Chemical mechanical polishing slurry

Abstract

In the present invention, nanometer cerium oxide is used as an abrasive, and the particle size thereof determined by dynamic light scattering is 1-30 nm, which is beneficial for reducing scratches during chemical mechanical polishing. By selecting a proper additive, the removal rates of silicon oxide, silicon nitride and polysilicon are adjusted and controlled. The selection ratio of the removal rate of silicon oxide to the removal rate of silicon nitride can be adjusted and controlled in the range of 2:1 to 3500:1, and the selection ratio of the removal rate of silicon oxide to the removal rate of polysilicon can be adjusted and controlled in the range of 2:1 to 3500:1.

Description

A chemical mechanical polishing fluid Technical Field

[0001] This invention relates to a chemical mechanical polishing slurry, and more particularly to a polishing slurry for removing silicon oxide films and for effectively stopping on silicon nitride or polycrystalline silicon films. Background Technology

[0002] In the chemical mechanical planarization (CMP) process, in order to reduce the damage caused by grinding, smaller abrasive particles can be selected as abrasives. However, the reduction in the particle size of abrasive particles will lead to a significant decrease in the polishing rate, which cannot meet the actual application requirements.

[0003] Traditional cerium oxide particles have a dynamic light scattering particle size of 100-200nm. Due to the relatively large particle size, the polishing film is easily damaged during chemical mechanical polishing, resulting in a decrease in chip yield.

[0004] Therefore, as a method to reduce grinding damage, the industry has proposed reducing the average particle size of the grinding particles in the polishing flux. With the miniaturization of semiconductor devices, in addition to grinding damage, insufficient planarization efficiency and insufficient grinding selectivity have also become significant challenges in CMP processes.

[0005] Besides the polishing rate, the difference in removal rate of different films by the polishing slurry also affects its application range. Different applications usually require polishing slurries with different selectivity ratios. For the layer to be removed, a higher polishing rate is generally better, while for the stop layer, a lower removal rate is generally better. In other words, the higher the selectivity ratio of the layer to be removed to the stop layer, the better. Typically, silicon nitride or polycrystalline silicon films are used as stop layers.

[0006] Existing cerium oxide polishing slurries typically only involve two types of films being polished, such as removing silicon oxide film and stopping at the surface of silicon nitride film, or removing silicon oxide film and stopping at the surface of polycrystalline silicon film. With the development of semiconductor manufacturing processes, some special application requirements are also increasing, such as removing silicon oxide film while simultaneously removing silicon nitride film and stopping at the surface of polycrystalline silicon film; or removing silicon oxide film and stopping at both the surface of silicon nitride film and the surface of polycrystalline silicon film.

[0007] As the particle size of cerium oxide decreases, the particles adhere more easily to the surfaces of silicon oxide films, silicon nitride films, and polycrystalline silicon films. In addition, the polishing rate of cerium oxide is closely related to its average particle size. As the particle size of cerium oxide decreases, the polishing rate also gradually decreases. Nano-cerium oxide particles often exhibit a low polishing rate and cannot be used in practical applications. Summary of the Invention

[0008] In view of the above background, the object of the present invention is to provide a nano-cerium oxide-based polishing slurry with extremely small particle size. Furthermore, the polishing slurry provided by the present invention can remove silicon oxide films at high speed (or simultaneously have a certain silicon nitride removal rate) and can effectively stop on silicon nitride or polycrystalline silicon films. The present invention provides an abrasive that can reduce damage to the polished film and has high planarization efficiency and a specific selectivity during chemical mechanical polishing. The present invention provides a series of dispersion methods that make it difficult for particles to adhere to the surface of the polished film, which is beneficial for reducing polishing defects.

[0009] This invention discloses a chemical mechanical polishing fluid comprising: nano-cerium oxide particles, polyethylene glycol, and polyquaternary ammonium salt.

[0010] Furthermore, the polishing fluid also includes polyaminopolysaccharides.

[0011] Further, the polyquaternium salt is polyquaternium salt-6, polyquaternium salt-7, polyquaternium salt-11, polyquaternium salt-28, or polyquaternium salt-37.

[0012] Furthermore, the polyaminopolysaccharide is chitosan and chitosan derivatives.

[0013] Furthermore, the content of the nano-cerium oxide particles is 0.005 wt% to 5 wt%.

[0014] Furthermore, the content of the polyquaternary ammonium salt is 0.0005 wt% to 0.1 wt%.

[0015] Furthermore, the content of the polyaminopolysaccharide is 0.0005 wt% to 0.1 wt%.

[0016] Furthermore, the molecular weight of the polyethylene glycol is in the range of 400-500,000.

[0017] Furthermore, the content of the polyethylene glycol is 0.01 wt% to 5 wt%.

[0018] Furthermore, the pH of the polishing solution is 3.0 to 7.0.

[0019] This invention uses nano-cerium oxide as an abrasive, with a dynamic light-scattering particle size of 1-30 nm, which helps reduce scratches caused by chemical mechanical processes. The removal rates of silicon oxide, silicon nitride, and polycrystalline silicon can be controlled by selecting appropriate additives. Specifically, the selectivity ratio of silicon oxide removal rate to silicon nitride removal rate can be controlled within the range of 2:1 to 3500:1, and the ratio of silicon oxide removal rate to polycrystalline silicon removal rate can also be controlled within the range of 2:1 to 3500:1. Detailed Implementation

[0020] The advantages of the present invention will be further illustrated below with reference to specific embodiments.

[0021] Example 1

[0022] Add 30g of 50% PEG600, 1.5g of 2% PQ7 aqueous solution and 6g of 1% m-aminobenzenesulfonic acid aqueous solution to 2887g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0023] Example 2

[0024] Add 30g of 50% PEG600, 4.5g of 2% PQ7 aqueous solution and 6g of 1% m-aminobenzenesulfonic acid aqueous solution to 2885g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0025] Example 3

[0026] Add 30g of 50% PEG800, 4.5g of 2% PQ7 aqueous solution and 6g of 1% m-aminobenzenesulfonic acid aqueous solution to 2885g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0027] Example 4

[0028] Add 30g of 50% PEG10000, 4.5g of 2% PQ7 aqueous solution and 6g of 1% m-aminobenzenesulfonic acid aqueous solution to 2885g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0029] Example 5

[0030] Add 30g of 50% PEG600, 4.5g of 2% PQ7 aqueous solution and 6g of 1% m-aminobenzenesulfonic acid aqueous solution to 2885g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 4.0.

[0031] Example 6

[0032] Add 30g of 50% PEG600, 4.5g of 2% PQ7 aqueous solution and 6g of 1% m-aminobenzenesulfonic acid aqueous solution to 2885g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 5.0.

[0033] Example 7

[0034] Add 30g of 50% PEG600, 4.5g of 2% PQ7 aqueous solution and 6g of 1% m-aminobenzenesulfonic acid aqueous solution to 2885g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 7.0.

[0035] Example 8

[0036] Add 12g of 50% PEG600, 1.5g of 2% PQ7 aqueous solution and 30g of 1% chitosan M aqueous solution to 2882g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0037] Example 9

[0038] Add 9g of 1% m-aminobenzenesulfonic acid, 1.5g of 2% PQ7 aqueous solution, 30g of 1% chitosan S aqueous solution, and 12g of 50% PEG600 to 2882g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0039] Example 10

[0040] Add 3.0g of 2% PQ7 aqueous solution, 30g of 1% chitosan S aqueous solution, and 12g of 50% PEG600 to 2882g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0041] Example 11

[0042] Add 30g of 1% chitosan S aqueous solution and 12g of 50% PEG600 to 2883g of deionized water, stir well, then add 75g of 2% nano-cerium oxide dispersion, and add imidazole to adjust the pH of the grinding solution to 6.0.

[0043] Example 12

[0044] Add 9g of 1% p-aminobenzenesulfonic acid, 3g of 2% PQ7 aqueous solution, 60g of 1% chitosan M aqueous solution, and 12g of 50% PEG600 to 2841g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0045] Example 13

[0046] Add 9g of 1% p-aminobenzenesulfonic acid, 3g of 2% PQ7 aqueous solution, 15g of 1% chitosan S aqueous solution, and 12g of 50% PEG600 to 2886g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0047] Example 14

[0048] Add 9g of 1% p-aminobenzenesulfonic acid, 3g of 2% PQ7 aqueous solution, 22.5g of 1% chitosan S aqueous solution, and 12g of 50% PEG600 to 2879g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0049] Example 15

[0050] Add 3g of 2% PQ7 aqueous solution, 60g of 1% chitosan S aqueous solution, and 12g of 50% PEG600 to 2841g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0051] Example 16

[0052] Add 6g of 1% m-aminobenzenesulfonic acid, 3g of 2% PQ7 aqueous solution, 15g of 1% chitosan M aqueous solution, and 12g of 50% PEG600 to 2887g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0053] Example 17

[0054] Add 6g of 1% m-aminobenzenesulfonic acid, 1.5g of 2% PQ6 aqueous solution and 30g of 50% PEG600 to 2887g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0055] Example 18

[0056] Add 6g of 1% m-aminobenzenesulfonic acid, 1.5g of 2% PQ11 aqueous solution and 30g of 50% PEG600 to 2887g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0057] Example 19

[0058] Add 6g of 1% m-aminobenzenesulfonic acid, 1.5g of 2% PQ28 aqueous solution and 30g of 50% PEG600 to 2887g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0059] Example 20

[0060] Add 6g of 1% m-aminobenzenesulfonic acid, 1.5g of 2% PQ37 aqueous solution and 30g of 50% PEG600 to 2887g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0061] Example 21

[0062] Add 6g of 1% m-aminobenzenesulfonic acid, 1.5g of 2% PQ7 aqueous solution and 3g of PEG20000 to 2911g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0063] Example 22

[0064] Add 6g of 1% m-aminobenzenesulfonic acid, 1.5g of 2% PQ7 aqueous solution and 3g of PEG300000 to 2911g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0065] Example 23

[0066] Add 6g of 1% m-aminobenzenesulfonic acid, 1.5g of 2% PQ7 aqueous solution and 30g of 50% PEG600 to 2930g of deionized water. After stirring evenly, add 30g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0067] Example 24

[0068] Add 6g of 1% m-aminobenzenesulfonic acid, 1.5g of 2% PQ7 aqueous solution and 30g of 50% PEG600 to 2660g of deionized water. After stirring evenly, add 300g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0069] Comparative Example 1

[0070] Add 30g of 50% PEG600 and 6g of 1% m-aminobenzenesulfonic acid aqueous solution to 2889g of deionized water, stir well, then add 75g of 2% nano-cerium oxide dispersion, and add imidazole to adjust the pH of the grinding solution to 6.0.

[0071] Comparative Example 2

[0072] Add 6g of 1% m-aminobenzenesulfonic acid aqueous solution and 4.5g of 2% PQ7 aqueous solution to 2915g of deionized water, stir well, then add 75g of 2% nano-cerium oxide dispersion, and add imidazole to adjust the pH of the grinding solution to 6.0.

[0073] Comparative Example 3

[0074] Add 15g of 1% chitosan S aqueous solution to 2910g of deionized water, stir well, then add 75g of 2% nano-cerium oxide dispersion, and add imidazole to adjust the pH of the grinding solution to 6.0.

[0075] Comparative Example 4

[0076] Add 1.5g of 2% PQ7 aqueous solution and 30g of 1% chitosan M aqueous solution to 2894g of deionized water, stir well, then add 75g of 2% nano-cerium oxide dispersion, and add imidazole to adjust the pH of the grinding solution to 6.0.

[0077] Comparative Example 5

[0078] Add 3.0g of 2% PQ7 aqueous solution and 15g of 1% chitosan S aqueous solution to 2907g of deionized water. After stirring evenly, add 75g of 2% nano-cerium oxide dispersion and add imidazole to adjust the pH of the grinding solution to 6.0.

[0079] Note: PEG600: Polyethylene glycol 600; PEG800: Polyethylene glycol 800; PEG-10K: Polyethylene glycol 10000;

[0080] PEG-20K: Polyethylene glycol 20000; PEG-300K: Polyethylene glycol 300000; PQ6: Polyquaternium 6

[0081] PQ7: Polyquaternium 7; PQ11: Polyquaternium 11; PQ28: Polyquaternium 28; PQ37: Polyquaternium 37; Chitosan S: Viscosity <100mPa.

[0082] Chitosan M: Viscosity 200-400 mPa·s

[0083] Chemical mechanical polishing rate evaluation: The polishing machine was an Ebara 300X, the polishing pad was an IC1000, the polishing disc rotation speed was 93 rpm, the polishing head rotation speed was 87 rpm, the polishing fluid flow rate was 300 ml / min, the polishing pressure was 2.0 psi, and the polishing time was 1 min.

[0084] The polishing rate of the polished film was calculated by measuring the reduction in film thickness. The ratio of the polishing rates of two different polished films was recorded as the removal rate selectivity ratio of the two polished films. Specific results are shown in Table 1.

[0085] Table 1. Components and polishing effects of some embodiments of the present invention.

[0086] As can be seen from Table 1, in Examples 1 to 4, the polishing slurry has an adjustable silicon dioxide removal rate and a certain silicon nitride removal rate. Overall, the silicon dioxide removal rate is higher than the silicon nitride removal rate, while the polycrystalline silicon removal rate is lower, showing that silicon dioxide has a higher removal selectivity for polycrystalline silicon.

[0087] In Examples 5-7, the removal rates of silica, silicon nitride, and polycrystalline silicon were controlled by changing the pH value of the polishing slurry.

[0088] In Examples 5 and 6, the silicon dioxide removal rate was lower than the silicon nitride removal rate, and the polycrystalline silicon rate was better suppressed.

[0089] In Examples 8-16, the polishing slurry exhibited a high silica removal rate and extremely high silica-to-silicon nitride and silica-to-polysilicon removal selectivity.

[0090] A comparison of Examples 1-7 with Examples 8-16 shows that the addition of polyaminopolysaccharides resulted in a better stopping effect of Poly.

[0091] Table 2. Components and polishing effects of the comparative examples of the present invention. Note: TEOS: silicon oxide film; SiN: silicon nitride film; Poly: polycrystalline silicon film; TEOS RR: silicon oxide film removal rate; SiN RR: silicon nitride film removal rate; Poly RR: polycrystalline silicon film removal rate; TEOS / SiN: silicon oxide film removal rate selectivity ratio to silicon nitride film removal rate; TEOS / Poly: silicon oxide film removal rate selectivity ratio to polycrystalline silicon film removal rate; 3-ABSA: m-aminobenzenesulfonic acid; 4-ABSA: p-aminobenzenesulfonic acid.

[0092] As can be seen from Table 2:

[0093] In Comparative Example 1, the selectivity ratio for silicon dioxide removal rate over silicon nitride was 1.3, and the selectivity ratio for silicon oxide removal rate over polycrystalline silicon was 8.0. Compared to Example 2, the silicon oxide removal rate in Comparative Example 4 was very low.

[0094] In Comparative Example 2, the selectivity ratio of silicon dioxide to silicon nitride removal rate was 5.6, and the selectivity ratio of silicon oxide to polycrystalline silicon removal rate was 3.3. Compared to Example 2, the polycrystalline silicon removal rate in Comparative Example 5 was very high, and it could not be effectively stopped on the surface of the polycrystalline silicon film.

[0095] In Comparative Example 3, the selectivity ratio of silicon dioxide to silicon nitride removal rate was 223.4, and the selectivity ratio of silicon oxide to polycrystalline silicon removal rate was 6.5. Compared to Example 11, the polycrystalline silicon removal rate in Comparative Example 6 was very high, and it could not be effectively stopped on the surface of the polycrystalline silicon film.

[0096] In Comparative Example 4, the selectivity ratio of silicon dioxide to silicon nitride removal rate was 82.7, and the selectivity ratio of silicon oxide to polycrystalline silicon removal rate was 4.9. Compared to Example 8, the polycrystalline silicon removal rate in Comparative Example 7 was very high, and it could not be effectively stopped on the surface of the polycrystalline silicon film.

[0097] In Comparative Example 5, the selectivity for silicon dioxide removal rate from silicon nitride was 1070.3, and the selectivity for silicon oxide removal rate from polycrystalline silicon was 7.5. Compared to Example 13, the polycrystalline silicon removal rate in Comparative Example 8 was very high, and it could not be properly stopped on the surface of the polycrystalline silicon film.

[0098] All contents in this invention are expressed as a percentage by mass.

[0099] This invention achieves the on-demand adjustment of the grinding rate of silicon oxide, silicon nitride, and polycrystalline silicon in the polishing slurry by selecting the best additives, resulting in a polishing slurry with an extremely low polycrystalline silicon polishing rate.

[0100] This invention significantly improves the removal rate of silicon oxide by nano-cerium oxide by adding cationic polymers (polyquaternary ammonium salts or polyaminopolysaccharides), and also improves its silicon nitride polishing rate.

[0101] Adding chitosan can significantly improve the removal rate of silica while inhibiting the removal rate of silicon nitride. Adding polyethylene glycol can suppress the removal rate of polycrystalline silicon. By combining these additives, the removal rates and selectivity of silica, silicon nitride, and polycrystalline silicon can be adjusted as needed.

[0102] This invention uses nano-cerium oxide as an abrasive, with a dynamic light-scattering particle size of 1-30 nm, which helps reduce scratches caused by chemical mechanical processes. The removal rates of silicon oxide, silicon nitride, and polycrystalline silicon can be controlled by selecting appropriate additives. Specifically, the selectivity ratio of silicon oxide removal rate to silicon nitride removal rate can be controlled within the range of 2:1 to 3500:1, and the ratio of silicon oxide removal rate to polycrystalline silicon removal rate can also be controlled within the range of 2:1 to 3500:1.

[0103] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A chemical mechanical polishing slurry, characterized in that, include: Nano-cerium oxide particles, polyethylene glycol, polyquaternium salt.

2. The polishing slurry as described in claim 1, characterized in that, The polishing fluid also includes polyaminopolysaccharides.

3. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The polyquaternary ammonium salts are polyquaternary ammonium salt-6, polyquaternary ammonium salt-7, polyquaternary ammonium salt-11, polyquaternary ammonium salt-28, and polyquaternary ammonium salt-37.

4. The chemical mechanical polishing slurry as described in claim 2, characterized in that, The polyaminopolysaccharide is chitosan and chitosan derivatives.

5. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The content of the nano-cerium oxide particles is 0.005 wt% to 5 wt%.

6. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The content of the polyquaternary ammonium salt is 0.0005 wt% to 0.1 wt%.

7. The chemical mechanical polishing slurry as described in claim 2, characterized in that, The content of the polyaminopolysaccharide is 0.0005 wt% to 0.1 wt%.

8. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The molecular weight range of the polyethylene glycol is 400-500,000.

9. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The content of the polyethylene glycol is 0.01 wt% to 5 wt%.

10. The chemical mechanical polishing slurry according to any one of claims 1-2, characterized in that, The pH of the polishing solution is 3.0 to 7.0.

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