Segmented Mirror Arrangement for EUV Projection Objectives
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Solution Overview
Problem
Microlithographic projection exposure apparatuses face challenges in increasing numerical aperture due to limitations in mirror size, manufacturing complexity, and gravity-induced deformation, as well as shadowing issues with larger mirrors.
Innovation Solution
A projection objective with a mirror segment arrangement comprising separate mirror segments, allowing for higher numerical apertures by superposing partial beam paths and using an obscuration shutter to minimize imaging errors from intermediate spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If mirror dimensions are increased to achieve higher numerical aperture, then numerical aperture is improved, but manufacturing precision deteriorates due to difficulty in reducing long-wave surface errors
Solution Approach 1:
The projection objective divides the mirror system into multiple separate mirror segments (first mirror segment, second mirror segment, third mirror segment) instead of using a single large mirror. This segmentation allows each individual segment to be manufactured with high precision while collectively achieving the required large effective aperture for high numerical aperture operation.
2Area of moving object
If mirror dimensions are increased to achieve higher numerical aperture, then numerical aperture is improved, but device complexity worsens due to larger processing machines and stricter machining requirements
Solution Approach 1:
By segmenting the mirror system into multiple smaller mirror segments, the patent enables use of standard-sized processing machines for manufacturing each segment, avoiding the need for extremely large specialized processing equipment that would be required for a single large mirror of equivalent total area.
3Area of moving object
If mirror dimensions are increased to achieve higher numerical aperture, then numerical aperture is improved, but reliability worsens due to gravity-induced deformation
Solution Approach 1:
The patent divides the mirror system into multiple smaller mirror segments that can be individually supported and positioned. This segmentation reduces the weight and gravitational deformation of each individual segment compared to a single large mirror, while maintaining the required total optical aperture for high numerical aperture operation.
4Area of moving object
If mirror dimensions are increased to achieve higher numerical aperture, then numerical aperture is improved, but object-generated harmful factors worsen due to shadowing of illumination beam path
Solution Approach 1:
By using multiple separated mirror segments instead of a single large mirror, the patent reduces shadowing effects in the illumination beam path. The segmented configuration allows illumination beams to access multiple segments from different angles, minimizing shadowing while maintaining the required effective aperture for high numerical aperture operation.
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
Enables higher numerical apertures while reducing manufacturing complexity and gravity-induced deformation, and minimizing imaging errors by using a segmented mirror configuration and obscuration shutter to manage mirror segment intermediate spaces.
Implementation Method 1
Mirrors are used as optical components for the imaging process in projection objectives designed for the EUV range
Implementation Method 2
using an obscuration shutter to minimize imaging errors from intermediate spaces
Data Source
Figure 1
Figure 2
Figure 3a~3c
AI summary
The invention concerns a projection objective of a microlithographic projection exposure apparatus designed for EUV, for imaging an object plane illuminated in operation of the projection exposure apparatus into an image plane, wherein the projection objective has at least one mirror segment arrangement (160, 260, 280, 310, 410, 500) comprising a plurality of separate mirror segments (161 -163; 261-266, 281 -284; 31 1, 312; 41 1, 412; 510-540); and wherein associated with the mirror segments of the same mirror segment arrangement are partial beam paths which are different from each other and which respectively provide for imaging of the object plane (OP) into the image plane (IP), wherein said partial beam paths are superposed in the image plane (IP) and wherein at least two partial beams which are superposed in the same point in the image plane (IP) were reflected by different mirror segments of the same mirror segment arrangement.