EUV Illumination Optical Unit Polarization Control
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Solution Overview
Problem
In EUV microlithography, existing illumination optical units require additional polarization elements that absorb radiation, reducing transmission and increasing costs, making it difficult to achieve a desired polarization distribution for improved imaging contrast.
Innovation Solution
An illumination optical unit that uses a collector mirror to produce a polarization distribution applied to a faceted optical element, eliminating the need for additional polarization elements by adjusting the normal vectors of reflective surfaces to achieve a predetermined polarization distribution at the object field, allowing adaptation to different mask structures and enhancing imaging resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional polarization elements are used in the illumination optical unit to achieve a predetermined polarization distribution, then the imaging contrast is improved, but the total transmission of the illumination optical unit is reduced due to radiation absorption
Solution Approach 1:
The patent extracts the polarization function from separate polarization elements and integrates it into the faceted optical element itself. The faceted optical element is designed with specific facet orientations that inherently produce the desired polarization distribution without requiring additional polarization elements, thereby eliminating the absorption losses associated with those elements.
Solution Approach 2:
The patent merges the polarization control function with the existing faceted optical element. By designing the facets with specific normal vector orientations, the element simultaneously performs beam shaping and polarization control functions, eliminating the need for separate polarization elements and their associated transmission losses.
2Manufacturing precision
If additional polarization elements are used to achieve a predetermined polarization distribution, then the imaging contrast is improved, but the cost and complexity of the illumination optical unit increase
Solution Approach 1:
The patent extracts the polarization control function from separate polarization elements and integrates it into the faceted optical element itself. This reduces the number of optical elements in the system while maintaining the ability to achieve the desired polarization distribution for improved imaging contrast.
Solution Approach 2:
The faceted optical element is designed to perform multiple functions: beam shaping and polarization control. By integrating these functions into a single element, the patent reduces the overall number of components required in the illumination optical unit, thereby reducing complexity and cost.
3Manufacturing precision
If the polarization distribution is adapted to different mask structures, then the imaging resolution and contrast are enhanced, but the complexity of adjusting the illumination optical unit increases
Solution Approach 1:
The patent implements adjustability in the faceted optical element, allowing the normal vectors of the facets to be reconfigured for different mask structures. This dynamic adjustment capability enables optimization of polarization distribution for various imaging scenarios while maintaining a relatively simple overall system design.
Solution Approach 2:
The patent changes the orientation parameters (normal vectors) of the facet elements to adapt the polarization distribution to different mask structures. By adjusting these geometric parameters, the system can optimize imaging resolution and contrast for different applications without requiring complete reconfiguration of the optical unit.
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 allows for cost-effective and efficient production of the illumination optical unit with improved radiation transmission and high-resolution imaging by adapting the polarization distribution to match the structure-bearing mask, particularly enhancing contrast for structures perpendicular to the principal dipole axis.
Implementation Method 1
a collector mirror (5) which produces a polarization distribution that is applied to the first faceted optical element (7) during the operation of the illumination optical unit (3)
Implementation Method 2
the first faceted optical element (7) has at least one first state in which the normal vectors of the reflective surfaces of the first facet elements (9) are selected so that a first predetermined polarization distribution results at the location of the object field (21)
Data Source
AI summary
An illumination optical unit includes a collector mirror which produces a polarization distribution that is applied to the first faceted optical element during the operation of the illumination optical unit. There are at least two first facet elements to which radiation having a differing polarization is applied. The first faceted optical element has at least one first state in which the normal vectors of the reflective surfaces of the first facet elements are selected so that a first predetermined polarization distribution results at the location of the object field during the operation of the illumination optical unit.