Lithographic Stage Positioning via Reflective Shape Correction
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Solution Overview
Problem
Current lithographic apparatuses face challenges in achieving accurate positioning of stages, which directly impacts the projection accuracy of patterns onto substrates due to inaccuracies in reflective surfaces used by optical position sensors.
Innovation Solution
Incorporating an optical shape sensor to determine the shape of reflective surfaces, allowing for precise correction of position measurements by the optical position sensor, thereby enhancing the accuracy of stage positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical position sensor is used to determine the position of the stage, then the positioning capability is provided, but the measurement precision is limited due to inaccuracies in the reflective surface
Solution Approach 1:
An optical shape sensor is introduced as an intermediary device to measure the shape of the reflective surface. This separate measurement capability allows the position sensor to function without being directly affected by reflective surface inaccuracies, as the shape information can be used to compensate for or correct position measurements.
Solution Approach 2:
The system implements feedback by using the shape measurement data from the optical shape sensor to correct or compensate for position measurement errors. The measured shape information feeds back into the position determination process, improving overall measurement precision by accounting for reflective surface deviations.
2Manufacturing precision
If the stage positioning system uses a reflective surface as reference, then the positioning function is enabled, but the manufacturing precision is reduced due to deviations in the reflective surface shape
Solution Approach 1:
The optical shape sensor acts as an intermediary that independently characterizes the reflective surface shape. This allows the positioning system to account for shape deviations without requiring the reflective surface itself to be perfectly accurate, thereby maintaining manufacturing precision despite surface imperfections.
Solution Approach 2:
Shape measurement feedback is used to correct position measurements, ensuring that overlay accuracy is maintained even when the reflective surface has shape deviations. The system continuously monitors and compensates for shape changes that would otherwise degrade manufacturing precision.
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 enables more accurate stage positioning, improving the overlay accuracy of patterns projected onto substrates by accounting for deviations in the reflective surface shape, leading to better manufacturing outcomes in semiconductor production.
Implementation Method 1
one of the stage and the reference structure comprises a reflective surface, an optical position sensor arranged at the other one of the stage and the reference structure and configured to determine a position of the reflective surface relative to the optical position sensor
Implementation Method 2
an optical shape sensor configured to determine a shape of the reflective surface
Data Source
AI summary
The invention provides a stage system comprising a stage (ST) which is movable in respect of a reference structure. One of the stage and the reference structure comprises a reflective surface (REFS). An optical position sensor (IF1) is arranged at the other one of the stage and the reference structure and is configured to determine a position of the reflective surface relative to the optical position sensor. An optical shape sensor (IF2) is configured to determine a shape of the reflective surface. The stage system further comprises a position measurement controller configured to derive a stage position of the stage from the position of the reflective surface relative to the optical position sensor and from the shape of the reflective surface as determined by the optical shape sensor.