CMP Polishing Agent Copolymer for STI Flatness
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Solution Overview
Problem
Current polishing agents for Chemical Mechanical Polishing (CMP) in semiconductor manufacturing, particularly in Shallow Trench Isolation (STI), fail to achieve a high selection ratio between silicon dioxide and silicon nitride films, leading to unsatisfactory flatness due to inadequate control over the removal rate of silicon nitride films.
Innovation Solution
A polishing agent comprising a water-soluble polymer copolymer of unsaturated dicarboxylic acid or its derivatives, cerium oxide particles, and water, with a pH of 4 to 9, is used to control the removal rates, ensuring a high selection ratio and flatness by maintaining a low removal rate for silicon nitride films while maintaining a high removal rate for silicon dioxide films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional polishing agents containing polyacrylic acid or ammonium polyacrylate are used, then the removal rate of silicon dioxide film can be maintained at a high value, but the removal rate of silicon nitride film is not sufficiently controlled, resulting in low selection ratio
Solution Approach 1:
The invention changes the chemical composition parameters of the polishing agent by replacing conventional polyacrylic acid or ammonium polyacrylate with a specific copolymer containing unsaturated dicarboxylic acid units and non-acidic ethylenic double bond monomer units. This parameter change in polymer structure enables differential removal rates, achieving high selection ratio while maintaining adequate silicon dioxide removal rate
Solution Approach 2:
The invention uses a composite polishing agent formulation combining cerium oxide particles with a specifically designed copolymer. The composite material approach allows the cerium oxide to provide mechanical abrasion for silicon dioxide removal while the copolymer chemically interacts with silicon nitride to suppress its removal rate, thereby achieving both high productivity and high manufacturing precision
2Productivity
If the removal rate of silicon nitride film is increased to improve polishing efficiency, then the overall polishing speed improves, but the flatness of the base material becomes unsatisfactory due to insufficient control over silicon nitride removal
Solution Approach 1:
The invention modifies the chemical parameters of the polishing system by introducing a copolymer with specific functional groups that selectively interact with silicon nitride. This parameter change enables independent control of silicon nitride removal rate, allowing high polishing efficiency to be achieved without compromising flatness control
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively achieves a high selection ratio and good flatness by controlling the removal rates, ensuring efficient polishing in CMP processes, particularly in STI, by using a water-soluble polymer copolymer and cerium oxide particles within a specific pH range.
Implementation Method 1
the polishing agent contains, as an abrasive grain, a cerium oxide particle
Implementation Method 2
a water-soluble polymer including a copolymer of a monomer (A) which includes at least one member selected from the group consisting of an unsaturated dicarboxylic acid, a derivative thereof, and salts of the unsaturated dicarboxylic acid and the derivative thereof and a monomer (B) other than the monomer (A), including an ethylenic double bond and no acidic group
Data Source
AI summary
The present invention relates to a polishing agent including: a water-soluble polymer including a copolymer of a monomer (A) which includes at least one member selected from the group consisting of an unsaturated dicarboxylic acid, a derivative thereof, and salts of the unsaturated dicarboxylic acid and the derivative thereof and a monomer (B) other than the monomer (A), comprising an ethylenic double bond and no acidic group; a cerium oxide particle; and water, in which the polishing agent has a pH of 4 to 9.