Plasma doping for the fabrication of ultra-shallow junctions

Pulsed plasma doping (P(2)LAD) is an alternate doping technique for the formation of ultra-shallow junctions in silicon wafers. In the P(2)LAD technique, a pulsed negative voltage applied to the silicon substrate creates a plasma containing the desired dopant species and also accelerates the positive dopant ions from the plasma toward the substrate, where they are implanted. BF3 plasmas have been used to form p(+)-n junctions, while AsH3 and PH3 plasmas have been used for the formation of n(+)-p junctions. This paper will review the characteristics of ultra-shallow junctions formed by P2LAD. As-implanted and annealed profiles have been obtained by secondary ion mass spectrometry and compared with analogous profiles produced by B+, BF2+ and As+ ion implantation. Good sheet resistance uniformity, charging performance, structural quality, and photoresist integrity have been observed. In addition, junctions have been made which offer trade-offs between sheet resistance and junction depth that are better than those achieved with beamline implants, Finally, sub-0.2 mum pMOSFET devices have been fabricated with P2LAD and exhibit device characteristics that are similar to or better than beamline-implanted ones. (C) 2002 Elsevier Science B.V. All rights reserved.