Feedforward Control Damping for Lithographic Positioning
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Solution Overview
Problem
In exposure apparatuses, control deviations occur when the target time for continuing feedforward operation exceeds the upper limit, leading to decreased accuracy and throughput due to limited memory capacity and complex processing requirements for storing multiple feedforward operation amounts.
Innovation Solution
A control device that determines whether the target time for continuing control exceeds a predetermined time and corrects the feedforward operation amount by damping it towards the end, using a processor or circuit to adjust the operation amount based on a damping start point and curvature, thereby reducing control deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedforward operation amount is stored for long processing time (200 msec or more), then control deviation can be curbed during exposure, but memory capacity is exceeded and device complexity increases
Solution Approach 1:
The patent segments the feedforward operation amount into two parts: a first feedforward operation amount determined based on system characteristics, and a second feedforward operation amount determined based on actual measurement results. This segmentation allows the large-capacity storage requirement to be divided, with only the second part needing to be stored in limited memory capacity, thus resolving the contradiction between maintaining control accuracy and managing memory constraints
Solution Approach 2:
The patent applies preliminary action by determining the first feedforward operation amount in advance based on system characteristics before actual exposure. This pre-determined amount is applied during exposure without requiring storage in limited memory, thereby maintaining control accuracy while avoiding memory capacity constraints
2Reliability
If feedforward operation amount is stored for long processing time, then control deviation can be curbed, but processing complexity increases due to layer management
Solution Approach 1:
The patent segments the feedforward control into two distinct determination processes: one based on system characteristics and another based on actual measurements. This segmentation simplifies the overall processing by clearly defining when each type of feedforward amount should be applied, reducing the complexity of managing multiple feedforward operation amounts across different layers
Solution Approach 2:
The patent changes the parameters used for determining feedforward operation amount based on the timing and context. For the first feedforward amount, system characteristics are used as parameters; for the second feedforward amount, actual measurement results are used. This parameter change approach simplifies processing by selecting appropriate parameters for each stage rather than managing all parameters throughout
3Quantity of substance
If feedforward control is stopped, then memory usage is reduced, but control deviation occurs during alignment measurement and exposure
Solution Approach 1:
The patent applies preliminary action by determining the first feedforward operation amount in advance based on system characteristics before actual alignment measurement and exposure. This pre-determined amount ensures that control accuracy is maintained during these critical processes without requiring continuous storage of large amounts of feedforward data in memory
Solution Approach 2:
The patent implements feedback by determining the second feedforward operation amount based on actual measurement results obtained during alignment measurement. This feedback mechanism ensures that any control deviations are corrected based on real-world performance data, maintaining manufacturing precision while managing memory usage efficiently
Data Source
AI summary
A control device for performing position control of a control target by imparting a feedforward operation amount to the control target to curb a control deviation even when a continuous target time of the control exceeds an upper limit in a case where the position control is performed by imparting the feedforward operation amount, including at least one processor or circuit configured to function as a determination unit configured to determine whether or not a target time for continuing the control using the feedforward operation amount exceeds a predetermined time, and a correction unit configured to correct the feedforward operation amount to be damped toward an end of the target time in a case where it is determined by the determination unit that the target time has exceeded the predetermined time.