Scanning Electron Microscope Condenser Lens Field Separation
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Solution Overview
Problem
The existing scanning electron microscope configurations face challenges in efficiently detecting elastically scattered electrons with small emission angles due to spherical aberration and require cumbersome manual operations for aperture switching, while also being restricted by interference between focusing and deflecting fields, which limits the instrument's size and flexibility.
Innovation Solution
The design incorporates first and second condenser lenses with modified pole pieces to prevent overlapping focusing and deflecting fields, allowing for electromagnetic deflection of the electron beam and efficient detection of elastically scattered electrons through a scattering beam limiting aperture plate, enabling angular selection and reducing instrument size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the electron detector is disposed beside the optical axis to detect elastically scattered electrons, then the detection capability is improved, but the instrument size increases and field interference occurs
Solution Approach 1:
The electron detector is positioned on the optical axis rather than beside it, utilizing the longitudinal dimension of the electron optical system. This dimensional repositioning allows detection of elastically scattered electrons while maintaining a compact instrument structure and avoiding field interference that would occur with lateral placement.
Solution Approach 2:
The optical axis position, traditionally used only for direct electron transmission, is made multi-functional by placing the detector there. This allows the same spatial location to serve both as the primary beam path and as the detection position for scattered electrons, eliminating the need for separate lateral detection pathways.
2Ease of operation
If manual aperture switching is used to control probe current, then the operation is simple, but the operation complexity increases and efficiency decreases
Solution Approach 1:
The manual mechanical aperture switching system is replaced with an electromagnetic deflection system. Electromagnetic fields are used to deflect the electron beam onto different aperture positions, eliminating the need for mechanical movement and enabling rapid, automated aperture selection controlled by electrical signals.
Solution Approach 2:
The static manual aperture selection is transformed into a dynamic electromagnetic deflection system. The electron beam can be rapidly redirected to different apertures by varying the electromagnetic deflection parameters, enabling real-time adaptive control of probe current without mechanical intervention.
3Device complexity
If the focusing field and deflecting field overlap, then the instrument size is reduced, but field interference occurs and performance deteriorates
Solution Approach 1:
The electron optical system is segmented into distinct functional zones: the condenser lens region for focusing and the deflector region for beam steering. By spatially separating these functions along the optical axis, the patent prevents field overlap and interference while maintaining a compact overall structure.
Solution Approach 2:
The patent introduces an intermediate region between the condenser lens and deflector where the electron beam is prepared for deflection. This intermediate zone acts as a buffer that prevents direct interaction between the focusing and deflecting fields, eliminating interference while keeping the instrument compact.
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 efficient detection of elastically scattered electrons with small emission angles, preventing field interference and allowing for compact instrument design, while enabling precise control of the electron beam's angular aperture and reducing manual operation complexities.
Implementation Method 1
The first condenser lens 11 acts to vary the current value (probe current value) of the electron beam impinging on the specimen 14
Implementation Method 2
The second condenser lens 101 adjusts the orbit of the electron beam such that the electron optical system is optimized for the aberration in the objective lens 13
Implementation Method 3
An extraction voltage is applied to the extraction electrode 2. As a result, electrons are extracted from the emitter 1
Implementation Method 4
electrons are extracted from the emitter 1 and accelerated by an acceleration voltage applied to the acceleration electrodes 3
Data Source
AI summary
A scanning electron microscope has a first condenser lens (121) having a lens gap (121a) facing toward an electron source (50) and a second condenser lens (122) having a lens gap (122a) facing toward an objective lens (13). The first and second condenser lenses are disposed between the electron source (50) and the objective lens (13). First deflecting means (133) is disposed in a beam passage opening formed in the first condenser lens (121). Second deflecting means (136) is disposed in a beam passage opening formed in the second condenser lens (122). An aperture plate (113) having a plurality of apertures (113a) of different diameters is mounted between the first deflecting means (133) and the second deflecting means (136). An electron detector (102) having a beam passage aperture (102a) is mounted between the second deflecting means (136) and the objective lens (13).