Exposure Stage Feedforward Control for Reticle-Substrate Synchronization
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Solution Overview
Problem
Existing exposure apparatuses, such as step-and-scan exposure apparatuses, face challenges in suppressing synchronous errors between the reticle stage and the substrate stage, leading to increased position deviations and degraded exposure accuracy due to the inability to accurately correct position deviations on the slave stage when using feedforward control techniques.
Innovation Solution
A control apparatus is implemented with a feedback control system and a feedforward control system that calculates a feedforward manipulated variable based on the input/output response of the second moving member and the synchronous error between the first and second moving members, allowing for synchronized driving and reduction of synchronous errors between the reticle and substrate stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedforward control is applied to each stage independently, then position deviation of individual stages is reduced, but synchronous error between stages increases
Solution Approach 1:
The patent combines the feedforward control of the reticle stage and substrate stage into a unified control system. The synchronous feedforward control unit integrates the feedforward manipulated variables from both stages and calculates a combined feedforward manipulated variable that considers the synchronous error between stages, thereby reducing synchronous error while maintaining individual stage position accuracy.
Solution Approach 2:
The patent implements feedback by measuring the synchronous error between the reticle stage and substrate stage and using this information to adjust the feedforward manipulated variable. The synchronous error measurement unit continuously monitors the position differences between stages, and this feedback is fed back to the synchronous feedforward control unit to optimize the control strategy.
2Ease of operation
If master-slave synchronous driving is used, then coordination between stages is achieved, but synchronous error cannot be suppressed on the slave side
Solution Approach 1:
The patent applies preliminary action by calculating and applying feedforward manipulated variables in advance to compensate for expected synchronous errors. The synchronous feedforward control unit pre-calculates the necessary adjustments based on the measured synchronous error and the input/output response characteristics, applying corrections before the errors manifest during actual operation.
Solution Approach 2:
The patent changes the control parameters by introducing a synchronous feedforward manipulated variable that is calculated based on the synchronous error and the dynamic response characteristics of the slave stage. This parameter change allows the system to adaptively adjust the control strategy to minimize synchronous error while maintaining coordinated motion.
Data Source
AI summary
The present invention provides a control apparatus for performing synchronous control to synchronize driving of a second moving member so as to follow driving of a first moving member, including a feedforward control system that includes a calculator configured to obtain an input/output response of the second moving member and position deviations of the first moving member and the second moving member while driving the first moving member and the second moving member in synchronism with each other, and calculate a feedforward manipulated variable based on the input/output response of the second moving member and the synchronous error between the first moving member and the second moving member obtained from the position deviations of the first moving member and the second moving member.