Cell Contact Shift Value Calculation for Lithography Mask Correction
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Solution Overview
Problem
Accurate determination of shift values between actual and target cell contacts in semiconductor devices is challenging due to noise and distortion in lithography mask imaging, affecting the precision of cell contact alignment and mask correction.
Innovation Solution
A method involving demarcation of reference and correction regions in images of actual cell blocks, measurement of preliminary shift values, noise reduction, and calculation of actual shift values by minimizing offsets in the reference region to correct lithography masks for precise cell contact formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If preliminary shift values are measured from all cell contacts in the image, then more data is obtained for mask correction, but noise and distortion in imaging reduce measurement precision
Solution Approach 1:
The cell block is divided into a reference region and a correction region. The reference region contains cell contacts used for determining transformation parameters (translation, rotation, scaling), while the correction region contains cell contacts whose shift values are calculated based on these parameters. This segmentation allows precise measurement in the reference region to be applied to the entire block, improving overall precision while maintaining comprehensive data coverage.
Solution Approach 2:
Transformation parameters serve as intermediaries that link the reference region measurements to the correction region calculations. By first determining translation, rotation, and scaling parameters from the reference region, these intermediaries enable accurate shift value calculation for all cell contacts in the correction region without directly measuring each one, thus maintaining precision across the entire block.
2Manufacturing precision
If shift values are calculated for all cell contacts including those in the reference region, then complete correction data is obtained, but the reference region measurements introduce noise and distortion errors
Solution Approach 1:
The reference region is extracted and separated from the correction region. Only cell contacts in the correction region have their shift values calculated using the transformation parameters derived from the reference region. This extraction prevents noise and distortion from the reference region measurements from propagating to the final shift values, while still utilizing the reference region for accurate parameter determination.
Solution Approach 2:
Transformation parameters (translation, rotation, scaling) are determined in advance from the reference region before calculating shift values for the correction region. This preliminary action allows the harmful effects of noise and distortion in the reference region to be isolated, while the derived parameters are then applied to achieve precise alignment correction in the correction region.
3Productivity
If the entire cell block image is used for shift value calculation, then processing time is reduced, but accuracy decreases due to including noisy reference region data
Solution Approach 1:
The cell block is segmented into reference and correction regions, allowing efficient processing of only the correction region for final shift value calculation. The reference region is processed once to determine transformation parameters, which are then applied to the correction region, reducing overall processing time while maintaining high accuracy by excluding noisy reference region data from the final shift value results.
Data Source
AI summary
In a method of calculating a shift value of a cell contact, a reference region and a correction region may be set on an image of an actual cell block. The cell block may include a plurality of actual cell contacts formed using a mask. Each of preliminary shift values of the actual cell contacts with respect to target cell contacts in a target cell block to be formed using the mask may be measured based on the image. The preliminary shift values of the actual cell contacts in the reference region may be minimized. Actual shift values of the actual cell contacts in the correction region with respect to the minimized preliminary shift values may be calculated. Thus, the mask may be corrected using the accurately measured shift values so that the cell contacts may have designed positions.