In-Line AFM Depth Measurement for Accurate FIB-SEM Delayering
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Solution Overview
Problem
Conventional methods for generating three-dimensional images of delayered regions in electronic structures lack the precision needed for accurate depth measurement during the delayering process, particularly in semiconductor wafers, due to limitations in resolution and alignment of two-dimensional images.
Innovation Solution
Incorporating an atomic force microscope (AFM) within the same vacuum chamber as a scanning electron microscope (SEM) to measure the depth of each slice during the delayering process with high precision, allowing for precise alignment and stacking of slices to create a highly accurate three-dimensional image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional SEM imaging techniques are used to capture slices during delayering, then three-dimensional images can be generated, but the depth measurement precision is insufficient for accurate alignment
Solution Approach 1:
The patent combines the AFM depth measurement system with the SEM imaging system into a single integrated platform. The AFM and SEM share the same vacuum chamber and sample stage, allowing simultaneous or sequential operation without removing the sample. This merging resolves the contradiction by achieving high depth measurement precision while avoiding the complexity of separate independent systems.
Solution Approach 2:
The AFM acts as an intermediary measurement tool between the FIB delayering process and the SEM imaging process. It provides precise depth measurements that serve as reference data for aligning SEM images at different depths, enabling accurate three-dimensional reconstruction without requiring the SEM itself to have high depth measurement capability.
2Reliability
If multiple delayering iterations are performed to capture sufficient slices for 3D imaging, then comprehensive three-dimensional data is obtained, but the time required for analysis increases significantly
Solution Approach 1:
The AFM depth measurements are taken during or immediately after each delayering iteration, before the full SEM image acquisition and processing sequence begins. This preliminary depth characterization allows for real-time tracking of the delayering progress and enables more efficient planning of subsequent imaging steps, reducing the total analysis time while maintaining comprehensive three-dimensional data quality.
Solution Approach 2:
The system uses AFM depth measurements as feedback to monitor the delayering process in real-time. This feedback mechanism allows the operator to adjust delayering parameters dynamically, ensuring that sufficient slices are captured at appropriate intervals without performing excessive iterations, thereby optimizing the balance between three-dimensional image accuracy and analysis time.
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 the generation of highly accurate three-dimensional images by precisely measuring and aligning slices, improving the accuracy of delayered region analysis in semiconductor wafers and similar specimens.
Implementation Method 1
an atomic force microscope (AFM), positioned in situ within a scanning electron microscope (SEM) vacuum chamber, to measure a depth at which each slice of a delayering process is removed
Implementation Method 2
a ROI on a specimen can be bombarded with ions of Xenon, Gallium or other elements generated by a focused ion beam (FIB) column to erode the surface layer of the specimen
Implementation Method 3
SEM imaging techniques can be used to see a surface of a region of interest (ROI) within a specimen
Data Source
AI summary
A method of evaluating a region of interest of a sample with a sample evaluation tool that includes a focused ion beam (FIB) column, a scanning electron microscope (SEM) column, and an atomic force microscope (AFM) instrument, the method comprising: transferring the sample into in a vacuum chamber of the sample evaluation tool; acquiring a plurality of two-dimensional images of the region of interest over a plurality of iterations of a delayering process by: (a) positioning the region of interest under a field of view of the FIB column; (b) milling a layer of material from the region of interest with the FIB column; (c) moving the region of interest under a field of view of the SEM column; (d) imaging the region of interest with the SEM column and measuring a depth of the milled layer in the region of interest with the AFM instrument; and repeating steps (a)-(d) a plurality of times without removing the sample from the vacuum chamber.