GOI Weakly Alkaline Cerium Oxide Polishing Fluid and Its Preparation Method

Abstract

This invention provides a weakly alkaline cerium oxide polishing slurry for GOI substrates and its preparation method, belonging to the field of semiconductor material processing technology. The polishing slurry comprises the following components by weight percentage: 0.5%–5.0% surface-modified nano-cerium oxide abrasive, 0.05%–1.0% dispersant stabilizer, 0.2%–2.0% oxidant, 0.01%–0.5% selective inhibitor, a weakly alkaline pH adjuster to adjust the pH to 8.0–10.0, and the remainder being deionized water. The nano-cerium oxide abrasive is surface-modified by carboxylic acid, phosphoric acid, or sulfonic acid modifiers. The method includes abrasive modification, dispersion, feeding, pH adjustment, and filtration. This polishing slurry is suitable for the fine polishing stage of chemical mechanical polishing (CMP) of GOI substrates, enabling moderate and controllable removal of the germanium layer, improving Ge / SiO2 selectivity, reducing the risk of buried oxide layer corrosion, and improving the surface quality after polishing.

Description

Technical Field

[0001] This invention relates to the field of semiconductor material processing technology, and in particular to GOI weakly alkaline cerium oxide polishing slurry and its preparation method. Background Technology

[0002] Germanium-on-Insulator (GOI) has promising applications in high-speed, low-power devices due to the high carrier mobility of germanium. The fabrication of GOI substrates typically employs a two-step process: mechanical polishing followed by chemical mechanical polishing. The fine polishing stage of chemical mechanical polishing is primarily used to further reduce surface roughness, precisely control the thickness of the top germanium layer, and ensure the integrity of the buried oxide layer structure.

[0003] However, GOI fine polishing differs from ordinary rough polishing, placing higher demands on removal rate, surface quality, selectivity, and endpoint control. Existing technologies mainly suffer from the following problems: Firstly, some existing polishing slurries focus more on higher removal rates. Although this is beneficial for improving processing efficiency, in the GOI fine polishing stage, excessively high removal rates are not conducive to the precise control of the top germanium removal thickness, which can easily lead to over-polishing and may exacerbate the preferential reaction of surface defect areas, affecting surface smoothness.

[0004] Secondly, in GOI structures, the buried oxide layer is typically used as a stop layer for fine polishing, requiring the polishing slurry to have high selectivity between the germanium layer and the buried oxide layer. If the selectivity is insufficient, SiO2 can easily continue to be removed when approaching or reaching the buried oxide layer, leading to damage to the buried oxide layer and affecting the integrity of the substrate structure.

[0005] Third, silica is prone to corrosion under strongly alkaline conditions. If the pH of the polishing solution is too high, although it may increase the removal rate of germanium, it will also increase the risk of chemical corrosion of the buried oxide layer, which is not conducive to the endpoint control and buried oxide layer protection during the GOI fine polishing process.

[0006] Fourth, although cerium oxide abrasive has good chemical-mechanical synergistic polishing performance, it is prone to agglomeration under weakly alkaline conditions due to its low absolute value of surface charge. Agglomerated particles are prone to introducing surface defects such as scratches during the polishing process, making it difficult to meet the high surface quality requirements of GOI fine polishing. Therefore, a weakly alkaline cerium oxide polishing slurry with GOI and its preparation method are proposed. Summary of the Invention

[0007] In view of this, the present invention provides a GOI weakly alkaline cerium oxide polishing slurry and its preparation method to solve or alleviate the technical problems existing in the prior art, and at least provide a beneficial alternative.

[0008] The technical solution of this invention is implemented as follows: GOI weakly alkaline cerium oxide polishing slurry, wherein the polishing slurry is composed of the following components by weight percentage: Surface-modified nano-cerium oxide abrasive: 0.5%–5.0%; Dispersant stabilizer: 0.05%–1.0%; Oxidant: 0.2%–2.0%; Selective inhibitor: 0.01%–0.5%; Weakly alkaline pH adjuster: used to adjust the pH of the polishing solution to 8.0–10.0; The balance is deionized water.

[0009] Preferably, the polishing solution has a pH value of 8.5 to 9.5, more preferably 9.0.

[0010] Preferably, the average particle size of the surface-modified nano-cerium oxide abrasive is 20nm to 60nm, more preferably 30nm to 50nm.

[0011] Preferably, the nano-cerium oxide abrasive is surface-modified with a carboxylic acid, phosphoric acid, or sulfonic acid modifier, wherein the modifier is selected from one or more of citric acid, tartaric acid, polyacrylic acid, phytic acid, phosphate esters, and polystyrene sulfonic acid; preferably citric acid or phytic acid. Surface modification introduces negatively charged functional groups onto the surface of cerium oxide particles under weakly alkaline conditions, thereby enhancing the electrostatic repulsion between particles and strengthening the steric hindrance effect, thus improving the dispersion stability of the cerium oxide abrasive in the polishing fluid.

[0012] Preferably, the weakly alkaline pH adjuster is selected from one or more of ammonia, tetramethylammonium hydroxide, ethylenediamine, and organic amines, and is preferably ammonia or tetramethylammonium hydroxide.

[0013] Preferably, the dispersant stabilizer is selected from nonionic surfactants or anionic surfactants; wherein the nonionic surfactant is selected from one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, and polyethylene glycol octylphenyl ether; the anionic surfactant is selected from one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and sodium polyacrylate; preferably, fatty alcohol polyoxyethylene ether is used, or a combination of fatty alcohol polyoxyethylene ether and sodium polyacrylate is used.

[0014] Preferably, the oxidant is selected from one or more of hydrogen peroxide, peracetic acid, potassium iodate, and potassium permanganate, with hydrogen peroxide being the most preferred, and the content preferably being 0.3% to 1.5%. The oxidant is used to promote the formation of an easily removable oxide layer on the germanium surface, thereby achieving synergistic polishing through chemical and mechanical action.

[0015] Preferably, the selective inhibitor is selected from one or more of benzotriazole, 2-mercaptobenzothiazole, polyethylene glycol, and polyvinylpyrrolidone, and is more preferably benzotriazole or 2-mercaptobenzothiazole. The selective inhibitor is used to suppress chemical erosion and mechanical removal of the buried oxide layer and the silicon substrate surface, and to improve the selectivity of the polishing slurry for the germanium layer relative to the SiO2 layer.

[0016] The present invention also provides a method for preparing the above-mentioned GOI weakly alkaline cerium oxide polishing solution, comprising the following steps: S1. Disperse nano-cerium oxide powder in deionized water and obtain a cerium oxide suspension by ultrasonic treatment; add a surface modifier to the suspension and adjust the pH of the system to 8.5-9.0, and reflux and stir at 60-80℃ for 4-8 hours to allow the modifier to bind to the surface of the cerium oxide particles; after the reaction is completed, centrifuge, wash and dry to obtain surface-modified nano-cerium oxide abrasive. S2. Add the obtained surface-modified nano-cerium oxide abrasive to deionized water according to the set ratio, and disperse it by ultrasonication for 20-30 minutes to obtain a uniform abrasive dispersion. S3. Under stirring conditions, add the dispersant stabilizer, oxidant and selective inhibitor to the abrasive dispersion in sequence, and continue stirring for 15 to 20 minutes to ensure that the components are fully mixed. S4. Adjust the pH of the obtained mixture to 8.0-10.0 using a weakly alkaline pH adjuster, preferably to 8.5-9.5; S5. Filter the prepared polishing solution through a 0.2μm filter membrane to obtain GOI weakly alkaline cerium oxide fine polishing solution.

[0017] The embodiments of the present invention have the following advantages due to the adoption of the above technical solutions: I. This invention applies the polishing slurry system to the GOI fine polishing stage, and through the weak alkaline system and the synergistic regulation of each component, the germanium layer has a moderate and controllable removal rate, which is conducive to accurately controlling the removal thickness of the top germanium layer and reducing the risk of over-polishing.

[0018] Second, this invention improves the selectivity of the polishing slurry for the germanium layer relative to the buried oxide layer by combining surface-modified nano-cerium oxide abrasive, oxidant and selective inhibitor, and facilitates the formation of more obvious signal changes at the interface between the germanium layer and the buried oxide layer, thereby achieving effective protection of the buried oxide layer and improving the accuracy of endpoint control.

[0019] Third, this invention controls the polishing slurry system within a weakly alkaline range, which reduces the risk of chemical corrosion of the SiO2 buried oxide layer while ensuring the efficiency of germanium layer removal. This is beneficial for maintaining the integrity of the GOI structure and broadening the window of fine polishing process.

[0020] Fourth, this invention modifies the surface of nano-cerium oxide abrasive by introducing negatively charged functional groups suitable for weakly alkaline environments on its surface, thereby enhancing the electrostatic repulsion and steric hindrance between particles and improving the dispersion stability of the abrasive in the polishing fluid. This reduces the surface scratch density and surface roughness after polishing, which is beneficial for obtaining a high-quality finely polished surface. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the preparation process of the GOI weakly alkaline cerium oxide polishing solution of the present invention. Detailed Implementation

[0023] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0024] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0025] like Figure 1 As shown, this invention provides a weakly alkaline cerium oxide polishing slurry for GOI and its preparation method. This polishing slurry is specifically used in the fine polishing stage of the chemical mechanical polishing process for germanium-on-insulator (GOI) substrates. By employing the synergistic effect of surface-modified nano-cerium oxide abrasive, weakly alkaline pH adjuster, dispersant stabilizer, oxidant and selective inhibitor, it achieves effective protection of the buried oxide layer and reduction of surface roughness after polishing while ensuring a moderate and controllable removal rate of the germanium layer.

[0026] In this embodiment, the surface-modified nano-cerium oxide abrasive can be obtained by surface modification with carboxylic acid, phosphoric acid, or sulfonic acid modifiers under weakly alkaline conditions. The modifier is preferably selected from one or more of citric acid, tartaric acid, polyacrylic acid, phytic acid, phosphate esters, or polystyrene sulfonic acid. The weakly alkaline pH adjuster is preferably ammonia or tetramethylammonium hydroxide. The dispersion stabilizer can be a nonionic or anionic surfactant. The oxidant is preferably hydrogen peroxide. The selective inhibitor is preferably benzotriazole or 2-mercaptobenzothiazole.

[0027] Example 1 (Citrate Acid Modification) This embodiment provides a GOI weakly alkaline cerium oxide polishing slurry, which, by weight percentage, consists of: 2.0% citric acid surface-modified nano-cerium oxide (average particle size 40nm); and 1.0% hydrogen peroxide (30% aqueous solution). Benzotriazole (BTA) 0.05%; AEO-9 (fatty alcohol polyoxyethylene ether) 0.1%; ammonia (25%) to adjust pH to 9.0; deionized water as the balance.

[0028] The surface modification methods for cerium oxide are as follows: Take 10g of nano-cerium oxide powder (average particle size 40nm, purity 99.9%), disperse it in 200mL of deionized water, and sonicate for 30 minutes; add 0.3g of citric acid, and adjust the pH to 8.5 with ammonia; reflux and stir at 70℃ for 6 hours; after the reaction is completed, centrifuge at 8000rpm for 15 minutes; wash 3 times with deionized water; and then vacuum dry at 60℃ for 12 hours to obtain citric acid surface-modified nano-cerium oxide abrasive.

[0029] The polishing slurry is prepared as follows: 2.0 g of the surface-modified cerium oxide abrasive was dispersed in deionized water and sonicated for 20 minutes. Under stirring, 0.1 g of AEO-9, 3.33 g of hydrogen peroxide (30% aqueous solution), and 0.05 g of BTA were added sequentially. The pH was adjusted to 9.0 with ammonia. The deionized water was added to a final volume of 100 g. The solution was filtered through a 0.2 μm filter membrane to obtain a GOI weakly alkaline cerium oxide polishing solution.

[0030] Example 2 (Phytic Acid Modification) This embodiment provides a GOI weakly alkaline cerium oxide polishing solution, which, by weight percentage, consists of: 2.0% phytic acid surface-modified nano-cerium oxide (average particle size 40nm); 1.0% hydrogen peroxide (30% aqueous solution); 0.03% 2-mercaptobenzothiazole (MBT); 0.12% Triton X-100; 25% tetramethylammonium hydroxide to adjust the pH to 8.8; and the balance being deionized water.

[0031] The surface modification methods for cerium oxide are as follows: Take 10g of nano-cerium oxide powder (average particle size 40nm), disperse it in 200mL of deionized water, and sonicate for 30 minutes; add 0.25g of phytic acid (50% aqueous solution), and adjust the pH to 8.5 with tetramethylammonium hydroxide; reflux and stir at 70℃ for 6 hours; after the reaction is completed, centrifuge and separate; wash 3 times with deionized water; and then vacuum dry at 60℃ for 12 hours to obtain phytic acid surface-modified nano-cerium oxide abrasive.

[0032] The polishing slurry was prepared using the same method as in Example 1.

[0033] Example 3 (Polyacrylic Acid Modification) This embodiment provides a GOI weakly alkaline cerium oxide polishing solution, which, by weight percentage, consists of: 2.0% polyacrylic acid (PAA, Mw≈2000) surface-modified nano-cerium oxide (average particle size 50nm); 0.8% hydrogen peroxide (30% aqueous solution); 0.05% benzotriazole (BTA); 0.15% OP-10 (alkylphenol polyoxyethylene ether); ammonia (25%) to adjust the pH to 9.0; and deionized water as the balance.

[0034] The surface modification methods for cerium oxide are as follows: Take 10g of nano-cerium oxide powder (average particle size 50nm), disperse it in 200mL of deionized water, and sonicate for 30 minutes; add 0.4g of polyacrylic acid (25% aqueous solution), adjust the pH to 8.5 with ammonia water; reflux and stir at 70℃ for 6 hours; after the reaction is completed, centrifuge and separate; wash 3 times with deionized water; and then vacuum dry at 60℃ for 12 hours to obtain polyacrylic acid surface-modified nano-cerium oxide abrasive.

[0035] The polishing slurry was prepared using the same method as in Example 1.

[0036] Example 4 (Tartaric Acid Modification) This embodiment provides a GOI weakly alkaline cerium oxide polishing solution, which, by weight percentage, consists of: 1.5% tartaric acid surface-modified nano-cerium oxide (average particle size 30nm); 1.2% hydrogen peroxide (30% aqueous solution); 0.08% polyethylene glycol (PEG-400); 0.1% AEO-9; pH adjusted to 9.0 with ammonia (25%); and the balance being deionized water.

[0037] The surface modification methods for cerium oxide are as follows: Take 10g of nano-cerium oxide powder (average particle size 30nm), disperse it in 200mL of deionized water, and sonicate for 30 minutes; add 0.35g of tartaric acid, and adjust the pH to 8.5 with ammonia; reflux and stir at 70℃ for 6 hours; after the reaction is completed, centrifuge and separate; wash 3 times with deionized water; and then vacuum dry at 60℃ for 12 hours to obtain tartaric acid surface-modified nano-cerium oxide abrasive.

[0038] The polishing slurry was prepared using the same method as in Example 1.

[0039] Comparative Example 1 (unmodified cerium oxide, strongly alkaline system, simulating coarse polishing conditions) This comparative example includes, by weight percentage: Unmodified nano-cerium oxide (average particle size 40nm) 2.0%; hydrogen peroxide 1.0%; benzotriazole (BTA) 0.05%; AEO-9 0.1%; pH adjusted to 11.0 with potassium hydroxide; deionized water as the balance.

[0040] This comparative example is used to characterize the suitability of a strongly alkaline, unmodified cerium oxide system for GOI fine polishing.

[0041] Comparative Example 2 (Unmodified cerium oxide, weakly alkaline system) This comparative example includes, by weight percentage: Unmodified nano-cerium oxide (average particle size 40nm) 2.0%; hydrogen peroxide 1.0%; benzotriazole (BTA) 0.05%; AEO-9 0.1%; pH adjusted to 9.0 with ammonia; deionized water as the balance.

[0042] This comparative example is used to characterize the effects of cerium oxide's dispersion stability, surface quality, and polishing selectivity under weakly alkaline conditions without surface modification.

[0043] Performance testing: The polishing slurries obtained in Examples 1-4 and Comparative Examples 1-2 were used to perform fine polishing tests on GOI substrates that had undergone mechanical polishing pretreatment. The structural parameters of the GOI substrates are as follows: the remaining thickness of the top Ge layer is 150 nm, the thickness of the buried oxide layer SiO2 is 150 nm, the thickness of the silicon substrate is 675 μm, and the initial surface roughness RMS is approximately 2.5 nm.

[0044] 1. Polishing conditions Polishing equipment: CETR CP-4 polishing machine; polishing pad: IC1000; polishing pressure: 3psi; polishing disc speed: 70rpm; polishing fluid flow rate: 150mL / min; polishing time: 3 minutes; polishing temperature: room temperature (25±2℃).

[0045] 2. Testing Methods Film thickness measurement: determined using an elliptic polarization spectrometer; Surface roughness: measured using atomic force microscopy (AFM), with a scanning range of 5 μm × 5 μm; Surface scratches: The scratch density was observed and statistically analyzed using an optical microscope (×400); Dispersion stability: The static settling method was used to record the settling rate over 48 hours; Zeta potential: Measured using a Zeta potential analyzer at pH 9.0; Coefficient of friction: recorded in real time by the torque sensor of the CETR CP-4 polishing machine; Reflected signal: Monitored using a device equipped with a laser interferometric endpoint detection system (wavelength 670nm).

[0046] 3. Fine polishing performance test results Table 1: Comparison of Fine Polishing Performance of Different Polishing Slurry Systems

[0047] Table 1 shows that cerium oxide abrasives modified with carboxylic acids or phosphoric acids exhibit significantly higher absolute zeta potential values ​​in weakly alkaline systems, all exceeding 45 mV. Simultaneously, the sedimentation rate after 48 hours is significantly reduced, indicating that their dispersion stability is significantly better than that of the unmodified cerium oxide system. In contrast, Comparative Examples 1 and 2 show lower absolute zeta potential values ​​and significantly higher sedimentation rates, indicating that unmodified cerium oxide is more prone to agglomeration in the polishing slurry.

[0048] In terms of removal rate and selectivity, the Ge removal rate in Examples 1-4 was 118-130 nm / min, which is within the range suitable for fine polishing of GOI. Meanwhile, the SiO2 removal rate was only 1.4-1.8 nm / min, and the Ge / SiO2 selectivity ratio reached 72:1-84:1, effectively balancing the removal of the germanium layer and the protection of the buried oxide layer. In contrast, although Comparative Example 1 had a higher Ge removal rate, its SiO2 removal rate was as high as 12.5 nm / min, and the Ge / SiO2 selectivity ratio was only 11.8:1, resulting in severe corrosion of the buried oxide layer, making it unsuitable for fine polishing. Comparative Example 2, under weakly alkaline conditions, had a lower SiO2 removal rate than Comparative Example 1, but it was still 4.2 nm / min, indicating relatively low selectivity.

[0049] In terms of surface quality, the RMS surface roughness after polishing in Examples 1-4 is no higher than 0.24 nm, and the scratch density is no higher than 3 scratches / cm. 2 Example 2 achieved an RMS wavelength of 0.18 nm and a scratch density of ≤1 scratch / cm. 2 The surface quality was optimal. The surface roughness of Comparative Example 1 and Comparative Example 2 after polishing were 1.35 nm and 0.68 nm, respectively, with a significant increase in scratch density, indicating that the unmodified abrasive system could not meet the atomically smooth surface requirements of GOI fine polishing.

[0050] From the perspective of endpoint control-related indicators, the friction coefficient reduction at the interface between the Ge layer and the SiO2 layer in Examples 1 to 4 all reached 42% to 45%, and the reflection signal was clear, which is conducive to the identification of the polishing endpoint; while the friction coefficient reduction in Comparative Examples 1 and 2 was only 22% and 26%, respectively, and the reflection signal was blurry or general, which is not conducive to accurately judging the fine polishing endpoint.

[0051] Example 5: Effect of different pH conditions on fine polishing performance Based on the polishing slurry formulation of Example 1, i.e. using citric acid-modified CeO2 as the abrasive, ammonia water was used to adjust different pH values ​​to investigate the effect of pH on fine polishing performance.

[0052] Table 2. Test results at different pH values.

[0053]

[0054] As shown in Table 2, when the pH value increases from 8.0 to 10.0, the Ge removal rate gradually increases, but the SiO2 removal rate also increases significantly, leading to a decrease in Ge / SiO2 selectivity. At pH 8.0, although SiO2 corrosion is low, the Ge removal rate is also low; at pH 9.0, the Ge removal rate is 125 nm / min, the SiO2 removal rate is 1.6 nm / min, the Ge / SiO2 selectivity ratio is 78:1, and the surface roughness RMS is 0.21 nm, exhibiting the best overall performance. When the pH rises to 9.5 and 10.0, slight or visible corrosion occurs in the buried oxide layer, indicating that excessively high pH is detrimental to the protection of the buried oxide layer. Therefore, the preferred pH range of the polishing solution in this invention is 8.5–9.5, more preferably 9.0.

[0055] Example 6: Effect of abrasive concentration on fine polishing performance Based on the formulation of Example 1, i.e., using citric acid-modified CeO2 and a pH of 9.0, the effect of different abrasive concentrations on fine polishing performance was investigated.

[0056] Table 3. Test results at different CeO2 concentrations.

[0057]

[0058] Table 3 shows that the Ge removal rate generally increases with the increase of CeO2 concentration. However, when the concentration is too high, the surface roughness and scratch density both tend to increase, and the sedimentation rate increases, resulting in a decrease in surface quality. Considering the removal efficiency, surface quality, and stability, the preferred abrasive concentration range is 1.0% to 3.0%, with 2.0% showing the best overall effect.

[0059] Example 7: Comparison of the effects of different surface modifiers Under the same formulation, i.e., keeping conditions such as 2.0wt% modified CeO2 and pH 9.0 constant, the effects of different surface modifiers on the dispersion stability and fine polishing performance of cerium oxide abrasive were compared.

[0060] Table 4. Comparison of the effects of different surface modifiers.

[0061]

[0062] Table 4 shows that various carboxylic acid or phosphoric acid modifiers can significantly improve the electronegativity and dispersion stability of cerium oxide particles under pH 9.0 conditions. Among them, phytic acid modification showed the highest absolute zeta potential (-52.6 mV), the lowest 48-hour sedimentation rate (only 2.8%), and the lowest surface roughness after polishing (0.18 nm), exhibiting the best overall performance. Citric acid modification showed performance similar to phytic acid, while having relatively lower raw material costs, making it a cost-effective option.

[0063] Based on the above embodiments, comparative examples, and parameter optimization experiments, it can be seen that the GOI weakly alkaline cerium oxide polishing slurry of the present invention, by using surface-modified nano-cerium oxide abrasives under weakly alkaline conditions, and in conjunction with the synergistic effect of oxidants, dispersants, stabilizers, and selective inhibitors, can achieve the following technical effects in the GOI polishing process: (1) The Ge removal rate can be controlled at around 118-130 nm / min, which is within a moderate and controllable range and is suitable for precise control of the removal thickness in the fine polishing stage. (2) The SiO2 removal rate can be controlled at 1.4 to 1.8 nm / min, and the Ge / SiO2 selectivity ratio reaches 72:1 to 84:1, which can effectively protect the buried oxide layer; (3) After polishing, the surface roughness RMS can be reduced to 0.18-0.24 nm, and the scratch density is no higher than 3 scratches / cm. 2 This meets the requirement for atomically flat surfaces; (4) The sedimentation rate can be controlled within 5% after 48 hours, which indicates that the polishing fluid has good storage stability and use stability. (5) There is a significant decrease in the friction coefficient and a clear change in the reflection signal at the Ge / SiO2 interface, which is beneficial for the identification and control of the fine polishing endpoint.

[0064] In summary, the GOI weakly alkaline cerium oxide polishing slurry and its preparation method provided by this invention can effectively solve the problems of difficulty in simultaneously achieving removal rate, selectivity, surface quality and buried oxide layer protection in the GOI polishing stage of the prior art, and has good application prospects.

[0065] The above description is merely a specific embodiment 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 GOI weakly alkaline cerium oxide polishing slurry, characterized in that, The polishing slurry is specifically designed for the fine polishing stage of the chemical mechanical polishing (CMP) process for GOI substrates and consists of the following components by weight percentage: Surface-modified nano-cerium oxide abrasive 0.5%-5.0%; weakly alkaline pH adjuster, used to adjust the pH value to 8.0-10.0; dispersant stabilizer 0.05%-1.0%; oxidant 0.2%-2.0%; selective inhibitor 0.01%-0.5%; balance is deionized water.

2. The GOI weakly alkaline cerium oxide polishing slurry according to claim 1, characterized in that, The nano-cerium oxide abrasive is surface modified by a carboxylic acid, phosphoric acid, or sulfonic acid modifier. The modifier is selected from one or more of citric acid, tartaric acid, polyacrylic acid (PAA), phytic acid, phosphate ester, or polystyrene sulfonic acid (PSS), preferably citric acid or phytic acid. The modified cerium oxide has an absolute zeta potential of ≥40 mV under pH 9.0 conditions.

3. The GOI weakly alkaline cerium oxide polishing slurry according to claim 1, characterized in that, The average particle size of the nano-cerium oxide abrasive is 20 nm-60 nm, preferably 30 nm-50 nm.

4. The GOI weakly alkaline cerium oxide polishing slurry according to claim 1, characterized in that, The weakly alkaline pH adjuster is selected from one or more of ammonia, tetramethylammonium hydroxide (TMAH), ethylenediamine, or organic amines, preferably ammonia or TMAH; the pH value of the polishing solution is 8.5-9.5, with 9.0 being optimal.

5. The GOI weakly alkaline cerium oxide polishing slurry according to claim 1, characterized in that, The dispersant stabilizer is selected from nonionic surfactants or anionic surfactants; the nonionic surfactant includes one or more of fatty alcohol polyoxyethylene ether (AEO-9), alkylphenol polyoxyethylene ether (OP-10), or polyethylene glycol octylphenyl ether (Triton X-100); the anionic surfactant includes one or more of sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS), or sodium polyacrylate (PAAS); preferably, the nonionic surfactant AEO-9.

6. The GOI weakly alkaline cerium oxide polishing slurry according to claim 1, characterized in that, The oxidant is selected from one or more of hydrogen peroxide, peracetic acid, potassium iodate, or potassium permanganate, preferably hydrogen peroxide, with a concentration of 0.3%-1.5%.

7. The GOI weakly alkaline cerium oxide polishing slurry according to claim 1, characterized in that, The selective inhibitor is selected from one or more of benzotriazole (BTA), 2-mercaptobenzothiazole (MBT), polyethylene glycol (PEG) or polyvinylpyrrolidone (PVP), preferably benzotriazole (BTA) or 2-mercaptobenzothiazole (MBT).

8. A method for preparing the GOI weakly alkaline cerium oxide polishing slurry as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Disperse nano-cerium oxide powder in deionized water, add carboxylic acid, phosphoric acid or sulfonic acid modifiers, adjust the pH to 8.5-9.0 with ammonia or TMAH, reflux and stir at 60-80℃ for 4-8 hours, centrifuge, wash and dry to obtain surface-modified nano-cerium oxide abrasive. S2. Disperse the surface-modified nano-cerium oxide abrasive obtained in S1 in deionized water according to the specified ratio, and ultrasonically treat for 20-30 minutes. S3. Under stirring conditions, add the dispersant stabilizer, oxidant and selective inhibitor in sequence, and continue stirring for 15-20 minutes; S4. Adjust the pH of the mixture to 8.0-10.0, preferably 8.5-9.5, using a weakly alkaline pH adjuster; S5. Filter the resulting mixture through a 0.2 μm filter membrane.

9. The method for preparing the GOI weakly alkaline cerium oxide polishing slurry according to claim 8, characterized in that, The amount of modifier used in step S1 is 1%-5% of the mass of nano-cerium oxide powder, preferably 2%-4%; the modification reaction is carried out in a deionized water system without the need for organic solvents.

10. The application of the GOI weakly alkaline cerium oxide polishing slurry according to any one of claims 1-7 in the fine polishing of germanium substrates on insulators, characterized in that, The fine polishing is performed after mechanical rough polishing. During the polishing process, the removal rate of the germanium layer is 100-140 nm / min, the Ge / SiO2 selectivity ratio is ≥ 70:1, the surface roughness RMS after fine polishing is ≤ 0.25 nm, the 48-hour settling rate is ≤ 5%, and the buried oxide layer is intact and free from corrosion.

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