Interface studies of tungsten gate metal-oxide-silicon capacitors

Abstract

The Si/SiO2 interface in 100-nm-thick chemical vapor deposition (CVD) tungsten gate metal-oxide-semiconductor (MOS) structures exhibits high interface state densities (Dit0>5 × 1011/cm2 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 hydrogen in tungsten and the high temperature CVD process. We have discovered that atomic hydrogen is more effective in passivating tungsten gate MOS interfaces because of its higher diffusivity in tungsten. Atomic hydrogen can be produced (1) by the reaction of aluminum with water vapor when aluminum is evaporated on the top of tungsten, (2) by hydrogen implantation, and (3) by hydrogen plasma. These techniques can passivate the Si/SiO2 interface effectively in MOS structures (Dit0 < 5 × 1010/cm2 eV) with 100-nm thick CVD tungsten gates. © 2001 American Institute of Physics.