CMP Composition for Selective SiN and Polysilicon Polishing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current polishing compositions for semiconductor substrates face challenges in achieving high removal rates of silicon nitride (SiN) and polysilicon while maintaining selectivity over silicon oxide (SiO), leading to issues like overpolishing or underpolishing, which can result in dishing or incomplete layer removal.
Innovation Solution
A chemical-mechanical polishing composition comprising ceria particles as the abrasive, a cationic polymer, a quaternary ammonium or phosphonium salt, and water, with a pH of about 5 to 8, is used. This composition is applied with a polishing pad and moved relative to the substrate to effectively polish the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional abrasive-containing polishing composition is used, then polishing process is simple, but removal rate of SiN and polysilicon is low and selectivity is insufficient
Solution Approach 1:
The patent changes the chemical parameters of the polishing composition by introducing a cationic polymer with specific molecular weight (10,000-1,000,000 g/mol) and specific cationic monomers (quaternary ammonium or quaternary phosphonium compounds). This chemical parameter change enables the composition to achieve both high removal rates (up to 10x improvement) and high selectivity (up to 100x improvement) for SiN and polysilicon over silicon oxide, resolving the contradiction between productivity and manufacturing precision.
Solution Approach 2:
The patent creates a composite polishing system combining conventional abrasives with a specifically designed cationic polymer. The cationic polymer forms a complex with silicon oxide through electrostatic attraction, while allowing cerium oxide abrasives to effectively remove SiN and polysilicon. This composite approach enables simultaneous achievement of high removal rate and high selectivity that cannot be obtained with conventional single-component polishing compositions.
2Productivity
If conventional polishing composition is used to remove polysilicon and SiN, then process is simple, but dishing occurs due to overpolishing
Solution Approach 1:
The cationic polymer acts as an intermediary substance that selectively interacts with silicon oxide through electrostatic attraction, forming a protective layer that prevents overpolishing. This intermediary mechanism allows the abrasive particles to remove SiN and polysilicon efficiently while the cationic polymer simultaneously protects the silicon oxide stopping layer, thereby preventing dishing and ensuring surface quality reliability.
Solution Approach 2:
By changing the chemical composition parameter to include a cationic polymer with specific molecular weight and cationic monomers, the polishing composition achieves selective interaction with different materials. The cationic polymer specifically binds to silicon oxide while allowing SiN and polysilicon removal, thus controlling the removal rate to prevent overpolishing and maintain surface quality.
3Device complexity
If conventional polishing composition is used, then formulation is simple, but incomplete layer removal occurs
Solution Approach 1:
The patent modifies the chemical parameters by introducing a cationic polymer with specific molecular weight (10,000-1,000,000 g/mol) and specific cationic monomers. This parameter change enhances the polishing composition's ability to remove SiN and polysilicon completely while maintaining simplicity in the overall formulation. The cationic polymer's specific chemical properties enable complete layer removal through enhanced interaction with the materials being removed.
4Productivity
If high removal rate is achieved, then productivity increases, but selectivity for SiN over oxide decreases
Solution Approach 1:
The patent develops a composite polishing system where a cationic polymer (with specific molecular weight and cationic monomers) works synergistically with abrasive particles. The cationic polymer forms electrostatic complexes with silicon oxide, creating a selective interaction that allows high removal rates of SiN and polysilicon while simultaneously protecting oxide layers. This composite material approach resolves the contradiction by enabling both high productivity and high manufacturing precision through the cooperative action of different components.
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 described composition achieves high removal rates for SiN and polysilicon while maintaining selectivity over SiO, reducing the risk of overpolishing or underpolishing, and improving surface planarity and uniformity.
Implementation Method 1
a chemical-mechanical polishing composition comprising (a) an abrasive comprising ceria particles
Implementation Method 2
a cationic polymer selected from a cationic homopolymer, a cationic copolymer comprising at least one cationic monomer and at least one nonionic monomer, and a combination thereof, and (c) a quaternary ammonium salt or a quaternary phosphonium salt
Data Source
AI summary
The invention provides a chemical-mechanical polishing composition comprising (a) an abrasive comprising ceria particles, (b) a cationic polymer selected from a cationic homopolymer, a cationic copolymer comprising at least one cationic monomer and at least one nonionic monomer, and a combination thereof, (c) a quaternary ammonium salt or a quaternary phosphonium salt, and (d) water, wherein the polishing composition has a pH of about 5 to about 8. The invention also provides a method of chemically-mechanically polishing a substrate, especially a substrate comprising silicon oxide, silicon nitride and/or polysilicon by contacting the substrate with the inventive chemical-mechanical polishing composition.