Laser Energy Control Using Repetition-Rate Gain Estimators
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Solution Overview
Problem
Existing laser light sources in photolithography face challenges in quickly and accurately stabilizing to desired energy levels due to noise and disturbances, leading to convergence lag when repetition rates change.
Innovation Solution
Implementing a set of gain estimators for varying repetition rates to immediately adjust laser voltage without convergence lag, using a RepRate Gain Estimator table to retrieve corresponding gain estimators for each repetition rate range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional laser control methods are used, then the laser system is simple to operate, but the convergence delay increases when repetition rate changes
Solution Approach 1:
The patent pre-calculates and stores gain estimators for multiple repetition rates before operation. When a repetition rate change is commanded, the corresponding pre-computed gain estimator is immediately retrieved and applied, eliminating the need for real-time convergence calculation and thus reducing convergence delay.
Solution Approach 2:
The patent implements dynamic adjustment of laser voltage by switching between different gain estimators based on the commanded repetition rate. The controller dynamically selects the appropriate gain estimator from a plurality of stored estimators, enabling rapid adaptation to changing operational conditions without fixed convergence delays.
2Manufacturing precision
If conventional gain estimation is used, then the device complexity is low, but the manufacturing precision of laser energy control deteriorates
Solution Approach 1:
The patent segments the gain estimation into multiple discrete repetition rate ranges, each with its own dedicated gain estimator. This segmentation allows precise control for each repetition rate band while keeping individual estimators relatively simple, as each is optimized for a specific range rather than requiring a single complex estimator to handle all rates.
Solution Approach 2:
The patent changes the control parameter from a single gain estimator to multiple gain estimators, each tuned for specific repetition rate ranges. This parameter change enables higher precision energy control by selecting the most appropriate estimator for the current operating conditions, while the overall system complexity remains manageable through structured organization.
Data Source
AI summary
A laser system's laser light energy control and resulting dose control is improved by creating and using a set of gain estimators, one for each of a set or range of laser light pulse repetition rates. When a new repetition rate is used, its corresponding gain estimator is retrieved, used to compute the voltage to fire the laser source, and updated. The resulting generated laser light thereby avoids the convergence delay inherent in prior laser systems and, further, can repeatedly do so with subsequent specified repetition rates.