Tilted CD-SEM Cross-Section Measurement for Wafer Feature Accuracy
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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
A method and system using a critical dimension scanning electron microscope (CD-SEM) that takes inline measurements at two different tilt angles to generate comparative inspection images and waveform plots, allowing for accurate calculation of cross-sectional features like height and sidewall angle, even for curved structural elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
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 deteriorates
Solution Approach 1:
The patent transitions from two-dimensional top-down viewing to three-dimensional measurement by introducing tilt angles. The structural element is viewed from multiple angular perspectives (different tilt angles) to capture cross-sectional features, enabling accurate measurement of height, sidewall angle, and other three-dimensional characteristics that cannot be obtained from a single top-down view.
2Measurement precision
If multiple measurement angles are used to improve three-dimensional measurement accuracy, then measurement precision improves, but device complexity and measurement time increase
Solution Approach 1:
The metrology tool is configured with multi-functionality to perform both top-down viewing and tilted-angle scanning operations. This allows a single instrument to handle both two-dimensional pattern inspection and three-dimensional cross-sectional measurement, eliminating the need for separate specialized equipment and reducing overall system complexity.
Solution Approach 2:
The measurement system dynamically adjusts the viewing angle through tilt mechanisms. The metrology tool can change its scanning angle adaptively to capture different cross-sectional views of the structural element, enabling flexible three-dimensional measurement without requiring multiple fixed-angle instruments.
3Measurement precision
If multiple measurement angles are used to improve three-dimensional measurement accuracy, then measurement precision improves, but measurement time increases
Solution Approach 1:
The patent combines multiple measurement operations into a single integrated scanning process. By merging the acquisition of images at different tilt angles into one continuous measurement sequence, the system reduces the total measurement time compared to performing separate measurements for each angle, while still capturing all necessary data for three-dimensional feature extraction.
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 provides reliable and accurate approximation of three-dimensional structural elements' features without the need for reference structures, reducing process variations and improving design-to-process sensitivity, thereby enhancing the quality of semiconductor wafers and integrated circuits.
Implementation Method 1
scanning, at a first tilt angle, a first location on a structural element and generating a first inspection image and scanning, at a second tilt angle, a second location on the structural element and generating a second inspection image
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.