Ceria CMP Composition for Selective SiN and Polysilicon Removal
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Solution Overview
Problem
Current chemical-mechanical polishing compositions for semiconductor manufacturing lack high removal rates and selective removal of silicon nitride (SiN) over silicon oxide, leading to issues like dishing and incomplete layer removal, which affect device fabrication and performance.
Innovation Solution
A chemical-mechanical polishing composition comprising ceria particles with an average size of 60 nm to 120 nm, a cationic polymer, a quaternary ammonium or phosphonium salt, and water, with a pH of 5 to 8, is used to selectively polish SiN and polysilicon while minimizing silicon oxide removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional abrasive-containing polishing compositions are used, then silicon oxide polishing is achieved, but silicon nitride and polysilicon removal rates are insufficient leading to overpolishing or underpolishing
Solution Approach 1:
The patent changes the chemical parameters of the polishing composition by using ceria particles instead of conventional abrasives, and by controlling pH in the range of 2-9. This parameter change enables high removal rates for silicon nitride and polysilicon while maintaining selectivity over silicon oxide, resolving the contradiction between productivity and manufacturing precision
Solution Approach 2:
The patent employs a composite polishing system consisting of ceria particles combined with specific additives including cationic polymers, chelating agents, and surfactants. This composite material approach enhances the chemical-mechanical polishing action to achieve both high removal rates and selective removal of silicon nitride over silicon oxide
2Productivity
If high removal rates for SiN and polysilicon are achieved, then throughput is improved, but selectivity for SiN over SiO is reduced leading to oxide layer damage
Solution Approach 1:
The patent introduces chelating agents and surfactants as intermediary substances that mediate between the ceria abrasive and the dielectric layers. These intermediaries enhance the chemical reactivity toward silicon nitride and polysilicon while protecting the silicon oxide layer, allowing high throughput without oxide damage
Solution Approach 2:
By adjusting pH to ranges of 2-9 and optimizing ceria particle size distribution, the patent creates optimal chemical conditions that accelerate SiN and polysilicon removal while maintaining oxide layer integrity, thus improving throughput without causing harmful effects
3Object-affected harmful factors
If low to moderate polishing rates are used to maintain selectivity, then oxide layer integrity is preserved, but throughput is limited
Solution Approach 1:
The patent fundamentally changes the polishing parameters by using ceria particles with specific size distributions and controlling pH at 2-9, which transforms the polishing mechanism to achieve both high removal rates and high selectivity simultaneously, eliminating the need to trade off throughput for oxide layer protection
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 composition achieves higher removal rates for SiN and polysilicon while maintaining low removal rates for silicon oxide, improving substrate planarity and selectivity, thus enhancing semiconductor device fabrication quality and performance.
Implementation Method 1
The invention provides a chemical-mechanical polishing composition comprising (a) an abrasive comprising ceria particles
Implementation Method 2
chemical-mechanical polishing composition
Implementation Method 3
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
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.