BORON PENETRATION AND HOT-CARRIER EFFECTS IN SURFACE-CHANNEL PMOSFETSWITH P(-SI GATES() POLY)

Surface-channel PMOSFETs are suitable for use in the quarter micron CM OS devices. For surface-channel PMOSFETs with p(+) poly-Si gates, boro n penetration and hot-carrier effects were investigated. When the anne aling temperature is higher and the gate oxide is thinner, a larger th reshold voltage shift was observed for p(+) poly-Si PMOSFETs, because of boron penetration. Furthermore, PMOSFETs with BF2-implanted gates c ause larger boron penetration than those with Boron-implanted gates. H owever, the PMOSFET lifetime, determined by hot-carrier reliability, d oes not depend on the degree of boron penetration. Instead, it depends on doping species, that is, BF2 and Boron. PMOSFETs with BF2-implante d gates have about 100 times longer lifetime than those with Boron-imp lanted gates. The main reason for the longer lifetime of BF2-doped PMO SFETs is the incorporation of fluorine in the gate oxide of the PMOSFE T with the BF2-implanted gate, resulting in the smaller electron trapp ing in the gate oxide. The maximum allowed supply voltage, based on th e hot-carrier reliability, is higher than /-4/ V for sub-half micron P MOSFETs with BF2- or Boron-implanted poly Si gates.