EUV Illumination Optical Apparatus Debris Partitioning
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Solution Overview
Problem
In EUV exposure apparatuses, debris generated in the light source section adheres to the reflecting surfaces of the illumination and projection optical systems, reducing reflectance and necessitating frequent system exchanges, which increases maintenance costs and affects image accuracy.
Innovation Solution
A reflection type illumination optical apparatus with a partition wall member separating different vacuum environments, featuring an aperture at the position where the cross-sectional area of the illumination light flux is smallest, minimizing gas flow and debris passage between the illumination and projection optical systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If the illumination optical system uses a reflection type structure near the light source section, then the reflecting optical member can be individually exchanged when reflectance is lowered, but the projection optical system requires entire system exchange when one member's reflectance deteriorates
Solution Approach 1:
The optical system is divided into two separate vacuum chambers: the illumination optical system in a first vacuum chamber and the projection optical system in a second vacuum chamber. This segmentation allows the illumination optical members to be individually exchanged without affecting the projection optical system, resolving the contradiction between ease of repair and device complexity.
2Object-generated harmful factors
If the aperture of the partition wall member is arranged at the position where the cross-sectional area of light flux is smallest, then the amount of debris passage is reduced, but the structural positioning becomes more critical
Solution Approach 1:
A partition wall member with an aperture is introduced as an intermediary structure between the illumination and projection optical systems. The aperture is positioned at the location where the light flux cross-sectional area is minimal, allowing light passage while blocking debris. This intermediary structure effectively reduces debris passage to the projection optical system.
3Object-generated harmful factors
If the partition wall member separates different vacuum environments, then debris adhesion to projection optical system is reduced, but the system complexity and vacuum maintenance requirements increase
Solution Approach 1:
The vacuum environment is segmented into two separate chambers: a first vacuum chamber for the illumination optical system and a second vacuum chamber for the projection optical system. The partition wall member with aperture connects these chambers. This segmentation protects the projection optical system from debris adhesion while maintaining necessary vacuum conditions.
4Manufacturing precision
If multiple reflecting optical members are installed in a barrel for the projection optical system, then image projection accuracy is maintained, but the entire system must be exchanged when one member deteriorates
Solution Approach 1:
The projection optical system is isolated in a separate second vacuum chamber, segmented from the illumination optical system. This allows the high-precision multi-member barrel structure to maintain image projection accuracy while protecting it from debris. The segmentation enables independent maintenance of each system, improving ease of repair.
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 reduces the adhesion of debris to the projection optical system's reflecting surfaces, prolonging the time before reflectance deterioration, lowering maintenance costs, and maintaining high illuminance and image accuracy.
Implementation Method 1
a partition wall member separating a first space in which the first reflecting surface is arranged and a second space in which the second reflecting surface is arranged into mutually different vacuum environments or pressure-reduced environments
Implementation Method 2
a first reflecting surface which reflects the illumination light reflected by each of the plurality of reflecting mirror elements
Implementation Method 3
a second reflecting surface which guides the illumination light reflected by the first reflecting surface to the illumination objective surface
Data Source
AI summary
An illumination optical apparatus which illuminates an illumination objective surface with an exposure light includes: an illumination optical system having a curved mirror and a concave mirror and defining a position substantially conjugate with the illumination objective surface between the curved and concave mirrors; and a second aperture plate separating a space in which the curved mirror is arranged and a space in which the concave mirror is arranged into mutually different vacuum environments or pressure-reduced environments, and having an aperture through which the exposure light passes, the aperture being arranged at a position at which a cross-sectional area of the exposure light is smallest, or in the vicinity of the position. It is possible to decrease the amount of passage of minute particles such as debris in relation to any downstream-side optical system.