An acrylate polymer for silicon wafer chemical mechanical fine polishing liquid and its preparation method and application

Abstract

The application discloses an acrylate polymer for a silicon wafer chemical mechanical fine polishing liquid and a preparation method and application thereof, and the acrylate polymer comprises the following components in parts by mass: 0.3-3 parts of an emulsifier, 45-50 parts of a soft monomer, 5-10 parts of a functional monomer, 0.3-3 parts of an initiator ammonium persulfate, 0.5-3 parts of a chain transfer agent, 3-5 parts of a silane coupling agent, 3-8 parts of an amino-carboxyl complexing agent and 45-50 parts of deionized water. The acrylate polymer prepared by the application has appropriate hardness, moderate molecular weight and certain adhesion to a silicon wafer, is added into the fine polishing liquid, is adsorbed on a wafer surface to form a protective film, reduces wafer surface defects and roughness, and ensures a certain removal rate.

Description

Technical Field

[0001] This invention belongs to the field of polishing fluid technology, specifically relating to an acrylate polymer for chemical mechanical polishing fluid of silicon wafers, its preparation method and application. Background Technology

[0002] Semiconductor technology has developed rapidly over the past few decades. With the advancement of Moore's Law, the linewidth in chips has continuously shrunk from a few micrometers to a few nanometers. To improve production efficiency and reduce costs, the size of silicon wafers has also increased. This places increasingly higher demands on the surface flatness of silicon wafers. Chemical mechanical polishing (CMP) is a key process for achieving silicon wafer planarization. Fine polishing, the final step in silicon wafer polishing, affects the final surface quality of the wafer. After fine polishing, the silicon wafer surface must be free of polishing marks, polishing haze, and have low roughness. This places even higher demands on the fine polishing solution.

[0003] CN113881347A discloses a chemical mechanical polishing fluid for silicon wafers, which uses silicon dioxide abrasive particles of different shapes and sizes. The large, multi-ellipsoidal particles increase the friction area during polishing, improving the polishing rate of the silicon wafer, while the smaller particles act as a lubricant, reducing scratches on the silicon wafer. However, it does not protect the silicon wafer surface during polishing, resulting in limited protection against scratches and roughness issues.

[0004] CN117567941A, CN112175524A, and CN114940866A all disclose a fine polishing solution to improve polishing marks on silicon wafer surfaces. These solutions improve the polishing effect by adding polymers such as polyvinyl alcohol, hydroxyethyl cellulose, and hydroxy starch. However, the molecular weight range of the polymers used in these solutions is too small to obtain good surface quality and affects the polishing rate. Summary of the Invention

[0005] To address the problems existing in the prior art, the purpose of this invention is to provide an acrylate polymer with moderate molecular weight and softness, which has a good adsorption effect on the surface of silicon wafers and ensures the polishing rate. When used in a fine polishing solution, it adsorbs onto the surface of silicon wafers, protects the silicon wafers, inhibits the abrasive's impact on the polishing rate, and reduces surface defects.

[0006] Another object of the present invention is to provide a method for preparing such acrylate polymer and its application in polishing solutions.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] An acrylate polymer for use in a chemical mechanical polishing solution for silicon wafers comprises the following components in parts by weight: 0.3-3 parts emulsifier, 45-50 parts monomer, 5-10 parts functional monomer, 0.3-3 parts initiator, 0.5-3 parts chain transfer agent, 3-5 parts silane coupling agent, 3-8 parts aminocarboxylic acid complexing agent, and 45-50 parts deionized water.

[0009] In some specific embodiments, the emulsifier is any one of nonylphenol polyoxyethylene ether, preferably any one of NP-6, NP-10, and NP-12, and more preferably NP-10. The weight parts of the emulsifier are, for example, 0.3, 0.5, 0.8, 1.0, 1.3, 1.5, 1.7, 2.0, 2.2, 2.5, 2.8, and 3.0 parts.

[0010] In some specific embodiments, the monomer is at least one of isooctyl acrylate, butyl acrylate, and ethyl acrylate; the monomer is, for example, 45, 46, 47, 48, 49, or 50 parts by weight.

[0011] In some specific embodiments, the functional monomer is at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate, preferably hydroxyethyl acrylate; the weight parts of the functional monomer are, for example, 5, 6, 7, 8, 9, 10 parts, etc.

[0012] In some specific embodiments, the initiator is a persulfate, preferably ammonium persulfate. The initiator is expressed in parts by weight, for example, 0.3, 0.5, 0.8, 1.0, 1.3, 1.5, 1.7, 2.0, 2.2, 2.5, 2.8, or 3.0 parts.

[0013] In some specific embodiments, the chain transfer agent is selected from mercaptoethanol and dodecyl mercaptan, preferably mercaptoethanol; the weight parts of the chain transfer agent are, for example, 0.5, 0.8, 1.0, 1.3, 1.5, 1.7, 2.0, 2.2, 2.5, 2.8, 3.0 parts, etc.

[0014] In some specific embodiments, the aminocarboxylic acid complexing agent is selected from either triacetic acid or ethylenediaminetetraacetic acid, preferably ethylenediaminetetraacetic acid; the weight parts of the aminocarboxylic acid complexing agent are, for example, 3, 4, 5, 6, 7, 8 parts, etc.

[0015] In some specific embodiments, the silane coupling agent is selected from at least one of KH540, KH550, and KH560, preferably KH550; the weight parts of the silane coupling agent are, for example, 3, 3.5, 4, 4.5, or 5 parts.

[0016] In some specific implementations, the deionized water is, for example, 45, 46, 47, 48, 49, or 50 parts by weight.

[0017] On the other hand, the present invention also provides a method for preparing an acrylate polymer for a chemical mechanical polishing solution for silicon wafers, comprising the following steps:

[0018] a. Preparation of pre-emulsion: Deionized water emulsifier, initiator, monomer, functional monomer, silane coupling agent, chain transfer agent and initiator are added to the pre-emulsion kettle for pre-emulsion to obtain pre-emulsion;

[0019] b. Preparation of seed emulsion: Deionized water, emulsifier, and part of the pre-emulsion are added to the reaction vessel, and the temperature is raised to carry out the polymerization reaction to obtain the seed emulsion;

[0020] c. Add the remaining pre-emulsion to the seed solution prepared in step b. After the addition is complete, keep the solution warm. Add the aminocarboxylic acid complexing agent (e.g., ethylenediaminetetraacetic acid) to the reaction vessel, then cool down, adjust the pH to 7-9, filter and discharge the material to obtain the acrylate polymer.

[0021] In a preferred embodiment, the preparation method includes the following steps:

[0022] a. Preparation of pre-emulsion: Add 20-30 parts deionized water, 0.2-2 parts emulsifier, 0.2-2 parts initiator, 45-50 parts monomer, 5-10 parts functional monomer, 3-5 parts silane coupling agent, 0.5-3 parts chain transfer agent and 0.3-3 parts initiator to a pre-emulsion kettle and pre-emulsify for 25-30 minutes to obtain the pre-emulsion;

[0023] b. Preparation of seed emulsion: Add 25-30 parts water, 0.1-2.8 parts emulsifier, and 5% pre-emulsion to the reactor, heat to 78-85℃ to carry out polymerization reaction, and react for 10-20 minutes to obtain seed emulsion;

[0024] c. Add the remaining pre-emulsion prepared in step a dropwise to the seed solution prepared in step b, with a dropwise addition time of 3-4 hours and a reaction temperature of 75-85℃. After the dropwise addition is completed, keep the temperature for 1-2 hours. Add 3-8 parts of ethylenediaminetetraacetic acid dropwise into the reaction vessel, with a dropwise addition time of 0.5-1 hour. Then cool down to 40-50℃, add ammonia water to adjust the pH to 7-9, filter and discharge to obtain the acrylate polymer.

[0025] On the other hand, the aforementioned acrylate polymers or acrylate polymers prepared by the aforementioned methods are used in chemical mechanical polishing solutions for silicon wafers.

[0026] In one specific implementation, the chemimechanical polishing solution in the application comprises the following components: 10-20 parts silica sol, 0.5-1.5 parts acrylate polymer, 0.1-0.3 parts surfactant, 0.1-0.3 parts pH adjuster, and 50-60 parts water.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1) The acrylate polymer of the present invention has good adhesion to the silicon wafer surface by adding a silane coupling agent; by selecting appropriate monomers and chain transfer agents, an acrylate polymer with moderate molecular weight and softness / hardness is obtained.

[0029] 2) When the acrylate polymer of the present invention is added to the chemical mechanical polishing solution, the acrylate polymer can be effectively adsorbed onto the silicon wafer surface during the polishing process, protecting the silicon wafer, avoiding excessive contact between the abrasive particles in the polishing solution and the wafer, and reducing the number of surface defects and surface roughness.

[0030] 3) In the acrylate polymer of the present invention, the chelating group dispersion effect is improved by reacting the functional monomer with the aminocarboxylic acid complexing agent (ethylenediaminetetraacetic acid). The removal rate can be guaranteed without the addition of ethylenediaminetetraacetic acid to the polishing solution, avoiding the possibility that the local concentration may be too high and the defects and roughness may be increased due to the addition of ethylenediaminetetraacetic acid alone. Detailed Implementation

[0031] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0032] The main raw material information in the examples is as follows:

[0033] NP-6P: Nonylphenol polyoxyethylene hexaether phosphate, Shanghai Zhongcheng Co., Ltd.

[0034] NP-10P: Nonylphenol polyoxyethylene decaether phosphate, Shanghai Zhongcheng Co., Ltd.

[0035] NP-12P: Nonylphenol polyoxyethylene dodecyl ether phosphate, Shanghai Zhongcheng Co., Ltd.

[0036] BA: Butyl acrylate, Beijing Dongfang Chemical Plant;

[0037] 2-EHA: Isooctyl acrylate, Beijing Dongfang Chemical Plant;

[0038] EA: Ethyl acrylate, Beijing Dongfang Chemical Plant;

[0039] HEA: Hydroxyethyl acrylate, Beijing Dongfang Chemical Plant;

[0040] HEMA: Hydroxyethyl methacrylate, Beijing Dongfang Chemical Plant;

[0041] TDM: Dodecyl mercaptan, Shanghai Melk Chemical Co., Ltd.

[0042] ME: Mercaptoethanol, Shanghai Melk Chemical Co., Ltd.;

[0043] KH540, KH550, KH560: Silane coupling agents, Xuanhao New Materials Co., Ltd.;

[0044] EDTA: Ethylenediaminetetraacetic acid, Laiyang Yuandong Co., Ltd.;

[0045] Ammonia water: Zhenjiang Runjing Co., Ltd.;

[0046] Hydroxyethyl cellulose: Aslan China;

[0047] Povidone: New Open Source Medical Technology Group Co., Ltd.

[0048] Hydroxy starch: Guangdong Qiangji Pharmaceutical Co., Ltd.

[0049]

Example 1

[0050] An acrylate polymer suitable for use in chemical mechanical polishing solutions for silicon wafers was prepared according to the raw material composition and dosage (parts by mass) in Table 1 and the following steps:

[0051] a. Preparation of pre-emulsion: Add 25 parts deionized water, 1 part NP-10, 1 part APS, 20 parts EHA, 15 parts BA, 12 parts EA, 7 parts HEA, 2 parts ME, and 4 parts KH550 to a pre-emulsion kettle and pre-emulsify for 30 minutes to obtain the pre-emulsion.

[0052] b. Preparation of seed emulsion: 28 parts of deionized water, 1.5 parts of emulsion-10 and 5% pre-emulsion were added to the reactor, heated to 80°C to carry out polymerization reaction, and the seed emulsion was obtained after reacting for 20 minutes.

[0053] c. Add the remaining pre-emulsion prepared in step a dropwise to the seed liquid prepared in step b, with a dropwise addition time of 4 hours and a reaction temperature of 82°C. After the dropwise addition is completed, keep the temperature for 2 hours. Add 5 parts of ethylenediaminetetraacetic acid dropwise into the reaction vessel, with a dropwise addition time of 11 hours. Then cool down to 40°C, add ammonia water to adjust the pH to 8, filter and discharge to obtain the polymer.

[0054] Table 1. Emulsion Formulations in Examples 1-11

[0055]

[0056] The obtained polymer was used to prepare a polishing solution according to the raw material formulation and method in Table 2.

[0057] Table 2. Formulation of Polishing Solution

[0058]

[0059] According to the formula in Table 2, the preparation method of the polishing solution is as follows:

[0060] a. Take high-purity silica sol and add 50 kg of water under stirring conditions, then mix thoroughly;

[0061] b. Take the acrylate polymer, AEO-7, and ammonium hydroxide and add them to the remaining water to disperse them evenly. Then add them to the dispersion prepared in the previous step and mix them thoroughly to obtain the polishing solution for silicon wafers.

[0062]

Example 2-11

[0063] The acrylate polymer was prepared according to the raw material composition in Table 1, and other operating conditions and methods were the same as in Example 1. The corresponding polishing solution was prepared according to the formulation and method in Table 2.

[0064] Comparative Example 1

[0065] Following the formula and method in Table 2, the only difference is that acrylate polymer is not added to the formula, while other operations remain unchanged, to obtain the polishing solution.

[0066] Comparative Example 2

[0067] Following the formulation and method in Table 2, the only difference is that the acrylate polymer is replaced with hydroxyethyl cellulose in the formulation, while other operations remain unchanged, to obtain the polishing solution.

[0068] Comparative Example 3

[0069] Following the formulation and method in Table 2, the only difference is that the acrylate polymer is replaced with povidone in the formulation, while other operations remain unchanged, to obtain the polishing solution.

[0070] Comparative Example 4

[0071] Following the formula and method in Table 2, the only difference is that the acrylate polymer is replaced with hydroxy starch in the formula, while other operations remain unchanged, to obtain the polishing solution.

[0072] Comparative Example 5

[0073] Following the formulation and method of Example 1, except that EDTA was not added, all other operations remained the same, to obtain an acrylate polymer. The obtained acrylate polymer was then used according to the formulation and method in Table 2, except that 0.025 kg of EDTA was added to prepare a polishing solution.

[0074] Examples 1-11 and Comparative Examples 1-5 were polished with polishing solutions under the following conditions, and surface defects, roughness, and polishing rate were tested:

[0075] The polishing conditions are as follows: Each polishing solution was diluted 20 times with ultrapure water before use. The polishing machine was a Speedfam 36GPAW single-sided polisher from Japan, and the polishing pad was a POLYPAS 275NX. The polishing pressure was 150 g / cm². 2 The polishing pad temperature was 27℃, the polishing head and polishing disc rotation speed was 30 / 30 rpm, the polishing time was 6 min, the polishing slurry flow rate was 3 L / min, and the polishing slurry usage per unit area was 16 mL / cm². 2 .

[0076] Roughness test: The roughness within a range of 330*287μm was measured using a sensofar 3D confocal white light interferometer, and the Sq value was obtained as the roughness measurement standard.

[0077] Defect count test: KLA Surfscan SP5, which measures the number of LPDs greater than 40nm as a standard for measuring defect status.

[0078] Removal rate test: Sentronics Metrology SemDex M1 was used to test the thickness before and after polishing and to calculate the removal rate.

[0079] The polishing performance test results of the fine polishing solution are shown in the table below.

[0080] Table 3. Test results of fine polishing solution formulation 1

[0081]

[0082]

[0083] Table 4. Test Results of Fine Polishing Solution Formulation 2

[0084]

[0085]

[0086] Table 5. Test results of polishing solution formulation 3

[0087]

[0088]

[0089] The results in the table show that, comparing Example 1 with Comparative Example 1, adding acrylate polymers can effectively reduce surface defects and surface roughness. Comparing Example 1 with Comparative Examples 2-4, it is evident that adding acrylate polymers significantly improves wafer surface defects and roughness compared to other polymers (such as hydroxyethyl cellulose, carboxylated starch, or povidone), and the polishing rate is significantly higher. This is because, compared to the aforementioned polymers, acrylate polymers possess silane coupling agents that can better adsorb onto the wafer surface, providing better protection. Furthermore, the molecular weight and hardness can be adjusted to select the optimal solution for improving wafer polishing performance. Additionally, the polishing rate of Example 1 is far higher than that of Comparative Examples 2-4. By comparing Example 1 and Comparative Example 5, it can be seen that although the same ethylenediaminetetraacetic acid (EDTA) was added, the polishing effect and rate of Example 1 were better than those of Comparative Example 5. This is because by combining the acrylate polymer with EDTA, the EDTA is more evenly dispersed on the wafer surface, ensuring the removal efficiency while avoiding the phenomenon that adding EDTA alone would result in excessively high local concentrations of EDTA during the polishing process, leading to excessively fast local removal rates and poor surface polishing effects.

[0090] In summary, this invention reduces the number of defects and roughness on the wafer surface by preparing an acrylate polymer with a silane coupling agent and a suitable molecular weight and hardness, and adding it to the polishing solution, while ensuring a certain removal rate.

[0091] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. An acrylate polymer for use in a chemical mechanical polishing solution for silicon wafers, characterized in that, It includes the following components in parts by weight: 0.3-3 parts emulsifier, 45-50 parts monomer, 5-10 parts functional monomer, 0.3-3 parts initiator, 0.5-3 parts chain transfer agent, 3-5 parts silane coupling agent, 3-8 parts aminocarboxylic acid complexing agent, and 45-50 parts deionized water. The monomer is at least one of isooctyl acrylate, butyl acrylate, and ethyl acrylate; The functional monomer is at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate; The method for preparing the acrylate polymer includes the following steps: a. Preparation of pre-emulsion: Deionized water, emulsifier, monomer, functional monomer, silane coupling agent, chain transfer agent and initiator are added to a pre-emulsion kettle for pre-emulsion to obtain a pre-emulsion; b. Preparation of seed emulsion: Deionized water, emulsifier, and part of the pre-emulsion are added to the reaction vessel, and the temperature is raised to carry out the polymerization reaction to obtain the seed emulsion; c. Add the remaining pre-emulsion to the seed emulsion prepared in step b. After the addition is complete, keep the mixture warm. Add the aminocarboxylic acid complexing agent to the reaction vessel, then cool down, adjust the pH to 7-9, filter and discharge the material to obtain the acrylate polymer.

2. The acrylate polymer according to claim 1, characterized in that, The emulsifier is nonylphenol polyoxyethylene ether.

3. The acrylate polymer according to claim 2, characterized in that, The emulsifier is any one of NP-6, NP-10, and NP-12.

4. The acrylate polymer according to claim 3, characterized in that, The emulsifier is NP-10.

5. The acrylate polymer according to claim 1, characterized in that, The functional monomer is hydroxyethyl acrylate.

6. The acrylate polymer according to claim 1, characterized in that, The chain transfer agent is selected from either mercaptoethanol or dodecyl mercaptan.

7. The acrylate polymer according to claim 6, characterized in that, The chain transfer agent is selected from mercaptoethanol.

8. The acrylate polymer according to claim 1, characterized in that, The silane coupling agent is selected from at least one of KH540, KH550, and KH560; and / or The initiator is a persulfate; and / or The aminocarboxylic acid complexing agent is selected from either nitrotriacetic acid or ethylenediaminetetraacetic acid.

9. The acrylate polymer according to claim 8, characterized in that, The silane coupling agent is KH550; and / or The initiator is ammonium persulfate; and / or The aminocarboxylic acid complexing agent is ethylenediaminetetraacetic acid.

10. The acrylate polymer according to claim 1, characterized in that, The method for preparing the acrylate polymer includes the following steps: a. Preparation of pre-emulsion: Add 20-30 parts deionized water, 0.2-2 parts emulsifier, 45-50 parts monomer, 5-10 parts functional monomer, 3-5 parts silane coupling agent, 0.5-3 parts chain transfer agent and 0.3-3 parts initiator to a pre-emulsion kettle and pre-emulsify for 25-30 minutes to obtain the pre-emulsion; b. Preparation of seed emulsion: Add 25-30 parts of deionized water, 0.1-2.8 parts of emulsifier, and 5% of pre-emulsion to the reactor, heat to 78-85℃ to carry out polymerization reaction, and react for 10-20 minutes to obtain seed emulsion; c. Add the remaining pre-emulsion dropwise to the seed emulsion prepared in step b, with a dropwise addition time of 3-4 hours and a reaction temperature of 75-85℃. After the dropwise addition is completed, keep the temperature for 1-2 hours. Then, add 3-8 parts of the ammonia-carboxyl complexing agent dropwise into the reaction vessel, with a dropwise addition time of 0.5-1 hour. Then, cool down to 40-50℃, add ammonia water to adjust the pH to 7-9, filter and discharge the material to obtain the acrylate polymer.

11. The use of the acrylate polymer according to any one of claims 1-10 in a chemical mechanical polishing solution for silicon wafers.

12. The application according to claim 11, characterized in that, The chemimechanical polishing solution comprises the following components in parts by weight: 10-20 parts silica sol, 0.5-1.5 parts acrylate polymer, 0.1-0.3 parts surfactant, 0.1-0.3 parts pH adjuster, and 50-60 parts water.

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