| Exposure of MOS devices to ionizing radiation results in an increase in interface trap density at the Si-SiO{dollar}sb2{dollar} interface, build-up of positive charge centers and generation of neutral electron traps in the oxide bulk. In this dissertation, we examine the details of these three processes. Emphasis is placed on the characterization of defects in the Si-SiO{dollar}sb2{dollar} system using MOSFETs fabricated with a self-aligned, poly-gate, N-well, CMOS technology. To quantify the degradation in MOSFET characteristics, which results upon exposure to ionizing radiation, and explore the relationships between interface traps, oxide charges, and mobility degradation, an analytical model is developed for the FET drain current and transconductance. Using this model we have investigated the frequency dependent response of interface traps and have related this phenomenon to the frequency dependent transconductance. A procedure has been developed to extract interface trap density by measuring the frequency dependent transconductance of moderate (1-10 {dollar}mu{dollar}m) channel length devices. To complement the technique developed for moderate channel length devices, an adaptation of the MOS capacitor conductance technique is introduced to study interface trap generation and its relation to inversion layer response and mobility degradation resulting upon irradiation of large area MOSFETs.; We have also developed a theoretical formulation of the conductance of amphoteric interface traps at the Si-SiO{dollar}sb2{dollar} interface.; To study bulk oxide defects a five terminal device called the injector device is proposed. The injector device is a MOSFET surrounded by an implanted p-n junction which when "forward" biased injects minority carriers in the depletion region of the MOSFET. We have made an attempt to establish the role of hydrogen and/or related species in the generation of interface traps and bulk oxide traps upon irradiation. Utilizing the superior radiation tolerance of the ONO gate devices (for the first time we have demonstrated the supression of interface trap generation up to a total dose of 1 M Rad (Si) in 100 A ONO devices), we have fabricated radiation hard, low-voltage programmable, non-volatile, EEPROMs. We have extensively characterized the static and dynamic behavior of the EEPROM devices and have shown the invariance of data retention, programming speed, and endurance characteristics up to a cumulative ionizing radiation dose of 1 M Rad (Si). (Abstract shortened with permission of author.)... |
