edfas.org ELECTRONIC DEV ICE FA I LURE ANALYSIS | VOLUME 25 NO . 1 4 EDFAAO (2023) 1:4-8 1537-0755/$19.00 ©ASM International® MAKING CONNECTIONS: CHALLENGES AND OPPORTUNITIES FOR IN SITU TEM BIASING William A. Hubbard NanoElectronic Imaging, Riverside, California bhubbard@nanoelectronicimaging.com INTRODUCTION The transmission electron microscope (TEM) is an essential tool for high-resolution imaging of micro and nano-electronic systems for basic research, fabrication quality control, and failure analysis. Despite the ubiquity of TEM, in situ biasing experiments involving electronic devices are markedly rare, with most examples found in academic studies. This is not for lack of interest, as the ability tooperateor inducedefects indeviceswhileobserving the resulting nanoscale dynamics would undoubtedly provide valuable information. Themain barrier to routine biasing of electronic devices in the TEM is the difficulty in producing electrically contacted samples that are both TEMcompatible and electronically viable. This article discusses sample preparation challenges that have impeded progress in producing bias-enabled TEM samples from electronic components, as well as strategies to mitigate these issues. It will also describe the potential benefits of developing techniques for high-throughput sample fabrication that preserves the electronic behavior of parent devices. Scanning TEM electron beam-induced current (STEMEBIC) is presentedas botha tool uniquely capableof assessing progress in achieving these fabrication goals as well as a complement to standardTEM imaging, producing contrast directly related to a device’s electronic structure, including local conductivity. SAMPLE PREPARATION STRATEGIES AND CHALLENGES The most hindering constraint on samples for TEM imaging is the requirement of electron transparency— that samples be thin (~100 nm or less). Broadly, there are two routes for preparing electronic device TEM samples: extracting a thin cross section (or lamella) from a larger device, and micro-fabricating a device from the ground up to be thin but functional. Cross sectioning, most commonly using a focused ion beam (FIB), enables studying samples from “real” components (i.e., devices that may be deployed in electronic systems), which is particularly appealing for studying failure and reliability. However, surface damage and contamination from the FIB milling process typically degrades the electronic structure of devices. The latter (micro-fabrication) approach enables precise control of device features, straightforward electrical connection, and entirely avoids the damage and contamination associated with FIB preparation. Such devices are well-suited to serve as model systems, where dynamics can be observed in a device that is analogous to a deployed device of interest. Such observations can Fig. 1 SEM images of a Si-based lift-out biasing chip. The Si-based chip supports a thin membrane and Pt electrodes that are patterned up to a trench etched through the membrane which is positioned at the edge of the chip. The lower image is tilted 45 degrees in the direction of the trench.
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