Preparation of high-quality gate dielectrics for Ge MOSFET's in wet ambients

Abstract

Germanium MOS capacitors with high-quality gate dielectrics are fabricated by novel processing in wet ambients. Wet NO oxidation with wet N2 annealing is used to grow GeON gate dielectric on Ge substrate. As compared to dry NO oxidation, negligible growth of unstable GeOx interlayer and thus a near-perfect GeON dielectric can be obtained. This idea is extended to high-k gate dielectric (HfTiON), which is prepared by reactive co-sputtering followed by wet N2 annealing. It is found that wet N2 anneal can also greatly suppress the growth of unstable GeOx at the HfTiON/Ge interface. As a result, the properties of Ge MOS capacitors prepared in wet ambient are greatly improved with lower interface-state and oxide-charge densities, and reduced gate leakage current. All these should be attributed to the hydrolysable property of GeOx in water-containing ambient. © 2006 IEEE.