Electron Beam Angle Modulation for Crystalline Defect Imaging
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Solution Overview
Problem
Current electron channeling contrast imaging techniques are inefficient for characterizing lowly defective materials due to lengthy measurement times required for analyzing large areas, which hampers their application as a routine analysis tool.
Innovation Solution
A method and system that modulate the instantaneous relative angle between the electron beam and the sample using a predetermined frequency, allowing for enhanced sensitivity and reduced measurement time by distinguishing signal contributions from regions with and without crystalline defects, enabling fast and nondestructive imaging of defect distributions and densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a focused electron beam is scanned across the sample surface to image crystalline defects, then single extended crystalline defects can be resolved, but the overall measurement time increases to several hours for lowly defective samples
Solution Approach 1:
The patent applies periodic modulation of the electron beam angle at a predetermined frequency to selectively enhance the backscattered signal from regions with crystalline defects. By modulating the beam angle and detecting the modulated signal, the system can distinguish defect regions from background crystalline regions, enabling faster acquisition of statistically relevant defect density information without requiring exhaustive scanning of large areas.
2Measurement precision
If a large area is analyzed by scanning the focused electron beam to derive statistically relevant defect density information, then accurate defect characterization is achieved, but the measurement time adds up to several hours
Solution Approach 1:
The periodic modulation of the electron beam angle enables selective signal enhancement from defect regions. By using lock-in detection at the modulation frequency, the system can extract defect-related signal contributions from the total backscattered electron signal, allowing accurate defect density characterization to be obtained from smaller scanned areas or with fewer pixels, thereby significantly reducing measurement time while maintaining statistical relevance.
3Productivity
If the electron beam intensity is increased to reduce measurement time, then faster characterization is achieved, but the signal from background regions increases reducing signal-to-noise ratio
Solution Approach 1:
By modulating the electron beam angle at a predetermined frequency and detecting the modulated backscattered signal, the system can selectively amplify the contribution from defect regions while suppressing the background signal. The lock-in detection technique extracts only the signal component at the modulation frequency, effectively filtering out background contributions and maintaining high signal-to-noise ratio even with higher beam intensities or faster scanning rates.
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 results in a good signal-to-noise ratio, reduced measurement time, and the ability to perform wafer-scale metrology with acceptable throughput, allowing for accurate characterization of crystalline defects and confined structures within non-crystalline matrices.
Implementation Method 1
The intensity of backscattered or forward scattered electrons depends on the lattice parameter as well as on the orientation of the lattice planes, with respect to the incident electron beam
Implementation Method 2
Crystalline defects cause a local deformation (extending over a few nm) of the lattice planes which leads to a local variation of the backscattered intensity
Data Source
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AI summary
A method (200) for characterizing a region in a sample under study is described. The sample under study comprising a first region having first crystalline properties and a second region having second crystalline properties. The method (200) comprises irradiating (210) the sample under study with an electron beam, the average relative angle between the electron beam and the sample under study being selected so that a contribution in the backscattered or forward scattered signal of the first region is distinguishable from that of the second region, detecting (220) the backscattered or forward scattered electrons, and deriving (230) a characteristic of the first and/or the second region from the detected backscattered or forward scattered electrons. The instantaneous relative angle α between the electron beam and the sample under study is modulated with a predetermined modulation frequency during said irradiating (210) and detecting (220) is performed at the predetermined modulation frequency.