Controlled Stepwise Wet Etching of Polycrystalline Mo Nanowires

Abstract

With the persistent downscaling of integrated circuits, molybdenum (Mo) is currently considered a potential replacement for copper (Cu) as a material for metal interconnects. However, fabricating metal nanostructures with critical dimensions of the order of 10 nm and below is challenging. This is because the very high density of grain boundaries (GBs) results in highly non‐uniform surface profiles during direct wet etching. Moreover, wet etching of Mo with conventional aqueous solutions is problematic, as products of Mo oxidation have different solubility in water, which leads to increased surface roughness. Here, a process is shown for achieving a stable and uniform soluble surface layer of Mo oxide by wet oxidation with H2O2 dissolved in IPA at −20 °C. The oxide layer is then selectively dissolved, and by repeating the oxidation and dissolution multiple times, a uniform etch profile is demonstrated with a fine control over the metal recess. Ultimately, this presents a method of precise and uniform wet etching for Mo and other metals needed to fabricate complex nanostructures that are critical in developing next‐generation electronic devices.

Abnormal Silicon Etching Behaviors in Nanometer-Sized Channels

“…Herein, wet etching processes of encapsulated silicon nanostructures are first visualized with in situ liquid-phase transmission electron microscopy (LP-TEM). − Recently, LP-TEM emerged as a critical tool for addressing the problem in the wet process of microfabrication, for example, investigation of a new metal candidate and its process, faceting of c-Si nanopillars for 3D transistors, and selective etching behavior of Si–Ge composites . We create structures analogous to dummy polycrystalline silicon gates on silicon nitride (SiN x ) chips that enable in situ and ex situ transmission electron microscopy (TEM) observations of wet etching processes.…”