Lithographic Projection System Aberration Compensation
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Solution Overview
Problem
Lithographic apparatuses face challenges in accurately applying patterns to substrates due to optical aberrations and line-of-sight errors caused by the positions of optical elements, which existing technologies struggle to fully correct.
Innovation Solution
A projection system with a controller that adjusts a second set of optical elements based on the positions of a first set, using sensors and actuators to compensate for aberrations and errors, and also adjusts the patterning device support structure and substrate table to further reduce residual errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the positions of optical elements are adjusted to correct optical aberrations, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The system employs sensors to detect the actual positions of optical elements and uses this feedback information to drive actuators that adjust the elements, creating a closed-loop control system that automatically compensates for positional deviations and optical aberrations
Solution Approach 2:
A controller acts as an intermediary between the sensors and actuators, processing sensor data and generating appropriate actuator commands to coordinate the adjustment of multiple optical elements for optimal aberration compensation
2Manufacturing precision
If multiple sensors and actuators are added to correct optical aberrations, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The optical element adjustment system is divided into multiple independent sensor-actuator pairs, each responsible for monitoring and correcting specific optical elements, allowing modular implementation and independent optimization of each correction channel
3Manufacturing precision
If optical elements are adjusted in real-time to compensate for positional deviations, then manufacturing precision is improved, but speed of operation decreases
Solution Approach 1:
The system performs position measurements and compensation adjustments during idle periods or between exposures, preparing the optical elements for optimal performance before the actual exposure process begins, thereby minimizing interference with production speed
Data Source
AI summary
A projection system (PS1) for a lithographic apparatus comprises: an optical path (100); a plurality of sensors (S1-S4); one or more actuators (A1-A4); and a controller (CN). The optical path is operable to receive an input radiation beam (Bin) and to project an output radiation beam (Bout) onto a substrate to form an image. The optical path comprises: a plurality of optical elements (M1-M4), the plurality of optical elements comprising: a first set of at least two optical elements (M1, M4) and a second set of at least one optical element (M2, M3). Each sensor is associated with one of the plurality of optical elements and is operable to determine a position of that optical element. Each actuator is associated with one of the second set of optical elements and is operable to adjust that optical element. The controller is operable to use the one or more actuators to adjust the second set of optical elements in dependence on the determined position of the first set of optical elements so as to at least partially compensate for optical aberrations and/or line-of-sight errors caused by the positions of the first set of optical elements.