Chemical mechanical polishing composition

Abstract

According to the cerium oxide chemical mechanical polishing solution, the quaternary ammonium compound is added into the cerium oxide polishing solution, the polishing rate of SiN can be increased to 1.5 times or above, and meanwhile the polishing rate of TEOS is hardly affected. Taking tetrabutyl ammonium hydroxide and benzyltriethylammonium chloride as examples, the content of tetrabutyl ammonium hydroxide and benzyltriethylammonium chloride ranges from 200 ppm to 1000 ppm, the pH value of the polishing solution ranges from 4.0 to 6.0, and the polishing rate of the polishing solution to SiN can be increased.

Description

Technical Field

[0001] The invention relates to a cerium oxide chemical mechanical polishing composition, and more specifically, by adding a quaternary ammonium compound into a cerium oxide polishing liquid, the polishing rate of SiN can be effectively improved while the polishing rate of TEOS is not affected. Background Art

[0002] In the manufacturing process of semiconductor devices, chemical mechanical polishing (CMP) has become the most effective and mature planarization technology. In chemical mechanical polishing solutions based on different abrasives, cerium oxide particles can still provide a higher polishing rate at a lower content, and can also obtain a higher selectivity, which has important application value in CMP. Generally, most chemical mechanical polishing solutions strive to reduce the removal rate of silicon nitride and obtain relatively high removal rates for other materials. For example, in the widely concerned shallow trench isolation (STI) process, silicon nitride (SiN) is used as the termination layer, and the chemical mechanical polishing solution used requires a higher silicon dioxide (TEOS) removal rate.

[0003] However, with the progress of semiconductor etching technology, the oxide line width gradually becomes smaller, and then the chemical mechanical polishing liquid used is expected to have a higher polishing rate for silicon nitride, which is different from the traditional STI selectivity requirement. By adjusting the silicon nitride and silicon dioxide selection ratio, the defects of the oxide circuit on the substrate surface are reduced. To achieve the above goal, 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. Summary of the invention

[0004] The invention discloses a chemical mechanical polishing composition, which comprises: water; cerium oxide abrasive particles; and a quaternary ammonium compound.

[0005] Furthermore, the quaternary ammonium compound is selected from one or more of tetrabutylammonium hydroxide, benzyltriethylammonium chloride and betaine.

[0006] Furthermore, the concentration range of the quaternary ammonium compound is 200ppm-1000ppm.

[0007] Furthermore, the mass percentage content of the cerium oxide abrasive particles ranges from 0.1wt% to 0.5wt%.

[0008] Furthermore, the polishing composition further comprises a pH adjuster, and the pH adjuster is selected from an inorganic acid or an inorganic base, preferably HNO 3 or KOH.

[0009] Furthermore, the pH value of the polishing composition ranges from 4.0 to 6.0.

[0010] The present invention adds quaternary ammonium compounds (including but not limited to tetrabutylammonium hydroxide, benzyltriethylammonium chloride and betaine) to the cerium oxide polishing liquid, which can increase the polishing rate of SiN to more than 1.5 times, while hardly affecting the polishing rate of TEOS. Taking tetrabutylammonium hydroxide and benzyltriethylammonium chloride as examples, their contents range from 200-1000ppm, and the pH of the polishing liquid is within the range of 4.0-6.0, which can achieve the improvement of the polishing rate of the polishing liquid for SiN. Specific embodiments

[0011] 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.

[0012] Embodiment 1

[0013] The raw materials used in this example are all commercially available. According to the ratio of each component in Table 1, each component was dissolved in deionized water, and the mass percentage was supplemented with deionized water to 100%, and HNO 3 Or KOH is used to adjust the pH to 4.5 to obtain the polishing liquids of Comparative Examples 1A-1C and Examples 1D-1F of the present invention.

[0014] Table 1 Components and contents of polishing liquids of Comparative Examples 1A-1C and Examples 1D-1F

[0015]

[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: The TEOS and SiN blank wafers were polished using the polishing liquid prepared above using the polishing instrument and polishing conditions described above. The film thickness measuring instrument was the NanoSpec film thickness measuring system (NanoSpec6100-300, Shanghai Nanospec Technology Corporation). The principle is to measure 49 points at equal intervals on the diameter line starting from 3 mm from the edge of the wafer, and test their polishing rates respectively. The polishing rate of each polishing liquid is the average of the polishing rates at the 49 points.

[0019] Table 2 Polishing rate of the polishing liquid of Comparative Examples 1A-1C and Examples 1D-1F

[0020]

[0021] From the polishing results of Comparative Examples 1A and 1C, it can be seen that although the addition of polyquaternary ammonium salt can improve the polishing rate of SiN under certain polishing pressures (2.0 psi and 3.0 psi), it will significantly inhibit the polishing rate of TEOS. The polishing results of Comparative Example 1A and Examples 1D and 1E show that both tetrabutylammonium hydroxide and benzyltriethylammonium chloride can effectively improve the polishing rate of SiN, which can be increased to about 1.5 times or more, while having little effect on the polishing rate of TEOS.

[0022] The polishing results of Comparative Example 1B and Example 1F show that betaine, as a zwitterionic compound containing quaternary ammonium cations, can also effectively improve the polishing rate of silicon nitride, while having almost no effect on the polishing rate of TEOS. This shows that although betaine is a zwitterionic compound, the quaternary ammonium cation plays a major role, and the carboxyl anion at the other end does not adsorb on the SiN surface to inhibit its polishing rate.

[0023] 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.

[0024] Embodiment 2

[0025] According to the ratio of each component in Table 3, each component was dissolved in deionized water, and the mass percentage was supplemented to 100% with deionized water. 3 Or KOH is used to adjust the pH to 4.5 to obtain the polishing solutions of Comparative Examples 2A-2C and Examples 2D-2Q. The polishing solutions prepared above are used for chemical mechanical polishing of TEOS and SiN blank wafers, respectively, and the polishing effects are compared. The results are shown in Table 3.

[0026] The polishing conditions are as follows: 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 2.0 psi, the polishing liquid flow rate is 150 mL / min, and the polishing time is 60 s. The film thickness measuring instrument is the NanoSpec film thickness measuring system.

[0027] Table 3 Effect of adding different contents of quaternary ammonium compounds on polishing effect

[0028]

[0029] 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, and will not significantly inhibit the polishing rate of TEOS. However, when its content is further increased to 1500ppm, the polishing rate of SiN will be inhibited. When betaine (500 or 1000ppm) is added, the result that the SiN rate is improved and 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 inhibit the polishing rate of TEOS while improving the polishing rate of SiN.

[0030] Embodiment 3

[0031] According to the ratio of each component in Table 4, each component was dissolved in deionized water, and the mass percentage was supplemented to 100% with deionized water. 3 Or KOH to adjust pH to different values, to obtain the corresponding comparative example and example polishing liquid. The polishing liquid prepared above was used for chemical mechanical polishing of TEOS and SiN blank wafers, and the polishing effects were compared. The results are shown in Table 4.

[0032] The polishing conditions are as follows: 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 2.0 psi, the polishing liquid flow rate is 150 mL / min, and the polishing time is 60 s. The film thickness measuring instrument is the NanoSpec film thickness measuring system.

[0033] Table 4 Effect of adding quaternary ammonium compounds on polishing effect under different pH conditions

[0034]

[0035]

[0036] 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, the polishing rate of SiN can be improved in the pH range of 4.0-6.0.

[0037] In summary, the present invention adds quaternary ammonium compounds to the cerium oxide polishing liquid to improve the polishing rate of the polishing liquid on 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.

[0038] 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, include: water; Cerium oxide abrasive particles; Quaternary ammonium compounds.

2. The chemical mechanical polishing composition according to claim 1, It is characterized in that 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, It is characterized in that 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, It is characterized in that 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, It is characterized in that 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, It is characterized in that The pH regulator is HNO 3 or KOH.

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

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