Polishing composition and polishing method

Abstract

The invention relates to the technical field of polishing, in particular to a polishing composition and a polishing method. The polishing composition comprises a water soluble cationic polymer and water; the polishing method comprises the following steps: providing a silicon surface to be polished, introducing the polishing composition between the silicon surface and a polishing surface of a polishing tool, and enabling the silicon surface and the polishing surface of the polishing tool to be in contact and relatively move. The polishing composition provided by the invention has a certain silicon removal rate under the condition that no abrasive is added, and the polished silicon surface has excellent hydrophilicity.

Description

Technical Field

[0001] This invention relates to the field of polishing technology, and in particular to a polishing composition and polishing method. Background Technology

[0002] Silicon wafer substrates are the fundamental material for silicon-based integrated circuit chips. With the advancement of chip manufacturing processes, the quality requirements for silicon wafer substrates are becoming increasingly stringent. The manufacturing process of silicon wafer substrates involves steps such as crystal pulling, dicing, polishing, and cleaning. Polishing is further divided into rough polishing and fine polishing. Rough polishing is used to quickly remove damaged layers, while fine polishing achieves atomic-level planarization and minimizes metal impurities and particle residues. Therefore, fine polishing is a crucial step in the manufacturing process of silicon wafer substrates, requiring highly sophisticated polishing slurries.

[0003] Currently, mainstream mass-produced silicon polishing solutions are formulated based on ultra-high purity silica sol and hydroxyethyl cellulose, as disclosed in CN103403123B. This combination of components possesses excellent properties, such as a certain silicon removal rate enabling atomic-level planarization of the silicon surface, and a hydrophilic surface after polishing, making residual particles easy to clean. Many optimization techniques are based on this. However, with the increasing technical requirements of chip manufacturing processes, the contradiction between the higher requirements for particle-free silicon wafer substrates and the polishing solution itself containing abrasive particles is becoming increasingly prominent. Minimizing the abrasive concentration has become the development direction for polishing solutions. Summary of the Invention

[0004] In order to minimize particle residue after fine polishing of silicon wafer substrates, the present invention provides a polishing composition and polishing method that do not contain abrasive particles, addressing the problems of the prior art.

[0005] In a first aspect, the present invention provides a polishing composition, which adopts the following technical solution:

[0006] A polishing composition comprising the following components: a water-soluble cationic polymer and water.

[0007] A further improvement to the above technical solution is that the water-soluble cationic polymer is selected from one or more of the following: polydimethyldiallylammonium chloride, dimethyldiallylammonium chloride-acrylic acid copolymer, dimethyldiallylammonium chloride-acrylamide copolymer, dimethyldiallylammonium chloride-acrylic acid-acrylamide copolymer, quaternized hydroxyethyl cellulose, dichloroethyl ether-bis(dimethylaminopropyl)urea polymer, methacryloyloxyethyltrimethylammonium chloride-acrylamide copolymer, and vinylpyrrolidone-dimethylaminopropylacrylamide-lauryl dimethylpropylmethacrylamide-ammonium chloride copolymer.

[0008] A further improvement to the above technical solution is that the water-soluble cationic polymer has a weight percentage of 0.0001%-1%.

[0009] A further improvement to the above technical solution is that the water is selected from tap water, distilled water, deionized water, or water purified by other methods.

[0010] A further improvement to the above technical solution is that the water is selected from deionized water with a resistance of 18.2 megohms.

[0011] A further improvement to the above technical solution is that the pH value of the polishing composition is 2-13.

[0012] A further improvement to the above technical solution is that the polishing composition also contains other additives, which are selected from surfactants and / or preservatives.

[0013] A further improvement to the above technical solution is that the surfactant is selected from nonionic surfactants, cationic surfactants, or amphoteric surfactants.

[0014] A further improvement to the above technical solution is that the preservative is selected from isothiazolinone preservatives or formaldehyde-releasing preservatives.

[0015] Secondly, the present invention provides a polishing method, which adopts the following technical solution: A polishing method comprising providing a silicon surface to be polished, introducing the aforementioned polishing composition between the silicon surface and the polishing surface of a polishing tool, and bringing the silicon surface into contact with and relative to the polishing surface of the polishing tool.

[0016] The beneficial effects of this invention are as follows: The polishing composition of this invention does not require the addition of abrasives, fundamentally solving the problem of particle residue after silicon polishing. The water-soluble cationic polymer of this invention not only has a suitable silicon removal rate, but also makes the silicon surface hydrophilic after polishing, making the polished silicon wafer easy to clean. Furthermore, since it eliminates the need to add expensive ultra-high purity silica sol as an abrasive, the cost of the polishing solution is significantly reduced. Detailed Implementation

[0017] As used herein, the terms “consisting of,” “including,” “comprising,” “having,” “having,” or any other variation thereof are intended to cover the meaning of non-exclusive inclusion. For example, a process, method, article, or apparatus that includes a list of features is not necessarily limited to the respective features, but may include other features not expressly listed or inherent to such a process, method, article, or apparatus.

[0018] As used herein, unless otherwise expressly stated, "or" means inclusive "or" rather than exclusive "or". For example, any of the following can satisfy condition A or B: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist). The following provides a further detailed description of this application.

[0019] This invention discloses a polishing composition and a polishing method, wherein the polishing composition comprises a water-soluble cationic polymer and water.

[0020] Water-soluble cationic polymers are polymers that are soluble or swollen in water and carry a net positive charge on their polymer chains. This invention, without abrasives, utilizes water-soluble cationic polymers to not only provide a certain silicon polishing removal rate but also to make the polished silicon surface hydrophilic. Both of these are essential conditions for fine silicon polishing, as a certain amount of silicon removal is required to achieve atomic-level planarization of the coarsely polished silicon surface after fine polishing. Furthermore, the hydrophilic properties of the polished surface facilitate the easy removal of silica and potential polishing pad debris particles generated during the polishing process.

[0021] Water-soluble cationic polymers are generally produced by polymerization of monomers containing alkene bonds, such as diallyl dimethyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, lauryl dimethylpropyl methacrylamide ammonium chloride, methacryloyloxyethyl phosphocholine, methacryloyloxyethyl dimethyl carboxymethyl ammonium, methacrylamide propyl trimethyl ammonium chloride, and 3-methyl-1-ethylimidazolium methyl sulfate; or copolymerized with other monomers containing alkene bonds, such as acrylic acid, acrylates, acrylamide, dimethylaminopropyl acrylamide, vinylpyrrolidone, and vinylcaprolactam; they can also be produced by polymerization of tertiary amine monomers containing alkene bonds, such as dimethylaminoethyl methacrylate, followed by quaternization; they can also be produced by reaction polymerization of polytertiary amine monomers, such as dimethylaminopropyl urea, with polyhalogenated compounds, such as dichloroethyl ether; and they can also be produced by quaternization modification of natural polymer compounds such as cellulose, chitosan, and guar gum.

[0022] The preferred addition amount of the above polymer is 0.0001%-1% by weight, more preferably 0.0001%-0.5% by weight, and even more preferably 0.001%-0.1% by weight. Too low an addition amount will weaken the hydrophilicity after polishing, while too high an addition amount will affect the silicon removal rate. The above addition amount refers to the amount used in polishing applications. When preparing, transporting, and storing the polishing composition, this concentration can be exceeded to form a concentrated solution. It should be diluted to the preferred concentration before use.

[0023] This invention also discovered that polymers of different molecular weights can achieve similar polishing effects. For example, polydimethyldiallyl ammonium chloride with a molecular weight of less than 100,000 Daltons and approximately 1 million Daltons can achieve similar silicon polishing removal rates and hydrophilicity. Generally, the optimal addition amount for high molecular weight compounds is lower than that for low molecular weight compounds, because as the molecular weight increases, the inhibitory effect of the compound on the silicon polishing removal rate becomes increasingly significant, requiring optimization of molecular weight and addition amount to achieve the best results.

[0024] Water: There are no special requirements for water. Tap water, distilled water, deionized water or water purified by other methods can be used depending on the application. Deionized water with a resistance of 18.2 megohms is preferred.

[0025] pH: The polishing composition of this invention can achieve a certain silicon removal rate and good hydrophilicity over a wide range, and can be used directly without pH adjustment, or the pH can be adjusted with an acid or alkali. There are no special requirements for the pH adjuster, as long as it can coexist stably with the above-mentioned water-soluble polymers. For acidic pH adjustment, examples include nitric acid, sulfuric acid, phosphoric acid, and small molecule organic acids such as formic acid, acetic acid, propionic acid, butyric acid, oxalic acid, malonic acid, succinic acid, citric acid, malic acid, and lactic acid; for alkaline pH adjustment, examples include sodium hydroxide, potassium hydroxide, ammonia, organic bases such as primary amines, secondary amines, tertiary amines, quaternary ammonium hydroxide, guanidines, and alkaline amino acids; from the perspective of metal impurity content, acids or bases without metal impurities are preferred; from the perspective of corrosion of polishing equipment and operator safety, a pH value of 2-13 is preferred, and a pH value of 3-12 is more preferred.

[0026] Other additives: Those skilled in the art can selectively add surfactants compatible with cationic polymers to further optimize the polishing effect. Suitable surfactants include nonionic surfactants such as polyethylene glycol, polypropylene glycol, polyoxyethylene-polyoxypropylene block polymers, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, polyoxyethylene dehydrated sorbitol fatty acid esters, glycerol polyethers, etc.; cationic surfactants such as alkyl quaternary ammonium salts containing quaternary ammonium groups, heterocyclic alkyl pyridines, alkyl imidazole / imidazoline salts, alkyl morpholine salts, alkyl quinoline salts, etc.; and amphoteric surfactants such as betaine-type, sulfobetaine-type, amino acid-type, imidazoline-type, amine oxide-type, etc. Preservatives such as isothiazolinones and formaldehyde releasers can also be added to increase shelf life.

[0027] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0028] The polishing machine used in the polishing experiment was a single-sided polishing machine with a large disc diameter of 380mm. The polishing pad was a non-woven fabric polishing pad with XY grooves. One 4-inch phosphorus-doped silicon wafer was polished at a time, with a pressure of 250g / cm². 2The polishing process was carried out at a rotation speed of 85 rpm, a polishing slurry flow rate of 60 ml / min, and a polishing time of 10 minutes. The amount of water removed was measured using an electronic balance with an accuracy of 0.1 mg. Hydrophilicity was measured using a method similar to that described in CN103403123B. After polishing, the polished surface of the silicon wafer was rinsed with deionized water for 15 seconds and then left to stand vertically for 30 seconds. The distance at which the water film contracted from the upper edge of the silicon wafer was then observed. A contraction distance of less than 5 mm was considered excellent, 5 mm to 10 mm was good, and greater than 10 mm was poor.

[0029] The high-viscosity polydimethyldiallyl ammonium chloride used in the experiment (CAS No. 26062-79-3, approximately 40% effective concentration, Brookfield viscosity 4# / 12rpm 18.65 Pa·s, molecular weight approximately 1×10⁻⁶) was used. 6 g / mol, hereinafter referred to as high viscosity PQ-6), dimethyl diallyl ammonium chloride-acrylamide copolymer (CAS No. 26590-05-6, approximately 10% effective concentration, Brookfield viscosity 4# / 12rpm is 19.07 Pa·s, hereinafter referred to as PQ-7), dimethyl diallyl ammonium chloride-acrylic acid-acrylamide copolymer (CAS No. 25136-75-8, approximately 10% effective concentration, Brookfield viscosity 4# / 12rpm is 20.79 Pa·s, hereinafter referred to as PQ-39), and quaternized hydroxyethyl cellulose (CAS No. 81859) -24-7, solid (hereinafter referred to as PQ-10), was purchased from Shandong Yousuo Chemical Technology Co., Ltd.; dimethyl diallyl ammonium chloride-acrylic acid copolymer (CAS No. 53694-17-0, approximately 40% effective concentration, Brookfield viscosity 4# / 12rpm is 14.84 Pa·s, hereinafter referred to as PQ-22) was purchased from Guangdong Qianjin Chemical Reagent Co., Ltd.; low viscosity polydimethyl diallyl ammonium chloride (CAS No. 26062-79-3, approximately 50% effective concentration, Brookfield viscosity 2# / 30rpm is 0.556 Pa·s, molecular weight less than 1×10 5The following polymers were purchased from Zhangjiagang Kaibaolai Environmental Protection Technology Co., Ltd.: dichloroethyl ether-bis(dimethylaminopropyl)urea polymer (CAS No. 68555-36-2, approximately 62% effective concentration, Brookfield viscosity 4# / 60rpm 1.47 Pa·s, hereinafter referred to as PQ-2); and methacryloyloxyethyltrimethylammonium chloride-acrylamide copolymer (CAS No. 35429-19-7, approximately 12wt% effective concentration, Brookfield viscosity 4# / 6rpm 72.71 g / mol). Pa·s (hereinafter referred to as PQ-32) was purchased from Guangdong Fangxin Biotechnology Co., Ltd.; vinylpyrrolidone-dimethylaminopropylacrylamide-lauryl dimethylpropylmethacrylamide ammonium chloride copolymer (CAS No. 306769-73-3, solid, hereinafter referred to as PQ-55) was purchased from Anhuyan (Hainan) Biotechnology Co., Ltd.; hydroxyethyl cellulose (CAS No. 9004-62-0, solid, molecular weight approximately 2.5×10⁻⁶) was purchased from Guangdong Fangxin Biotechnology Co., Ltd.; vinylpyrrolidone-dimethylaminopropylacrylamide-lauryl dimethylpropylmethacrylamide ammonium chloride copolymer (CAS No. 306769-73-3, solid, hereinafter referred to as PQ-55) was purchased from Anhuyan (Hainan) Biotechnology Co., Ltd.; hydroxyethyl cellulose (CAS No. 90 5 (g / mol, hereinafter referred to as HEC) was purchased from Ashland.

[0030] Example Example 1 One gram of high-viscosity PQ-6 with an effective concentration of approximately 40 wt% was added to 49 grams of deionized water and stirred until homogeneous to prepare a concentrated polishing composition solution. At this point, the natural pH was 5.75, and the high-viscosity PQ-6 concentration was approximately 0.8 wt%. Before the polishing experiment, 1450 grams of deionized water was added to achieve a 30-fold dilution, at which point the high-viscosity PQ-6 concentration was approximately 0.027 wt%, and the pH was 5.83. Polishing experiments were then conducted, and the results are summarized in Table 1.

[0031] Example 2 0.05 g of high-viscosity PQ-6 with an effective concentration of approximately 40 wt% was added to approximately 1500 g of deionized water and stirred until homogeneous. The pH was then adjusted to approximately 10 with ammonia to prepare a polishing composition. At this point, the concentration of high-viscosity PQ-6 was approximately 0.0013 wt%. Polishing experiments were then conducted, and the results are summarized in Table 1.

[0032] Example 3 30 grams of low-viscosity PQ-6 with an effective concentration of approximately 50 wt% was added to 1470 grams of deionized water and stirred until homogeneous. The pH was then adjusted to approximately 10 with ammonia to prepare a polishing composition, at which point the concentration of low-viscosity PQ-6 was approximately 1 wt%. Polishing experiments were then conducted, and the results are summarized in Table 1.

[0033] Example 4 0.05 g of PQ-7 with an effective concentration of approximately 10 wt% was added to approximately 1500 g of deionized water and stirred until homogeneous. The pH was then adjusted to approximately 10 with ammonia to prepare a polishing composition. At this point, the concentration of PQ-7 was approximately 0.00033 wt%. Polishing experiments were then conducted, and the results are summarized in Table 1.

[0034] Example 5 0.05 g of solid PQ-10 was added to approximately 1500 g of deionized water and stirred until completely dissolved. The pH was then adjusted to approximately 10 with ammonia to prepare a polishing composition. At this point, the concentration of PQ-10 was approximately 0.0033 wt%. Polishing experiments were then conducted, and the results are summarized in Table 1.

[0035] Example 6 One gram of PQ-39 with an effective concentration of approximately 10 wt% was added to 1499 grams of deionized water and stirred until homogeneous. The pH was then adjusted to approximately 10 using tetramethylammonium hydroxide solution to prepare a polishing composition. At this point, the concentration of PQ-39 was approximately 0.0067 wt%. Polishing experiments were then conducted, and the results are summarized in Table 1.

[0036] Example 7 One gram of PQ-22 with an effective concentration of approximately 40 wt% was added to 1499 grams of deionized water and stirred until homogeneous. The pH was then adjusted to approximately 10 using tetramethylammonium hydroxide solution to prepare a polishing composition. At this point, the concentration of PQ-22 was approximately 0.027 wt%. Polishing experiments were then conducted, and the results are summarized in Table 1.

[0037] Example 8 One gram of high-viscosity PQ-6 with an effective concentration of approximately 40 wt% was added to 1499 grams of deionized water and stirred until homogeneous. The pH was then adjusted to approximately 2 with nitric acid to prepare a polishing composition, at which point the PQ-6 concentration was approximately 0.027 wt%. Polishing experiments were then conducted, and the results are summarized in Table 1.

[0038] Example 9 One gram of high-viscosity PQ-6 with an effective concentration of approximately 40 wt% was added to 1499 grams of deionized water and stirred until homogeneous. The pH was then adjusted to approximately 8 with ammonia to prepare a polishing composition. At this point, the PQ-6 concentration was approximately 0.027 wt%. Polishing experiments were then conducted, and the results are summarized in Table 1.

[0039] Example 10 One gram of high-viscosity PQ-6 with an effective concentration of approximately 40 wt% was added to 1499 grams of deionized water and stirred until homogeneous. The pH was then adjusted to approximately 13 using tetramethylammonium hydroxide solution to prepare a polishing composition. At this point, the PQ-6 concentration was approximately 0.027 wt%. Polishing experiments were then conducted, and the results are summarized in Table 1.

[0040] Example 11 One gram of high-viscosity PQ-6 with an effective concentration of approximately 40 wt% was added to 1499 grams of deionized water and stirred until homogeneous. The pH was then adjusted to approximately 14 using tetramethylammonium hydroxide solution to prepare a polishing composition. At this point, the PQ-6 concentration was approximately 0.027 wt%. Polishing experiments were then conducted, and the results are summarized in Table 1.

[0041] Example 12 One gram of PQ-2 with an effective concentration of approximately 62 wt% was added to 1499 grams of deionized water and stirred until homogeneous. The pH was then adjusted to approximately 10 using tetramethylammonium hydroxide solution to prepare a polishing composition. At this point, the concentration of PQ-2 was approximately 0.041 wt%. Polishing experiments were then conducted, and the results are summarized in Table 1.

[0042] Example 13 One gram of PQ-32 with an effective concentration of approximately 12 wt% was added to 1499 grams of deionized water and stirred until homogeneous to prepare a polishing composition. At this point, the pH was approximately 8 and the PQ-32 concentration was approximately 0.008 wt%. Polishing experiments were then conducted, and the results are summarized in Table 1.

[0043] Example 14 0.05 g of solid PQ-55 was added to approximately 1500 g of deionized water and stirred until homogeneous. The pH was then adjusted to approximately 10 using tetramethylammonium hydroxide solution to prepare a polishing composition. At this point, the concentration of PQ-55 was approximately 0.0033 wt%. Polishing experiments were then conducted, and the results are summarized in Table 1.

[0044] Comparative Example Comparative Example 1 A polishing composition was prepared by adjusting the pH of 1500g of deionized water to approximately 10 with ammonia water, and then polishing experiments were conducted. The results are summarized in Table 1.

[0045] Comparative Example 2 Add 27.06 g of 1% HEC solution, 107.25 g of 0.28% ammonia solution, and 34.62 g of 20% pure silica with a primary particle size of 35 nm to 1331.47 g of deionized water. The pH is 10.37, and the conductivity is 95.6 μS / cm. Then add 4.11 g of 5% ammonium acetate solution to prepare a polishing composition. The pH is now 9.66, the conductivity is 231 μS / cm, the silica content is 0.46%, the HEC content is 0.018%, and the ammonia content is 0.02%. The conductivity increases 2.416 times after adding ammonium acetate. This example is Example 11 in CN103403123B. Polishing experiments were then conducted, and the results are summarized in Table 1.

[0046] Comparative Example 3 A polishing composition was prepared by adding 27.06 g of 1% HEC solution, 107.25 g of 0.28% ammonia solution, and 4.11 g of 5% ammonium acetate solution to 1366.09 g of deionized water. The pH at this point was 10.21. This example is Comparative Example 2, where silica abrasive has been removed. Polishing experiments were then conducted, and the results are summarized in Table 1.

[0047] Comparative Example 4 A polishing composition was prepared by adding 18.0 g of 1% HEC solution, 0.6 g of 25% tetrabutylammonium hydroxide solution, and 34.5 g of ultra-high purity silica with a solid content of 20% and a primary particle size of 35 nm to 1446.9 g of deionized water. The pH was 10.26, the silica content was 0.46%, the HEC content was 0.012%, and the tetrabutylammonium hydroxide content was 0.010%. This example is Example 1 from TW201518488A (the molecular weight of HEC is slightly different). Polishing experiments were then conducted, and the results are summarized in Table 1.

[0048] Comparative Example 5 A polishing composition was prepared by adding 18.0 g of 1% HEC solution and 0.6 g of 25% tetrabutylammonium hydroxide solution to 1481.4 g of deionized water, with a pH of 10.78. This example is Comparative Example 4, where silica abrasive has been removed. Polishing experiments were then conducted, and the results are summarized in Table 1.

[0049] Performance testing summary Table 1: Component content and test results of polishing compositions in Examples 1-14 and Comparative Examples 1-5

[0050] Combined with Examples 1-14 and Comparative Example 1, it can be seen that water-soluble cationic polymers can increase the silicon removal rate and make the polished surface hydrophilic without abrasives, and the polishing effect can be maintained over a wide range of pH and addition amounts.

[0051] Based on Examples 1-14 and Comparative Examples 2 and 4, it can be seen that water-soluble cationic polymers can achieve or exceed the hydrophilicity and silicon removal rate of the prior art without abrasives.

[0052] As can be seen from Comparative Examples 2-5, the silicon removal rate is significantly reduced in the existing technology if silica abrasive is not added.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the present invention without departing from the scope of the present invention are within the scope of the present invention.

Claims

1. A polishing composition, characterized in that, The polishing composition comprises the following components: a water-soluble cationic polymer and water.

2. The polishing composition according to claim 1, characterized in that, The water-soluble cationic polymer is selected from one or more of the following: polydimethyldiallylammonium chloride, dimethyldiallylammonium chloride-acrylic acid copolymer, dimethyldiallylammonium chloride-acrylamide copolymer, dimethyldiallylammonium chloride-acrylic acid-acrylamide copolymer, quaternized hydroxyethyl cellulose, dichloroethyl ether-bis(dimethylaminopropyl)urea polymer, methacryloyloxyethyltrimethylammonium chloride-acrylamide copolymer, and vinylpyrrolidone-dimethylaminopropylacrylamide-lauryl dimethylpropylmethacrylamide-ammonium chloride copolymer.

3. The polishing composition according to claim 1, characterized in that, The water-soluble cationic polymer has a weight percentage of 0.0001%-1%.

4. The polishing composition according to claim 1, characterized in that, The water is selected from tap water, distilled water, deionized water, or water purified by other methods.

5. The polishing composition according to claim 4, characterized in that, The water is selected from deionized water with a resistance of 18.2 megohms.

6. The polishing composition according to claim 1, characterized in that, The polishing composition has a pH value of 2-13.

7. The polishing composition according to claim 1, characterized in that, The polishing composition also contains other additives selected from surfactants and / or preservatives.

8. The polishing composition according to claim 7, characterized in that, The surfactant is selected from nonionic surfactants, cationic surfactants, or amphoteric surfactants.

9. The polishing composition according to claim 7, characterized in that, The preservative is selected from isothiazolinone preservatives or formaldehyde-releasing preservatives.

10. A polishing method, characterized in that, A silicon surface to be polished is provided, a polishing composition as described in any one of claims 1-9 is introduced between the silicon surface and the polishing surface of a polishing tool, and the silicon surface is brought into contact with and moved relative to the polishing surface of the polishing tool.

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