Lithography Mask Qualification with Temporal Drift Correction
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Solution Overview
Problem
Existing mask qualification methods for lithography systems are time-consuming due to the need for extensive measurements at multiple points, which are often affected by drifts, requiring significant time expenditure.
Innovation Solution
A method involving sequential first detection at all measurement points, followed by second detection at a subset of reference points, determining deviations, and applying a temporal correction factor to obtain corrected critical dimensions, reducing the overall qualification time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mask qualification is performed at all measurement points multiple times to account for drift, then measurement precision is improved, but measurement time increases significantly
Solution Approach 1:
The patent divides the measurement process into two segments: a first measurement at all measurement points to establish baseline values, and a second measurement at only a subset of reference measurement points to determine drift. This segmentation allows the system to maintain high precision through drift correction while significantly reducing the time required for repeated measurements across all points.
Solution Approach 2:
The patent applies partial action by performing the second measurement only at a selected subset of reference measurement points rather than at all measurement points. This subset is sufficient to determine the temporal drift profile, which is then applied to correct measurements at all points, achieving the necessary precision without the excessive time cost of measuring all points repeatedly.
2Measurement precision
If multiple measurement passes are performed to determine deviations and apply corrections, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the drift determination function to a separate, simplified process involving only reference measurement points. By isolating the drift measurement to a subset of points and using these to create a temporal correction profile, the system reduces the complexity of the overall measurement process while maintaining the ability to detect and correct deviations at all measurement points.
3Measurement precision
If sequential measurement at all points is performed, then measurement precision is maintained, but productivity decreases
Solution Approach 1:
The patent performs preliminary measurement at all measurement points to establish baseline critical dimension values before drift occurs. This preliminary data, combined with subsequent drift measurements at reference points, allows the system to reconstruct accurate measurements for all points without requiring time-consuming repeated measurements at each location, thereby maintaining precision while improving productivity.
Data Source
AI summary
A method for qualifying a mask for a lithography system, the mask having measurement points for detecting critical dimensions of the mask, comprising: first detection of critical dimensions of the mask at the measurement points, the first detection taking place sequentially and the duration of the first detection defining a measurement time period; determining reference measurement points from the measurement points, the number of reference measurement points being less than the number of measurement points; second detection of the at least one critical dimension of the mask at the reference measurement points; determining a deviation between the first and the second detected critical dimension at each of the reference measurement points; and applying a determined temporal profile of the correction factor to the at least one critical dimension to obtain a corrected critical dimension of the mask, and also a corresponding device for qualifying a mask for a lithography system.