Illumination Optical Unit with Individual-Mirror Array
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Solution Overview
Problem
Current illumination systems for projection lithography lack flexibility and adaptability to predetermined illumination values, limiting the precision and effectiveness of object field illumination.
Innovation Solution
An illumination optical unit comprising a collector, field facet mirror, pupil facet mirror, and an individual-mirror array that allows for tiltable individual mirrors, enabling flexible illumination by imaging intermediate focus into specific spatial regions, thereby achieving targeted reflection angles and polarization effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional illumination systems are used, then the structure is simple, but the flexibility and adaptability to predetermined illumination values are limited
Solution Approach 1:
The illumination system is divided into multiple independent facet mirrors (field facet mirror with field facets, pupil facet mirror with pupil facets) and an individual-mirror array. Each mirror can be independently controlled to reflect light at specific angles, enabling flexible adaptation to different illumination requirements while maintaining a modular structure that manages complexity through functional decomposition.
Solution Approach 2:
The individual mirrors in the individual-mirror array are made tiltable and can be adjusted individually to achieve different illumination geometries. This dynamic adjustability allows the system to adapt to predetermined illumination values and optimize imaging conditions, transforming a static system into a dynamically controllable one.
2Adaptability or versatility
If individual-mirror array is added upstream of field facet mirror, then new degrees of freedom are achieved for target reflection angles, but device complexity increases
Solution Approach 1:
The individual-mirror array serves multiple functions: it can be used to achieve specific target reflection angles at field facets and/or pupil facets, control polarization effects during reflection, and optimize illumination geometry for different imaging conditions. This multi-functionality justifies the added complexity by providing versatile control over illumination characteristics.
Solution Approach 2:
The system controls illumination by adjusting parameters such as reflection angles, polarization states, and illumination geometries through the tiltable individual mirrors. By changing these parameters dynamically, the system achieves diverse illumination patterns without adding permanent structural complexity, as the same mirror array can be reconfigured for different imaging tasks.
3Adaptability or versatility
If facets are arranged in non-continuous regions, then more degrees of freedom are available for illumination geometry, but manufacturing complexity increases
Solution Approach 1:
The facet mirrors are designed with non-continuous facet regions where individual facets are separated by interspaces. This segmentation allows each facet to be independently positioned and controlled, providing greater freedom for illumination geometry optimization. The modular nature of segmented facets can actually simplify manufacturing compared to continuous structures, as each segment can be produced and assembled independently.
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 provides enhanced flexibility and precision in object field illumination, allowing for optimized imaging and correction of intensity and angle distributions, improving the efficiency and homogeneity of illumination in projection exposure apparatuses.
Implementation Method 1
a collector for collecting the emission of a light source for the illumination light, wherein the collector is arranged such that it transfers the illumination light from the light source into an intermediate focus
Implementation Method 2
the individual-mirror array is arranged downstream of the intermediate focus in the illumination beam path, with a configuration in such a way that the intermediate focus is imaged via illumination channels, which are each formed by at least one of the individual mirrors
Implementation Method 3
comprising a field facet mirror having a plurality of field facets, comprising a pupil facet mirror having a plurality of pupil facets, wherein the field facets are imaged into the object field by a transfer optical unit
Implementation Method 4
wherein the field facets are imaged into the object field by a transfer optical unit
Data Source
AI summary
An illumination optical unit for projection lithography illuminates an object field with illumination light. The illumination optical unit has a collector for collecting the emission of a light source for the illumination light. The collector is arranged such that it transfers the illumination light from the light source into an intermediate focus. The illumination optical unit furthermore has a field facet mirror and a pupil facet mirror, each having a plurality of facets. The field facets are imaged into the object field by a transfer optical unit. The illumination optical unit additionally has an individual-mirror array having individual mirrors tiltable in a manner driven individually. The array is arranged upstream of the field facet mirror and downstream of the intermediate focus in an illumination beam path.