Catoptric Illumination System Faceted Reflector Arc Field
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Solution Overview
Problem
Current catoptric illumination systems for microlithography face challenges in providing homogeneous illumination across an arc-shaped object field, leading to inefficiencies and aberrations in the imaging process.
Innovation Solution
The use of a faceted reflector, such as a field raster plate, with curve-shaped elements that are distorted relative to the object field, ensuring that the shape of their images at the object plane matches the object field, thereby achieving uniform illumination and correcting for projection effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional catoptric illumination systems use standard reflective elements, then the system structure is simple, but the illumination homogeneity across the arc-shaped field deteriorates
Solution Approach 1:
The illumination system divides the reflective field into multiple discrete facets or segments. Each facet is independently shaped and positioned to control the illumination angle and distribution. This segmentation allows precise control over the illumination homogeneity across the arc-shaped field while maintaining a manageable system structure through modular design.
Solution Approach 2:
Different regions of the reflective field are assigned different local properties through varying facet shapes, sizes, and orientations. Each facet is optimized for its specific position in the arc, creating locally tailored illumination characteristics that collectively achieve global homogeneity across the entire exposure field.
2Stability of the object's composition
If the field facet elements are distorted relative to the field shape, then projection effects are compensated and illumination homogeneity improves, but the element design complexity increases
Solution Approach 1:
The facet elements are pre-distorted during manufacturing to compensate for anticipated projection effects. By calculating the required distortion in advance based on the optical path and projection geometry, the elements are fabricated with predetermined non-uniform shapes that will produce uniform illumination when viewed through the projection lens, eliminating the need for post-manufacturing adjustment.
3Productivity
If curve-shaped field facet elements are used to illuminate arc-shaped fields, then the illumination efficiency improves, but the manufacturing precision requirements increase
Solution Approach 1:
The facet elements are designed with curved geometries that match the arc-shaped exposure field. These curved facets efficiently direct light along the arc trajectory, maximizing illumination coverage and intensity. The curvature profiles are optimized to maintain uniform intensity distribution while following the natural arc geometry, improving illumination efficiency without requiring excessive precision beyond the inherent curved design.
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 high transmission efficiency and uniform intensity distribution across the exposure field, enhancing the homogeneity of illumination and reducing aberrations, thus improving the overall performance of microlithography tools.
Implementation Method 1
Catoptric systems use exclusively reflective elements (e.g., mirror elements) to shape the radiation
Data Source
AI summary
In general, in one aspect, the invention features a system that includes an illumination system of a microlithography tool, the illumination system including a first component having a plurality of elements. During operation of the system, the elements direct radiation from a source along an optical path to an arc-shaped object field at an object plane of a projection objective, and at least one of the elements has a curved shape that is different from the arc-shape of the object field.