Radiation Effects in Ion-Implanted SOS Capacitors with Negative Charge

In B+ - implanted silicon-on-sapphire (SOS) capacitors, extended range MIS C(V) measurements have been used to characterize the interfacial charge as a function of Si epitaxial growth temperature (960° - 975°C) for slow growth rate (.3 - 168 m/min) films, before and after 1 Mrad (A1203) of Co4 gamma radiation, under a radiation-bias stress of 104 V/cm. Before radiation, it was found that, for a given temperature, the amount of negative charge in the SOS capacitors decreased with increasing epitaxial growth rate, and conversely, for a given slow growth rate, the amount of negative charge in the SOS capacitors increased with increasing growth temperature. After irradiation under bias, it was found that the radiation-induced positive charge linearly added to the negative interfacial charge. The implications of these results upon the radiation-induced backchannel problem in NMOS devices are discussed.