Low Loss Electron Detection for High Resolution Compositional Analysis
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Solution Overview
Problem
Current methods for compositional analysis in scanning electron microscopes, particularly for small objects, face challenges due to the low spatial resolution of backscattered electron and x-ray signals, which are affected by the size of the object and substrate, and are hindered by detector limitations such as variable conversion efficiency and gain drift.
Innovation Solution
The use of low loss electrons (LLEs) with energy filtering to obtain compositional information from a small interaction volume, combined with x-ray data from a larger volume, allows for higher spatial resolution analysis without needing correction tables for object size or substrate effects, using discrete counting to avoid detector variability issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional backscattered electron detection is used for compositional analysis, then atomic number information can be obtained, but spatial resolution is limited to about 1000nm due to electron scattering and penetration depth
Solution Approach 1:
The patent segments the backscattered electron signal into two distinct components based on energy loss: low loss electrons (LLEs) with minimal energy loss and conventional backscattered electrons with greater energy loss. This segmentation allows LLEs to provide high spatial resolution compositional information from shallow depths while conventional backscattered electrons provide atomic number information from deeper regions, resolving the spatial resolution limitation without sacrificing compositional analysis accuracy
Solution Approach 2:
The patent changes the detection parameter from total backscattered electron intensity to energy-filtered low loss electron intensity. By selecting electrons with minimal energy loss (LLEs), the interaction volume is reduced to approximately 100nm lateral range and 100nm depth, dramatically improving spatial resolution while maintaining the ability to determine effective atomic number through calibrated intensity measurements
2Measurement precision
If x-ray detection is used for compositional analysis, then elemental concentration information can be obtained, but spatial resolution deteriorates to about 3000nm due to deep electron penetration and extended x-ray generation volume
Solution Approach 1:
The patent merges two complementary detection techniques: low loss electron detection for high spatial resolution compositional analysis and x-ray detection for elemental concentration information. The LLE signal provides effective atomic number with 100nm spatial resolution while x-ray spectroscopy provides detailed elemental concentrations, creating a synergistic analytical approach that overcomes the spatial resolution limitation of conventional x-ray methods
Solution Approach 2:
The patent uses low loss electrons as an intermediary to bridge the gap between surface-sensitive secondary electron imaging and deep-penetrating x-ray analysis. LLEs interact with a shallow volume (100nm depth) providing high resolution compositional data that can guide and interpret the broader x-ray spectral information, effectively mediating between surface and bulk analysis
3Measurement precision
If total backscattered electron signal is used for analysis, then atomic number information is obtained, but the signal is affected by object size and substrate effects requiring correction tables
Solution Approach 1:
The patent extracts the low loss electron component from the total backscattered electron signal using energy filtering. By isolating LLEs with minimal energy loss, the signal becomes predominantly sensitive to effective atomic number with reduced sensitivity to object size and substrate effects, eliminating the need for complex correction tables while maintaining accurate atomic number determination
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 provides detailed compositional information with significantly improved spatial resolution, enabling analysis of objects smaller than 1000nm and overcoming limitations of conventional backscattered electron and x-ray techniques.
Implementation Method 1
Backscattered electrons are high-energy electrons which are back-scattered from the specimen as a result of its interaction with the beam
Implementation Method 2
x-rays are generated throughout the region reached by the electrons
Implementation Method 3
a low loss electron detector with an energy filter set to pass only electrons with an energy greater than 80% of the energy of the incident beam
Data Source
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AI summary
A method and apparatus for quantitative analysis of a material in which an electron beam is caused to impinge upon the material are described. The method comprises detecting low loss electrons (LLEs) received from a first region of the material due to interaction with the electron beam and generating corresponding LLE data. The method further comprises detecting x-rays received from a second region of the material due to interaction with the electron beam and generating corresponding x-ray data, wherein the first and second regions overlap, and analysing the LLE data together with the x-ray data so as to generate compositional data representative of the composition of the first region.