At Vanderbilt University there is a large research effort to study the underlying phenomena behind the effects of radiation on electronic devices and integrated circuits and to propose new solutions to increase the reliability of systems in space and other systems exposed to ionizing radiation.
Space systems rely on advanced microelectronic devices to perform functions including communication, control, imaging, and power conversion. While in space, the electronics are exposed to various forms of radiation, including electrons, protons, neutrons, and heavy ions. The radiation may produce effects in the electronics ranging from temporary loss of data to catastrophic failure. Device failure can occur because of long-term degradation caused by continuous exposure to the space-radiation environment (total dose effects) or as a result of transient, high-energy particle radiation (single event effects). The specific effects produced depend strongly on the specific technology and the radiation environment. Most space systems are designed conservatively using electronic parts that are at least several generations behind the current state of the art. However, the demand for higher performance and reduced time from design to flight has increased the pressure to use advanced technologies in space. The radiation response and long-term reliability of high-k alternative gate dielectrics will play a critical role in determining the viability of these new materials for use in future space applications.
Gate oxide reliability has been studied intensively; particularly as commercial gate oxide thickness has moved to the ultra-thin oxide regime, generally interpreted as sub 2-5 nm. A common type of reliability screen used to evaluate long-term device reliability is time dependent dielectric breakdown (TDDB) testing. TDDB accelerated life tests are used to construct reliability models that allow test a device under high stress in the lab and extrapolate the results to predict operational lifetime at use conditions.
Selected References:- J.A. Felix, M.R. Shaneyfelt, D.M. Fleetwood, T.L. Meisenheimer, J.R. Schwank, R.D. Schrimpf, P.E. Dodd, E.P. Gusev, and C. D Emic, Radiation-induced charge trapping in thin Al2O3/SiOxNy/Si(100) gate dielectric stacks, (in press) IEEE Trans. Nucl. Sci. (2003)
- J.A. Felix, D.M. Fleetwood, R.D. Schrimpf, J.G. Hong, G. Lucovsky, J.R. Schwank, and M.R. Shaneyfelt, Radiation response and reliability of hafnium-silicate capacitors, IEEE SISC Conference Proceedings. (2002).