PMOS device performance improvement by using buried contact implants

An ultra-low energy high dose B-based implant was processed after source and drain region formed and before metal sillicide contact formed for PMOS devices. B beam-line (BL) implant and plasma doping (PLAD) using either B₂H₆ or BF₃ gases were utilized for this process. PMOS device performance showed significant improvements, including ~70 percent lower contact resistances, similar threshold and sub-threshold characteristics, and ~15 percent higher drive currents without degrading off current. PLAD is preferred on this application because of its much higher throughput in this process regime.