Improvements in both thermal stability of Ni-silicide and electrical reliability of gate oxides using a stacked polysilicon gate structure

Abstract

A process design is presented for improving the thermal stability of Ni-silicide (nickel-silicide) using a stacked polysilicon gate structure. The Ni-silicide formed has low sheet resistance up to 800 degreesC on a silicidation process. Additionally, the metal-oxide-semiconductor (MOS) capacitors fabricated using these proposed gate structures demonstrate higher electrical reliability for gate oxides than those of nonstacked films. That is, the gate oxides of the MOS capacitors were only slightly degraded after silicidation step at 800 degreesC. In conclusion, the Ni-silicide formed on those stacked polysilicon gates are attractive in fabricating ultralarge scale integration (ULSI) circuits because both the thermal stability of Ni-silicide and the reliability of gate oxides are improved simultaneously. (C) 2001 The Electrochemical Society.