Compact Metrology Frame for Lithographic Optical Element Positioning
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Solution Overview
Problem
Lithographic apparatuses face challenges with large dimensions and measurement inaccuracies due to bulky metrology frame structures, which are prone to vibrations and misalignment, affecting the precision of optical element positioning and orientation measurement.
Innovation Solution
A compact metrology frame structure is positioned within a rectangle that envelops the optical elements, patterning device stage, and substrate stage, with a reduced size and increased stiffness, using a combination of optical encoder and interferometer systems to enhance measurement precision and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bulky metrology frame structure is used to measure optical elements, then the measurement system can be integrated into the lithographic apparatus, but the apparatus dimensions increase and measurement precision deteriorates due to vibrations and misalignment
Solution Approach 1:
The patent extracts the measurement function from a separate bulky metrology frame and integrates it directly into the projection system structure. The measurement system is taken out as an independent measurement beam path that uses the existing projection system components (mirrors, beam path) for positioning, eliminating the need for a separate large-scale metrology frame structure
Solution Approach 2:
The patent merges the measurement system with the projection system by using common structural elements and beam paths. The measurement mirrors are integrated into the projection system's mirror structure, and the measurement beam shares the projection beam path, combining two functions into a unified system that reduces overall dimensions
2Reliability
If a bulky metrology frame structure is used, then the measurement system can be implemented, but the frame stiffness decreases and resonance frequency lowers, causing vibrations that affect measurement accuracy
Solution Approach 1:
The measurement system is merged with the projection system's rigid structure, using the same support framework and mounting points. This integration allows the measurement components to benefit from the projection system's inherent structural stiffness, eliminating the need for a separate flexible metrology frame
Solution Approach 2:
The patent replaces the mechanical metrology frame structure with an optical measurement approach that uses laser interferometry. Instead of relying on a physical frame's mechanical stability, the system uses optical interference patterns to measure positions, substituting mechanical structural requirements with optical measurement principles
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 design reduces the size of the lithographic system, improves measurement precision, and enhances the stiffness and resonance frequency of the metrology frame, leading to improved accuracy in optical element positioning and orientation measurement.
Implementation Method 1
part of an encoder measurement system configured to measure the position of the optical element
Implementation Method 2
part of an interferometer measurement system configured to measure the position and/or orientation of the optical element
Data Source
AI summary
A lithographic apparatus includes a projection system which includes a plurality of optical elements configured to project a beam of radiation onto a radiation sensitive substrate. The lithographic apparatus also includes a metrology frame structure which includes a part of one or more optical element measurement systems to measure the position and/or orientation of at least one of the optical elements. The plurality of optical elements, a patterning device stage, and a substrate stage are arranged such that, in a two dimensional view on the projection system, a rectangle is defined such that it envelops the plurality of optical elements, the patterning device stage, and the substrate stage. The rectangle is as small as possible. The metrology frame structure is positioned within the rectangle.