Microlithography Imaging Optics with Through-Opening Mirrors
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Solution Overview
Problem
Current imaging optics systems face challenges in managing small imaging errors, production complexity, and light throughput, particularly in achieving a compact beam course and minimizing obscuration effects in the pupil plane, which affects the precision and efficiency of imaging processes.
Innovation Solution
The design incorporates at least six mirrors with a through-opening for imaging light, featuring a pupil plane with an obscuration stop for central shading, allowing for a compact beam course and free installation space, which enables a mechanically accessible pupil plane without shading other imaging part beams, thereby achieving small imaging errors and high throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact beam course is implemented in the region of the third and fourth mirror, then free installation space is provided in the beam path, but the complexity of arranging the pupil plane without shading other imaging part beams increases
Solution Approach 1:
The pupil plane is arranged in a different spatial dimension (transversely to the main beam path) rather than sequentially along the beam path. This allows the pupil plane to be positioned without interfering with the compact beam course of other imaging part beams, resolving the spatial conflict between compact beam routing and pupil plane placement.
Solution Approach 2:
A transmissive element is introduced as an intermediary component in the pupil plane to enable central shading while maintaining transmission of necessary imaging light. This mediator allows the obscuration stop to function without completely blocking the beam path, balancing the need for central shading with the requirement to maintain light throughput for other imaging part beams.
2Loss of energy
If an obscuration stop is arranged in the pupil plane for central shading, then imaging light losses are reduced, but the complexity of the imaging optics system increases
Solution Approach 1:
The obscuration stop is extracted as a separate, dedicated component positioned in the pupil plane, distinct from the main mirror assembly and other imaging components. This separation allows the central shading function to be implemented independently, reducing imaging light losses without requiring redesign of the entire imaging optics system.
Solution Approach 2:
The pupil plane structure is designed to serve multiple functions: it provides central shading through the obscuration stop, maintains the beam path for other imaging part beams, and allows for potential future additions such as wavefront sensors or other diagnostic equipment. This multi-functionality justifies the added complexity by providing long-term system versatility.
3Manufacturing precision
If at least six mirrors are used to achieve precise imaging, then imaging errors are reduced, but the device complexity and production difficulty increase
Solution Approach 1:
The imaging optics system is segmented into multiple discrete mirror elements (at least six mirrors) that can be individually fabricated, tested, and adjusted. This segmentation allows for precise control of each mirror's contribution to the overall imaging performance, enabling high imaging precision while facilitating modular production and assembly.
Solution Approach 2:
The mirror system incorporates adjustable elements that allow for dynamic alignment and correction of imaging errors during operation. This dynamic capability compensates for the complexity of having multiple mirrors by enabling real-time optimization of the imaging performance, maintaining high precision despite the increased number of components.
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 results in a compact and efficient imaging optics system with reduced imaging light losses, precise imaging parameters (e.g., wavefront error and distortion), and the ability to handle wide-band light sources, suitable for projection exposure installations in microlithography.
Implementation Method 1
imaging optics with at least six mirrors, which image an object field in an object plane into an image field in an image plane
Data Source
AI summary
An imaging optics has at least six mirrors, which image an object field in an object plane in an image field in an image plane. An entry pupil of the imaging optics is arranged in the imaging beam path in front of the object field. At least one of the mirrors has a through-opening for the passage of imaging light. A mechanically accessible pupil, in which an obscuration stop is arranged for the central shading of the pupil of the imaging optics, is located in a pupil plane in the imaging beam path between the object field and a first of the through-openings. A first imaging part beam directly after a second mirror in the imaging beam path after the object field and a second imaging part beam directly after a fourth mirror in the imaging beam path after the object field intersect one another in an intersection region. The result is an imaging optics, in which a handleable combination of small imaging errors, manageable production and a good throughput for the imaging light is achieved.