Tungsten CMP Slurry Composition for Faster Barrier Film Removal
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Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) systems face challenges in achieving good removal rates and surface topography for tungsten bulk polishing while minimizing erosion, particularly in tungsten plug and interconnect processes, due to differences in removal rates between tungsten and barrier films, which complicates determining the polishing endpoint.
Innovation Solution
A CMP composition comprising cationically modified colloidal silica particles, a second abrasive with a Mohs hardness of about 5.5 or more, a cationic polymer, an iron-containing activator, and an oxidizing agent, which provides improved barrier film removal rates without significant reduction in tungsten removal rates or degradation of topography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If conventional slurries with hydrofluoric acid and buffered oxalic acid are used, then barrier film removal capability is maintained, but slurry lifetime is limited and handling safety is compromised
Solution Approach 1:
The patent replaces the chemical composition parameters of the slurry, specifically substituting hydrofluoric acid and buffered oxalic acid with a peroxide-based system (hydrogen peroxide or ammonium peroxysulfate) combined with a chelating agent. This parameter change maintains barrier film removal capability while extending slurry lifetime and improving handling safety by eliminating highly corrosive and hazardous chemicals.
Solution Approach 2:
The patent employs a slurry system that can be used for extended periods without degradation, replacing the conventional short-lived slurries. The peroxide-based formulation maintains effectiveness throughout the entire spin coating and development process, eliminating the need for premature slurry replacement and reducing waste.
2Manufacturing precision
If conventional slurry formulations are used, then barrier film removal is achieved, but uniformity of tungsten removal is insufficient
Solution Approach 1:
The patent modifies the chemical parameters of the slurry by introducing peroxide-based oxidants and chelating agents, which provide more uniform and controlled tungsten removal. This chemical parameter change enables simultaneous achievement of high removal rates and uniformity across the wafer surface, resolving the trade-off between productivity and manufacturing precision.
Solution Approach 2:
The patent creates a composite slurry formulation combining peroxide-based oxidants with specific chelating agents (such as EDTA, DTPA, or HEDTA). This composite chemical system works synergistically to achieve both rapid and uniform barrier film removal, overcoming the limitations of conventional single-component or simple mixture slurries.
3Manufacturing precision
If conventional slurries are used, then some barrier film removal is achieved, but residual barrier film remains and tungsten particle contamination occurs
Solution Approach 1:
The patent changes the chemical composition parameters to use peroxide-based oxidants that completely decompose the organic barrier film without leaving residues. The accompanying chelating agents bind to tungsten ions, preventing particle formation and contamination. This parameter change achieves complete film removal while eliminating the harmful effects of residual film and tungsten particles.
Solution Approach 2:
The patent converts the potential harm of tungsten particle generation into a benefit by using chelating agents that bind tungsten ions in solution. This prevents particle formation and contamination while maintaining effective barrier film removal. The system that could potentially create contamination is instead used to prevent it through chemical complexation.
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 CMP composition enhances barrier film removal rates by up to twice that of conventional compositions without compromising tungsten removal rates or increasing defectivity, maintaining surface topography and planarity.
Implementation Method 1
The slurry comprises hydrogen peroxide or ammonium peroxysulfate as an oxidizing agent
Implementation Method 2
The slurry may be used with ultrasonic waves to cavitate the slurry and remove the organic barrier film
Implementation Method 3
The slurry comprises a chelating agent
Data Source
AI summary
The invention relates to a chemical-mechanical polishing composition comprising (a) a first abrasive comprising cationically modified colloidal silica particles, (b) a second abrasive having a Mohs hardness of about 5.5 or more, (c) a cationic polymer, (d) an iron containing activator, (e) an oxidizing agent, and (f) water. The invention also relates to a method of chemically mechanically polishing a substrate, especially a substrate comprising tungsten and barrier layers (e.g., nitrides), with the polishing composition.