Adaptive SEM Dwell Time Control for Faster Low-Damage Imaging
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Solution Overview
Problem
Conventional scanning electron microscopes (SEMs) face inefficiencies in material analysis due to fixed dwell times, leading to prolonged acquisition times and potential sample damage from electron beams, especially for sensitive samples like biological specimens, and result in uneven exposure and image quality issues.
Innovation Solution
Adaptive dwell time techniques in SEMs that adjust dwell times based on detected particle counts, using variable staircase patterns and multiple detectors to optimize exposure duration per pixel, reducing unnecessary beam exposure and accelerating image acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fixed dwell times are used in conventional SEMs, then the scanning process is simple and reliable, but the acquisition time is prolonged and sample damage increases
Solution Approach 1:
The patent implements dynamic dwell time adjustment where the dwell time at each pixel location is varied based on detected particle counts. The system transitions from fixed dwell times to adaptive dwell times that are modified in real-time during scanning, allowing faster acquisition while maintaining image quality and reducing sample exposure time
Solution Approach 2:
The system uses feedback from particle detection to control dwell time adjustments. Detectors monitor particle counts at each location and provide feedback signals that trigger dwell time modifications, creating a closed-loop control system that optimizes scanning speed while preserving image quality
2Object-affected harmful factors
If fixed dwell times are used in conventional SEMs, then the control system is simple, but sample damage from electron beam exposure increases
Solution Approach 1:
The patent changes the dwell time parameter dynamically during the scanning process based on detected particle counts. By modifying this critical parameter in response to real-time detection data, the system reduces unnecessary electron beam exposure and minimizes sample damage while managing control complexity through automated algorithms
3Manufacturing precision
If fixed dwell times are used in conventional SEMs, then the scanning process is uniform, but image quality becomes uneven and acquisition time increases
Solution Approach 1:
The patent applies local quality optimization by adjusting dwell times at specific pixel locations based on detected particle counts. Rather than using a uniform dwell time across the entire image, the system tailors exposure duration to local characteristics, improving image quality uniformity while increasing scanning efficiency through targeted adjustments
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 significantly reduces sample damage and overall acquisition time while improving image quality by dynamically adjusting dwell times, ensuring uniform exposure and efficient use of electron beam, particularly beneficial for sensitive samples.
Implementation Method 1
A SEM is configured to scan the surface of the sample with a primary beam (e.g., an electron beam) and acquire an image of the sample based on various types of emissions
Implementation Method 2
Backscattered electrons (BSE) originate from the primary electron beam, which, as the name suggests, are reflected back (e.g., out of the sample) via elastic scattering on the sample atoms
Implementation Method 3
Along with the emissions of backscattered electrons, emissions of X-rays can also emerge from the interaction of the primary beam with the sample. In particular, characteristic X-rays are emitted when primary electrons cause the ejection of an electron in an inner shell of a sample atom
Data Source
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AI summary
A method for adaptive pixel dwell time usage in a microscope that includes scanning a beam (302) emitted by a beam source over a sample in a scan pattern such that the beam interacts with the sample (306) at a first scanning location according to the scan pattern. The method includes monitoring, by at least using a detector (320) of the microscope, a first cumulative number of particles (373) associated with the first scanning location of the sample such that the first cumulative number of particles correspond to an interaction of the beam with the sample at the first scanning location. The method further includes moving, after a first dwell time and before a first dwell period elapses, the beam to a second scanning location of the sample according to the scan pattern if a signal criterion is met such that the signal criterion is based on the first cumulative number of particles.