Rotatable Needle TEM Sample Mounting for Orthogonal Imaging
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Solution Overview
Problem
Current methods for inspecting integrated circuits (ICs) using transmission electron microscopy face challenges in accurately characterizing three-dimensional features due to issues like warping, bending, and non-uniform thickness of extracted lamellae, which limits the resolution and reliability of measurements.
Innovation Solution
A method involving a sample with multiple orthogonal faces mounted on a rotatable needle within a transmission electron microscope, allowing for the exposure of these faces to an electron beam at various angles to capture high-resolution orthogonal images, rather than relying on tomographic reconstruction from multiple angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If extracted lamellae are used for TEM analysis, then thin cross-sectional samples can be obtained, but warping, bending, and non-uniform thickness occur leading to poor measurement accuracy
Solution Approach 1:
The patent uses disposable sacrificial support structures (such as silicon dioxide or silicon nitride layers) that are removed after sample preparation. These support structures provide temporary mechanical stability during FIB milling and sample extraction, preventing warping and bending, but are then discarded in a final cleanup step. This resolves the contradiction by providing the mechanical support needed for uniform thickness without compromising the final measurement reliability.
Solution Approach 2:
The patent employs controlled parameter changes during the FIB milling process, including adjusting ion beam current, milling depth, and support structure thickness. By carefully controlling these parameters, the process achieves uniform sample thickness while preventing warping and bending. The support structure thickness is specifically tuned to provide adequate support during preparation but be removable afterward, resolving the contradiction between manufacturing precision and measurement reliability.
2Loss of information
If electron tomography is performed to obtain three dimensional images, then 3D characterization is achieved, but time-consuming tomographic reconstruction is required
Solution Approach 1:
The patent extracts and characterizes specific features of interest from the sample using targeted FIB milling and TEM imaging of prepared cross-sections. Instead of performing complete 3D tomographic reconstruction, the method extracts the necessary dimensional information from strategically prepared samples, eliminating the time-consuming reconstruction process while retaining the essential three-dimensional characterization data needed for IC analysis.
Solution Approach 2:
The patent performs preliminary sample preparation including FIB milling to create precisely positioned cross-sections and lamellae before TEM imaging. By pre-positioning the sample to reveal specific features of interest and preparing targeted cross-sections, the method obtains the necessary three-dimensional information directly from 2D images without requiring subsequent tomographic reconstruction, thus saving time while maintaining information completeness.
3Measurement precision
If multiple separate lamellae are extracted in three different viewing directions, then complete three dimensional characterization is achieved, but the process becomes more complex and time-consuming
Solution Approach 1:
The patent combines multiple viewing directions and measurement capabilities into a single integrated sample preparation approach. By using FIB milling to create samples with multiple exposed faces or by preparing a single sample that can be rotated to different orientations, the method merges what would traditionally require multiple separate lamellae extractions. This reduces preparation complexity while maintaining the ability to obtain precise three-dimensional measurements from multiple viewing angles.
Solution Approach 2:
The patent employs dynamic sample manipulation during TEM analysis, including rotating the sample holder to view the same sample from multiple angles and orientations. This dynamic approach allows a single prepared sample to provide information from multiple viewing directions, eliminating the need for multiple static lamellae extractions. The sample is kept fixed during preparation but dynamically repositioned during analysis, reducing preparation complexity while maintaining measurement precision.
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 enables quicker and more accurate measurement of IC features by obtaining high-resolution orthogonal images directly, improving the characterization of IC components without the need for time-consuming tomographic reconstruction.
Implementation Method 1
TEM samples are viewed by transmitting a beam of electrons through the sample and detecting the transmitted electrons on the opposite side to form the image
Implementation Method 2
In electron tomography, the sample (or beam) is tilted through a series of tilt angles, with an image formed at each of the different tilt angles, to provide data that can be used to mathematically reconstruct a three dimensional image
Data Source
AI summary
A system and method for transmission electron microscopy is provided. The sample can be examined from multiple directions using an electron beam in a transmission electron microscope. The sample has at least three observation faces that are not parallel to each other with the thickness of the sample orthogonal to each of the observation faces being less than 200 nm. The sample is mounted on a needle that is needle rotatable about more than one axis so the needle can orient at least three of the observation faces to be normal to the electron beam of the electron microscope for observation.