EUV Facet Mirror Assembly Spacer Alignment
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Solution Overview
Problem
In EUV lithography apparatuses, swapping facet mirrors can lead to unwanted displacement of the object field in the field plane due to facet misalignment, which is difficult to prevent with existing adjustment methods.
Innovation Solution
A method for assembling facet mirrors involves determining the positions of facets relative to interfaces, calculating the actual object field position, and arranging spacers between the interfaces and a support structure to bring the object field to a target position, thereby avoiding complex adjustments of other optical elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If facet mirrors are swapped in EUV lithography apparatuses, then maintenance and contamination removal are enabled, but facet misalignment occurs causing object field displacement
Solution Approach 1:
The patent applies preliminary action by pre-determining the positions of facets relative to interfaces and pre-calculating the actual object field position before the mirror swap. This allows the spacers to be pre-configured with precise thicknesses that will compensate for any misalignment, ensuring the object field returns to its target position after swapping without requiring post-swap realignment operations.
Solution Approach 2:
The patent introduces spacers as intermediary elements between the facet mirror interfaces and the support structure. These spacers act as mediators that physically compensate for position deviations of the facets, allowing the mirror to be swapped while maintaining precise optical alignment through the corrective function of the spacers.
2Manufacturing precision
If traditional adjustment methods are used after mirror swap, then facet alignment can be corrected, but the process becomes complex and time-consuming
Solution Approach 1:
The patent eliminates complex post-swap adjustment procedures by performing all necessary calculations and determinations beforehand. The spacers are designed with specific thicknesses based on pre-calculated facet positions and object field deviations, so that simply installing the spacers automatically corrects any alignment issues without requiring complex adjustment mechanisms or procedures.
Solution Approach 2:
The patent replaces complex mechanical adjustment systems with a simpler spacer-based compensation system. Instead of using adjustable mechanisms, motors, or complex alignment procedures after mirror swapping, the solution uses precisely dimensioned spacers that provide automatic mechanical compensation for misalignment, greatly simplifying the overall process.
3Manufacturing precision
If spacers are arranged to compensate for facet position deviations, then object field displacement is prevented, but additional assembly steps are required
Solution Approach 1:
The patent performs all complex calculations and determinations in advance, before the actual assembly process. The spacers are designed with predetermined thicknesses based on pre-calculated facet positions and required compensation amounts. This preliminary preparation transforms a potentially complex assembly process into a straightforward installation of pre-configured components.
Solution Approach 2:
The patent creates a precise digital model or calculation framework that determines the exact specifications of spacers needed for compensation. This computational copying of the required geometric relationships allows the physical spacers to be manufactured with precise dimensions that automatically implement the alignment correction without requiring complex assembly procedures.
Data Source
AI summary
A method of assembling a facet mirror of an optical system, in which facets of the facet mirror are imaged onto a field plane of the optical system, includes: a) determining positions of the facets of the facet mirror relative to interfaces of the facet mirror, with the aid of which the facet mirror is able to be connected to a support structure; b) calculating an actual position of an object field of the optical system arising for the facet mirror in the field plane; and c) arranging spacers between the interfaces and the support structure so that the object field in the field plane is brought from the calculated actual position to a target position.