EUV Illumination Optics Field Pupil Facet Correction
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Solution Overview
Problem
Current illumination optical units for EUV projection lithography lack flexibility in field-dependent correction of illumination parameters, leading to inefficient illumination distribution and reduced illumination light throughput.
Innovation Solution
The illumination optical unit employs a field facet mirror and a pupil facet mirror with correction actuators that allow for controlled displacement of field facets, enabling targeted trimming and distribution of illumination light across the object field, and a method to prescribe minimum illumination intensity over a transverse field coordinate, increasing light throughput by optimizing illumination channel alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If field-dependent correction of illumination parameters is implemented using correction field facets and correction pupil facets, then illumination distribution flexibility is improved, but device complexity increases due to additional actuators and control mechanisms
Solution Approach 1:
The illumination optical unit is divided into multiple discrete illumination channels, each with its own field facet and pupil facet. This segmentation allows independent control of each channel's illumination parameters, enabling flexible field-dependent correction without requiring complete system redesign. Each segment can be adjusted individually through its associated actuators.
Solution Approach 2:
The system employs dynamic actuators that can adjust the position and orientation of field facets and pupil facets in real-time. This dynamic capability allows the illumination distribution to be adaptively corrected based on measured field dependencies, transforming a static optical system into a dynamically adjustable one that can compensate for various illumination non-uniformities.
2Manufacturing precision
If correction field facets are displaced to trim illumination channels, then illumination parameter correction is improved, but illumination light throughput may be reduced due to partial beam cutoff
Solution Approach 1:
The system changes the parameters of illumination channels individually through controlled displacement of correction field facets. By adjusting parameters such as channel position, angle, and aperture, the system can correct illumination non-uniformities while optimizing light throughput. The parameter adjustments are designed to trim only the necessary portions of beams that contribute to field-dependent non-uniformities.
Solution Approach 2:
Different regions of the object field receive differently optimized illumination characteristics. The correction system applies local quality adjustments by selectively trimming specific illumination channels based on their contribution to field-dependent non-uniformities. This ensures that correction is applied precisely where needed without unnecessarily reducing overall light throughput.
3Area of stationary object
If multiple illumination channels are used to cover the object field, then field coverage is improved, but illumination uniformity deteriorates due to field-dependent variations
Solution Approach 1:
The system employs a feedback mechanism where illumination uniformity is measured across the object field, and the measured field dependencies are used to determine optimal correction settings. The control device processes measurement data and adjusts the correction field facets accordingly, creating a closed-loop system that continuously optimizes illumination uniformity while maintaining full field coverage.
Solution Approach 2:
The system changes parameters of individual illumination channels based on measured field dependencies. By adjusting parameters such as channel position, angle, and aperture for each illumination channel, the system compensates for field-dependent variations and achieves uniform illumination across the entire object field.
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 enables flexible field-dependent correction of illumination parameters and increased illumination light throughput by ensuring precise control over illumination distribution, enhancing the production of microstructured or nanostructured components with high structural resolution.
Implementation Method 1
Each of the field facets serves to transfer used illumination light from a light source to respectively one of the pupil facets
Implementation Method 2
For each illumination channel, the transfer optical unit respectively includes one of the pupil facets for transferring the illumination light partial beam from the field facet toward the object field
Data Source
AI summary
An illumination optical unit for EUV projection lithography includes a field facet mirror and a pupil facet mirror. A correction control device, which is used for the controlled displacement of at least some field facets that are usable as correction field facets, which are signal connected to displacement actuators, is embodied so that a correction displacement path for the correction field facets is so large that a respective correction illumination channel is cut off at the margin by the correction pupil facet so that the illumination light partial beam is not transferred in the entirety thereof from the correction pupil facet into the object field.