Lubricant for wire sawing of silicon wafers, method for wire sawing of silicon wafers and use thereof

Abstract

The application belongs to the technical field of silicon wafer cutting, and discloses a lubricating liquid for wire cutting of silicon wafers, a wire cutting method for silicon wafers and application of the lubricating liquid. The lubricating liquid for wire cutting of silicon wafers comprises, in percentage by mass, 20-30% of a lubricating dispersant, 15-25% of a wetting agent, 0-5% of an antifoaming agent and the balance of pure water. The lubricating dispersant is an organic amine polyether dispersant which is a polymer grafted with ethylene oxide and propylene oxide and taking organic amine as a starting agent. The wetting agent is at least one of a condensate of 8-12 carbon fatty acid methyl ester with ethylene oxide and propylene oxide and a condensate of isomeric fatty alcohol with ethylene oxide and propylene oxide. The wire cutting method for silicon wafers uses the lubricating liquid for wire cutting of silicon wafers in the cutting process. The application also discloses application of the lubricating liquid for wire cutting of silicon wafers in N-type 210 large-size half wafer multi-wire cutting. The lubricating liquid provided by the application can be matched with steel wire, has better dispersibility and wettability, and has good cutting effect on silicon wafers.

Description

Technical Field

[0001] This invention relates to the field of silicon wafer cutting technology, and more specifically, to a lubricant for wire cutting of silicon wafers, a method for wire cutting silicon wafers, and their applications. Background Technology

[0002] Silicon wafer wire cutting is a crucial upstream production step in photovoltaic cell manufacturing. This process currently mainly handles solid silicon rods, whether monocrystalline or polycrystalline. First, the silicon rods are cut into cubes, and then wire-cut into standard silicon wafers required for the cell manufacturing process. Two key factors in this process are diamond wire and lubricant. If the two are not effectively matched, various wire cutting defects and risks will occur during the wire cutting process.

[0003] During the wire cutting process, the friction between the steel wire and the silicon wafer generates a large amount of silicon powder, which increases the concentration of silicon powder in the pure water within the cutting cylinder. Therefore, the requirements for silicon powder dispersibility and wetting properties increase. As market demand for larger and thinner silicon wafers grows, conventional dispersants and wetting agents currently on the market are increasingly unable to meet the needs of silicon wafer manufacturers.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a lubricant for wire cutting of silicon wafers, a method for wire cutting of silicon wafers, and their applications.

[0006] This invention is implemented as follows:

[0007] In a first aspect, the present invention provides a lubricant for wire cutting silicon wafers, comprising, by weight percentage:

[0008] The composition includes 20-30% lubricating dispersant, 15-25% wetting agent, 0-5% defoamer, and the balance being pure water.

[0009] The lubricating dispersant is an organic amine polyether dispersant, which is a polymer grafted with ethylene oxide and propylene oxide using organic amine as an initiator.

[0010] The wetting agent is at least one of the following: a condensation product of 8-12 carbon fatty acid methyl esters and ethylene oxide and propylene oxide, and a condensation product of isomeric fatty alcohols and ethylene oxide and propylene oxide.

[0011] In an optional embodiment, the structural formula of the wetting and dispersing agent is shown in (1) or (2) below:

[0012]

[0013] In formula (1), at least one group among R1, R2, R3, and R4 is an ethylene oxide or propylene oxide segment, and a is 1 to 14. In formula (2), at least one group among R5, R6, and R7 is an ethylene oxide or propylene oxide segment; the structural formulas of the ethylene oxide and propylene oxide segments are as follows: or , where R is H or -CH3, m is 1 to 3, and n is 1 to 3.

[0014] In an optional embodiment, when non-ethylene oxide and non-propylene oxide segments are present in R1, R2, R3 and R4 in formula (1), the group is alkyl;

[0015] When non-ethylene oxide and non-propylene oxide segments are present in R5, R6 and R7 in formula (2), the group is alkyl;

[0016] The structural formula of alkyl groups is -C f H 2f+1 , where f is 1 to 6.

[0017] In an optional embodiment, the organic amine is at least one of alkylamine and ethylenediamine, and the organic amine polyether dispersant is a polymer with organic amine as the initiator and 1-2 long molecular chains of ethylene oxide and propylene oxide grafted onto the N atom.

[0018] In an optional embodiment, the wetting agent has the structural formula R-CO-R8-OCH3, where R is -C g H 2g+1 Where g is 1 to 12, and R8 is or Where h is 1 to 3 and i is 1 to 3.

[0019] In an optional implementation, the defoamer content is greater than 0%.

[0020] In an optional embodiment, the defoamer is selected from at least one of acetylenic diol defoamers and polyether-modified organosiloxanes.

[0021] Secondly, the present invention provides a method for wire cutting silicon wafers, wherein the cutting process uses a wire cutting lubricant as described in any of the foregoing embodiments.

[0022] Thirdly, the present invention provides the application of the wire cutting lubricant as described in any of the foregoing embodiments in N-type 210 large-size half-plane multi-wire cutting.

[0023] The present invention has the following beneficial effects:

[0024] The wire cutting lubricant provided in this invention contains an organic amine polyether with a large molecular spatial structure. During the cutting process, it can act as a lubricant and silica powder dispersant, thereby adsorbing heavy metal ions generated during wire cutting or in the water. It can also significantly reduce the impact on the wire cutting process, silica powder dispersion, and the white spots caused by adsorbates on the silicon wafer surface. The three-dimensional structure of the nitrogen atom in the molecular structure, combined with multiple grafted groups, enhances the steric hindrance effect, resulting in excellent cleaning and dispersing effects. Therefore, the lubricant of this invention has superior dispersing and lubricating capabilities for wire cutting of large-size silicon wafers, as well as a chelating effect on harmful components. Compared to cyclodextrin polyether dispersants, organic amine polyether dispersants can adjust their viscosity, hydrophilicity, and other properties by selecting different polyoxyalkylene structures, and the amine groups provide potentially better reactivity. Therefore, organic amine polyether dispersants have better effects in metal cleaning. Fatty acid methyl ester polyoxyethylene polyoxypropylene ether series wetting agents can provide superior wetting, penetration, dispersion, and low foaming properties. Their surface tension can be as low as 25, allowing them to carry water deep into all silicon powder particles, achieving excellent dispersion performance. Therefore, the lubricant provided by this invention has better dispersing ability compared to existing technologies, avoiding silicon powder agglomeration and deposition during the wire cutting of large-size silicon wafers, preventing surface damage to the silicon wafers, and preventing defects such as white spots and bright spots caused by residual cutting fluid in subsequent texturing processes. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0026] The following is a detailed description of the lubricant, wire cutting method, and application of the silicon wafer wire cutting provided in the embodiments of the present invention.

[0027] The wire cutting lubricant for silicon wafers provided in this embodiment of the invention comprises, by weight percentage:

[0028] The composition includes 20-30% lubricating dispersant, 15-25% wetting agent, 0-5% defoamer, and the balance being pure water.

[0029] The lubricating dispersant is an organic amine polyether dispersant, which is a polymer grafted with ethylene oxide and propylene oxide using organic amine as an initiator.

[0030] The wetting agent is at least one of the following: a condensation product of 8- to 12-carbon fatty acid methyl esters with ethylene oxide and propylene oxide, and a condensation product of isomeric fatty alcohols with ethylene oxide and propylene oxide.

[0031] The wire cutting lubricant provided in this invention contains an organic amine polyether with a large molecular spatial structure. During the cutting process, it acts as a lubricant and silica powder dispersant, thereby adsorbing heavy metal ions generated during wire cutting or in the water. It also significantly reduces the impact on the wire cutting process, silica powder dispersion, and the white spots on the silicon wafer surface caused by adsorbates. The three-dimensional structure of the nitrogen atom in the molecular structure, combined with multiple grafted groups, enhances the steric hindrance effect, resulting in excellent cleaning and dispersing performance. The introduction of the epoxy propylene group also gives it low-foaming properties, with low foam and self-eliminating foam. Therefore, the lubricant of this invention has superior dispersing and lubricating capabilities for wire cutting of large-size silicon wafers, as well as a chelating effect on harmful components. Compared to cyclodextrin polyether dispersants, organic amine polyether dispersants have better performance in metal cleaning because their viscosity, hydrophilicity, and other properties can be adjusted by selecting different polyoxyalkylene structures, and the amine groups provide potentially better reactivity.

[0032] Fatty acid methyl ester polyoxyethylene polyoxypropylene ether wetting agents offer superior wetting, penetration, dispersion, and low-foaming properties. Their surface tension can be as low as 25, allowing them to carry water deep into all silicon powder particles for excellent dispersion. The introduction of propylene oxide solves the problem of defoaming in fatty acid methyl ester polyoxyethylene ethers, and its excellent activity enables these products to perform well in solar silicon wafer processing.

[0033] The lubricant provided by this invention has a simpler composition compared to existing technologies on the market. It does not contain metal corrosion inhibitors, significantly reducing COD emissions from wire-cutting wastewater and making the wastewater easier to treat. This lubricant has excellent dispersing ability, preventing silicon powder agglomeration and deposition during the wire-cutting of large-size silicon wafers, thus avoiding surface damage and preventing defects such as white spots and bright spots caused by residual cutting fluid in subsequent texturing processes. Furthermore, due to the small amount of lubricant added and the high dilution ratio, the COD of the wastewater generated from wire cutting is also greatly reduced, resulting in more cost-effective and environmentally friendly subsequent treatment.

[0034] Furthermore, the organic amine is at least one of alkylamine and ethylenediamine, and the organic amine polyether dispersant is a polymer with organic amine as the initiator and 1-2 long molecular chains of ethylene oxide and propylene oxide grafted onto the N atom.

[0035] Furthermore, the structural formula of the wetting and dispersing agent is shown below:

[0036] In formula (1), at least one group among R1, R2, R3 and R4 is an ethylene oxide and propylene oxide segment, and a is 1 to 14. In formula (2), at least one group among R5, R6 and R7 is an ethylene oxide and propylene oxide segment.

[0037] The structural formulas of ethylene oxide and propylene oxide segments are as follows: R or Where R is H or -CH3, m is 1 to 3, and n is 1 to 3.

[0038] Furthermore, when non-ethylene oxide and non-propylene oxide segments are present in R1, R2, R3 and R4 in formula (1), the group is alkyl;

[0039] When non-ethylene oxide and non-propylene oxide segments are present in R5, R6 and R7 in formula (2), the group is alkyl;

[0040] The structural formula of alkyl groups is -C f H 2f+1 , where f is 1 to 6.

[0041] Furthermore, to improve the defoaming properties of the lubricant, the content of the defoamer can be greater than 0%.

[0042] Furthermore, the defoamer can be selected from at least one of commercially available acetylenic diol defoamers and polyether-modified organosiloxanes, with the following structural formulas respectively:

[0043]

[0044] This invention also provides a method for wire cutting silicon wafers, wherein the cutting process uses the wire cutting lubricant provided in this invention.

[0045] This invention also provides the application of the above-mentioned wire cutting lubricant in N-type 210 large-size half-plate multi-wire cutting. Because the wire cutting lubricant provided by this invention performs better in N-type 210 large-size half-plate multi-wire cutting, it is more suitable for N-type 210 large-size half-plate multi-wire cutting.

[0046] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0047] Example 1

[0048] This embodiment provides a lubricant for wire cutting, the specific components of which are:

[0049] The composition is 20% lubricating dispersant, 15% wetting agent, and the remainder is pure water.

[0050] The lubricating dispersant is ethylenediamine polyether, using ethylenediamine as the initiator, grafted with polymers of ethylene oxide and propylene oxide. Each part of ethylenediamine is mixed with one part of the polymer of ethylene oxide and propylene oxide. Additionally, methyl groups are attached to the three nitrogen-containing sites to provide a branched structure and steric hindrance. Its structural formula is:

[0051] That is, in the general formula, a is 2, m is 1, n is 1, and f is 3.

[0052] In this embodiment, the wetting agent is 10-carbon fatty acid methyl ester polyoxyethylene ether polyoxypropylene ether, and its structural formula is: That is, in the general formula, g is 10, h is 1, and i is 1.

[0053] Example 2

[0054] This embodiment provides a lubricant for wire cutting, the specific components of which are:

[0055] The composition is 22% lubricating dispersant, 15% wetting agent, and the remainder is pure water.

[0056] The lubricating dispersant is dimethylamine polyether, which is a polymer grafted with ethylene oxide and propylene oxide using dimethylamine as the initiator. Each part of dimethylamine is grafted with one part of the polymer of ethylene oxide and propylene oxide. Its structural formula is as follows:

[0057] That is, in the general formula, m is 1, n is 1, and f is 2.

[0058] In this embodiment, the wetting agent is 12-carbon fatty acid methyl ester polyoxyethylene ether polyoxypropylene ether, and its structural formula is: In the general structural formula, g is 12, h is 1, and i is 1.

[0059] Example 3

[0060] This embodiment provides a lubricant for wire cutting, the specific components of which are:

[0061] The composition consists of 18% lubricating dispersant, 20% wetting agent, and the remainder is pure water.

[0062] The lubricating dispersant is methylamine polyether, using methylamine as an initiator, grafted with polymers of ethylene oxide and propylene oxide. Each part of methylamine is grafted with 2 parts of polymers of ethylene oxide and propylene oxide. Additionally, methyl groups are grafted onto the nitrogen-containing sites to provide a branched structure and steric hindrance. Its structural formula is:

[0063] That is, in the general formula, m is 2, n is 2, and f is 1.

[0064] In this embodiment, the wetting agent is 12-carbon fatty acid methyl ester polyoxyethylene ether polyoxypropylene ether, and its structural formula is: That is, in the general formula, g is 12, h is 1, and i is 1.

[0065] Example 4

[0066] This embodiment provides a lubricant for wire cutting, the specific components of which are:

[0067] The composition is 23% lubricating dispersant, 17% wetting agent, and the remainder is pure water.

[0068] The lubricating dispersant is ethylenediamine polyether, a polymer grafted with ethylene oxide and propylene oxide using ethylenediamine as the initiator. Each part of ethylenediamine is mixed with 3 parts of the polymer of ethylene oxide and propylene oxide. Its structural formula is:

[0069] That is, in the general formula, a is 2, m is 3, n is 3, and f is 1.

[0070] In this embodiment, the wetting agent is 12-carbon fatty acid methyl ester polyoxyethylene ether polyoxypropylene ether, and its structural formula is: That is, in the general formula, g is 12, h is 1, and i is 1.

[0071] (The defoamer content in the above cases is 0%. To achieve better defoaming performance in the lubricant, the defoamer content can be greater than 0%. Therefore, no additional implementation cases containing defoamer are provided.)

[0072] Experimental Example

[0073] Large-size silicon wafer wire-cutting experiments were conducted using the examples, comparative examples, and certain commercially available lubricants. The results are shown below:

[0074]

[0075] As can be seen from the table above, the lubricant provided by this invention has significantly better flocculent rate and breakage rate compared to commercially available lubricants.

[0076] In summary, the wire cutting lubricant provided in this invention contains an organic amine polyether with a large molecular spatial structure. During the cutting process, it can act as a lubricant and a silica powder dispersant, thereby adsorbing heavy metal ions generated during wire cutting or in the water. It can also significantly reduce the impact on the wire cutting process, silica powder dispersion, and the white spot effect caused by adsorbates on the silicon wafer surface. The three-dimensional structure of the nitrogen atom in the molecular structure, combined with multiple grafted groups, enhances the steric hindrance effect, resulting in excellent cleaning and dispersing effects. Therefore, the lubricant of this invention has superior dispersing and lubricating capabilities for wire cutting of large-size silicon wafers, as well as a chelating effect on harmful components. Compared to cyclodextrin polyether dispersants, organic amine polyether dispersants can adjust their viscosity, hydrophilicity, and other properties by selecting different polyoxyalkylene structures, and the amine groups provide potentially better reactivity. Therefore, organic amine polyether dispersants have better effects in metal cleaning. Fatty acid methyl ester polyoxyethylene polyoxypropylene ether series wetting agents can provide superior wetting, penetration, dispersion, and low foaming properties. Their surface tension can be as low as 25, allowing them to carry water deep into all silicon powder particles, achieving excellent dispersion performance. Therefore, the lubricant provided by this invention has better dispersing ability compared to existing technologies, avoiding silicon powder agglomeration and deposition during the wire cutting of large-size silicon wafers, preventing surface damage to the silicon wafers, and preventing defects such as white spots and bright spots caused by residual cutting fluid in subsequent texturing processes.

[0077] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lubricant for wire cutting silicon wafers, characterized in that, By weight percentage, including: Lubricating dispersant 20-30%, wetting agent 15-25%, defoamer 0-5%, balance is pure water; The lubricating dispersant is an organic amine polyether dispersant, which is a polymer grafted with ethylene oxide and propylene oxide using organic amine as an initiator. The wetting agent is a condensation product of 10- or 12-carbon fatty acid methyl ester with ethylene oxide and propylene oxide. The structural formula of the lubricating dispersant is: , , or ; The structural formula of the wetting agent is: or .

2. The wire cutting lubricant according to claim 1, characterized in that, The content of the defoamer is greater than 0%.

3. The wire cutting lubricant according to claim 1, characterized in that, The defoamer is selected from at least one of acetylenic diol defoamers and polyether-modified organosiloxanes.

4. A method for wire cutting silicon wafers, characterized in that, The cutting process uses the wire cutting lubricant as described in any one of claims 1 to 3.

5. The application of the wire cutting lubricant as described in any one of claims 1 to 3 in N-type 210 large-size half-plane multi-wire cutting.

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