Double-Side Wafer Polishing Termination Using Shape Index Feedback
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Solution Overview
Problem
Conventional double-side polishing methods struggle to accurately terminate the process based on wafer thickness measurements, resulting in wafers that do not achieve the target shape.
Innovation Solution
A double-side polishing apparatus and method that utilize real-time thickness measurements through monitoring holes, with a computing unit to analyze thickness data, extract shape components, determine their positions, compute shape distributions, and calculate a shape index to precisely determine the termination timing based on a set value derived from the difference between target and actual shape indices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If polishing time is controlled based on operator experience and wafer thickness measurements, then the wafer thickness can be reduced to match the carrier plate thickness, but the wafer shape deviates from the target shape due to inaccurate termination timing
Solution Approach 1:
The system continuously monitors wafer thickness in real-time during polishing and feeds this information back to the control unit. The control unit compares the measured thickness against the target thickness and automatically adjusts or determines the termination timing to achieve the target wafer shape, eliminating reliance on operator experience.
Solution Approach 2:
The patent replaces the manual operator-based timing control system with an automated optical measurement and computational control system. Through-hole monitoring devices measure wafer thickness optically, and a control unit processes this data to determine termination timing, substituting human judgment with precise instrumental measurement and algorithmic decision-making.
2Manufacturing precision
If polishing is terminated when wafer thickness equals carrier plate thickness, then thickness control is achieved, but the wafer periphery shape does not match the target shape
Solution Approach 1:
The control unit divides the wafer into multiple measurement regions (center and periphery) and analyzes thickness data separately for each region. By segmenting the wafer surface and evaluating shape components at different locations, the system can determine termination timing that achieves the target shape across the entire wafer surface, not just at the center.
3Measurement precision
If multiple thickness measurements are taken during polishing, then real-time thickness data is obtained, but the complexity of data processing and termination timing determination increases
Solution Approach 1:
The control unit extracts only the essential shape components from the multiple thickness measurements taken during polishing. By identifying and isolating the critical shape parameters that determine whether the target shape is achieved, the system simplifies the decision-making process for termination timing while still utilizing comprehensive measurement data.
Data Source
AI summary
Provided is a double-side polishing apparatus and a double-side polishing method for a work which make it possible to terminate double-side polishing with timing allowing a work having been polished to have a target shape. A computing unit performs a step of grouping the data of thicknesses on a work basis; a step of extracting shape components of each work; a step of identifying a position of each of the shape components in the work radial direction; a step of computing a shape distribution of the work; a step of obtaining a shape index of the work; and a step of determining timing at which the obtained shape index becomes a set value of the shape index, determined based on a difference between a target value and an actual value of the shape index in the previous batch, as timing of termination of the double-side polishing.