Reflective Imaging Optical System Aberration Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing reflective imaging optical systems for EUV lithography exposure apparatuses face challenges with aberration correction and overlay errors due to a short incident pupil distance, which affects the optical efficiency and resolution when using EUV light.
Innovation Solution
A reflective imaging optical system is designed with a specific condition of incident pupil distance, total optical axis length, and angle of incidence to ensure a large incident pupil distance and correct aberrations, allowing for high-resolution projection exposure with reduced overlay errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the incident pupil distance is increased to reduce overlay error, then the overlay error is reduced, but the aberration correction becomes difficult
Solution Approach 1:
The patent applies parameter changes by establishing a specific mathematical relationship between the incident pupil distance (PD), total optical axis length (TT), and angle of incidence (R). By controlling these parameters to satisfy the condition −14.3(PD/TT)/R ≤ −8.3, the system achieves both reduced overlay error and maintained aberration correction capability simultaneously
2Loss of energy
If the number of mirrors is reduced to enhance optical efficiency, then the optical efficiency is improved, but the aberration correction capability deteriorates
Solution Approach 1:
The reflective imaging optical system is designed to perform multiple functions simultaneously: it acts as both an imaging system and an aberration correction system. By optimizing the geometric parameters (PD, TT, and R), the system achieves aberration correction without requiring additional dedicated correction components, thus maintaining high optical efficiency
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
The solution enables high-resolution pattern transfer with reduced overlay errors and improved aberration correction, enhancing the optical efficiency and accuracy of EUV lithography processes.
Implementation Method 1
a reflective imaging optical system which forms, on a second plane, an image of an object arranged on a first plane
Data Source
AI summary
An imaging optical system of the far pupil type, which is applicable to an exposure apparatus, is provided with six reflecting mirrors and forms an image of a first plane on a second plane. An incident pupil of the imaging optical system is positioned on a side opposite to the imaging optical system with the first plane intervening therebetween. A condition of −14.3<(PD/TT)/R←8.3 is fulfilled by a distance PD which is provided along an optical axis between the incident pupil and the first plane, a distance TT which is provided along the optical axis between the first plane and the second plane, and an angle of incidence R (rad) of a main light beam which comes into the first plane.