Beam Apparatus Backscattered Electron Detection
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Solution Overview
Problem
Existing beam apparatuses face challenges in detecting secondary electrons and backscattered electrons separately and simultaneously due to the overlap of signals in the charged-particle detector, with difficulties in distinguishing between the two types of electrons, especially when the energies of backscattered electrons are low.
Innovation Solution
The apparatus incorporates a configuration with a condenser lens forming one crossover point between the electron source and the objective lens, along with a charged-particle detector positioned closer to the electron source and an aperture near the sample, allowing backscattered electrons to pass through while blocking secondary electrons, enabling efficient detection of low-energy backscattered electrons and simultaneous detection of both electron types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single charged-particle detector is used to detect both secondary electrons and backscattered electrons, then the detection capability is simplified, but the signals from the two types of electrons overlap and cannot be distinguished separately
Solution Approach 1:
The patent divides the detection function into two separate detectors: one dedicated to detecting secondary electrons and another dedicated to detecting backscattered electrons. This segmentation allows each detector to be optimized for its specific electron type, eliminating signal overlap and enabling separate detection of both electron types simultaneously.
Solution Approach 2:
The patent extracts the detection function for different electron types into separate detection paths. By placing detectors at different positions relative to the sample and beam path, the signal from each electron type is extracted separately, preventing mixing and enabling independent analysis of secondary electrons and backscattered electrons.
2Measurement precision
If the beam current is increased to improve signal intensity, then the detection sensitivity is improved, but the position of the virtual light source varies making angular aperture control inaccurate
Solution Approach 1:
The patent introduces a virtual light source position correction mechanism that acts as an intermediary between beam current control and angular aperture control. By monitoring and correcting for shifts in the virtual light source position, the system maintains accurate angular aperture control even when beam current varies, thereby preserving both detection sensitivity and control precision.
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 allows for the separate and simultaneous detection of secondary and backscattered electrons, improving image quality and compositional information of the sample by effectively isolating backscattered electron signals and enhancing detection efficiency.
Implementation Method 1
a condenser lens disposed between the electron source and the objective lens, with the condenser lens operated such that the primary beam forms one crossover point between the condenser lens and the objective lens
Implementation Method 2
an objective lens for focusing the primary beam produced from the beam source onto a sample
Implementation Method 3
A charged-particle detector is mounted at a position closer to the electron source than the crossover point. An aperture is disposed at the crossover point or at a position closer to the observed sample than the crossover point
Data Source
AI summary
A beam apparatus has a beam source producing a primary electron beam, an objective lens focusing the beam onto an observed sample, and at least one condenser lens mounted between the beam source and the objective lens. The condenser lens operates such that the beam forms one crossover point between the condenser lens and the objective lens. A first detector is mounted at the crossover point or at a position closer to the sample than the crossover point. A second detector is mounted at a position closer to the electron source than the crossover point.