INVITED: Sputtered Indium Zinc Oxide – new post-deposition processing

Sputtered Indium Zinc Oxide (IZO) is now widely used as the transparent conducting oxide (TCO) of choice in a range of flat panel display technologies.  Deposited at room temperature, these materials offer excellent optical transparency combined with high conductivity along with high surface planarity and isotropic etch characteristics.   A key property of these materials is that their carrier density (and hence conductivity) can be adjusted during sputter deposition to create materials whose properties range from conducting to semiconducting to insulating.   In the past decade, third cation species (such as Ga) have been added to IZO to enable the fabrication of high performance thin film transistors (TFT’s) that, by virtue of higher carrier mobility (10-50 for IZO vs. 0.1-1 cm²/Vsec for Si) and significant processing advantages have displaced deposited thin film Silicon TFT’s for pixel switching purposes.  We report here on the use of IZO and buried reactive metal layers to create buried dielectrics formed by in-situ solid state reaction between selected metals and a-IZO.   Low temperature annealing of thermodynamically unstable interfaces results in the chemical reduction of IZO (creating oxygen vacancies, a defect donor) and the oxidation of the reactive over-layer to create high quality dielectrics and interfaces.   We have used this method [1] to create a new class of high performance devices that will broaden the utility of amorphous oxides beyond simple TFT’s. 

^[1] Y. Song, R. Xu, J. He, S. Siontas, A. Zaslavsky, and D. C. Paine, IEEE Electron Device Lett., 35 (2014) 1251-1253