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

Germanium MOS capacitors with high-quality gate dielectrics are fabricated by novel processing in wet ambients. Wet NO oxidation with wet N
₂
annealing is used to grow GeON gate dielectric on Ge substrate. As compared to dry NO oxidation, negligible growth of unstable GeO
_x
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 N
₂
annealing. It is found that wet N
₂
anneal can also greatly suppress the growth of unstable GeO
_x
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 GeO
_x
in water-containing ambient