CMP Pressure Control Using Predicted Parameter Changes
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Solution Overview
Problem
Chemical mechanical polishing (CMP) processes face challenges in achieving uniform material removal rates due to variations in substrate thickness, slurry composition, polishing pad conditions, and pressure loads, leading to within-wafer non-uniformity and edge exclusion issues.
Innovation Solution
A computer program or method that uses in-situ monitoring to calculate adjustments for polishing parameters, optimizing pressure changes and minimizing cost functions to achieve target thickness while constraining pressure differentials and avoiding underdamped or overdamped behavior, allowing for real-time control of polishing parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CMP control methods are used to achieve target thickness, then material removal rate is controlled, but within-wafer non-uniformity and edge exclusion occur due to pressure variations
Solution Approach 1:
The carrier head is divided into multiple independently controllable pressure chambers that can be adjusted separately to compensate for local variations in polishing rate across different regions of the substrate, thereby reducing within-wafer non-uniformity while maintaining overall thickness control
Solution Approach 2:
Different regions of the substrate receive customized pressure profiles through the segmented pressure chambers, allowing local adjustment of polishing rates to achieve uniform thickness across the entire wafer surface, particularly addressing edge exclusion issues
2Manufacturing precision
If real-time parameter adjustments are made during polishing, then polishing uniformity is improved, but system complexity increases due to multiple objectives and constraints
Solution Approach 1:
In-situ monitoring systems continuously measure substrate thickness or surface topology during polishing and feed this information back to the controller, which automatically adjusts pressure chamber settings in real-time to maintain uniform polishing across the wafer
Solution Approach 2:
The system dynamically changes pressure parameters across different chambers during the polishing process based on real-time measurements, allowing adaptation to varying material removal rates while managing system complexity through automated control algorithms
Data Source
AI summary
Controlling a polishing system includes receiving from an in-situ monitoring system, for each region of a plurality of regions on a substrate being processed by the polishing system, a sequence of characterizing values for the region. For each region, a polishing rate is determined for the region, and an adjustment is calculated for at least one processing parameter. For each of a plurality of parameter update times, an adjustment is calculated for at least one processing parameter, wherein calculation of the adjustment for a particular parameter update time from the plurality of parameter update times includes calculation of expected future parameter changes for one or more future parameter update times subsequent to the particular parameter update time.