Chemical mechanical polishing composition

Abstract

The present invention is intended to provide a cerium-oxide chemical mechanical polishing solution. Adding a quaternary ammonium compound to a cerium-oxide polishing solution can increase the polishing rate of SiN to 1.5 times or more, and the polishing rate of TEOS is virtually unaffected. By taking tetrabutylammonium hydroxide and benzyltriethylammonium chloride as an example, the content of which is 200-1,000 ppm, a pH of the polishing solution in the range of 4.0-6.0 can improve the polishing rate of the polishing solution for SiN.

Description

A chemical mechanical polishing composition Technical Field

[0001] The present invention relates to a cerium oxide chemical mechanical polishing composition. More specifically, by adding a quaternary ammonium compound to a cerium oxide polishing solution, the polishing rate of SiN can be effectively improved without affecting the polishing rate of TEOS. Background Art

[0002] Chemical mechanical polishing (CMP) has become the most effective and mature planarization technology in semiconductor device manufacturing. 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 valuable 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 the advancement of semiconductor etching technology, the oxide line width gradually becomes smaller, and it is then expected that the chemical mechanical polishing liquid used also has a higher polishing rate for silicon nitride, which is different from the traditional STI selectivity requirement. By adjusting the silicon nitride and silicon dioxide selectivity ratio, the defects of the oxide circuit on the substrate surface are reduced. To achieve the above goals, some studies (such as CN102046743B, US200690047870A1) have proposed adding some polymers / copolymers to the cerium oxide polishing liquid to improve the polishing rate of SiN, but this type of polymer additive has a significant inhibitory effect on the polishing rate of TEOS. The present invention adds quaternary ammonium compounds to the cerium oxide polishing liquid, which can effectively improve the polishing rate of SiN while having almost no effect on the polishing rate of TEOS.

[0004] Summary of the Invention

[0005] The invention discloses a chemical mechanical polishing composition, which comprises: water; cerium oxide abrasive particles; and a quaternary ammonium compound.

[0006] Furthermore, the quaternary ammonium compound is selected from one or more of tetrabutylammonium hydroxide, benzyltriethylammonium chloride and betaine.

[0007] Furthermore, the concentration range of the quaternary ammonium compound is 200ppm-1000ppm.

[0008] Furthermore, the mass percentage content of the cerium oxide abrasive particles ranges from 0.1 wt% to 0.5 wt%.

[0009] 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.

[0010] Furthermore, the pH value of the polishing composition ranges from 4.0 to 6.0.

[0011] The present invention adds quaternary ammonium compounds (including but not limited to tetrabutylammonium hydroxide, benzyltriethylammonium chloride, and betaine) to a cerium oxide polishing solution, increasing the SiN polishing rate by more than 1.5 times while barely affecting the TEOS polishing rate. For example, tetrabutylammonium hydroxide and benzyltriethylammonium chloride, when present in a range of 200-1000 ppm and a polishing solution pH of 4.0-6.0, can both improve the SiN polishing rate. Specific embodiments

[0012] In order to better understand the technical solution of the present invention, the following examples will further illustrate the method provided by the present invention, but the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the claims of the present invention.

[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 adjusted to 4.5 with 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 Comparative Examples 1A-1C and Examples 1D-1F

[0016] In order to further measure the polishing performance of the polishing solutions of Examples 1D-1F and Comparative Examples 1A-1C in Table 1, the polishing rates of the polishing solutions in Table 1 on TEOS wafers and SiN wafers were measured respectively. The results are shown in Table 2.

[0017] Polishing conditions: the polishing machine is Mirra, the polishing pad is IC1000, 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 150 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 the polishing solutions of Comparative Examples 1A-1C and Examples 1D-1F

[0020] The polishing results of Comparative Examples 1A and 1C show that while the addition of polyquaternium salts can increase the SiN polishing rate at certain polishing pressures (2.0 psi and 3.0 psi), it significantly inhibits the TEOS polishing rate. The polishing results of Comparative Example 1A and Examples 1D and 1E demonstrate that both tetrabutylammonium hydroxide and benzyltriethylammonium chloride can effectively increase the SiN polishing rate by more than approximately 1.5 times, while having little effect on the TEOS polishing rate.

[0021] The polishing results of Comparative Example 1B and Example 1F demonstrate that betaine, a zwitterionic compound containing quaternary ammonium cations, can also effectively improve the polishing rate of silicon nitride while having little effect on the polishing rate of TEOS. This demonstrates that although betaine is a zwitterionic compound, the primary effect is the quaternary ammonium cation, and the carboxyl anion at the other end does not adsorb on the SiN surface to inhibit its polishing rate.

[0022] In summary, adding quaternary ammonium compounds to the cerium oxide polishing solution can effectively improve the polishing rate of SiN and will not inhibit the polishing rate of TEOS.

[0023] Example 2

[0024] According to the proportions of the components in Table 3, each component was dissolved in deionized water, and the weight 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 Examples 2A-2C and Examples 2D-2Q. 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 3.

[0025] 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, 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.

[0026] Table 3 Effect of adding different amounts of quaternary ammonium compounds on polishing effect

[0027] Table 3 shows the effect of adding different amounts of quaternary ammonium compounds on the polishing effect of cerium oxide polishing liquid. It can be seen that when the content of added tetrabutylammonium hydroxide is 100ppm, the polishing rate of SiN is not significantly improved. When the content of added tetrabutylammonium hydroxide is higher than 200ppm, the polishing rate of SiN is significantly improved. In addition, the polishing rate of SiN does not gradually increase with the increase of the amount of tetrabutylammonium hydroxide added. In the content range of 200-1000ppm, its polishing rate always remains at This shows that adding a certain amount of tetrabutylammonium hydroxide (200ppm) can have a good effect on improving the polishing rate of SiN. At the same time, even if the addition amount is increased to 1000ppm, the polishing rate of TEOS is almost unaffected. Similarly, when benzyltriethylammonium chloride is added, compared with Comparative Example 2A, its content in the range of 200-1000ppm can also effectively improve the polishing rate of SiN, while not significantly suppressing the polishing rate of TEOS. However, when its content is further increased to 1500ppm, the polishing rate of SiN will be suppressed. When betaine (500 or 1000ppm) is added, the result that the SiN rate is improved while the TEOS rate is not significantly affected can also be obtained. In summary, unlike polyquaternary ammonium compounds, the addition of quaternary ammonium compounds will not significantly suppress the polishing rate of TEOS while improving the polishing rate of SiN.

[0028] Example 3

[0029] According to the proportions of the components listed in Table 4, each component was dissolved in deionized water, and the weight percentage was adjusted to 100% with deionized water. The pH was adjusted to different values ​​with HNO3 or KOH to obtain the corresponding polishing solutions of the comparative examples and examples. 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.

[0030] 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, 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.

[0031] Table 4 Effect of adding quaternary ammonium compounds on polishing effect under different pH conditions

[0032] Table 4 shows the effect of adding tetrabutylammonium hydroxide or benzyltriethylammonium chloride on the polishing effect of cerium oxide polishing solution under different pH conditions. The polishing results of Comparative Examples 3A-3C show that when the pH is 3.5, the polishing rate of SiN is suppressed. When the pH is adjusted to 4.0 or 4.5, the addition of tetrabutylammonium hydroxide or benzyltriethylammonium chloride can effectively improve the polishing rate of SiN. As the pH gradually increases to 6.0, the effect of tetrabutylammonium hydroxide or benzyltriethylammonium chloride on the polishing rate of SiN will gradually weaken. In summary, taking tetrabutylammonium hydroxide and benzyltriethylammonium chloride as examples, they can improve the polishing rate of SiN in the pH range of 4.0-6.0.

[0033] In summary, the present invention adds a quaternary ammonium compound to the cerium oxide polishing liquid to improve the polishing rate of the polishing liquid for SiN, while having almost no effect on the polishing rate of TEOS, thereby overcoming the problem that polyquaternary ammonium salts will inhibit the polishing rate of TEOS.

[0034] 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; Quaternary ammonium compounds.

2. The chemical mechanical polishing composition according to claim 1, wherein The quaternary ammonium compound is selected from one or more of tetrabutylammonium hydroxide, benzyltriethylammonium chloride and betaine.

3. The chemical mechanical polishing composition according to claim 1, wherein The concentration of the quaternary ammonium compound is in the range of 200 ppm to 1000 ppm.

4. The chemical mechanical polishing composition according to claim 1, wherein The mass percentage content of the cerium oxide abrasive particles is in the range of 0.1 wt % to 0.5 wt %.

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

6. The chemical mechanical polishing composition according to claim 5, characterized in that The pH regulator is HNO3 or KOH.

7. The chemical mechanical polishing composition according to claim 1, characterized in that The pH value of the polishing composition ranges from 4.0 to 6.0.

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