Movable Reflective Elements for EUV Lithography Illumination Modes
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Solution Overview
Problem
Current lithographic apparatuses face challenges in achieving efficient EUV radiation intensity and forming desired illumination modes due to the absorption of EUV radiation by refractive materials and the need to block significant portions of the radiation beam with spatial filters, which reduces intensity and is not desirable.
Innovation Solution
An illumination system utilizing movable reflective elements that direct radiation towards different locations in the pupil plane, allowing for the formation of various illumination modes by adjusting the positions of end stops, enabling the creation of multiple illumination modes without blocking significant radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If spatial filters are used to form illumination modes, then the desired illumination pattern is achieved, but significant portions of the radiation beam are blocked which reduces radiation intensity
Solution Approach 1:
Instead of using spatial filters to block unwanted radiation paths, the invention inverts the approach by using reflective elements to actively direct radiation towards desired locations in the pupil plane. The illumination modes are formed by constructive redirection rather than destructive blocking, thereby maintaining high radiation intensity while achieving the required illumination patterns.
Solution Approach 2:
The invention replaces the traditional spatial filter mechanism (which absorbs or blocks radiation) with a reflective redirection mechanism. By using movable reflective elements to steer radiation, the system achieves illumination mode formation without the intensity loss inherent in filter-based approaches.
2Ease of operation
If refractive materials are used in EUV illumination systems, then radiation can be focused and shaped, but EUV radiation is absorbed by these materials reducing overall efficiency
Solution Approach 1:
The invention substitutes refractive optical elements with reflective elements for EUV radiation manipulation. The movable reflective elements achieve radiation focusing and shaping through reflection geometry rather than refraction, eliminating the absorption losses that occur when EUV radiation passes through refractive materials.
Solution Approach 2:
The invention changes the fundamental interaction parameter between the optical system and EUV radiation from refraction (which causes absorption) to reflection (which minimizes absorption). This parameter change enables efficient EUV radiation handling while maintaining the necessary focusing and shaping capabilities.
3Adaptability or versatility
If the number of reflective elements is increased to provide more illumination mode options, then versatility is improved, but device complexity increases
Solution Approach 1:
Each movable reflective element is designed to perform multiple functions: it can direct radiation to different locations in the pupil plane by changing its orientation, and can be positioned at different end stops to create various illumination modes. This multi-functionality allows a relatively small number of elements to provide diverse illumination mode options without proportionally increasing system complexity.
Solution Approach 2:
The invention introduces dynamic controllability to the reflective elements, allowing each element to be moved between different orientations and positions. This dynamic capability enables a single set of reflective elements to generate multiple illumination modes, providing versatility without requiring a large static array of fixed elements.
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 enhances the efficiency of EUV radiation use and allows for the formation of multiple illumination modes, improving the lithographic process by maintaining radiation intensity and flexibility in pattern projection.
Implementation Method 1
An illumination system is disclosed having a plurality of reflective elements, the reflective elements being movable between different orientations which direct radiation towards different locations in a pupil plane
Data Source
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AI summary
Provided is an illumination system of a lithographic apparatus, the illumination system having a plurality of reflective elements arranged to receive radiation from a radiation source, the reflective elements being movable between different orientations. In the different orientations the reflective elements direct radiation towards different locations at a reflective component in a pupil plane of the illumination system, thereby forming different illumination modes. Each reflective element is moveable between a first orientation which directs radiation towards a first location the pupil plane and a second orientation which directs radiation towards a second location in the pupil plane, the first orientation and the second orientation of the reflective element being defined by end stops.