Process Development of Amorphous Indium Tin Gallium Oxide (ITGO) Thin Film Transistors

Abstract

The focus of this study is an investigation on Indium-Tin-Gallium-Oxide (ITGO) TFTs. Unpassivated bottom-gate devices werefabricated with a sputter-deposited 30nm a-ITGO film with 1% and10% oxygen gas ambient, followed by a 1 or 2 hour anneal at 300oCin oxygen. Devices fabricated with PO2 = 1% resulted in a highlyconductive channel, whereas devices with PO2 = 10% displayedsemiconducting behavior and a shallow subthreshold. Followingaging in room ambient for multiple days, devices displayed left-shifted transfer characteristics with steep subthreshold. It ishypothesized that the unpassivated back-channel attains a morehomogeneous trap distribution. The ITGO devices demonstrate aneffective channel mobility approximately 2.5 times higher thanIGZO TFTs. Radial variation in device performance can beattributed to non-uniformities in the as-deposited ITGO film, with acorrelation to the distribution in optical constants across the wafer.