A polishing solution for hybrid bonding and a method for regulating the same

Abstract

The application relates to the technical field of chemical mechanical polishing, and discloses a polishing liquid for hybrid bonding and a regulation method thereof, the polishing liquid is used for wafer polishing of a Cu-containing layer and a SiCN medium layer, and comprises colloidal silicon dioxide abrasive, hydrogen peroxide, amino acid, organic amine, 2-mercaptobenzimidazole, organic quaternary ammonium salt, polymer stabilizer, biocide, pH regulator and deionized water, and the pH is 7.5-9.5. By adjusting the contents of 2-mercaptobenzimidazole and organic quaternary ammonium salt, the removal process of the Cu layer and the SiCN medium layer can be proportionally regulated, and the polishing liquid is suitable for controlling the Cu recess amount and the SiCN planarization in the hybrid bonding process.

Description

Technical Field

[0001] This invention relates to the field of chemical mechanical polishing technology, and in particular to a polishing slurry for mixed bonding and its control method. Background Technology

[0002] With the development of fields such as artificial intelligence, high-performance computing, and high-bandwidth memory, integrated circuits are placing higher demands on high integration, high interconnect density, low power consumption, and low latency. Hybrid bonding technology, which combines metal-metal bonding and dielectric-dielectric bonding to achieve wafer-level or chip-level interconnects, can shorten interconnect distances and increase interconnect density, and has been gradually applied in the field of advanced packaging.

[0003] In hybrid bonding processes, the flatness and cleanliness of the bonding surfaces, as well as the relative height between the metal and dielectric layers, directly affect the bonding quality. For structures containing a Cu layer and a SiCN dielectric layer, due to the thermal expansion of Cu during subsequent annealing, it is usually necessary to maintain an appropriate depression on the Cu surface relative to the SiCN dielectric layer, and the amount of depression must be precisely controlled. If the Cu depression is too large, it can easily lead to poor Cu-Cu contact in the subsequent process; if the dielectric layer is not sufficiently planarized, it will affect the bonding quality of the bonding interface.

[0004] Chemical mechanical polishing (CMP) is an important process for obtaining mixed-bonded surface morphologies. However, existing polishing slurries often struggle to simultaneously control the Cu removal rate and planarize the SiCN dielectric layer when processing Cu / SiCN structures, particularly in adjusting the SiCN / Cu removal rate selectivity ratio based on different wafer initial morphologies. An inappropriate selectivity ratio can easily lead to excessive Cu depressions or insufficient SiCN removal, thus affecting the mixed-bonding yield.

[0005] Existing technologies include solutions for SiCN polishing or hybrid bonding polishing, such as chemical mechanical polishing compositions for SiCN layer polishing, and hybrid bonding polishing methods that control copper pillar depressions through a two-step polishing process. However, these solutions still have problems such as difficulty in synergistically controlling the removal rates of Cu and SiCN, narrow process windows, and difficulty in cleaning surface contaminants after polishing. To address this, a polishing slurry for mixed bonding and its control method are proposed. Summary of the Invention

[0006] In view of this, the present invention provides a polishing slurry for mixed bonding and a method for controlling the slurry thereof, so as to solve or alleviate the technical problems existing in the prior art, and at least provide a beneficial alternative.

[0007] The technical solution of the present invention is implemented as follows: a polishing slurry for mixed bonding, wherein the polishing slurry is used for chemical mechanical polishing of wafers containing Cu layers and SiCN dielectric layers.

[0008] Based on a total mass of 100 wt% of the polishing slurry, the polishing slurry comprises the following components: Colloidal silica abrasive 0.01–1.0 wt% Hydrogen peroxide 0.5–3.0 wt% Amino acids 0.5–8.0 wt% Organic amines 0.001–0.1 wt% 2-Mercaptobenzimidazole 0.01–0.3 wt% Organic quaternary ammonium salts: 0.001–0.05 wt% Polymer stabilizer 0.01–0.5 wt%; Biocides 0.0001–0.01 wt%; pH adjuster; The remainder is deionized water; The pH of the polishing solution is 7.5 to 9.5.

[0009] Furthermore, the particle size of the colloidal silica abrasive is 30–80 nm.

[0010] Furthermore, the pH of the polishing solution is 8.5–9.0.

[0011] Furthermore, the amino acid is selected from one or more of glycine, D-alanine, L-alanine, DL-alanine, β-alanine, and proline.

[0012] Furthermore, the organic amine is selected from one or more of ethylenediamine, 1,3-propanediamine, and 1,4-butanediamine.

[0013] Furthermore, the organic quaternary ammonium salt is selected from one or more of choline bicarbonate, choline hydroxide, choline chloride, tetramethylammonium hydroxide, and tetraethylammonium hydroxide.

[0014] Furthermore, the polymer stabilizer is polyvinylpyrrolidone, and the weight-average molecular weight of the polyvinylpyrrolidone is 10,000 to 50,000.

[0015] Further, the organic quaternary ammonium salt is choline bicarbonate; based on the total mass of the polishing solution of 100 wt%, the content of 2-mercaptobenzimidazole is 0.15-0.22 wt%, the content of choline bicarbonate is 0.006-0.012 wt%, and the pH of the polishing solution is 8.5-9.0.

[0016] The present invention also provides a method for controlling the polishing slurry for mixed bonding, comprising the following steps: S1. Prepare a basic polishing fluid, wherein the basic polishing fluid includes colloidal silica abrasive, hydrogen peroxide, amino acids, organic amines, polymer stabilizers, biocides and deionized water; S2. Add 2-mercaptobenzimidazole and an organic quaternary ammonium salt to the base polishing solution; S3. Based on the total mass of the obtained polishing solution as 100 wt%, adjust the content of the 2-mercaptobenzimidazole to 0.01-0.3 wt% and the content of the organic quaternary ammonium salt to 0.001-0.05 wt%. S4. Add a pH adjuster to adjust the pH of the resulting polishing solution to 7.5–9.5.

[0017] Further, the organic quaternary ammonium salt is choline bicarbonate; based on the total mass of the obtained polishing solution of 100 wt%, the content of 2-mercaptobenzimidazole is 0.15-0.22 wt%, the content of choline bicarbonate is 0.006-0.012 wt%, and the pH of the obtained polishing solution is 8.5-9.0.

[0018] Further, based on a total mass of 100 wt% of the obtained polishing slurry, the content of the colloidal silica abrasive is 0.1 wt%, the content of the hydrogen peroxide is 1.5 wt%, the amino acid is glycine with a content of 3.78 wt%, the organic amine is ethylenediamine with a content of 0.004 wt%, the content of 2-mercaptobenzimidazole is 0.15 wt%, the organic quaternary ammonium salt is choline bicarbonate with a content of 0.008 wt%, the polymer stabilizer is polyvinylpyrrolidone with a content of 0.05 wt%, and the pH of the obtained polishing slurry is 8.5.

[0019] The embodiments of the present invention have the following advantages due to the adoption of the above technical solutions: I. The polishing slurry of the present invention is suitable for mixed bonding structures containing Cu layers and SiCN dielectric layers, and can take into account both the Cu layer removal control and SiCN dielectric layer planarization requirements, thus improving the problem of difficulty in coordinating the Cu and SiCN removal processes in existing polishing systems.

[0020] II. The present invention employs an additive system combining 2-mercaptobenzimidazole and an organic quaternary ammonium salt, wherein 2-mercaptobenzimidazole is used to regulate the Cu layer removal process, and the organic quaternary ammonium salt is used to regulate the SiCN dielectric layer removal process, thereby giving the polishing slurry a clearer component control path.

[0021] Third, by adjusting the content of 2-mercaptobenzimidazole and organic quaternary ammonium salt, the present invention can adjust the composition of the polishing slurry according to different initial wafer morphologies, thereby improving the problem of the narrow process window of the polishing slurry in the prior art and the difficulty in adapting to different Cu depression amounts and SiCN planarization requirements.

[0022] Fourth, the present invention uses a weakly alkaline polishing system composed of colloidal silica abrasive, hydrogen peroxide, amino acids and organic amines, and combines it with polymer stabilizers and biocides, which helps to maintain the stability of the polishing fluid system, reduce the risk of corrosion to equipment, and improve its applicability in mixed bonding chemical mechanical polishing processes.

[0023] The above overview is for illustrative purposes only and is not intended to be limiting in any way. Further aspects, embodiments, and features of the invention will become readily apparent from the following detailed description, in addition to the illustrative aspects, embodiments, and features described above. Detailed Implementation

[0024] This invention provides a synergistic polishing slurry for hybrid bonding, suitable for chemical mechanical polishing of wafers containing Cu and SiCN dielectric layers. The polishing slurry comprises colloidal silica abrasive, hydrogen peroxide, amino acids, organic amines, 2-mercaptobenzimidazole, organic quaternary ammonium salts, polymer stabilizers, biocides, pH adjusters, and deionized water.

[0025] Among them, colloidal silica abrasive is used to provide mechanical removal; hydrogen peroxide is used to participate in the oxidation process of Cu surface; amino acids and organic amines are used to participate in the complexation removal process of Cu surface; 2-mercaptobenzimidazole is used to regulate the Cu layer removal process; organic quaternary ammonium salt is used to regulate the SiCN dielectric layer removal process; polymer stabilizer is used to maintain the stability of the polishing slurry system; biocide is used to inhibit the growth of microorganisms during the storage of polishing slurry; and pH adjuster is used to adjust the pH of polishing slurry.

[0026] In some embodiments, the colloidal silica abrasive has a particle size of 30–80 nm; the amino acid is selected from one or more of glycine, D-alanine, L-alanine, DL-alanine, β-alanine, and proline; the organic amine is selected from one or more of ethylenediamine, 1,3-propanediamine, and 1,4-butanediamine; the organic quaternary ammonium salt is selected from one or more of choline bicarbonate, choline hydroxide, choline chloride, tetramethylammonium hydroxide, and tetraethylammonium hydroxide; and the polymer stabilizer is polyvinylpyrrolidone, wherein the weight-average molecular weight of polyvinylpyrrolidone is 10,000–50,000.

[0027] In this invention, the SiCN / Cu removal rate selectivity ratio is calculated according to the following formula: SiCN / Cu removal rate selectivity = SiCN removal rate / Cu removal rate.

[0028] In this invention, the Dishing repair value and the Erosion repair value are calculated according to the following formulas: Dishing repair value = Dishing value before polishing - Dishing value after polishing; Erosion repair value = Erosion value before polishing - Erosion value after polishing.

[0029] The polishing slurry is prepared as follows: According to the formulations listed in each embodiment or comparative example, weigh out deionized water, amino acids, organic amines, 2-mercaptobenzimidazole, organic quaternary ammonium salts, polymer stabilizers, biocides, and colloidal silica abrasives, mix them evenly, add hydrogen peroxide, and then use a pH adjuster to adjust the pH of the system to the target value to obtain the polishing solution.

[0030] Ammonia and nitric acid can be used as pH adjusters; in specific comparative tests, ammonia or sodium hydroxide can also be used to adjust the pH of the system to the same value.

[0031] The following examples and comparative examples all used the same chemical mechanical polishing conditions: The polishing pressure is 1–2 psi; the wafer rotation speed is 70–90 rpm; the polishing disc rotation speed is 80–100 rpm; the polishing fluid flow rate is 200–400 mL / min; and the polishing time is 60 s.

[0032] Removal rate test method: Cu wafers and SiCN wafers were polished separately, and the film thickness changes before and after polishing were measured. The removal rate was calculated using the following formula: Removal rate = Difference in film thickness before and after polishing / Polishing time.

[0033] The removal rate is measured in Å / min.

[0034] Dishing and Erosion testing methods: The morphology of patterned wafers with Cu and SiCN dielectric layers was tested before and after polishing. The Dishing value before polishing, the Dishing value after polishing, the Erosion value before polishing, and the Erosion value after polishing were recorded, and the corresponding repair values ​​were calculated.

[0035] Example 1 The polishing slurry in this embodiment includes the following components: Colloidal silica abrasive 0.1 wt%, particle size 50 nm; hydrogen peroxide 1.5 wt%; glycine 3.78 wt%; ethylenediamine 0.004 wt%; 2-mercaptobenzimidazole in varying amounts; choline bicarbonate 0.005 wt%. Polyvinylpyrrolidone 0.05 wt%, molecular weight 20000; balance deionized water.

[0036] The pH of the polishing solution was adjusted to 8.5 using ammonia and nitric acid.

[0037] Comparative Example 1 Except for the absence of 2-mercaptobenzimidazole, the other components, contents, pH and polishing conditions were the same as in Example 1.

[0038] Test results: Table 1: Effect of 2-mercaptobenzimidazole content on polishing properties of Cu and SiCN

[0039] As shown in Table 1, when the 2-mercaptobenzimidazole content is 0, the Cu removal rate is high, the SiCN / Cu selectivity ratio is 0.70, and the Dishing and Erosion repair values ​​are low.

[0040] As the 2-mercaptobenzimidazole content increased from 0.05 wt% to 0.22 wt%, the Cu removal rate decreased from 13500 Å / min to 8300 Å / min, while the SiCN removal rate remained within the range of 11000–11410 Å / min. This indicates that 2-mercaptobenzimidazole mainly affects the Cu removal process and has a relatively small impact on the SiCN removal rate.

[0041] When the 2-mercaptobenzimidazole content was 0.15 wt%, the Cu removal rate was 8800 Å / min, the SiCN / Cu selectivity was 1.30, the SiCN / Cu selectivity was 38 Å after Dishing polishing, and the SiCN / Cu selectivity was 32 Å after Erosion polishing. Further increasing the 2-mercaptobenzimidazole content to 0.18 wt% and 0.22 wt% resulted in a slower change in the Cu removal rate, while the SiCN / Cu selectivity remained between 1.36 and 1.37. Therefore, the preferred 2-mercaptobenzimidazole content is 0.15–0.22 wt%.

[0042] Example 2 The polishing slurry in this embodiment includes the following components: Colloidal silica abrasive 0.1 wt%, particle size 50 nm; hydrogen peroxide 1.5 wt%; glycine 3.78 wt%; ethylenediamine 0.004 wt%; 2-mercaptobenzimidazole 0.15 wt%; choline bicarbonate in varying amounts; polyvinylpyrrolidone 0.05 wt%, molecular weight 20000; balance deionized water.

[0043] The pH of the polishing solution was adjusted to 8.5 using ammonia and nitric acid.

[0044] Comparative Example 2 Except for the absence of choline bicarbonate, the other components, contents, pH and polishing conditions were the same as in Example 2.

[0045] Test results: Table 2: Effect of choline bicarbonate content on polishing properties of Cu and SiCN

[0046] As shown in Table 2, when choline bicarbonate is not added, the SiCN removal rate is only 450 Å / min and the SiCN / Cu selectivity ratio is 0.05, indicating that the SiCN removal in this system is insufficient.

[0047] As the choline bicarbonate content increased from 0.002 wt% to 0.012 wt%, the SiCN removal rate increased from 6000 Å / min to 14100 Å / min, while the Cu removal rate remained in the range of 8800–9400 Å / min. These results indicate that choline bicarbonate primarily regulates the SiCN removal process and has a relatively small impact on the Cu removal rate.

[0048] When the choline bicarbonate content is 0.006 wt%, the SiCN / Cu selectivity ratio is 1.15; when the choline bicarbonate content is 0.008 wt%, the SiCN / Cu selectivity ratio is 1.30; and when the choline bicarbonate content is 0.012 wt%, the SiCN / Cu selectivity ratio is 1.50. Therefore, the preferred choline bicarbonate content is 0.006–0.012 wt%.

[0049] Example 3 This embodiment uses a base polishing slurry, which includes the following components: Colloidal silica abrasive 0.1 wt%, particle size 50 nm; hydrogen peroxide 1.5 wt%; glycine 3.78 wt%; ethylenediamine 0.004 wt%; 2-mercaptobenzimidazole 0.15 wt%; polyvinylpyrrolidone 0.05 wt%, molecular weight 20000; balance deionized water.

[0050] In the above-mentioned basic polishing solution, the pH of the system was adjusted to 8.5 using the following three methods: Group 1: Add 0.008 wt% choline bicarbonate. Group 2: pH is adjusted using ammonia water, without adding organic quaternary ammonium salts; Group 3: pH is adjusted using sodium hydroxide, without the addition of organic quaternary ammonium salts.

[0051] The polishing conditions were the same as in Example 1.

[0052] Test results: Table 3: Comparison of Organic Quaternary Ammonium Salts and Conventional Alkaline pH Adjustment Methods

[0053] Table 3 shows that, under the condition of pH 8.5, when only ammonia or sodium hydroxide is used to adjust the pH, the SiCN removal rates are 1850 Å / min and 620 Å / min, respectively, and the SiCN / Cu selectivity ratios are 0.20 and 0.07, respectively. In contrast, when 0.008 wt% choline bicarbonate is added to the polishing solution, the SiCN removal rate is 12000 Å / min, and the SiCN / Cu selectivity ratio is 1.30.

[0054] The above results indicate that the increased SiCN removal rate in the polishing slurry system of this invention is not solely due to the weakly alkaline pH environment, but is related to the addition of organic quaternary ammonium salts. These organic quaternary ammonium salts can participate in regulating the interfacial interaction between the SiCN surface and the colloidal silica abrasive, thereby promoting SiCN removal.

[0055] Comparative Example 3: Polishing solution without the addition of 2-mercaptobenzimidazole and choline bicarbonate This comparative example illustrates the effect of 2-mercaptobenzimidazole and choline bicarbonate as additives on the polishing system.

[0056] The polishing slurry in this comparative example comprises the following components: The abrasive consists of 1.0 wt% colloidal silica with a particle size of 50 nm; 1.5 wt% hydrogen peroxide; 3.78 wt% glycine; 0.004 wt% ethylenediamine; 0.05 wt% polyvinylpyrrolidone with a molecular weight of 20,000; and the balance is deionized water.

[0057] The pH of the polishing solution was adjusted to 8.5 using ammonia and nitric acid. This comparative example does not contain 2-mercaptobenzimidazole or choline bicarbonate.

[0058] Test results: Table 4: Polishing performance without the addition of 2-mercaptobenzimidazole and choline bicarbonate

[0059] Table 4 shows that without the addition of 2-mercaptobenzimidazole and choline bicarbonate, the SiCN / Cu selectivity ratio is only 0.03, and the Dishing and Erosion repair values ​​are low, indicating that this polishing slurry is difficult to simultaneously control Cu removal and remove the SiCN dielectric layer. This result further demonstrates that the combination of 2-mercaptobenzimidazole and choline bicarbonate plays a crucial role in regulating the polishing process of the Cu and SiCN dielectric layers.

[0060] Test case: Post-CMP cleaning validation The wafer polished by the polishing solution of the present invention was brushed with an alkaline cleaning solution with a pH of 10 for 60 seconds, then rinsed with deionized water, and then subjected to N2 plasma activation treatment, wherein the plasma activation power was 100 W and the treatment time was 15 seconds.

[0061] X-ray photoelectron spectroscopy was used to analyze the surface of the cleaned and activated wafers. The results showed that the N1s peak corresponding to the 2-mercaptobenzimidazole residue on the copper surface disappeared after cleaning, and the surface carbon contaminants were reduced.

[0062] The results indicate that, after the above cleaning and activation treatments, the polished wafer surface can meet the surface cleanliness requirements for hybrid bonding.

[0063] Results analysis: As shown in Example 1 and Table 1, 2-mercaptobenzimidazole can regulate the Cu removal process in the polishing solution system of this invention. With increasing 2-mercaptobenzimidazole content, the Cu removal rate decreases, while the SiCN removal rate remains essentially stable.

[0064] As shown in Example 2 and Table 2, choline bicarbonate can regulate the SiCN removal process in the polishing solution system of this invention. With increasing choline bicarbonate content, the SiCN removal rate increases, while the Cu removal rate changes relatively little.

[0065] As can be seen from Example 3 and Table 3, under the same pH conditions, when only ammonia or sodium hydroxide is used to adjust the pH, the SiCN removal rate is significantly lower than that of the system with added choline bicarbonate. This indicates that organic quaternary ammonium salts have a different effect on the SiCN removal process than simple pH adjustment.

[0066] As shown in Comparative Example 3 and Table 4, without the addition of 2-mercaptobenzimidazole and choline bicarbonate, the SiCN / Cu selectivity is relatively low, and the Dishing and Erosion repair effects are weak. This indicates that the combination of the two is an important factor in achieving Cu / SiCN mixed bonding polishing control in the polishing slurry of this invention.

[0067] In summary, this invention utilizes a weakly alkaline polishing system composed of colloidal silica abrasive, hydrogen peroxide, amino acids, organic amines, 2-mercaptobenzimidazole, organic quaternary ammonium salts, polymer stabilizers, biocides, and pH adjusters. By adjusting the content of 2-mercaptobenzimidazole and organic quaternary ammonium salts, the polishing solution is made suitable for chemical mechanical polishing of mixed-bonded structures containing Cu layers and SiCN dielectric layers.

[0068] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in the present invention, and these should all be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A polishing slurry for mixed bonding, characterized in that, The polishing slurry is used for chemical mechanical polishing of wafers containing Cu and SiCN dielectric layers; based on a total mass of 100 wt%, the polishing slurry comprises the following components: Colloidal silica abrasive 0.01–1.0 wt% Hydrogen peroxide 0.5–3.0 wt% Amino acids 0.5–8.0 wt% Organic amines 0.001–0.1 wt% 2-Mercaptobenzimidazole 0.01–0.3 wt% Organic quaternary ammonium salts: 0.001–0.05 wt% Polymer stabilizer 0.01–0.5 wt%; Biocides 0.0001–0.01 wt%; pH adjuster; The remainder is deionized water; The pH of the polishing solution is 7.5 to 9.

5.

2. The polishing slurry according to claim 1, characterized in that, The particle size of the colloidal silica abrasive is 30–80 nm.

3. The polishing slurry according to claim 1, characterized in that, The pH of the polishing solution is 8.5 to 9.

0.

4. The polishing slurry according to claim 1, characterized in that, The amino acid is selected from one or more of glycine, D-alanine, L-alanine, DL-alanine, β-alanine, and proline.

5. The polishing slurry according to claim 1, characterized in that, The organic amine is selected from one or more of ethylenediamine, 1,3-propanediamine and 1,4-butanediamine.

6. The polishing slurry according to claim 1, characterized in that, The organic quaternary ammonium salt is selected from one or more of choline bicarbonate, choline hydroxide, choline chloride, tetramethylammonium hydroxide, and tetraethylammonium hydroxide; the polymer stabilizer is polyvinylpyrrolidone, and the weight average molecular weight of the polyvinylpyrrolidone is 10,000 to 50,000.

7. The polishing slurry according to claim 1, characterized in that, The organic quaternary ammonium salt is choline bicarbonate; based on the total mass of the polishing solution of 100 wt%, the content of 2-mercaptobenzimidazole is 0.15-0.22 wt%, the content of choline bicarbonate is 0.006-0.012 wt%, and the pH of the polishing solution is 8.5-9.

0.

8. A method for controlling the polishing slurry for mixed bonding, characterized in that, Includes the following steps: S1. Prepare a basic polishing fluid, wherein the basic polishing fluid includes colloidal silica abrasive, hydrogen peroxide, amino acids, organic amines, polymer stabilizers, biocides and deionized water; S2. Add 2-mercaptobenzimidazole and an organic quaternary ammonium salt to the base polishing solution; S3. Based on the total mass of the obtained polishing solution as 100 wt%, adjust the content of the 2-mercaptobenzimidazole to 0.01-0.3 wt% and the content of the organic quaternary ammonium salt to 0.001-0.05 wt%. S4. Add a pH adjuster to adjust the pH of the resulting polishing solution to 7.5–9.

5.

9. The polishing slurry control method according to claim 8, characterized in that, The organic quaternary ammonium salt is choline bicarbonate; based on the total mass of the obtained polishing solution of 100 wt%, the content of 2-mercaptobenzimidazole is 0.15-0.22 wt%, the content of choline bicarbonate is 0.006-0.012 wt%, and the pH of the obtained polishing solution is 8.5-9.

0.

10. The polishing slurry control method according to claim 8, characterized in that, Based on a total mass of 100 wt% of the obtained polishing slurry, the content of the colloidal silica abrasive is 0.1 wt%, the content of the hydrogen peroxide is 1.5 wt%, the amino acid is glycine with a content of 3.78 wt%, the organic amine is ethylenediamine with a content of 0.004 wt%, the content of 2-mercaptobenzimidazole is 0.15 wt%, the organic quaternary ammonium salt is choline bicarbonate with a content of 0.008 wt%, the polymer stabilizer is polyvinylpyrrolidone with a content of 0.05 wt%, and the pH of the obtained polishing slurry is 8.5.

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