Topography-Aware Optical Proximity Correction for Wafer Lithography
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Solution Overview
Problem
In photolithography, wafer topography variations cause depth of focus issues, leading to inaccuracies in transferring geometric patterns to the photoresist, as existing optical proximity correction methods do not account for varying topographies, resulting in out-of-focus regions and larger critical dimensions.
Innovation Solution
A topography-aware optical proximity correction method that determines the wafer's topography, divides it into regions based on height, calculates specific defocus values for each region, and performs optical proximity correction using these values to generate accurate simulated contours, thereby compensating for topographical variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If optical proximity correction is performed using a single defocus value for the entire wafer, then the processing is simple and fast, but the pattern transfer accuracy deteriorates due to wafer topography variations causing out-of-focus regions
Solution Approach 1:
The wafer is divided into multiple regions based on topography characteristics, with each region assigned a specific defocus value. This segmentation allows the optical proximity correction to account for topography variations across different areas of the wafer, improving pattern transfer accuracy while maintaining computational feasibility through region-based processing
Solution Approach 2:
Different defocus values are applied to different regions of the wafer according to their specific topography characteristics. This local quality approach ensures that each region receives the appropriate correction for its height variations, thereby improving overall manufacturing precision without requiring a completely complex system-wide solution
2Manufacturing precision
If the depth of focus margin is reduced to meet current scale requirements, then the resolution improves, but the tolerance to topography variations decreases, causing out-of-focus errors
Solution Approach 1:
The system dynamically adjusts the defocus value based on the topography of each region rather than using a fixed defocus value for the entire wafer. This dynamic adaptation allows the correction method to respond to varying topography conditions, maintaining dimensional accuracy while accommodating topography variations through region-specific parameter optimization
3Measurement precision
If wafer topography variations are not accounted for in optical proximity correction, then the correction process is simpler, but the critical dimension accuracy deteriorates due to out-of-focus regions
Solution Approach 1:
The topography of the wafer is measured and analyzed before the optical proximity correction process. This preliminary action allows the system to pre-determine appropriate defocus values for different regions, ensuring that topography variations are accounted for in the subsequent correction process, thereby improving critical dimension accuracy without adding excessive complexity during the main correction phase
Data Source
AI summary
Various embodiments provide for topography aware optical proximity correction that can improve depth of focus during wafer lithography. The system can determine the topography of the wafer using real process information. The topographical variations can be based on random defects or structural details. The system can divide the wafer into regions based on the topography of the regions and determine depth of focus values for each of the regions. Optical proximity correction can then be performed on each region separately, using the separate defocus values to yield an accurate, topographically aware optical proximity correction model for the wafer. For regions with varying topography, optical proximity correction can be performed for two defocus values corresponding to the high and low extremes, such that the resulting simulated contour is satisfies a predetermined criterion associated with accuracy.