Colloidal Silica Polishing Composition for Semiconductor Wafers
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Solution Overview
Problem
Conventional polishing compositions using non-spherical colloidal silica or colloidal silica with bimodal particle diameter distribution face challenges in achieving both high polishing rates and sedimentation stability.
Innovation Solution
A polishing composition with colloidal silica that satisfies specific criteria, including a high average aspect ratio, broad particle diameter distribution, and a high volume fraction of particles within 1 to 300 nm, along with a broad aspect ratio distribution, to enhance both polishing rate and sedimentation stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If non-spherical colloidal silica or colloidal silica with bimodal particle diameter distribution is used to obtain a higher polishing rate, then the polishing rate is improved, but the sedimentation stability deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle diameter distribution (standard deviation σD = 30-70 nm) and aspect ratio distribution (standard deviation σA = 0.05-0.20) of colloidal silica, along with maintaining specific concentration ranges (0.5-5.0 wt%). These parameter optimizations enable the colloidal silica to achieve both high polishing rate and excellent sedimentation stability, resolving the technical contradiction between productivity and composition stability.
2Productivity
If colloidal silica with broad particle diameter distribution is used to enhance polishing rate, then the polishing rate is improved, but the uniformity of particle distribution deteriorates
Solution Approach 1:
The patent optimizes the particle diameter distribution by controlling the standard deviation σD to be 30-70 nm and setting the volume fraction F of particles with diameter 1-300 nm to 60-95%. This controlled distribution broadens the effective polishing particle range while maintaining sufficient uniformity to prevent sedimentation, thereby achieving both high polishing rate and stable particle distribution.
3Productivity
If colloidal silica with high aspect ratio is used to improve polishing performance, then the polishing rate is improved, but the sedimentation stability deteriorates
Solution Approach 1:
The patent controls the aspect ratio distribution of colloidal silica by setting the standard deviation σA to 0.05-0.20 and the volume fraction G of particles with aspect ratio 1.05-1.30 to 70-95%. This optimization ensures that particles have sufficiently high aspect ratios for effective polishing while maintaining a narrow enough distribution to prevent excessive sedimentation, resolving the contradiction between polishing performance and sedimentation stability.
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 composition achieves a high polishing rate while maintaining excellent sedimentation stability, preventing scratches and ensuring a stable polishing process by controlling the particle distribution and aspect ratios of colloidal silica.
Implementation Method 1
a polishing composition used mainly in polishing an object-to-be-polished, such as semiconductor wafers including silicon wafers
Data Source
AI summary
A polishing composition contains colloidal silica. The colloidal silica satisfies the expression A×D×E×F≧350,000 where “A” denotes the average aspect ratio (dimensionless) of the colloidal silica, “D” denotes the average particle diameter (units: nm) of the colloidal silica, “E” denotes the standard deviation of the particle size (units: nm) of the colloidal silica, and “F” denotes the volume fraction (units: %) of particles having a diameter of 1 to 300 nm in the colloidal silica. The volume fraction of particles having a diameter of 1 to 300 nm in the colloidal silica is 90% or greater.