In-Lens Sectional Detector for High-Resolution Side-View SEM Imaging
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Solution Overview
Problem
Conventional scanning electron microscopes with side-view imaging capabilities face challenges in achieving high resolution, especially for low landing energy imaging, due to poor aberration properties and the inability to collect secondary electrons effectively with strong axial magnetic and electrostatic fields.
Innovation Solution
An electron detector structure with an in-lens sectional detector and an ExB filter is used to capture secondary and backscattered electrons from the specimen surface at various angles, allowing for high-resolution side-view and plane-view imaging without interfering with the primary electron beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional side-detector is placed close to the specimen surface with a conical objective lens, then side-view imaging capability is achieved, but resolution deteriorates due to poor aberration properties
Solution Approach 1:
The detector is divided into multiple segments arranged in a circular pattern around the primary beam axis. Each segment detects electrons from specific angular ranges, allowing simultaneous collection of side-view and plane-view signals without requiring a conical lens modification.
Solution Approach 2:
The detector is positioned in a plane perpendicular to the primary beam axis rather than close to the specimen surface. This spatial reconfiguration allows electrons to be collected after passing through the objective lens, maintaining lens symmetry and aberration correction while enabling side-view imaging capability.
2Measurement precision
If an immersion magnetic lens and retarding electrostatic lens are combined to achieve low aberration and high resolution, then imaging resolution is improved, but side-view imaging capability deteriorates due to strong axial magnetic and electrostatic fields preventing side-detector operation
Solution Approach 1:
The detector is relocated from the specimen surface region to a plane downstream of the objective lens. This positional change places the detector in a region where the strong axial fields have diminished, allowing it to function with the immersion-RETarding lens combination intact, thus preserving both high resolution and side-view imaging capability.
Solution Approach 2:
The detector system can operate in multiple modes: detecting secondary electrons for side-view imaging and detecting backscattered electrons for plane-view imaging. This multi-functionality allows the system to achieve both high-resolution imaging and side-view capability with the compound lens configuration.
3Productivity
If a positive voltage is applied to the side-detector to attract secondary electrons and improve collection efficiency, then electron collection is improved, but device complexity increases due to additional voltage control requirements
Solution Approach 1:
The detector combines multiple detection functions into a single device structure. The same detector segments can collect both secondary electrons (with enhanced efficiency from the positive voltage) and backscattered electrons, eliminating the need for separate detection systems and reducing overall device complexity.
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 solution enables high-resolution imaging by guiding electrons through an aperture and ExB filter, improving collection efficiency and reducing aberration, thus resolving the conflict between high-resolution imaging and side-view imaging for low landing energy SEMs.
Implementation Method 1
an ExB filter is positioned to guide the secondary electrons and backscattered electrons emanating from specimen surface substantially toward the off-axis sectional detector
Implementation Method 2
a charged particle beam generator arranged to generate and control a charged particle beam substantially towards a portion of the specimen
Implementation Method 3
a detector arranged to detect charged particles emanating from the specimen to allow generation of an image of interested portion of the specimen
Data Source
AI summary
An electron beam apparatus and method are presented for collecting side-view and plane-view SEM imagery. The electron beam apparatus includes an electron source, some intermediate lenses if needed, an objective lens and an in-lens sectional detector. The electron source will provide an electron beam. The intermediate lenses focus the electron beam further. The objective lens is a combination of an immersion magnetic lens and a retarding electrostatic lens focuses the electron beam onto the specimen surface. The in-lens detector will be divided into two or more sections to collect secondary electrons emanating from the specimen with different azimuth and polar angle so that side-view SEM imagery can be obtained.