Optical Rod Correction Area for Lithography Illumination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Illumination optical units for projection lithography face challenges in reducing unwanted field dependence of illumination angle distributions, especially when illumination angles deviate significantly from normal incidence, leading to imaging aberrations and non-uniform field illumination.
Innovation Solution
Incorporating a correction area with refractive effects at the exit area of the optical rod, described by asphere equations, to correct field-dependent illumination angle distributions, which can be designed with specific sagittal heights and structure gradients, and optionally integrated into a separate correction element or as part of the optical rod, allowing for flexible adaptation to different illumination settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional optical rod is used for illuminating the object field, then the structure is simple and easy to manufacture, but an unwanted field dependence of illumination angle distribution occurs, especially at extreme illumination angles
Solution Approach 1:
The patent applies local quality by introducing a correction area with specific refractive properties at the exit area of the optical rod. This correction area has a different optical function compared to the main rod body, with correction structures (aspheric surfaces) designed to locally compensate for field-dependent illumination angle deviations without redesigning the entire optical rod structure.
Solution Approach 2:
The correction structures in the correction area are described by asphere equations, utilizing curved surfaces to correct the illumination angle distribution. The aspheric curvature allows for precise control of light ray angles across the field, compensating for aberrations that occur at extreme illumination angles while maintaining manufacturing feasibility.
2Adaptability or versatility
If imaging aberrations occur at extreme illumination angles, then the illumination optical unit can cover a wider angular range, but field dependence of illumination angle distribution increases
Solution Approach 1:
The correction area is designed to preemptively counteract the field-dependent illumination angle deviations before they affect the object field illumination. By placing the correction area at the exit of the optical rod, the system pre-corrects the angular distribution of illumination rays, ensuring uniform illumination even at extreme angles without compromising the wide angular range capability.
3Manufacturing precision
If a separate correction element is added to correct field dependence, then illumination uniformity improves, but device complexity and number of optical elements increases
Solution Approach 1:
The patent merges the correction functionality directly into the optical rod structure by forming the correction area at the exit area of the rod. This integration eliminates the need for a separate correction element, reducing the total number of optical components while maintaining the field-dependent illumination correction capability. The correction structures are manufactured as part of the optical rod, simplifying alignment and reducing system complexity.
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 solution effectively reduces or eliminates unwanted field dependence of illumination angle distributions, compensating for imaging aberrations and ensuring uniform illumination even at extreme angles, thereby improving the quality of microstructured or nanostructured component production.
Implementation Method 1
The optical rod is designed in such a way that the illumination light is mixed and homogenized at lateral walls of the optical rod by multiple instances of total internal reflection
Implementation Method 2
The correction area can have a refractive effect
Data Source
AI summary
An illumination optical unit for projection lithography illuminates an object field. The illumination optical unit has an optical rod with an entrance area and an exit area for illumination light. The optical rod is configured so that the illumination light is mixed and homogenized at lateral walls of the optical rod by multiple in-stances of total internal reflection. At least one correction area serves to correct a field dependence of an illumination angle distribution when illuminating the object field. The correction area is disposed in the region of the exit area of the optical rod. This can result in an illumination optical unit, in which an unwanted field dependence of a specified illumination angle distribution is reduced or entirely avoided, even in the case of illumination angle distributions with illumination angles deviating extremely from a normal incidence on the object field.