Focusing Element Positioning for Secondary Electron Detection
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Solution Overview
Problem
The trajectory of electrons emitted from a specimen varies due to energy and charge status, leading to loss of secondary electron information when they collide with other structures before reaching the detector, resulting in decreased detection efficiency in scanning electron microscopes.
Innovation Solution
A charged corpuscular particle beam apparatus with a focusing element positioned to prevent its focusing action from affecting the beam traveling towards the specimen, allowing for selective control of electron trajectories to guide them into the detector, using a focusing electrode between the objective lens and secondary electron conversion electrode, and a Faraday cup to measure and feedback control the current, ensuring efficient detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a focusing element is placed to focus electrons emitted from the specimen, then detection efficiency of secondary electrons is improved, but the primary electron beam trajectory is affected causing positioning errors
Solution Approach 1:
The patent divides the electron optical system into separate functional zones: a first electron optical system for beam formation and scanning, and a second electron optical system for focusing and detecting secondary electrons. This segmentation allows independent optimization of each system without mutual interference, resolving the contradiction between detection efficiency and beam positioning accuracy.
Solution Approach 2:
The patent introduces an electron optical converter as an intermediary device that converts the primary electron beam into secondary electrons, which are then focused by the second electron optical system. This intermediary approach allows the focusing element to act on secondary electrons rather than the primary beam, improving detection efficiency without affecting beam positioning.
2Object-affected harmful factors
If accelerating voltage is lowered to reduce shrinkage and deformation of the specimen, then specimen damage is reduced, but resolution of the SEM decreases
Solution Approach 1:
The patent changes the energy parameter of electrons by introducing a boosting electrode that applies a negative potential, accelerating secondary electrons before they reach the detector. This allows the use of lower primary beam accelerating voltage (reducing specimen damage) while maintaining high detection efficiency through the energy boost of secondary electrons.
3Adaptability or versatility
If a detector is used to detect electrons traveling toward the outside of the detector, then detection coverage is improved, but detection efficiency decreases due to electron collisions with structures
Solution Approach 1:
The patent extracts the focusing function from the primary beam path and applies it only to secondary electrons in the detection region. The second electron optical system selectively focuses electrons in the detection area without affecting the primary beam, thereby improving detection coverage and efficiency simultaneously by removing the harmful focusing action from the beam path.
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 enhances the detection efficiency of charged corpuscular particles by controlling their trajectories, maintaining constant detection signals and preventing loss, thereby improving the signal-to-noise ratio and resolution in scanning electron microscopes.
Implementation Method 1
a focusing element which focuses the trajectories of charged corpuscular particles emitted from a specimen is arranged
Implementation Method 2
scans a spot beam focused on a specimen by using an electrostatic lens or a magnetic lens
Implementation Method 3
accelerates primary electron beams emitted from an electron source
Implementation Method 4
detects a secondary signal such as a secondary electron or a reflection electron generated as a secondary phenomenon from the specimen
Data Source
AI summary
According to a charged corpuscular particle beam irradiating method of this invention, a focusing element (19) which focuses the trajectories of charged corpuscular particles (12) emitted from a specimen (10) is arranged at a position which prevents focusing action by the focusing element (19) from affecting a charged corpuscular particle beam (4) traveling toward the specimen or can curb effects of the focusing action on the charged corpuscular particle beam (4). With this configuration, the focusing action selectively affects the charged corpuscular particles (12) emitted from the specimen (10), and effects of the focusing action on the charged corpuscular particle beam (4) traveling toward the specimen (10) are curbed. Thus, charged corpuscular particles emitted from the specimen (10) and traveling in a direction other than a direction toward a detector and the like can be focused and guided into the detector and the like, and a charged corpuscular particle beam irradiating method capable of efficiently detecting a charged corpuscular particle traveling in a direction other than the direction toward the detector and the like can be provided.