Chemical mechanical polishing solution

Abstract

According to the polishing solution based on cerium oxide, the compound in the general formula I is used as a polycrystalline silicon auxiliary agent, and polishing removal of polycrystalline silicon is achieved under the acidic condition. And meanwhile, the polishing rate ratio of silicon oxide to polycrystalline silicon can be adjusted. The specific structure of the compound shown in the general formula I is shown in the specification, X1 to X3 are independently selected from C or N, and at least one of X1 to X3 is N; r1 is selected from H or amino; r2 is selected from H, methyl and amino;

Description

Technical Field

[0001] This invention relates to the field of chemical mechanical polishing slurries, and more particularly to a chemical mechanical polishing slurry for silicon oxide and polycrystalline silicon. Background Technology

[0002] Shallow trench isolation (STI) technology is widely used as a method for isolating the active regions of semiconductor devices. It not only improves the electrical performance of devices but also reduces transistor spacing by eliminating loss regions on the surface, thereby improving chip performance and integration density. The formation of an STI structure typically involves depositing, patterning, and etching a silicon nitride mask to form trenches, which are then filled with deposited silicon oxide. Excess silicon oxide is then removed and stopped at the silicon nitride layer using a chemical mechanical polishing (CMP) process. Ultimately, this process must achieve a highly flat and uniform surface.

[0003] Today, approximately 50% of all STI polishing is performed using cerium dioxide (CeO2)-based slurries. Even though cerium dioxide has lower mechanical abrasiveness than conventional abrasive particles such as silica or alumina, its use for polishing oxide layers is of particular interest due to its chemical affinity for silica. Because of this high chemical affinity, even with reduced cerium dioxide content in the slurry, the removal rate and selectivity for Si3N4 are high. In fact, cerium dioxide slurries typically contain only 1 wt% abrasive material, while silica-based slurries are characterized by at least 12 wt%, and in most cases even 20-30 wt% abrasive content.

[0004] With the continuous development of semiconductor technology and the continuous improvement of process technology, advanced processes have led to demands for increasing the polishing rate of polycrystalline silicon in STI polishing slurries. Traditional STI polishing slurries lack the ability to remove polycrystalline silicon. Therefore, this application presents a cerium oxide-based polishing slurry that uses a compound of general formula I as a polycrystalline silicon additive, achieving polishing removal of polycrystalline silicon under acidic conditions. Simultaneously, the polishing rate ratio of silicon oxide to polycrystalline silicon can be adjusted. Summary of the Invention

[0005] To overcome the aforementioned technical deficiencies, the present invention aims to provide a chemical mechanical polishing fluid, comprising cerium dioxide abrasive particles and an accelerator, wherein the accelerator is a compound of general formula I, with the specific structure as follows:

[0006]

[0007] Wherein, X1 to X3 are each independently selected from C or N, and at least one of X1 to X3 is N; R1 is selected from H or amino; R2 is selected from H, methyl, amino,

[0008] Furthermore, the accelerator is a pyrimidine compound containing one or more amino groups or its derivatives.

[0009] Furthermore, the accelerator is selected from 2-aminopyrimidine, 4-aminopyrimidine, 2,6-diaminopyrimidine, 2,5-diaminopyrimidine, 2,4,6-triaminopyrimidine, and 4-acetyl-2-aminopyrimidine.

[0010] Furthermore, the accelerator is a pyridine compound containing one or more amino groups or its derivatives.

[0011] Furthermore, the accelerator is selected from 2,6-diaminopyridine, N-acetyl-1,6-diaminopyridine, and N-(4-aminopyridin-2-yl)acetamide.

[0012] Furthermore, the accelerator is a triazine compound containing one or more amino groups or its derivatives.

[0013] Furthermore, the accelerator is selected from 2,4-diamino-6-methyltriazine, 2,4-diamino-6-[2-(2-methyl-1-imidazolyl)ethyl]-1,3,5-triazine, and cyclopropanezine.

[0014] Furthermore, the mass percentage concentration of the cerium dioxide particles is 0.2% to 2.0%.

[0015] Furthermore, the concentration of the accelerator is 100ppm to 3000ppm.

[0016] Furthermore, the pH adjuster is acetic acid, nitric acid, or hydrochloric acid.

[0017] Furthermore, the pH value of the chemical mechanical polishing solution is 3-6.

[0018] This invention discloses that a compound of general formula I, as an additive, can enhance the removal rate of polycrystalline silicon in a cerium oxide polishing slurry under acidic conditions. This invention achieves the polishing of polycrystalline silicon based on a cerium oxide polishing slurry under acidic conditions, while simultaneously allowing adjustment of the polishing rate ratio between silicon oxide and polycrystalline silicon. Detailed Implementation

[0019] The chemical mechanical polishing composition of the present invention will be described in detail below through specific embodiments in order to better understand the present invention, but the following embodiments do not limit the scope of the present invention.

[0020] The embodiments of this application select compounds with the following structures as accelerators.

[0021]

[0022] In the specific embodiments and comparative examples, all components were dissolved and mixed thoroughly according to the formulations given in Table 1, and water was added to bring the mass percentage to 100%. The pH was adjusted to the desired value using a pH adjuster. All reagents of this invention are commercially available.

[0023] Polishing rate determination: TEOS and polycrystalline silicon blank wafers were polished using a Mirra polishing machine. Polishing conditions included: IC1000 polishing pad, Platten and Carrier rotation speeds of 93 rpm and 87 rpm respectively, pressure of 3.0 psi, and polishing fluid flow rate of 150 mL / min. TEOS and polycrystalline silicon film thicknesses were measured using a NanoSpec film thickness measurement system (NanoSpec6100-300, Shanghai Nanospec Technology Corporation). For blank wafers, film thickness was measured at 49 points at equal intervals along the diameter line, starting 3 mm from the wafer edge. The polishing rate was the average of these 49 points.

[0024] Table 1. Components, content, and pH value of polishing slurries in Examples 1-42 and Comparative Examples 1-5, and the effect of compound of general formula I on the polishing rate of polycrystalline silicon.

[0025]

[0026]

[0027]

[0028] Compared to Comparative Example 1 and Example 15, the removal rate of polysilicon decreased from [previous rate] after the addition of accelerator P5. Increased to Compared to Comparative Example 2 and Example 18, the removal rate of polysilicon decreased from [previous rate] after the addition of accelerator P6. Increased to The results in Table 1 show that, as additives, compounds of general formula I can significantly improve the removal rate of polycrystalline silicon in cerium oxide-based chemical mechanical polishing slurries under acidic conditions.

[0029] As can be seen from Examples 12-15, the polycrystalline silicon maintains a high removal rate with increasing cerium oxide content. Therefore, the preferred cerium oxide content in this invention is between 0.2 wt% and 2.0 wt%. Below 0.2 wt%, the TEOS polishing rate is already very low and has no practical value; above 2.0 wt%, the increase in TEOS polishing rate is very small, and the cost also increases, resulting in very low commercial value.

[0030] As can be seen from Examples 6-10, as the amount of compound of general formula I increases, polycrystalline silicon maintains a high removal rate. The preferred concentration range of the accelerator in this application is between 100ppm and 3000ppm. Above 3000ppm, particles in the polishing solution will agglomerate and settle.

[0031] As can be seen from Examples 6-10, the polishing rate ratio of silicon oxide to polycrystalline silicon can vary from 1.45 to 0.97; as can be seen from Examples 16-19, the polishing rate ratio of silicon oxide to polycrystalline silicon can vary from 2.57 to 1.11; and as can be seen from Examples 21-23, the polishing rate ratio of silicon oxide to polycrystalline silicon can vary from 1.72 to 0.76. Therefore, this invention achieves polishing removal of polycrystalline silicon under acidic conditions while simultaneously adjusting the polishing rate ratio of silicon oxide to polycrystalline silicon. At the same time, the polishing rate of silicon nitride is also very low, and the selectivity ratio of the polishing rate of silicon oxide to silicon nitride of this invention can be greater than 10.

[0032] Between pH 3.0 and 6.0, particles in the polishing solution tend to agglomerate and settle when pH is less than 3.0. When pH is greater than 6.0 or even in the alkaline range, hydroxide ions in the solution can increase the polishing rate of polycrystalline silicon, which is no longer applicable to the range of using general formula I compounds to increase the polishing rate of polycrystalline silicon under acidic conditions in this case.

[0033] 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, The chemical mechanical polishing slurry comprises cerium dioxide abrasive particles and an accelerator, wherein the accelerator is a compound of general formula I, with the specific structure as follows: Wherein, X1 to X3 are each independently selected from C or N, and at least one of X1 to X3 is N; R1 is selected from H or amino; R2 is selected from H, methyl, amino, 2. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The accelerator is a pyrimidine compound containing one or more amino groups or its derivatives.

3. The chemical mechanical polishing slurry as described in claim 2, characterized in that, The accelerator is selected from 2-aminopyrimidine, 4-aminopyrimidine, 2,6-diaminopyrimidine, 2,5-diaminopyrimidine, 2,4,6-triaminopyrimidine, and 4-acetyl-2-aminopyrimidine.

4. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The accelerator is a pyridine compound containing one or more amino groups or its derivatives.

5. The chemical mechanical polishing slurry as described in claim 4, characterized in that, The accelerator is selected from 2,6-diaminopyridine, N-acetyl-1,6-diaminopyridine, and N-(4-aminopyridin-2-yl)acetamide.

6. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The accelerator is a triazine compound containing one or more amino groups or its derivatives.

7. The chemical mechanical polishing slurry as described in claim 6, characterized in that, The accelerator is selected from 2,4-diamino-6-methyltriazine, 2,4-diamino-6-[2-(2-methyl-1-imidazolyl)ethyl]-1,3,5-triazine, and cyclopropanezine.

8. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The mass percentage concentration of the cerium dioxide particles is 0.2% to 2.0%.

9. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The concentration of the accelerator is 100ppm to 3000ppm.

10. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The pH adjuster is acetic acid, nitric acid, or hydrochloric acid.

11. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The pH value of the chemical mechanical polishing solution is 3-6.

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