EELS Spectrum Acquisition via Multi-Pass Beam Scanning
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Solution Overview
Problem
The existing methods for performing Electron Energy-Loss Spectroscopy (EELS) in charged particle microscopes are slow and cumbersome, relying on lengthy dwell times for data acquisition, which limits the speed and accuracy of spectral data collection and often requires offline post-processing.
Innovation Solution
A method that involves scanning a charged particle beam over a sample multiple times to acquire EELS spectra at multiple positions, combining the spectra to build up a full spectrum in real-time, allowing for shorter dwell times and providing immediate feedback, enabling quicker insights and more efficient data collection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a long dwell time is used at each sample position to acquire EELS spectra, then the spectral data quality and statistics are improved, but the total acquisition time increases significantly
Solution Approach 1:
The patent divides the EELS spectrum acquisition into multiple segments by scanning the beam over the sample multiple times (e.g., 5-10 passes). Each pass collects a portion of the spectral data at each position, and the segments are combined to form the complete spectrum. This segmentation allows shorter dwell times per pass while achieving the same total data quality as a single long dwell time
Solution Approach 2:
The patent performs preliminary scanning to identify regions of interest and plan the acquisition strategy before the actual EELS data collection. This preliminary action allows optimization of the scanning path and dwell times, ensuring efficient use of beam time while maintaining spectral quality
2Productivity
If the charged particle beam is scanned quickly over the sample to reduce acquisition time, then productivity is improved, but the spectral data quality and signal-to-noise ratio deteriorate
Solution Approach 1:
The patent maintains continuous scanning motion of the charged particle beam over the sample without stopping at each position. The beam continuously scans across all sample positions multiple times, collecting spectral data throughout the scan. This continuous action enables fast data collection while maintaining quality through the accumulation of data across multiple passes
Solution Approach 2:
The continuous scan is divided into multiple passes or segments, where each pass contributes a portion of the total spectral data. By combining data from multiple continuous scans, the system achieves both high productivity (continuous motion) and high precision (accumulated statistics)
3Measurement precision
If extensive post-processing and multiple linear least square fitting are performed on acquired spectra, then accurate extraction of material properties is achieved, but the processing time and computational complexity increase
Solution Approach 1:
The patent performs preliminary processing of the spectral data during or immediately after acquisition, including initial fitting and extraction of material properties. This preliminary action reduces the burden on offline post-processing and enables faster turnaround of results
Solution Approach 2:
The system implements feedback loops where the results from initial spectral analysis are used to guide subsequent scanning and acquisition strategies. This feedback enables real-time optimization of the measurement process, reducing the need for extensive offline processing
4Speed
If the beam dwell time at each position is reduced to enable real-time feedback, then the acquisition speed is improved, but the statistics and quality of individual spectra deteriorate
Solution Approach 1:
The patent segments the spectral acquisition into multiple passes, where each pass uses short dwell times for fast acquisition. The individual spectral segments from each pass are then combined through co-adding or averaging to achieve the statistical quality equivalent to much longer individual dwell times
Solution Approach 2:
The system performs periodic scanning passes over the sample, collecting spectral data at regular intervals. This periodic action allows accumulation of statistical data over time while maintaining fast acquisition speed through the use of multiple periodic cycles
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 approach allows for rapid and accurate acquisition of EELS spectral data, enabling real-time feedback and more informed sampling strategies, improving the throughput of applications such as semiconductor metrology and material science, while also enabling drift correction and reducing sample damage through low-dose scanning.
Implementation Method 1
Some of the electrons will undergo inelastic scattering, which means that they lose energy and have their paths slightly and randomly deflected. The amount of energy loss can be measured via an electron spectrometer and interpreted in terms of what caused the energy loss.
Implementation Method 2
The inner-shell ionizations are particularly useful for detecting the elemental components of a material. For example, one might find that a larger-than-expected number of electrons comes through the material with 285 eV less energy than they had when they entered the material. This is approximately the amount of energy needed to remove an inner-shell electron from a carbon atom
Data Source
AI summary
The invention relates to a method of examining a sample using a charged particle microscope, comprising the steps of providing a charged particle beam, as well as a sample; scanning said charged particle beam over said sample at a plurality of sample positions; and acquiring an EELS spectrum for each of said plurality of sample positions. According to the method, it comprises the further steps of scanning, once more, said charged particle beam over said sample at said plurality of sample positions; acquiring a further EELS spectrum for each of said plurality of sample positions; and combining, for each of said plurality of sample positions, said EELS spectrum with said further EELS spectrum. With this, it is possible to acquire rapid information on the sample being investigated, allowing for faster processing of samples.