Low thermal budget titanium-based salicide contacts and their application to 65 GHz fT Si/SiGe-HBT technology

A new, Ti-based salicide process is presented using an RF-sputter technique and conventional furnace annealing. Ohmic contacts have been made to n- and p-type silicon and to p-type SiGe resulting in specific contact resistances of 9.3×10^-8 and 3.6×10^-8 Ω·cm² for n- and p-type Si, and 4.5×10^-8 Ω·cm² for p-type SiGe, respectively. The salicidation was applied to emitter and base contacts of an integrated, selfaligned Si/SiGe-heterojunction bipolar transistor fabricated with a 1.5 μm technology. The maximum post-epitaxial processing temperature could be limited to 650°C. The transistor is marked by a clear emitter-base heterojunction due to a constant Ge fraction of 28% in the base layer. High-frequency measurements resulted in f_T=65 GHz (V_CE=1 V)