Mortar cutting fluid for 12-inch semiconductor wafer as well as preparation method and application of mortar cutting fluid

Abstract

The invention relates to mortar cutting fluid for a 12-inch semiconductor wafer as well as a preparation method and application of the mortar cutting fluid. The mortar cutting fluid comprises the following components in parts by weight: 10-30 parts of polyethylene glycol; 30 to 60 parts of deionized water; 1-5 parts of a dispersant; 1-10 parts of a protective agent; and 5-20 parts of a cooling agent. The dispersing agent can ensure that the grinding material is uniformly distributed in a system, can be used as a protective colloid to wrap the grinding material and form a layer of lubricating film on the outer surface of the grinding material, so that the mortar system is more stable, and the fluidity of the mortar in the stirring process is also improved. Silicate and sulfate are adopted as the protective agent, so that the protective effect on the steel wire can be greatly improved, the wire breakage rate is effectively reduced, and the cutting cost is reduced. The cutting fluid provided by the invention has the advantages of good abrasive dispersibility, stable cooling performance and low line breaking rate.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor manufacturing technology, and in particular relates to a mortar cutting fluid for 12-inch semiconductor wafers, a preparation method and use thereof. Background Art

[0002] As integrated circuits develop rapidly, the research on cutting technology has received more and more attention. As the feature size of integrated circuits continues to shrink, the chip cutting process has become an indispensable key step in the integrated circuit manufacturing process. As one of the process chemicals required for the key process of integrated circuit manufacturing, cutting functional chemicals are the most critical functional chemical materials involved in cutting technology and are widely used in the manufacture of integrated circuits and the micro-machining of discrete semiconductor devices.

[0003] At present, the global large-size hard and brittle material cutting functional chemical manufacturers are mainly concentrated in Europe, the United States, Japan, South Korea and other places, among which Europe and the United States occupy more than 30% of the global market share; Japan occupies about 26% of the global share. More than 90% of China's chip cutting materials are imported from abroad.

[0004] With the rapid development of the semiconductor industry, the requirements for various technologies and materials in the semiconductor manufacturing process are also constantly increasing. Among them, semiconductor mortar cutting fluid is a key auxiliary material in the semiconductor material cutting process, and its performance is directly related to the cutting quality, efficiency and cost.

[0005] Currently, the global silicon wafer market is developing towards large-size silicon wafers. The most mainstream products are 8-inch silicon wafers and 12-inch silicon wafers, with 12-inch wafers accounting for a higher proportion. At the same time, higher requirements are also placed on the cutting performance of mortar cutting fluids.

[0006] At present, the cutting fluid for 12-inch silicon wafers still has problems such as poor abrasive dispersion, unstable cooling performance, and high wire breakage rate. Therefore, it is necessary to develop an efficient and environmentally friendly cutting fluid that can simultaneously ensure dispersion and cooling performance and reduce the wire breakage rate. The cutting fluid can be applied to mortar cutting fluid for 12-inch large-size silicon wafers. Summary of the invention

[0007] The technical problem solved by the present invention is that the current 12-inch silicon wafer cutting fluid has poor abrasive dispersion, unstable cooling performance and high wire breakage rate.

[0008] In view of the technical problems existing in the prior art, the present invention designs a mortar cutting fluid for 12-inch semiconductor wafers, a preparation method and use thereof.

[0009] It should be noted that, in the present invention, unless otherwise specified, the specific meaning of "including" in relation to composition limitations and descriptions includes both open-ended "including", "comprising" and similar meanings, and closed-ended "consisting of..." and similar meanings.

[0010] In order to solve the above-mentioned technical problems, the present invention adopts the following solutions:

[0011] A mortar cutting fluid for 12-inch semiconductor wafers, characterized in that it comprises the following components calculated by weight:

[0012] 10-30 parts of polyethylene glycol;

[0013] 30-60 parts of deionized water;

[0014] Dispersant 1-5 parts;

[0015] 1-10 parts of protective agent;

[0016] 5-20 parts of coolant.

[0017] Furthermore, the dispersant is at least one of methyl cellulose, hydroxyethyl methyl cellulose, carboxymethyl cellulose, ethyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose.

[0018] Furthermore, the dispersant is methylcellulose and / or hydroxypropyl methylcellulose.

[0019] Furthermore, when the dispersant is a mixture of methylcellulose and hydroxypropyl methylcellulose, the mass ratio of the methylcellulose to the hydroxypropyl methylcellulose is 1:1-3:1.

[0020] Furthermore, the protective agent is a mixture of silicate and sulfate;

[0021] The mass ratio of the silicate to the sulfate is 4:1-9:1.

[0022] Furthermore, the silicate is at least one of sodium silicate and potassium silicate;

[0023] The sulfate is at least one of zinc sulfate, sodium sulfate and potassium sulfate.

[0024] Furthermore, the coolant is one or two of ethylene glycol, propylene glycol, and diethylene glycol.

[0025] Furthermore, the mass ratio of the protective agent to the dispersant is 1:1-5:1.

[0026] The present invention also discloses a method for preparing a mortar cutting fluid for a 12-inch semiconductor wafer, which is characterized by comprising the following steps:

[0027] Step 1: At room temperature, take 4 / 5 deionized water, add polyethylene glycol, dispersant, protective agent and coolant in sequence under stirring, continue stirring for a certain period of time, then add the remaining 1 / 5 deionized water, continue stirring at 20-45°C until it is completely dissolved;

[0028] Step 2: Stop stirring, let stand for 4-8 hours, and filter to obtain the mortar cutting fluid for 12-inch semiconductor wafers.

[0029] The invention also discloses a use of a mortar cutting fluid for 12-inch semiconductor wafers in cutting large-size semiconductor silicon wafers.

[0030] In the present invention, in order to further optimize the performance of the mortar cutting fluid, its components can be optimized: 10-20 parts of polyethylene glycol; 50-60 parts of deionized water; 1-2 parts of dispersant; 1-5 parts of protective agent; 10-15 parts of coolant.

[0031] In the present invention, when the dispersant is a mixture of methylcellulose and hydroxypropylmethylcellulose, the mass ratio of methylcellulose to hydroxypropylmethylcellulose may further preferably be 1:1.

[0032] In the protective agent of the present invention, the sulfate may further preferably be zinc sulfate. In the protective agent, the mass ratio of silicate to sulfate is preferably 6:1-9:1. In the protective agent, the mass ratio of silicate to sulfate is most preferably 9:1.

[0033] In the present invention, the mass ratio of the protective agent to the dispersant is preferably 2:1-5:1; the mass ratio of the protective agent to the dispersant may further preferably be 2.5:1.

[0034] In the preparation of the mortar cutting fluid of the present invention, silicon carbide is not added when the stock fluid is filtered, and the abrasive is usually added to the cutting fluid and stirred evenly before on-site cutting.

[0035] The inventors have found that the dispersant in the present invention is a cellulose ether-based substance. After being dissolved in water, the surface activity thereof ensures that the abrasive is effectively and evenly distributed in the system. The cellulose ether, as a protective colloid, can wrap the abrasive and form a lubricating film on its outer surface, thereby making the mortar system more stable and improving the fluidity of the mortar during the stirring process.

[0036] In addition, cellulose ethers also have a certain thickening effect, which can prevent the abrasive from becoming a "hard cake" after precipitation and improve the redispersibility of the abrasive.

[0037] The inventors have found that sodium silicate / potassium silicate can form a protective film on the surface of the steel wire, but this protective film is porous. Therefore, the corrosion inhibition performance of silicate alone is poor and needs to be used in combination with zinc sulfate. Zinc sulfate and silicate can significantly improve the protective effect on the steel wire and fill the pores of the protective film formed by silicate on the steel wire.

[0038] The inventors have found that the coolant of the present invention can effectively reduce the temperature of the contact area between the steel wire and the silicon wafer during the cutting process, take away most of the heat generated by friction, and prevent the problem of uneven cutting surface caused by uneven heating of the silicon wafer.

[0039] The present invention provides a mortar cutting fluid for 12-inch semiconductor wafers, and its preparation method and use have the following beneficial effects:

[0040] 1. The dispersant in the present invention can not only ensure the uniform distribution of the abrasive in the system, but also as a protective colloid, it can wrap the abrasive and form a lubricating film on its outer surface, making the mortar system more stable and improving the fluidity of the mortar during the mixing process. In addition, such substances also have a certain thickening effect, which can prevent the abrasive from "hardening" after precipitation and improve the redispersibility of the system.

[0041] 2. The protective agent of the present invention uses silicate and sulfate, which can greatly improve the protective effect on the steel wire, form a dense protective film on the surface of the steel wire, effectively reduce the wire breakage rate, and reduce the cutting cost.

[0042] 3. In the protective agent of the present invention, the silicate material exists in the form of sol after being dissolved in water, and together with the dispersant, improves the dispersibility of the abrasive, helps the abrasive particles to be evenly dispersed in the cutting fluid, and improves the cutting effect.

[0043] 4. The cutting fluid of the present invention has excellent comprehensive performance, good abrasive dispersibility, stable cooling performance, and low wire breakage rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 : The corrosion condition of the steel wire surface after cutting with the cutting fluid of Comparative Example 1 of the present invention;

[0045] Figure 2 : This is the corrosion condition of the steel wire surface after cutting with the cutting fluid of Example 1 of the present invention. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with specific embodiments and accompanying drawings:

[0047] Table 1 Example 1-Example 6

[0048]

[0049] Table 2 Comparative Examples 1-3

[0050]

[0051] About the preparation method of the cutting fluid of the present invention:

[0052] The present invention relates to methods for preparing cutting fluids in multiple groups of embodiments and comparative examples, all of which are prepared by referring to the following method:

[0053] Step 1: At room temperature, take 4 / 5 deionized water, add polyethylene glycol, dispersant, protective agent and coolant in sequence under stirring, continue stirring for a certain period of time, then add the remaining 1 / 5 deionized water, continue stirring at 25°C until it is completely dissolved;

[0054] Step 2: Stop stirring, let stand for 6 hours, and filter to obtain the mortar cutting fluid for 12-inch semiconductor wafers.

[0055] In the preparation of the mortar cutting fluid of the present invention, silicon carbide is not added when the stock fluid is filtered, and the abrasive is usually added to the cutting fluid and stirred evenly before on-site cutting.

[0056] About performance testing and description:

[0057] Performance 1 Test on TTV

[0058] TTV refers to the difference between the maximum and minimum thickness of a silicon wafer. This parameter is an important indicator used to measure the uniformity of silicon wafer thickness. In the semiconductor manufacturing process, the thickness of the silicon wafer must be very uniform across the entire surface.

[0059] Typically, measurements are taken at five locations on the wafer and the maximum difference is calculated. The proportion of wafers with a maximum difference exceeding 4 microns to the total number of wafers is then calculated.

[0060] Randomly select 5 points on the same piece to measure the thickness d. The d of the 5 points max -d min = the maximum difference of the film; d max -d min Number of silicon wafers with a thickness of >4μm / total number of silicon wafers = TTV

[0061] Performance 2 disconnection rate test

[0062] The wire breakage rate refers to the ratio of the number of wire breaks during cutting on the same day to the total number of wire breaks during the day.

[0063] The calculation formula is: Number of broken knives / total number of knives = broken rate

[0064] Performance 3 Abrasive Recovery Test

[0065] The abrasive recovery rate refers to the ratio of the amount of abrasive that can be stirred and then used in the cutting pool to the total amount. The initial amount of abrasive added is m1, and the amount of abrasive that settles at the bottom and cannot be stirred after one cutting is m2. The amount of recoverable abrasive is m3 = m1-m2, and the recovery rate is m3 / m1.

[0066] Under the same cutting parameter conditions, 12-inch silicon wafers were cut and 1000 mesh silicon carbide powder was added in a 1:1 ratio to mix. The performance of the mortar cutting fluid prepared in the embodiment of the present invention was compared with that of the comparative example. The specific results are shown in Table 3 below.

[0067] Table 3 Performance test

[0068] Example / Comparative Example Disconnection rate TTV Abrasive recovery rate Example 1 0.88％ 1.06％ 98.39％ Example 2 1.88％ 1.61％ 97.58％ Example 3 1.12％ 1.53％ 97.40％ Example 4 1.04％ 1.17％ 96.91％ Example 5 1.52％ 1.19％ 96.83％ Example 6 1.58％ 1.13％ 96.19％ Comparative Example 1 20.27％ 1.23％ 93.25％ Comparative Example 2 25.35％ 1.25％ 93.35％ Comparative Example 3 0.97％ 9.78％ 87.59％

[0069] Analysis of the test results:

[0070] In Comparative Example 1, sodium silicate in the protective agent is missing, so the cutting fluid causes certain corrosion to the steel wire. At the same time, the friction during the cutting process also causes wear to the steel wire, so the wire breakage rate increases sharply.

[0071] In Comparative Example 2, zinc sulfate in the protective agent is missing, so the cutting fluid causes certain corrosion to the steel wire. At the same time, the friction during the cutting process also causes wear to the steel wire, so the wire breakage rate increases sharply.

[0072] In Comparative Example 3, ethylene glycol is missing from the coolant, which results in heat generated by friction between the steel wire and the silicon wafer during the cutting process, and uneven temperatures at the contact point and other locations, so that TTV increases sharply.

[0073] If the abrasive forms a hard cake after precipitation, it cannot be dispersed and used again by stirring, so the precipitated abrasive needs to be discharged and new abrasive needs to be added.

[0074] The higher the abrasive recovery rate, the better the dispersibility of the cutting fluid, the less the amount of additional abrasive required, and the lower the cost. The abrasive recovery rates in the embodiments of the present invention are all relatively high, indicating good dispersibility.

[0075] Further comparison is made through the attached drawings in the specification:

[0076] Figure 1 The surface corrosion of the steel wire after cutting with the cutting fluid of Comparative Example 1 of the present invention;

[0077] Figure 2 This is the corrosion condition of the steel wire surface after being cut by the cutting fluid of Example 1 of the present invention.

[0078] from Figure 1 and Figure 2It can be seen from the comparison that after cutting with the cutting fluid of comparative example 1 of the present invention, the surface of the steel wire is severely corroded, while after cutting with the cutting fluid of example 1 of the present invention, the surface of the steel wire is basically smooth and no corrosion occurs.

[0079] The dispersant in the present invention can not only ensure that the abrasive is evenly distributed in the system, but also as a protective colloid, it can wrap the abrasive and form a lubricating film on its outer surface, making the mortar system more stable and improving the fluidity of the mortar during the stirring process. The protective agent in the present invention adopts silicates and sulfates, which can greatly improve the protective effect on the steel wire, form a dense protective film on the surface of the steel wire, effectively reduce the wire breakage rate, and reduce the cutting cost. Silicate substances exist in the form of sol after being dissolved in water, and together with the dispersant, improve the dispersibility of the abrasive, help the abrasive particles to be evenly dispersed in the cutting fluid, and improve the cutting effect. In short, the cutting fluid of the present invention has excellent comprehensive performance, good abrasive dispersibility, stable cooling performance, and low wire breakage rate.

[0080] The present invention is described exemplarily above in conjunction with the embodiments and drawings. It is obvious that the implementation of the present invention is not limited to the above-mentioned methods. As long as various improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A mortar cutting fluid for 12-inch semiconductor wafers, characterized in that: Calculated by weight, it includes the following components: The protective agent is a mixture of silicate and sulfate.

2. The mortar cutting fluid for 12-inch semiconductor wafers according to claim 1, characterized in that: The dispersant is at least one of methyl cellulose, hydroxyethyl methyl cellulose, carboxymethyl cellulose, ethyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose.

3. The mortar cutting fluid for 12-inch semiconductor wafers according to claim 2, characterized in that: The dispersant is methylcellulose and / or hydroxypropyl methylcellulose.

4. The mortar cutting fluid for 12-inch semiconductor wafers according to claim 3, characterized in that: When the dispersant is a mixture of methylcellulose and hydroxypropyl methylcellulose, the mass ratio of the methylcellulose to the hydroxypropyl methylcellulose is 1:1-3:

1.

5. The mortar cutting fluid for 12-inch semiconductor wafers according to claim 1, characterized in that: The mass ratio of the silicate to the sulfate is 4:1-9:

1.

6. The slurry cutting fluid for 12-inch semiconductor wafers according to claim 5, characterized in that: The silicate is at least one of sodium silicate and potassium silicate; The sulfate is at least one of zinc sulfate, sodium sulfate and potassium sulfate.

7. The mortar cutting fluid for 12-inch semiconductor wafers according to claim 1, characterized in that: The coolant is one or two of ethylene glycol, propylene glycol and diethylene glycol.

8. The mortar cutting fluid for 12-inch semiconductor wafers according to claim 1, characterized in that: The mass ratio of the protective agent to the dispersant is 1:1-5:

1.

9. A method for preparing a mortar cutting fluid for 12-inch semiconductor wafers according to any one of claims 1 to 8, characterized in that The following steps are involved: Step 1: At room temperature, take 4 / 5 deionized water, add polyethylene glycol, dispersant, protective agent and coolant in sequence under stirring, continue stirring for a certain period of time, then add the remaining 1 / 5 deionized water, continue stirring at 20-45°C until it is completely dissolved; Step 2: Stop stirring, let stand for 4-8 hours, and filter to obtain the mortar cutting fluid for 12-inch semiconductor wafers.

10. Use of the slurry cutting fluid for 12-inch semiconductor wafers according to any one of claims 1 to 8 in cutting large-size semiconductor silicon wafers.

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