SEM Electron Trajectory Adjustment for Low-Energy Spectroscopy
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Solution Overview
Problem
Current scanning electron microscopes face challenges in achieving high spatial resolution and secondary electron detection rates, particularly when primary electron energy is low, due to limitations in working distance and electromagnetic field interference.
Innovation Solution
The implementation of a scanning electron microscope system that includes an electron source, objective lens, primary electron acceleration and deceleration means, a secondary electron deflector, spectroscope, and detectors, with a controller to optimize voltage settings for the objective lens and electron acceleration/deceleration means to converge secondary electrons effectively into the spectroscope, enhancing spatial resolution and detection rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a spectroscope is installed between the objective lens and the sample, then secondary electron energy spectroscopy can be performed, but the working distance cannot be shortened and spatial resolution is degraded
Solution Approach 1:
The spectroscope is positioned above the objective lens rather than between the lens and sample, changing the spatial dimension of installation. This allows the working distance to be shortened while maintaining spectroscopy capability through a different geometric arrangement
Solution Approach 2:
The electron optical path is segmented into separate regions: primary electron acceleration above the lens, secondary electron extraction at the sample, and spectroscopy detection above the lens. This segmentation allows independent optimization of each function without mutual interference
2Ease of operation
If the working distance is shortened and secondary electrons are dispersed with the electromagnetic field of the objective lens, then the structure is more compact, but the detection rate of secondary electrons is degraded
Solution Approach 1:
A dedicated secondary electron extraction electrode is introduced as an intermediary component between the objective lens and the spectroscope. This electrode actively extracts and guides secondary electrons, mediating between the lens electromagnetic field and the spectroscope to maintain high detection rates despite short working distance
Solution Approach 2:
The electric field parameters (voltage, field distribution) are optimized in the region between the objective lens and sample to enhance secondary electron extraction efficiency. By changing field parameters rather than geometric parameters, high detection rate is maintained with short working distance
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 high spatial resolution and improved secondary electron detection rates, even at low primary electron energies, by controlling the convergence of electrons through voltage settings, thereby optimizing signal/noise ratios and convergence conditions.
Implementation Method 1
an objective lens that converges primary electrons emitted from the electron source on a sample
Implementation Method 2
primary electron acceleration means that accelerates the primary electrons and passes them through the objective lens
Implementation Method 3
primary electron deceleration means that decelerates the primary electrons and irradiates them to the sample
Implementation Method 4
a secondary electron deflector that deflects secondary electrons from the sample, caused from the primary electrons converged with the objective lens, to the outside of an optical axis of the primary electrons
Implementation Method 5
a spectroscope for dispersion of the secondary electrons
Implementation Method 6
a controller that controls application voltage to at least one of the objective lens, the primary electron acceleration means and the primary electron deceleration means so as to converge the secondary electrons to an entrance of the spectroscope
Data Source
AI summary
To provide a scanning electron microscope having an electron spectroscopy system to attain high spatial resolution and a high secondary electron detection rate under the condition that energy of primary electrons is low, the scanning electron microscope includes: an objective lens 105; primary electron acceleration means 104 that accelerates primary electrons 102; primary electron deceleration means 109 that decelerates the primary electrons and irradiates them to a sample 106; a secondary electron deflector 103 that deflects secondary electrons 110 from the sample to the outside of an optical axis of the primary electrons; a spectroscope 111 that disperses secondary electrons; and a controller that controls application voltage to the objective lens, the primary electron acceleration means and the primary electron deceleration means so as to converge the secondary electrons to an entrance of the spectroscope.