CN109251675B

CN109251675B - Chemical mechanical polishing solution

Info

Publication number: CN109251675B
Application number: CN201710569910.5A
Authority: CN
Inventors: 李守田; 尹先升; 贾长征; 王雨春
Original assignee: Anji Microelectronics Technology Shanghai Co ltd
Current assignee: Anji Microelectronics Technology Shanghai Co ltd
Priority date: 2017-07-13
Filing date: 2017-07-13
Publication date: 2021-07-30
Anticipated expiration: 2037-07-13
Also published as: CN109251675A

Abstract

The invention provides a chemical mechanical polishing solution which comprises cerium oxide abrasive particles, polyquaternium and a pH regulator. The polyquaternium of the present invention can control the polishing rate of silicon oxide such that a high polishing rate of silicon oxide is achieved at high pressure and a low polishing rate of silicon oxide is achieved at low pressure, thereby achieving lower dishing (dishing).

Description

Chemical mechanical polishing solution

Technical Field

The invention relates to the field of chemical mechanical polishing, in particular to a chemical mechanical polishing solution.

Background

Cerium oxide is an important CMP polishing slurry abrasive, has a more efficient polishing characteristic to silicon dioxide materials than a traditional silica sol abrasive, and has been widely used for CMP polishing of STI and ILD. However, in STI CMP polishing applications, it is generally desirable to have a high polishing rate for silicon dioxide dielectric layers, while a low polishing rate for silicon nitride dielectric layers, preferably a polishing rate for silicon nitride dielectric layers that can approach zero. That is, a high silicon dioxide to silicon nitride selectivity is required. Organic molecules capable of effectively inhibiting the polishing rate of silicon nitride have been reported, for example, Electrochemical and Solid-State filter (vol 8(8), page G218-G221, year 2005) reports that compounds such as picolinic acid (picolinic acid) can improve the polishing rate of a polishing solution on a silicon dioxide dielectric layer, and simultaneously inhibit the polishing rate of silicon nitride, and compared with a common polishing solution, the polishing rate is reduced by at least 20 times, so that the selectivity of the polishing solution on silicon dioxide and silicon nitride exceeds 200.

However, in STI applications, in addition to suppressing the polishing rate of silicon nitride, dishing (dishing) is also controlled. One way to achieve low dishing values is to use a high silicon oxide polishing rate at high pressures (e.g., 4psi or 5 psi) and a low silicon oxide polishing rate at low pressures (e.g., 1.5 psi). In other words, the velocity versus pressure curve for silica should deviate from the conventional Prestonian linear equation. During the wafer polishing of the pattern, a high point needs to bear a large pressure, a low point (trench) needs to bear a much lower pressure than the high point, and the purpose of CMP is to remove the high point material and achieve planarization.

It has been reported that the quaternary ammonium salt with positive charge can generate strong charge repulsion to the cerium oxide friction particles with positive charge, but can generate strong attraction to the silicon oxide wafer with negative charge, thereby achieving the purpose of controlling the polishing rate of the silicon oxide. However, not all quaternary ammonium salts can control the polishing rate of silicon oxide well.

Disclosure of Invention

The present inventors have discovered that polyquaternium-10 (PQ-10) has a unique ability to control the polishing rate of silica. The invention uses polyquaternium-10 (PQ-10) to control the polishing rate of silicon oxide, so that high polishing rate of silicon oxide is achieved under high pressure, and low polishing rate of silicon oxide is achieved under low pressure, thereby achieving low dishing (dishing).

Specifically, the invention provides a chemical mechanical polishing solution. The polishing solution comprises a sol type cerium oxide abrasive, polyquaternium-10 and a pH regulator. The recipe can control the polishing rate of silicon oxide such that a higher polishing rate of silicon oxide is achieved at high pressure and a lower polishing rate of silicon oxide is achieved at low pressure, thereby achieving lower dishing (dishing).

The invention provides a chemical mechanical polishing solution which comprises cerium oxide abrasive particles, polyquaternium-10 and a pH regulator.

Preferably, the concentration of the sol-type cerium oxide abrasive particles is 0.1 to 2.0 wt%.

Preferably, the concentration of polyquaternium-10 is 5.0ppm to 150ppm, preferably 50ppm to 100 ppm.

Preferably, the chemical mechanical polishing solution further comprises an organic acid compound.

Preferably, the organic acid compound is picolinic acid and/or p-hydroxybenzoic acid.

Preferably, the concentration of the organic acid compound is 500-800 ppm.

Preferably, the pH value of the chemical mechanical polishing solution is 3.5-5.5.

Preferably, the pH adjusting agent is potassium hydroxide (KOH) and/or nitric acid (HNO)₃). Compared with the prior art, the invention has the advantages that: according to the invention, polyquaternium-10 (PQ-10) is added into the polishing solution, and has a nonlinear polishing rate to silicon oxide, so that a high polishing rate of silicon oxide can be achieved under high pressure, and a low polishing rate of silicon oxide can be achieved under low pressure, thereby obtaining low dishing (dishing).

Detailed Description

The advantages of the invention are explained in detail below with reference to specific embodiments.

The raw materials selected in the examples of the present invention are all commercially available. In the embodiment of the invention, small-molecular hexadecyl trimethyl ammonium chloride (CTMAC) and trimethyl benzyl ammonium chloride (BTMAC) are selected, and macromolecular quaternary ammonium salts comprise polyquaternium-10 (PQ-10) and polyquaternium-11 (PQ-11) as quaternary ammonium salts, and the molecular structures of the quaternary ammonium salts are shown as follows:

according to the specific components and contents in table 1, the corresponding quaternary ammonium salt, cerium oxide and 800ppm picolinic acid (picolinic acid) are mixed uniformly, water is used to make up the mass percent to 100%, and the solution pH is adjusted by potassium hydroxide (KOH) or nitric acid (HNO3), so as to obtain the following specific examples, wherein 1A without any quaternary ammonium salt is used as a reference solution. Specific examples were obtained as follows.

TABLE 1 comparative and example compounding ratios and practical results

The polishing solutions prepared in the above examples and comparative examples were subjected to different pressure conditions to measure the removal rate of the TEOS blank wafer.

The specific polishing conditions were Mirra, IC1010 polishing pad, Platten and Carrier speeds of 93rpm and 87rpm, respectively, 1.5psi,2psi, 3psi, 4psi and 5psi, a slurry flow rate of 150mL/min, and a polishing time of 60 seconds.

The results of the above comparative examples and examples show that small molecular quaternary ammonium salts such as cetyltrimethylammonium chloride (CTMAC) or trimethylbenzylammonium chloride (BTMAC) only linearly decrease the polishing rate of silica with a decrease in pressure, and polyquaternium-10 (PQ-10) can selectively inhibit the rate of silica. Specifically, as can be seen from Table 1, as in examples 1G, 1H, when the polyquaternium-10 (PQ-10) concentration is 16.7ppm or less, the influence of PQ-10 on the TEOS polishing rate is insignificant between 1.5psi and 5psi at the polishing pressure when the other component contents are the same; however, when the concentration of polyquaternium-10 (PQ-10) in the polishing solution is 100ppm, the polishing solution can significantly reduce the polishing rate of TEOS when the polishing pressure is less than or equal to 3psi, as in example 1J; as also shown in example 1I, when the concentration of polyquaternium-10 (PQ-10) in the polishing slurry is 50ppm, the polishing pressure is less than or equal to 2psi, which significantly reduces the TEOS polishing rate. In other words, the polishing rate curve of the above polishing solution for TEOS deviates from the linear region at a pressure of 3psi to 4psi when the concentration of polyquaternium-10 (PQ-10) is 100ppm, and deviates from the linear region at a pressure of 2psi to 3psi when the concentration of PQ-10 is 50 ppm. Meanwhile, as can be seen from table 1, the concentrations of cerium oxide and polyquaternium-10 in the formula of the polishing solution were adjusted under different pH conditions of the polishing solution, and the polishing rate of the corresponding polishing solution to TEOS and the polishing pressure condition thereof all showed a nonlinear relationship.

According to the specific components and contents of the quaternary ammonium salt in the table 2, the quaternary ammonium salt is dissolved and mixed with 1 wt% of sol type cerium oxide, 800ppm of p-hydroxybenzoic acid and the like, the mass percent is complemented to 100% by water, and the pH is adjusted to 4.5 by potassium hydroxide (KOH) or nitric acid (HNO3), and the comparative and specific implementation examples are shown in the following table:

TABLE 2 polishing Effect of comparative polishing solutions and inventive polishing solutions

The polishing conditions were Mirra, IC1010 polishing pad, Platten and Carrier speeds of 93rpm and 87rpm, respectively, pressure of 1.5psi,2psi, 3psi, 4psi and 5psi, polishing slurry flow rate of 150mL/min, and polishing time of 60 seconds.

The TEOS film thickness was measured using a NanoSpec film thickness measuring system (NanoSpec6100-300, Shanghai NanoSpec Technology Corporation). Starting 10mm from the edge of the wafer, 49 points were measured at equal intervals on the diameter line. The polishing rate was an average of 49 points.

The above comparative examples and examples show that not all of the polymeric polyquaterniums control the polishing rate of silicon oxide like polyquaternium-10 (PQ-10). Polyquaternium-11 (PQ-11) has a cationic functional group similar to that of polyquaternium-10 (PQ-10), but its polishing characteristics are different from those of polyquaternium-10 (PQ-10). The results of Table 2 also show that polyquaternium-11 (PQ-11), a small molecule quaternary ammonium salt like cetyltrimethylammonium chloride (CTMAC) or trimethylbenzylammonium chloride (BTMAC), only down-shifts the polishing rate of silica in parallel, while polyquaternium-10 (PQ-10) selectively suppresses the polishing rate of silica. For example, when the concentration of polyquaternium-10 (PQ-10) is 16.7ppm or less, polyquaternium-10 (PQ-10) has a small influence on the polishing rate of TEOS at a pressure of 1.5psi to 5psi, but when the concentration of polyquaternium-10 (PQ-10) is 100ppm, the polishing liquid significantly reduces the polishing rate of TEOS at a pressure of 3psi or less. In other words, the polishing rate curve for the polishing solution versus TEOS deviates from the linear region at a pressure in the range of 3psi to 4psi at a polyquaternium-10 (PQ-10) concentration of 100 ppm.

According to the specific components and content of the quaternary ammonium salt in the table 3, the mixture is uniformly mixed with 0.2 wt% of cerium oxide and 500ppm of p-hydroxybenzoic acid, water is used for complementing the mass percent to 100%, and the pH is adjusted to 4.5 by potassium hydroxide (KOH) or nitric acid (HNO3), so that the comparison and specific examples are shown in the following table:

TABLE 3 example proportions and specific implementation results

The polishing solutions prepared in the above examples were used to perform chemical mechanical polishing of TEOS blank wafers, respectively. The polishing conditions were Mirra, IC1010 polishing pad, Platten and Carrier speeds of 93rpm and 87rpm, respectively, pressure of 1.5psi,2psi, 3psi, 4psi and 5psi, polishing slurry flow rate of 150mL/min, and polishing time of 60 seconds.

Here, the TEOS film thickness was measured by a NanoSpec film thickness measuring system (NanoSpec6100-300, Shanghai NanoSpec Technology Corporation). Starting 10mm from the edge of the wafer, 49 points were measured at equal intervals on the diameter line. The polishing rate was an average of 49 points. The results in Table 3 show that polyquaternium-10 (PQ-10) has a small effect on the TEOS polishing rate at pressures of 1.5psi to 5psi when the concentration of polyquaternium-10 (PQ-10) in the polishing slurry is 150ppm, and PQ-10 can significantly change the TEOS versus pressure curve.

According to the specific components and contents of quaternary ammonium salt in table 4, the mixture is uniformly mixed with 1 wt% of cerium oxide, water is used for complementing the mass percent to 100%, and the pH is adjusted to 4.5 by potassium hydroxide (KOH) or nitric acid (HNO3), so that the comparison and specific implementation examples are shown in the following table:

TABLE 4 formulation and implementation results of the examples

The polishing solutions prepared in the above examples were used to perform chemical mechanical polishing of TEOS blank wafers, respectively. The polishing conditions were Mirra, IC1010 polishing pad, Platten and Carrier speeds of 93rpm and 87rpm, respectively, pressure of 1.5psi,2psi, 3psi, 4psi to 5psi, polishing slurry flow rate of 150mL/min, and polishing time of 60 seconds.

The TEOS film thickness was measured using a NanoSpec film thickness measuring system (NanoSpec6100-300, Shanghai NanoSpec Technology Corporation). Starting 10mm from the edge of the wafer, 49 points were measured at equal intervals on the diameter line. The polishing rate was an average of 49 points. The results in Table 4 show that, when the concentration of polyquaternium-10 (PQ-10) in the polishing solution was 100ppm, the TEOS polishing rate was significantly lower than that of the blank comparative example at a pressure of 3psi or less, and that polyquaternium-10 (PQ-10) was able to significantly change the TEOS polishing rate versus pressure curve.

In conclusion, the present invention adds polyquaternium-10 (PQ-10) to the polishing slurry, which has a nonlinear polishing rate for silicon oxide, and can achieve a high polishing rate for silicon oxide at high pressure and a low polishing rate for silicon oxide at low pressure, thereby achieving a lower dishing (dishing).

The embodiments of the present invention have been described in detail, but the embodiments are merely examples, and the present invention is not limited to the embodiments described above. Any equivalent modifications and substitutions to those skilled in the art are also within the scope of the present invention. Accordingly, equivalent changes and modifications made without departing from the spirit and scope of the present invention should be covered by the present invention.

Claims

1. A chemical mechanical polishing solution comprises a cerium oxide abrasive, a polyquaternium and a pH regulator;

the polyquaternium is selected from polyquaternium-10.

2. The chemical mechanical polishing solution according to claim 1, wherein the cerium oxide abrasive has a concentration of 0.1 to 2 wt%.

3. The chemical mechanical polishing solution according to claim 1, wherein the polyquaternium-10 is present in a concentration of 5ppm to 150 ppm.

4. The chemical mechanical polishing solution according to claim 3, wherein the polyquaternium-10 is present in a concentration of 50ppm to 100 ppm.

5. The chemical mechanical polishing solution according to any one of claims 1 to 4, wherein the chemical mechanical polishing solution further comprises an organic acid compound.

6. The chemical mechanical polishing solution according to claim 5, wherein the organic acid compound is picolinic acid and/or parahydroxybenzoic acid.

7. The chemical mechanical polishing solution according to claim 5, wherein the concentration of the organic acid compound is 500 to 800 ppm.

8. The chemical mechanical polishing solution according to claim 1, wherein the pH of the chemical mechanical polishing solution is 3.5 to 5.5.

9. The chemical mechanical polishing solution according to claim 1, wherein the pH adjusting agent is potassium hydroxide (KOH) and/or nitric acid (HNO)₃)。