Chemical-mechanical polishing slurry

Abstract

The present application provides a cerium-oxide-based polishing slurry, which uses the compound of general formula (I) as a polycrystalline silicon auxiliary, and achieves the removal of polycrystalline silicon by means of polishing under acidic conditions. Moreover, the ratio of a silicon oxide removal rate to a polycrystalline silicon removal rate can be adjusted. The compound of general formula (I) has a specific structure as shown in formula (I) below: 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 an amino group; and R2 is selected from H, a methyl group, an amino group, formula (II) and formula (III).

Description

Chemical mechanical polishing solution TECHNICAL FIELD

[0001] The present application relates to the field of chemical mechanical polishing solution, in particular to a chemical mechanical polishing solution for silicon oxide and polysilicon. BACKGROUND

[0002] As a method for isolating the active region of a semiconductor device, the application range of shallow trench isolation (STI) technology is very wide, which not only improves the electrical performance of the device, but also shortens the pitch of the transistor by eliminating the loss area on the surface, thereby improving the performance and integration of the chip. The formation of STI structure is usually completed by using silicon nitride mask through deposition, patterning, etching silicon to form a groove, and filling the groove with deposited silicon oxide. Then the excess silicon oxide is generally removed by chemical mechanical polishing (CMP) process and stopped at the silicon nitride layer, and finally this process must achieve a highly flat and uniform surface.

[0003] Today, about 50% of all STI polishing is carried out using ceria (CeO2) based slurries. Even though ceria is less mechanically abrasive than traditional abrasive particles such as silica or alumina, ceria is of particular interest for polishing of oxide layers due to its chemical affinity to silicon dioxide. Due to this high chemical affinity, the removal rate and selectivity to Si3N4 is high even with a reduced ceria content in the slurry. In fact, ceria slurries typically contain only 1 wt% of abrasive material, while silica based slurries are characterized by abrasive contents of at least 12 wt% and in most cases even 20-30 wt%.

[0004] With the continuous development of semiconductor technology and the continuous improvement of process, the polishing rate of polysilicon is required to be increased in advanced processes. The traditional STI polishing solution does not have the removal ability of polysilicon, therefore, based on the ceria polishing solution, the present application uses a compound of general formula I as a polysilicon additive to achieve the polishing and removal of polysilicon under acidic conditions. At the same time, the polishing rate ratio of silicon oxide and polysilicon can be adjusted. SUMMARY

[0005] In order to overcome the above technical defects, the purpose of the present application is to provide a chemical mechanical polishing solution, which comprises ceria abrasive particles and a speed enhancer, the speed enhancer is a compound of general formula I, and the specific structure is as follows:

[0006] 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,

[0007] Further, the speed enhancer is a pyrimidine compound containing one or more amino groups and derivatives thereof.

[0008] Further, the speed enhancer is selected from 2-amino pyrimidine, 4-amino pyrimidine, 2,6-diamino pyrimidine, 2,5-diamino pyrimidine, 2,4,6-triamino pyrimidine, 4-acetyl-2-amino pyrimidine.

[0009] Further, the speed enhancer is a pyrimidine compound containing one or more amino groups and derivatives thereof.

[0010] Further, the speed enhancer is selected from 2,6-diamino pyrimidine, N-acetyl-1,6-diamino pyrimidine, N-(4-aminopyrimidin-2-yl)acetamide.

[0011] Further, the speed enhancer is a pyrimidine compound containing one or more amino groups and derivatives thereof.

[0012] Further, the speed enhancer is selected from 2,4-diamino-6-methyl-s-triazine, 2,4-diamino-6-[2-(2-methyl-1-imidazolyl)ethyl]-1,3,5-triazine, cyromazine.

[0013] Further, the mass percentage concentration of the cerium dioxide particles is 0.2% to 2.0%.

[0014] Further, the concentration of the speed enhancer is 100 ppm to 3000 ppm.

[0015] Further, the pH adjuster is acetic acid, nitric acid, hydrochloric acid.

[0016] Further, the pH value of the chemical mechanical polishing liquid is 3 to 6.

[0017] The compound of general formula I as an additive can make the cerium oxide polishing liquid have the ability to improve the polysilicon removal rate under acidic conditions. The present application realizes the polishing of polysilicon based on cerium oxide polishing liquid under acidic conditions, and can adjust the polishing rate ratio of silicon oxide and polysilicon. DETAILED DESCRIPTION

[0018] The chemical mechanical polishing composition of the present application is described in detail below through specific examples, so that the present application can be better understood, but the following examples do not limit the scope of the present application.

[0019] The compound of the following structure is selected as the speed enhancer in the examples of the present application.

[0020] The specific embodiments and comparative examples are prepared according to the formulations given in Table 1, all components are dissolved and mixed uniformly, and water is added to make up the mass percentage to 100%. The pH is adjusted to the desired value with a pH adjuster. All reagents of the present application are commercially available.

[0021] Polishing rate determination: TEOS and polysilicon blank wafers are polished using a Mirra polisher, and the corresponding polishing conditions include: IC1000 polishing pad, Platten and Carrier rotation speeds of 93 rpm and 87 rpm, respectively, a pressure of 3.0 psi, and a polishing liquid flow rate of 150 mL / min. The TEOS and polysilicon film thicknesses are measured using a NanoSpec film thickness measurement system (NanoSpec 6100-300, Shanghai Nanospec Technology Corporation). The blank film thickness is measured at 49 points at equal intervals on the diameter line, starting from 3 mm from the edge of the wafer. The polishing rate is the average of the 49 points.

[0022] Table 1: Components, contents, and pH values of the polishing liquids of Examples 1-42 and Comparative Examples 1-5, and the effect of the compound of Formula I on the polysilicon polishing rate

[0023] Compared with Comparative Example 1 and Example 15, after the addition of the speed enhancer P5, the removal rate of polysilicon increased from to Compared with Comparative Example 2 and Example 18, after the addition of the speed enhancer P6, the removal rate of polysilicon increased from to As shown by the results in Table 1, as an additive, the compound of Formula I can greatly increase the removal rate of polysilicon in an acidic cerium oxide particle-based chemical mechanical polishing liquid.

[0024] As can be seen from Examples 12-15, as the cerium oxide content increases, the polysilicon always maintains a high removal rate, and therefore, the present application preferably has a cerium oxide solid content of 0.2wt% to 2.0wt%. Below 0.2wt%, the TEOS polishing rate is already very low and has no practical value; above 2.0wt%, the increase in the TEOS polishing rate is already very small, and the cost is also increased, and the commercial value is already very low.

[0025] As can be seen from Examples 6-10, as the amount of the compound of general formula I is increased, the polysilicon always maintains a high removal rate. The preferred concentration of the accelerator is between 100 ppm and 3000 ppm. When the concentration is higher than 3000 ppm, the particles in the polishing solution will agglomerate and cause sedimentation.

[0026] As can be seen from Examples 6-10, the polysilicon and silicon oxide polishing rate ratio can be changed from 1.45 to 0.97; as can be seen from Examples 16-19, the polysilicon and silicon oxide polishing rate ratio can be changed from 2.57 to 1.11; as can be seen from Examples 21-23, the polysilicon and silicon oxide polishing rate ratio can be changed from 1.72 to 0.76. Thus, the present application can adjust the polysilicon and silicon oxide polishing rate ratio while achieving the polishing removal of polysilicon under acidic conditions. The polishing rate of silicon nitride is also very low, and the polysilicon and silicon oxide polishing rate ratio of the present application can be greater than 10.

[0027] When the pH is between 3.0 and 6.0, when the pH is less than 3.0, the particles in the polishing solution will agglomerate and cause sedimentation; when the pH is greater than 6.0 or even in the alkaline range, the hydroxyl ions in the solution can increase the polishing rate of polysilicon, and thus the compound of general formula I of the present application is not suitable for use in the acidic range to increase the polishing rate of polysilicon.

[0028] It should be noted that the embodiments of the present application are preferred and do not limit the present application in any form. Any skilled person in the art can change or modify the above-mentioned technical content to obtain equivalent effective embodiments, as long as the content of the technical solution of the present application is not deviated, and any modification or equivalent change and modification of the above-mentioned embodiments according to the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. A chemical mechanical polishing liquid, characterized by comprising: The chemical mechanical polishing liquid comprises cerium dioxide abrasive particles and a speed enhancer, the speed enhancer being a compound of general formula I, and the specific structure is as follows: wherein X1to X3are each independently selected from C or N, and at least one of X1to X3is N; R1is selected from H or amino; R2is selected from H, methyl, amino, 2. The chemical mechanical polishing liquid according to claim 1, wherein The speed enhancer is a pyrimidine compound containing one or more amino groups and derivatives thereof.

3. The chemical mechanical polishing liquid according to claim 2, wherein The speed enhancer is selected from 2-amino pyrimidine, 4-amino pyrimidine, 2,6-diamino pyrimidine, 2,5-diamino pyrimidine, 2,4,6-triamino pyrimidine, 4-acetyl-2-amino pyrimidine.

4. The chemical mechanical polishing liquid according to claim 1, wherein The speed enhancer is a pyridine compound containing one or more amino groups and derivatives thereof.

5. The chemical mechanical polishing liquid according to claim 4, wherein the abrasive is alumina having a particle size of 0.1 to 0.3 μm. The speed enhancer is selected from 2,6-diamino pyridine, N-acetyl-1,6-diamino pyridine, N-(4-aminopyridin-2-yl)acetamide.

6. The chemical mechanical polishing liquid according to claim 1, wherein The speed enhancer is a s-triazine compound containing one or more amino groups and derivatives thereof.

7. The chemical mechanical polishing liquid according to claim 6, wherein The speed enhancer is selected from 2,4-diamino-6-methyl s-triazine, 2,4-diamino-6-[2-(2-methyl-1-imidazolyl)ethyl]-1,3,5-triazine, cyromazine.

8. The chemical mechanical polishing liquid according to claim 1, wherein The mass percentage concentration of the cerium dioxide particles is 0.2% to 2.0%.

9. The chemical mechanical polishing liquid according to claim 1, wherein The concentration of the speed enhancer is 100 ppm to 3000 ppm.

10. The chemical mechanical polishing liquid of claim 1, wherein The pH adjuster is acetic acid, nitric acid, hydrochloric acid.

11. The chemical mechanical polishing liquid of claim 1, wherein The pH value of the chemical mechanical polishing liquid is 3-6.

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