Optimizing computational efficiency by multiple truncation of spatial harmonics

The invention relates to optimizing computational efficiency by multiple truncation of spatial harmonics. The computational efficiency of electromagnetic simulation algorithms based on truncated spatial harmonic series is improved for periodic targets that exhibit a fundamental spatial period and one or more approximate periods that are integer fractions of the fundamental spatial period. Spatialharmonics are classified according to each distinct period of the target exhibiting multiple periodicity. A distinct truncation order is selected for each group of spatial harmonics. This approach produces optimal, sparse truncation order sampling patterns, and ensures that only harmonics with significant contributions to the approximation of the target are selected for computation. Metrology systems employing these techniques are configured to measure process parameters and structural and material characteristics associated with different semiconductor fabrication processes. 本发明涉及通过空间谐波的多重截断而优化计算效率。基于经截断空间谐波级数的电磁模拟算法