Polishing Pad Surface Histogram Analysis for CMP Wear Judging
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Solution Overview
Problem
The existing chemical mechanical polishing (CMP) process for semiconductor devices faces challenges in accurately determining the wear of polishing pads, leading to inconsistent film-thickness profiles and premature or delayed replacement of pads, due to indirect indicators of pad wear such as use time and number of substrates polished.
Innovation Solution
A surface property judging method and system that generates and analyzes histograms of shape index values from the polishing pad, using a surface data generator and arithmetic system to determine the pad's surface condition, comparing it to reference data to assess similarity and predict replacement time, and potentially using machine learning for deterioration assessment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If use time or number of substrates polished is used as indicator for polishing pad wear, then replacement timing can be determined, but the indication of actual pad wear is inaccurate leading to premature or delayed replacement
Solution Approach 1:
The patent replaces indirect mechanical indicators (use time, substrate count) with direct optical measurement of pad surface properties. A light source illuminates the polishing pad surface, and a sensor detects reflected light intensity to calculate surface roughness, providing accurate real-time wear measurement without relying on time-based estimates.
Solution Approach 2:
The patent introduces an intermediary measurement system between the polishing pad and the replacement decision. Instead of directly using time or substrate count, the system measures surface roughness through light reflection characteristics, using the ratio of diffuse reflection to total reflection as an intermediary parameter to accurately indicate pad wear state.
2Ease of manufacture
If polishing pad is replaced based on predetermined time or substrate count, then replacement process is simple, but target film-thickness profile cannot be achieved due to excessive wear
Solution Approach 1:
The patent implements a feedback mechanism where the surface roughness measurement continuously monitors pad wear state. When the measured roughness exceeds a predetermined threshold, the system triggers a replacement alert, ensuring the pad is replaced at the optimal moment to maintain film-thickness profile accuracy while avoiding premature replacement.
3Adaptability or versatility
If individual differences in polishing pads are considered, then appropriate replacement time varies, but determination becomes complex and time-consuming
Solution Approach 1:
The patent applies local quality by measuring surface roughness at multiple specific locations on the polishing pad surface (center, intermediate, and peripheral regions). This localized measurement approach captures individual pad characteristics and wear patterns without requiring complex overall analysis, enabling pad-specific replacement timing determination through simple comparative evaluation of regional roughness values.
Data Source
AI summary
A surface property judging method and a surface property judging system for a polishing pad capable of appropriately judging a surface property of the polishing pad are disclosed. The surface property judging method includes: rotating a polishing table together with a polishing pad which is supported by the polishing table; generating surface data by a surface data generator, the surface data containing a plurality of shape index values representing a surface property of the polishing pad; producing a histogram indicating a distribution of the plurality of shape index values based on the surface data; and judging the surface property of the polishing pad based on the histogram.