Moiré Grating Wavefront Measurement for Projection Lens Aberration Correction
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Solution Overview
Problem
Existing wavefront measuring devices in projection exposure apparatuses are time-consuming, leading to increased loss of throughput and reduced exposure efficiency, and are unable to rapidly identify and correct imaging aberrations in microlithography processes.
Innovation Solution
A projection exposure apparatus equipped with a Moiré grating arrangement that allows for simultaneous wavefront measurement at multiple field points, enabling accurate and efficient wavefront manipulation through a closed-loop controlled optical wavefront manipulator, which corrects aberrations in the projection lens to optimize imaging performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a wavefront measuring device is used in a projection exposure apparatus, then imaging aberrations can be measured and corrected, but the measurement process is time-consuming and causes loss of throughput
Solution Approach 1:
The wavefront measurement is divided into multiple discrete field points that can be measured independently and simultaneously. The projection lens is characterized at multiple object field points, and Moiré gratings are positioned at multiple image field points, allowing parallel measurement of wavefront aberrations across the entire field rather than sequential point-by-point measurement.
Solution Approach 2:
Multiple wavefront measurements at different field points are combined into a single integrated measurement process. The Moiré grating arrangement merges the measurement of multiple field points simultaneously, and the projection lens characteristics from all field points are combined to generate comprehensive correction data for the wavefront manipulator.
2Reliability
If conventional wavefront measurement methods are used, then imaging aberrations can be identified, but the correction process is slow and reduces exposure efficiency
Solution Approach 1:
The projection lens is pre-characterized at multiple field points during setup, storing wavefront aberration data for all field points in advance. This preliminary measurement and data storage eliminates the need for time-consuming repeated measurements during actual exposure operations, allowing rapid correction by simply retrieving and applying the pre-stored correction data.
Solution Approach 2:
A closed-loop feedback system is implemented where the wavefront manipulator applies corrections based on measured aberrations, and the Moiré grating arrangement continuously monitors the correction效果 at multiple field points. This real-time feedback enables rapid iterative optimization of wavefront correction without requiring time-consuming manual adjustments.
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 significantly reduces throughput loss and enables rapid correction of imaging aberrations, improving the efficiency and accuracy of wavefront manipulation, thereby enhancing the overall performance of the projection exposure apparatus in microlithography.
Implementation Method 1
The object grating and the image grating are coordinated with one another in a manner true to scale in such a way as to generate a Moiré superimposition pattern from an imaging of the object grating onto the image plane and the image grating
Data Source
AI summary
A projection exposure apparatus includes a projection lens, a wavefront manipulator and a wavefront measuring device for measuring a wavefront in the projection lens. The wavefront measuring device includes a Moiré grating arrangement having an object grating and an image grating which are designed to be arranged in an object plane and an image plane, respectively, of the projection lens. The object grating and the image grating are coordinated with one another in a manner true to scale in such a way as to generate a Moiré superimposition pattern from an imaging of the object grating onto the image plane and the image grating. The Moiré grating arrangement is designed in such a way as to simultaneously generate the Moiré superimposition pattern for a plurality of field points of an object field in the object plane and/or of an image field in the image plane.