated reagent DMSO, and the signal peak at 8.07 ppm is the proton peak of -NH ₃ ⁺ . The above results prove the successful synthesis of the final product P(VAm·HI-co-HDFD).

Example 2

The invention discloses an application of a polyvinylamine copolymer containing a perfluorinated substituent in alkali polishing of a single crystal silicon wafer. The polyvinylamine copolymer containing a perfluorinated substituent is configured into an alkali polishing liquid to polish the single crystal silicon wafer.

The polishing process of single crystal silicon wafers includes the following steps:

1) Cleaning pretreatment: First, use 95% ethanol solution to ultrasonically clean the single crystal silicon wafer for 1 hour, then rinse it with deionized water, and dry it for later use;

2) immersing the single crystal silicon wafer after the cleaning and pretreatment in step 1) in an alkaline polishing liquid in an alkaline polishing tank, and polishing the back side of the single crystal silicon wafer; the polishing temperature is 80° C., and the polishing time is 5 min; the alkaline polishing liquid is made of the following components in weight percentage: 2% additive, 3% sodium hydroxide mass fraction, and the balance is deionized water;

3) Purification treatment: The single crystal silicon wafer polished in step 2) is cleaned with deionized water and dried.

Step 2) A method for preparing an alkaline polishing liquid, such as 1000 g of the alkaline polishing liquid, comprising the following steps: 1) Preparation of a perfluoro-substituted polyvinylamine copolymer solution: dissolving a corresponding mass of the perfluoro-substituted polyvinylamine copolymer prepared in Example 1 in 450 g of deionized water to obtain a perfluoro-substituted polyvinylamine copolymer solution;

2) dissolving a corresponding amount of sodium hydroxide in 500 g of deionized water to obtain a dilute alkali solution;

3) Mix the polyvinylamine copolymer solution with perfluorinated substituents in step 1) and the diluted alkali solution in an alkali polishing tank, and add deionized water to 1000 g to obtain the alkali polishing solution. Heat the alkali polishing solution to a polishing temperature of 80 degrees Celsius using the heating mechanism of the alkali polishing tank for standby use.

Step 1) Pre-cleaning treatment can remove oil and other impurities on the surface of the single crystal silicon wafer and eliminate interfering factors.

Step 3) purifying impurities remaining in the single crystal silicon wafer after cleaning and polishing.

Example 3

The invention discloses an application of a polyvinylamine copolymer containing a perfluorinated substituent in alkali polishing of a single crystal silicon wafer. The polyvinylamine copolymer containing a perfluorinated substituent is configured into an alkali polishing liquid to polish the single crystal silicon wafer.

The polishing process of single crystal silicon wafers includes the following steps:

1) Cleaning pretreatment: First, use 95% ethanol solution to ultrasonically clean the single crystal silicon wafer for 1 hour, then rinse it with deionized water, and dry it for later use;

2) immersing the single crystal silicon wafer after the cleaning and pretreatment in step 1) in an alkaline polishing liquid in an alkaline polishing tank, and polishing the back side of the single crystal silicon wafer; the polishing temperature is 50° C., and the polishing time is 16 min; the alkaline polishing liquid is made of the following components in weight percentage: 6% additive, 1% sodium hydroxide mass fraction, and the balance is deionized water;

3) Purification treatment: The single crystal silicon wafer polished in step 2) is cleaned with deionized water and dried.

The preparation method of the alkaline polishing liquid is as shown in Example 2.

Embodiment 4 effect test

Based on the need to verify the alkali polishing effect of single crystal silicon wafers, a Phenom desktop scanning electron microscope was used to observe the surface polishing effects of unpolished single crystal silicon wafers, single crystal silicon wafers obtained by alkali polishing, and single crystal silicon wafers after using additives in Example 2, and EDS was used to observe the polished front and back sides of the single crystal silicon wafers, and the SEM images are shown in Figures 3, 4, and 5, respectively.

The difference between the alkaline polishing method and the step of Example 2 is that no additive is added to the alkaline polishing liquid.

In Figure 3, the front side (a) and back side (b) of an unpolished single crystal silicon wafer; in Figure 4, the front side (c) and back side (d) of a single crystal silicon wafer polished with an alkali agent; in Figure 5, the front side (e) and back side (f) of a single crystal silicon wafer after using the additive in Example 2.

As shown in FIG3 , both the front and back sides of the unpolished single crystal silicon wafer are pyramids with uniform shapes.

As shown in FIG4 , when the single crystal silicon wafer is polished with a dilute alkali solution, it is found that the polishing effect of the back side of the single crystal silicon wafer is not very good, and while the back side is polished, the front side is also damaged.

As shown in FIG5 , the single crystal silicon wafer is polished using the alkaline polishing solution prepared in Example 2. It can be seen that the polishing effect on the back side of the single crystal silicon wafer is significant, and the flatness of the back side is improved. At the same time, the corrosion inhibition effect on the front side of the single crystal silicon wafer is significant.

Claims (8)

1. The application of the perfluorinated-substituent-containing polyvinylamine copolymer in the alkali polishing of monocrystalline silicon wafers is characterized in that the synthesis method of the perfluorinated-substituent-containing polyvinylamine copolymer comprises the following steps:

1) Under the protection of nitrogen, adding N-vinylformamide, perfluoro substituted alpha-olefin and an initiator into a reaction vessel containing an organic solvent for free radical copolymerization reaction, and separating and purifying after the reaction is finished to obtain a primary product; the ratio of the amounts of the N-vinylformamide and the perfluoro-substituted alpha-olefin is (4-99) to 1;

2) Carrying out hydrolysis reaction on the primary product in the step 1) under the alkaline action, and separating and purifying to obtain a hydrolysis product;

3) Carrying out protonation reaction on the hydrolysate in the step 2), and separating and purifying again to obtain a target product;

preparing a perfluorinated substituent-containing polyvinylamine copolymer into an alkali polishing solution to polish the monocrystalline silicon piece;

The alkali polishing solution comprises the following components in percentage by weight: 0.5-3.5% of additive, 1-3% of alkaline agent and the balance of water, wherein the additive is a polyethyleneamine copolymer containing perfluorinated substituents;

in step 1), the perfluoro-substituted α -olefin is 1H, 2H-perfluoro-1-hexa, hepta, octa, nonane, deca, undec or dodecene.

2. Use of a perfluoro substituent-containing polyvinylamine copolymer in single crystal silicon wafer alkaline polishing as claimed in claim 1, wherein the single crystal silicon wafer polishing process comprises the steps of:

1) Cleaning and preprocessing monocrystalline silicon wafers;

2) Placing the monocrystalline silicon piece pretreated in the step 1) into an alkali polishing solution for polishing;

3) And 3) purifying the monocrystalline silicon wafer polished in the step 2).

3. The use of the perfluorinated substituted group-containing polyvinylamine copolymer according to claim 2 in the alkaline polishing of monocrystalline silicon wafers, wherein the alkaline polishing solution is prepared by the following steps: firstly, adding a part of water into the additive to dissolve the additive, so as to obtain a polyethyleneamine copolymer solution containing perfluorinated substituents; and dissolving an alkaline agent in the other part of water to obtain a dilute alkali solution, and mixing the perfluorinated substituent-containing polyvinyl amine copolymer solution with the dilute alkali solution.

4. Use of a perfluoro substituent-containing polyvinylamine copolymer in single crystal silicon wafer alkaline polishing as claimed in claim 3, wherein in step 1) of single crystal silicon wafer polishing treatment, the pretreatment method of single crystal silicon wafer comprises: sequentially adopting ethanol solution and water to clean and dry the monocrystalline silicon piece; in the step 2) of the monocrystalline silicon piece polishing treatment, the polishing temperature is 40-80 ℃ and the polishing time is 2-16min; the alkaline agent is sodium hydroxide or potassium hydroxide, and the water is deionized water.

5. Use of a perfluoro substituted polyvinylamine copolymer according to claim 1 in monocrystalline silicon wafer alkaline polishing, wherein in step 1) the initiator is azobisisobutyronitrile, the ratio of the mass of azobisisobutyronitrile to the sum of the mass of N-vinylformamide and perfluoro substituted α -olefin being 0.1-5%, and the organic solvent is tetrahydrofuran.

6. Use of a perfluoro substituent-containing polyvinylamine copolymer in single crystal silicon wafer alkaline polishing as claimed in claim 5, wherein in step 2), the hydrolysis reaction process: adding the preliminary product obtained in the step 1) and sodium hydroxide into a reaction container containing absolute ethyl alcohol, and carrying out hydrolysis reaction for 24-48h at 60-80 ℃ under the protection of nitrogen; the separation and purification steps are as follows: and evaporating the reacted solution to remove absolute ethyl alcohol, adding the absolute ethyl alcohol into tetrahydrofuran to generate black precipitate, carrying out suction filtration, washing the black precipitate with tetrahydrofuran, and drying to obtain a hydrolysate.

7. The use of a perfluoro substituted polyvinylamine copolymer according to claim 6 for alkali polishing of monocrystalline silicon wafers, wherein the mass ratio of N-vinylformamide to sodium hydroxide in step 2) is (0.25-1) to 1, and the mass concentration of the preliminary product in the solution of preliminary product, sodium hydroxide, absolute ethanol is 5-20%.

8. Use of a perfluorinated-substituent-containing polyvinylamine copolymer according to claim 7 in monocrystalline silicon wafer alkaline polishing, characterized in that in step 3) the protonation reaction process: under the protection of nitrogen, dissolving the hydrolysate in the step 2) in absolute ethyl alcohol, and then adding hydroiodic acid to carry out protonation reaction; the separation and purification steps are as follows: adding the reacted solution into dichloromethane to generate brown precipitate, filtering, washing the brown precipitate with dichloromethane, and drying to obtain a target product; the mass concentration of the hydrolysate in the solution of the hydrolysate, the hydroiodic acid and the absolute ethanol is 5-20%, the mass concentration of the hydroiodic acid is 57%, and n (hydrolysate)/n (HI) =0.25-1.