Lithographic Apparatus Eigenmode Coupling Compensation
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Solution Overview
Problem
Conventional lithographic apparatuses fail to effectively compensate for eigenmode coupling, leading to positioning errors due to non-rigid body movements caused by eigenmode vibrations, which are not addressed by existing compensation methods like gain balancing and gain scheduling.
Innovation Solution
A lithographic apparatus with a positioning system that measures and compensates for eigenmode coupling between movement along one axis and the measured position along another axis, using feedback control systems and modeling units to predict and mitigate disturbances caused by eigenmode vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional positioning systems are used to move components along one axis, then basic positioning function is achieved, but eigenmode coupling causes positioning errors along other axes
Solution Approach 1:
The patent implements feedback control by measuring the actual position of the component along the second axis and using this information to adjust the movement control along the first axis. The positioning system continuously monitors position deviations caused by eigenmode coupling and applies corrective actions to maintain accurate positioning, thereby resolving the contradiction between achieving basic positioning function and maintaining positioning accuracy despite eigenmode vibrations.
Solution Approach 2:
The patent introduces an intermediary control mechanism that decouples the eigenmode vibrations from the positioning accuracy. By measuring position along one axis and using this as an intermediary signal to control movement along another axis, the system mediates the harmful eigenmode coupling effects and prevents them from degrading positioning reliability.
2Measurement precision
If sensors are used to detect component position, then position measurement is achieved, but sensors cannot discriminate between rigid body movement and non-rigid body movement
Solution Approach 1:
The patent segments the movement detection into two distinct components: rigid body movement and non-rigid body eigenmode vibrations. By using multiple sensors positioned at different locations and analyzing their relative measurements, the system can distinguish between overall component movement (rigid body) and localized vibrations (non-rigid body), thereby resolving the difficulty of movement type discrimination while maintaining measurement precision.
Solution Approach 2:
The patent adds an additional measurement dimension by monitoring position along a second axis that is perpendicular to the primary movement axis. This dimensional expansion allows the system to detect and differentiate eigenmode coupling effects from actual positioning movements, enabling discrimination between rigid and non-rigid body movement while preserving measurement accuracy.
3Ease of operation
If positioning control is adjusted based on sensor detection, then positioning function is achieved, but eigenmode coupling creates real motion and positioning errors
Solution Approach 1:
The patent implements feedback control by continuously monitoring the actual position of the component along the second axis and using this information to adjust the movement control along the first axis. This feedback mechanism allows the positioning control to compensate for eigenmode coupling effects in real-time, maintaining positioning accuracy while preserving ease of operation.
Solution Approach 2:
The patent dynamically changes control parameters based on measured position deviations. By adjusting control signals in response to detected eigenmode vibrations, the system modifies its operation to counteract positioning errors, thereby maintaining manufacturing precision without complicating the overall positioning control function.
Data Source
AI summary
A lithographic apparatus can include a component and a positioning system operatively coupled and configured to move the component along a first axis. The positioning system can be configured to measure a position of the component along a second axis or a third axis. The positioning system can also be configured to control movement of the component so as to compensate for an effect of eigenmode coupling between the movement of the component along the first axis and the measured position of the component along the second axis or the third axis. In some embodiments, the component is a reticle stage or a wafer stage.