FIB-SEM 3D Tomography for HAR Structure Shape Deviation Metrology
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Solution Overview
Problem
Current 2D imaging techniques for integrated semiconductor devices are inadequate for accurately capturing the 3D shape and trajectory of high aspect ratio (HAR) structures, such as pillars and channels, due to limitations in capturing non-planar shapes and potential errors in material removal during cross-sectioning.
Innovation Solution
A method utilizing a charged particle beam system for cross-sectioning and imaging integrated semiconductors, generating a 3D volume image by registering a series of 2D cross-section images, allowing for high-precision reconstruction and analysis of HAR structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If 2D imaging techniques are used for cross-sectioning integrated semiconductors, then the imaging process is simple and fast, but the measurement precision of HAR structure shape and trajectory is insufficient
Solution Approach 1:
The patent transitions from 2D cross-sectional imaging to 3D volumetric imaging by introducing a third dimension (depth/z-axis) through serial sectioning and image stacking. This dimensional upgrade enables accurate reconstruction of HAR structure trajectories and shapes that cannot be captured in single 2D planes, directly resolving the measurement precision limitation while accepting increased system complexity.
Solution Approach 2:
The imaging process is segmented into multiple discrete 2D cross-sectional acquisitions at different depths, which are then computationally reconstructed into a 3D volume. This segmentation approach allows precise measurement of vertical trajectories by analyzing the spatial relationship between sequential sections, overcoming the fundamental limitation of single-plane 2D imaging.
2Measurement precision
If material removal is performed during cross-sectioning, then sequential imaging planes are obtained, but errors in material removal affect reconstruction accuracy
Solution Approach 1:
The system incorporates feedback mechanisms where each acquired 2D cross-section is immediately registered and aligned to the growing 3D volume model. This real-time feedback allows detection and correction of positioning or material removal errors before they propagate through the complete reconstruction, maintaining high accuracy despite the sequential nature of the process.
Solution Approach 2:
Instead of relying solely on physical material removal accuracy, the patent creates digital copies (3D volumetric models) from multiple 2D cross-sections. This digital reconstruction process compensates for minor physical sectioning errors by using computational alignment and registration algorithms to reconstruct the true 3D geometry of HAR structures.
3Measurement precision
If 3D volume image is generated by registering series of 2D cross-section images, then accurate 3D reconstruction is achieved, but the processing time and computational resources increase
Solution Approach 1:
The system performs preliminary actions by acquiring and storing multiple 2D cross-sectional images with precise metadata (position, orientation, scaling) before the actual 3D reconstruction computation. This pre-processing and organization of data in structured formats enables faster subsequent volumetric rendering and analysis, reducing the computational burden during the critical measurement phase.
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
Enables accurate 3D reconstruction and quantitative metrology of HAR structures, allowing for precise determination of shape properties, trajectories, and defects, with an accuracy of below a few nanometers.
Implementation Method 1
a focused ion beam device (FIB) adapted for milling of a series of cross sections of an integrated semiconductor sample
Implementation Method 2
a scanning electron beam microscope (SEM) adapted for imaging of the series of cross sections of the integrated semiconductor sample
Data Source
AI summary
A 3D tomographic inspection method for the inspection of semiconductor features in an inspection volume of a semiconductor wafer includes obtaining a 3D tomographic image, and selecting a plurality of 2D cross section images. The method also includes identifying contours of HAR structures, and extracting deviation parameters. The deviation parameters describe fabrication errors such as displacement, deviation in radius or diameter, area or shape.