Characterization of heavy-ion, neutron and alpha particle-induced single-event transient pulse widths in advanced CMOS technologies

Abstract

Radiation-induced soft errors have become a key reliability issue for advanced semiconductor integrated circuits. With technology scaling, a large fraction of the observed soft failures are estimated to be related to latched single-event transients (SETs). Precise knowledge of the particle-induced transient pulse widths is important for determining error rates and for the design of hardening techniques to mitigate the effect of these transients.

This work presents a novel, autonomous pulse characterization circuit technique to measure the distribution of SET pulse widths for different radiation environments. The pulse characterization technique has been implemented in a range of CMOS technologies and test chips have been used to measure the distribution of SET pulse widths for heavy-ions, neutrons and alpha particles. The dissertation focuses on test results from IBM 130-nm and 90-nm bulk CMOS processes.

Heavy-ion SET measurements show a reduction in the threshold for a measurable SET from about 7 MeV-cm^2/mg for 130-nm to less than 2 MeV-cm^2/mg for 90-nm. SET pulse widths ranging from about hundred ps to over 1 ns were measured with heavy-ions in 130-nm and 90-nm processes and the pulse widths were found to increase when scaling from 130-nm to 90-nm. Technology scaling trends in SET pulse widths are explained based on experimental measurements and with the use of mixed-mode 3D-TCAD simulations. Reasons for long transients measured at low LETs in the 90-nm process, including the pulse broadening phenomenon, are examined. Results indicate that lower drive currents and reduced contact size to the well region are factors that lead to an increase in SET pulse widths with scaling. The presence of a parasitic bipolar charge collection in these processes, triggered by a well potential collapse effect, leads to wider transients. Simulation and experimental results illustrate that the use of larger contacts to the well region mitigates the well potential collapse and hence limits the SET pulse width.

The SET measurements reported in this work are the first-ever for neutrons and alpha particles and these results are important for predicting error rates for commercial terrestrial applications. Most neutron and alpha particle-induced SETs were found to be of the order of hundreds of picoseconds. Neutron and alpha failures-in-time (FIT) rates were found to be about 10^-5 FIT/inverter.