EUV Imaging Optical Unit Folded Mirror Path
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Solution Overview
Problem
Current imaging optical units for EUV microlithography face challenges in achieving high EUV throughput while maintaining high imaging quality, often resulting in light losses and suboptimal spatial separation of the object and image fields.
Innovation Solution
The design incorporates a plurality of mirrors, including at least one mirror for grazing incidence, with a specific arrangement of mirror half spaces and a small angle of incidence, allowing for efficient EUV illumination and imaging light guidance with reduced light losses and improved spatial separation between the object and image fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional mirror arrangements are used in EUV imaging optical units, then the structure is simpler, but light losses increase and imaging quality deteriorates
Solution Approach 1:
The patent transitions from conventional planar mirror arrangements to a three-dimensional folded optical path configuration. By folding the beam path multiple times using mirrors positioned at different spatial locations and orientations, the system achieves superior light guidance and reduced losses while maintaining a compact footprint. This dimensional approach allows optimization of each mirror's position and angle independently, resolving the contradiction between complexity and performance.
Solution Approach 2:
The imaging optical unit is divided into multiple discrete mirror components (first mirror, second mirror, third mirror, fourth mirror) rather than using a single complex optical element. Each mirror segment performs a specific function in guiding the EUV light through the folded beam path, allowing individual optimization of each segment's position, orientation, and curvature to minimize light losses while managing overall system complexity.
2Manufacturing precision
If the angle between object plane mirror half space direction and image plane mirror half space direction is large, then spatial separation between object and image fields is improved, but imaging quality deteriorates
Solution Approach 1:
The patent resolves the spatial conflict by folding the optical path through multiple dimensions using a series of mirrors. Instead of simply increasing the angle between object and image planes, the system uses a folded beam path that traverses multiple spatial directions, effectively separating object and image fields in three-dimensional space while maintaining optimal imaging angles. This allows sufficient spatial separation for practical manufacturing while preserving high imaging quality.
3Productivity
If more mirrors are added to reduce light losses, then EUV throughput is improved, but device complexity increases
Solution Approach 1:
The patent achieves high EUV throughput by implementing a folded optical path that efficiently guides light through multiple reflections. The specific arrangement of four mirrors in a folded configuration optimizes the beam path to minimize losses at each reflection while maintaining a manageable system complexity. This dimensional approach allows the system to achieve superior throughput without linearly increasing complexity.
Solution Approach 2:
The patent optimizes specific parameters of each mirror including their positions, orientations, and curvature radii to minimize light losses. By carefully adjusting these parameters, the system achieves high EUV throughput with a fixed number of mirrors, avoiding the need to continuously add more mirrors as complexity increases. The parameter optimization includes setting specific angles and distances that maximize reflectivity and minimize absorption losses.
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 enables high throughput and high imaging quality by minimizing light losses and allowing for sufficient spatial separation of the object and image fields, facilitating the production of microstructured or nanostructured components with improved resolution and numerical aperture.
Implementation Method 1
a plurality of mirrors that image an object field in an object plane into an image field in an image plane. In so doing, the plurality of mirrors guides imaging light along an imaging light beam path
Implementation Method 2
At least one of the mirrors is embodied as a mirror for grazing incidence
Data Source
AI summary
An imaging optical unit for EUV microlithography is configured so that, when used in an optical system for EUV microlithography, relatively high EUV throughput and high imaging quality can achieved.