SEM Image Alignment Across Scan Directions to Reduce Charging Artifacts
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Solution Overview
Problem
Scanning electron microscope (SEM) images of electrically insulating materials suffer from SEM-induced charging artifacts, leading to inaccuracies in dimension metrology and defect detection due to distortions caused by charge accumulation during electron beam scanning.
Innovation Solution
Obtaining multiple SEM images of a target feature from different scanning directions and aligning them using positional offsets to generate a combined output image, which reduces the impact of charging-induced distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple SEM images are acquired and combined to reduce charging artifacts, then measurement precision improves, but inspection time increases
Solution Approach 1:
The patent applies preliminary action by performing alignment and combination operations on SEM images acquired from different scan directions. By pre-processing multiple images to compensate for charging artifacts before final measurement, the system achieves higher measurement precision without requiring real-time corrections during inspection
Solution Approach 2:
The patent merges multiple SEM images obtained from different scanning directions into a single combined image. This combination process integrates information from multiple scans to produce an output image with reduced charging artifacts, thereby improving measurement precision while distributing the time cost across parallel or sequential image acquisitions
2Difficulty of detecting and measuring
If SEM imaging is performed on electrically insulating materials, then defect detection capability is maintained, but image quality deteriorates due to charging artifacts
Solution Approach 1:
The patent converts the harmful charging artifacts into beneficial information by acquiring images from multiple scan directions. The charging artifacts appear differently in each scan direction, and by combining these images with appropriate alignment, the system eliminates the artifacts while preserving the actual defect information, thus improving image quality without sacrificing defect detection capability
Solution Approach 2:
The patent introduces an additional dimension to the imaging process by scanning from multiple directions rather than a single direction. This multi-directional approach adds a spatial dimension to the data collection, allowing the system to differentiate between actual sample features and charging artifacts through comparative analysis across different scan angles
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
The method significantly improves the accuracy of SEM images by minimizing charging artifacts, resulting in more faithful representations of the sample structures and reducing errors in measurements, such as edge placement and critical dimension analysis.
Implementation Method 1
obtaining a first SEM image of a target feature on a sample from a first electron beam scan in a first scanning direction
Implementation Method 2
SEM images of electrically insulating materials suffer from SEM-induced charging artifacts, leading to inaccuracies in dimension metrology and defect detection due to distortions caused by charge accumulation during electron beam scanning
Data Source
AI summary
Disclosed herein is a method of reducing a sample charging effect in a scanning electron microscope (SEM) image, the method comprising: obtaining a first SEM image of a target feature on a sample from a first electron beam scan in a first scanning direction; obtaining a second SEM image of the target feature on the sample from a second electron beam scan in a second scanning direction different from the first scanning direction; aligning the first SEM image and the second SEM image; and generating an output image based a combination of the first SEM image and the second SEM image.