Improved interface properties of Ge metal-oxide-semiconductor capacitor with TaTiO gate dielectric by using in situ TaON passivation interlayer

Abstract

TaON is in situ formed as a passivating interlayer in Ge metal-oxide-semiconductor (MOS) capacitors with high-k TaTiO gate dielectric fabricated simply by alternate sputtering of Ta and Ti. Also, postdeposition annealing is performed in wet N 2 to suppress the growth of unstable GeO x at the Ge surface. As a result, excellent electrical properties of the Ge MOS devices are demonstrated, such as high equivalent dielectric constant (22.1), low interface-state density (7.3× 10 11 cm -2 eV), small gate leakage current (8.6× 10 -4 A cm -2 at V g -V fb =1 V), and high device reliability. Transmission electron microscopy and x-ray photoelectron spectroscopy support that all these should be attributed to the fact that the nitrogen barrier in the TaON interlayer can effectively block the interdiffusions of Ge and Ta, and the wet- N 2 anneal can significantly suppress the growth of unstable low-k GeO x. © 2011 American Institute of Physics.