Split-Grid On-Axis Detector for Charged Particle Beam Systems
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Solution Overview
Problem
On-axis secondary particle detectors in charged particle beam systems suffer from low collection efficiency, particularly for high aspect ratio holes, due to secondary particles passing through the central hole and not being detected, which complicates endpointing in applications like circuit edit and reduces detector lifespan.
Innovation Solution
An electric or magnetic field is applied to alter the trajectory of secondary particles, ensuring they impact the detector rather than passing through the central hole, thereby increasing detection efficiency and extending detector life by distributing particle impact more evenly across the detector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an on-axis detector with a central hole is used to allow the primary beam to pass through, then the detector can be positioned on the beam axis for compact system design, but secondary particles pass through the hole and are not detected, resulting in low collection efficiency
Solution Approach 1:
The detector is divided into multiple independently biased segments or quadrants. By applying different voltages to each segment, electric fields are created that redirect secondary particles away from the central hole and toward the detector surface, improving collection efficiency while maintaining the on-axis configuration
Solution Approach 2:
The solution moves the detection problem from a two-dimensional plane (detector surface) to three-dimensional space by using electric fields to manipulate particle trajectories in the volume between the target and detector, redirecting particles along curved paths that avoid the central hole
2Productivity
If the detector collects all secondary particles uniformly, then detection efficiency is maximized, but the detector lifespan is reduced due to concentrated particle impact at specific locations
Solution Approach 1:
Different segments of the detector are independently biased to create localized electric fields that distribute particle impacts across different regions of the detector surface. This allows uniform collection efficiency while preventing concentration of damage at any single location, thereby extending detector lifespan
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 significantly enhances secondary particle collection efficiency to nearly 100%, especially at low beam currents, and extends detector lifespan by utilizing a split-grid MCP detector with independently biased segments to redirect secondary particles, improving endpoint detection and overall system performance.
Implementation Method 1
An electric or magnetic field is applied to alter the trajectory of secondary particles, ensuring they impact the detector rather than passing through the central hole
Data Source
AI summary
A split grid multi-channel secondary particle detector for a charged particle beam system includes a first grid segment and a second grid segment, each having independent bias voltages creating an electric field such that the on-axis secondary particles that are emitted from the target are directed to one of the grids. The bias voltages of the grids can be changed or reversed so that each grid can be used to detect the secondary particles and the multi-channel particle detector as a whole can extend its lifetime.