Multi-Cell Charged-Particle Detector for Electron Beam Crosstalk
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Solution Overview
Problem
In multi-beam scanning electron microscopes, adjacent electron beams often overlap at the detector, causing crosstalk and noise in the output signals, which degrades the fidelity of image reconstruction due to the limited deflection directions provided by existing deflector arrays, especially when a large number of beams are used.
Innovation Solution
A multi-cell detector with a layered structure including a first conductivity type region, a second conductivity type region partitioned by third regions of the first conductivity type, and an intrinsic layer, which guides electrons to specific detection cells using applied biases to minimize crosstalk and enhance signal separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a deflector array is expanded to provide more deflection directions, then the ability to distinguish secondary electrons from different primary electron beams is improved, but the structural complexity of the deflector array increases and the difficulty of aligning the detector array with the electron sensing elements increases
Solution Approach 1:
The patent extracts the deflection function from the deflector array and transfers it to the detector structure itself. The detector includes a first deflection region and a second deflection region with different deflection directions, allowing each detector element to receive secondary electrons from specific primary electron beams without requiring complex external deflectors. This integration simplifies the overall system structure while maintaining the ability to distinguish electrons from different beams.
Solution Approach 2:
The patent introduces a new spatial dimension for electron detection by creating a three-dimensional detector structure with multiple layers and deflection regions. Instead of using a two-dimensional array of deflectors, the detector uses stacked layers with different deflection directions to spatially separate and identify secondary electrons from different primary beams, effectively adding a vertical dimension to the detection system.
2Device complexity
If adjacent electron beams are directed to reach substantially the same location of the detector surface, then the detector can be simplified, but beam spots from adjacent electron beams overlap leading to crosstalk and noise in output signals
Solution Approach 1:
The patent segments the detector into multiple independently controllable detector elements arranged in an array. Each detector element corresponds to a specific region where secondary electrons from a particular primary electron beam land. This segmentation allows the system to maintain a simplified overall detector structure while preventing crosstalk between adjacent beams through electrical isolation and independent signal processing of each detector element.
Solution Approach 2:
The patent applies different properties to different regions of the detector. Each detector element has tailored characteristics including specific deflection directions and sensitivity profiles optimized for receiving secondary electrons from its corresponding primary electron beam. This local optimization ensures high signal fidelity for each beam while maintaining overall system simplicity.
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
The solution effectively reduces crosstalk between adjacent detection cells, improving the accuracy and resolution of image reconstruction by ensuring that electrons from different beams are properly segregated, even with a large number of primary electron beams.
Implementation Method 1
a charged particle source configured to generate one or more beams of charged particles that are projected on a surface of a sample and that cause the sample to generate secondary charged particles
Implementation Method 2
which guides electrons to specific detection cells using applied biases to minimize crosstalk and enhance signal separation
Data Source
AI summary
A multi-cell detector may include a first layer having a region of a first conductivity type and a second layer including a plurality of regions of a second conductivity type. The second layer may also include one or more regions of the first conductivity type. The plurality of regions of the second conductivity type may be partitioned from one another, preferably by the one or more regions of the first conductivity type of the second layer. The plurality of regions of the second conductivity type may be spaced apart from one or more regions of the first conductivity type in the second layer. The detector may further include an intrinsic layer between the first and second layers.