Recyclable suspension additive with long service life, grinding fluid containing suspension additive, and preparation method and application of suspension additive

Abstract

The invention relates to a recyclable suspension additive with long service life, a grinding fluid containing the suspension additive, and a preparation method and application of the suspension additive. The suspension additive comprises the following components in parts by weight: 1-5 parts of ionic liquid; 2 to 10 parts of a thickening agent; 5 to 15 parts of a pH regulator; 1-5 parts of an antioxidant; 2-5 parts of a suspension stabilizer; and 60-80 parts of ultrapure water. The suspension additive can be recycled, has long service life, can be applied to the field of silicon wafer grinding, can solve the problem of short service life of the suspension additive in the recycling process, can still keep excellent grinding efficiency in multiple times of recycling, and reduces the scratch and fragment rate at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of suspension agents, and in particular relates to a suspension aid with a long service life and recyclability, a grinding liquid containing the same, and a preparation method and application thereof. Background Art

[0002] With the development of semiconductor technology, chip size continues to shrink, which requires the flatness and smoothness of the silicon wafer surface to become more critical. At the same time, the market demand for miniaturized, high-performance semiconductor products continues to increase, which also puts higher requirements on the silicon wafer grinding process.

[0003] Silicon wafer grinding is one of the key process steps in semiconductor manufacturing, which is used to produce a flat and smooth silicon wafer surface for subsequent process steps such as photolithography, etching and deposition. Generally speaking, grinding is to remove knife marks or line marks on the surface of the silicon wafer by grinding the upper and lower surfaces of the silicon wafer, improve the surface flatness of the silicon wafer, and produce a uniform surface damage layer. At the same time, the thickness deviation of each batch of silicon wafers is as close as possible, creating conditions for the subsequent preparation of a damage-free silicon wafer surface.

[0004] At present, silicon wafers are mainly ground by chemical mechanical polishing, in which the suspension and the polishing liquid containing it are one of the core technologies that affect the polishing index. In order to reduce the waste of the suspension, reduce the cost, and reduce the pollution to the environment, the suspension and the polishing liquid containing it are usually recycled.

[0005] However, as the use time of current suspending agents increases, their physical and chemical properties may change, such as narrowing of particle size distribution, increase in particle size, ineffectiveness of surfactants, etc., making it difficult for them to continue to play their original dispersing and suspending roles, resulting in a decrease in suspension and dispersion performance, leading to a slow removal rate and even scratches and fragments, greatly affecting production efficiency. Therefore, it is urgent to develop a long-life, recyclable suspending aid. Summary of the invention

[0006] The technical problem solved by the present invention is that the suspension and dispersion performance of the current suspending agent will decrease during the recycling process, resulting in a slow removal rate or even scratches and fragments, which greatly affects the production efficiency.

[0007] In view of the technical problems existing in the prior art, the present invention designs a long-life, recyclable suspension aid, a grinding liquid containing the same, a preparation method and an application thereof. The suspension aid of the present invention can be recycled and has a long service life. When used in the field of silicon wafer grinding, the problem of insufficient service life of the suspension aid during recycling can be solved, and excellent grinding efficiency can still be maintained during multiple recycling uses, while reducing the scratch and fragmentation rate.

[0008] 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.

[0009] In order to solve the above-mentioned technical problems, the present invention adopts the following solutions:

[0010] [The first technical solution]

[0011] The invention provides a long-life, recyclable suspension aid, which comprises the following components in parts by weight:

[0012] 1-5 parts of ionic liquid;

[0013] Thickener 2-10 parts;

[0014] 5-15 parts of pH regulator;

[0015] 1-5 parts of antioxidants;

[0016] 2-5 parts of suspension stabilizer;

[0017] 60-80 parts of ultrapure water;

[0018] Wherein, the ionic liquid is an ionic liquid with hydroxyl groups.

[0019] Furthermore, the ionic liquid is a hydroxymethyl imidazolium salt ionic liquid;

[0020] The hydroxymethylimidazolium salt ionic liquid is one or more of 1-hydroxymethylimidazolium chloride, 1-hydroxymethylimidazolium acetate, 1-hydroxymethylimidazolium formate, 1-hydroxymethylimidazolium butyrate, and 1-hydroxymethylimidazolium sulfate.

[0021] Furthermore, the suspension stabilizer is isobutyl mercaptan, 2-aminobutane-1-thiol,

[0022] One or more of 2,3-dimethyl-2-butanethiol, 3-methyl-2-butanethiol, and 1-methylbutanethiol.

[0023] Furthermore, the thickener is one or more of methyl cellulose, hydroxyethyl cellulose, alginic acid, xanthan gum and xylan gum.

[0024] Furthermore, the pH regulator is one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, triethanolamine, and diethanolamine.

[0025] Furthermore, the antioxidant is one or more of ascorbic acid, vitamin E, tea polyphenols, and glutathione.

[0026] In the present invention, in order to improve the performance of the suspension aid, its various components can be preferably: 2-5 parts of ionic liquid; 3-6 parts of thickener; 8-12 parts of pH adjuster; 2-4 parts of antioxidant; 3-5 parts of suspension stabilizer; 65-75 parts of ultrapure water.

[0027] In the present invention, the hydroxymethylimidazolium salt-based ionic liquid is preferably 1-hydroxymethylimidazolium chloride.

[0028] In the present invention, the suspension stabilizer is preferably isobutyl mercaptan.

[0029] In the present invention, the thickener is preferably methyl cellulose.

[0030] In the present invention, the pH adjuster is preferably sodium hydroxide.

[0031] In the present invention, the antioxidant is preferably ascorbic acid.

[0032] The inventors have found that the ionic liquid of the present invention has unique advantages:

[0033] The ionic liquid is a liquid composed entirely of ions. In the suspension aid system of the present invention, it is preferably an ionic liquid with a hydroxyl group, and more preferably a hydroxymethylimidazole salt ionic liquid.

[0034] First, it has good thermal and chemical stability, which can improve the stability of the suspension in high temperature environments and protect other components in the suspension from chemical erosion;

[0035] Secondly, the hydroxyl groups it contains have the ability to form hydrogen bonds, and can form hydrogen bonds with other electrophilic groups or negative ions, thereby improving the dispersion performance of particles in ionic liquids and further improving the stability and service life of the suspension.

[0036] In the present invention, the hydroxyl group in the hydroxymethyl imidazolium salt ionic liquid has the ability to form hydrogen bonds, and can form hydrogen bonds with other electrophilic groups or negative ions, thereby improving the dispersion performance of particles in the ionic liquid. Adding the hydroxymethyl imidazolium salt ionic liquid to the suspending agent can interact with the surface of the alumina grinding sand through hydrogen bonding to form a stable dispersion system, reduce agglomeration and deposition, and extend the service life of the suspending agent.

[0037] The inventors have found that the mercaptan suspension stabilizer can synergistically enhance the hydrogen bonding effect of the ionic liquid together with the ionic liquid, further improve the dispersion performance of the particles in the ionic liquid, and further increase the stability and service life of the suspension agent.

[0038] In the present invention, the antioxidant itself can participate in and act as a reducing agent to promote the redox reaction, and the hydroxymethylimidazole salt ionic liquid works synergistically to promote its activity during the grinding process. Dispersibility can be achieved without using a dispersant, and since the dispersant is omitted, the process of the dispersant becoming ineffective due to oxidation is avoided, so that the suspending agent still maintains excellent performance during cyclic use.

[0039] [Second technical solution]

[0040] The invention provides a method for preparing the above-mentioned suspension aid with a long service life and recyclable use, comprising the following steps:

[0041] Step 1: Weigh each component in its respective amount;

[0042] Step 2: Heat ultrapure water to 40-50°C, add thickener under mechanical stirring, stir for 30-45 minutes until a stable and uniform gel is formed, and let it stand for 1-2 hours to swell;

[0043] Step 3: The gel obtained after standing and swelling in step 2 is added in sequence to all the remaining components under stirring conditions and stirred for 30-50 minutes until the mixture is uniformly mixed to obtain the suspension aid.

[0044]

Third technical solution

[0045] The invention provides a grinding liquid, comprising the above-mentioned suspension aid with long service life and recyclable use;

[0046] Also contains ultrapure water and aluminum oxide abrasive grit;

[0047] The mass ratio of the suspension aid, ultrapure water and alumina abrasive sand is: 1-1.2:40-50:10-12.

[0048]

The fourth technical solution

[0049] A method for using the above-mentioned polishing liquid is provided, comprising the following steps:

[0050] Step 1: weigh the suspension aid, ultrapure water, and alumina grinding sand according to the mass ratio and add them into a stirring container, use mechanical stirring, and stir for 40-50 minutes until the mixture is uniform to obtain a grinding liquid;

[0051] Step 2: The grinding liquid obtained in step 1 is used to grind silicon wafers using a double-sided grinder. After each grinding process, the suspension aid is recovered from the grinding wastewater by filtering and is recycled for the next grinding.

[0052]

Fifth technical solution

[0053] The invention provides a use of the above-mentioned suspension aid with long service life and recyclability in silicon wafer grinding.

[0054] The present invention provides a long-life, recyclable suspension aid, a grinding liquid containing the same, a preparation method and an application thereof, which have the following beneficial effects:

[0055] 1. The hydroxyl group in the hydroxymethylimidazolium salt ionic liquid of the present invention has the ability to form hydrogen bonds, which can form hydrogen bonds with other electrophilic groups or negative ions, thereby improving the dispersion performance of particles in the ionic liquid. Adding hydroxymethylimidazolium salt ionic liquid to the suspending agent can interact with the surface of alumina grinding sand through hydrogen bonding to form a stable dispersion system, reduce agglomeration and deposition, and extend the service life of the suspending agent.

[0056] 2. The hydroxymethylimidazole salt ionic liquid of the present invention has good thermal stability and chemical stability, can improve the stability of the suspension agent in a high temperature environment and protect other components in the suspension agent from chemical corrosion, further extending the stability and service life of the suspension agent.

[0057] 3. The antioxidant of the present invention can participate in and act as a reducing agent to promote the redox reaction. The hydroxymethylimidazole salt ionic liquid works synergistically to promote its activity during the grinding process. Dispersibility can be achieved without the use of a dispersant. Since the dispersant is omitted, the process of the dispersant becoming ineffective due to oxidation is avoided, so that the suspending agent still maintains excellent performance during cyclic use.

[0058] 4. The cations and anions in the hydroxymethylimidazole salt ionic liquid of the present invention can interact with the ions in the suspension stabilizer, thereby adjusting the charge characteristics of the surface of the aluminum oxide abrasive sand particles, reducing the electrostatic repulsion, improving the stability of the suspension, maintaining the uniform suspension of the particles in the suspension, and preventing stratification or precipitation.

[0059] 5. The suspension aid of the present invention can be recycled and still maintain excellent performance, thereby reducing the waste of the suspension agent, lowering costs, and reducing environmental pollution.

[0060] 6. The suspension aid of the present invention has a long service life. When used in the field of silicon wafer grinding, it can solve the problem of insufficient service life of the suspension aid during recycling. It can still maintain excellent grinding efficiency during multiple recycling uses while reducing the scratch and breakage rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 : The scratch picture of the silicon wafer surface after grinding twice using the grinding liquid prepared with the semiconductor silicon wafer suspension aid in Example 1;

[0062] Figure 2: This is a picture of scratches on the silicon wafer surface after grinding twice using the grinding liquid prepared with the semiconductor silicon wafer suspension aid in Comparative Example 1 and recycled. DETAILED DESCRIPTION

[0063] The present invention will be further described below in conjunction with specific embodiments and accompanying drawings:

[0064] Table 1 Example 1-Example 5

[0065]

[0066] Table 2 Comparative Examples 1-4

[0067]

[0068] Table 3 Test data

[0069]

[0070] About the preparation method of the suspension aid of the present invention:

[0071] The present invention involves a plurality of preparation methods of suspension aids, which are all operated according to the following method:

[0072] Step 1: Weigh each component in its respective amount;

[0073] Step 2: Heat ultrapure water to 45°C, add thickener under mechanical stirring, stir for 40 minutes until a stable and uniform gel is formed, and let it stand for 1 hour to swell;

[0074] Step 3: The gel obtained after standing and swelling in step 2 is added in sequence to all the remaining components under stirring conditions and stirred for 40 minutes until the mixture is uniformly mixed to obtain the suspension aid.

[0075] About the use of the grinding liquid of the present invention:

[0076] Step 1: weigh the suspension aid, ultrapure water, and alumina grinding sand according to the mass ratio and add them into a stirring container, use mechanical stirring, and stir for 50 minutes until the mixture is uniform to obtain a grinding liquid;

[0077] The mass ratio of the suspension aid, ultrapure water and alumina abrasive sand is 1:40:10.

[0078] Step 2: The grinding liquid obtained in step 1 is used to grind silicon wafers using a double-sided grinder. After each grinding process, the suspension aid is recovered from the grinding wastewater by filtering and is recycled for the next grinding.

[0079] About performance testing and description:

[0080] in:

[0081] The test method for performance 1 removal rate is:

[0082] The grinding liquid includes suspension aid, ultrapure water and alumina grinding sand.

[0083] The mass ratio of the suspension aid, ultrapure water and alumina abrasive sand is 1:40:10.

[0084] Under the same process conditions, 8-inch single crystal silicon wafers were used for grinding tests. After each grinding process, the suspending agent was recovered from the grinding wastewater by filtration and continued to be used in the next grinding cycle. The removal rate after each grinding cycle was compared;

[0085] The grinding process is as follows:

[0086] Grinding equipment: double-sided grinding machine,

[0087] Wafer size: 8 inches,

[0088] Speed: 45r / min,

[0089] Pressure: 120kPa,

[0090] Plate temperature: 25-35℃,

[0091] Flow rate: 1.2L / min,

[0092] Grinding time: 12min.

[0093] The removal rate calculation formula is:

[0094] Performance 2 The test method for silicon wafer surface scratches is:

[0095] After the silicon wafer is ground using the above-mentioned grinding process, the scratch condition of the silicon wafer surface after each grinding cycle is directly observed, and the number of cycles when scratches appear is recorded.

[0096] Performance 3 fragmentation rate test method:

[0097] The breakage rate refers to the number of broken silicon wafers that are warped, deformed, or broken after grinding on the same day, as a percentage of the total number of silicon wafers ground on that day.

[0098] The calculation formula is: number of fragments / total number of fragments*100%=fragmentation rate

[0099] Analysis of the test results:

[0100] Based on Table 3, it can be seen that the silicon wafer polishing liquid containing the suspension aid of the present invention still has a high removal rate after being recycled for 3 times. Among them, Example 1 can still maintain a low scratch rate and a fragmentation rate (less than 2%) in 5 cycles, and Examples 2-4 of the present invention have a fragmentation rate of 2% after more than 3 cycles; while the fragmentation rate of the comparative example is significantly higher than that of Examples 2-4, and the number of cycles is also reduced to a certain extent. When the fragmentation rate exceeds 2%, it does not meet the standard for recycling.

[0101] The silicon wafer grinding liquid containing the suspension aid of the present invention can improve the compatibility with other components in the suspension, enhance the stability of the suspension, maintain the uniform suspension of particles in the suspension, and prevent stratification or precipitation.

[0102] In Comparative Example 1, since no suspension aid was added, the abrasive particles precipitated, and the removal rate decreased when the abrasive particles were used for the second cycle, and slight scratching occurred when the abrasive particles were used for the second cycle, with a breakage rate of 4.3%;

[0103] In Comparative Example 2, 2-aminoimidazole sulfate was used as the ionic liquid, and its performance was lower than that of hydroxymethylimidazole salt ionic liquids. It could not interact with the surface of alumina abrasive sand through hydrogen bonding, which reduced the removal rate. When it was recycled for 3 times, slight scratching occurred, and the breakage rate reached 3.6%.

[0104] In Comparative Example 3, since no antioxidant was added, the removal rate was reduced and the fragmentation rate reached 4.5% when the sample was used for the second cycle;

[0105] In Comparative Example 4, no hydroxymethylimidazole salt ionic liquid was added, so recycling could not be achieved and the removal rate was significantly reduced.

[0106] Further comparison is made through the attached drawings in the specification:

[0107] Figure 1 The scratch condition of the silicon wafer surface after the grinding liquid prepared with the semiconductor silicon wafer suspension aid in Example 1 was recycled twice;

[0108] Figure 2 The scratch condition of the silicon wafer surface after two cycles of grinding using the grinding liquid prepared with the semiconductor silicon wafer suspension aid in Comparative Example 1.

[0109] from Figure 1 and Figure 2 It can be seen from the comparison that the surface of the silicon wafer after being ground twice by recycling the grinding liquid prepared with the semiconductor silicon wafer suspension aid in Example 1 is smooth and has no scratches.

[0110] However, the surface of the silicon wafer was seriously scratched after two cycles of grinding using the grinding liquid prepared with the semiconductor silicon wafer suspension aid in Comparative Example 1, with many and obvious scratches.

[0111] The suspension aid of the present invention has a long service life. When used in the field of silicon wafer grinding, the problem of insufficient service life of the suspension aid during recycling can be solved. The excellent grinding efficiency can be maintained during multiple recycling uses, while the scratch and fragmentation rates can be reduced. The suspension aid of the present invention can be recycled and still maintain excellent performance, thereby reducing the waste of the suspension agent, reducing costs, and reducing environmental pollution.

[0112] 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 long-life, recyclable suspension aid, characterized in that: Calculated by weight, it includes the following components: 1-5 parts of ionic liquid; Thickener 2-10 parts; 5-15 parts of pH regulator; 1-5 parts of antioxidants; 2-5 parts of suspension stabilizer; 60-80 parts of ultrapure water; Wherein, the ionic liquid is an ionic liquid with hydroxyl groups.

2. The long-life, recyclable suspension aid according to claim 1, characterized in that: The ionic liquid is a hydroxymethyl imidazolium salt ionic liquid; The hydroxymethylimidazolium salt ionic liquid is one or more of 1-hydroxymethylimidazolium chloride, 1-hydroxymethylimidazolium acetate, 1-hydroxymethylimidazolium formate, 1-hydroxymethylimidazolium butyrate, and 1-hydroxymethylimidazolium sulfate.

3. The long-life, recyclable suspension aid according to claim 1, characterized in that: The suspension stabilizer is one or more of isobutyl mercaptan, 2-aminobutane-1-thiol, 2,3-dimethyl-2-butanethiol, 3-methyl-2-butanethiol, and 1-methylbutyl mercaptan.

4. The long-life, recyclable suspension aid according to claim 1, characterized in that: The thickener is one or more of methyl cellulose, hydroxyethyl cellulose, alginic acid, xanthan gum and xylan gum.

5. The long-life, recyclable suspension aid according to claim 1, characterized in that: The pH regulator is one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, triethanolamine and diethanolamine.

6. The long-life, recyclable suspension aid according to claim 1, characterized in that: The antioxidant is one or more of ascorbic acid, vitamin E, tea polyphenols and glutathione.

7. A method for preparing a long-life, recyclable suspension aid according to any one of claims 1 to 6, characterized in that The following steps are involved: Step 1: Weigh each component in its respective amount; Step 2: Heat ultrapure water to 40-50°C, add thickener under mechanical stirring, stir for 30-45 minutes until a stable and uniform gel is formed, and let it stand for 1-2 hours to swell; Step 3: The gel obtained after standing and swelling in step 2 is added in sequence to all the remaining components under stirring conditions and stirred for 30-50 minutes until the mixture is uniformly mixed to obtain the suspension aid.

8. A grinding liquid, characterized in that: The invention comprises the long-life, recyclable suspension aid as described in any one of claims 1 to 6, and also comprises ultrapure water and alumina abrasive sand; the mass ratio of the suspension aid, ultrapure water and alumina abrasive sand is: 1-1.2:40-50:10-12.

9. A method for using the polishing liquid according to claim 8, characterized in that The following steps are involved: Step 1: weigh the suspension aid, ultrapure water, and alumina grinding sand according to the mass ratio and add them into a stirring container, use mechanical stirring, and stir for 40-50 minutes until the mixture is uniform to obtain a grinding liquid; Step 2: The grinding liquid obtained in step 1 is used to grind silicon wafers using a double-sided grinder. After each grinding process, the suspension aid is recovered from the grinding wastewater by filtering and is recycled for the next grinding.

10. Use of the long-life, recyclable suspension aid according to any one of claims 1 to 6 in silicon wafer grinding.

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