Lithographic Projection Sensor Frame Damping Control
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Solution Overview
Problem
Lithographic apparatuses face a decrease in projection accuracy due to counter-effective attempts to compensate for disturbances in the sensor frame, resulting in an increase in line of sight error instead of the intended reduction.
Innovation Solution
A lithographic apparatus with a control device that uses acceleration and position signals to derive damping force signals and estimated line of sight errors, driving actuators to dampen the sensor frame and compensate for these errors, employing a matrix calculation to determine actuator drive signals from sensor frame damping force signals and estimated line of sight errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sensor frame actuators are provided to dampen the sensor frame and compensate for disturbances, then projection accuracy should improve, but line of sight error increases instead
Solution Approach 1:
The control device uses acceleration sensors to measure sensor frame acceleration and position sensors to measure sensor frame position, then feeds this information back to calculate damping force signals and estimated line of sight errors. The actuators use this feedback to compensate for disturbances, resolving the contradiction by continuously adjusting based on actual measurements rather than relying on fixed compensation parameters.
Solution Approach 2:
The system dynamically changes the damping force parameters based on real-time acceleration and position measurements. The control device calculates damping force signals from sensor frame acceleration and position signals, adjusting the actuator forces adaptively to compensate for disturbances while minimizing line of sight errors, rather than using fixed compensation values.
2Object-affected harmful factors
If vibration isolators are used to isolate the sensor frame from vibrations in the force frame, then disturbances should be reduced, but line of sight error increases due to translation of vibrations into disturbance forces
Solution Approach 1:
The system converts the harmful vibration disturbances into useful information by using acceleration sensors to measure the vibrations. The control device then calculates damping force signals from these measurements and uses actuators to compensate for the disturbances, turning the previously harmful vibrations into data for accurate compensation and line of sight error reduction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces line of sight errors by compensating for sensor frame disturbances, maintaining or improving projection accuracy while minimizing additional line of sight errors generated by actuator forces.
Implementation Method 1
The sensor frame is supported by the force frame using vibration isolators. Hence, the vibration isolators aim to keep vibrations acting in the force frame away from the sensor frame
Implementation Method 2
acceleration sensors and/or sensor frame position sensors may be provided to measure an acceleration resp. a position of the sensor frame
Implementation Method 3
a plurality of actuators arranged between the sensor frame and the force frame and configured to exert a force between the sensor frame and the force frame
Data Source
AI summary
A lithographic apparatus comprises a projection system comprising position sensors to measure a position of optical elements of the projection system. The positions sensors are referenced to a sensor frame. Damping actuators damp vibrations of the sensor frame. A control device drives the actuators and is configured to derive sensor frame damping force signals from at least one of the acceleration signals and the sensor frame position signals, derive an estimated line of sight error from the position signals, determine actuator drive signals from the sensor frame damping force signals and the estimated line of sight error, drive the actuators using the actuator drive signals to dampen the sensor frame and to at least partly compensate the estimated line of sight error.