Chromatically Corrected Illumination Optics for High-Transmission Lithography
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Solution Overview
Problem
Existing chromatically corrected imaging illumination optical units in lithographic projection exposure apparatuses face challenges in achieving high throughput and illumination quality, with limitations in transmission efficiency and aberration correction.
Innovation Solution
The development of an illumination optical unit with a specific number of lens elements, primarily aspherical lenses, and a dioptric design, utilizing two or three different lens materials, such as flint and crown glass, to achieve an overall transmission of at least 85% and effective aberration correction, allowing for a compact structure and high magnification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional illumination optical unit is used, then the structure is simpler, but the throughput and illumination quality are insufficient
Solution Approach 1:
The illumination optical unit is divided into multiple lens elements (7-12 elements) arranged in specific groups. Each lens element is optimized for specific functions such as chromatic correction, field curvature control, and aberration reduction. This segmentation allows the system to achieve high throughput and illumination quality by distributing optical functions across multiple specialized components rather than relying on a single complex element.
Solution Approach 2:
The patent employs composite optical designs combining different lens materials with specific refractive indices and aberration characteristics. The lens elements are made from materials selected to optimize chromatic correction and transmission efficiency, creating a composite optical system that achieves superior performance in throughput and illumination quality compared to single-material designs.
2Manufacturing precision
If more lens elements are added to improve aberration correction, then the imaging quality improves, but the overall transmission decreases
Solution Approach 1:
The patent optimizes parameters such as lens element curvature, thickness, spacing, and material properties to achieve the desired balance between aberration correction and transmission efficiency. By carefully adjusting these parameters across the 7-12 lens elements, the system achieves high imaging precision while maintaining overall transmission of at least 85%, preventing excessive energy loss despite the increased number of optical interfaces.
3Manufacturing precision
If the number of lens elements is increased to at least seven, then aberration correction improves, but the device complexity increases
Solution Approach 1:
The optical system is segmented into 7-12 lens elements that are strategically arranged to perform specific correction functions. Each element is designed with optimized parameters to address specific aberrations, allowing the system to achieve high manufacturing precision through distributed correction rather than requiring a single complex element or excessive number of elements.
Solution Approach 2:
The lens elements are designed to serve multiple functions simultaneously - correcting various types of aberrations, controlling field curvature, optimizing transmission, and managing chromatic effects. This multi-functionality allows the system to achieve comprehensive error correction with a manageable number of elements (7-12), avoiding the need for even more complex designs.
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 enhances the throughput and illumination quality of the projection exposure apparatus by ensuring high transmission efficiency and effective aberration correction, enabling the production of structured components with improved precision.
Implementation Method 1
The illumination optical unit has at least seven and at most twelve lens elements in the imaging beam path
Implementation Method 2
At least three of the lens elements can be in the form of aspherical lens element. Such an aspherical form can allow for improved illumination quality.
Data Source
AI summary
A chromatically corrected imaging illumination optical unit serves for use in a lithographic projection exposure apparatus, for example for imaging, in a manner adapted to a downstream projection optical unit, an illumination conditioning field via an imaging beam path into an object field of the downstream projection optical unit. The illumination optical unit has at least seven and at most twelve lens elements in the imaging beam path. The illumination optical unit has an overall transmission for illumination light of at least 85%. Such an illumination optical unit can be used to improve a throughput of a projection exposure apparatus equipped therewith and achieve a high illumination quality.