Mirror Segment Mounting for EUV Lithography Deformation Control
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Solution Overview
Problem
The production of high-numerical-aperture projection lenses for EUV microlithography faces challenges due to the large size and weight of mirrors, which increase production costs and complexity, and the introduction of mechanical stresses from mounting elements, leading to deformation issues.
Innovation Solution
The use of a mirror segment arrangement with separate mirror segments connected via mounting elements, where at least one mounting element extends into the region of an adjacent mirror segment, reducing the need for larger production machines and minimizing deformation by avoiding direct mechanical contact on the rear side of the mirror.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the image-side numerical aperture (NA) is increased, then the imaging performance is improved, but the mirror surfaces must be enlarged which increases production costs and complexity
Solution Approach 1:
The patent divides a large mirror into multiple smaller mirror segments. Each segment can be manufactured separately using standard production equipment, avoiding the need for excessively large processing machines. The segments are then assembled to form the complete mirror surface, enabling high NA imaging while maintaining manageable production complexity and cost.
2Ease of manufacture
If mounting elements are installed directly on the rear side of the mirror, then the mounting process is simplified, but mechanical stresses and deformations are significantly increased
Solution Approach 1:
The patent transitions the mounting element installation from the rear side (z-dimension) to the lateral region (x-y plane) of the mirror segment. By positioning mounting elements in the lateral region rather than on the rear surface, the design avoids direct mechanical coupling that would transmit stresses to the optically active surface, thereby reducing deformations while maintaining ease of mounting through accessible positioning.
Solution Approach 2:
The patent introduces the lateral region of the mirror segment as an intermediary zone between the mounting elements and the optically active surface. This spatial intermediary allows mounting elements to be positioned where they can securely attach to the mirror segment without their mechanical stresses directly affecting the precision-critical rear surface and optical path.
3Ease of manufacture
If mounting elements are installed outside the mirror base body, then the structural space is enlarged, but the overall system size increases which is undesirable
Solution Approach 1:
The patent merges the mounting element installation area with the lateral region of the mirror segment itself. Instead of requiring separate external mounting structures that would increase overall system size, the design utilizes the existing lateral space of the mirror segment as the mounting zone, effectively combining the optical component and mounting infrastructure into a single integrated structure.
Data Source
AI summary
The disclosure relates to optical arrangements in a microlithographic projection exposure apparatus. In accordance with one aspect, an optical arrangement has at least one mirror segment arrangement including a plurality of separate mirror segments. The mirror segments are connected to a carrying structure of the projection exposure apparatus via mounting elements. At least one of the mounting elements, which is assigned to a first one of the mirror segments, extends, on the opposite side to the optically active surface of the mirror segment arrangement, at least partly into the region of a second mirror segment of the mirror segment arrangement. The second mirror segment is adjacent to the first mirror segment.