Imaging Dielectric Breakdown in Valence Change Memory

Abstract

Dielectric breakdown (DB) controls the failure, and increasingly the function, of microelectronic devices. Standard imaging techniques, which generate contrast based on physical structure, struggle to visualize this electronic process. Here in situ scanning transmission electron microscopy (STEM) electron beam‐induced current (EBIC) imaging of DB in Pt/HfO2/Ti valence change memory devices is reported. STEM EBIC imaging directly visualizes the electronic signatures of DB, namely local changes in the conductivity and in the electric field, with high spatial resolution and good contrast. DB is observed to proceed through two distinct structures arranged in series: a volatile, “soft” filament created by electron injection; and a non‐volatile, “hard” filament created by oxygen‐vacancy aggregation. This picture makes a physical distinction between “soft” and “hard” DB, while at the same time accommodating “progressive” DB, where the relative lengths of the hard and soft filaments can change on a continuum.

Quantum Conductance in Memristive Devices: Fundamentals, Developments, and Applications

“…[198,199] Interesting new results are emerging from the development of techniques based upon the emission of secondary electrons (SEEBIC) and integrated differential phase contrast (iDPC) modes in TEM that are sensitive to local electric fields with nanoscale resolution. [200] For the analysis of microscale redox processes occurring inside the switching layer, X-ray techniques including PEEM and HAXPES have been able to provide valence states of the filament in different conductive states. [201,202] High spatial Figure 13.…”

Separation of EBIC Modes with Two-Channel STEM EBIC

“…Recently demonstrated in STEM, SEEBIC imaging measures the holes left behind by the emission of secondary electrons (SEs) from the sample [2]. SEEBIC is capable of much higher resolution than standard EBIC [3] and can generate contrast related to a number of different electronic properties, including conductivity [4,5]. While standard EBIC requires a local electric field, SEEBIC is virtually always present; any STEM EBIC image with standard EBIC contrast also has a (typically much smaller) SEEBIC component.…”

“…If, however, the sample is connected to two or more paths to ground, Fig. 1A, the hole will reach ground preferentially through the lowest resistance path and generate "differential SEEBIC" conductivity contrast [4,5]. For example, the SEEBIC-generated hole in Fig.…”

Determining the Polarization Fraction of Thin Film Ferroelectric HZO with STEM EBIC

“…Traditional STEM is insensitive to a material's electronic properties, but EBIC can reveal local electric fields and conductivity changes [8]. Standard STEM imaging of these devices (Figs.…”