Optical Phase Measurement via Self-Interferometry
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Solution Overview
Problem
Existing optical metrology methods for measuring phase shifts on patterned structures are delicate, require special apparatus, and are sensitive to environmental vibrations, making them unsuitable for in-line measurements, while failing to capture valuable spectral phase information.
Innovation Solution
A self-interferometry method that detects interference patterns from different regions of a structure illuminated with single or multiple wavelengths, allowing for robust and accurate phase measurements, including spectral phase, without the need for an internal reference beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional interferometry methods are used to measure phase, then measurement precision is improved, but device complexity and sensitivity to environmental vibrations increase
Solution Approach 1:
The patent extracts and eliminates the reference beam component from the interferometric measurement system. By using only the sample beam that reflects from different regions of the structure, the method removes the need for complex reference beam generation and stabilization apparatus, while still enabling phase measurement through spatial interference patterns formed by light reflecting from different structural regions
Solution Approach 2:
The measurement system uses the sample structure itself to generate the interference pattern. Different regions of the patterned structure (e.g., patterned and unpatterned regions) act as the two interfering sources, eliminating the need for external reference beams or additional interferometric components. The structure's own optical response provides the measurement signal
2Measurement precision
If conventional interferometry methods are used to measure phase, then measurement precision is improved, but reliability in vibration environments deteriorates
Solution Approach 1:
The patent removes the reference beam path from the measurement system, eliminating the long optical paths that are highly sensitive to vibrations. By confining the measurement to light reflecting from different regions within the sample structure itself, the method reduces the measurement path length and eliminates sensitivity to environmental vibrations while preserving phase measurement capability
Solution Approach 2:
The system uses the sample structure's own reflected light from different regions as the interfering sources. This self-contained approach eliminates the need for external reference beams that would require long, vibration-sensitive optical paths, making the measurement inherently more reliable in practical environments
3Reliability
If reflectometry and ellipsometry methods are used, then robustness to vibrations is improved, but phase measurement capability is lost
Solution Approach 1:
The patent merges the robustness of reflectometry with the phase measurement capability of interferometry. By detecting interference patterns formed by reflected light from different regions of the structure using a simple reflectometric setup without reference beams, the method achieves both vibration robustness and phase sensitivity, capturing spectral phase information that was previously accessible only through delicate interferometric methods
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 robust phase measurements, providing valuable information for optical characterization and OCD metrology, while being insensitive to system vibrations and apparatus sensitivity issues.
Implementation Method 1
the detected light comprising interference of at least two complex electric fields reflected from said at least part of the at least two different regions
Data Source
AI summary
A method for use in optical measurements on patterned structures, the method including performing a number of optical measurements on a structure with a measurement spot configured to provide detection of light reflected from an illuminating spot at least partially covering at least two different regions of the structure, the measurements including detecting light reflected from the at least part of the at least two different regions within the measurement spot, the detected light including interference of at least two complex electric fields reflected from the at least part of the at least two different regions, and being therefore indicative of a phase response of the structure, carrying information about properties of the structure.