Variable Dose Electron Beam Scanning for STEM Tomography
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Solution Overview
Problem
Current scanning electron microscopy methods, such as STEM tomography, apply a uniform electron beam dose per scanning point, leading to high sample loading and time-consuming data generation, with low dose efficiency and resolution limitations due to high overall doses and repeated scanning at different angles.
Innovation Solution
Adapting the particle beam dose per scanning point during scanning, varying the dose to focus higher doses on areas of interest with contrasting imaging signals, while reducing doses in non-contrasting areas, and using pre-scanning and main-scanning phases with different electron beam intensities to optimize image quality and reduce overall dose.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a uniform electron beam dose is applied per scanning point during STEM tomography, then the sample is adequately irradiated for imaging, but the overall dose to the sample becomes excessively high and the imaging time becomes very long
Solution Approach 1:
The patent applies different electron beam doses to different regions of the sample based on their imaging importance. High-dose regions are targeted at areas with high contrast or boundaries that require detailed imaging, while low-dose regions are applied to areas with lower contrast or less imaging importance. This local differentiation resolves the contradiction by concentrating the necessary dose where it provides maximum imaging benefit while reducing the overall cumulative dose to the sample.
Solution Approach 2:
The patent dynamically adjusts the electron beam dose during the scanning process rather than applying a static uniform dose. The dose per scanning point is varied based on real-time assessment of signal contrast and imaging requirements. This dynamic adaptation allows the system to optimize the balance between achieving sufficient imaging resolution and minimizing the total dose accumulated across all scanning points throughout the tomography process.
2Quantity of substance
If the electron beam dose per scanning point is reduced to lower the overall dose, then the imaging time decreases, but the signal-to-noise ratio deteriorates and resolution is lost
Solution Approach 1:
The patent ensures sufficient signal-to-noise ratio by concentrating adequate electron beam dose on scanning points that contribute most to image quality, such as boundaries and high-contrast regions. By locally optimizing the dose distribution rather than uniformly reducing it, the patent maintains the necessary signal-to-noise ratio in critical areas while allowing the overall dose to be reduced through lower doses in less critical regions.
Solution Approach 2:
The patent dynamically determines the appropriate dose level for each scanning point based on its contribution to the overall image quality. Scanning points that provide critical imaging information receive higher doses to maintain signal-to-noise ratio, while less important points receive lower doses. This dynamic allocation ensures that the signal-to-noise ratio is preserved where it matters most while reducing the cumulative dose.
3Reliability
If the same electron beam dose is applied at each scanning point during repeated scanning at different inclination angles, then consistent imaging data is obtained, but the time required for data set generation becomes excessively long
Solution Approach 1:
The patent dynamically adjusts the electron beam dose for each scanning point based on previously acquired imaging data from earlier inclination angles. This allows the system to identify and prioritize scanning points that provide the most valuable new information at each inclination angle, rather than uniformly scanning all points. The dynamic dose adjustment maintains imaging consistency by ensuring adequate sampling of critical features while reducing redundant scanning, thereby significantly reducing the total data acquisition time.
Solution Approach 2:
The patent uses preliminary scanning data from previous inclination angles to inform and optimize the scanning strategy at subsequent angles. By analyzing the imaging quality and information content from earlier scans, the system can pre-identify which scanning points require attention at current inclination angles, allowing for more efficient dose allocation and reducing the time needed to acquire complete tomographic data sets while maintaining imaging consistency.
4Measurement precision
If a high electron beam dose is applied to improve the signal-to-noise ratio and resolution, then the imaging quality increases, but the sample loading and damage increase
Solution Approach 1:
The patent applies high electron beam doses only locally to specific scanning points where high signal-to-noise ratio is critical for imaging quality, such as boundaries and interfaces. In regions where lower contrast or less critical features are imaged, the patent uses lower doses. This spatially differentiated approach ensures that the necessary signal-to-noise ratio is achieved in critical areas while minimizing the cumulative sample loading and potential damage that would result from uniformly high dosing across the entire sample.
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 reduces the overall electron beam dose and time required for data set generation while enhancing image resolution and signal-to-noise ratio, particularly highlighting boundaries with high nuclear charge numbers, thereby improving imaging quality and efficiency.
Implementation Method 1
the sample is scanned in a point-wise manner by a focused beam of charged particles for generating imaging signals
Data Source
AI summary
The disclosed subject matter relates to testing a sample by means of a particle beam microscope in which the sample is scanned in a point-wise manner by a focused beam of charged particles thereby generating imaging signals. The particle beam dose applied per scanning point is changed during scanning.