Lithographic Positioning System Motor Constant Compensation
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Solution Overview
Problem
Lithographic apparatuses face challenges in achieving high positioning accuracy due to motor position-dependent motor constants, which introduce disturbances and result in overlay errors and imaging problems during the scanning process.
Innovation Solution
A positioning system with a motor having a motor position-dependent motor constant is compensated using a control system that includes a set-point generator and a controller with a compensator, which adjusts the drive signal based on a reference signal and a motor position-dependent compensation value to mitigate these disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a motor with constant motor constant is used, then the control system is simple, but positioning accuracy deteriorates due to motor position-dependent disturbances
Solution Approach 1:
The patent transforms the motor constant from a fixed parameter to a position-dependent parameter K(x). By measuring the actual motor constant at different positions and creating a compensation profile, the system accounts for positional variations without requiring a completely different motor design, thus resolving the contradiction between simplicity and precision
Solution Approach 2:
The patent implements a feedback mechanism where the motor position is continuously monitored and used to select the appropriate motor constant value from the compensation profile. This closed-loop approach allows the control system to adapt to positional variations and maintain high positioning accuracy while keeping the overall system architecture relatively simple
2Manufacturing precision
If motor position-dependent motor constant is compensated, then positioning accuracy is improved, but control system complexity increases
Solution Approach 1:
The patent performs preliminary measurement and characterization of the motor constant at different positions before actual operation. This pre-characterization data is stored as a compensation profile, which is then used during normal operation without requiring real-time complex calculations, thus improving positioning accuracy while limiting the increase in control system complexity
Solution Approach 2:
The patent uses a lookup table approach with pre-calculated compensation values instead of implementing complex real-time calculations. This disposable pre-computed data approach provides accurate compensation without requiring expensive or complex real-time computational resources in the control system
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 solution enhances the positioning accuracy of the lithographic apparatus, reduces overlay errors, and improves imaging quality by effectively compensating for the motor position-dependent motor constant, thereby meeting the increasing requirements for positioning precision.
Implementation Method 1
a motor having a motor position dependent motor constant defining a relation between a motor input and a motor output
Implementation Method 2
a control system to drive the motor, the control system including a set-point generator to provide a reference signal based on a desired position of the support structure, and a controller to provide a drive signal to the motor based on the reference signal, wherein the controller includes a compensator which is configured to at least partially compensate the drive signal for the motor position dependent motor constant
Data Source
AI summary
A lithographic apparatus includes a positioner configured to position a first part of the apparatus relative to a second part of the apparatus, the positioner including a motor having a motor position dependent motor constant defining a relation between a motor input and a motor output, and a control system to drive the motor, the control system including a set-point generator to provide a reference signal based on a desired position of the first part relative to the second part, and a controller to provide a drive signal to the motor based on the reference signal, wherein the controller includes a compensator which is configured to at least partially compensate the drive signal for the motor position dependent motor constant. The invention further relates to a positioner, a method to optimize the positioning system, and a method to derive a motor position dependent motor constant.