SEM Image Processing Device Scanning Direction Decision Unit
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Solution Overview
Problem
Charging phenomena caused by electron beam irradiation lead to shape distortion and uneven brightness in scanning electron microscope images, particularly when dealing with curved pattern edges, resulting in image drift and reduced precision.
Innovation Solution
An image processing device that captures and processes SEM images by dividing the field of view into scanning regions, deciding the scanning direction for each region based on the pattern edge, and optimizing the scanning order to minimize electron beam overlap, ensuring the scanning direction is perpendicular to the pattern edge, thereby reducing charging effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the electron beam scans the sample to acquire an image, then image data is captured, but charging phenomenon occurs causing shape distortion and uneven brightness
Solution Approach 1:
The patent divides the field of view into multiple scanning regions and further segments each scanning region into multiple sub-scanning regions. This segmentation allows the electron beam to scan smaller areas sequentially, reducing the total charge accumulated in any single region and minimizing charging effects that cause image distortion and brightness unevenness.
Solution Approach 2:
The patent implements periodic scanning by repeatedly scanning the same scanning region multiple times (first scan, second scan, third scan). Between these periodic scans, the beam scans other regions, allowing charge to dissipate partially before returning to scan the same area again. This periodic action prevents excessive charge accumulation and reduces charging phenomenon.
2Measurement precision
If the electron beam scans curved pattern edges, then the pattern is captured, but overlapping irradiation regions increase charging amount causing image drift
Solution Approach 1:
The patent segments curved pattern edges into multiple scanning regions, where each scanning region contains only a portion of the curved edge. By further dividing these into sub-scanning regions and scanning them sequentially with periodic intervals, the electron beam avoids continuous overlapping irradiation on the same curved edge portion, thereby reducing charge accumulation and preventing image drift.
Solution Approach 2:
The patent applies periodic scanning to curved pattern edges by scanning each sub-region multiple times with intervals. This periodic action allows charge to dissipate between scans, preventing the excessive charge accumulation that would otherwise occur on curved edges and causing image drift.
3Ease of operation
If the scanning direction is not perpendicular to the pattern edge, then scanning is simplified, but pattern edge information becomes missing
Solution Approach 1:
The patent divides the field of view into multiple scanning regions, and for each scanning region, determines the scanning direction based on the local pattern edge orientation. This segmentation allows each region to have its scanning direction optimized perpendicular to its local pattern edge, preventing information loss while maintaining overall scanning simplicity through automated region-by-region processing.
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 high-precision image acquisition on pattern edges by minimizing electron beam overlap and charging influences, resulting in clearer, high-definition images suitable for accurate two-dimensional size measurements.
Implementation Method 1
A scanning electron microscope (SEM) irradiates an electron beam which is emitted from an electron gun on a sample to detect a secondary electron generated from a surface of the sample
Implementation Method 2
A charging phenomenon generated by the irradiation of the electron beam on the sample results in shape distortion and unevenness of brightness in the acquired image
Data Source
AI summary
The image processing device has: a scanning direction decision unit which divides an captured image into a plurality of scanning regions and deciding a scanning direction of each scanning region based on a pattern edge captured in each scanning region in the captured image, a scanning order decision unit which performs a raster scan per pixel constituting each scanning region such that the scanning direction of each of the decided scanning region is directed to a horizontal direction of the raster scan, and a scanning image acquisition unit which acquires a scanning image by capturing each scanning region by the scanning-electron-microscope based on the decided scanning order.