A chemical cleaning process for electronic grade polysilicon

Abstract

The present invention is a chemical cleaning process for electronic-grade polysilicon. A chemical cleaning process for electronic-grade polysilicon is: silicon material is sequentially cleaned through No. 1-7 slots; wherein, No. 1-3 slots contain hydrofluoric acid and concentrated nitric acid, and the volume percentage of hydrofluoric acid in the slots decreases step by step; No. 4 slot contains hydrofluoric acid and hydrogen peroxide; No. 5 slot contains hydrofluoric acid and hydrochloric acid; No. 6-7 slots contain high-purity water; the concentration of hydrofluoric acid is 49wt%; the concentration of concentrated nitric acid is 69wt%; the concentration of hydrochloric acid is 10-15wt%. The chemical cleaning process for electronic-grade polysilicon described in the present invention can stably control the metal impurity index on the surface of electronic-grade polysilicon at the level of national standards, while extending the service life of chemical agents.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic-grade polysilicon, and in particular relates to a chemical cleaning process for electronic-grade polysilicon. Background Art

[0002] The control indicators for surface metal impurities in electronic-grade polysilicon are very stringent. According to the latest national electronic-grade polysilicon standard GB / T-12963-2022, the minimum standard for entering the electronic-grade polysilicon grade is that the surface metal impurity content is ≤5ppbw, while the national standard first-grade and special-grade products have lower requirements for surface metal impurities, which poses a great challenge to the chemical cleaning process of electronic-grade polysilicon manufacturers.

[0003] At present, my country's electronic-grade polysilicon cleaning technology is weak, the industry has deep technical barriers, and the core cleaning technology of electronic-grade polysilicon materials is mainly in the hands of world-class companies. Among the mainstream polysilicon block cleaning technologies, wet cleaning processes are the main ones, which are widely used due to their high output, high reliability and excellent selectivity. Different types of pickling tanks and water washing tanks are set up to achieve the purpose of reducing metal impurities on the surface of polysilicon.

[0004] The existing electronic-grade polysilicon cleaning process in China is relatively simple, and the process is arranged in different arrangements according to different acid and alkali tanks and water tanks. For example, the prior art CN 114653658A and CN 115815204A disclose electronic-grade polysilicon cleaning methods; (1) by washing the polysilicon block with water, acid washing and spraying it in sequence to improve the uniformity of the surface morphology of the silicon block, and avoid the formation of streaks and spots on the surface of the silicon block; (2) by combining alkali washing and acid washing, the impurities on the surface of the electronic-grade polysilicon can be further removed to improve the purity of the electronic-grade polysilicon. The prior art CN 112209383 A and CN 112390259B disclose electronic-grade polysilicon and cleaning methods; (1) by setting five cleaning tanks, each cleaning tank is set with a different acid ratio to improve the cleaning effect of the silicon block and reduce the amount of cleaning liquid. (2) The first cleaning uses alkaline solution (sodium hydroxide, potassium hydroxide) to perform the first cleaning treatment on the silicon block to be cleaned, and the fourth cleaning liquid is NH4OH solution; other cleanings are mainly based on nitric acid and hydrofluoric acid, which can significantly improve the cleaning effect of the silicon block and make the silicon block as a whole more rounded, so as to facilitate downstream processing.

[0005] However, the above-mentioned existing electronic-grade polysilicon chemical cleaning process not only includes process conditions such as the type of chemical agents used, agent ratio, and reasonable process sequence, but also includes the key condition of the amount of liquid replenishment. These cleaning methods have the following problems: (1) The existing domestic electronic-grade polysilicon cleaning methods (including the above-mentioned public patents) do not describe the liquid replenishment method during the chemical cleaning process. (2) The alkaline solution (sodium hydroxide, potassium hydroxide) used in the disclosed electronic-grade polysilicon is a strong alkaline cleaning agent, and it is difficult to effectively control the K and Na indicators in the metal impurities on the surface of the electronic-grade polysilicon.

[0006] In view of this, the present invention proposes a new chemical cleaning process for electronic-grade polysilicon, which can stably control the metal impurity index on the surface of electronic-grade polysilicon at the national standard level, while extending the service life of the chemical agent. Summary of the invention

[0007] The object of the present invention is to provide a chemical cleaning process for electronic-grade polysilicon, which arranges different reagents in a certain order and concentration, and is equipped with a unique liquid replenishment method, so as to stably control the metal impurity index on the surface of electronic-grade polysilicon at the national standard level, while extending the service life of the chemical reagents.

[0008] In order to achieve the above purpose, the technical solution adopted is:

[0009] A chemical cleaning process for electronic grade polysilicon comprises: cleaning the silicon material by sequentially passing through tanks 1 to 7;

[0010] Wherein, the No. 1-3 tanks all contain hydrofluoric acid and concentrated nitric acid, and the volume percentage of the hydrofluoric acid in the tanks decreases step by step;

[0011] The No. 4 tank contains hydrofluoric acid and hydrogen peroxide;

[0012] The No. 5 tank contains hydrofluoric acid and hydrochloric acid;

[0013] The No. 6-7 tank contains high-purity water;

[0014] The concentration of the hydrofluoric acid is 49wt%;

[0015] The concentration of the concentrated nitric acid is 69wt%;

[0016] The concentration of the hydrochloric acid is 10-15wt%.

[0017] Furthermore, the No. 1 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:8-10;

[0018] The No. 2 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:20-40;

[0019] The No. 3 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:40-80;

[0020] In the No. 4 tank, the volume ratio of hydrofluoric acid and hydrogen peroxide to high-purity water is 1:1:50-70;

[0021] In the No. 5 tank, the volume ratio of hydrofluoric acid to hydrochloric acid and high-purity water is 1:1:50-70.

[0022] Furthermore, the No. 1 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:8-9;

[0023] The No. 2 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:30.

[0024] Furthermore, the No. 1 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:8.

[0025] Furthermore, the temperature of the tanks 1-3 is always less than 30°C.

[0026] Furthermore, the calculation method of the refilling of tank No. 1 is: Z1 = A1X1 - B1Y1 + C;

[0027] In the formula, Z1 represents the amount of replenishing liquid; X1 and Y1 represent the volume of hydrofluoric acid and concentrated nitric acid in tank No. 1 respectively; A1, B1, and C are constants, and their values ​​are: A1 is 68-72, and B1 is 3.8-4.2.

[0028] Furthermore, the calculation method of the refilling of tank No. 2 is: Z2 = A2X2-B2Y2+C;

[0029] In the formula, Z2 represents the amount of replenishing liquid; X2 and Y2 represent the volume of hydrofluoric acid and concentrated nitric acid in tank No. 2 respectively; A2, B2, and C are constants, and their values ​​are: A2 is 159-163, and B2 is 3.5-4.0.

[0030] Furthermore, the calculation method of the refilling of tank No. 3 is: Z3 = A3X3-B3Y3+C;

[0031] In the formula, Z3 represents the amount of replenishing liquid; X3 and Y3 represent the volume of hydrofluoric acid and concentrated nitric acid in tank No. 3 respectively; A3, B3, and C are constants, and their values ​​are: A3 is 178-182, and B3 is 1.5-2.0.

[0032] Furthermore, the C is the size of the silicon material, ranging from 10-100mm.

[0033] Furthermore, the tanks 4-5 are replenished with liquid according to a fixed liquid level.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The chemical cleaning process for electronic-grade polysilicon described in the present invention adopts a unique liquid replenishment method, which can enable the cleaning system to achieve continuous and stable replenishment of chemical agents, not only improving the service life of the chemical agents (continuous cleaning can reach 1,000 batches), but also increasing the stability of the silicon material etching thickness, effectively reducing the metal impurity content on the surface of electronic-grade polysilicon, and contributing to further improvement of the level of electronic-grade polysilicon cleaning technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the flow chart of chemical cleaning of electronic grade polysilicon. DETAILED DESCRIPTION

[0037] In order to further explain the chemical cleaning process of electronic grade polysilicon of the present invention and achieve the intended purpose of the invention, the following is a detailed description of the specific implementation method, structure, characteristics and efficacy of the chemical cleaning process of electronic grade polysilicon proposed according to the present invention in combination with the preferred embodiment. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0038] The following will further introduce in detail a chemical cleaning process for electronic grade polysilicon of the present invention in conjunction with specific embodiments:

[0039] The existing chemical cleaning process for electronic-grade polysilicon has the following problems: the chemical agent tank is replenished at a fixed liquid level, and there is a lack of batch conversion replenishment. The product quality (surface metal impurity index) is difficult to control, and the amount of chemical agents cannot be accurately controlled, which shortens the service life of chemical agents. Based on this, the technical solution of the present invention is proposed, which can effectively reduce the metal impurity content on the surface of electronic-grade polysilicon and increase the service life of the agent. The technical solution of the present invention is:

[0040] A chemical cleaning process for electronic grade polysilicon comprises: cleaning the silicon material by sequentially passing through tanks 1 to 7;

[0041] Wherein, the No. 1-3 tanks all contain hydrofluoric acid and concentrated nitric acid, and the volume percentage of the hydrofluoric acid in the tanks decreases step by step;

[0042] The No. 4 tank contains hydrofluoric acid and hydrogen peroxide;

[0043] The No. 5 tank contains hydrofluoric acid and hydrochloric acid;

[0044] The No. 6-7 tank contains high-purity water;

[0045] The concentration of the hydrofluoric acid is 49wt%; the concentration of the concentrated nitric acid is 69wt%; and the concentration of the hydrochloric acid is 10-15wt%.

[0046] Preferably, the No. 1 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:8-10;

[0047] The No. 2 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:20-40;

[0048] The No. 3 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:40-80;

[0049] In the No. 4 tank, the volume ratio of hydrofluoric acid and hydrogen peroxide to high-purity water is 1:1:50-70;

[0050] In the No. 5 tank, the volume ratio of hydrofluoric acid to hydrochloric acid to high-purity water is 1:1:50-70.

[0051] In the above technical solution, the amount of hydrofluoric acid in slots 1-5 is gradually reduced, which effectively slows down the etching rate and facilitates the control of etching thickness. At the same time, it can avoid acid spots and water marks generated by the silicon material during the transfer process (in the process of taking out the silicon material from one slot and transferring it to another slot, acid and water will remain on the surface, and the residual acid will continue to react in the air to form spots, so that spots and water marks are prone to appear during the transfer process), thereby achieving the correction effect.

[0052] In addition, the role of compounding hydrofluoric acid and hydrogen peroxide in tank No. 4 and compounding hydrochloric acid and hydrofluoric acid in tank No. 5 is that if copper impurities are contained in the metal impurities of polysilicon, the copper ions precipitated on the surface of the silicon material are the core. This core has a greater electronegativity than silicon, attracts electrons from the silicon element and is negatively charged, and then meets the positively charged copper ions to precipitate metal copper ions, so that the copper ions grow. The silicon element under the electronegativity of the copper element, on the one hand, supplies copper electrons, and on the other hand, generates silicon dioxide, which is corroded by hydrofluoric acid to form small grooves on the surface. After adding hydrogen peroxide to hydrofluoric acid, the surface of the silicon material is oxidized, and the copper ions attached to the silicon surface are also oxidized and dissolved in the cleaning solution. The electron exchange between the divalent copper ions and silicon is difficult to occur, which can effectively prevent the attachment of copper ions. In addition, adding dilute hydrochloric acid can also effectively prevent the attachment of copper ions.

[0053] Further preferably, the No. 1 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:8-9;

[0054] The No. 2 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:30.

[0055] Further preferably, the No. 1 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:8.

[0056] Preferably, the temperature of tanks 1-3 is always less than 30°C.

[0057] In the above technical solution, the temperature of tanks 1-3 is always less than 30° C., which is convenient for controlling the etching rate of the silicon material surface.

[0058] Preferably, the calculation method of the liquid replenishment of tank No. 1 is: Z1=A1X1-B1Y1+C;

[0059] In the formula, Z1 represents the amount of replenishing liquid; X1 and Y1 represent the volume of hydrofluoric acid and concentrated nitric acid in tank No. 1 respectively; A1, B1, and C are constants, and their values ​​are: A1 is 68-72, and B1 is 3.8-4.2.

[0060] Preferably, the calculation method of the liquid replenishment of tank No. 2 is: Z2=A2X2-B2Y2+C;

[0061] In the formula, Z2 represents the amount of replenishing liquid; X2 and Y2 represent the volume of hydrofluoric acid and concentrated nitric acid in tank No. 2 respectively; A2, B2, and C are constants, and their values ​​are: A2 is 159-163, and B2 is 3.5-4.0.

[0062] Preferably, the calculation method of the refill of tank No. 3 is: Z3 = A3X3-B3Y3+C;

[0063] In the formula, Z3 represents the amount of replenishing liquid; X3 and Y3 represent the volume of hydrofluoric acid and concentrated nitric acid in tank No. 3 respectively; A3, B3, and C are constants, and their values ​​are: A3 is 178-182, and B3 is 1.5-2.0.

[0064] Further preferably, the C is the size of the silicon material, ranging from 10-100 mm.

[0065] Preferably, the tanks 4-5 are replenished with liquid according to a fixed liquid level.

[0066] In the above technical solution, according to this method of fluid replenishment, continuous and stable fluid replenishment is achieved, which not only prolongs the service life of the medicine, but also maintains the stability of the process.

[0067] The purity level of the chemical reagents used in the present invention is at least UPS level.

[0068] Example 1.

[0069] Combination Figure 1 , the silicon material is cleaned in turn through tanks 1#-7#.

[0070] Tanks 1#-7# consist of 5 acid tanks and 2 water tanks. Tanks 1#-3# use hydrofluoric acid (HF) and concentrated nitric acid (HNO3), tank 4# uses HF and hydrogen peroxide (H2O2), tank 5# uses HF and hydrochloric acid (HCl), and tanks 6# and 7# use high-purity water (UPW). The concentration of hydrofluoric acid is 49wt%, the concentration of concentrated nitric acid is 69wt%, and the concentration of hydrochloric acid is 10-15wt%.

[0071] Tanks 1#-3# have concentration ratios with different corresponding relationships, and the amount of liquid replenishment after each batch of silicon material pickling has a different calculation method; no liquid replenishment system is set in tanks 4#-5#, and liquid replenishment is based on a fixed liquid level.

[0072] Specific:

[0073] On the premise that the volume of each tank is 300L, tanks 1#-7# are set as S1-S7 respectively.

[0074] The volume ratio of HF to HNO3 in S1 tank is 1:8-10, the volume ratio of HF to HNO3 in S2 tank is 1:20-40, and the volume ratio of HF to HNO3 in S3 tank is 1:40-80. The temperature of S1-S3 is controlled below 30℃ by the heat exchange system.

[0075] The reagents in the S4 tank are HF and H2O2, and the volume ratio of HF:H2O2:H2O is 1:1:50-70.

[0076] The reagents in the S5 tank are HF and HCl, and the volume ratio of HF:HCl:H2O is 1:1:50-70.

[0077] S6 and S7 are high-purity water tanks with rinsing and flushing functions.

[0078] Among them, each tank of S1, S2, and S3 has a unique method for calculating the amount of fluid replenishment, and the calculation formulas for the amount of fluid replenishment of S1, S2, and S3 are: Z1 = A1X1-B1Y1+C, Z2 = A2X2-B2Y2+C, and Z3 = A3X3-B3Y3+C;

[0079] In the formula, Z1, Z2, and Z3 represent the amount of replenishment in the S1, S2, and S3 tanks, and X and Y represent the volume of HF and HNO3 in the acid tank, respectively. A, B, and C are constants, and their values ​​are as follows: A1 is (68-72), B1 is (3.8-4.2); A2 is (159-163), B2 is (3.5-4.0); A3 is (178-182), B3 is (1.5-2.0); C is the size of the silicon material, taking the longest particle size, which ranges from 10-100mm.

[0080] Example 2.

[0081] The concentration of hydrofluoric acid was 49 wt %, the concentration of concentrated nitric acid was 69 wt %, and the concentration of hydrochloric acid was 15 wt %.

[0082] The specific steps are as follows:

[0083] On the premise that the volume of each tank is 300L, tanks 1#-7# are set as S1-S7 respectively.

[0084] ① The volume ratio of HF and HNO3 in S1 tank is 1:8, and the temperature of S1 tank is controlled below 30℃ through the heat exchange system.

[0085] The calculation method for the replenishment of tank S1 is: Z1 = A1X1-B1Y1+C;

[0086] In the formula, Z1 represents the amount of replenishment; X1 and Y1 represent the volume of hydrofluoric acid and concentrated nitric acid in tank 1 respectively; A1, B1, and C are constants, and their values ​​are: A1 is 68, B1 is 3.8, and C is the size of the silicon material. The size range of the silicon material is: 70-100mm, and the longest particle size is taken. The specific parameters are shown in the following table:

[0087] ②The volume ratio of HF and HNO3 in S2 tank is 1:20, and the temperature of S2 tank is controlled below 30℃ through the heat exchange system.

[0088] The calculation method for the replenishment of tank S2 is: Z2 = A2X2-B2Y2+C;

[0089] Wherein, Z2 represents the amount of replenishing liquid; X2 and Y2 represent the volume of hydrofluoric acid and concentrated nitric acid in tank No. 2 respectively; A2, B2 and C are constants, and their values ​​are: A2 is 159, B2 is 3.5; C is the size of silicon material, taking the longest particle size, and its range is 70-100mm.

[0090] ③The volume ratio of HF and HNO3 in S3 tank is 1:40. The temperature of S3 tank is controlled below 30℃ by heat exchange system.

[0091] The calculation method for the replenishment of tank S3 is: Z3 = A3X3-B3Y3+C;

[0092] Wherein, Z3 represents the amount of replenishing liquid; X3 and Y3 represent the volume of hydrofluoric acid and concentrated nitric acid in tank No. 3 respectively; A3, B3 and C are constants, and their values ​​are: A3 is 178, B3 is 1.5; C is the size of silicon material, taking the longest particle size, and its range is 70-100mm.

[0093] ④The reagents in S4 tank are HF and H2O2, the volume ratio of HF:H2O2:H2O is 1:1:50, and it is replenished according to a fixed liquid level.

[0094] ⑤The reagents in S5 tank are HF and HCl, and the volume ratio of HF:HCl:H2O is 1:1:50, and it is replenished according to the fixed liquid level.

[0095] ⑥S6 and S7 are high-purity water sinks with rinsing and flushing functions.

[0096] Example 3.

[0097] The concentration of hydrofluoric acid was 49 wt %, the concentration of concentrated nitric acid was 69 wt %, and the concentration of hydrochloric acid was 10 wt %.

[0098] The specific steps are as follows:

[0099] On the premise that the volume of each tank is 300L, tanks 1#-7# are set as S1-S7 respectively.

[0100] ①The volume ratio of HF and HNO3 in S1 tank is 1:9, and the temperature of S1 is controlled below 30℃ through the heat exchange system.

[0101] The calculation method for the replenishment of tank S1 is: Z1 = A1X1-B1Y1+C;

[0102] Wherein, Z1 represents the amount of replenishing liquid; X1 and Y1 represent the volume of hydrofluoric acid and concentrated nitric acid in tank No. 1 respectively; A1, B1 and C are constants, and their values ​​are: A1 is 72, B1 is 4.2, and C is the size of silicon material, taking the longest particle size, which ranges from 40-70mm.

[0103] ②The volume ratio of HF and HNO3 in the S2 tank is 1:40, and the temperature of S2 is controlled below 30°C through the heat exchange system.

[0104] The calculation method for the replenishment of tank S2 is: Z2 = A2X2-B2Y2+C;

[0105] Wherein, Z2 represents the amount of replenishing liquid; X2 and Y2 represent the volumes of hydrofluoric acid and concentrated nitric acid in tank No. 2 respectively; A2, B2 and C are constants, and their values ​​are: A2 is 163, B2 is 4; C is the size of silicon material, taking the longest particle size, and its range is 40-70mm.

[0106] ③The volume ratio of HF and HNO3 in S3 tank is 1:80. The temperature of S3 is controlled below 30℃ by the heat exchange system.

[0107] The calculation method for the replenishment of tank S3 is: Z3 = A3X3-B3Y3+C;

[0108] Wherein, Z3 represents the amount of replenishing liquid; X3 and Y3 represent the volumes of hydrofluoric acid and concentrated nitric acid in tank No. 3 respectively; A3, B3 and C are constants, and their values ​​are: A3 is 182, B3 is 2.0; C is the size of silicon material, taking the longest particle size, and its range is 40-70mm.

[0109] ④The reagents in S4 tank are HF and H2O2, the volume ratio of HF:H2O2:H2O is 1:1:60, and it is replenished according to a fixed liquid level.

[0110] ⑤The reagents in S5 tank are HF and HCl, and the volume ratio of HF:HCl:H2O is 1:1:60, and it is replenished according to the fixed liquid level.

[0111] ⑥S6 and S7 are high-purity water sinks with rinsing and flushing functions.

[0112] Example 4.

[0113] The concentration of hydrofluoric acid was 49 wt %, the concentration of concentrated nitric acid was 69 wt %, and the concentration of hydrochloric acid was 12 wt %.

[0114] The specific steps are as follows:

[0115] On the premise that the volume of each tank is 300L, tanks 1#-7# are set as S1-S7 respectively.

[0116] ①The volume ratio of HF and HNO3 in S1 tank is 1:10, and the temperature of S1 is controlled below 30℃ through the heat exchange system.

[0117] The calculation method for the replenishment of tank S1 is: Z1 = A1X1-B1Y1+C;

[0118] Wherein, Z1 represents the amount of replenishing liquid; X1 and Y1 represent the volume of hydrofluoric acid and concentrated nitric acid in tank No. 1 respectively; A1, B1 and C are constants, and their values ​​are: A1 is 69, B1 is 4.1, and C is the size of silicon material, taking the longest particle size, which ranges from 10-40mm.

[0119] ②The volume ratio of HF and HNO3 in S2 tank is 1:35, and the temperature of S2 is controlled below 30℃ through the heat exchange system.

[0120] The calculation method for the replenishment of tank S2 is: Z2 = A2X2-B2Y2+C;

[0121] Wherein, Z2 represents the amount of replenishing liquid; X2 and Y2 represent the volumes of hydrofluoric acid and concentrated nitric acid in tank No. 2 respectively; A2, B2 and C are constants, and their values ​​are: A2 is 161, B2 is 3.7; C is the size of silicon material, taking the longest particle size, and its range is 10-40mm.

[0122] ③The volume ratio of HF and HNO3 in S3 tank is 1:70. The temperature of S3 is controlled below 30℃ by the heat exchange system.

[0123] The calculation method for the replenishment of tank S3 is: Z3 = A3X3-B3Y3+C;

[0124] Wherein, Z3 represents the amount of replenishing liquid; X3 and Y3 represent the volume of hydrofluoric acid and concentrated nitric acid in tank No. 3 respectively; A3, B3 and C are constants, and their values ​​are: A3 is 179, B3 is 1.6; C is the size of silicon material, taking the longest particle size, and its range is 10-40mm.

[0125] ④The reagents in S4 tank are HF and H2O2, the volume ratio of HF:H2O2:H2O is 1:1:70, and it is replenished according to a fixed liquid level.

[0126] ⑤The reagents in S5 tank are HF and HCl, and the volume ratio of HF:HCl:H2O is 1:1:70, and it is replenished according to a fixed liquid level.

[0127] ⑥S6 and S7 are high-purity water sinks with rinsing and flushing functions.

[0128] According to the method of Examples 2-4, the specific implementation parameters and the amount of fluid replacement are shown in Table 1.

[0129] Table 1

[0130]

[0131]

[0132] Example 5.

[0133] The silicon material was cleaned by the cleaning process of Examples 2-4, and 3 batches of silicon material test samples were taken respectively. The total content of 10 kinds of metal impurities on the surface of the silicon material was detected by inductively coupled plasma mass spectrometry (ICP-MS for short). The results are shown in Table 2.

[0134] Table 2

[0135]

[0136] It can be seen from Table 2 that the total amount of metal impurities on the surface of the silicon material is controlled below 1 ng / g, and the cleaning effect is good; and the cleaning effect is stable, which also shows that the liquid replenishment method of the present invention achieves continuous and stable liquid replenishment.

[0137] The above is only a preferred embodiment of the embodiment of the present invention, and does not impose any form of limitation on the embodiment of the present invention. Any simple modification, equivalent changes and modifications made to the above embodiment based on the technical essence of the embodiment of the present invention are still within the scope of the technical solution of the embodiment of the present invention.

Claims

1. A chemical cleaning process for electronic grade polysilicon, characterized in that: The chemical cleaning process is as follows: the silicon material is sequentially cleaned through tanks 1 to 7; Wherein, the No. 1-3 tanks all contain hydrofluoric acid and concentrated nitric acid, and the volume percentage of hydrofluoric acid in the tanks decreases step by step; The No. 4 tank contains hydrofluoric acid and hydrogen peroxide; The No. 5 tank contains hydrofluoric acid and hydrochloric acid; The No. 6-7 tank contains high-purity water; The concentration of the hydrofluoric acid is 49wt%; The concentration of the concentrated nitric acid is 69wt%; The concentration of the hydrochloric acid is 10-15wt%; The calculation method of the refill of tank No. 1 is: Z1 = A1X1-B1Y1+C; In the formula, Z1 represents the amount of replenishing liquid; X1 and Y1 represent the volume of hydrofluoric acid and concentrated nitric acid in tank 1 respectively; A1, B1, and C are constants, and their values ​​are: A1 is 68-72, B1 is 3.8-4.2; The calculation method of the liquid replenishment of tank No. 2 is: Z2 = A2X2-B2Y2+C; Wherein, Z2 represents the amount of replenishing liquid; X2 and Y2 represent the volume of hydrofluoric acid and concentrated nitric acid in tank 2 respectively; A2, B2 and C are constants, and their values ​​are: A2 is 159-163, B2 is 3.5-4.0; The calculation method of the refill of tank No. 3 is: Z3 = A3X3-B3Y3+C; Wherein, Z3 represents the amount of replenishing liquid; X3 and Y3 represent the volume of hydrofluoric acid and concentrated nitric acid in tank 3 respectively; A3, B3 and C are constants, and their values ​​are: A3 is 178-182, B3 is 1.5-2.0; The C is the size of the silicon material, ranging from 10-100mm.

2. The chemical cleaning process according to claim 1, characterized in that: The No. 1 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:8-10; The No. 2 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:20-40; The No. 3 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:40-80; In the No. 4 tank, the volume ratio of hydrofluoric acid, hydrogen peroxide and high-purity water is 1:1:50-70; In the No. 5 tank, the volume ratio of hydrofluoric acid, hydrochloric acid and high-purity water is 1:1:50-70.

3. The chemical cleaning process according to claim 2, characterized in that: The No. 1 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:8-9; the No. 2 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:

30.

4. The chemical cleaning process according to claim 3, characterized in that: The No. 1 tank contains hydrofluoric acid and concentrated nitric acid in a volume ratio of 1:

8.

5. The chemical cleaning process according to claim 1, characterized in that: The temperature of the No. 1-3 tanks is less than 30°C.

6. The chemical cleaning process according to claim 1, characterized in that: The No. 4-5 tanks are replenished with liquid according to a fixed liquid level.

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