Hot-carrier effects in surface-channel PMOSFETs with BF/sub 2/- or boron-implanted gates

Abstract

Hot-carrier effects for surface-channel PMOSFETs with p/sup +/ poly-Si gates were investigated. When the annealing temperature is higher and the gate oxide thickness is thinner, larger boron penetration is observed for p/sup +/ poly-Si PMOSFETs. As a dopant for poly-Si gates, BF/sub 2/ causes larger boron penetration. However, PMOSFET lifetime does not depend on the degree of boron penetration, but on doping species (BF/sub 2/ or boron). PMOSFETs with BF/sub 2/-implanted gates have about 100 times longer lifetime than those with boron-implanted gates, because electron trapping in the gate oxide with the BF/sub 2/-implanted gate is smaller due to the incorporation of fluorine. The maximum allowed supply voltage, based on the hot-carrier reliability, is higher than mod -4 mod V for sub half-micron PMOSFETs with p/sup +/ poly Si gates.<>