Angularly Resolved Intensity Measurement in Projection Exposure
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Solution Overview
Problem
Current methods for measuring angularly resolved intensity distribution and beam divergence in projection exposure apparatuses for microlithography are time-consuming and require specialized sensors, especially in older systems without a sensor below the wafer plane, disrupting production and providing inaccurate measurements for optical proximity correction.
Innovation Solution
A method and system that measure angularly resolved intensity distribution in the reticle plane during operation by placing an optical module and detection module in the beam path, with the detection module positioned closer to the field plane than the pupil plane, allowing for precise measurement without the need for additional sensors below the wafer stage, and a divergence amplification module is used to accurately determine beam divergence by exchanging elements in the beam angle redistribution module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor is integrated below the wafer plane for pupilogram measurement, then measurement precision is improved, but device complexity increases and compatibility with older systems decreases
Solution Approach 1:
The patent introduces a beam splitter as an intermediary optical element that redirects a portion of the illumination beam to a sensor positioned in the reticle plane. This mediator enables the sensor to capture pupilogram information without requiring direct access to the pupil plane or integration below the wafer plane, thus maintaining measurement precision while reducing device complexity and improving compatibility with older systems.
Solution Approach 2:
The beam splitter creates an optical copy of the illumination beam path, directing a replicated portion of the light to the sensor. This copying mechanism allows the sensor to measure the angularly resolved intensity distribution without physically accessing the pupil plane, thereby achieving accurate measurements with simpler device architecture.
2Measurement precision
If a special measurement reticle with pinhole structures is loaded for pupilogram measurement, then measurement precision is improved, but productivity decreases due to production interruptions
Solution Approach 1:
The patent enables the illumination system to perform self-diagnosis and self-characterization by using the production reticle itself as the measurement target. The beam splitter redirects light from the production reticle to the sensor, allowing the system to automatically measure the angularly resolved intensity distribution during normal operation without requiring external measurement reticles or stopping production.
Solution Approach 2:
The measurement process occurs continuously during production operation rather than requiring separate measurement steps. The beam splitter enables simultaneous production and measurement functions, maintaining continuous useful action without interruptions for loading special reticles or performing dedicated measurement cycles.
3Measurement precision
If the detection module is positioned in the pupil plane for angularly resolved intensity distribution measurement, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The beam splitter serves as an intermediary that creates an alternative optical path from the illumination system to the sensor. Instead of positioning the sensor in the pupil plane, the beam splitter redirects light through a different path that ends at the reticle plane, achieving the same measurement objective with simpler positioning and reduced device 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 rapid, precise measurement of angularly resolved intensity distribution and beam divergence without production interruptions, improving the accuracy of optical proximity correction and compatibility with older systems.
Implementation Method 1
determining an angularly resolved intensity distribution of the radiated radiation from a signal recorded by the detection module
Implementation Method 2
arranging an optical module in the beam path of the projection exposure apparatus
Data Source
AI summary
A method for measuring an angularly resolved intensity distribution in a reticle plane (24) of a projection exposure apparatus (10). The apparatus includes an illumination system (16), irradiating a reticle (22) arranged in the reticle plane (24) and having a first pupil plane (20). All planes of the projection exposure apparatus which are conjugate thereto are further pupil planes, and the reticle plane (24) and all planes which are conjugate thereto are field planes. The method includes: arranging a spatially resolving detection module (44) in the region of one of the field planes (24, 30) such that the detection module is at a smaller distance from this field plane than from the closest pupil plane (20), radiating electromagnetic radiation (21) onto an optical module (42) from the illumination system, and determining an angularly resolved intensity distribution of the radiation from a signal recorded by the detection module.