EUV Illumination System Optical Axis Inclination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
EUV illumination systems face conflicting requirements of minimizing reflective components to reduce reflection losses while achieving a compact design to efficiently illuminate object surfaces, particularly in micro-lithography for integrated circuit production, where the optical axis needs to be deflected significantly without excessive obstruction or reflection losses.
Innovation Solution
The illumination system achieves high EUV throughput and compact construction by inclining at least an axis portion of the optical axis between optical elements, allowing for minimal reflections with favorable angles of incidence, particularly using grazing or vertical incidence, and folding the optical axis in three spatial directions to minimize obstruction and enhance deflection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the number of reflective components is minimized to reduce reflection losses, then EUV throughput is improved, but the ability to deflect the optical axis by 90° becomes difficult to achieve
Solution Approach 1:
The patent introduces an inclination of the optical axis relative to the illumination main plane, adding a dimensional aspect to the optical path design. This allows the optical axis to be deflected through the arrangement and inclination of reflective components in three-dimensional space, achieving the required 90° deflection while maintaining a minimal number of components.
2Loss of energy
If the angle of incidence on reflective components is made very large (grazing incidence) or very small (vertical incidence), then reflection losses are minimized, but the optical system becomes more complex to achieve the required deflection
Solution Approach 1:
The patent optimizes the angle of incidence parameter for the reflective components, specifically designing for angles greater than 70° or less than 20° relative to the optical axis. This parameter optimization minimizes reflection losses while the inclination of the optical axis provides the necessary deflection capability without excessive system complexity.
3Length of stationary object
If the optical axis is folded in multiple directions to achieve compact construction, then the overall height is reduced, but the optical or mechanical design becomes more difficult
Solution Approach 1:
The patent employs folding of the optical axis in multiple directions, utilizing three-dimensional spatial arrangement to achieve compact construction. The inclination of the optical axis relative to the illumination main plane enables this folding approach, reducing the overall height to approximately 2.5 m or less while managing design complexity through systematic arrangement of reflective 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 approach results in a high EUV throughput, compact system design, and efficient production of integrated circuits with reduced reflection losses, enabling effective illumination of large object surfaces and faster production without excessive spatial demands, even with extended EUV sources.
Implementation Method 1
the angle of incidence on the reflecting components of the illumination system, i.e. on the reflecting optical elements after the collector and preferably on the EUV collector itself, should either be very large, i.e. in the region of grazing incidence, or very small, i.e. in the region of vertical incidence
Data Source
AI summary
An illumination system is used to illuminate a specified illumination field of an object surface with EUV radiation. The illumination system has an EUV source and a collector to concentrate the EUV radiation in the direction of an optical axis. A first optical element is provided to generate secondary light sources, and a second optical element is provided at the location of these secondary light sources, the second optical element being part of an optical device which includes further optical elements, and which images the first optical element into an image plane into the illumination field. Between the collector and the illumination field, a maximum of five reflecting optical elements are arranged. These optical elements reflect the main beam either grazingly or steeply. The optical axis, projected onto an illumination main plane, is deflected by more than 30° between a source axis portion and a field axis portion. In a first variant of the illumination system, at least an axis portion between at least two of the reflecting optical elements is inclined relative to the illumination main plane. In a second variant of the illumination system, the optical device, in addition to the second optical element includes precisely three further optical elements, i.e. a third optical element, a fourth optical element and a fifth optical element. In this second variant, the optical axis meets the third, fourth and fifth optical elements at an angle of incidence which is greater than 70°. This construction variants make possible either an increase of the EUV throughput of the illumination system for a given size, or a reduction of the size of the illumination system and thus of the associated projection exposure system for a given EUV throughput.