SEM Image Merging for High-Precision Critical Dimension Measurement
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Solution Overview
Problem
Current methods for measuring critical dimensions (CD) in semiconductor devices face errors due to limitations in resolution and accuracy, especially as semiconductor design rules become more stringent and patterns become smaller.
Innovation Solution
A method involving the formation of multiple non-overlapping patterns on a substrate, creation of multiple SEM images from different areas, merging these images to enhance resolution, and measuring CD using the merged image, which allows for accurate CD measurement across different chip areas with improved precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single SEM image is used for CD measurement, then the measurement process is simple and fast, but the resolution and measurement precision are insufficient for small patterns
Solution Approach 1:
The substrate is divided into multiple non-overlapping areas, and separate SEM images are acquired for each area. This segmentation allows the total field of view to be larger than what a single SEM image can capture, enabling measurement of patterns that span across multiple areas while maintaining high resolution in each segment.
Solution Approach 2:
Multiple SEM images from different areas are merged into a single composite image. The merging process aligns and combines the images to create a high-resolution overview that preserves the detail from each individual image while expanding the total measurement area, thus improving CD measurement precision without sacrificing resolution.
2Quantity of substance
If the SEM scanning area is increased to cover more patterns, then more patterns can be measured, but the resolution decreases
Solution Approach 1:
Instead of capturing one large low-resolution image, the measurement area is segmented into multiple smaller regions, each imaged at high resolution. This allows the system to maintain high scanning resolution for each individual area while collectively covering a large number of patterns across all areas.
Solution Approach 2:
The solution transitions from a single two-dimensional image to a composite image formed by combining multiple two-dimensional images in space. By acquiring images from multiple non-overlapping areas and merging them, the system effectively adds a spatial dimension to the measurement, enabling both large coverage and high resolution simultaneously.
3Measurement precision
If multiple images are merged to increase resolution, then CD measurement accuracy improves, but the processing time and complexity increase
Solution Approach 1:
Multiple SEM images are acquired in advance from different areas before the merging process. By preparing these individual high-resolution images separately, the system can then efficiently combine them using image processing algorithms, reducing the overall processing time compared to attempting to capture everything in a single low-resolution image that would require extensive post-processing to enhance.
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 reduces measurement errors by increasing the resolution of the merged image, enabling accurate CD measurement in both the same and perpendicular directions to the scanning direction, thus enhancing the precision and reliability of critical dimension assessments.
Implementation Method 1
scanning each of the first to n-th areas using a scanning electron microscope
Data Source
AI summary
A method of measuring a critical dimension (CD) includes forming a plurality of patterns in a substrate, creating first to n-th images, where n is a natural number greater than 1, for first to n-th areas in the substrate, respectively, where the first to n-th areas do not overlap with each other, where each of the first to n-th areas comprising at least some of the plurality of patterns, creating a merged image for the first to n-th images, and measuring a CD for a measurement object from the plurality of patterns using the merged image. The merged image has a higher resolution than each of the first to n-th images.