Imaging Optical System Wavefront Measurement by Segmented Modules
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Solution Overview
Problem
Existing methods for measuring complex imaging optical systems in microlithography, such as those used in EUV projection exposure systems, are inefficient as they require disassembly and cannot accurately attribute wavefront errors to individual optical elements, leading to time-consuming and inaccurate assessments.
Innovation Solution
A measuring arrangement and method that uses adaptation modules to form imaging optical arrangements with optical units, allowing separate measurement of individual optical modules within the system, using wavefront measuring devices and diffractive optical elements to accurately determine wavefront errors without disassembling the entire system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the imaging optical system is measured as a whole, then the wavefront error can be measured, but it is difficult to assign the measured aberrations to individual optical elements
Solution Approach 1:
The imaging optical system is divided into multiple optical modules, each containing one or more optical elements. The measurement process is segmented to measure each module separately while it is integrated into the complete optical system. This allows the wavefront error to be measured with precision while simultaneously assigning the aberrations to specific optical elements or modules, resolving the contradiction between measurement precision and information loss.
2Measurement precision
If individual optical elements are measured by disassembling the system, then the cause of wavefront error can be identified, but the process becomes increasingly time-consuming
Solution Approach 1:
The optical system is pre-configured with multiple optical modules that can be independently measured while remaining integrated into the complete system. This preliminary arrangement eliminates the need for disassembly before measurement. Each module can be measured in its designated position within the system, allowing rapid identification of wavefront errors without the time-consuming process of disassembly and reassembly.
3Ease of operation
If the imaging optical system is measured as a whole, then the measurement process is simple, but the complexity of the system makes it difficult to identify specific problematic elements
Solution Approach 1:
The system is segmented into multiple optical modules, each of which can be measured independently while maintaining integration into the complete optical system. This segmentation allows the measurement process to remain simple and straightforward, while simultaneously enabling the identification of specific problematic elements or modules that contribute to wavefront errors, thus resolving the contradiction between ease of operation and difficulty of detection.
4Measurement precision
If adaptation modules are used to form imaging optical arrangements, then individual optical modules can be measured separately, but the measurement arrangement becomes more complex
Solution Approach 1:
The adaptation modules are designed with multi-functionality, serving both as optical elements within the imaging system and as measurement tools. These modules can be used to measure different optical elements depending on their position and configuration in the system. This universality allows the measurement arrangement to maintain precision while reducing overall complexity, as the same modules serve dual purposes rather than requiring separate dedicated measurement components.
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
Enables precise and time-efficient determination of wavefront errors in individual optical modules, reducing the time required to identify and correct errors in complex imaging optical systems.
Implementation Method 1
Deviations from the desired shape can be determined by superimposing the test wave reflected by the optical element with a reference wave
Implementation Method 2
The wavefront of a test wave is adapted to a desired surface shape by a diffractive element, such as a computer-generated hologram (CGH)
Data Source
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AI summary
The invention relates to a method for measuring a wavefront error of an imaging optical system (10) of a projection lithography system for microlithography. The method consists of measuring separately respective wavefront errors of different sub-arrangements (M1; M2; M3; M1, M3) of the optical elements.