EUV Microscope Free Form Illumination Using Spherical Mirrors
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Solution Overview
Problem
Existing EUV microscope devices with free form illumination systems require expensive aspheric lenses, leading to increased costs and complexity, while also struggling with uniformity of illumination.
Innovation Solution
A high-performance EUV microscope with a free form illumination system using a spherical mirror and a plane mirror with a micro-mirror cell structure, allowing for two-axis angle scan and independent angle control of mirror cells to achieve uniform illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If aspheric lenses are used to achieve free form illumination, then illumination flexibility is improved, but cost and device complexity increase
Solution Approach 1:
The patent segments the optical system into multiple spherical mirrors instead of using a single complex aspheric lens. Each spherical mirror handles a specific portion of the illumination task, collectively achieving the free form illumination that would otherwise require a complex aspheric element. This segmentation reduces manufacturing difficulty and cost while maintaining functional flexibility.
Solution Approach 2:
The patent combines multiple spherical mirrors to achieve the functional equivalent of a single aspheric lens. By merging several simpler optical elements working together, the system attains the illumination flexibility of aspheric lenses without the associated cost and complexity penalties.
2Adaptability or versatility
If aspheric lenses are used to achieve free form illumination, then illumination flexibility is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive aspheric lenses with cheaper spherical mirrors that are easier and less costly to manufacture. Spherical mirrors can be produced using standard fabrication techniques, making them significantly more economical than precision aspheric lenses while still achieving the desired illumination flexibility through their arrangement and control.
Solution Approach 2:
By segmenting the illumination function across multiple inexpensive spherical mirrors rather than relying on a single expensive aspheric lens, the system achieves cost reduction while maintaining the required illumination flexibility.
3Device complexity
If conventional mirror systems are used for EUV measurement, then structural simplicity is maintained, but illumination uniformity deteriorates
Solution Approach 1:
The patent introduces dynamic control of the spherical mirrors through two-axis angle scanning. This dynamic adjustment capability allows the system to optimize illumination uniformity across the measurement target while maintaining the structural simplicity of using spherical mirrors rather than complex aspheric lenses.
Solution Approach 2:
The spherical mirrors serve multiple functions: they provide the necessary beam steering, focus adjustment, and illumination uniformity optimization. This multi-functionality allows the system to achieve good illumination uniformity without adding separate dedicated components, thus maintaining structural simplicity.
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
The solution enables cost reduction and structural simplification by eliminating the need for expensive aspheric lenses, while ensuring uniformity of illumination for precise EUV mask inspection.
Implementation Method 1
one spherical mirror which receives and reflects the EUV light outputted from the EUV light source and includes a two-axis drive part for controlling reflection direction of incident light through two-axis angle scan
Implementation Method 2
one plane mirror which receives the reflected light reflected from the spherical mirror and provides illumination light to a measurement target, in which a plurality of mirror cells are arranged at each angle
Implementation Method 3
a zone plate lens for focusing measurement light, which is the illumination light formed through the plane mirror and incident on the measurement target and then reflected
Implementation Method 4
a photodetector for receiving the measurement light focused by the zone plate lens
Data Source
AI summary
A high-performance EUV microscope with a free form illumination system, includes: an EUV light source that outputs EUV light; one spherical mirror, which receives and reflects the EUV light outputted from the EUV light source and includes a two-axis drive part for controlling reflection direction of incident light through two-axis angle scan; one plane mirror, which receives the reflected light reflected from the spherical mirror and provides illumination light to a measurement target, and in which a plurality of mirror cells are arranged at each angle; a zone plate lens for focusing measurement light, which is the illumination light formed through the plane mirror and incident on the measurement target and then reflected; and a photodetector for receiving the measurement light focused by the zone plate lens, wherein a reflection angle of the spherical mirror and a reflection angle of the plane mirror are selectively controlled, respectively.