Acrylate polymer for silicon wafer chemical mechanical fine polishing liquid and preparation method and application thereof

Abstract

The invention 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 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, and 3-5 parts of a silane coupling agent. 3-8 parts of an ammonia carboxylic acid complexing agent and 45-50 parts of deionized water. According to the invention, the acrylate polymer with proper hardness, moderate molecular weight and certain adhesive force to the silicon wafer is prepared, is added into the fine polishing liquid and is adsorbed on the surface of the wafer to form a protective film, so that the surface defects and roughness of the wafer are reduced, and a certain removal rate is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of polishing liquid, and specifically relates to an acrylate polymer used for chemical mechanical polishing liquid for silicon wafers, and a preparation method and application thereof. Background Art

[0002] Semiconductor technology has developed rapidly in the past few decades. With the development of Moore's Law, the line width in the chip has been continuously reduced from a few microns to a few nanometers. In order to improve production efficiency and reduce production costs, the size of silicon wafers has become larger and larger. This places higher and higher requirements on the surface flatness of silicon wafers. Chemical mechanical polishing is a key process to achieve silicon wafer flatness. Fine polishing is the last step in silicon wafer polishing, which will affect the final surface quality of the silicon wafer. After fine polishing, the surface of the silicon wafer is required to have no polishing marks, no polishing fog, and low roughness. This puts higher requirements on the fine polishing liquid.

[0003] CN113881347A discloses a chemical mechanical polishing liquid for silicon wafers, which uses silicon dioxide abrasive particles of different shapes and particle sizes. The large polyspherical particles increase the friction area during the polishing process and improve the polishing rate of the silicon wafer. The small particles play a lubricating role during the polishing process and reduce the scratches on the silicon wafer. However, the surface of the silicon wafer is not protected during the polishing process, and the scratch and roughness protection effect is limited.

[0004] CN117567941A, CN112175524A and CN114940866A all disclose a fine polishing liquid for improving polishing marks on the surface of silicon wafers, which improves the polishing effect by adding high molecular polymers such as polyvinyl alcohol, hydroxyethyl cellulose and hydroxy starch. However, the molecular weight range of the high molecular polymers used in these solutions is too small to obtain good surface quality and affects the polishing rate. Summary of the invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide an acrylate polymer with moderate molecular weight and hardness, good adsorption effect on the surface of silicon wafer and guaranteed polishing rate. The acrylate polymer is used in the fine polishing liquid to protect the silicon wafer by adsorbing on the surface of the silicon wafer, inhibit the polishing rate of the abrasive and reduce surface defects.

[0006] Another object of the present invention is to provide a method for preparing the acrylic ester polymer and its application in fine polishing liquid.

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

[0008] An acrylate polymer for chemical mechanical polishing liquid for silicon wafers comprises the following components in parts by mass: 0.3-3 parts of an emulsifier, 45-50 parts of a monomer, 5-10 parts of a functional monomer, 0.3-3 parts of an initiator, 0.5-3 parts of a chain transfer agent, 3-5 parts of a silane coupling agent, 3-8 parts of an aminocarboxylic complexing agent, and 45-50 parts of 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, 3.0 parts, etc.

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

[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 proportion of the functional monomer is, for example, 5, 6, 7, 8, 9, 10 parts, etc.

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

[0013] In some specific embodiments, the chain transfer agent is selected from any one of mercaptoethanol and dodecyl mercaptan, preferably mercaptoethanol; the weight proportion of the chain transfer agent is, 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 any one of nitrilotriacetic acid and ethylenediaminetetraacetic acid, preferably ethylenediaminetetraacetic acid; the weight proportion of the aminocarboxylic acid complexing agent is, 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 proportion of the silane coupling agent is, for example, 3, 3.5, 4, 4.5, 5, and the like.

[0016] In some specific embodiments, the weight parts of the deionized water are, for example, 45, 46, 47, 48, 49, 50 parts, etc.

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

[0018] a. Preparing a pre-emulsified liquid: adding a deionized water emulsifier, an initiator, a monomer, a functional monomer, a silane coupling agent, a chain transfer agent and an initiator into a pre-emulsification kettle for pre-emulsification to obtain a pre-emulsified liquid;

[0019] b. Prepare seed emulsion: add deionized water, emulsifier and part of pre-emulsion into a reaction kettle, heat up to carry out polymerization reaction, and prepare seed emulsion;

[0020] c. Add the remaining pre-emulsified liquid dropwise to the seed liquid prepared in step b. After the addition is completed, keep the temperature high. Add an aminocarboxylic acid complexing agent (e.g., ethylenediaminetetraacetic acid) dropwise into the reaction kettle. Then cool the kettle, adjust the pH to 7-9, and filter the material to obtain the acrylate polymer.

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

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

[0023] b. Preparation of seed emulsion: Add 25-30 parts of water, 0.1-2.8 parts of emulsifier, and 5% pre-emulsion into a reaction kettle, heat to 78-85°C for polymerization, and react for 10-20 minutes to obtain seed emulsion;

[0024] c. Add the remaining pre-emulsified liquid prepared in step a to the seed liquid prepared in step b, the adding time is 3-4 hours, the reaction temperature is 75-85°C, and after the adding is completed, keep warm for 1-2 hours, add 3-8 parts of ethylenediaminetetraacetic acid to the reaction kettle, the adding time is 0.5-1 hour, then cool to 40-50°C, add ammonia water to adjust the pH to 7-9, filter the material, and obtain the acrylic ester polymer.

[0025] In another aspect, the aforementioned acrylate polymer or the acrylate polymer prepared by the aforementioned preparation method is used in chemical mechanical polishing liquid for silicon wafers.

[0026] In a specific embodiment, in the application, the chemical mechanical polishing liquid includes the following components: 10-20 parts of silica sol, 0.5-1.5 parts of acrylate polymer, 0.1-0.3 parts of surfactant, 0.1-0.3 parts of pH adjuster, and 50-60 parts of water.

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

[0028] 1) The acrylate polymer of the present invention is added with a silane coupling agent so that the acrylate polymer has good adhesion to the surface of a silicon wafer; and an acrylate polymer with a moderate molecular weight and hardness is obtained by selecting a suitable monomer and a chain transfer agent.

[0029] 2) The acrylate polymer of the present invention is added to the chemical mechanical polishing liquid. During the polishing process, the acrylate polymer can be effectively adsorbed on the surface of the silicon wafer to protect the silicon wafer, avoid excessive contact between the abrasive particles in the polishing liquid and the wafer, and reduce the number of surface defects and surface roughness of the wafer.

[0030] 3) In the acrylate polymer of the present invention, the functional monomer reacts with the aminocarboxylic acid complexing agent (ethylenediaminetetraacetic acid) to improve the dispersion effect of the chelating group, and the removal rate can be guaranteed without adding ethylenediaminetetraacetic acid to the fine polishing liquid, thereby avoiding the possibility of excessive local concentration, increased defects and roughness caused by adding ethylenediaminetetraacetic acid alone. DETAILED DESCRIPTION

[0031] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0032] The main raw material information in the embodiment 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 lauryl ether phosphate, Shanghai Zhongcheng Co., Ltd.;

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

[0037] 2-EHA: 2-ethylhexyl 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 agent, Xuanhao New Materials Co., Ltd.;

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

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

[0046] Hydroxyethyl cellulose: Ashland China;

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

[0048] Hydroxystarch: Guangdong Qiangji Pharmaceutical Co., Ltd.

[0049] [Example 1]

[0050] According to the raw material composition and dosage (parts by mass) in Table 1, an acrylate polymer that can be used for chemical mechanical polishing liquid for silicon wafers is prepared according to the following steps:

[0051] a. Prepare pre-emulsion: add 25 parts of deionized water, 1 part of NP-10, 1 part of APS, 20 parts of EHA, 15 parts of BA, 12 parts of EA, 7 parts of HEA, 2 parts of ME and 4 parts of KH550 into a pre-emulsification kettle and pre-emulsify for 30 minutes to obtain 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 a reaction kettle, and the temperature was raised to 80° C. for polymerization reaction, and the reaction was carried out for 20 minutes to obtain seed emulsion;

[0053] c. Add the remaining pre-emulsified liquid prepared in step a to the seed liquid prepared in step b, the adding time is 4 hours, the reaction temperature is 82°C, and after the adding is completed, keep warm for 2 hours. Add 5 parts of ethylenediaminetetraacetic acid to the reaction kettle, the adding time is 11 hours, and then cool to 40°C, add ammonia water to adjust the pH to 8, filter the material, and obtain the polymer.

[0054] Table 1, emulsion formula in Examples 1-11

[0055]

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

[0057] Table 2, fine polishing liquid formula

[0058]

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

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

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

[0062] [Example 2-11]

[0063] Acrylate polymer was prepared according to the raw material composition in Table 1, and other operating conditions and methods were the same as those in Example 1. The corresponding fine polishing liquid was prepared according to the formula and method in Table 2.

[0064] [Comparative Example 1]

[0065] According to the formulation and method in Table 2, the only difference is that the acrylic acid ester polymer is not added to the formulation, and other operations remain unchanged to obtain a fine polishing liquid.

[0066] [Comparative Example 2]

[0067] According to the formula and method in Table 2, the only difference is that the acrylic acid ester polymer in the formula is replaced by hydroxyethyl cellulose, and other operations remain unchanged to prepare a fine polishing solution.

[0068] [Comparative Example 3]

[0069] According to the formulation and method in Table 2, the only difference is that the acrylate polymer in the formulation is replaced by povidone, and other operations remain unchanged to prepare a fine polishing solution.

[0070] [Comparative Example 4]

[0071] According to the formula and method in Table 2, the only difference is that the acrylic acid ester polymer in the formula is replaced by hydroxy starch, and other operations remain unchanged to obtain a fine polishing solution.

[0072] [Comparative Example 5]

[0073] According to the formula and method of Example 1, the only difference is that EDTA is not added, and other operations remain unchanged to obtain an acrylate polymer. The obtained acrylate polymer is used according to the formula and method of Table 2, except that 0.025 kg EDTA is additionally added to obtain a fine polishing liquid.

[0074] The polishing liquids of Examples 1-11 and Comparative Examples 1-5 were polished according to the following conditions, and the surface defects, roughness, and polishing rate were tested:

[0075] Polishing conditions are as follows: each polishing liquid was diluted 20 times with ultrapure water before use, the polishing machine was a Japanese Speedfam 36GPAW single-sided polishing machine, and the polishing pad was POLYPAS 275NX. Polishing pressure was 150g / cm 2 The polishing pad temperature is 27°C, the polishing head and polishing disc speed is 30 / 30rpm, the polishing time is 6min, the polishing liquid flow rate is 3L / min, and the polishing liquid dosage per unit area is 16mL / cm 2 .

[0076] Roughness test: sensorfar 3D confocal white light interferometer profiler measures the roughness within the range of 330*287μm and obtains the Sq value as the roughness measurement standard.

[0077] Defect count test: KLA Surfscan SP5, measuring the number of LPDs larger than 40nm as a measure of defect status.

[0078] Removal rate test: Sentronics Metrology SemDex M1 tests the thickness before and after polishing and calculates the removal rate.

[0079] The polishing performance test results of the fine polishing liquid are shown in the following table

[0080] Table 3. Test results of fine polishing liquid formula 1

[0081]

[0082]

[0083] Table 4. Test results of fine polishing liquid formula 2

[0084]

[0085]

[0086] Table 5. Test results of fine polishing liquid formula 3

[0087]

[0088]

[0089] As can be seen from the results in the table, by comparing Example 1 with Comparative Example 1, it can be seen that by adding an acrylate polymer, surface defects can be effectively reduced and surface roughness can be reduced. By comparing Example 1 with Comparative Examples 2-4, it can be seen that the addition of an acrylate polymer is significantly better than other polymers (such as hydroxyethyl cellulose, carboxyl starch or polyvidone) in improving wafer surface defects and roughness, and the polishing rate is significantly higher than the above-mentioned polymers. This is because compared with the above-mentioned polymers, the acrylate polymer has a silane coupling agent that can be better adsorbed on the wafer surface, and has a better protective effect on the wafer surface, and the molecular weight and hardness can be adjusted to select the optimal solution to improve the wafer polishing effect. At the same time, the polishing rate of Example 1 is much higher than that of Comparative Examples 2-4. By comparing Example 1 and Comparative Example 5, it can be seen that although the same EDTA is added, the polishing effect and rate of Example 1 are better than those of Comparative Example 5. This is because the acrylate polymer is combined with EDTA to make the EDTA more evenly dispersed on the wafer surface, thereby ensuring the removal efficiency and avoiding the phenomenon that the local concentration of EDTA is too high during the polishing process, resulting in too fast local removal rate and poor surface polishing effect caused by the addition of EDTA alone.

[0090] In summary, the present invention prepares an acrylate polymer with a silane coupling agent and a moderate molecular weight and hardness, and adds the acrylate polymer to the fine polishing liquid to reduce the number of surface defects and roughness of the wafer while ensuring a certain removal rate.

[0091] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. An acrylate polymer for chemical mechanical polishing of silicon wafers, characterized in that: The invention comprises the following components in parts by weight: 0.3-3 parts of an emulsifier, 45-50 parts of a monomer, 5-10 parts of a functional monomer, 0.3-3 parts of an initiator, 0.5-3 parts of a chain transfer agent, 3-5 parts of a silane coupling agent, 3-8 parts of an aminocarboxylic acid complexing agent, and 45-50 parts of deionized water.

2. The acrylate polymer according to claim 1, characterized in that The emulsifier is nonylphenol polyoxyethylene ether, preferably any one of NP-6, NP-10 and NP-12, more preferably NP-10.

3. The acrylate polymer according to claim 1, characterized in that The monomer is at least one of isooctyl acrylate, butyl acrylate and ethyl acrylate.

4. The acrylate polymer according to claim 1, characterized in that The functional monomer is at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate and hydroxypropyl methacrylate, preferably hydroxyethyl acrylate.

5. The acrylate polymer according to claim 1, characterized in that The chain transfer agent is selected from any one of mercaptoethanol and dodecyl mercaptan, preferably mercaptoethanol.

6. 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, preferably KH550; and / or The initiator is a persulfate, preferably ammonium persulfate; and / or The aminocarboxylic acid complexing agent is selected from any one of nitrilotriacetic acid and ethylenediaminetetraacetic acid, preferably ethylenediaminetetraacetic acid.

7. The method for preparing the acrylic acid ester polymer according to any one of claims 1 to 6, characterized in that: The following steps are involved: a. Preparing a pre-emulsified liquid: adding deionized water, an emulsifier, an initiator, a monomer, a functional monomer, a silane coupling agent, a chain transfer agent and an initiator into a pre-emulsification kettle for pre-emulsification to obtain a pre-emulsified liquid; b. Prepare seed emulsion: add deionized water, emulsifier and part of pre-emulsion into a reaction kettle, heat up to carry out polymerization reaction, and prepare seed emulsion; c. Add the remaining pre-emulsified liquid dropwise to the seed liquid prepared in step b. After the addition is completed, keep the temperature high. Add the aminocarboxylic acid complexing agent dropwise into the reaction kettle. Then cool the kettle, adjust the pH to 7-9, filter the material, and obtain the acrylate polymer.

8. The preparation method according to claim 7, characterized in that: The following steps are involved: a. Prepare pre-emulsion: add 20-30 parts of deionized water, 0.2-2 parts of emulsifier, 0.2-2 parts of initiator, 45-50 parts of monomer, 5-10 parts of functional monomer, 3-5 parts of silane coupling agent, 0.5-3 parts of chain transfer agent and 0.3-3 parts of initiator into a pre-emulsification kettle and pre-emulsify for 25-30 minutes to obtain pre-emulsion; b. Preparation of seed emulsion: Add 25-30 parts of water, 0.1-2.8 parts of emulsifier, and 5% of pre-emulsion into a reaction kettle, heat to 78-85°C for polymerization, and react for 10-20 minutes to obtain seed emulsion; c. Add the remaining pre-emulsified liquid to the seed liquid prepared in step b, the adding time is 3-4h, the reaction temperature is 75-85°C, and after the adding is completed, keep warm for 1-2h, add 3-8 parts of aminocarboxylic acid complexing agent to the reaction kettle, the adding time is 0.5-1h, then cool to 40-50°C, add ammonia water to adjust the pH to 7-9, filter the material, and obtain the acrylic ester polymer.

9. Use of the acrylate polymer according to any one of claims 1 to 6 or the acrylate polymer prepared by the preparation method according to claim 7 or 8 in a chemical mechanical polishing liquid for silicon wafers.

10. The use according to claim 9, characterized in that: The chemical mechanical polishing liquid comprises the following components in parts by weight: 10-20 parts of silica sol, 0.5-1.5 parts of acrylate polymer, 0.1-0.3 parts of surfactant, 0.1-0.3 parts of pH regulator, and 50-60 parts of water.

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