Silicon Wafer Polishing Slurry Sequencing for Haze-Controlled Surface Finish
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Solution Overview
Problem
Conventional silicon wafer polishing methods face limitations in achieving high-grade surface smoothness due to mismatches between polishing slurries used in intermediate and final polishing steps, leading to suboptimal surface quality and increased defects.
Innovation Solution
A method involving an intermediate polishing step with a slurry containing abrasive grains and a water-soluble polymer with a weight average molecular weight of 60 × 10^4 or less, followed by a final polishing step with a slurry containing a surfactant and a water-soluble polymer, where the relative haze of the intermediate slurry is greater than that of the final slurry but less than 6.8 times higher, to ensure a high-grade surface finish.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If different polishing slurries are used in intermediate and final polishing steps, then polishing power is optimized for each step, but mismatches occur between surface grades and slurry properties leading to reduced manufacturing precision
Solution Approach 1:
The patent changes the molecular weight parameter of the water-soluble polymer in the polishing slurry. By using a polymer with a weight average molecular weight of 60×10^4 or less in both intermediate and final polishing steps, the slurry properties are optimized to achieve both adequate polishing power and high surface smoothness without mismatches between steps.
Solution Approach 2:
The patent applies local quality by having different water-soluble polymer characteristics in different polishing steps. The intermediate polishing slurry uses a polymer with Mw ≤ 60×10^4, while the final polishing slurry uses a polymer with lower molecular weight and controlled relative haze, creating locally optimized conditions for each step's specific requirements.
2Ease of manufacture
If conventional polishing slurries are used without molecular weight control, then polishing process is simple, but surface defects increase and surface smoothness is reduced
Solution Approach 1:
The patent introduces a specific parameter control for the water-soluble polymer's molecular weight (Mw ≤ 60×10^4) and relative haze ratio. This parameter control enables achievement of high surface grades while maintaining reasonable process simplicity, as the controlled parameters provide clear guidance for slurry formulation without requiring complex multi-component systems.
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
This approach effectively prevents mismatches between polishing steps, enhancing surface smoothness and reducing defects, thereby achieving a higher-grade silicon wafer surface with improved polishing efficiency.
Implementation Method 1
an intermediate polishing step of polishing a silicon wafer with a polishing slurry Sp containing abrasive grains and a water-soluble polymer
Implementation Method 2
the relative haze Hp of the polishing slurry Sp used in the intermediate polishing step refers to a value calculated in accordance with an equation: Hp = (hp/h 0 ) × 100 from a haze value (haze reference value) h 0
Data Source
AI summary
Provided is a method for polishing a silicon wafer that can effectively obtain a high-grade surface. The method for polishing a silicon wafer includes an intermediate polishing step of polishing a silicon wafer with a polishing slurry Sp containing abrasive grains and a final polishing step of polishing the silicon wafer with a polishing slurry Sf containing abrasive grains. The polishing slurry Sp has a relative haze Hp greater than a relative haze Hf of the polishing slurry Sf and less than 6.8 times as high as the relative haze Hf of the polishing slurry Sf.