INFLUENCE OF NITROGEN OR ARGON ANNEALS ON THE PROPERTIES OF WAFERS AND DEVICES SEPARATED BY IMPLANTATION OF OXYGEN

Wafers separated by implantation of oxygen (SIMOX) and annealed at hig h temperature In argon or nitrogen ambient are compared in terms or fi lm, oxide, interface. and device properties. This evaluation is conduc ted by correlating pseudo-metal-oxide-semiconductor field effect trans istor (Psi-MOSFET) data in plain, unprocessed wafers with the performa nce of n- and p-channel transistors. In situ wafer characterization wi th the Psi-MOSFET technique reveals a pileup of nitrogen near the buri ed Si-SiO2, interface, where the electron mobility is degraded. MOSFET characteristics are even more dramatically affected by annealing in n itrogen: large shifts of front- and back-channel threshold voltages, E nhanced leakage currents, and doping modification. Nitrogen-induced do nors are suspected to be responsible for doping compensation in n-chan nels (leading to an unexpected full-depletion mode of operation) and o verdoping in p-channels (reinforcing the partial depletion). By contra st to argon ambient. which does not have any major drawback, nitrogen ambient appears to be unsuitable for annealing of SIMOX wafers.