Interface studies of tungsten gate metal-oxide-silicon capacitors

The Si/SiO2 interface in 100-nm-thick chemical vapor deposition (CVD) tungs ten gate metal-oxide-semiconductor (MOS) structures exhibits high interface state densities (D-it0>5 x 10(11)/cm(2) eV) after conventional forming gas anneals over varying temperatures and times. In this letter, we show this is a consequence of the low diffusivity and solubility of molecular hydroge n in tungsten and the high temperature CVD process. We have discovered that atomic hydrogen is more effective in passivating tungsten gate MOS interfa ces because of its higher diffusivity in tungsten. Atomic hydrogen can be p roduced (1) by the reaction of aluminum with water vapor when aluminum is e vaporated on the top of tungsten, (2) by hydrogen implantation, and (3) by hydrogen plasma. These techniques can passivate the Si/SiO2 interface effec tively in MOS structures (D-it0<5 x 10(10)/cm(2) eV) with 100-nm thick CVD tungsten gates. (C) 2001 American Institute of Physics.