Large-size silicon wafer tungsten filament wire cutting liquid as well as preparation method and application thereof

Abstract

The invention relates to a tungsten filament wire cutting liquid for a large-size silicon wafer and a preparation method and application of the tungsten filament wire cutting liquid, and the tungsten filament wire cutting liquid comprises the following components in parts by weight: 40-60 parts of deionized water; 7-15 parts of a solubilizer; 10 to 20 parts of a wetting agent; 2-8 parts of a lubricant; and 1-8 parts of a dispersant. The dispersing agent adopted by the invention can permeate into the silicon powder to achieve good dispersity, and the wetting permeability of the dispersing agent can achieve a synergistic effect with the wetting agent, so that the cutting force is improved, and the wire breakage rate is reduced.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing processes, and particularly relates to a tungsten wire cutting fluid for large-size silicon wafers, its preparation method, and its uses. Background Technology

[0002] 1. Development History of Photovoltaic Cells

[0003] The development of photovoltaic (PV) cells is closely related to global energy transition, environmental issues, and technological advancements. Following the oil crisis of the 1970s, countries began seeking alternative energy sources to reduce their dependence on fossil fuels. Simultaneously, global warming became increasingly severe, and international conventions such as the Paris Agreement promoted the development of renewable energy, making PV, as a clean energy source with zero carbon emissions, an important choice. Technologically, the photovoltaic effect was discovered in 1839, and Bell Labs developed the first silicon-based solar cell in 1954, but its high cost limited it to the aerospace field. Subsequently, from monocrystalline silicon and polycrystalline silicon to thin-film batteries and new materials such as perovskite, efficiency has continuously improved. Advances in processes such as diamond wire cutting, PERC technology, and TOPCon have significantly reduced mass production costs; since 2020, the cost per kilowatt-hour of PV electricity has been lower than that of coal-fired power. Application scenarios are also becoming increasingly diversified. Large-scale ground-mounted PV power plants have become one of the main power sources for the grid, while residential PV and commercial / industrial rooftop PV systems are becoming widespread, achieving "self-consumption" through energy storage technology. Building-integrated photovoltaics (BIPV), PV agriculture, PV vehicles, and space-based solar power plants are expanding their application areas. Currently, photovoltaic cells are developing towards higher efficiency (such as perovskite-silicon tandem cells), lower cost, and more environmentally friendly (such as lead-free and recycling technologies), becoming one of the core pillars of the global energy transition.

[0004] 2. Diamond wire and tungsten wire cutting technology for silicon wafers

[0005] With the rapid development of the photovoltaic industry, silicon wafer cutting technology has shifted entirely from traditional wire abrasive cutting to diamond wire cutting. Diamond wire cutting uses electroplating or resin bonding methods to bond diamond abrasive to the surface of a steel wire, directly grinding and cutting the silicon rod. It has advantages such as high cutting speed, high precision, and low material loss, making it the mainstream process for manufacturing monocrystalline / polycrystalline silicon wafers.

[0006] Diamond wire cutting of silicon wafers is a core link in the photovoltaic industry chain, and a development pattern has emerged with China as the technology leader and the global market rapidly iterating. Domestic companies, leveraging their technological breakthroughs and production capacity advantages, have captured over 60% of the global cutting market share. Technologically, diamond wire is iterating towards ultra-fine wire, high wire speed, and the transition from carbon steel wire to tungsten wire.

[0007] Compared to traditional slurry cutting technology, the original diamond wire cutting technology uses carbon steel wire as the "main wire" with diamond micropowder bonded to its surface to form diamond wire. High-speed diamond wire physically grinds and cuts the material. Diamond particles remove silicon material through a combined action of "crushing friction-cutting-fracture." The bonded abrasive (diamond wire) reduces inter-particle wear compared to free-floating (slurry) abrasives, increasing the effective diamond content in the cutting process to over 60%. Key process parameter optimizations include a segmented tension system to reduce TTV exceeding limits due to wire bow vibration; increased diamond particle count per unit time at high wire speeds reduces edge chipping, but requires a low-viscosity cutting fluid to minimize thermal damage; and a spray system uses a water curtain to remove silicon powder in real time, reducing wafer contamination. Tungsten wire cutting technology, on the other hand, converts the main wire material from carbon steel to tungsten wire, further reducing the wire diameter, thereby reducing cutting losses and improving material utilization. In addition, for the same wire diameter, tungsten wire exhibits superior breaking strength and fatigue resistance compared to high-carbon steel wire, effectively reducing the breakage rate and improving cutting stability. Furthermore, tungsten wire is resistant to high temperatures and corrosion, making it more suitable for cutting large-size photovoltaic silicon wafers.

[0008] 3. Existing tungsten wire cutting fluids and their disadvantages

[0009] Existing tungsten wire cutting fluids include two main types: one is a polyethylene glycol (PEG) system, which uses PEG as the main base fluid and is compounded with rust inhibitors, emulsifiers, and defoamers. This system possesses excellent cooling performance and silicon powder suspension capabilities, making it suitable for traditional silicon wafer cutting. The other type is a small molecule alcohol-ether mixture system, which uses propylene glycol or diethylene glycol monobutyl ether as the main component, with the addition of extreme pressure agents and wetting agents. This system enhances the adhesion of the lubricating film in the cutting zone by adjusting the viscosity.

[0010] Their common disadvantages include: 1. Rapid decline in lubrication and cooling performance; after prolonged use, the lubricant (such as polyethylene glycol) degrades due to high-temperature oxidation, resulting in a decrease in the strength of the lubricating film and an increase in the wire mark rate on the silicon wafer surface; at the same time, the viscosity of the coolant increases, the chip removal capacity weakens, and silicon powder accumulation leads to an increase in the contaminated wafer rate; 2. Poor adaptability to fine wire cutting: for tungsten wire and diamond wire below 25μm, the existing cutting fluid dispersants are insufficient in their ability to coat silicon powder, resulting in an increase in silicon powder concentration and wire breakage rate in the cutting area; 3. Conflict between environmental protection and cost: most lubricants contain phosphorus or sulfur elements, which can improve lubrication, but the cost of wastewater treatment also increases accordingly.

[0011] 4. Innovation of this invention

[0012] To address these issues, the development of new cutting fluids focuses on optimizing the dispersion system by introducing special lubricating and dispersing components to reduce corrosion risks; and on developing a wetting-lubricating synergistic system adapted to the characteristics of tungsten wires to meet the high-precision cutting requirements of heterojunction N-type large-size silicon wafers. Summary of the Invention

[0013] The technical problem solved by this invention is the poor lubricity and high breakage rate of current large-size silicon wafer cutting fluids.

[0014] In view of the technical problems existing in the prior art, the present invention designs a cutting fluid with high lubricity and low wire breakage rate, which can be applied to tungsten wire cutting fluid for 210mm large-size silicon wafers, providing good cutting force and improving cutting efficiency.

[0015] It should be noted that, in this invention, unless otherwise specified, the specific meaning of "comprising" in relation to composition definition and description includes both open-ended meanings such as "comprising," "including," etc., and closed-ended meanings such as "composed of," etc., and similar meanings.

[0016] To solve the aforementioned technical problems, the present invention adopts the following solution:

[0017] [The first technical solution]

[0018] A tungsten wire cutting fluid for large-size silicon wafers, characterized in that it comprises the following components by weight:

[0019] 40-60 parts deionized water;

[0020] 7-15 parts of solubilizer;

[0021] 10-20 parts wetting agent;

[0022] 2-8 parts lubricant;

[0023] 1-8 parts of dispersant;

[0024] The dispersant is a sodium alkyl ester sulfonate derivative.

[0025] Furthermore, the dispersant is sodium dihexyl sulfosuccinate and / or sodium dioctyl sulfosuccinate.

[0026] Furthermore, the solubilizer is C 12-21 Alkyl glycosides.

[0027] Furthermore, the solubilizer described in this invention can be obtained commercially, and there is no specific limitation. For example, it can be AEG500, AEG1511 or AEG2104.

[0028] Furthermore, the lubricant is an aliphatic dicarboxylic acid diester.

[0029] Furthermore, the lubricant is a long-chain dicarboxylic acid dimethyl ester.

[0030] Furthermore, the lubricant is one or more of diethyl sebacate, dimethyl azelaate, dimethyl sebacate, dibutyl sebacate, dimethyl octanoate, and dimethyl undecanoate.

[0031] Furthermore, the wetting agent is a narrowly distributed fatty alcohol polyoxyethylene ether.

[0032] Furthermore, the structural formula of the wetting agent is C n H 2n+1 O(CH2CH2O) x H, where n is an integer from 8 to 13 and x is an integer from 3 to 9.

[0033] In this invention, in order to further optimize the performance of the tungsten wire cutting fluid for large-size silicon wafers, the components can be optimized as follows: 45-50 parts of deionized water; 10-15 parts of solubilizer; 15-20 parts of wetting agent; 3-5 parts of lubricant; and 2-5 parts of dispersant.

[0034] In this invention, the dispersant is preferably sodium dioctyl succinate sulfonate.

[0035] In this invention, the lubricant is preferably dimethyl undecanoate.

[0036] In this invention, the mass ratio of the solubilizer to the lubricant is preferably greater than 2:1.

[0037] In this invention, in the wetting agent structural formula, n is preferably an integer of 10-12, and x is preferably an integer of 4-8.

[0038] In this invention, n is preferably 10 and x is preferably 4 in the wetting agent structural formula.

[0039] In this invention, the dispersant in the tungsten wire cutting fluid for large-size silicon wafers plays a unique role:

[0040] The inventors have discovered that this dispersant has a certain penetrating ability and can quickly penetrate into the gaps between silicon powders. By dissociating the negative charges, it interacts with the negative charges on the surface of the silicon powder through the repulsion of like charges, thereby preventing the silicon powder from agglomerating. This makes the surface of the silicon wafer in the tungsten wire cutting gap more uniform, reduces friction, and lowers the wire breakage rate.

[0041] In this invention, the lubricant in the tungsten wire cutting fluid for large-size silicon wafers plays a unique role:

[0042] Firstly, the lubricant used in this invention has film-forming properties, and the polarity of the ester group will cause adsorption on the surface of the tungsten wire, which improves the stability of the lubricating film and improves the problem of wire breakage.

[0043] Secondly, since the lubricant itself is insoluble in water, and the wetting agent has a solubilizing effect on this type of lubricant, in addition, the symmetrical dimethyl ester structure of the lubricant helps the solubilizer to combine evenly with other components, thereby improving the stability of the cutting fluid.

[0044] Third, solubilizer and lubricant molecules spontaneously aggregate to form micelles or microemulsion structures. These structures have large internal space, which can encapsulate poorly soluble components, prevent the precipitation of insoluble substances, and improve the stability of the cutting fluid.

[0045] [Second Technical Solution]

[0046] A method for preparing the above-mentioned large-size silicon wafer tungsten wire cutting fluid includes the following steps:

[0047] At room temperature, add 4 / 5 of the deionized water while stirring, and add the solubilizer, wetting agent, lubricant and dispersant. Then, add the remaining deionized water while stirring continuously. Stir continuously at 20-45℃ until completely dissolved, then let stand and filter to obtain the tungsten wire cutting fluid for large-size silicon wafers.

[0048] [The third technical solution]

[0049] The above-mentioned large-size silicon wafer tungsten wire cutting fluid is used for cutting large-size solar silicon wafers, especially suitable for cutting 210mm large-size solar silicon wafers and tungsten wires with a diameter of 35μm.

[0050] This invention provides a tungsten wire cutting fluid for large-size silicon wafers, and its preparation method and uses have the following beneficial effects:

[0051] 1. The dispersant used in this invention can not only penetrate between silicon powders to achieve good dispersion, but its own wetting and penetrating properties can also work synergistically with the wetting agent to improve cutting force and reduce wire breakage rate.

[0052] 2. This invention uses alcohol ether glycosides as a solubilizer, which can effectively solubilize other components such as wetting agents and lubricants in the formulation. This not only improves the stability of the entire formulation in water, but also significantly enhances the wetting and lubrication effects of wetting agents and lubricants in actual cutting.

[0053] 3. The lubricant selected in this invention has a dimethyl ester structure, which can not only form a lubricating film on the silicon wafer surface to prevent silicon powder from adsorbing on the silicon wafer and reduce the friction between the steel wire and the silicon wafer, but also work synergistically with the solubilizer. While being solubilized by the solubilizer, it can also help the solubilizer to combine uniformly with other components. Attached Figure Description

[0054] Figure 1 : Photographs of silicon wafers cut using Example 1;

[0055] Figure 2 Photograph of the silicon wafer after cutting using Comparative Example 1. Detailed Implementation

[0056] The present invention will be further described below with reference to specific embodiments and accompanying drawings:

[0057] In this invention, Examples 1-8 and Comparative Examples 1-5 disclose a variety of cutting fluids, the components and mass ratios of which are shown in Tables 1 and 2.

[0058] Table 1. Components and proportions of tungsten wire cutting fluid for large-size silicon wafers in Examples 1-8

[0059] Table 2. Components and proportions of cutting fluids in Comparative Examples 1-5

[0060] The preparation method of the large-size silicon wafer tungsten wire cutting fluid of the present invention is as follows:

[0061] At room temperature, add 4 / 5 of the deionized water while stirring, and add the solubilizer, wetting agent, lubricant and dispersant. Then, add the remaining deionized water while stirring continuously. Stir continuously at 20-45℃ until completely dissolved, then let stand and filter to obtain the tungsten wire cutting fluid for large-size silicon wafers.

[0062] Regarding performance testing and explanation:

[0063] Performance 1 Yield:

[0064] The proportion of silicon wafers without issues such as TTV, edge chipping, or line marks to the total number of cut silicon wafers.

[0065] Performance 2: Dirt Rate

[0066] The proportion of silicon wafers with obvious silicon powder agglomerations that are difficult to clean out.

[0067] Performance 3: Wire breakage rate

[0068] The ratio of the number of cuts in which the tungsten wire broke to the total number of cuts.

[0069] All three testing methods used 35μm diameter tungsten wire to cut 210mm*210mm silicon wafers. The test results are shown in Table 3 and... Figure 1-2 .

[0070] Table 3 Test Data

[0071] Analysis and explanation of the test results:

[0072] As can be seen from the test data in Table 3, the tungsten wire cutting fluid for large-size silicon wafers in this embodiment of the invention exhibits excellent yield, low breakage rate, and low contamination rate. Specifically:

[0073] Compared with Example 1, Comparative Example 1 does not contain a dispersant. Due to the lack of a dispersant, silicon powder agglomerates severely and adheres to the silicon wafer, resulting in a higher contamination rate.

[0074] Comparative Example 2 used sodium lignosulfonate as a dispersant, which resulted in insufficient dispersibility of silicon powder. Some silicon powder agglomerated and adsorbed onto the silicon wafer, increasing the contamination rate.

[0075] Comparative Example 3 does not contain lubricant, which leads to a significant increase in frictional resistance between the tungsten wire and the silicon wafer. On the one hand, friction will increase the breakage rate of the tungsten wire, and on the other hand, it will exacerbate the problems of wire marks and scratches on the surface of the silicon wafer, thus affecting the cutting yield.

[0076] Comparative Example 4 used ethyl acetate as a lubricant, which resulted in insufficient lubrication performance and excessive frictional resistance between the tungsten wire and the silicon wafer. This caused the tungsten wire to break easily due to friction and also caused some wire marks and scratches on the silicon wafer.

[0077] Comparative Example 5 used fatty alcohol polyoxyethylene ether AEO-9 as a wetting agent, resulting in insufficient wettability. On the one hand, the cutting fluid could not quickly spread on the silicon wafer surface to form a protective film, easily causing problems such as edge chipping and wire marks. On the other hand, it also prevented the cutting fluid from quickly penetrating into the gap between the silicon wafer and the steel wire, causing the lubricant to not be able to play its full role, increasing frictional resistance and raising the wire breakage rate.

[0078] Further comparison can be made using the accompanying diagrams in the instruction manual:

[0079] Figure 1 Photographs of silicon wafers cut using Example 1; Figure 2 Photograph of the silicon wafer after it was cut, for use in Comparative Example 1.

[0080] from Figure 1-2 It can be seen that the silicon wafers cut with the cutting fluid of Example 1 have high cleanliness, with only a small amount of silicon powder residue on the surface. The silicon powder will be completely washed away in the subsequent cleaning process. However, the silicon wafers cut with the cutting fluid of Comparative Example 1 have a lot of dirt on the surface, and the silicon powder cannot be completely washed away in the subsequent cleaning process, which affects the subsequent process.

[0081] The present invention has been described above by way of example with reference to the embodiments and accompanying drawings. Obviously, the implementation of the present invention is not limited to the above-described manner. Any improvements made by adopting the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A tungsten wire cutting fluid for large-size silicon wafers, characterized in that, Based on parts by weight, it includes the following components: 40-60 parts deionized water; 7-15 parts of solubilizer; 10-20 parts wetting agent; 2-8 parts lubricant; 1-8 parts of dispersant; The dispersant is a sodium alkyl ester sulfonate derivative.

2. The tungsten wire cutting fluid for large-size silicon wafers according to claim 1, characterized in that: The dispersant is sodium dihexyl sulfosuccinate and / or sodium dioctyl sulfosuccinate.

3. The tungsten wire cutting fluid for large-size silicon wafers according to claim 1 or 2, characterized in that: The solubilizer is an alcohol ether glycoside.

4. The tungsten wire cutting fluid for large-size silicon wafers according to claim 1 or 3, characterized in that: The solubilizer is C 12-21 Alkyl glycosides.

5. The tungsten wire cutting fluid for large-size silicon wafers according to claim 1, characterized in that: The lubricant is one or more of the following: diethyl sebacate, dimethyl azelaate, dimethyl sebacate, dibutyl sebacate, dimethyl octanoate, and dimethyl undecanoate.

6. The tungsten wire cutting fluid for large-size silicon wafers according to claim 1, characterized in that: The wetting agent is a narrowly distributed fatty alcohol polyoxyethylene ether.

7. The tungsten wire cutting fluid for large-size silicon wafers according to claim 1, characterized in that: The structural formula of the wetting agent is C. n H 2n+1 O(CH2CH2O) x H, where n is an integer from 8 to 13 and x is an integer from 3 to 9.

8. The tungsten wire cutting fluid for large-size silicon wafers according to claim 1, characterized in that: The mass ratio of the solubilizer to the lubricant is greater than 2:

1.

9. A method for preparing the tungsten wire cutting fluid for large-size silicon wafers according to any one of claims 1-8, characterized in that, Includes the following steps: At room temperature, add 4 / 5 of the deionized water while stirring, and add the solubilizer, wetting agent, lubricant and dispersant. Then, add the remaining deionized water while stirring continuously. Stir continuously at 20-45℃ until completely dissolved, then let stand and filter to obtain the tungsten wire cutting fluid for large-size silicon wafers.

10. The use of the tungsten wire cutting fluid for cutting large-size silicon wafers according to any one of claims 1-8 in cutting large-size solar silicon wafers.

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