Chemical mechanical polishing solution

Abstract

The invention discloses a chemical mechanical polishing solution for flattening a barrier layer. The polishing solution comprises silicon dioxide grinding particles, azole compounds, organic carboxylic acid, alkyl betaine and hydrogen peroxide. The chemical mechanical polishing solution can meet the requirements on the polishing rate and the selection ratio of various materials in the barrier layer polishing process, and can effectively reduce the number of defects on the surface of a polished wafer.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical reagents for semiconductor manufacturing, and particularly to a chemical mechanical polishing liquid. Background Art

[0002] In the manufacture of integrated circuits, the standards for interconnect technologies are increasing. With the increase in the number of interconnect layers and the reduction of process feature sizes, the requirement for the surface flatness of silicon wafers is also getting higher and higher. Without the ability of planarization, it is very limited to create complex and dense structures on semiconductor wafers. The chemical mechanical polishing method CMP is the most effective method to achieve the planarization of the entire silicon wafer.

[0003] The CMP process is to polish the surface of an integrated circuit using a mixture containing abrasives and a polishing pad. In a typical chemical mechanical polishing method, the substrate is directly contacted with the rotating polishing pad, and a load is applied to the back of the substrate. During polishing, the pad and the workbench rotate, and at the same time, a downward force is maintained on the back of the substrate. The abrasive and the chemically active solution (usually called the polishing liquid or polishing slurry) are applied to the pad, and the polishing liquid reacts with the film being polished to start the polishing process.

[0004] At the beginning of the 21st century, the emergence of copper chemical mechanical polishing (Cu CMP) made the 0.13 μm back-end copper process a reality. However, at that time, Cu CMP was relatively simple and only required the polishing of materials such as Cu, Ta, and TEOS. The chemical mechanical polishing process of the copper process is generally divided into three steps. The first step is to use a relatively high down pressure to quickly and efficiently remove a large amount of copper on the substrate surface and leave a certain thickness of copper. The second step is to remove the remaining metallic copper at a lower removal rate and stop at the barrier layer. In the first and second steps, a copper chemical mechanical polishing liquid is used, and after polishing, copper dishing and dielectric layer erosion will occur. The third step is to use a barrier layer polishing liquid to remove the barrier layer, part of the dielectric layer, and metallic copper, repair the copper dishing and dielectric layer erosion generated in the previous two steps, achieve planarization, and reduce surface defects after polishing. Cu CMP has been continuously used until 90 nm, 65 nm, and even today's 5 / 3 nm. The polishing materials are becoming increasingly complex, involving low dielectric constant (low k) materials, ALD barrier layers, Co, Ru, etc.; the polishing requirements are increasing, requiring high uniformity, high flatness, and low defects, etc. Among them, reducing defects is an eternal topic in the CMP process and even the entire chip manufacturing. As the device feature size continues to shrink, the impact of defects on process control and final yield becomes more obvious. The size of fatal defects is required to be at least less than 50% of the device size. CN1400266A discloses an alkaline barrier layer polishing liquid, which contains silica abrasive, amine compounds, and non-ionic surfactants, but this polishing liquid will corrode copper; CN101372089A discloses an alkaline barrier layer polishing liquid, which contains silica abrasive, corrosion inhibitor, oxidant, non-ionic fluorosurfactant, aromatic sulfonic acid oxidant compound, but the polishing rate of the barrier layer of this polishing liquid is relatively low and the yield is low. CN101012356A discloses an acidic barrier layer polishing liquid, which contains oxidant, silica particles partially covered with aluminum, inhibitor, and complexing agent, but this acidic polishing liquid has the defect of serious copper corrosion. The present application aims to provide a barrier layer polishing liquid suitable for copper interconnect processes, which has a high barrier layer removal rate under relatively mild conditions and can well control the surface defect index. Summary of the Invention

[0005] In order to overcome the above technical defects, the present invention provides a barrier layer polishing suitable for copper interconnect processes, which meets the requirements of the removal rate and removal rate selectivity ratio of tantalum (Ta), silicon dioxide (TEOS), copper, and low dielectric materials (BD) in the barrier layer polishing process, and has less pollutant residue after polishing.

[0006] The present invention discloses a chemical mechanical polishing liquid, comprising: silica grinding particles, azole compounds, organic carboxylic acids, alkyl betaines, and hydrogen peroxide.

[0007] Further, the particle size of the silica abrasive particles is 20 to 150 nm, and the mass percentage concentration of the silica abrasive particles is 3 to 15%.

[0008] Further, the azole compound is selected from one or more of benzotriazole, methylbenzotriazole, 5-phenyltetrazole, and benzimidazole, and the mass percentage concentration of the azole compound is 0.01 to 0.2%.

[0009] Further, the organic carboxylic acid is selected from one or more of oxalic acid, malonic acid, citric acid, succinic acid, and tartaric acid, and the mass percentage concentration of the organic acid is 0.1 to 0.5%.

[0010] Further, the alkyl betaine is selected from one or more of dodecyl betaine, tetradecyl betaine, hexadecyl betaine, and octadecyl betaine.

[0011] Further, the mass percentage concentration of the alkyl betaine is 0.005 to 0.05%.

[0012] Further, the concentration of the hydrogen peroxide is 0.1 to 1.5%.

[0013] Further, the pH value of the chemical mechanical polishing liquid is 8 to 12.

[0014] The polishing liquid of the present invention further contains conventional additives such as a bactericide and a pH regulator.

[0015] The present invention controls the surface defects after polishing and reduces the number of surface defects on the polished wafer by adding alkyl betaine, and has no obvious influence on the removal rates of tantalum, copper, silica (TEOS), and low dielectric constant material (BD), meeting the process requirements of barrier layer polishing. Detailed Embodiments

[0016] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the examples described herein.

[0017] Prepare the polishing liquids of Examples 1-8 and the comparative example according to the components and their contents in Table 1. According to the formula given in the table, mix the components other than hydrogen peroxide evenly, adjust the pH value to the required value with KOH or HNO3, and make up the mass percentage to 100% with deionized water. Add hydrogen peroxide before use and mix evenly.

[0018] Table 1 Components and Contents of Examples 1-8 and the Comparative Example (the % all refer to the mass percentage content)

[0019]

[0020] The copper (Cu), tantalum (Ta), silicon dioxide (TEOS), and low-k dielectric material (BD) were polished using the polishing liquid of the comparative example and the polishing liquids of Examples 1-8 of the present invention under the following conditions. Polishing conditions: The polishing machine was a Reflexion LK machine, the polishing pad was a Fujibo H800 pad, the down pressure was 1.5 psi, the rotation speed was platen / polishing head = 93 / 87 rpm, the flow rate of the polishing liquid was 300 ml / min, and the polishing time was 1 min.

[0021] Table 2 Removal rates of copper (Cu), tantalum (Ta), silicon dioxide (TEOS), and low-k dielectric material (BD) for the comparative example and Examples 1-8, and surface roughness and surface contaminants of Cu after polishing

[0022]

[0023] As shown in Table 2: The addition of alkyl betaine greatly improved the surface roughness of Cu after polishing and effectively reduced the number of surface defects. Therefore, using the polishing liquid of the present invention can ensure a better surface finish and flatness of the wafer after polishing without affecting the high removal rates of Ta, TEOS, and BD and the removal rate selectivity, and can meet the requirements of the barrier layer polishing process in the copper interconnect process.

[0024] In the present invention, wt% all refer to mass percentage content.

[0025] It should be noted that the embodiments of the present invention have better implementability and are not any form of limitation to the present invention. Any person skilled in the art may use the disclosed technical content to change or modify it into equivalent effective embodiments. However, as long as it does not depart from the technical solution of the present invention, any modification, equivalent change, or modification made to the above embodiments according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A chemical mechanical polishing liquid, characterized in that, Comprising: Silica abrasive particles, azole compounds, organic carboxylic acids, alkyl betaines and hydrogen peroxide, with a pH value of 8 - 12.

2. The chemical mechanical polishing liquid according to claim 1, wherein, The particle size of the silica abrasive particles is 20 - 150 nm.

3. The chemical mechanical polishing liquid according to claim 1, wherein, The mass percentage concentration of the silica abrasive particles is 3 - 15%.

4. The chemical mechanical polishing liquid according to claim 1, wherein The azole compound is selected from one or more of benzotriazole, methylbenzotriazole, 5-phenyltetrazole, and benzimidazole.

5. The chemical mechanical polishing liquid according to claim 1, wherein The mass percentage concentration of the azole compound is 0.01 - 0.2%.

6. The chemical mechanical polishing liquid according to claim 1, wherein The organic carboxylic acid is selected from one or more of oxalic acid, malonic acid, citric acid, succinic acid, and tartaric acid.

7. The chemical mechanical polishing liquid according to claim 1, characterized in that The mass percentage concentration of the organic carboxylic acid is 0.1 - 0.5%.

8. The chemical mechanical polishing liquid according to claim 1, characterized in that The alkyl betaine is selected from one or more of dodecyl betaine, tetradecyl betaine, hexadecyl betaine, and octadecyl betaine.

9. The chemical mechanical polishing liquid according to claim 1, characterized in that, The mass percentage concentration of the alkyl betaine is 0.005 - 0.05%.

10. The chemical mechanical polishing liquid according to claim 1, wherein The mass percentage concentration of the hydrogen peroxide is 0.1 - 1.0%.

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