EUV Illumination Optical Unit Dynamic Mirror Assignment
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Solution Overview
Problem
Current illumination optical units for EUV projection lithography face challenges in optimizing the superimposition of illumination light from different channels without losses, particularly in adapting to the actual profile of the EUV light source and correcting illumination intensity and imaging effects across the object field.
Innovation Solution
The illumination optical unit employs a field facet mirror with switchable individual mirrors and a pupil facet mirror to create individual-mirror groups that can be assigned flexibly, allowing for partial or complete coverage of the object field, enabling the correction of illumination intensity and imaging effects without losses by utilizing a larger proportion of the far field area and adjusting the assignment of mirrors to optimize illumination parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed assignment of individual mirrors to pupil facets is used, then the device complexity is reduced, but the adaptability in defining illumination settings and correcting illumination intensity distribution deteriorates
Solution Approach 1:
The patent implements dynamic reconfigurability by allowing individual mirrors to be switched between different pupil facets during operation. The field facet mirror comprises multiple individually controllable mirrors that can be dynamically assigned to different pupil facets based on the required illumination setting, enabling adaptation without physical reconfiguration of the entire system.
Solution Approach 2:
The illumination system is segmented into multiple independently controllable individual mirrors on the field facet mirror, each assignable to different pupil facets. This segmentation allows flexible grouping of mirrors into individual-mirror groups that can be adapted to various illumination requirements while maintaining manageable system complexity through modular control.
2Use of energy by moving object
If edge regions of the far field are excluded from illumination, then imaging quality is improved, but the use of energy and illumination intensity deteriorate
Solution Approach 1:
The patent changes the illumination parameters by extending the illuminated area into the edge regions of the far field. By adjusting the assignment of individual mirrors to pupil facets, the system utilizes a larger proportion of the far field area, increasing energy use and illumination intensity while maintaining acceptable imaging quality through controlled inclusion of edge regions.
3Illumination intensity
If the number of pupil facets is increased to cover more individual mirrors, then the illumination intensity distribution is improved, but the device complexity increases
Solution Approach 1:
The patent implements multi-functionality by designing pupil facets that can serve multiple individual mirrors through dynamic assignment. Each pupil facet can receive light from different groups of individual mirrors at different times, allowing a smaller number of pupil facets to achieve comprehensive illumination intensity distribution improvement without proportionally increasing device complexity.
4Ease of operation
If individual mirrors are grouped into individual-mirror groups for pupil facet assignment, then the ease of operation is improved, but the manufacturing precision of illumination parameters deteriorates
Solution Approach 1:
The patent applies partial grouping by creating individual-mirror groups that can be selectively assigned to pupil facets. Not all mirrors need to be grouped simultaneously, and groups can be partially reconfigured based on requirements. This partial action approach maintains ease of operation through grouping while preserving precision by allowing selective exclusion or inclusion of specific mirrors in the groups.
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 solution allows for a more efficient use of the far field area, reducing edge region losses and enhancing the flexibility in defining illumination settings, thereby improving the structural resolution and integration density of micro- or nanostructured components, such as semiconductor chips, produced using the projection exposure apparatus.
Implementation Method 1
a field facet mirror (19) including a multiplicity of individual mirrors (27) which are switchable between at least two tilting positions and which provide individual-mirror illumination channels for guiding illumination light partial beams (16) toward the object field (5)
Implementation Method 2
the pupil facets in each case contribute to the at least sectionally superimposing imaging of a group of the individual mirrors (27) of the field facet mirror (19) into the object field (5) via a group-mirror illumination channel
Data Source
AI summary
An illumination optical unit for EUV projection lithography guides illumination light toward an object field. A field facet mirror of the illumination optical unit has a multiplicity of individual mirrors which are switchable between at least two tilting positions. A pupil facet mirror of the illumination optical unit has a plurality of stationary pupil facets and is disposed downstream of the field facet mirror in the beam path of the illumination light. The pupil facets serve for the at least sectionally superimposing imaging of a group of the individual mirrors of the field facet mirror into the object field via a group-mirror illumination channel.