Relay Optical System for EUVL Field Stop Conjugation
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Solution Overview
Problem
In EUVL exposure apparatuses, the second partial field stop blocks light intended for the photosensitive substrate, affecting imaging quality, and it is challenging to minimize this impact due to the difficulty in reducing the distance between the field stop and the mask without mechanical interference.
Innovation Solution
An illumination optical apparatus with a relay optical system that optically conjugates the positions of the first and second partial field stops, allowing the second partial field stop to be positioned between the illumination optical system and the mask without blocking reflected light, thereby reducing adverse effects on imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the second partial field stop is arranged in the vicinity of the mask to limit the light flux reflected by the mask, then the arcuate profile line of the static exposure region is formed, but the light flux intended for the photosensitive substrate is blocked, adversely affecting imaging quality
Solution Approach 1:
The patent introduces a relay optical system that creates an intermediate optical image plane, effectively adding a dimensional transformation in the optical path. The second partial field stop is positioned at this intermediate plane rather than directly at the mask, allowing it to define the arcuate profile while the optical system ensures the reflected light flux reaches the photosensitive substrate without being blocked. This dimensional change in the optical path resolves the contradiction between forming the correct exposure region shape and maintaining imaging quality.
2Manufacturing precision
If the distance between the second partial field stop and the mask is decreased to reduce light blocking, then the adverse effect on imaging is reduced, but mechanical interference between the moving mask and field stop becomes a problem
Solution Approach 1:
The relay optical system acts as an intermediary between the second partial field stop and the mask. By positioning the field stop at an intermediate optical image plane and using the relay optical system to transfer the optical information, the patent achieves effective light flux control without requiring the field stop to be in immediate proximity to the mask. This intermediary mechanism reduces the risk of mechanical interference while maintaining imaging quality.
3Shape
If the second partial field stop is positioned between the illumination optical system and the mask, then the static exposure region is properly formed, but the reflected light flux towards the photosensitive substrate is shielded
Solution Approach 1:
The patent replaces the direct mechanical positioning approach with an optical system approach. Instead of positioning the second partial field stop directly at the mask plane and relying on mechanical precision, the invention uses the relay optical system to create an intermediate optical image. This substitution allows the field stop to be positioned at a different location in the optical path while achieving the same functional result of defining the static exposure region without blocking the reflected light flux.
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 configuration ensures satisfactory exposure conditions by preventing light flux limitations that would otherwise impair imaging on the photosensitive substrate, allowing for improved device manufacturing performance.
Implementation Method 1
an illumination optical system including a plurality of reflection mirrors (19a, 19b) arranged to guide illumination light flux to a mask (M)
Data Source
AI summary
An illumination optical apparatus of the present invention includes an illumination optical system having a plurality of reflection mirrors arranged to guide illumination light flux to an irradiated plane. A first partial field stop is arranged in an optical path of the illumination optical system to form a first profile line of an illumination region that is to be formed on the irradiated plane. A second partial field stop is arranged between the illumination optical system and the irradiated plane to form a second profile line of the illumination region. The illumination optical system includes a relay optical system for substantially optically conjugating the position of the first partial field stop and the position of the second partial field stop.