Optimal Location Selection for Substrate Measurement Sampling
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Solution Overview
Problem
Current lithographic apparatuses face challenges in achieving accurate cross-wafer and cross-field sampling while being flexible enough to handle constraints such as limited measurement time and uniformity of feature locations, which affects the accuracy of process fingerprints like focus and overlay.
Innovation Solution
A method using simulated annealing to select optimal sets of locations on a substrate for measurements or feature placement, involving operations like duplication, mutation, and cross-over, to define candidate solutions based on constraints like available positions, measurement time, and uniformity, ensuring efficient and accurate sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an increased number of target features are measured across the substrate to improve accuracy of process fingerprints, then measurement precision is improved, but measurement time increases and throughput decreases
Solution Approach 1:
The patent extracts only the most informative subset of target features from the complete set of available features on the substrate. By identifying and selecting a minimal optimal set of locations that capture the essential process variations, the system achieves accurate process fingerprint determination without measuring all possible features, thereby reducing measurement time while maintaining precision.
Solution Approach 2:
The patent applies local quality by assigning different selection criteria and weights to different regions of the substrate. Rather than uniformly sampling all areas, the system identifies specific local regions where measurements provide the most value for capturing process fingerprints, optimizing the distribution of measurement locations to improve efficiency without sacrificing accuracy.
2Measurement precision
If more target features are measured to capture focus fingerprint with sufficient accuracy, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The patent extracts a minimal optimal subset of target features specifically for focus fingerprint determination. By identifying the smallest set of measurement locations that sufficiently capture focus variations across the substrate, the system achieves accurate focus measurement without the need to measure all available features, thereby maintaining productivity while improving measurement precision.
Solution Approach 2:
The patent applies partial action by measuring only the necessary portion of target features required to achieve sufficient focus fingerprint accuracy. Rather than performing exhaustive measurements across the entire substrate, the system selectively measures a partial set of features that provides adequate information for focus determination, balancing precision requirements with productivity constraints.
3Measurement precision
If measurement locations are optimized for uniformity distribution across the substrate, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the substrate into multiple regions and selects measurement locations within each segment to achieve overall uniform distribution. By dividing the substrate into manageable segments and applying systematic selection criteria to each segment, the system achieves uniform measurement location distribution without requiring complex global optimization algorithms, thereby reducing computational complexity while maintaining measurement precision.
Data Source
AI summary
A method for selecting an optimal set of locations for a measurement or feature on a substrate, the method includes: defining a first candidate solution of locations, defining a second candidate solution with locations based on modification of a coordinate in a solution domain of the first candidate solution, and selecting the first and/or second candidate solution as the optimal solution according to a constraint associated with the substrate.