CMP Slurry Polymer for Silicon Wafer Edge Roll-Off Reduction
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Solution Overview
Problem
Current semiconductor substrate polishing technologies face challenges in achieving enhanced surface flatness and reduced edge roll-off in silicon wafers, leading to increased product costs and yield reduction due to uneven surface pressure and polishing rate variations near the edges.
Innovation Solution
A slurry composition incorporating a water-soluble polymer with specific solubility parameters and molecular weights, containing hetero atoms, is used to selectively lower the polishing rate near the edges of silicon wafers, thereby reducing edge roll-off and improving surface flatness without compromising the overall polishing rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CMP is used with uniform polishing conditions, then overall polishing rate is maintained, but edge roll-off occurs and surface flatness deteriorates
Solution Approach 1:
The patent applies local quality by adding a water-soluble polymer to the slurry that selectively accumulates at the edge region of the silicon wafer during polishing. This creates a localized modification of polishing conditions at the edges, where the polymer forms a protective layer that reduces the polishing rate specifically in the edge region (within 1mm from the outer edge), thereby preventing roll-off and improving surface flatness without significantly affecting the overall polishing productivity
Solution Approach 2:
The patent changes the chemical composition parameter of the polishing slurry by incorporating a water-soluble polymer with specific molecular weight (10,000 to 1,000,000) and solubility parameter (9.0 to 14.0). This parameter change causes the polymer to selectively adsorb at the edge region under the influence of centrifugal force and capillary action, thereby locally modifying the polishing rate parameter at the edges while maintaining the overall polishing process efficiency
2Manufacturing precision
If polishing pressure is increased to improve surface quality, then surface flatness improves, but edge roll-off is exacerbated due to uneven pressure distribution
Solution Approach 1:
The patent addresses the uneven pressure distribution by applying local quality through selective polymer accumulation at the edge region. The water-soluble polymer forms a protective layer specifically where the pressure is highest (at the edges), creating a localized counterbalancing effect that prevents the polish from removing too much material at the edges, thereby correcting the shape distortion without reducing the overall polishing pressure
3Manufacturing precision
If slurry composition is modified to reduce edge roll-off, then surface flatness improves, but polishing rate may be compromised
Solution Approach 1:
The patent resolves this contradiction by applying local quality through selective polymer accumulation. The water-soluble polymer is designed to accumulate preferentially at the edge region (within 1mm from the outer edge) under the influence of centrifugal force and capillary action during polishing. This localized accumulation creates a protective layer only where needed, reducing the polishing rate specifically at the edges to prevent roll-off, while the central region (FQA) maintains its normal polishing rate, thereby preserving overall productivity
Solution Approach 2:
The patent applies partial action by having the polymer accumulate excessively at the edge region compared to the center. The concentration of the polymer is designed to be highest at the edges where it is most needed to prevent roll-off, while gradually decreasing toward the center. This partial or excessive accumulation at the critical edge region allows the patent to improve surface flatness without significantly affecting the overall polishing rate across the entire wafer surface
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 solution effectively reduces edge roll-off and enhances surface flatness, increasing the usable area of silicon wafers and improving yield while maintaining productivity, thus reducing manufacturing costs.
Implementation Method 1
a water soluble polymer which can selectively interpose near edges of a polished substrate
Implementation Method 2
polishing is carried out under compression and rotation
Data Source
AI summary
Slurry composition and a method of substrate polishing used in chemical mechanical polishing (CMP). The present invention concerns a slurry composition containing a polishing agent and a water soluble polymer. The slurry composition contains a water soluble polymer that has a solubility parameter in the range of 9.0 to 14.0 and that may contain hetero atoms at a level sufficient to lower the polishing rate near the edges of the polished substrate defined as the region within 1 mm of the outer edge of the polished substrate to a level below the mean polishing rate of the polished substrate. The water soluble polymer may have a mean molecular weight in the range of 200 to about 3,000,000, and the mean molecular weight may be in the range of 200 to 110,000 if hetero atoms are present in the main-chain structure and the SP value is under 9.5.