Full-Field Mask Error Enhancement Function Analysis
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Solution Overview
Problem
In the low k1-factor regime of photo-lithography, traditional methods for calculating the Mask Error Enhancement Factor (MEEF) are insufficient due to increased complexity and optical-proximity effects, leading to inadequate identification of lithographically marginal locations and potential design flaws in photo-masks.
Innovation Solution
A computer system generates simulated wafer patterns to determine a full-field MEEF, including MEEF values in multiple directions along contours, calculating gradients and ratios to account for critical dimension changes and biases, providing a comprehensive analysis of MEEF distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional limited-cutline CD technique is used to calculate MEEF, then the analysis is simpler and faster, but the identification of lithographically marginal locations is insufficient and inaccurate
Solution Approach 1:
The patent segments the MEEF analysis by calculating MEEF values at multiple discrete locations (cutlines) across the mask pattern rather than attempting a single comprehensive measurement. Each cutline represents a specific feature or region, allowing the complex full-field analysis to be broken down into manageable segments that can be processed individually and combined to provide overall MEEF characterization.
Solution Approach 2:
The patent applies local quality analysis by calculating MEEF values specifically at critical locations where lithographic marginality occurs, rather than uniformly across the entire mask. The method identifies and focuses measurement efforts at locations with highest sensitivity to mask errors, such as feature boundaries and corners, providing localized precision where it matters most.
2Reliability
If extensive RET is used in low k1-factor regime, then the compensation for diffraction and optical-proximity effects is improved, but the complexity of photo-lithography simulations increases significantly
Solution Approach 1:
The patent performs preliminary MEEF calculations during the mask design phase to identify and characterize critical locations before full lithographic simulation. By pre-calculating MEEF values at multiple cutlines and determining which locations are most sensitive to mask errors, the method enables targeted simulation efforts that focus computational resources on the most critical areas, reducing overall simulation complexity while maintaining reliability.
3Measurement precision
If full-field MEEF analysis is performed, then the identification of lithographically marginal locations is improved, but the calculation time and computational resources increase
Solution Approach 1:
The patent applies partial action by calculating MEEF values at a selected set of critical cutlines rather than uniformly across all possible locations. The method identifies and focuses on the most critical locations where mask errors have the greatest impact, performing detailed analysis only where needed. This selective approach provides sufficient accuracy for identifying marginal locations while significantly reducing computational time compared to exhaustive full-field analysis.
Data Source
AI summary
A technique for determining a full-field Mask Error Enhancement Function (MEEF) associated with a mask pattern for use in a photo-lithographic process is described. In this technique, simulated wafer patterns corresponding to the mask pattern are generated at an image plane in an optical path associated with the photo-lithographic process. Then, the full-field MEEF is determined. This full-field MEEF includes MEEF values in multiple directions at positions along one or more contours that define boundaries of one or more features in the one or more simulated wafer patterns. Moreover, at least one of the MEEF values is at a position on a contour where a critical dimension for a feature associated with the contour is undefined.