Characteristics of BF3 plasma-doped gate/source/drain for 0.18-μm pMOSFETs

A BF3 plasma doping (PLAD) process has been utilized in shallow source/drain (S/D) extension and source/drain/gate doping for high-performance 0.18-μm pMOSFETs. Low-resistance shallow junctions were obtained using a BF3 PLAD system with a high-performance low-energy boron doping technology. The drive current and transconductance of pMOSFETs with plasma-doped S/D extensions are remarkably improved compared to those of BF2+ ion-implanted devices, due to the low resistance of the S/D extension at the equivalent short-channel-effect characteristics. The fluorine ions in the BF3 plasma-doped silicon are significantly less than in the BF2+ implanted one. In the case of surface channel pMOSFETs with a BF3 plasma-doped gate, the boron penetration and depletion in the gate poly were reduced because of the reduced fluorine incorporation into the gate poly compared to those of a conventional BF2 ion-implanted gate. The improved characteristics of BF3 plasma-doped gate enhance the drive current and gate oxide quality of pMOSFETs compared to conventional BF2+-implanted devices. No plasma damage was identified, and cobalt salicide formation is also very compatible with the plasma-doped p+/n junction.