Partial conversion as a first silicidation process to fabricate low-resistive and low-leakage nickel silicide film in advanced CMOSs

The authors proposed the application of partial conversion (PC) as a first silicidation process. The key to PC in silicidation is leaving sputtered metal on the silicide after the first silicidation. The authors defined the metal-consumption ratio (MCR) as a process parameter of the first silicidation to characterize the stack structure of the films. The PC process drastically improved the resistance of the silicide on the narrow active lines between gate canyons. With a low MCR in PC, the Pt in the Ni-Pt silicide was enriched due to Pt being supplied from the unconsumed Ni-Pt alloy on the silicide during the first silicidation. Therefore, the PC process with a low MCR led to the fabrication of nickel mono-silicide without the formation of nickel di-silicide on the narrow active lines between gate canyons after two-step silicidation. Therefore, we successfully attained Ni-Pt mono-silicide with low resistivity, i.e., 16.4 x 10^-8 Ω-m, consisting of nominal 15-nm thick silicide on 35-nm wide p+ active lines between gate canyons fabricated by PC at an MCR of 50%. Furthermore, we reduced the standby leakage current of SRAMs fabricated by PC by suppressing the formation of nickel di-silicide.