edfas.org ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 26 NO. 1 14 ADVANCED CHARACTERIZATION OF MATERIALS USING ATOM PROBE TOMOGRAPHY Jacob M. Garcia and Ann N. Chiaramonti National Institute of Standards and Technology, Applied Chemicals and Materials Division, Boulder, Colorado jacob.garcia@nist.gov EDFAAO (2024) 1:14-21 1537-0755/$19.00 ©ASM International® INTRODUCTION Electronic device failures are influenced by numerous factors, including the choice of material and associated processing methods, as well as the service conditions the device will see, e.g., temperature excursion, electric current, mechanical or thermal stress, cyclic or static electric fields. The fundamental factors that influence failure modes come down to the interplay between atoms within the material. Among the analytical techniques that provide sub-nm spatially resolved chemical information, atom probe tomography (APT) has emerged as the best compromise between analytical sensitivity and spatial resolution, as compared to other analytical methods such as secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM). Owing to the single atom specificity, APT can provide 3D chemical maps, or tomograms, of samples comprising any element or isotope in the periodic table, with sub-nm spatial resolution in three dimensions. The ability to provide 3D reconstructions with sub-nm spatial resolution, and elemental specificity in the ppm range in some cases, has proven useful for diverse applications. To date, APT has been utilized for compositional profiling of geological minerals,[1] the direct observation of H poisoning at grain boundaries in steel,[2] cryogenically frozen biomaterial analyses,[3] and elucidating the atomic scale structure and composition of electronic materials and devices,[4] to name a few. Atom probe tomography is an evolution of field ion microscopy, which provided the first direct glimpse of atoms in 1955, but at the time worked exclusively on metals.[5] The first atom probe microscope followed in 1967 and has been iteratively improved by many groups since then, with improvements in spatial resolution, mass resolving power, and analytical sensitivity, as well as the variety of materials that can be analyzed through the addition of 3D detectors, energy compensating optics, local electrodes, and advances in pulsed laser technology. APT will be briefly reviewed here, focusing on the capabilities and advances to assist in the characterization of electronic devices. New materials integration and improved design can be promoted by using atom probe tomography as an analysis technique, shown through the following diverse examples in this article. EXPERIMENTAL OVERVIEW The sub-nm spatial resolution and analytical sensitivity of APT is obtained through a process known as field ion evaporation. Field evaporation requires applying a high standing voltage (1 to 10 kV) to a needle-shaped Fig. 1 A schematic showing the incoming laser pulse to a sample tip, resulting in field evaporation followed by ion detection on a 2D detector. Adapted from Ref 9.
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