Adaptive Charged Particle Beam Scanning for Mixed Electron Yield Regions
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Solution Overview
Problem
Scanning electron microscopes face challenges in obtaining high-quality images of areas with high and low electron yield regions due to varying electron yields and signal-to-noise ratios, requiring adaptive scanning strategies to optimize image acquisition.
Innovation Solution
A system and method utilizing charged particle optics to scan regions of interest at different rates based on electron yield, signal-to-noise ratio, and priority, with the processor generating images by detecting particles from these scans, allowing for adaptive scan patterns and segment definitions to enhance image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the SEM scans the entire area at a very low scan rate to obtain high-quality images of low electron yield regions, then the image quality of low electron yield regions is improved, but the productivity decreases
Solution Approach 1:
The inspection area is divided into multiple regions of interest (ROIs) based on electron yield characteristics. High electron yield regions and low electron yield regions are segmented separately, allowing different scan rates to be applied to each segment. This resolves the contradiction by enabling fast scanning of high electron yield areas while maintaining slow scanning for low electron yield areas, thus improving overall productivity without sacrificing image quality in critical regions.
Solution Approach 2:
Different scan rates are applied to different regions based on their local electron yield properties. High electron yield regions are scanned at higher scan rates, while low electron yield regions are scanned at lower scan rates. This local differentiation resolves the contradiction by optimizing the scan rate for each specific region's characteristics rather than using a uniform scan rate across the entire area.
2Measurement precision
If the SEM scans low electron yield regions at a low scan rate, then the signal to noise ratio is improved, but the scanning time increases
Solution Approach 1:
The area is segmented into high electron yield regions and low electron yield regions. By identifying and separating low electron yield regions, the system can apply extended scanning time only to these specific segments rather than the entire area. This resolves the contradiction by concentrating the time investment where it is most needed for improving signal to noise ratio.
Solution Approach 2:
The scan rate is dynamically adjusted based on the electron yield characteristics of each region. Low electron yield regions are scanned at lower rates to improve signal to noise ratio, while high electron yield regions are scanned at higher rates to reduce scanning time. This dynamic adaptation resolves the contradiction by making scan rate flexible rather than fixed.
3Measurement precision
If multiple images are acquired and averaged to improve image quality, then the measurement precision is improved, but the duration of action increases
Solution Approach 1:
The acquisition process is segmented into multiple passes, with different regions receiving different numbers of scans. Low electron yield regions are scanned multiple times and averaged to improve image quality, while high electron yield regions require fewer scans. This segmented approach resolves the contradiction by applying image averaging only where necessary rather than uniformly across the entire area.
Solution Approach 2:
The number of scans and averaging factor are changed as parameters based on region characteristics. Regions with low electron yield undergo more scans and greater averaging to improve signal quality, while regions with high electron yield use fewer scans. This parameter variation resolves the contradiction by adapting the acquisition duration to the specific needs of each region.
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 improves image quality by adjusting scan rates and electron illumination according to region-specific parameters, effectively handling high and low electron yield regions, thereby enhancing defect review efficiency in complex manufacturing processes.
Implementation Method 1
The electron yield of the bottom of the high aspect ratio hole may be the ratio between (a) a number of electrons that originate from the bottom of the high aspect ratio hole and may be detected by the SEM as a result of an irradiation of the high aspect ratio hole and (b) the number of electrons that irradiate the high aspect ratio hole
Data Source
AI summary
A system for scanning an object, the system may include (a) charged particles optics that is configured to: scan, with a charged particle beam and at a first scan rate, a first region of interest (ROI) of an area of the object; detect first particles that were generated as a result of the scanning of the first ROI; scan, with the charged particle beam and at a second scan rate, a second ROI of the area of the object; wherein the second scan rate is lower than the first scan rate; wherein first ROI differs from the second ROI by at least one parameter; detect second particles that were generated as a result of the scanning of the second ROA; and (b) a processor that is configured to generate at least one image of the area in response to the first and second particles.