Interferometer Zero-Position Determination via Dual Coherence Detection
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Solution Overview
Problem
Existing interferometer systems face challenges in accurately determining the zero-position, particularly in lithographic apparatuses where precise positioning is critical for manufacturing smaller features.
Innovation Solution
The proposed interferometer system includes a first and second detector configured to receive reference and measurement beams, with a reference and measurement variable delay path controlled by a delay path controller. This system generates reference and measurement spectral coherence pulses, allowing the control unit to determine the zero-position based on coherence signals and arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional interferometer system is used to determine the zero-position, then the system structure is simple, but the measurement precision for long-range positioning deteriorates
Solution Approach 1:
The interferometer system is divided into two separate detectors: a first detector for receiving reference beams and a second detector for receiving measurement beams. This segmentation allows independent optimization of reference and measurement paths, enabling precise zero-position determination while maintaining manageable system complexity through modular architecture
Solution Approach 2:
A delay path controller is introduced as an intermediary component to control variable delay paths in the reference beam. This mediator enables precise control of optical path differences, facilitating accurate zero-position determination through coherence signal analysis without requiring direct mechanical adjustment of the entire interferometer system
2Adaptability or versatility
If the measurement range is extended for long-range measurements, then the applicability improves, but the measurement precision deteriorates
Solution Approach 1:
The system employs variable delay paths that can be dynamically adjusted by the delay path controller. This dynamic capability allows the system to adapt the optical path difference for different measurement ranges while maintaining precise coherence signal detection, thereby extending measurement range without sacrificing precision
Solution Approach 2:
The system changes the delay length parameter in the reference beam path to match different measurement distances. By adjusting this parameter, the system can determine zero-positions at various ranges while maintaining measurement precision through optimal coherence signal detection at each range
3Productivity
If multiple coherence signals are measured simultaneously, then the measurement speed improves, but the device complexity increases
Solution Approach 1:
The measurement process is segmented into two independent detection channels: the first detector measures reference beam coherence and the second detector measures measurement beam coherence simultaneously. This segmentation enables parallel processing of reference and measurement signals, improving determination speed while keeping each detector's complexity manageable
Solution Approach 2:
Both detectors use the same coherence detection principle and can process their respective beams independently yet simultaneously. This universal approach allows the system to measure multiple coherence signals in parallel without requiring fundamentally different detection mechanisms, improving productivity with controlled 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
The system enables precise determination of the zero-position, facilitating long-range measurements and improving the accuracy of position control in lithographic processes, thereby supporting the advancement of semiconductor manufacturing in line with Moore's law.
Implementation Method 1
a reference spectral coherence pulse of the first reference beam and the first measurement beam occurs at the first detector, when the delay length corresponds to a reference coherence arrangement, and a measurement spectral coherence pulse of the second reference beam and the second measurement beam occurs at the second detector
Data Source
AI summary
Interferometer system including a first detector for receiving a first measurement beam travelling to a reference surface; a second detector for receiving a second measurement beam travelling to the target surface; a reference variable delay path and/or measurement variable delay path and a delay path controller for adapting a delay length. A reference spectral coherence pulse occurs at the first detector, at a reference coherence arrangement and a measurement spectral coherence pulse at the second detector at a measurement coherence arrangement. A control unit receives a reference coherence signal from the first detector, and a measurement coherence signal from the second detector, and determines a zero-position of the target surface based on the reference coherence signal and the measurement coherence signal, and based on the reference coherence arrangement and the measurement coherence arrangement and/or a delay path difference between the reference coherence arrangement and the measurement coherence arrangement.