Focus-Exposure Model Calibration for Lithography Process Window
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Solution Overview
Problem
Current lithography simulation models struggle with accuracy and robustness, particularly in predicting lithographic performance across a multidimensional parameter space, including geometry and process window variations, which hampers the manufacturability of advanced semiconductor designs.
Innovation Solution
A focus-exposure model calibration system that utilizes data from multiple dimensions within an exposure-defocus process window space to provide unified model parameter values, enabling better accuracy and robustness, and the ability to predict lithographic performance at any point within the process window without recalibration, by selecting initial fitting parameter values, generating simulated results, and comparing them with actual results to optimize parameter values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional lithography simulation models are used, then the model structure is simple, but the accuracy and robustness in predicting lithographic performance across multidimensional parameter space deteriorates
Solution Approach 1:
The patent transitions from traditional single-point calibration to multi-dimensional calibration across the process window. It introduces calibration at multiple sampling locations spanning focus and exposure parameter spaces, transforming the calibration approach from one-dimensional to multi-dimensional, thereby capturing the complex interactions between process parameters and lithographic outcomes
Solution Approach 2:
The patent segments the process window into multiple discrete sampling locations for calibration. By dividing the continuous parameter space into distinct calibration points and using weighted combinations of calibration data from these segments, the model achieves comprehensive coverage of the parameter space while maintaining computational manageability
2Adaptability or versatility
If traditional calibration methods are used, then the calibration process is simple, but the ability to predict performance across process window variations without recalibration deteriorates
Solution Approach 1:
The patent performs preliminary calibration across the entire process window by selecting multiple sampling locations that span the focus and exposure parameter ranges. This advance calibration establishes a comprehensive model that can predict performance at any point within the process window without requiring subsequent recalibration, thereby eliminating time losses associated with repeated calibration procedures
Solution Approach 2:
The patent creates a universal calibration model that functions across all conditions within the process window. By calibrating at multiple sampling locations and combining the results with appropriate weighting, the model achieves multi-functionality, serving as a single predictive tool for diverse lithographic conditions rather than requiring separate calibrated models for each condition
3Reliability
If more sampling locations are used in calibration, then the model accuracy across process window improves, but the number of measurements required increases
Solution Approach 1:
The patent applies partial calibration by selecting a strategic subset of sampling locations within the process window rather than calibrating at every possible point. By carefully choosing sampling locations that provide maximum information content and using weighted combinations, the method achieves robust predictive capability with fewer measurements than a complete grid calibration would require
Data Source
AI summary
A system and a method for creating a focus-exposure model of a lithography process are disclosed. The system and the method utilize calibration data along multiple dimensions of parameter variations, in particular within an exposure-defocus process window space. The system and the method provide a unified set of model parameter values that result in better accuracy and robustness of simulations at nominal process conditions, as well as the ability to predict lithographic performance at any point continuously throughout a complete process window area without a need for recalibration at different settings. With a smaller number of measurements required than the prior-art multiple-model calibration, the focus-exposure model provides more predictive and more robust model parameter values that can be used at any location in the process window.