Coherent Point Microscopy for Scattering Matrix Characterization
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Solution Overview
Problem
Current optical metrology techniques are inadequate for measuring the diverse and independent physical properties of patterned structures, particularly critical dimensions, thickness, and optical properties of various layers, as they cannot fully access the entire set of scattering properties using a single method.
Innovation Solution
The development of Coherent Point Microscopy (CPM) technique, which measures the light intensity pattern related to the Fourier transform of the scattering matrix of a sample, utilizing critical illumination and coherent light sources to characterize both amplitude and phase, enabling comprehensive analysis of scattering properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical metrology techniques (reflectometry, ellipsometry, scatterometry) are used, then specific scattering properties can be measured, but the entire set of scattering properties cannot be accessed using a single technique
Solution Approach 1:
The patent combines multiple optical measurement capabilities into a single Coherent Point Microscopy system that can access the entire scattering matrix. By integrating coherent light illumination with point-by-point scanning and detector array imaging, the system merges reflectometry, scatterometry, and interferometry capabilities to simultaneously measure both amplitude and phase of scattered light across multiple directions and polarizations.
Solution Approach 2:
The CPM system is designed as a universal measurement platform that can characterize all scattering properties of a sample using a single technique. The system's ability to measure the complete scattering matrix (all elements Sij) makes it multi-functional, replacing the need for multiple specialized techniques while providing comprehensive structural information about the sample.
2Loss of information
If a point-like coherent light source is focused onto the sample in critical illumination, then coherent interference between different illumination angles is achieved, but the system complexity increases
Solution Approach 1:
The patent uses an imaging optical system as an intermediary between the coherent light source and the sample. The optical system includes lenses or mirrors that focus the coherent light into a diffraction-limited spot on the sample while maintaining the coherence required for interference measurements. This intermediary optical train enables phase information access without requiring direct contact between the light source and sample.
Solution Approach 2:
The system transitions from measuring only intensity (scalar) to measuring both amplitude and phase (complex quantity) by utilizing the spatial coherence dimension. By focusing coherent light and detecting the interference pattern in the image plane, the system accesses the phase dimension of the scattering matrix elements, providing complete complex scattering information.
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
CPM provides precise characterization of sample parameters, improving semiconductor manufacturing process control by offering a novel means to measure properties not easily accessible otherwise, enhancing measurement capabilities and reducing the need for multiple techniques.
Implementation Method 1
a light source system configured for producing an input beam of at least partially coherent light in spatial and temporal domains
Implementation Method 2
coherent interference between different illumination angles
Implementation Method 3
focusing the input light beam onto a diffraction limited spot on a sample's surface
Implementation Method 4
an optical system configured for focusing the input light beam onto a diffraction limited spot
Implementation Method 5
measuring a light intensity pattern from a sample related to the Fourier transform of the scattering matrix of a sample and thus containing information on both its amplitude and phase
Data Source
AI summary
Method and system for measuring one or more parameters of a patterned structure, using light source producing an input beam of at least partially coherent light in spatial and temporal domains, a detection system comprising a position sensitive detector for receiving light and generating measured data indicative thereof, an optical system configured for focusing the input light beam onto a diffraction limited spot on a sample's surface, collecting an output light returned from the illuminated spot, and imaging the collected output light onto a light sensitive surface of the position sensitive detector, where an image being indicative of coherent summation of output light portions propagating from the structure in different directions.