Double-Side Polishing Shape Control via Real-Time Thickness Feedback
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Solution Overview
Problem
Conventional double-side polishing methods struggle to achieve a target shape for semiconductor wafers, as the timing of termination is based on thickness measurement rather than shape, leading to inconsistencies in the polished surface.
Innovation Solution
A double-side polishing apparatus and method that utilize real-time thickness measurement through holes in the polishing plates, with a computing unit to analyze thickness data, identify shape components, compute shape distribution, and determine the optimal termination time based on a shape index, ensuring the wafer achieves a target shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If polishing time is adjusted by operator experience to achieve target thickness, then wafer thickness can be controlled, but polishing shape precision deteriorates due to operator variability and inconsistent termination timing
Solution Approach 1:
The patent implements real-time feedback by continuously measuring wafer thickness during polishing through holes in the polishing plates and using this data to automatically determine when to terminate polishing. The measurement results are fed back to the control system, which automatically stops polishing when the target thickness is reached, eliminating operator variability and ensuring consistent shape precision.
Solution Approach 2:
The patent replaces the manual operator-based thickness adjustment system with an automated optical measurement and control system. Thickness measuring devices using light beams substitute for operator experience, and the control system automatically determines termination timing based on real-time measurements, replacing the mechanical/manual adjustment process with an automated electronic control system.
2Manufacturing precision
If polishing is terminated when wafer thickness equals carrier plate thickness, then thickness uniformity is achieved, but shape uniformity deteriorates due to peripheral sagging and depression
Solution Approach 1:
The patent segments the wafer surface into multiple measurement zones by positioning holes at different radial locations (center and periphery) on the polishing plates. This allows independent measurement of thickness at different locations, enabling the system to detect and compensate for shape variations such as peripheral sagging or central depression, thereby achieving both thickness and shape uniformity.
Solution Approach 2:
The patent changes the measurement parameter from a single overall thickness value to multiple localized thickness values at different radial positions. By measuring thickness at both center and periphery locations simultaneously, the system can detect shape deviations and adjust polishing parameters or termination timing to achieve uniform shape across the entire wafer surface.
3Extent of automation
If real-time thickness measurement is implemented through holes in polishing plates, then automated termination timing is achieved, but measurement reliability deteriorates due to inconsistent measurement positions and missed measurements
Solution Approach 1:
The patent introduces an intermediary computational processing layer that receives raw measurement data, identifies measurement positions based on hole locations and carrier plate rotation, filters invalid measurements, and reconstructs reliable thickness data. This intermediary system bridges the gap between the physical measurement holes and the automated control system, ensuring measurement reliability despite positional variations.
Solution Approach 2:
The patent performs preliminary actions by pre-defining hole positions on the polishing plates and pre-calculating measurement position mappings before polishing begins. The system also pre-establishes criteria for valid measurements and prepares data processing algorithms in advance, enabling reliable automated termination timing without requiring complex real-time decisions during polishing.
Data Source
AI summary
Provided is a double-side polishing apparatus and a double-side polishing method 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 13 performs a step of grouping the data of thicknesses measured using work thickness measuring devices 11 on a work basis; a step of extracting shape components of each work from the thickness data; 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 from the identified position ; a step of obtaining a shape index of the work from the computed shape distribution; and a step of determining timing of termination of the double-side polishing based on the obtained shape index, thus timing of termination of the double-side polishing is determined.