EUV Illumination Optical Unit Facet Mirror Segmentation
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Solution Overview
Problem
Current illumination optical units for projection lithography lack flexibility in defining illumination fields, particularly in achieving efficient far-field coverage and optimizing thermal load management.
Innovation Solution
The illumination optical unit employs a first facet mirror with individually tiltable mirror groups that can be grouped non-contiguously and assigned to further facets, allowing for efficient EUV light distribution and flexible occupancy, with selection individual mirrors that can adjust between tilting positions to optimize illumination settings and reduce thermal load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If individual mirror groups are formed from non-contiguous individual mirror subgroups, then flexibility in defining illumination fields and far-field coverage are improved, but device complexity increases
Solution Approach 1:
The first facet mirror is divided into multiple individually tiltable mirror groups, where each mirror group can be independently controlled and positioned. This segmentation allows non-contiguous mirror subgroups to be grouped together, enabling flexible definition of illumination fields and achievement of high far-field coverage while managing device complexity through modular control
Solution Approach 2:
The individual mirror groups are made tiltable and reconfigurable, allowing dynamic adjustment of their positions and orientations. This dynamic capability enables the system to adapt illumination patterns flexibly by repositioning non-contiguous mirror subgroups to different locations, achieving versatile illumination field definitions without permanent structural complexity
2Adaptability or versatility
If individual mirror groups are made tiltable and reconfigurable, then illumination settings flexibility is improved, but control complexity increases
Solution Approach 1:
The control system is segmented to manage individual mirror groups independently, with each group having its own tilt control mechanisms. This segmentation of control allows flexible illumination settings through coordinated adjustment of multiple mirror groups while keeping the control architecture manageable through modular organization
Solution Approach 2:
The tiltable mirror groups serve multiple functions: they can be individually positioned to create different illumination patterns, grouped non-contiguously to achieve specific far-field coverage, and reconfigured to adapt to various illumination requirements. This multi-functionality maximizes illumination settings flexibility while avoiding the need for separate dedicated mechanisms for each function
3Temperature
If the further facet mirror is arranged at a distance from the pupil plane, then thermal load management is improved, but optical path complexity increases
Solution Approach 1:
The further facet mirror acts as an intermediary optical element positioned at a distance from the pupil plane, serving as a mediator between the illumination optical unit and the downstream imaging optical unit. This intermediate positioning allows thermal load management by creating spatial separation while maintaining optical functionality through the mirror's reflective guidance of illumination light
4Area of stationary object
If non-contiguous individual mirror subgroups are grouped together, then far-field coverage is improved, but manufacturing complexity increases
Solution Approach 1:
The first facet mirror is manufactured as an array of individually controllable mirror segments or subgroups that can be independently positioned. This segmentation approach enables non-contiguous subgroups to be grouped together to achieve high far-field coverage while simplifying manufacturing through modular assembly of standardized mirror units with integrated tilt mechanisms
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 achieves high far-field coverage (>80%) and flexible illumination settings, reducing thermal load and improving stability and throughput while maintaining efficient use of EUV light.
Implementation Method 1
The two facet mirrors are embodied for reflecting, overlaid guidance of partial beams of a beam of the EUV illumination light to the object field
Data Source
AI summary
An illumination optical unit for projection lithography illuminates an illumination field, in which an object field of a downstream imaging optical unit and an object to be illuminated are arrangeable, with illumination light of an EUV light source. The illumination optical unit includes two facet mirrors for reflecting, overlaid guidance of partial beams of a beam of the EUV illumination light via exactly one facet of one of the two facet mirrors in each case. The facet mirror is a distance from a pupil plane of the illumination optical unit. Individual mirrors of the other facet mirror, which is arranged in, or in the vicinity of, a field plane that is conjugate to the object field, may be grouped into individual mirror groups which are tiltable together.