OPTIMIZATION OF GATE DOPANT CONCENTRATION AND MICROSTRUCTURE FOR IMPROVED ELECTRICAL AND RELIABILITY CHARACTERISTICS OF ULTRATHIN OXIDES AND N2O OXYNITRIDES

We study the effects of gate dopant species (boron, arsenic, or phosph orous) concentration (1x10(19) cm(-3)-1x10(21) cm(-3)) and microstruct ure (as-deposited amorphous or polycrystalline silicon gate) on the el ectrical and reliability characteristics of ultrathin oxides and N2O o xynitrides (60 Angstrom). In order to minimize polysilicon depletion, a high gate dopant concentration is desirable. However, for devices wi th BF2 doped gates, it is found that because of baron penetration thro ugh the thin gate oxide, device characteristics degrade as the gate do ping concentration increases, thus an intermediate gate doping must be chosen. In contrast, samples with arsenic and phosphorous doped gates show no degradation as the doping level increases. Optimization of ga te microstructure for N2O and O-2 dielectrics is also discussed. (C) 1 996 American Institute of Physics.