Impact of uniaxial stress on silicon diodes and metal-oxide-semiconductor-field-effect-transistors under radiation

Uniaxial strained-silicon (Si) has emerged as a leading technique for enhancing transistor performance for sub-100 nm logic technology for use in commercial and consumer electronics. Traditionally, semiconductor chips for military and space applications are fabricated using expensive radiation hardened technology. There is significant interest in the radiation research community towards integrating commercial CMOS technology for use in radiation environments to reduce costs. Although radiation effects in deep-submicron MOSFETs have been studied extensively in recent years, the effects of mechanical stress on transients in advanced MOSFETs have not been understood fully. Since strained-Si technology is widely adopted to increase carrier mobility in the channel in commercial off-the-shelf (COTs) chips, it is important to understand the trade-offs between chip performance and radiation effects in strained-Si devices. This work investigates the effect of uniaixial stress on Si diodes and MOSFETs under radiation through controlled stress experiments and device simulation.;X-ray-induced charge trapping and mobility degradation are investigated on uniaxially stressed HfO2-based nMOSFETs. Uniaxial tensile and compressive stress in nMOSFETs decreases the amount of net positive charge trapping and reduces the threshold voltage shift. Our experimental results suggest that changes in bond lengths and angles in HfO2 and/or SiOx as function of mechanical stress can reduce trap activation energy in gate dielectrics. Drive current (electron mobility) degradation in nMOSFETs is characterized and explained after irradiating devices under stress.;Laser-induced current transients in uniaxially stressed silicon (Si) N+/P and P+/N diodes are studied. They are good representation of source and drain regions of MOSFETs. Uniaxial stress alters the shape of the current transient in diodes resulting from strain induced changes in carrier mobility. The Florida Object Oriented Device Simulator (FLOODS) is used to model and explain the mechanism of current transients in unstressed and stressed diodes. The correlation between the external mechanical stress results on large diodes and deep sub-micron MOSFETs (both n-type and p-type) with process induced stress is also investigated and explained. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)...