Semiconductor Wafer Optical Characteristic Calculation via Field Segmentation
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Solution Overview
Problem
Current methods for calculating the optical characteristics of semiconductor wafers, such as reflectivity and diffraction, are inefficient when dealing with finite-sized structures or defects within periodic patterns, as they require large unit cells and increased computational resources, leading to significant inaccuracies and increased computation times.
Innovation Solution
A system and method that determine optical characteristics by computing a background optical field for a reference structure and a correction optical field, allowing for the extraction of characteristics from measured optical signals with improved accuracy and reduced computational demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional RCWA or FDTD methods are used to calculate optical characteristics of finite-sized structures or defects within periodic patterns, then measurement precision is maintained, but computation time increases significantly and computational resources are excessive
Solution Approach 1:
The patent segments the electromagnetic problem into two distinct parts: (1) calculating the background optical field for the periodic structure using efficient RCWA methods, and (2) calculating the correction optical field for the finite-sized defect or target using FDTD methods only in the localized region where the defect exists. This segmentation allows each part to be solved with the most appropriate and efficient method, avoiding the need to use computationally intensive FDTD for the entire periodic structure.
Solution Approach 2:
The patent extracts the defect or finite-sized target from the periodic structure and treats it separately. The defect is identified and isolated, and its optical field is calculated independently using FDTD methods. This extracted approach allows the periodic background to be handled efficiently by RCWA while the defect is handled with the more accurate but computationally intensive FDTD method only where necessary.
2Measurement precision
If traditional RCWA or FDTD methods are used to calculate optical characteristics of finite-sized structures or defects within periodic patterns, then measurement precision is maintained, but computational resources increase significantly
Solution Approach 1:
The patent segments the electromagnetic problem into two distinct parts: (1) calculating the background optical field for the periodic structure using efficient RCWA methods, and (2) calculating the correction optical field for the finite-sized defect or target using FDTD methods only in the localized region where the defect exists. This segmentation allows each part to be solved with the most appropriate and efficient method, avoiding the need to use computationally intensive FDTD for the entire periodic structure.
Solution Approach 2:
The patent extracts the defect or finite-sized target from the periodic structure and treats it separately. The defect is identified and isolated, and its optical field is calculated independently using FDTD methods. This extracted approach allows the periodic background to be handled efficiently by RCWA while the defect is handled with the more accurate but computationally intensive FDTD method only where necessary.
3Measurement precision
If large unit cells are used to model finite-sized structures within periodic patterns, then measurement precision is improved, but device complexity and computational resources increase
Solution Approach 1:
The patent extracts the defect or finite-sized target from the periodic structure and treats it separately. The defect is identified and isolated, and its optical field is calculated independently using FDTD methods. This extracted approach allows the periodic background to be handled efficiently by RCWA while the defect is handled with the more accurate but computationally intensive FDTD method only where necessary.
Solution Approach 2:
The patent applies different computational methods to different regions of the structure: RCWA is used for the periodic background regions where it is computationally efficient, while FDTD is used only in the localized region where the finite-sized defect or target exists. This local quality approach ensures high accuracy where needed while maintaining overall computational efficiency.
Data Source
AI summary
Determination of one or more optical characteristics of a structure of a semiconductor wafer includes measuring one or more optical signals from one or more structures of a sample, determining a background optical field associated with a reference structure having a selected set of nominal characteristics based on the one or more structures, determining a correction optical field suitable for at least partially correcting the background field, wherein a difference between the measured one or more optical signals and a signal associated with a sum of the correction optical field and the background optical field is below a selected tolerance level, and extracting one or more characteristics associated with the one or more structures utilizing the correction optical field.