Tungsten CMP Slurry Chemistry for Low Dishing and Erosion
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Solution Overview
Problem
Current Chemical Mechanical Polishing (CMP) processes for semiconductor devices, particularly for tungsten, face challenges in minimizing dishing and erosion while maintaining a desirable removal rate, which are critical for achieving planarity and functionality in metal lines and arrays.
Innovation Solution
The development of a CMP composition comprising an abrasive, an oxidizing agent, and a bicyclic amidine compound, along with a solvent, which is formulated to have a specific pH range and includes additives such as silica, hydrogen peroxide, and ferric nitrate, to reduce dishing and erosion while maintaining high removal rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional CMP processes are used to achieve high removal rates, then productivity is improved, but dishing and erosion increase
Solution Approach 1:
The patent changes the chemical parameters of the CMP slurry by incorporating amidine compounds and controlling pH levels (typically pH 2-5) to optimize the balance between removal rate and surface quality. This chemical parameter adjustment allows high removal rates while minimizing dishing and erosion through controlled tungsten oxidation and dissolution.
Solution Approach 2:
The invention uses composite slurry formulations combining multiple components: abrasives (such as colloidal silica), oxidizing agents (such as hydrogen peroxide), amidine compounds (such as DBU or TBD), and other additives. This composite approach creates synergistic effects where each component contributes to both removal rate and surface quality control.
2Productivity
If aggressive polishing is applied to increase removal rate, then productivity is improved, but surface planarity deteriorates
Solution Approach 1:
The amidine compounds act as intermediary substances that mediate between the aggressive mechanical polishing action and the tungsten surface. These compounds form protective complexes with tungsten oxide, controlling the dissolution rate and preventing excessive material removal from high points, thereby maintaining surface planarity even at high removal rates.
Solution Approach 2:
The patent adjusts chemical parameters including pH control (typically pH 2-5 using buffers), oxidizing agent concentration, and amidine compound dosage to create optimal polishing conditions. These parameter changes enable aggressive mechanical action to be applied without compromising surface planarity, as the chemical environment controls the material removal mechanism.
3Manufacturing precision
If slurry formulation is optimized for low dishing, then manufacturing precision is improved, but removal rate may decrease
Solution Approach 1:
The patent optimizes multiple slurry parameters simultaneously: pH level (typically 2-5), oxidizing agent concentration (such as 1-5% hydrogen peroxide), amidine compound concentration, and abrasive particle characteristics. This multi-parameter optimization ensures that low dishing is achieved through controlled chemistry while maintaining high removal rates through appropriate mechanical abrasion and chemical dissolution balance.
Solution Approach 2:
The invention employs composite slurry formulations that combine abrasives, oxidizing agents, amidine compounds, and other additives in specific ratios. This composite approach allows the slurry to perform multiple functions simultaneously: mechanical abrasion for material removal, chemical oxidation for controlled dissolution, and amidine complexation for dishing prevention, all working together to achieve both precision and productivity.
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 CMP composition effectively reduces dishing and erosion of tungsten structures to below 1000 Angstroms, achieving low corrosion and excellent colloidal stability while maintaining high removal rates, thus improving the planarity and functionality of semiconductor devices.
Implementation Method 1
Removal of tungsten in the CMP is believed to be due to synergy between mechanical abrasion and tungsten oxidation followed by dissolution.
Implementation Method 2
CMP is a process using a combination of chemical and mechanical forces to smooth or planarize surfaces.
Implementation Method 3
The CMP composition comprises an amidine compound, or hydrolyzed derivative thereof, having a structure of: (chemical structure shown)
Data Source
AI summary
This invention pertains to compositions, methods and systems that can be used in chemical mechanical planarization (CMP) of a tungsten containing semiconductor device. CMP slurries comprising bicyclic amidine additives provide low dishing and low erosion topography.