Segmented Interferometry for Precise Optical Surface Measurement
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Solution Overview
Problem
Existing interferometric methods for measuring optical surfaces in lithography systems are time-consuming and inefficient due to partial region-based scanning, which hinders precise determination of surface shape.
Innovation Solution
A measurement apparatus and method that adaptively splits the optical surface into individual areas with adjustable subapertures, using a non-spherical wavefront and dynamic interferometer configuration to optimize measurement precision and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If partial region-based scanning is used to measure optical surfaces, then measurement precision can be maintained for each region, but measurement time increases significantly
Solution Approach 1:
The optical surface is divided into multiple individual measurement areas that can be measured separately. The interferometer device is positioned to measure different subapertures of the optical surface in sequence, allowing comprehensive surface measurement while managing measurement time through systematic segmentation of the measurement process
Solution Approach 2:
The interferometer device is made dynamically positionable relative to the optical surface using a positioning device with multiple degrees of freedom. This allows the system to adaptively adjust the measurement area and subaperture configuration in real-time, optimizing the measurement process by focusing on regions of interest and reducing unnecessary measurements
2Productivity
If the entire optical surface is measured at once, then measurement time is reduced, but measurement precision and spatial resolution deteriorate
Solution Approach 1:
The optical surface is segmented into multiple individual measurement areas with distinct subapertures. By measuring these segmented regions separately with optimized interferometer positioning, the system achieves high spatial resolution in each area while maintaining overall measurement efficiency through systematic coverage of the entire surface
Solution Approach 2:
Different regions of the optical surface are measured with locally optimized interferometer configurations. The positioning device adjusts the interferometer to capture the specific characteristics of each subaperture, ensuring high measurement precision and spatial resolution tailored to local surface features rather than applying a uniform measurement approach
3Device complexity
If fixed interferometer configuration is used, then device complexity is reduced, but adaptability to different measurement areas decreases
Solution Approach 1:
The interferometer device is equipped with a positioning mechanism that provides dynamic adjustability in multiple degrees of freedom. This allows the interferometer configuration to be adapted to different measurement areas and subapertures without requiring multiple fixed interferometer systems, achieving versatility through controlled movement rather than structural 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
Enables time-efficient and precise determination of optical surface shape with improved spatial resolution and reduced interference, facilitating high-precision processing and lithography.
Implementation Method 1
an interferometer device (7) having a splitting element (8) for splitting the illumination wave (6) into a test wave (9) directed at the surface (2) and a reference wave (10), and a registration device (11) for combining the returning test wave (9), which has interacted with the surface (2) to be measured, with the reference wave (10), for registering an interference pattern
Data Source
AI summary
A measurement apparatus (1) for measuring a shape of a surface (2) of a test object (3), in particular an optical surface (2) by interferometry, has:an illumination device (4) with an illumination source (5) for generating an illumination wave (6),an interferometer device (7) with a splitting element (8) for splitting the illumination wave into a test wave (9) directed at the surface (2) and into a reference wave (10), and for combining the returning test wave (9), having interacted with the surface to be measured, with the reference wave (10),a registration device (11) for registering and evaluating an interference pattern to determine a deviation of the measured surface shape from a target shape, anda control device (12) configured to split the surface (2) to be measured into a plurality of individual areas (13) to be measured.