3D Detector Array for Multi-Beam Electron Column BSE Detection
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Solution Overview
Problem
Conventional multi-beam electron columns face challenges in detecting backscattered electrons (BSE) due to their large energy range, leading to cross-talk between beamlets and inefficient signal separation, which hampers defect inspection in applications like scanning electron microscopes.
Innovation Solution
The implementation of three-dimensional detectors positioned along the focal points of BSE of different energies within the electron optics system, allowing for the collection of BSE across a wide energy range while minimizing cross-talk through thin and strategically placed detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a detector normal to the BSE paths is used to collect BSE, then collection efficiency for a specific energy range is improved, but cross-talk with BSE from neighboring beamlets increases
Solution Approach 1:
The patent transitions from a two-dimensional detector plane to a three-dimensional detection volume by positioning multiple detectors at different distances from the sample along the BSE paths. This spatial distribution in the third dimension (depth) allows separation of BSE from different beamlets based on their focal points at different energies, reducing cross-talk while maintaining collection efficiency.
Solution Approach 2:
The detection system is divided into multiple independent detectors, each assigned to detect BSE from a specific beamlet. Each detector is positioned to receive BSE within a specific energy range that focuses at its location, creating segmented detection zones that prevent signal overlap and cross-talk between adjacent beamlets.
2Productivity
If the minimal distance between beamlets is reduced to increase throughput, then productivity is improved, but cross-talk between detected signals increases
Solution Approach 1:
By utilizing the depth dimension with detectors positioned at different distances from the sample, the system can resolve BSE from closely spaced beamlets that would otherwise overlap in a two-dimensional detection plane. This enables reduced beamlet spacing while maintaining signal separation through energy-dependent focal point discrimination along the optical axis.
Solution Approach 2:
The system exploits the energy parameter of BSE, which varies with scattering angle and beamlet position. By detecting BSE at different energies (which focus at different distances), the system can distinguish signals from adjacent beamlets even when their spatial separation is minimal, enabling higher throughput without sacrificing detection precision.
3Adaptability or versatility
If detectors are positioned to collect BSE across the entire energy range, then comprehensive BSE detection is achieved, but cross-talk with BSE from neighboring beamlets increases
Solution Approach 1:
The full BSE energy range is segmented across multiple detectors, with each detector responsible for a specific energy subrange. This segmentation allows comprehensive coverage of all BSE energies while each detector maintains selective sensitivity to its assigned energy range, preventing cross-talk through energy-filtered detection zones.
Solution Approach 2:
The array of detectors collectively provides universal detection capability across the entire BSE energy spectrum, while individually each detector maintains specialized function for its specific energy range. This multi-functional arrangement achieves both comprehensive energy coverage and selective signal isolation simultaneously.
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 enables efficient detection of BSE across a broad energy range, reducing cross-talk and enhancing the sensitivity and accuracy of defect inspection in multi-beam electron columns.
Implementation Method 1
BSE with different energies focus at different focal points—located at different distances from the sample
Data Source
AI summary
A method and a system for detecting backscattered electrons in a multi-beam electron column.