Anionic-Coated Alumina Abrasives for Tungsten CMP Topography
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Solution Overview
Problem
Conventional polishing compositions for tungsten surfaces in semiconductor substrates face issues of high roughness, poor topography, and edge-over-erosion during CMP operations, with silica-based abrasives leading to excessive tungsten removal and alumina-based abrasives having unsuitable removal rates.
Innovation Solution
A chemical-mechanical polishing composition comprising silica and alumina particles, where alumina particles are surface-coated with an anionic polymer, is used to balance material removal rates and minimize erosion, achieving optimized surface topography and planarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If silica-based abrasives are used for tungsten polishing, then material removal rate is improved, but surface roughness increases and topography deteriorates
Solution Approach 1:
The patent uses a composite abrasive system containing both silica particles and alumina particles with different size distributions. The silica particles (0.01-10 μm) provide effective tungsten removal, while the alumina particles (0.01-5 μm) with anionic polymer coating control surface roughness and improve topography. This composite approach allows simultaneous achievement of high removal rate and good surface quality.
Solution Approach 2:
The patent applies local quality by using bimodal or multimodal particle size distributions where different sized particles perform different functions. Larger particles (up to 10 μm) are more effective for bulk material removal, while smaller particles (down to 0.01 μm) are more effective for surface finishing and controlling roughness. The anionic polymer coating on alumina particles specifically targets surface quality improvement.
2Manufacturing precision
If alumina-based abrasives are used for tungsten polishing, then surface topography is improved, but material removal rate decreases
Solution Approach 1:
The patent combines alumina particles with anionic polymer coating (for good topography) with silica particles (for high removal rate). The alumina content is controlled at 1-50 wt% of total abrasive, with silica making up the remainder. This composite formulation allows the alumina to dominate surface quality while silica contributes to removal rate.
Solution Approach 2:
The patent modifies the properties of alumina particles by coating them with anionic polymers and controlling their size distribution (0.01-5 μm). This parameter modification enhances the polishing performance of alumina, making it more effective at controlling surface topography while maintaining compatibility with silica particles for achieving adequate removal rates.
3Productivity
If conventional polishing compositions are used for tungsten CMP, then polishing speed is maintained, but edge-over-erosion occurs
Solution Approach 1:
The patent uses a composite abrasive system with silica and alumina particles in specific ratios, where alumina (1-50 wt%) with anionic polymer coating provides selective polishing that reduces edge-over-erosion. The combination allows maintaining overall polishing speed while the alumina particles preferentially polish tungsten at edges and corners, preventing excessive erosion.
Solution Approach 2:
The patent applies local quality through selective material removal where alumina particles with anionic polymer coating preferentially act on tungsten material at critical locations (edges, corners, and protrusions). This selective action corrects topography issues and reduces edge-over-erosion while silica particles handle bulk material removal, maintaining polishing speed.
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 effectively polishes tungsten surfaces by balancing removal rates of tungsten and silicon oxide, reducing edge-over-erosion and improving surface uniformity.
Implementation Method 1
alumina particles are surface-coated with an anionic polymer
Implementation Method 2
chemical-mechanical polishing composition comprising (a) an abrasive comprising silica particles and alumina particles
Data Source
AI summary
The invention provides a chemical-mechanical polishing composition comprising (a) an abrasive comprising silica particles and alumina particles, wherein the alumina particles are surface-coated with an anionic polymer, and (b) water. The invention also provides a method of chemically mechanically polishing a substrate, especially a substrate comprising tungsten, silicon oxide, and nitride, with the polishing composition.