Tungsten CMP Slurry pH Control for Oxide Erosion
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Solution Overview
Problem
Current chemical mechanical polishing (CMP) slurries for tungsten in semiconductor manufacturing face challenges in minimizing erosion while maintaining a desirable removal rate, particularly for tungsten lines and arrays of metal lines, which can lead to dishing and erosion issues affecting device performance.
Innovation Solution
The development of CMP slurries comprising abrasive particles, oxidizing agents, and erosion-reducing agents with a pH range of 2 to 14, specifically designed to stabilize the pH between 4 and 12 after the addition of tungsten, incorporating additives such as polyacrylic acid and citric acid to maintain a pH greater than 4, thereby reducing oxide erosion and enhancing tungsten removal rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional CMP slurries are used for tungsten polishing, then tungsten removal rate is achieved, but oxide erosion and dishing occur
Solution Approach 1:
The patent applies parameter changes by carefully controlling the pH of the slurry to be greater than 4, which fundamentally alters the chemical environment during polishing. This pH control modifies the reactivity of the slurry components, reducing oxide erosion while preserving effective tungsten removal. The specific pH parameter adjustment transforms the harmful chemical interactions into a more selective process.
Solution Approach 2:
The patent introduces an intermediary approach by using a slurry composition that mediates between the abrasive action needed for tungsten removal and the chemical reactivity that causes oxide erosion. The slurry acts as an intermediary medium that enables mechanical removal while suppressing harmful chemical etching of the dielectric oxide layer.
2Productivity
If aggressive polishing is used to increase removal rate, then productivity improves, but dishing and erosion worsen
Solution Approach 1:
The patent uses parameter changes by adjusting the slurry pH to greater than 4, which modifies the polishing mechanics and chemistry. This parameter adjustment enables effective material removal while suppressing the dishing effect, maintaining planarity even at higher removal rates. The pH parameter acts as a control variable that decouples removal rate from dishing.
3Productivity
If pH is not controlled, then slurry is more reactive for removal, but oxide erosion increases
Solution Approach 1:
The patent directly applies parameter changes by controlling the pH to be greater than 4, which fundamentally changes the chemical reactivity profile of the slurry. This pH control creates a more selective chemical environment that favors tungsten removal over oxide erosion, effectively decoupling these two processes through chemical parameter management.
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 proposed CMP slurries effectively reduce oxide erosion and maintain high tungsten removal rates, achieving low dielectric polish rates and minimizing dishing, thus improving the planarity and reliability of semiconductor devices.
Implementation Method 1
The polishing composition contacts a first material to be polished and a second material and removes the first material at a higher removal rate than the second material
Implementation Method 2
The CMP slurries comprise abrasive particles, one or more oxidizing agents
Data Source
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AI summary
This invention pertains to slurries, methods and systems that can be used in chemical mechanical planarization (CMP) of tungsten containing semiconductor device. Using the CMP slurries with additives to counter lowering of pH by tungsten polishing byproducts and maintain pH 4 or higher, the erosion of dense metal (such as tungsten) structures can be greatly diminished.