Oxide electronics: Translating materials science from lab-to-fab

Abstract

Advances in the science and technology of thin-film materials have fueled a myriad of developments in large area electronics. This is particularly true for amorphous oxide semiconductors. Oxides have underpinned a number of technologically significant innovations in displays, sensors, and photovoltaics. Now they are setting the stage for exciting new applications related to flexible electronics and three-dimensional (3D) integration for post-complementary metal oxide semiconductor (CMOS) back-end-of-line processing in the quest for more-than-Moore solutions. This article reviews the development of oxide semiconductors and associated integration processes that have translated materials science fiction to commercial reality on a large scale. These advances have been driven by a host of advantages such as low cost, prudent manufacturing and large area scalability. What makes oxide semiconductors so attractive? These materials have a wide bandgap, which provides for high transparency; a cool feature for seamless embedding of electronics, particularly displays and imagers, for the immersive ambient. The OFF-current in oxide thin-film transistors is ultralow, thanks to the very low density of states in the bandgap. Indeed, this attribute is indispensable to minimize charge leakage in switching transistors and for low power, low-voltage, high-resolution sensor interfaces. More importantly, oxide thin-film transistors can be processed at relatively low temperatures thus making them amenable for 3D integration on post-processed CMOS silicon. This article provides the current status of the oxide semiconductor technology. We review the evolution of oxides based on their functional properties, along with deposition and solution processing techniques for heterostructure thin-film transistors, phototransistors, nanowire image sensors, ultralow power Schottky-barrier transistors, and 3D integration for back-end-of-line CMOS. These devices constitute fundamental building blocks for a new generation of applications ranging from interactive displays and imaging to future 3D electronic systems that are not constrained by form factor.