Lithography Stage Feedforward Control for Position-Dependent Response
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Solution Overview
Problem
In lithography apparatuses, quickly reducing control deviation of a control target, such as a stage holding an original or substrate, is challenging due to varying stage responses at different target positions, making it difficult to achieve accurate and efficient positioning.
Innovation Solution
A control device that uses a combination of feedback and feedforward control to determine and update feedforward manipulated values based on measured output responses at multiple target positions, allowing for precise and rapid reduction of control deviations by adjusting the feedforward manipulated values in real-time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single feedforward manipulated value is generated from stage response measurement at one position, then the control deviation can be reduced at that position, but the control deviation cannot be quickly reduced at other target positions where stage responses differ
Solution Approach 1:
The patent divides the control space into multiple segments by measuring stage responses at multiple different target positions. A plurality of feedforward manipulated values are generated corresponding to each measured position, allowing the system to select the appropriate feedforward value based on the current target position, thereby resolving the contradiction between precision at one position and adaptability across multiple positions
Solution Approach 2:
The patent applies local quality by tailoring the feedforward manipulated value to each specific target position. Instead of using a universal feedforward value, the system stores multiple position-specific feedforward manipulated values and selects the appropriate one based on the current operation, ensuring optimal control deviation reduction at each location
2Loss of time
If feedforward control is used to quickly reduce control deviation, then settling time is shortened, but positioning accuracy varies across different target positions due to varying stage responses
Solution Approach 1:
The patent applies preliminary action by pre-measuring stage responses and pre-calculating multiple feedforward manipulated values at different target positions before actual operation. When the stage needs to move to a specific position, the corresponding pre-computed feedforward manipulated value is immediately applied, enabling both quick response (short settling time) and high accuracy by having position-optimized control parameters ready in advance
Data Source
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AI summary
The present invention provides a control device (120) that performs position control of a control target by giving a feedforward manipulated value to the control target, wherein the device obtains, for each of a plurality of positions at which the control target is to be arranged, a measurement result of a first output response of the control target obtained when giving a first manipulated value to the control target, determines a reference value of the first output response, based on the measurement results respectively obtained at the plurality of positions, determines a second manipulated value by arraying a plurality of first manipulated values in time-series based on a relationship between the first manipulated value and the reference value, and sets the feedforward manipulated value based on the second manipulated value.