Wafer Cross-Section Metrology Using Multi-Tilt CD-SEM
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Solution Overview
Problem
Existing metrology tools struggle to accurately measure three-dimensional structural elements on semiconductor wafers due to limitations in top-down views, leading to inaccuracies in critical dimension measurements, which can result in manufacturing failures and compromised electrical characteristics of integrated circuits.
Innovation Solution
The use of a metrology tool, such as a Critical Dimension Scanning Electron Microscope (CD-SEM), that takes inline measurements at two different tilt angles to generate inspection images and waveform plots, allowing for the formation of a comparative representation to accurately calculate cross-sectional features like height and sidewall angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a top-down view is used to measure structural elements, then the measurement process is simple and fast, but the measurement precision of three-dimensional features is insufficient
Solution Approach 1:
The patent applies dimensionality change by transitioning from a two-dimensional top-down view to a three-dimensional measurement approach. By scanning the structural element at multiple tilt angles (e.g., 0 degrees and 45 degrees) and combining the inspection images, the system captures depth information and calculates cross-sectional features such as height and sidewall angle, thereby achieving accurate three-dimensional measurements.
2Measurement precision
If multiple tilt angle scans are performed to improve measurement accuracy, then cross-sectional feature precision improves, but the measurement time increases
Solution Approach 1:
The patent implements periodic action by performing scans at multiple discrete tilt angles in a sequential manner. The structural element is scanned at a first tilt angle to generate a first inspection image, then scanned at a second tilt angle to generate a second inspection image. This periodic scanning approach allows the system to accumulate sufficient data for accurate three-dimensional reconstruction while maintaining a manageable measurement cycle.
Solution Approach 2:
The patent applies preliminary action by performing alignment and comparison of inspection images from different tilt angles before final feature calculation. The system pre-processes the images by aligning them based on reference features and then compares them to extract cross-sectional dimensions. This preliminary processing ensures that the subsequent calculations are based on properly registered data, improving accuracy while optimizing the overall measurement workflow.
Data Source
AI summary
Disclosed herein are methods and systems for analyzing a cross-sectional feature of a structural element on a semiconductor wafer to determine whether an isolated or a systemic failure to reach preselected parameters occurred.