EUV Mirror Positioning via Direct Interferometric Measurement
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Solution Overview
Problem
Microlithographic projection exposure apparatuses face challenges in accurately determining the relative position of optical components, particularly EUV mirrors, due to the need for external measurement structures and reference elements, which increase costs and complexity while compromising positional accuracy.
Innovation Solution
An optical system that uses direct length measurement sections between optical components to determine their relative positions in six degrees of freedom, eliminating the need for external reference elements and allowing for a more sensitive and accurate measurement arrangement, potentially using a Stewart-Gough platform geometry with overlapping measurement sections and interferometric or capacitive measurement principles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external measurement structures and reference elements are used to determine the relative position of optical components, then the measurement system can be implemented, but the manufacturing costs and device complexity increase
Solution Approach 1:
The invention extracts the measurement function from external reference structures and integrates it directly into the optical components themselves. The mirrors are equipped with integrated measurement markers that serve as both optical elements and measurement references, eliminating the need for separate external measurement structures and reducing overall system complexity while maintaining measurement precision.
Solution Approach 2:
The invention merges the measurement reference function with the optical mirror components. The measurement markers are directly integrated onto the mirrors, combining the optical function and measurement reference function into a single component, thereby reducing device complexity and the number of separate parts required.
2Measurement precision
If external measurement structures and reference elements are used to determine the relative position of optical components, then the measurement system can be implemented, but manufacturing costs increase
Solution Approach 1:
The invention merges the measurement reference function with the optical mirror components. The measurement markers are directly integrated onto the mirrors, combining the optical function and measurement reference function into a single component, thereby reducing device complexity and the number of separate parts required.
Solution Approach 2:
The invention uses simple, easily manufacturable measurement markers that can be produced at low cost and integrated directly onto the mirrors. These markers are designed to be simple geometric features that can be manufactured using standard processes, avoiding the need for expensive specialized measurement components.
3Measurement precision
If length measurement sections extend directly between optical components, then measurement accuracy improves, but the measurement arrangement becomes more sensitive to positioning requirements
Solution Approach 1:
The invention uses laser interferometry to create an equipotential measurement field between the mirrors. The laser wavelength provides a universal reference that is insensitive to gravitational potential differences and thermal expansion, allowing direct measurement between components without requiring extremely precise mechanical positioning of the measurement sections themselves.
Solution Approach 2:
The invention replaces mechanical measurement sections with optical interferometric measurement. Instead of using physical rods or mechanical linkages that would require precise positioning, the system uses laser light waves to measure the relative position and orientation of mirrors, eliminating the need for mechanically precise measurement section positioning.
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 reduces manufacturing costs, decouples positional measurement from actuator systems, and achieves high accuracy in mirror positioning, enabling precise EUV imaging with reduced aberrations and assembly time, allowing for accurate adjustment during mounting without additional wavelengths.
Implementation Method 1
EP 1 465 015 A1 discloses, among other things, a projection exposure apparatus designed for EUV where the relative positions of the mirrors with respect to each other are measured directly by an interferometric mechanism or a capacitive mechanism.
Implementation Method 2
EP 1 465 015 A1 discloses, among other things, a projection exposure apparatus designed for EUV where the relative positions of the mirrors with respect to each other are measured directly by an interferometric mechanism or a capacitive mechanism.
Data Source
AI summary
An optical system, such as a microlithographic projection exposure apparatus, includes a first optical component, a second optical component, and a measurement arrangement for determining the relative position of the first optical component and the second optical component in six degrees of freedom. The measurement arrangement is adapted to determine the relative position of the first optical component and the second optical component over six different length measurement sections. The length measurement sections extend directly between the first optical component and the second optical component.