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, benzotriazole and derivatives thereof, Tween, organic carboxylic acid, hydrogen peroxide and water. The chemical mechanical polishing solution can meet the requirements for the polishing rate and the selection ratio of various materials in the barrier layer polishing process, and has high metal corrosion control capacity and pattern surface appearance correction capacity.

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 manufacturing of integrated circuits, the standards of interconnect technology 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 a rotating polishing pad, and a load is applied to the back of the substrate. During polishing, the pad and the workbench rotate, while a downward force is maintained on the back of the substrate, and an abrasive and a chemically active solution (usually called a polishing liquid or a polishing slurry) are applied to the pad. 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 at a high removal rate 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. The first and second steps use copper chemical mechanical polishing fluid, which will cause dishing of copper and erosion of the dielectric layer after polishing. The third step is to use the barrier layer polishing fluid to remove the barrier layer, part of the dielectric layer, and metallic copper, repair the dishing of copper and the erosion of the dielectric layer generated in the previous two steps, achieve planarization, and reduce the 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 getting higher and higher, which require 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 the final yield becomes more and more obvious. The size of fatal defects is required to be at least less than 50% of the device size. Among them, copper corrosion is a common and intractable defect, which poses a challenge to the chemical mechanical polishing process, especially the chemical mechanical polishing process under acidic conditions. The present invention aims to provide an acidic barrier layer polishing fluid suitable for the copper interconnect process, which not only has a high barrier layer removal rate, but also can prevent local and overall corrosion during copper polishing and can well control the dishing of copper. Summary of the Invention

[0005] In order to overcome the above technical defects, the object of the present invention is to provide a chemical mechanical polishing fluid, comprising: silica abrasive particles, benzotriazole and its derivatives, Tween, organic carboxylic acid, and an oxidant, and the pH value is 2-4. The chemical mechanical polishing fluid of the present invention not only has a high barrier layer removal rate, but also can prevent local and overall corrosion of copper during polishing and can well control the dishing of copper.

[0006] Further, the particle size of the silica abrasive particles is 20-150 nm; the mass percentage concentration of the silica abrasive particles is 3-15%.

[0007] Further, the benzotriazole and its derivatives are benzotriazole and methylbenzotriazole; the mass percentage concentration of the benzotriazole and its derivatives is 0.05-0.2%.

[0008] Further, the organic carboxylic acid is selected from one or more of oxalic acid, malonic acid, citric acid, succinic acid and tartaric acid; the mass percentage concentration of the organic acid is 0.1-0.5%.

[0009] Further, the Tween is Tween 20, Tween 21, Tween 40, Tween 60, Tween 61, Tween 80, Tween 81 and Tween 85; the mass percentage concentration of the Tween is 0.001-0.05%.

[0010] Further, the concentration of the hydrogen peroxide is 0.1-1.0%.

[0011] Further, the pH value of the chemical mechanical polishing composition is 2-4.

[0012] The polishing liquid of the present invention may further contain conventional additives such as bactericides and pH regulators.

[0013] The acidic polishing liquid provided by the present invention effectively prevents corrosion during metal polishing through the compounding of benzotriazole and its derivatives with Tween, and has a good corrective ability for the dish-shaped depression caused after copper polishing. Specific Embodiments

[0014] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples.

[0015] Prepare the polishing liquids of Examples 1-8 and Comparative Examples 1-3 according to the components and their contents in Table 1. According to the given formula in the table, mix the other components except hydrogen peroxide evenly, and make up the mass percentage to 100% with deionized water. Adjust to the required pH value with KOH or HNO3. Add hydrogen peroxide before use and mix evenly.

[0016] Table 1 Formulas of Examples 1-8 and Comparative Examples 1-3 (the % all refer to mass percentage content)

[0017]

[0018] Polish copper (Cu), tantalum (Ta), silicon dioxide (TEOS) and low-k dielectric material (BD) using the polishing liquids of Comparative Examples 1-3 and Examples 1-8 under the following conditions. Polishing conditions: The polishing machine is a Reflexion LK machine, the polishing pad is a Fujibo H800 pad, the down pressure is 1.5 psi, the rotation speed is the polishing platen / polishing head = 93 / 87 rpm, the flow rate of the polishing liquid is 300 ml / min, and the polishing time is 1 min.

[0019] Immerse the Cu wafers in the polishing liquids of Comparative Examples 1-3 and Examples 1-8 for 30 min and then test the static corrosion rate.

[0020] Table 2 Removal rates of copper (Cu), tantalum (Ta), TEOS, and low-k dielectric material (BD), and Cu static corrosion rate for Comparative Examples 1-3 and Examples 1-8

[0021]

[0022] The results are shown in Table 2: Compared with Comparative Examples 1-3, the compounding of benzotriazole and Tween can effectively reduce the Cu static corrosion rate, ensuring that Cu will not be corroded during the polishing process while not affecting the high removal rates of Ta, TEOS, and BD.

[0023] Furthermore, in order to characterize the influence of the polishing liquid in this application on the surface topography of the wafer, Comparative Examples 1-3 and Examples 1-2 were used to polish the patterned copper wafer according to the following conditions.

[0024] The graphic chip is a commercially available 12-inch Sematech754 graphic chip, and the film layer materials from top to bottom are copper / tantalum / tantalum nitride / TEOS.

[0025] The polishing process is divided into three steps. In the first step, a commercially available copper polishing liquid is used to remove most of the copper; in the second step, a commercially available copper polishing liquid is used to remove the remaining copper; in the third step, the barrier layer polishing liquid of the present invention is used to remove the barrier layer (tantalum / tantalum nitride) and part of the TEOS and stop on the TEOS layer.

[0026] Polishing conditions: The polishing machine is a Reflexion LK machine, the polishing pad is a Fujibo H800 pad, the down pressure is 1.5 psi, the rotation speed is polishing disc / polishing head = 93 / 87 rpm, the polishing liquid flow rate is 300 ml / min, and the polishing time is 70 s.

[0027] Table 3 Comparison of the corrective ability of the polishing compositions of Comparative Examples 1-3 and Examples 1-2 after polishing the patterned copper wafer

[0028]

[0029] Among them, the dish-shaped depression mentioned above refers to the dish-shaped depression on the metal pad before barrier layer polishing, and the dielectric layer erosion refers to the dielectric layer erosion of the barrier layer in the dense line area with a line width of 0.18 microns and a density of 50% (50% copper / 50% dielectric layer).

[0030] According to the data in Table 2, compared with Comparative Examples 1-3, in the polishing liquid of Examples 1-2, the compounding of benzotriazole and its derivatives with Tween can better correct the dish-shaped depression and dielectric layer erosion generated on the wafer during the previous process (after copper polishing) under acidic conditions, so that the polished copper wafer can obtain a better crystal morphology.

[0031] It should be understood that the wt% mentioned in the present invention all refer to the mass percentage content.

[0032] It should be noted that the embodiments of the present invention have better implementability and do not impose any form of limitation on the present invention. Any person skilled in the art may use the technical content disclosed above 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 based on 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, Including: Silica grinding particles, benzotriazole and its derivatives, Tween, organic carboxylic acid and hydrogen peroxide, with a pH value of 2 - 4.

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

3. The chemical mechanical polishing liquid according to claim 1, characterized in that, The mass percentage concentration of the silica grinding particles is 3 - 15%.

4. The chemical mechanical polishing liquid according to claim 1, wherein The benzotriazole and its derivatives are benzotriazole and methylbenzotriazole.

5. The chemical mechanical polishing liquid according to claim 1, wherein The mass percentage concentration of the benzotriazole and its derivatives is 0.05 - 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, wherein The mass percentage concentration of the organic acid is 0.1 - 0.5%.

8. The chemical mechanical polishing liquid according to claim 1, wherein The Tween is selected from Tween 20, Tween 21, Tween 40, Tween 60, Tween 61, Tween 80, Tween 81 and Tween 85.

9. The chemical mechanical polishing liquid according to claim 1, wherein The mass percentage concentration of the Tween is 0.001 - 0.05%.

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

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