Iterative Spatial Harmonics Truncation for Optical Metrology
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Solution Overview
Problem
The accuracy of diffraction signal simulations in optical metrology depends on the number of spatial harmonics orders used, but increasing this number significantly increases computation time, and arbitrarily minimizing it can lead to loss of information, especially in three-dimensional structures.
Innovation Solution
A method is introduced to iteratively truncate and modify sets of spatial harmonics orders based on different patterns to optimize the number used for simulation, prioritizing orders that carry the most information and adjusting them until a preset error or accuracy threshold is met, thereby reducing computation costs without sacrificing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of spatial harmonics orders is increased to improve simulation accuracy, then measurement precision is improved, but computation time increases significantly
Solution Approach 1:
The patent applies partial action by selectively including only the most relevant spatial harmonics orders in the simulation. Instead of using all possible orders or a fixed large number, the method identifies and includes only those orders that contribute significantly to the diffraction signal accuracy, thereby achieving sufficient measurement precision with reduced computation time
Solution Approach 2:
The patent dynamically adjusts the number of spatial harmonics orders based on the specific grating structure being analyzed. By changing this parameter adaptively rather than using a fixed value, the method optimizes the balance between simulation accuracy and computation time for different structural complexities
2Productivity
If the number of spatial harmonics orders is minimized to reduce computation time, then productivity is improved, but loss of information occurs
Solution Approach 1:
The patent applies local quality by treating different spatial harmonics orders differently based on their individual importance. Rather than uniformly including or excluding all orders, the method evaluates each order's contribution to the diffraction signal and selectively includes only those that carry significant information, thus maintaining accuracy while improving efficiency
Solution Approach 2:
The method uses partial action by including only the necessary subset of spatial harmonics orders required to capture the essential diffraction information. This selective approach prevents information loss while avoiding the inclusion of redundant orders that would increase computation time unnecessarily
3Measurement precision
If the number of spatial harmonics orders is increased for three-dimensional structures, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the set of spatial harmonics orders into different groups or categories based on their importance. This allows the method to systematically manage and process only the relevant subset of orders for three-dimensional structures, reducing computational complexity while maintaining measurement precision
Data Source
AI summary
A method for improving computation efficiency for diffraction signals in optical metrology is described. The method includes simulating a set of spatial harmonics orders for a grating structure. The set of spatial harmonics orders is truncated to provide a first truncated set of spatial harmonics orders based on a first pattern. The first truncated set of spatial harmonics orders is modified by an iterative process to provide a second truncated set of spatial harmonics orders based on a second pattern, the second pattern different from the first pattern. Finally, a simulated spectrum is provided based on the second truncated set of spatial harmonics orders.