Multi-Beam SEM Focus Adjustment via Parallel Image Analysis
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Solution Overview
Problem
Current single-beam scanning electron microscopy (SEM) systems face inefficiencies in focus adjustment, requiring multiple images at different settings and often necessitating astigmatism correction, which prolongs the inspection process and reduces tool availability.
Innovation Solution
A multi-beam SEM system with a controller that simultaneously acquires images from multiple electron beams, identifies the best focus or astigmatism settings by analyzing image quality parameters, and adjusts the electron-optical elements to optimize focus and astigmatism across the image field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple images are acquired at different focus settings in a single-beam SEM, then focus adjustment accuracy is improved, but inspection time increases
Solution Approach 1:
The patent divides the single electron beam into multiple parallel electron beams that simultaneously scan different regions of the sample. Each beam acquires an image in parallel, enabling focus evaluation to be performed simultaneously across multiple focus settings, thus reducing total inspection time while maintaining accuracy.
Solution Approach 2:
The patent introduces a spatial dimension by using multiple parallel beams scanning across the sample surface simultaneously. This parallel acquisition approach transforms the sequential focus measurement process into a concurrent multi-point measurement, resolving the time-accuracy tradeoff.
2Measurement precision
If astigmatism correction is performed in a single-beam SEM, then image quality is improved, but the number of images required increases
Solution Approach 1:
The patent segments the astigmatism correction process into simultaneous measurements across multiple parallel beams. By evaluating astigmatism parameters across multiple beams at once, the system can determine correction settings more efficiently, reducing the total number of images needed while maintaining image quality.
Solution Approach 2:
The patent implements feedback mechanisms where astigmatism parameters are continuously evaluated from multiple beam images and used to dynamically adjust correction settings. This feedback loop enables accurate astigmatism correction with fewer images by iteratively optimizing based on real-time measurements.
3Measurement precision
If multiple images are acquired for focus and astigmatism adjustment in a single-beam SEM, then measurement accuracy is improved, but tool availability decreases
Solution Approach 1:
The patent divides the inspection area into multiple regions scanned by parallel beams simultaneously. This segmentation enables focus and astigmatism parameters to be measured across all regions in parallel, maintaining measurement accuracy while reducing the total time required, thereby improving tool availability.
Solution Approach 2:
The patent maintains continuous useful action by having multiple beams continuously scan and acquire data simultaneously throughout the inspection process. This parallel continuous measurement eliminates idle time between sequential measurements, preserving accuracy while maximizing productivity and tool availability.
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 enables rapid focus adjustment and minimizes astigmatism, significantly reducing the time required for inspection and increasing tool availability by leveraging multiple images to determine optimal focus and astigmatism settings.
Implementation Method 1
a multi-beam electron source configured to form a plurality of electron beams
Implementation Method 2
an electron-optical assembly including a set of electron-optical elements configured to direct at least a portion of the plurality of electron beams onto a portion of the sample
Data Source
AI summary
A scanning electron microscopy system is disclosed. The system includes a multi-beam scanning electron microscopy (SEM) sub-system. The SEM sub-system includes a multi-beam electron source configured to form a plurality of electron beams, a sample stage configured to secure a sample, an electron-optical assembly to direct the electron beams onto a portion of the sample, and a detector assembly configured to simultaneously acquire multiple images of the surface of the sample. The system includes a controller configured to receive the images from the detector assembly, identify a best focus image of images by analyzing one or more image quality parameters of the images, and direct the multi-lens array to adjust a focus of one or more electron beams based on a focus of an electron beam corresponding with the identified best focus image.