Multi-Beam SEM Beamlet Positioning With Overlap Scan Correction
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Solution Overview
Problem
Multi-beam scanning electron microscopes face challenges in accurately determining beamlet positions, leading to errors in stitched images due to displacements, which affect imaging throughput and quality.
Innovation Solution
A method involving two scans of overlapping sample regions by multiple beamlets to determine beamlet positions accurately, using cell images from both scans to correct displacements, and applying these positions to subsequent imaging sessions without additional sample damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If beamlet positions are determined using traditional single-scan methods, then the imaging process is faster, but the positioning accuracy decreases leading to stitching errors
Solution Approach 1:
The patent performs a preliminary first scan to establish initial beamlet positions and acquire reference cell images. This preliminary action creates a baseline for comparison that enables accurate position determination without requiring excessive scanning time during the actual imaging process. The first scan prepares the system in advance, allowing subsequent scans to focus on correction rather than complete reconstruction.
Solution Approach 2:
The patent implements a feedback mechanism by comparing cell images from overlapping regions between the first scan and second scan. The system uses the acquired images to calculate beamlet position displacements and feed this information back to correct positioning errors. This closed-loop feedback ensures high positioning accuracy while maintaining efficient imaging throughput through iterative refinement.
2Manufacturing precision
If the field of view is increased to reduce stitching errors, then image quality improves, but data acquisition time increases
Solution Approach 1:
The patent applies partial action by scanning only overlapping regions of the sample during the first and second scans, rather than scanning the entire field of view multiple times. This selective scanning approach provides sufficient information to determine beamlet positions and correct stitching errors without the time penalty of acquiring complete redundant images of the entire sample area.
Solution Approach 2:
The patent segments the imaging process into distinct phases: a first scan for initial positioning, a second scan for correction, and a final imaging phase using determined positions. By dividing the process into segments that focus on specific tasks (positioning vs. imaging), the system achieves high stitching accuracy without requiring the entire field of view to be scanned repeatedly, thus reducing total acquisition time.
3Reliability
If multiple scans are performed to determine beamlet positions, then positioning reliability improves, but the system throughput decreases
Solution Approach 1:
The patent merges the beamlet position determination process with the imaging process by using the same scanning mechanism and detectors for both purposes. The cell images acquired during the first and second scans serve dual functions: they are used for determining beamlet positions and will also be used for final image reconstruction. This merging eliminates the need for separate dedicated calibration scans, maintaining reliability while preserving throughput.
Solution Approach 2:
The scanning system is designed with multi-functionality, where the same beamlets and detectors used for imaging are also used for position determination. The overlapped region scanning serves multiple purposes: it provides reference data for position calculation, enables error correction, and contributes to the final image dataset. This universal use of system components ensures reliable positioning without sacrificing imaging productivity.
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 precise beamlet positioning, reducing stitching errors and increasing system throughput by minimizing the need for increased field of view and data acquisition time.
Implementation Method 1
each cell image is formed based on signals received responsive to irradiation from a corresponding beamlet of the multiple beamlets
Data Source
AI summary
Methods and systems to determine positions of multiple beamlets includes performing a first scan by scanning the beamlets over a first sample region and acquiring multiple cell images; and performing a second scan by scanning the beamlets over a second sample region and acquiring multiple cell images. Each cell image corresponds to a beamlet, and at least a part of an overlapped region between the first sample region and the second sample region is scanned by multiple beamlets during both the first scan and the second scan. Position of each beamlet may then be determined based on the corresponding cell images acquired during the first scan and the second scan.