Cobalt CMP Slurry Composition for Corrosion and Dishing Control
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Solution Overview
Problem
Current CMP slurries designed for copper and tungsten cause unacceptable corrosion and defects in cobalt layers due to cobalt's chemical fragility, leading to etching and device failure.
Innovation Solution
A polishing slurry concentrate comprising a synergistic combination of an anionic surfactant with phosphate groups and benzotriazole derivatives, along with selected abrasives and cobalt removal rate enhancers, is used to form a point-of-use slurry that protects cobalt while achieving high removal rates for other materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional slurries with silica particles and tartaric acid are used for cobalt CMP, then the slurry can perform basic polishing, but it causes excessive dishing and fails to achieve desired surface flatness
Solution Approach 1:
The patent changes the chemical parameters of the slurry by replacing tartaric acid with gluconic acid and adjusting particle size distribution. This chemical parameter change fundamentally alters the interaction between slurry and cobalt surface, reducing dishing while maintaining polishing effectiveness and achieving desired surface flatness.
Solution Approach 2:
The patent uses a composite abrasive system combining sub-10nm and sub-25nm particles with gluconic acid. This composite material approach creates synergistic effects where the multi-component slurry formulation achieves both effective material removal and controlled surface morphology, preventing excessive dishing.
2Manufacturing precision
If sub-10nm particles are used to achieve fine surface finish, then surface quality improves, but the polishing rate decreases
Solution Approach 1:
The patent segments the abrasive particle size distribution into multiple ranges (sub-10nm and sub-25nm particles). This segmentation allows different particle sizes to perform different functions: finer particles provide surface finishing while coarser particles contribute to material removal, thereby maintaining both high surface quality and acceptable polishing rate.
Solution Approach 2:
The patent optimizes the concentration and size distribution parameters of abrasive particles in the slurry. By carefully controlling particle concentration and size distribution, the slurry achieves enhanced polishing rate while maintaining fine surface finish quality through the synergistic action of multiple particle sizes.
3Productivity
If slurry formulations are optimized for high polishing rate, then productivity improves, but control over surface morphology and dishing worsens
Solution Approach 1:
The patent optimizes multiple slurry parameters simultaneously: chemical composition (gluconic acid instead of tartaric acid), particle size distribution (bimodal distribution of sub-10nm and sub-25nm particles), and concentrations. This multi-parameter optimization enables the slurry to achieve high polishing rate while maintaining excellent control over surface morphology and minimizing dishing.
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 slurry effectively reduces cobalt corrosion, minimizes defects like dishing and edge of erosion, and maintains optimal removal rates for common wafer materials like TEOS, while ensuring low etch rates and precise material interface management.
Implementation Method 1
Chemical mechanical polishing (CMP) is a planarization process that utilizes a slurry and a polishing pad to remove material from a substrate
Implementation Method 2
The slurry of the present disclosure has been found to be particularly useful for polishing cobalt and cobalt alloy barriers
Data Source
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AI summary
A slurry that polishes surfaces or substrates which includes cobalt. The slurry further comprises an anionic and/or cationic surfactant, each of which has a phosphate group, a long chain alkyl group, or both. The slurry also includes a corrosion inhibitor, abrasives, removal rate enhancers, solvents, pH adjustors, and chelating agents. The pH of the slurry is preferably 8 or higher.