Beam Limiting Aperture for Sample Shielding in Helical Tomography

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Solution Overview

Problem

Transmission electron microscopes (TEMs) face challenges in obtaining multiple images of samples without causing damage due to limited electron beam doses, leading to sample alteration and noisy images, especially in electron beam tomography applications.

Innovation Solution

The method involves defining an irradiation zone with a beam limiting aperture and positioning a detector to receive radiation from a conjugate detector zone, allowing only specific portions of the sample to be exposed to the electron beam for imaging, while other portions are shielded, enabling reduced radiation exposure and multiple image acquisition with minimized damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If multiple images of a sample are acquired using low electron beam doses to minimize sample damage, then sample damage is reduced, but image quality deteriorates due to noisy images

Engineering Contradiction:

Improvesample damageVSAvoidimage quality

Core Design Contradiction:

Object-affected harmful factorsVSMeasurement precision

Solution Approach 1:

The sample is divided into multiple portions, with only the currently imaged portion exposed to the electron beam while other portions remain shielded. This segmentation allows the beam to concentrate on one region at a time, reducing overall sample damage while maintaining sufficient dose for high-quality imaging of each portion.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the sample receive different treatment: the active imaging region receives the electron beam at optimal dose for high-quality imaging, while other regions receive reduced or no exposure. This local differentiation allows high image quality in the imaged region without proportionally damaging the entire sample.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If multiple images are acquired with low electron beam doses, then sample damage is reduced, but the total imaging time increases

Engineering Contradiction:

Improvesample damageVSAvoidimaging time

Core Design Contradiction:

Object-affected harmful factorsVSLoss of time

Solution Approach 1:

While one sample portion is being imaged, other portions remain in position and ready for immediate imaging. The system maintains continuous operation by seamlessly transitioning between portions without requiring sample repositioning or beam reconfiguration, eliminating idle time and maintaining high productivity throughout the imaging process.

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

Multiple sample portions are pre-positioned in the field of view before imaging begins. This preliminary arrangement allows the imaging process to proceed continuously through different portions without time-consuming repositioning operations, reducing total imaging time while maintaining low dose per portion.

Inventive Principle:

Principle #10Preliminary action

3Loss of information

If the entire sample is exposed to the electron beam for multiple images, then complete sample coverage is achieved, but sample damage increases leading to alteration of the initial sample structure

Engineering Contradiction:

Improvesample coverageVSAvoidsample damage

Core Design Contradiction:

Loss of informationVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The electron beam is applied periodically to different sample portions in a systematic sequence rather than continuously to the entire sample. Each portion receives the beam at optimal intervals, ensuring complete coverage for information gathering while limiting cumulative exposure and damage through controlled periodic application.

Inventive Principle:

Principle #19Periodic action

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 approach allows for reduced sample damage and improved image quality by selectively exposing portions of the sample to the electron beam, enabling longer exposures and superior image acquisition in electron beam tomography and other charged-particle-beam imaging systems.

Implementation Method 1

defining an irradiation zone with a beam limiting aperture and situating a detector to receive radiation from a detector zone of the irradiation zone

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 2

the detector is operable to produce the images based on portions of the electron beam scattered, reflected, or transmitted by the sample

Methodology Applied

Scientific EffectScattering: Scattering

Data Source

PatentUS11430633B2Illumination apertures for extended sample lifetimes in helical tomography

Publication Date: 2022.08.30 FEI CO

AI summary

Apertures having references edges are situated to define a sample irradiation zone and a shielded zone. The sample irradiation zone includes a portion proximate the shielded zone that is conjugate to a detector. A sample is scanned into the sample irradiation zone from the shielded zone so that the sample can remain unexposed until situated properly with respect to the detector for imaging. Irradiation exposure of the sample is reduced, permitting superior imaging.