High-clean water-based cutting fluid for multi-wire sawing of silicon wafers and preparation method thereof

Abstract

This invention discloses a high-purity water-based cutting fluid for multi-wire cutting of silicon wafers and its preparation method, belonging to the field of semiconductor processing fluid technology. The cutting fluid is composed of the following components in parts by weight: 70.0–85.0 parts ultrapure water, 10.0–20.0 parts polyethylene glycol-400, 3.0–5.0 parts polyethylene glycol-3350, 1.0–1.8 parts methylethanolamine, 0.5–1.0 parts lauroyl amino acid ester, 0.8–1.5 parts isotridecyl polyoxyethylene ether, 0.05–0.1 parts pyridinecarboxylic acid, and 0.05–0.15 parts polyether-modified siloxane defoamer. This invention constructs a lubricating suspension system that balances low viscosity and high abrasive suspension stability by compounding high molecular weight polyethylene glycol-3350 and low molecular weight polyethylene glycol-400 in a specific ratio. Simultaneously, through the molecular synergy of methylethanolamine, lauroyl amino acid ester, and pyridinecarboxylic acid, a highly efficient and easy-to-clean rust-preventive system is constructed. This formulation is free of solid lubricating particles, elements detrimental to semiconductor processes (B, S, P, Cl), and chemical bactericides, eliminating the risk of contamination at the source. While ensuring high lubrication, strong rust prevention, and good cooling and cleaning performance, it meets the extreme cleanliness requirements of semiconductor manufacturing processing fluids, making it particularly suitable for multi-wire silicon wafer dicing processes.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor processing fluid technology, specifically relating to a high-purity water-based cutting fluid that can be used for multi-wire cutting of silicon wafers in semiconductor manufacturing processes. Background Technology

[0002] Water-based cutting fluids are crucial auxiliary materials in semiconductor wafer cutting, grinding, and other processing steps, and their performance directly affects tool life, machining accuracy, workpiece surface quality, and production costs. An ideal semiconductor cutting fluid must simultaneously meet the following requirements: high lubricity, excellent rust prevention, superior cleaning properties, excellent chemical compatibility, environmental and operator friendliness, and, most importantly, "semiconductor-grade cleanliness." This "semiconductor-grade cleanliness" refers not only to macroscopic cleanliness but also requires that the cutting fluid itself and any residues after use must not introduce any physical, chemical, or biological contaminants that could affect device performance.

[0003] In recent years, the industry has explored various approaches to address the increasingly stringent requirements for lubrication, cooling, and cleanliness in semiconductor cutting. However, existing technologies, in pursuing a single performance indicator, often inevitably introduce new risks or sacrifice other key performance aspects. As a result, there is still room for improvement in simultaneously meeting multiple performance requirements such as lubrication, cooling, abrasive suspension stability, and ease of cleaning while maintaining high cleanliness.

[0004] Firstly, in pursuing ultra-high lubrication and extreme pressure performance, some solutions tend to introduce solid nanoparticles. For example, existing technologies (such as CN115948193B) use hard inorganic particles with a Mohs hardness of 8 or higher, such as zirconium oxide and tungsten carbide, to reduce friction through their "micro-bearing" effect. However, this inevitably brings the risk of physical contamination from hard particles embedding or scratching the silicon wafer surface, and these particles are difficult to clean thoroughly. Other technologies (such as CN116751617B and CN115960671B) rely on complex nanocomposite materials (such as porous graphene oxide loaded with lubricant and boron nitride composites). These materials themselves are submicron or nanoscale solid particles, which have similar risks of residue and scratching, and their synthesis processes are cumbersome and costly.

[0005] Secondly, in enhancing rust prevention and antibacterial properties, some formulations rely on adding compounds containing elements contraindicated in semiconductor processes, such as sulfur, phosphorus, chlorine, and boron (e.g., CN113563959B). While this improves specific properties, it introduces potential risks of chemical and ionic contamination, and the bactericide itself may become a new pollutant.

[0006] Third, in the pursuit of solutions that aim to avoid the aforementioned contamination and achieve high cleanliness, balancing performance often presents challenges. For example, while using only low molecular weight polyethylene glycol (such as CN1858169A) can ensure good cooling and easy cleaning, its suspension stability for cutting abrasives is insufficient, easily leading to sedimentation and affecting cutting uniformity and surface quality. On the other hand, excessively increasing the viscosity of the system to improve suspension will impair its penetration, cooling, and subsequent cleaning capabilities.

[0007] In summary, how to construct a water-based cutting fluid system that combines high lubricity, strong rust prevention, excellent abrasive suspension stability, and inherent cleanliness without relying on solid particles is a pressing technical problem in this field. Although polyethylene glycol (PEG) is widely recognized as a basic lubricant, existing technologies typically use single conventional molecular weight PEGs (such as PEG200-1000), primarily focusing on adjusting viscosity and lubricity. There are no systematic reports on how to achieve excellent abrasive suspension stability through precise blending of specific high molecular weight PEGs (such as PEG-3350) and low molecular weight PEGs (such as PEG-400) without compromising their flow permeability and subsequent cleaning properties under high shear, and how to coordinate with specific rust inhibitor systems to meet the extreme requirements of "zero contamination" and "ultra-cleanliness" in semiconductor processing.

[0008] This invention aims to solve the core technical challenge of balancing lubrication performance and environmental safety in existing water-based cutting fluids for semiconductor cutting applications, particularly addressing bottlenecks such as hard particle residue pollution, the presence of restricted harmful elements, complex and costly formulations, and poor biodegradability. By employing an innovative strategy of "polyethylene glycol compound lubrication" and "molecular synergistic rust prevention," a green lubrication system achieving synergistic "lubrication-cooling-suspension" is creatively constructed by compounding polyethylene glycols of different molecular weights. This system eliminates the risk of scratches from hard particles by eliminating the addition of solid nanoparticles. A molecular synergistic rust-preventive protective layer is constructed using methylethanolamine, lauroyl amino acid ester, and pyridine carboxylic acid, providing multiple layers of protection for silicon wafers and equipment metal. Simultaneously, the addition of isomeric tridecyl alcohol polyoxyethylene ether further enhances the efficient wetting and suspension system, ensuring both excellent cleaning performance and uniform abrasive suspension. Ultimately, this results in a new water-based cutting fluid system that combines high-performance lubrication, excellent rust prevention, inherent environmental friendliness, and easy cleaning, making it particularly suitable for precision semiconductor wafer cutting applications requiring extremely high machining accuracy and cleanliness. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the shortcomings of existing water-based cutting fluids used for multi-wire cutting of silicon wafers, which are difficult to balance excellent lubricity, good cooling, long-lasting rust prevention and excellent abrasive suspension stability when pursuing high cleanliness. The present invention provides a high-cleanliness water-based cutting fluid and its preparation method that is free of solid lubricating particles, process-restricted elements, and chemical bactericides, and has a balanced comprehensive performance.

[0010] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0011] On one hand, the present invention provides a high-purity water-based cutting fluid for multi-wire cutting of silicon wafers, which is composed of the following components in parts by weight:

[0012] 70.0–85.0 parts of ultrapure water;

[0013] Polyethylene glycol-400: 10.0–20.0 parts;

[0014] Polyethylene glycol-3350: 3.0–5.0 parts;

[0015] 1.0–1.8 parts of methylethanolamine;

[0016] Lauroyl amino acid ester 0.5-1.0 parts;

[0017] 0.8–1.5 parts of isomeric tridecyl alcohol polyoxyethylene ether;

[0018] Pyridinecarboxylic acid 0.05–0.1 parts;

[0019] 0.05-0.15 parts of polyether-modified siloxane defoamer.

[0020] The water-based cutting fluid is a homogeneous liquid system, containing no intentionally added solid lubricating particles, such as zirconium oxide or boron nitride nanoparticles. The technical solution of this invention is achieved through the following synergistic system:

[0021] (1) Polyethylene glycol compound lubricating suspension system: This system is composed of low molecular weight polyethylene glycol-400 and high molecular weight polyethylene glycol-3350 in a specific ratio. Polyethylene glycol-400 contributes good fluid lubrication, efficient cooling capacity, and helps maintain a low dynamic viscosity of the system, thereby ensuring the penetration efficiency of the cutting fluid in high-speed cutting and subsequent cleanability. Polyethylene glycol-3350 (average molecular weight of about 3350) is completely dissolved and uniformly dispersed in the system by heating and stirring during the preparation process. Its long molecular chains entangle with each other in the aqueous phase to form a dynamic network structure, which endows the system with excellent abrasive suspension potential. Through a large number of experiments, this invention has found that when the weight ratio of polyethylene glycol-400 to polyethylene glycol-3350 is controlled between 2:1 and 6.67:1, the compound system can achieve excellent and long-lasting suspension stability of abrasives while maintaining low viscosity characteristics that are conducive to cooling and cleaning. Within this range, when the weight ratio of the two components is further optimized to 4:1 to 5:1, the system achieves a better balance between lubrication and anti-wear performance and suspension stability. This specific compounding relationship effectively synergizes the two often mutually restrictive performance parameters of low viscosity and high suspension stability, thereby resolving the related technical contradictions.

[0022] (2) Molecular Synergistic Rust Inhibition System: This system consists of methylethanolamine, lauroyl amino acid ester, and pyridine carboxylic acid, which work synergistically through multiple mechanisms to exert a long-lasting rust inhibitory effect. Methylethanolamine, as an organic base, primarily functions to quickly adjust and stabilize the pH of the system within a weakly alkaline range (8.2-8.8), creating a chemical environment unfavorable to metal corrosion. Lauroyl amino acid ester, with its long-chain alkyl hydrophobic tail and amino acid polar head in its molecular structure, can be directionally adsorbed onto the surface of metals and silicon wafers, forming a dense physical adsorption isolation film that blocks direct contact with corrosive media. Pyridine carboxylic acid, as a highly efficient metal chelating agent, has nitrogen atoms and carboxyl groups in its molecule that can form stable five-membered ring chelates with metal ions, thereby generating a chemical passivation film on the surface of the metal substrate. The synergistic mechanism of the three is as follows: the alkaline environment established by methylethanolamine provides a stable interface for the subsequent film formation process; lauroyl amino acid ester spreads rapidly to form a physical barrier; and pyridine carboxylic acid further strengthens the protective layer through chemical bonding. This multi-layered synergy of "environmental regulation, physical shielding, and chemical passivation" enables the rust prevention system to provide Class A long-lasting rust protection that surpasses that of a single component. Furthermore, the composite protective film can be effectively removed in subsequent standard ultrapure water cleaning processes without leaving any residue.

[0023] (3) Intrinsically Clean System: This invention adheres to the principle of "intrinsically clean" from the very beginning of the formulation design. All selected components are free of elements such as boron (B), sulfur (S), phosphorus (P), and chlorine (Cl), which are contraindicated in semiconductor processes, thus fundamentally avoiding the risk of contamination from these impurity ions. At the same time, the system completely eliminates any chemical bactericides. Its microbial control relies on strict raw material cleanliness, a clean environment during preparation, and physical filtration maintenance during use, thereby completely eliminating the risk of chemical contamination caused by the decomposition or residue of bactericides.

[0024] In the water-based cutting fluid:

[0025] The polyethylene glycol-400 and polyethylene glycol-3350 are used together as lubricants, wherein the mass percentage of polyethylene glycol-400 is 10.0% to 20.0% and the mass percentage of polyethylene glycol-3350 is 3.0% to 5.0%.

[0026] The methylethanolamine, lauroyl amino acid ester, and pyridine carboxylic acid are used together as rust inhibitors, wherein the mass percentage of methylethanolamine is 1.0% to 1.8%, the mass percentage of lauroyl amino acid ester is 0.5% to 1.0%, and the mass percentage of pyridine carboxylic acid is 0.05% to 0.1%.

[0027] The surfactant is isomeric tridecyl alcohol polyoxyethylene ether (ethylene oxide addition number EO=8-10), with a mass percentage of 0.8% to 1.5%. Its main function is to significantly reduce the surface tension of the system and promote the rapid wetting and spreading of the cutting fluid on the silicon wafer, cutting line and abrasive surface, thereby optimizing cooling efficiency and cleaning effect.

[0028] The defoamer is a polyether-modified siloxane defoamer with a mass percentage of 0.05% to 0.15%. This defoamer has good compatibility with the polyethylene glycol system, can effectively suppress foam generated by high-speed stirring and surfactants during processing, and is easy to clean with low residual risk.

[0029] The methylethanolamine also acts as a pH stabilizer, precisely stabilizing the pH of the cutting fluid within a weakly alkaline range of 8.2-8.8. This pH environment is most conducive to the effectiveness of the aforementioned synergistic rust prevention system and has good compatibility with common semiconductor materials such as silicon, copper, and aluminum.

[0030] The ultrapure water has a resistivity ≥18.2 MΩ·cm and a mass percentage of 70.0% to 85.0%, serving as the basic solvent to ensure that the entire cutting fluid system achieves semiconductor-grade cleanliness.

[0031] On the other hand, the present invention provides a method for preparing the above-mentioned water-based cutting fluid, comprising the following steps:

[0032] Step 1 - Preparation of the basic aqueous phase: In a mixing vessel with a cleanliness level of not less than 1000, add 60% to 70% of the total volume of ultrapure water. Start stirring (300 to 500 rpm), and add the prescribed amounts of methylethanolamine, lauroyl amino acid ester, and pyridinecarboxylic acid sequentially. Continue stirring for 10 to 15 minutes until all components are completely dissolved, forming a homogeneous and transparent solution.

[0033] Step 2 - Polyethylene Glycol Dissolution: While stirring, slowly add the prescribed amounts of polyethylene glycol-400 and polyethylene glycol-3350 to the solution obtained in Step 1. Heat the mixture to 50℃±2℃ and continue stirring at this temperature and a stirring rate of 500~800 rpm for 30~45 minutes until polyethylene glycol-3350 is fully swollen and dispersed, and the system returns to a homogeneous viscous liquid. This step is crucial for forming the dynamic viscoelastic lubrication-suspension synergistic system.

[0034] Step 3 - Adding Surfactants and Defoamers: Cool the mixture to room temperature (25℃±3℃). While stirring, add the formulated amounts of isomeric tridecyl alcohol polyoxyethylene ether and polyether-modified siloxane defoamer sequentially, stirring for 10-15 minutes to ensure uniform mixing.

[0035] Step 4 - Final Dilution and pH Adjustment: Add the remaining ultrapure water to the above solution to dilute the cutting fluid to the target concentration. Use a trace amount of methylethanolamine to precisely adjust the pH of the cutting fluid, stabilizing it within the target range of 8.2–8.8.

[0036] Step 5 - Terminal Filtration and Filling: The prepared cutting fluid is terminally filtered through a polytetrafluoroethylene (PTFE) filter element with a pore size ≤0.2 μm to remove any trace amounts of insoluble matter or mechanical impurities. The filtered product is then filled in a clean environment to obtain the high-purity water-based cutting fluid.

[0037] Beneficial effects

[0038] Compared with the prior art, the water-based cutting fluid of the present invention has the following outstanding advantages for multi-wire cutting of semiconductor silicon wafers:

[0039] (1) It fundamentally eliminates the risk of physical contamination introduced by solid particles. By using a completely soluble polyethylene glycol compound system as the core lubrication-suspension medium, it avoids the problem of scratches and residues on the silicon wafer surface caused by hard particles.

[0040] (2) It completely avoids chemical pollution caused by taboo elements and chemical disinfectants. The formula components do not contain harmful elements such as B, S, P, and Cl, and rely on a molecular synergistic rust prevention system to achieve Class A rust prevention. After cleaning, the residual key harmful elements on the silicon wafer surface are extremely low, and no chemical disinfectants need to be added.

[0041] (3) It innovatively balances lubrication, cooling, suspension, and cleaning performance. By compounding PEG-400 and PEG-3350 in a specific ratio, while maintaining low viscosity to facilitate cooling and cleaning, the dynamic network structure formed enhances the system stability and abrasive suspension ability, thus contributing to better cutting surface quality. Combined with a highly efficient molecular synergistic rust prevention system, it achieves optimization of comprehensive performance.

[0042] (4) The preparation process is simple, the raw materials are readily available, and there is no need for high temperature, high pressure, vacuum or complex chemical reaction steps, making it suitable for large-scale production. Attached Figure Description

[0043] Figure 1 The wear scar diameter (a) and the corresponding friction coefficient curve (b) of the water-based cutting fluid prepared in Example 1 of this invention are shown.

[0044] Figure 2 The wear scar diameter (a) and the corresponding friction coefficient curve (b) of the water-based cutting fluid prepared in Example 2 of this invention are shown.

[0045] Figure 3 The wear scar diameter (a) and the corresponding friction coefficient curve (b) of the water-based cutting fluid prepared in Example 3 of this invention are shown.

[0046] Figure 4 The wear scar diameter (a) and the corresponding friction coefficient curve (b) of the water-based cutting fluid prepared in Comparative Example 1 of this invention are shown.

[0047] Figure 5 The wear scar diameter (a) and the corresponding friction coefficient curve (b) of the water-based cutting fluid prepared in Comparative Example 2 of this invention are shown.

[0048] Figure 6 The wear scar diameter (a) and the corresponding friction coefficient curve (b) of the water-based cutting fluid prepared in Comparative Example 3 of this invention are shown.

[0049] Figure 7 The wear scar diameter (a) and the corresponding friction coefficient curve (b) of the water-based cutting fluid prepared in Comparative Example 4 of this invention are shown.

[0050] Figure 8 The surface microstructure (a) and its energy dispersive spectroscopy (EDS) diagram (b) obtained after silicon wafer cutting using the water-based cutting fluid prepared in Example 1 of this invention and standard cleaning.

[0051] Figure 9 The surface microstructure (a) and its energy dispersive spectroscopy (EDS) diagram (b) obtained after cutting a silicon wafer using the water-based cutting fluid prepared in Comparative Example 1 of this invention and performing standard cleaning are shown in the figure. The nanoscale particles are marked with red arrows. Detailed Implementation

[0052] The technical solution of the present invention will be further described below with reference to specific embodiments. The scope of protection of the present invention is not limited to the following embodiments; these examples are provided for illustrative purposes only and do not limit the present invention in any way.

[0053] It should be noted that the terms "free of solid lubricating particles" and "uniform transparent liquid" used in this invention refer to the cutting fluid formulation itself and its factory state, and do not contain any intentionally added, insoluble solid lubricating substances. In actual use, users may add cutting abrasives such as silicon carbide according to process requirements, which is unrelated to the formulation design of this invention.

[0054] Example 1

[0055] The preparation of the water-based cutting fluid in this embodiment includes the following steps:

[0056] In an environment with a cleanliness level of not less than 1000, prepare the following ingredients: 778.2 g of ultrapure water (resistivity ≥18.2 MΩ·cm), 150.0 g of polyethylene glycol-400, 35.0 g of polyethylene glycol-3350 (average molecular weight approximately 3350), 12.0 g of methylethanolamine, 6.0 g of lauroyl amino acid ester, 12.0 g of isomeric tridecyl alcohol polyoxyethylene ether (EO=9), 0.6 g of pyridine carboxylic acid, and 1.2 g of polyether-modified siloxane defoamer.

[0057] The preparation steps are as follows:

[0058] (1) Dissolving the rust inhibitor: In a clean mixing vessel, add about 500 g of ultrapure water. Turn on the stirring (400 rpm) and add methylethanolamine, lauroyl amino acid ester and pyridine carboxylic acid in sequence, stirring for 15 minutes until completely dissolved.

[0059] (2) Dissolving polyethylene glycol: While stirring, add polyethylene glycol-400 and polyethylene glycol-3350 to the above solution in sequence. Heat the mixture to 50°C and increase the stirring speed to 600 rpm. Keep stirring under these conditions for 40 minutes until polyethylene glycol-3350 is fully swollen and dispersed and the system is homogeneous.

[0060] (3) Add surfactant and defoamer: Stop heating and cool to room temperature. Add isotridecyl alcohol polyoxyethylene ether and polyether modified siloxane defoamer while stirring, and continue stirring for 15 minutes.

[0061] (4) Volume adjustment and pH adjustment: Add the remaining ultrapure water and stir for 30 minutes to homogenize the system. Adjust the pH to 8.5 precisely with a trace amount of methylethanolamine.

[0062] (5) Terminal filtration: The prepared liquid is filtered through a 0.2 μm polytetrafluoroethylene (PTFE) filter element to obtain the water-based cutting fluid, which is labeled as sample S-1.

[0063] Example 2

[0064] The preparation of the water-based cutting fluid in this embodiment includes the following steps:

[0065] Following the preparation method of Example 1, the amounts of each component were adjusted as follows: 750.0 g of ultrapure water, 200.0 g of polyethylene glycol-400, 30.0 g of polyethylene glycol-3350 (average molecular weight approximately 3350), 18.0 g of methylethanolamine, 5.0 g of lauroyl amino acid ester, 8.0 g of isomeric tridecyl alcohol polyoxyethylene ether (EO=10), 1.0 g of pyridine carboxylic acid, and 1.5 g of polyether-modified siloxane defoamer.

[0066] After stirring evenly and filtering through a 0.2 μm polytetrafluoroethylene filter, the water-based cutting fluid was obtained and labeled as sample S-2.

[0067] Example 3

[0068] The preparation of the water-based cutting fluid in this embodiment includes the following steps:

[0069] Following the preparation method of Example 1, the amounts of each component were adjusted as follows: 850.0 g of ultrapure water, 100.0 g of polyethylene glycol-400, 50.0 g of polyethylene glycol-3350 (average molecular weight approximately 3350), 10.0 g of methylethanolamine, 10.0 g of lauroyl amino acid ester, 15.0 g of isomeric tridecyl polyoxyethylene ether (EO=8), 0.5 g of pyridine carboxylic acid, and 0.5 g of polyether-modified siloxane defoamer.

[0070] After stirring evenly and filtering through a 0.2 μm polytetrafluoroethylene filter, the water-based cutting fluid was obtained and labeled as sample S-3.

[0071] Comparative Example 1

[0072] Zirconia nanoparticles (D50=100nm, Mohs hardness>8) were used instead of the polyethylene glycol compound system in this invention, with an addition amount of 20.0 g. The remaining components and preparation methods were the same as in Example 1, resulting in comparative sample C-1.

[0073] Comparative Example 2

[0074] Without adding pyridine carboxylic acid, the remaining components and preparation method were the same as in Example 1, resulting in comparative sample C-2.

[0075] Comparative Example 3

[0076] Using only polyethylene glycol-400 (190.0 g) and excluding polyethylene glycol-3350, with the other components the same as in Example 1, comparative sample C-3 was obtained.

[0077] Comparative Example 4

[0078] Using 150.0 g of polyethylene glycol-400 and replacing 35.0 g of polyethylene glycol-8000 with polyethylene glycol-3350, with the remaining components the same as in Example 1, comparative sample C-4 was obtained.

[0079] Comparative Example 5

[0080] Based on the formulation of Example 1, lauroyl amino acid ester was removed, while the remaining components and preparation method remained unchanged, resulting in comparative sample C-5.

[0081] Comparative Example 6

[0082] Based on the formulation of Example 1, pyridine carboxylic acid and lauroyl amino acid ester were removed, and only methylethanolamine was retained as a rust inhibitor. The remaining components and preparation method remained unchanged, resulting in comparative sample C-6.

[0083] Performance testing

[0084] Test Example 1: Evaluation of Basic Lubrication and Anti-wear Performance

[0085] The basic lubrication performance of the water-based cutting fluid samples S-1 to S-3 prepared in Examples 1-3 of this invention, as well as the comparative samples C-1, C-2, C-3, and C-4, was tested using the following methods:

[0086] The friction was evaluated using an MS-10A four-ball friction testing machine. The friction pair consisted of four φ12.7 mm GCr15 bearing steel balls. The experimental conditions were fixed as follows: normal load 392 N, spindle speed 1200 r / min, and test time 30 min. Before testing, the steel balls were ultrasonically cleaned and dried sequentially in petroleum ether and ethanol. During the test, the working fluid (5% concentration) was injected into the oil tank, completely submerging the bottom three steel balls. The testing machine was started, and the friction coefficient was continuously recorded. After the test, the wear scar diameter (WSD) of any one of the bottom three steel balls was measured using an optical microscope. The test results are shown in [Figure number missing]. Figure 1-7 .

[0087] Results analysis:

[0088] Depend on Figure 1-7It can be seen that the wear scar diameters of the samples (S-1 to S-3) obtained in Examples 1-3 of this invention are all smaller than those of the comparative sample, and the average friction coefficient is lower and the stability is better. Among them, Example 1 (S-1) exhibits the best comprehensive anti-wear and friction-reducing performance. Comparative Example 3 (C-3) lacks PEG-3350, and its anti-wear performance (wear scar diameter) and friction coefficient stability are both reduced, proving the synergistic effect of the compound system. Although Comparative Example 4 (C-4) has the same total PEG content, its wear scar diameter (0.48 mm) and friction coefficient stability are significantly worse than those of Example 1 (0.38 mm). This directly proves that using a specific high molecular weight PEG-3350 and PEG-400 compound, compared with the use of other high molecular weight PEGs (such as PEG-8000) (Comparative Example 4, C-4), can bring unexpected improvements in anti-wear performance. Although the wear scar diameter of Comparative Example 1 (C-1) is acceptable, the friction curve fluctuates greatly, indicating that the lubrication state of solid particles is unstable.

[0089] Test Example 2: Rust Prevention and Foaming Properties Test

[0090] The rust-preventive properties and foaming properties of the water-based cutting fluid samples S-1 to S-3 prepared in Examples 1-3 of this invention and the comparative samples C-1 to C-6 were tested using the following methods:

[0091] Rust prevention performance was evaluated using the cast iron single-piece method according to GB / T 6144 standard. Standard cast iron test pieces were polished and cleaned, then immersed in a 5% concentration of the test cutting fluid working solution and placed in a humidification tank at (35±2)℃ for 24 hours. After the test, the test pieces were removed to observe surface rust and were rated. To further evaluate the compatibility of the cutting fluid with common metals in semiconductor processing equipment, copper and aluminum sheet immersion tests were conducted in accordance with relevant principles in the SEMI standard. Clean brass sheets (H62) and aluminum alloy sheets (6061) were completely immersed in a 5% concentration of the test cutting fluid working solution and sealed at (55±2)℃ for 168 hours (7 days). After the test, the sheets were removed, rinsed with ultrapure water, dried, and the surfaces were visually inspected and observed under an optical microscope for discoloration, pitting, or corrosion marks. The foaming test was also conducted according to GB / T 6144 standard. 100 mL of working solution was measured into a stoppered graduated cylinder, and the solution was vigorously shaken at a constant temperature of (25±1)℃ for 10 minutes. The foam volume was recorded immediately afterward. The test results are shown in Table 1.

[0092] Results analysis:

[0093] As shown in Table 1, the water-based cutting fluid samples (S-1 to S-3) obtained in Examples 1-3 of this invention all reached the highest Grade A (rust-free) standard in the rust prevention performance test. The rust prevention grades of Comparative Example 5 (C-5), Comparative Example 2 (C-2), and Comparative Example 6 (C-6) decreased sequentially, fully demonstrating that the "molecular synergistic rust prevention system" composed of methylethanolamine, lauroyl amino acid ester, and pyridinecarboxylic acid is indispensable, and its synergistic effect is far superior to single or two-component formulations. Regarding foaming properties, the foam volume of the example samples was controlled below 30 mL due to the use of polyether-modified siloxane defoamer, meeting processing requirements. However, Comparative Example 1 (C-1), containing solid particles, exacerbated foam generation and stability, resulting in the largest foam volume. All samples showed no corrosion to aluminum, indicating good formulation compatibility.

[0094] Table 1: Results of Rust Prevention and Foaming Tests

[0095] Test Example 3: Evaluation of Multi-Wire Cutting Performance of Silicon Wafers

[0096] The water-based cutting fluid samples S-1 to S-3 prepared in Examples 1-3 of this invention, as well as comparative samples C-1, C-2, C-3, C-4 and a commercially available semiconductor cutting fluid (D-1), were evaluated using real multi-wire cutting processes. The testing methods are as follows:

[0097] Following standard practices for evaluating semiconductor silicon wafer dicing processes, a 6-inch single-crystal silicon ingot was diced using the same multi-wire dicing machine under fixed process parameters (wire diameter, wire speed, feed rate). The cutting fluid concentration was consistently 5%. After dicing, silicon wafers were randomly selected and sequentially ultrasonically cleaned with standard ultrapure water and dried with nitrogen. The average chipping size (ACS) of the diced edges was measured using a laser confocal microscope; the surface roughness (Ra) of the diced surface was measured using a white light interferometer; and the wire saw wear during the dicing process was recorded. The test results are shown in Table 2.

[0098] Results analysis:

[0099] As shown in Table 2, the silicon wafers cut using the cutting fluid of this invention exhibit significantly better processing quality than the comparative examples and commercially available products. The sample examples demonstrate the best performance in terms of edge integrity and surface finish. Furthermore, compared to commercially available semiconductor cutting fluids, the formulation of this invention effectively reduces wire saw wear and extends tool life. This test directly proves that the cutting fluid of this invention can achieve high-precision, low-damage cutting in real-world machining.

[0100] Table 2: Results of Multi-Wire Cutting Processing Performance of Silicon Wafers

[0101] Test Example 4: Analysis of Silicon Wafer Surface Cleanliness and Contaminants

[0102] The surface cleanliness and contaminant analysis of the silicon wafers cut in Test Example 3 were performed using the following methods:

[0103] (1) Morphology and Elemental Analysis: Silicon wafers cut and cleaned using the water-based cutting fluids prepared in Example 1 (S-1) and Comparative Example 1 (C-1) were selected as representative research objects. Field emission scanning electron microscopy and a matching energy dispersive spectroscopy (SEM / EDS) were used to observe the cut surfaces of the silicon wafers. The surface micromorphology was observed at an accelerating voltage of 5 kV, and surface scanning elemental analysis was performed within a 1 μm × 1 μm area. The results are shown in […]. Figure 8 and 9 .

[0104] (2) Analysis of metallic contaminants on silicon wafer surface: In accordance with SEMI standards, inductively coupled plasma mass spectrometry (ICP-MS) was used to quantitatively analyze the surface of the cleaned silicon wafers. The silicon wafers were placed in a sealed container, and high-purity nitric acid vapor was used to contact the surface to dissolve and collect the contaminants. The content of key metal ions was detected, and the results were expressed as mass concentration per unit area (ng / cm²). The detection results are shown in Table 3.

[0105] (3) Hazardous elements in cleaning residue: To quantify the residual levels of migratable hazardous elements on the surface of silicon wafers after cutting and standard cleaning, the actual cleaning process was simulated, and the ultrapure water used for the final rinsing of the silicon wafers was collected as a "surface cleaning residue" sample. Inductively coupled plasma mass spectrometry (ICP-MS) equipped with a collision / reaction cell was used to detect the content of boron (B), phosphorus (P), and sulfur (S), with method detection limits of 0.1 ppb, 0.05 ppb, and 1 ppb, respectively. Ion chromatography (IC) was used to detect the content of chlorine (Cl), with a detection limit of 0.1 ppb according to SEMI C7 standards. The detection results are shown in Table 3.

[0106] Table 3: Analysis Results of Contaminants and Harmful Elements in Cleaning Residue on Silicon Wafer Surfaces

[0107] Results analysis:

[0108] (1) Surface morphology and elemental residue analysis:

[0109] SEM / EDS analysis showed that the silicon wafer cut using sample S-1 of this embodiment of the invention had a smooth and clean surface. Figure 8 a) The EDS spectrum only showed characteristic peaks for silicon (Si) and oxygen (O), and no other anomalous elemental signals were detected. Figure 8 b). This indicates that the formulation system of the present invention does not introduce solid residues during the cutting process, and that the formulation components have no adsorption residues after cleaning.

[0110] In contrast, the silicon wafers cut using Comparative Example C-1 (containing zirconium oxide nanoparticles) showed obvious submicron-sized foreign particle adhesion on their surface. Figure 9 a) A significant zirconium (Zr) element peak appeared in the EDS spectrum ( Figure 9 (b) This directly confirms the mechanical embedding and residue of high-hardness nanoparticles on the silicon wafer surface. Such contaminants are difficult to completely remove during subsequent cleaning, seriously affecting the surface quality of the silicon wafer.

[0111] (2) Analysis of surface metal contaminants and harmful elements in cleaning residue:

[0112] The results of ICP-MS and IC analysis (Table 3) show that:

[0113] Embodiments of the present invention (S-1 to S-3): The content of key metallic contaminants (Na, Fe, Cr, etc.) on the surface of the diced silicon wafer is extremely low. Harmful elements sensitive to semiconductor processes, such as B, P, S, and Cl, in the cleaning residue are all below the method detection limit, indicating that the formulation system of the present invention is pure and has not introduced related ionic contamination.

[0114] Comparative Example C-1 (with added zirconium oxide): Surface metal contamination was significantly increased (e.g., Fe reached 25.6 ng / cm²), and exogenous elements Zr and Al were detected, confirming that hard particles exacerbated equipment wear and remained in the sample. The Cl content in the cleaning residue was abnormally high (24.6 ppb), significantly different from other samples, indicating that a chlorine contaminant was introduced into its formulation or raw materials.

[0115] Comparative Example C-2 (without pyridinecarboxylic acid): The surface Fe content (2.1 ng / cm²) was slightly higher than that of the Example, indicating that pyridinecarboxylic acid, as an organic corrosion inhibitor, has an observable contribution to inhibiting equipment wear and reducing Fe contamination.

[0116] Comparative examples C-3 / C-4 (improper polyethylene glycol compounding): The surface Na and Fe contents fluctuated slightly, but no significant contamination trend was formed; the harmful elements in the cleaning residue were still below the detection limit, indicating that the polyethylene glycol compounding system mainly affected lubricity and cleaning properties, and did not directly introduce harmful elements.

[0117] Commercially available product D-1 exhibits a significantly higher level of metal contamination on its silicon wafer surface (e.g., Fe at 8.7 ng / cm²) compared to the embodiments of this invention. B (0.3 ppb), P (0.1 ppb), and Cl (0.2 ppb) were clearly detected in the cleaning residue. Although the absolute values ​​are low, this indicates that the formulation system contains or contains residues of these semiconductor-restricted elements, and its purity differs from that of the product of this invention.

[0118] Test Example 5: Storage Stability Test

[0119] The water-based cutting fluid stock solutions prepared in Example 1 (S-1) and Comparative Example 3 (C-3) were subjected to the following tests:

[0120] (1) Stability at room temperature: The sample was sealed and placed in an environment of 25 °C. Observe whether layering, precipitation or turbidity occurred within 90 days.

[0121] (2) Thermal stability: The sealed sample of the cutting fluid to be tested was placed in a constant temperature oven at 40 ℃±2 ℃ and left to stand for 14 consecutive days. After the test, the sample was taken out and allowed to cool naturally to room temperature (25 ℃±2 ℃), and left to stand for equilibration for 2 hours. The viscosity was measured using a Brookfield DV2T rotational viscometer with the LV-2 rotor (or other suitable rotor selected according to the viscosity range of the sample). The measurement temperature was kept constant at 25 ℃ and the rotation speed was set to 65 rpm. The apparent viscosity value was recorded after the reading stabilized. The rate of change of the sample viscosity before and after heat storage was calculated, and the appearance (color, transparency, uniformity) was visually inspected at the same time. The test results are shown in Table 4.

[0122] Checklist 4: Storage Stability Test Results

[0123] Results analysis:

[0124] As shown in Table 4, the sample of Example 1 (S-1) of this invention remained uniform and transparent after long-term static storage and heat storage, with minimal viscosity change, exhibiting excellent physical and chemical stability. In contrast, Comparative Example 3 (C-3) showed slight stratification after static storage at room temperature, and its viscosity decreased significantly after heat storage. This result directly proves that the introduction of PEG-3350 plays a crucial role in maintaining the uniformity and stability of the system. The improved system stability is the fundamental reason why it can effectively suspend the abrasive, prevent sedimentation, and thus achieve the better cutting surface quality (smaller chipping and lower roughness) shown in Test Example 3.

[0125] The above embodiments fully demonstrate the excellent performance of the water-based cutting fluid of the present invention in silicon wafer multi-wire cutting applications, especially the synergistic improvement in lubrication, rust prevention, cleanliness and environmental friendliness, effectively solving the technical problems existing in the prior art.

[0126] Those skilled in the art should note that the embodiments described in this invention are merely exemplary, and various other substitutions, changes, and improvements can be made within the scope of this invention. Therefore, this invention is not limited to the above embodiments, but is defined only by the claims.

Claims

1. A high-purity water-based cutting fluid for multi-wire cutting of silicon wafers, characterized in that, It consists of the following components in parts by weight: 70.0–85.0 parts of ultrapure water; Polyethylene glycol-400: 10.0–20.0 parts; Polyethylene glycol-3350: 3.0–5.0 parts; 1.0–1.8 parts of methylethanolamine; Lauroyl amino acid ester 0.5-1.0 parts; 0.8–1.5 parts of isomeric tridecyl alcohol polyoxyethylene ether; Pyridinecarboxylic acid 0.05–0.1 parts; 0.05–0.15 parts of polyether-modified siloxane defoamer; The water-based cutting fluid is a homogeneous, transparent liquid that does not contain solid lubricating particles.

2. The high-purity water-based cutting fluid for multi-wire silicon wafer cutting according to claim 1, characterized in that, The weight ratio of polyethylene glycol-400 to polyethylene glycol-3350 is 2:1 to 6.67:

1.

3. The high-purity water-based cutting fluid for multi-wire silicon wafer cutting according to claim 1 or 2, characterized in that, The weight ratio of polyethylene glycol-400 to polyethylene glycol-3350 is 4:1 to 5:

1.

4. The high-purity water-based cutting fluid for multi-wire silicon wafer cutting according to claim 1, characterized in that, The ethylene oxide addition number of the isomeric tridecyl alcohol polyoxyethylene ether is 8-10.

5. The high-purity water-based cutting fluid for multi-wire silicon wafer cutting according to claim 1, characterized in that, The pH value of the water-based cutting fluid is 8.2-8.

8.

6. The high-purity water-based cutting fluid for multi-wire silicon wafer cutting according to claim 1, characterized in that, The resistivity of the ultrapure water is ≥18.2 MΩ·cm.

7. A method for preparing a high-purity water-based cutting fluid for multi-wire cutting of silicon wafers as described in any one of claims 1-6, characterized in that, Includes the following steps: (1) Add methylethanolamine, lauroyl amino acid ester and pyridine carboxylic acid to ultrapure water and stir until completely dissolved to obtain the basic aqueous phase; (2) Add polyethylene glycol-400 and polyethylene glycol-3350 to the basic aqueous phase, heat to 48-52°C and stir until polyethylene glycol-3350 is completely dissolved and the system is homogeneous; (3) Cool the system to room temperature, add isomeric tridecyl alcohol polyoxyethylene ether and polyether modified siloxane defoamer, and stir evenly; (4) Add ultrapure water to the total volume, adjust the pH value to 8.2-8.8, stir evenly, and then filter through the terminal to obtain the high-purity water-based cutting fluid.

8. The preparation method according to claim 7, characterized in that, The terminal filter uses a filter element with a pore size ≤ 0.2 μm.

9. The application of the high-purity water-based cutting fluid for multi-wire cutting of silicon wafers according to any one of claims 1-6 in the multi-wire cutting process of semiconductor silicon wafers.

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