Chemical mechanical polishing composition

Abstract

Disclosed in the present invention is a chemical mechanical polishing composition, which is used for achieving different polishing rate SiN / TEOS selectivity ratios. Specifically, a preferred trivalent transition metal ion compound iron(III) nitrate nonahydrate is added to a cerium oxide polishing solution, so that the polishing rate of SiN can be effectively improved at different pressures (1.5 psi, 2.0 psi and 3.0 psi) and within a concentration range (1-100 ppm) and a pH range (4.0-9.0), and a wide operation window is achieved. Moreover, different SiN / TEOS selectivity ratios can be achieved by adjusting the amount of iron(III) nitrate nonahydrate added. In addition, at a pressure of 3.0 psi, lanthanum(III) nitrate hexahydrate and cerium(III) nitrate hexahydrate can also effectively improve the polishing rate of SiN within a concentration range (20-100 ppm) and the pH range (4.0-9.0).

Description

A chemical mechanical polishing composition Technical Field

[0001] The present invention relates to a cerium oxide chemical mechanical polishing liquid, and more particularly to a chemical mechanical polishing composition which uses trivalent transition metal ions as additives to effectively achieve SiN / TEOS selectivity with different polishing rates. Background Art

[0002] In the semiconductor device manufacturing process, chemical mechanical polishing (CMP) has become the most effective and mature planarization technology. Among CMP slurries based on different abrasives, cerium oxide particles can still provide higher polishing rates at lower concentrations while achieving higher selectivity, making them of great value in CMP applications. Typically, most CMP slurries strive to reduce the removal rate of silicon nitride while achieving relatively high removal rates for other materials. For example, in the widely-regarded shallow trench isolation (STI) process, silicon nitride (SiN) is used as the termination layer, and the CMP slurry used requires a higher removal rate for silicon dioxide (TEOS).

[0003] However, with advances in semiconductor etching technology, oxide line widths are gradually decreasing. Consequently, it is desirable for the chemical mechanical polishing solution to prioritize polishing silicon nitride over oxide, i.e., to have the opposite selectivity requirement from conventional STI. This minimizes defects in the oxide lines formed on the substrate surface. Therefore, finding a polishing solution that can increase the polishing rate of silicon nitride is a problem that needs to be solved. The present invention effectively increases the polishing rate of SiN by adding trivalent transition metal ions to the cerium oxide polishing solution. Furthermore, by adjusting the content of the preferred trivalent transition metal ions, different SiN / TEOS selectivities can be achieved.

[0004] Summary of the Invention

[0005] The invention discloses a chemical mechanical polishing composition comprising: water; cerium oxide abrasive particles; and a trivalent transition metal ion compound.

[0006] Furthermore, in the chemical mechanical polishing composition, the trivalent transition metal ion is iron (III), lanthanum (III) or cerium (III).

[0007] Furthermore, the trivalent transition metal ion compound is iron (III) nitrate nonahydrate, lanthanum (III) nitrate hexahydrate or cerium (III) nitrate hexahydrate.

[0008] Furthermore, the concentration range of the trivalent transition metal ion compound is 1-100 ppm.

[0009] Furthermore, the mass percentage content of the cerium oxide abrasive particles ranges from 0.02% to 0.4%.

[0010] Furthermore, the pH value of the polishing composition ranges from 4.0 to 9.0.

[0011] Furthermore, the polishing composition further comprises a pH adjuster, and the pH adjuster is selected from an inorganic acid or an inorganic base, preferably HNO3 or KOH.

[0012] The present invention adds a preferred trivalent transition metal ion compound, iron (III) nitrate nonahydrate, to a cerium oxide polishing liquid. This method effectively improves the SiN polishing rate under various pressures (1.5 psi, 2.0 psi, and 3.0 psi), concentration ranges (1-100 ppm), and pH ranges (4.0-9.0), with a wide operating window. Furthermore, by adjusting the amount of iron (III) nitrate nonahydrate added, different SiN / TEOS selectivities can be achieved. Furthermore, at a pressure of 3.0 psi, lanthanum (III) nitrate hexahydrate and cerium (III) nitrate hexahydrate also effectively improve the SiN polishing rate within a concentration range (20-100 ppm) and a pH range (4.0-9.0). Specific embodiments

[0013] Example 1

[0014] The raw materials used in this example are all commercially available. According to the proportions of the components listed in Table 1, each component was dissolved in deionized water, and the weight percentage was adjusted to 100% with deionized water. The pH was then adjusted to 4.5 using a pH adjuster (HNO3 or KOH) to obtain the polishing solutions of Comparative Examples 1A-1C and Examples 1D-1F of the present invention.

[0015] Table 1 Components and contents of the polishing liquids of the comparative examples and the examples

[0016] In order to further measure the polishing performance of the polishing solution in each embodiment and comparative example, the polishing rate of the polishing solution on TEOS wafers and SiN wafers was measured at different polishing pressures of 1.5 psi, 2.0 psi or 3.0 psi. The results are shown in Table 2.

[0017] Polishing conditions: the polishing machine is Ebara F-REX-300X, the polishing pad is IK4350, the platen and head speeds are 93 rpm and 87 rpm respectively, the polishing pressure is 1.5 psi, 2.0 psi or 3.0 psi, the polishing liquid flow rate is 300 mL / min, and the polishing time is 60 s.

[0018] Polishing Step: TEOS and SiN blank wafers were polished using the polishing slurries prepared above, using the polishing equipment and polishing conditions described above. Film thickness was measured using a NanoSpec film thickness measurement system (NanoSpec 6100-300, Shanghai Nanospec Technology Corporation). The polishing rate was measured at 49 points on a diameter line at equal intervals, starting 3 mm from the wafer edge. The polishing rate for each polishing slurry was the average of the polishing rates at these 49 points.

[0019] Table 2 Polishing rates of comparative and example polishing solutions at different polishing pressures

[0020] The polishing results of Comparative Examples 1A and 1C show that the addition of aluminum (III) nitrate nonahydrate significantly inhibits the SiN polishing rate. The polishing results of Comparative Example 1A and Examples 1D and 1E demonstrate that, at a polishing pressure of 3.0 psi, the addition of either lanthanum (III) nitrate hexahydrate or iron (III) nitrate nonahydrate increases the SiN polishing rate. However, at lower polishing pressures (1.5 psi or 2.0 psi), the addition of lanthanum (III) nitrate hexahydrate decreases the SiN polishing rate, while the addition of iron (III) nitrate nonahydrate still significantly increases the SiN polishing rate, more than doubling it.

[0021] The polishing results of Comparative Example 1B and Example 1F show that at a polishing pressure of 3.0 psi, cerium (III) nitrate hexahydrate can more than double the SiN polishing rate. However, at low pressures (1.5 psi or 2.0 psi), cerium (III) nitrate hexahydrate significantly inhibits the SiN polishing rate. In summary, the addition of trivalent transition metal ions to a cerium oxide polishing solution can increase the SiN polishing rate under certain pressures. Preferably, compared to lanthanum (III) or cerium (III), iron (III) nitrate nonahydrate in the example has a wider polishing pressure operating window, significantly promoting the SiN polishing rate at 1.5 psi, 2.0 psi, and 3.0 psi.

[0022] Example 2

[0023] According to the proportions of the components in Table 3, each component was dissolved in deionized water, and the mass percentage was adjusted to 100% with deionized water. The pH was adjusted to 4.5 with HNO3 or KOH to obtain the polishing solutions of Comparative Example 2A and Examples 2B-2H. The polishing solutions of Comparative Example 2A and Examples 2B-2H were then used to chemically mechanically polish TEOS and SiN blank wafers, respectively. The polishing results were compared. The results are shown in Table 3.

[0024] Polishing conditions were as follows: Ebara F-REX-300X polishing machine, IK4350 polishing pad, platen and head speeds of 93 rpm and 87 rpm, respectively, polishing pressure of 2.0 psi, polishing fluid flow rate of 300 mL / min, and polishing time of 60 s. Film thickness was measured using a NanoSpec film thickness measurement system.

[0025] Table 3 Effect of adding different amounts of iron (III) nitrate nonahydrate on polishing effect

[0026] Table 3 shows the effect of adding different amounts of iron (III) nitrate nonahydrate on the polishing effect of cerium oxide polishing liquid. It can be seen that even adding only a trace amount (1ppm, 5ppm) of iron (III) nitrate nonahydrate can increase the polishing rate of SiN. As the content of iron (III) nitrate nonahydrate increases, the SiN rate gradually increases, and the optimal concentration is 50ppm. When the concentration of iron (III) nitrate nonahydrate increases to 100ppm, the SiN polishing rate of Example 2H is still significantly higher than that of Comparative Example 2A, indicating that iron (III) nitrate nonahydrate has a wider concentration range. Compared with Comparative Example 2A, the TEOS polishing rate of Example 2H is significantly suppressed, so the SiN / TEOS selectivity is significantly improved. By adjusting the amount of iron (III) nitrate nonahydrate added, different SiN / TEOS selectivities can be achieved.

[0027] Table 4 shows the effects of adding different amounts of cerium (III) nitrate hexahydrate or lanthanum (III) nitrate hexahydrate on the polishing performance of cerium oxide polishing solutions. The components were dissolved in deionized water according to their respective proportions, and the weight percentage was adjusted to 100% with deionized water. The pH was adjusted to 4.5 with HNO3 or KOH to obtain polishing solutions for the comparative examples and examples. The polishing solutions prepared above were used for chemical mechanical polishing of TEOS and SiN blank wafers, respectively, and the polishing performance was compared. The results are shown in Table 4.

[0028] Polishing conditions were as follows: Mirra polishing machine, IC1000 polishing pad, platen and head speeds of 93 rpm and 87 rpm, respectively, polishing pressure of 3.0 psi, polishing fluid flow rate of 150 mL / min, and polishing time of 60 s. Film thickness was measured using a NanoSpec film thickness measurement system.

[0029] Table 4 Effect of adding different amounts of cerium (III) nitrate hexahydrate or lanthanum (III) nitrate hexahydrate on the polishing effect

[0030] As can be seen from Table 4, when the content of cerium (III) nitrate hexahydrate is gradually increased from 20ppm to 80ppm, the polishing rate of SiN is gradually improved. When the concentration of cerium (III) nitrate hexahydrate is increased to 100ppm, the polishing rate of SiN in Example 3E decreases compared to Example 3D, but is still higher than that in Comparative Example 3A. When the content is further increased to 300ppm, the polishing rate of SiN in Example 3F is significantly decreased compared to Comparative Example 3A. When lanthanum (III) nitrate hexahydrate is added, the polishing rate of SiN is gradually increased as its content increases from 20ppm to 100ppm. When its content is further increased to 200ppm, the polishing rate of SiN is significantly decreased compared to Comparative Example 3G. This shows that under a polishing pressure of 3.0psi, cerium (III) nitrate hexahydrate and lanthanum (III) nitrate hexahydrate can effectively improve the polishing rate of SiN in the concentration range of 20-100ppm.

[0031] Example 3

[0032] Polishing solutions for the comparative examples and examples were prepared by dissolving the components in deionized water according to the proportions listed in Tables 5 and 6, adjusting the mass percentage to 100% with deionized water, and adjusting the pH values ​​with HNO₃ or KOH. The polishing solutions prepared above were used to chemically mechanically polish TEOS and SiN blank wafers, respectively, and the polishing results were compared. The results are shown in Table 4.

[0033] Polishing conditions were as follows: Mirra polishing machine, IC1000 polishing pad, platen and head speeds of 93 rpm and 87 rpm, respectively, polishing pressure of 2.0 psi or 3.0 psi, polishing fluid flow rate of 150 mL / min, and polishing time of 60 s. Film thickness was measured using a NanoSpec film thickness measurement system.

[0034] Table 5 Effect of adding iron (III) nitrate nonahydrate on polishing effect under different pH conditions

[0035] Table 5 shows the effect of adding 50ppm of iron (III) nitrate nine hydrate on the polishing effect of cerium oxide polishing solution under different pH conditions. It can be seen that the addition of iron (III) nitrate nine hydrate in the polishing solution pH range of 4.0-9.0 can effectively improve the polishing rate of SiN. The polishing results of Comparative Examples 4A and 4B show that at pH = 3.5, the polishing rate of SiN will be suppressed regardless of whether iron (III) nitrate nine hydrate is added. When the pH is adjusted to 4.0-6.5, the addition of iron (III) nitrate nine hydrate can not only improve the polishing rate of SiN, but also significantly reduce the polishing rate of TEOS. When the pH is further adjusted to alkaline (9.0), the addition of iron (III) nitrate nine hydrate can still significantly improve the polishing rate of SiN, but has little effect on the polishing rate of TEOS.

[0036] Table 6 Effect of adding cerium (III) nitrate hexahydrate or lanthanum (III) nitrate hexahydrate on polishing effect under different pH conditions

[0037] Table 6 shows the effect of adding cerium (III) nitrate hexahydrate or lanthanum (III) nitrate hexahydrate on the polishing performance of a cerium oxide polishing slurry at different pH conditions. Similarly, at a pH of 3.5, the polishing rate of SiN is inhibited. However, adding cerium (III) nitrate hexahydrate or lanthanum (III) nitrate hexahydrate to the polishing slurry within the pH range of 4.0-9.0 can improve the polishing rate of SiN to a certain extent.

[0038] In summary, the addition of iron (III) nitrate nonahydrate to the cerium oxide polishing liquid of the present invention effectively improves the SiN polishing rate across various pressures (1.5 psi, 2.0 psi, and 3.0 psi), concentration ranges (1-100 ppm), and pH ranges (4.0-9.0), demonstrating a wide operating window. Furthermore, by adjusting the amount of iron (III) nitrate nonahydrate added, varying SiN / TEOS selectivities can be achieved. Furthermore, at a pressure of 3.0 psi, lanthanum (III) nitrate hexahydrate and cerium (III) nitrate hexahydrate also effectively improve the SiN polishing rate across concentration ranges (20-100 ppm) and pH ranges (4.0-9.0).

[0039] It should be noted that the embodiments of the present invention have better practicability and do not impose any form of limitation on the present invention. Any technician familiar with the field may use the technical content disclosed above to change or modify it into an equivalent effective embodiment. However, any modification 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 are still within the scope of the technical solution of the present invention.

Claims

1. A chemical mechanical polishing composition comprising: water; cerium oxide abrasive particles; a trivalent transition metal ion compound.

2. The chemical mechanical polishing composition according to claim 1, wherein The trivalent transition metal ion is iron (III), lanthanum (III) or cerium (III).

3. The chemical mechanical polishing composition according to claim 1, wherein The trivalent transition metal ion compound is iron (III) nitrate nonahydrate, lanthanum (III) nitrate hexahydrate or cerium (III) nitrate hexahydrate.

4. The chemical mechanical polishing composition according to claim 1, wherein The concentration range of the trivalent transition metal ion compound is 1-100 ppm.

5. The chemical mechanical polishing composition according to claim 1, wherein The mass percentage content of the cerium oxide abrasive particles ranges from 0.02% to 0.4%.

6. The chemical mechanical polishing composition according to claim 1, wherein The pH value of the polishing composition ranges from 4.0 to 9.

0.

7. The chemical mechanical polishing composition according to claim 1, characterized in that The polishing composition includes a pH adjuster, and the pH adjuster is selected from an inorganic acid or an inorganic base.

8. The chemical mechanical polishing composition according to claim 7, characterized in that The pH regulator is HNO3 or KOH.

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