Reduction of Leakage and Low-Frequency Noise in MOS Transistors Through Two-Step RTA of NiSi-Silicide Technology

A two-step rapid thermal annealing (RTA) nickel salicidation process was employed to fabricate 0.1-mum gate length CMOS transistors. Excess salicidation, common in the conventional one-step RTA NiSi process, is effectively suppressed by this approach, which is confirmed by transmission electron microscopy (TEM) images. More improvements due to two-step NiSi are observed in NMOS than in PMOS transistors: The n
⁺
-p junction diode with two-step NiSi exhibits lower reverse leakage and higher breakdown voltage than the one-step silicided diode. For the first time, it is found that two-step NiSi NMOS exhibits significant reduction in off-state leakage (~5times) and low-frequency noise (up to two orders of magnitude) over one-step NiSi NMOS, although there is not much difference in PMOS transistors