Optimized Germanium co-implant with B2H6 PLAD for better advanced PMOS device performance

Abstract

This work demonstrates that the sequence of a Ge co-implant with a B2H6 PLAD in the source/drain is very critical in order to improve advanced PMOS performance. Locating the Ge co-implant after the B2H6 PLAD resulted in higher total retained B dose and less implant damage. PMOS performance was significantly improved compared to B2H6 PLAD without the Ge co-implant or Ge co-implant before B2H6 PLAD. The Ge implant energy was optimized to locate the Ge peak around the B deposition layer/Si substrate interface for a better knocking effect and less implant damage. With the optimized Ge implant conditions the source/drain contact resistance and sheet resistance were significantly reduced, while the junction leakage current was not degraded. As a result, PMOS Ids improved by 12%, transconductance KL improved by 14%, and IOFF variation improved by 33% without significant change in mean IOFF. This process helps overcome technical challenges of B2H6 PLAD, providing a path for continued scaling of PMOS junction depth with improved device performance.