Acid polishing solution for dielectric layer as well as preparation method and application of acid polishing solution

Abstract

The invention provides an acidic polishing solution for a dielectric layer and a preparation method and application of the acidic polishing solution. The polishing solution is prepared from, by mass, 5%-30% of silicon oxide abrasive, 0.01%-1% of modifier, 0.01%-1% of surfactant and the balance pH regulator and water, and the pH value of the polishing solution is 2-3.5 through the pH regulator; the modifier is organic ammonium salt and / or organic amine, and the surfactant is alkyl sulphobetaine. The polishing rate and the polishing quality of the polishing solution can be improved through the cooperation of the modifier and the surfactant.

Description

Technical Field

[0001] This invention relates to the field of polishing fluid technology, and in particular to an acidic polishing fluid for use in a dielectric layer, its preparation method, and its applications. Background Technology

[0002] Currently, the key insulating isolation technology for device isolation in IC manufacturing is shallow trench isolation. Its core process involves patterning a silicon substrate using a silicon nitride mask to form shallow trenches, then filling these trenches with a silicon dioxide dielectric layer to achieve electrical isolation between components. Finally, chemical mechanical polishing (CMP) is used to planarize the surface. This process requires a very high silicon dioxide removal rate and extremely low surface defect rates, both of which directly determine the efficiency of device isolation.

[0003] Traditional silica sol-based spherical abrasive particles used in dielectric layer polishing slurries have low polishing efficiency for silica materials. To improve the masking efficiency of these slurries, the morphology of the silica sol particles is often modified to create cocoon-shaped, curved, or popcorn-shaped particles with multiple edges. However, due to the angular shape of the abrasive particles, scratches are inevitably generated during CMP polishing, making it difficult to meet the polishing requirements of advanced processes. As integrated circuit technology nodes move towards smaller dimensions, higher polishing rates and lower polishing defects are required for silica dielectric layer polishing.

[0004] Chinese patent CN119709023A proposes a method using 2,2'[[((methyl1H-benzotriazolyl)methyl]imino]diethanol (TTLYK) and octylhydroxamic acid (OHA) as inhibitors. The two agents, acting alone or in combination, work synergistically with a complexing agent to achieve a high polishing rate and good surface quality in the polishing slurry. However, this polishing method requires the use of hydrogen peroxide as an oxidant, which is a hazardous chemical, posing certain requirements for industrial production. Chinese patent CN120248831A proposes a modification method using a silane coupling agent and surfactant to modify cerium dioxide abrasive grains, which can improve the polishing rate of the media layer. However, this modification method generates alcohols such as methanol and ethanol during the modification process. Without distillation of these alcohols, the polishing rate of the polishing slurry will be significantly affected. Furthermore, this modification method requires multiple preparation steps, including heating, distillation, and ultrasonication, making large-scale industrialization difficult. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide an acidic polishing slurry for a dielectric layer, its preparation method and application, to solve the problems of low polishing rate, numerous surface defects of the polished material, and complex abrasive modification methods in the prior art, which make it difficult to achieve large-scale production.

[0006] To achieve the above and other related objectives, the present invention provides an acidic polishing slurry for a dielectric layer, a method for preparing the slurry, and its uses.

[0007] The first aspect of the present invention provides an acidic polishing slurry for a dielectric layer, the polishing slurry comprising the following components in the following mass fractions: 5 wt% to 30 wt% silica abrasive, 0.01 wt% to 1 wt% modifier, 0.01 wt% to 1 wt% surfactant, and the balance being a pH adjuster and water, wherein the pH adjuster makes the pH value of the polishing slurry 2 to 3.5; the modifier is an organic ammonium salt and / or an organic amine, and the surfactant is an alkyl sulfobetaine.

[0008] The mass fraction is the percentage of each component relative to the total mass of the polishing slurry, based on the total mass of the polishing slurry.

[0009] The polishing liquid product of this invention can be diluted according to actual needs in actual use. It can usually be diluted to 2 to 10 times for polishing; for example, it can be 2 times, 2.5 times, 3 times, 3.5 times, 4 times, 4.5 times, 5 times, 5.5 times, 6 times, 6.5 times, 7 times, 7.5 times, 8 times, 8.5 times, and 9 times.

[0010] Preferably, the pH of the polishing solution is 2.5 to 3.5.

[0011] More preferably, the pH of the polishing solution is 2.5 to 3.

[0012] Considering polishing rate, surface quality and production cost, preferably, the mass fraction of the abrasive is 10wt% to 20wt%; for example, it can be 10wt%, 12wt%, 15wt%, 18wt%, or 20wt%.

[0013] Considering the polishing rate and surface quality, preferably, the mass fraction of the modifier is 0.04wt%~1wt%; for example, it can be 0.04wt%, 0.05wt%, 0.08wt%, 0.1wt%, 0.2wt%, 0.4wt%, 0.5wt%, 0.8wt%, or 1wt%.

[0014] More preferably, the mass fraction of the modifier is 0.04wt% to 0.1wt%.

[0015] Considering polishing rate, surface quality and dispersibility, preferably, the mass fraction of the surfactant is 0.01wt% to 0.1wt%; for example, it can be 0.01wt%, 0.02wt%, 0.04wt%, 0.05wt%, 0.08wt%, or 0.1wt%.

[0016] Preferably, the modifier is any one or more selected from tetrabutylammonium hydroxide, tetrapropylammonium hydroxide, dihexenetriamine, trihexylamine, dicyclohexylamine, spermine, and spermidine.

[0017] Preferably, the modifier is any one or more selected from tetrabutylammonium hydroxide, tetrapropylammonium hydroxide, dihexenetriamine, and dicyclohexylamine.

[0018] More preferably, the modifier is any one or more of tetrabutylammonium hydroxide, dihexenetriamine, and dicyclohexylamine.

[0019] Preferably, the alkyl group in the alkyl sulfonate betaine is a straight-chain alkyl group with ≥8 carbon atoms.

[0020] Preferably, the surfactant is selected from any one or more of thiobetaine 8, thiobetaine 10, thiobetaine 12, octadecyl sulfobetaine, lauroylpropyl hydroxysulfonate betaine, and cocamidohydroxysulfonate.

[0021] Preferably, the silicon oxide is selected from any one or two of spherical silicon oxide and curved silicon oxide.

[0022] The polishing rate of spherical silicon oxide is slightly lower than that of curved silicon oxide, but the surface quality of the wafer after polishing is slightly higher than that of curved silicon oxide.

[0023] Preferably, the silicon oxide has a particle size of 30~100nm; for example, it can be 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, or 100nm.

[0024] Preferably, the pH adjuster is selected from any one or more of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and acetic acid.

[0025] More preferably, the pH adjuster is nitric acid.

[0026] Preferably, the above-mentioned polishing slurry is diluted 7.5 times, and under the conditions of polishing pressure of 2.8 psi, polishing speed of upper / lower disk of 45 / 55 rpm, flow rate of 300 mL / min, and polishing temperature of 25℃, the polishing rate of the diluted polishing slurry on silicon oxide wafer is ≥2300 Å / min.

[0027] More preferably, the above-mentioned polishing slurry is diluted 7.5 times, and under the conditions of polishing pressure of 2.8 psi, polishing speed of upper / lower disk of 45 / 55 rpm, flow rate of 300 mL / min, and polishing temperature of 25℃, the polishing rate of the diluted polishing slurry on silicon oxide wafer is ≥2300~3000 Å / min; for example, it can be 2300 Å / min, 2400 Å / min, 2500 Å / min, 2600 Å / min, 2700 Å / min, 2800 Å / min, 2900 Å / min, or 3000 Å / min.

[0028] Preferably, the above-mentioned polishing slurry is diluted 7.5 times. Under the conditions of polishing pressure of 2.8 psi, polishing speed of upper / lower disk of 45 / 55 rpm, flow rate of 300 mL / min, and polishing temperature of 25℃, the surface roughness Ra of the silicon oxide wafer after polishing by the diluted polishing slurry is ≤0.15nm.

[0029] More preferably, the above-mentioned polishing slurry is diluted 7.5 times, and under the conditions of polishing pressure of 2.8 psi, polishing upper / lower disk rotation speed of 45 / 55 rpm, flow rate of 300 mL / min, and polishing temperature of 25℃, the surface roughness Ra of the silicon oxide wafer after polishing by the diluted polishing slurry is 0.1~0.15 nm; for example, it can be 0.1 nm, 0.11 nm, 0.12 nm, 0.13 nm, 0.14 nm, or 0.15 nm.

[0030] A second aspect of the present invention provides a method for preparing a polishing slurry, the method comprising mixing and stirring a portion of water, abrasive and surfactant, adjusting the pH of the solution to 2-3.5 to obtain solution A; mixing and stirring the remaining water, abrasive and modifier, adjusting the pH of the solution to 2-3.5 to obtain solution B; and mixing solution A and solution B to obtain the polishing slurry.

[0031] The applicant explored the preparation method of polishing slurry and found that directly mixing and stirring the abrasive, water, modifier and surfactant together, or directly mixing and stirring water, abrasive and one of the modifier or surfactant, and then adding the other and mixing, will cause the abrasive to agglomerate and form gel, affecting the stability of the polishing slurry; only by using the above-mentioned mixing method of liquid A and liquid B can the stability of the polishing slurry be guaranteed.

[0032] Preferably, the stirring rate during the preparation of liquid A and liquid B is 100~300 r / min; for example, it can be 100 r / min, 200 r / min, or 300 r / min.

[0033] Preferably, the stirring time during the preparation of liquid A and liquid B is 10 to 30 minutes; for example, it can be 10 minutes, 20 minutes, or 30 minutes.

[0034] A third aspect of the present invention provides an application of the above-mentioned polishing slurry in the polishing of silicon oxide dielectric layers.

[0035] A fourth aspect of the present invention provides the use of an organic ammonium salt and / or an organic amine in synergy with an alkyl sulfobetaine in improving the polishing rate of a polishing slurry.

[0036] Preferably, the purpose is to improve the polishing rate of the polishing slurry on the silicon oxide dielectric layer.

[0037] The fifth aspect of the present invention provides the use of an organic ammonium salt and / or an organic amine in synergy with an alkyl sulfobetaine in reducing the surface roughness of a polished silicon oxide wafer.

[0038] As described above, the acidic polishing slurry for a dielectric layer, its preparation method, and its uses according to the present invention have the following beneficial effects:

[0039] This invention provides a surface modification method for silica abrasives using organic ammonium salts or organic amines as modifiers and betaine derivatives as surfactants. This method significantly improves the Zeta potential of silica abrasives under acidic conditions. The polishing slurry formulation of this invention is simple, requiring no additional oxidants, complexing agents, polymers, or other components. Only silica, modifiers, and surfactants are needed to form a stable acidic polishing slurry system, effectively improving the polishing rate and quality of the silica dielectric layer. Detailed Implementation

[0040] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0041] It should be noted that the process equipment or apparatus not specifically specified in the following embodiments are all conventional equipment or apparatus in the art. Furthermore, it should be understood that one or more method steps mentioned in this invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0042] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention; in the specification and claims of the present invention, unless otherwise expressly stated in the text, the singular forms "a", "an" and "this" include the plural forms.

[0043] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0044] This invention provides a simple acidic polishing slurry for silicon oxide dielectric layers. A special sulfonic acid betaine derivative with long carbon chains is adsorbed onto the surface of the silicon oxide abrasive. The long carbon chains provide steric hindrance, preventing agglomeration of the abrasive particles and improving their dispersibility. An organic ammonium salt or organic amine modifier promotes the adsorption of the silicon oxide abrasive onto the wafer surface, increasing the zeta potential. Positive charges adsorb onto the surface of the silicon oxide dielectric layer to be polished, improving abrasive dispersion and resulting in a larger contact area with the wafer surface. This further enhances the polishing rate and quality. By optimizing the ratio of these two components, the polishing slurry can achieve a polishing rate of 2300 Å / min on silicon oxide dielectric layers, with a post-polishing surface roughness ≤0.15 nm.

[0045] The silica particle size range used in the following embodiments of this application is 30~100nm, and the mass fraction of silica sol dispersed in water is 20wt%.

[0046] Example 1

[0047] This embodiment 1 provides a specific polishing fluid, which, based on the total mass of the polishing fluid, has the following specific composition: 15wt% curved silica abrasive, 0.1wt% organic ammonium salt (tetrabutylammonium hydroxide), 0.1wt% surfactant (thiobetaine 12), and the balance being pH adjuster and water. The pH adjuster is nitric acid, used to adjust the pH of the polishing fluid to 2.5.

[0048] The specific preparation method of this polishing slurry is as follows:

[0049] S1. Add water, abrasive, and surfactant to a clean reactor A according to the specified ratio, start stirring at 200 r / min for 30 min.

[0050] S2. Add nitric acid, stir for 30 minutes, and adjust the pH of the solution to 2.5.

[0051] S3. Add water, modifier, and nitric acid to a clean reactor B according to the specified ratio, start stirring at 200 r / min for 30 min, and adjust the pH of the solution to 2.5.

[0052] S4. Add the solution from reactor A to reactor B, start stirring at 200 r / min for 30 min.

[0053] S5. After passing through a 5µm filter element for primary filtration and a 0.1µm filter element for secondary filtration, the polishing liquid is filled to obtain the polishing liquid.

[0054] Example 2

[0055] Example 2 provides a specific polishing liquid and its preparation method. The difference between Example 1 and Example 2 is that the amount of tetrabutylammonium hydroxide added is reduced to 0.04wt%, and thiobetaine 12 is replaced with octadecyl betaine; the remaining components and preparation methods are the same as in Example 1.

[0056] Example 3

[0057] This embodiment 3 provides a specific polishing liquid and its preparation method. The difference between this embodiment and embodiment 1 is that the amount of tetrabutylammonium hydroxide added is increased to 0.5wt%, and thiobetaine 12 is replaced with lauroylpropyl hydroxysulfonate betaine; the remaining components and preparation methods are the same as in embodiment 1.

[0058] Example 4

[0059] This embodiment 4 provides a specific polishing liquid and its preparation method, which differs from that of embodiment 1 in that the amount of tetrabutylammonium hydroxide added is increased to 1 wt%; the remaining components and preparation methods are the same as those in embodiment 1.

[0060] Example 5

[0061] This embodiment 5 provides a specific polishing liquid and its preparation method, which differs from embodiment 1 in that the amount of silicon oxide added is reduced to 10 wt%; the remaining components and preparation method are the same as in embodiment 1.

[0062] Example 6

[0063] This embodiment 6 provides a specific polishing liquid and its preparation method, which differs from embodiment 1 in that the amount of silicon oxide added is increased to 20 wt%; the remaining components and preparation method are the same as in embodiment 1.

[0064] Example 7

[0065] This embodiment 7 provides a specific polishing liquid and its preparation method, which differs from that of embodiment 1 in that the amount of thiobetaine 12 added is increased to 1 wt%; the remaining components and preparation methods are the same as those in embodiment 1.

[0066] Example 8

[0067] This embodiment 8 provides a specific polishing liquid and its preparation method, which differs from that of embodiment 1 in that the amount of thiobetaine 12 added is reduced to 0.01 wt%; the remaining components and preparation methods are the same as those in embodiment 1.

[0068] Example 9

[0069] This Example 9 provides a specific polishing liquid and its preparation method, which differs from Example 1 in that: tetrabutylammonium hydroxide is replaced with dihexenetriamine; the remaining components and preparation methods are the same as in Example 1.

[0070] Example 10

[0071] This embodiment 10 provides a specific polishing liquid and its preparation method, which differs from embodiment 1 in that: the curved silicon oxide is replaced with spherical silicon oxide; the remaining components and preparation methods are the same as in embodiment 1.

[0072] Example 11

[0073] This embodiment 11 provides a specific polishing liquid and its preparation method, which differs from embodiment 1 in that the pH of the polishing liquid is adjusted to 3.5; the remaining components and preparation methods are the same as in embodiment 1.

[0074] Comparative Example 1

[0075] Comparative Example 1 provides a specific polishing solution and its preparation method, which differs from Example 1 in that tetrabutylammonium hydroxide is not added; the remaining components are the same as in Example 1. The preparation method is as follows:

[0076] S1. Add water, abrasive, and surfactant to a clean reactor according to the specified ratio, start stirring at 200 r / min for 30 min.

[0077] S2. Add nitric acid, stir for 30 minutes, and adjust the pH of the solution to 2.5.

[0078] S3. After passing through a 5µm filter element for primary filtration and a 0.1µm filter element for secondary filtration, the polishing liquid is filled to obtain the polishing liquid.

[0079] Comparative Example 2

[0080] Comparative Example 2 provides a specific polishing solution and its preparation method, which differs from Example 1 in that: tetrabutylammonium hydroxide and thiobetaine 12 are not added, and the curved silica is replaced with spherical silica; the amount of silica added is the same as in Example 1. The preparation method is as follows:

[0081] S1. Add water and abrasive to a clean reactor according to the ratio, start stirring at 200 r / min for 30 min.

[0082] S2. Add nitric acid, stir for 30 minutes, and adjust the pH of the solution to 2.5.

[0083] S3. After passing through a 5µm filter element for primary filtration and a 0.1µm filter element for secondary filtration, the polishing liquid is filled to obtain the polishing liquid.

[0084] Comparative Example 3

[0085] Comparative Example 3 provides a specific polishing solution and its preparation method, which differs from Example 1 in that: thiobetaine 12 is not added; the remaining components and preparation method are the same as in Example 1. The preparation method is as follows:

[0086] S1. Add water, abrasive, and modifier to a clean reactor according to the specified ratio, start stirring at 200 r / min for 30 min.

[0087] S2. Add nitric acid, stir for 30 minutes, and adjust the pH of the solution to 2.5.

[0088] S3. After passing through a 5µm filter element for primary filtration and a 0.1µm filter element for secondary filtration, the polishing liquid is filled to obtain the polishing liquid.

[0089] Comparative Example 4

[0090] Comparative Example 4 provides a specific polishing liquid and its preparation method. The difference between this and Example 1 is that thiobetaine 12 is replaced with sodium hexametaphosphate; the remaining components and preparation methods are the same as in Example 1.

[0091] Comparative Example 5

[0092] Comparative Example 5 provides a specific polishing liquid and its preparation method, which differs from Example 1 in that: thiobetaine 12 is replaced with fatty alcohol polyoxyethylene ether; the remaining components and preparation methods are the same as in Example 1.

[0093] Comparative Example 6

[0094] Comparative Example 6 provides a specific polishing liquid and its preparation method, which differs from Example 1 in that the amount of thiobetaine 12 added is reduced to 0.0001 wt%; the remaining components and preparation methods are the same as in Example 1.

[0095] Comparative Example 7

[0096] Comparative Example 7 provides a specific polishing liquid and its preparation method, which differs from Example 1 in that the amount of thiobetaine 12 added is increased to 5 wt%; the remaining components and preparation methods are the same as in Example 1.

[0097] Comparative Example 8

[0098] Comparative Example 8 provides a specific polishing liquid and its preparation method, which differs from Example 1 in that the amount of tetrabutylammonium hydroxide added is reduced to 0.0001 wt%; the remaining components and preparation methods are the same as in Example 1.

[0099] Comparative Example 9

[0100] Comparative Example 9 provides a specific polishing liquid and its preparation method, which differs from Example 1 in that the amount of tetrabutylammonium hydroxide added is increased to 5 wt%; the remaining components and preparation methods are the same as in Example 1.

[0101] Comparative Example 10

[0102] Comparative Example 10 provides a specific polishing liquid and its preparation method, which differs from Example 1 in that the pH is adjusted to 4; the remaining components and preparation methods are the same as in Example 1.

[0103] Comparative Example 11

[0104] Comparative Example 11 provides a specific amino-modified silica polishing slurry and its preparation method. Based on the total mass of the polishing slurry, its specific composition is as follows: 15wt% curved silica abrasive, 0.2wt% silane coupling agent KH550, 0.05wt% citric acid, and the balance being pH adjuster and water. The pH adjuster is nitric acid, used to adjust the pH of the polishing slurry to 2.5.

[0105] The specific preparation method of this polishing slurry is as follows:

[0106] S1. Add water to a clean reactor according to the formula and start stirring at 200 r / min. Add silica sol according to the formula and maintain stirring for 10 min.

[0107] S2. Slowly add the aminosilane coupling agent according to the ratio and continue stirring for 5 hours.

[0108] S3. Adjust the pH of the polishing solution to 2.5 and continue stirring for 30 minutes.

[0109] S4. Add citric acid according to the ratio and continue stirring for 10 minutes.

[0110] S5. After passing through a 5µm filter element for primary filtration and a 0.1µm filter element for secondary filtration, the polishing liquid is filled to obtain the polishing liquid.

[0111] Table 1. Formulation composition of polishing slurries in Examples 1-10 and Comparative Examples 1-10

[0112]

[0113]

[0114] Test section

[0115] The performance of the polishing slurries prepared in the above embodiments and comparative examples was tested. The specific test methods are as follows:

[0116] 1) Polishing Rate Test: The specific process conditions were as follows: the polishing object was a 12-inch diameter TEOS wafer with a thickness of 8000 Å; the polishing pad was a WH6000 polishing pad; the polishing disk diameter was 762 mm; the polishing pressure was 2.8 psi; the upper / lower disk rotation speeds were 45 / 55 rpm; the polishing slurry was diluted 7.5 times; the flow rate was 300 mL / min; and the polishing time was 30 s. The polishing temperature was 25℃. The polishing rate was measured using a KLA non-metallic film thickness gauge (F50). Specifically, the thickness of the single-crystal silicon wafer was measured before and after polishing. The polishing rate was calculated by dividing the difference in film thickness before and after polishing by the polishing time. The test results are shown in Table 2.

[0117] 2) Surface roughness: The surface roughness was tested using an atomic force microscope. The test area at each location was 10μm*10μm. The average roughness of the three locations was calculated, and the results are shown in Table 2.

[0118] 3) Zeta potential: Each sample was diluted 7.5 times before testing using a nanoparticle zeta potential analyzer. The results are shown in Table 2.

[0119] 4) TSI Index (Stability Coefficient): The stability analyzer was used for testing. Each sample was kept at a temperature of 30 min and the TSI index was measured after 24 h. If the index ≤ 1, the polishing solution is considered to have high stability. If the index > 1 and < 1.5, the polishing solution is considered to have medium stability. If the index ≥ 1.5, the polishing solution is considered to have low stability. The results are shown in Table 2.

[0120] 5) Degree of dispersion of polishing slurry: After 3 months of storage, observe the sedimentation state of the particles in the transparent container with the naked eye; if the polishing slurry is still a uniform turbid suspension and does not separate into layers in the following 9 months, the polishing slurry is highly dispersed; if the polishing slurry is in a gel state and becomes a uniform turbid suspension after shaking, the polishing slurry is moderately dispersed; if it cannot be shaken, the polishing slurry is poorly dispersed. The results are shown in Table 2.

[0121] Table 2. Polishing slurry performance test results

[0122]

[0123] According to the results in Table 2, compared with Comparative Examples 1 to 11, the TSI index of the polishing liquid in Examples 1 to 11 is ≤1, indicating a highly dispersed state. The polishing rate is >2300 Å / min, and the surface roughness Ra is ≤0.15. It can simultaneously achieve both high polishing rate and surface quality.

[0124] In Comparative Example 1, the polishing rate and Zeta potential were significantly reduced without the addition of a modifier. The repulsive force between abrasive grains weakened, leading to abrasive grain aggregation and reduced dispersibility of the polishing slurry and surface quality of the polished wafer. In Comparative Example 2, the absence of both a modifier and surfactant resulted in a further decrease in Zeta potential compared to Comparative Example 1, with even lower dispersibility and a further increase in the surface roughness Ra of the polished wafer. In Comparative Example 3, the addition of only a modifier caused the surface charge of the silica abrasive to change from negative to positive during the pH adjustment of the polishing slurry. This process caused abrasive aggregation. Tetrabutylammonium hydroxide, being positively charged, accelerated the charge conversion on the abrasive surface, leading to accelerated aggregation and flocculation, resulting in a sharp decrease in dispersibility and rendering polishing impossible. In Comparative Example 4, sodium hexametaphosphate was used as a surfactant, but it hydrolyzes under strong acid conditions, failing to promote dispersion and resulting in poor abrasive dispersibility and reduced surface quality of the polished wafer. In Comparative Example 5, fatty alcohol polyoxyethylene ether was used as a surfactant, but it failed to provide adequate dispersion. The surfactant itself has viscosity and will adsorb at the polishing interface to form a hydration film, hindering the polishing reaction; in Comparative Example 6, the amount of surfactant added was too low, failing to achieve a good dispersion effect, resulting in a decrease in the surface quality of the wafer after polishing; in Comparative Example 7, the amount of surfactant added was too high, and excessive thiobetaine 12 would crowd out the active sites of the modifier, leading to a decrease in the zeta potential, and at the same time, it would generate a large amount of foam during polishing, resulting in a decrease in the polishing rate; in Comparative Example 8, the amount of modifier added was too low, and the polishing rate was lower compared to Comparative Example 1 without modifier. The Zeta potential was only slightly increased; in Comparative Example 9, the amount of modifier added was too large, and the excess modifier would be free in the polishing slurry, causing wafer surface corrosion and resulting in a decrease in surface roughness Ra; in Comparative Example 10, the pH of the polishing slurry increased, approaching the isoelectric point of the curved silicon oxide abrasive, and the silicon oxide was in a metastable state. After the addition of organic ammonium salt, the rapid change in potential would produce gel, making polishing impossible; in Comparative Example 11, the silicon oxide polishing slurry modified with silane coupling agent had a lower polishing rate compared with the polishing slurry prepared in the embodiments of this application.

[0125] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. An acidic polishing slurry for use in a dielectric layer, characterized in that, The polishing slurry comprises the following components in the following mass fractions: 5wt%~30wt% silica abrasive, 0.01wt%~1wt% modifier, 0.01wt%~1wt% surfactant, and the balance being pH adjuster and water, wherein the pH adjuster makes the pH value of the polishing slurry 2~3.5; the modifier is an organic ammonium salt and / or an organic amine, and the surfactant is alkyl sulfobetaine.

2. The polishing slurry according to claim 1, characterized in that, The modifier is selected from any one or more of tetrabutylammonium hydroxide, tetrapropylammonium hydroxide, dihexenetriamine, trihexylamine, dicyclohexylamine, spermine, and spermidine.

3. The polishing slurry according to claim 1, characterized in that, The surfactant is selected from any one or more of thiobetaine 8, thiobetaine 10, thiobetaine 12, octadecyl sulfobetaine, lauroylpropyl hydroxysulfonate betaine, and cocamidohydroxysulfonate betaine.

4. The polishing slurry according to claim 1, characterized in that, The silicon oxide abrasive is selected from any one or two of spherical silicon oxide and curved silicon oxide; And / or, the particle size of the silicon oxide is 30~100nm.

5. The polishing slurry according to claim 1, characterized in that, The pH adjuster is selected from any one or more of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and acetic acid.

6. A method for preparing a polishing slurry as described in any one of claims 1 to 5, characterized in that, The method includes mixing and stirring a portion of water, abrasive, and surfactant, adjusting the pH of the solution to 2-3.5 to obtain solution A; mixing and stirring the remaining water, abrasive, and modifier, adjusting the pH of the solution to 2-3.5 to obtain solution B; and mixing solution A and solution B to obtain the polishing liquid.

7. The preparation method according to claim 6, characterized in that, The stirring rate during the preparation of liquid A and liquid B is 100~300 r / min; And / or, the stirring time during the preparation of liquid A and liquid B is 10~30 min.

8. The application of a polishing slurry as described in any one of claims 1 to 5 in the polishing of a silicon oxide dielectric layer.

9. The use of organic ammonium salts and / or organic amines in synergy with alkyl sulfobetaine in increasing the polishing rate of polishing slurries and / or reducing the surface roughness of silicon oxide wafers after polishing.

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