Phase and Composition Control of Ni Fully Silicided Gates by Nitrogen Ion Implantation and Double Ni Silicidation

Abstract

The phase and composition control of a Ni fully silicided (Ni-FUSI) gate electrode is investigated to achieve a wider process window for complementary metal–oxide–semiconductor (CMOS) device integration. We performed nitrogen ion implantation (N2 I/I) on polycrystalline silicon (poly-Si) prior to Ni deposition only for an n-MOS gate. The implanted nitrogen in the poly-Si layer suppresses the reaction of Ni and Si. As a consequence, the process temperature for Ni silicidation increased by ∼20 °C compared with that in the case without implantation. It was also found that the grain size of the Ni silicide found in the N2 I/I-treated poly-Si layer is smaller, possibly due to nitrogen atoms bound to Si and/or cavities generated inside the poly-Si layer. We also propose double Ni silicidation for fabricating a p-MOS gate, where a Ni-rich silicide was formed by carrying out an additional Ni deposition and annealing on a Ni silicide film. The Ni-rich silicide was evaluated in terms of X-ray diffraction patterns and flat band voltage shifts on capacitance–voltage measurement. Combining these techniques will enable the development of an optimized process integration scheme for CMOS devices.