Charged Particle Beam Detector Positioning for Resolution and Efficiency
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Solution Overview
Problem
Charged particle beam devices face challenges in maintaining high resolution and detection efficiency across a wide range of accelerating voltages, as magnetic saturation limits the magnetic field strength, causing issues with working distance and stray magnetic fields affecting electron detection.
Innovation Solution
A charged particle beam device with a movable detection surface that adjusts its position relative to the sample stage, allowing it to maintain constant distance from the sample surface regardless of working distance changes, and accommodates the detector between the objective lens magnetic paths to optimize electron detection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the working distance (WD) is shortened to achieve high resolution, then resolution is improved, but the detector cannot be positioned to detect reflected electrons effectively due to magnetic saturation and stray magnetic fields
Solution Approach 1:
The detector is designed to move between two positions: a first position for detecting reflected electrons when WD is long, and a second position for detecting emitted electrons when WD is short. This dynamic repositioning allows the system to adapt to different operating conditions and maintain both high resolution and detection efficiency
Solution Approach 2:
The system changes the position parameter of the detector based on the working distance setting. When WD is shortened for high resolution, the detector moves to the second position closer to the sample. When WD is extended, the detector moves to the first position to detect reflected electrons effectively
2Reliability
If the working distance (WD) is extended to overcome magnetic saturation at high accelerating voltage, then magnetic field limitations are addressed, but detection efficiency decreases due to increased distance between detector and sample
Solution Approach 1:
The detector position is dynamically adjusted based on WD settings. When operating at high accelerating voltage with extended WD, the detector moves to the first position optimized for detecting reflected electrons. When operating at low accelerating voltage with short WD, the detector moves to the second position closer to the sample
Solution Approach 2:
The system changes the detector's position parameter in response to changes in working distance and accelerating voltage, optimizing detection geometry for each operating condition
3Reliability
If a detector is introduced between the sample and objective lens to detect reflected electrons, then detection capability is improved, but the space required reduces the ability to maintain short working distance for high resolution
Solution Approach 1:
The detector is designed with movable capability to reposition between detecting reflected electrons (first position) and emitted electrons (second position). This dynamic positioning allows the detector to be placed in the path of reflected electrons when WD is long, and retracted or repositioned when WD is short, avoiding the need for permanent space occupation
Solution Approach 2:
The detection function is segmented into two modes: detecting reflected electrons at the first position and detecting emitted electrons at the second position. This segmentation allows the system to optimize for different detection needs without requiring the detector to occupy fixed space that would limit WD adjustment
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 configuration enables both high resolution at short working distances and improved detection efficiency at longer distances, effectively addressing the limitations of existing technologies by maintaining detection efficiency and resolution across varying accelerating voltages.
Implementation Method 1
an objective lens for converging a charged particle beam emitted from a charged particle source
Implementation Method 2
the magnetic field strength necessary for the convergence cannot be acquired due to the magnetic saturation of the lens magnetic path
Implementation Method 3
a detection surface for detecting charged particles emitted from the sample
Implementation Method 4
the reflected electrons emitted from the sample being inclined receive a rotation action by a stray magnetic field of the objective lens
Data Source
AI summary
The present disclosure is to provide a charged particle beam device capable of achieving both high resolution by setting of a short WD and improvement of detection efficiency when setting a long WD. According to an aspect for achieving the above-described object, there is suggested a charged particle beam device including: an objective lens for converging a charged particle beam emitted from a charged particle source; a sample stage having a first driving mechanism for moving a sample to be irradiated with the charged particle beam between a first position and a second position more separated from the objective lens than the first position; a detection surface for detecting charged particles emitted from the sample; and a second driving mechanism for moving the detection surface between within a movable range of the sample between the first position and the second position and out of the movable range of the sample.