28nm Device improvement studies by replacing Indium with Gallium halo

Optimization of halo profile for advanced MOSFET device is known to be very critical and challenging. Halo profiles around channel can cause carrier mobility degradation, leakage and higher Vt mismatch. Indium and high scattering P-type dopant (HS-P) mixed halo formation have been used widely for n-FET devices. Gallium has a better activation than Indium and is heavier specie than HS-P. Gallium could be promising specie for device improvement through halo optimization in planar devices or ground plane/retrograde well for better FinFET leakage characteristics. In this paper, Gallium is used to replace Indium halo on bare and device wafers using a poly-SiON 28nm process. Secondary Ion Mass Spectroscopy (SIMS) was employed for dopant profiles after anneals. Device gain in drive current with better Drain Induced Barrier Lowering or DIBL by 12mV was observed when Gallium replaced Indium in the HS-P/Indium mixed halo. The observed excessive device shift when Gallium was used to replace HS-P halo will be discussed in a future study. Ga for halo formation is not an plug/play and the interaction among the co-implant and dopant through implant induced damage should be investigated in the integration flow.