Rustem G. Useinov

Microdose Induced Drain Leakage Effects in Power Trench MOSFETs: Experiment and Modeling

We study experimentally and theoretically the micro-dose induced drain-source leakage current in the trench power MOSFETs under irradiation with high-LET heavy ions. We found experimentally that cumulative increase of leakage current occurs by means of stochastic spikes corresponding to a strike of single heavy ion into the MOSFET gate oxide. We simulate this effect with the proposed analytic model allowing to describe (including Monte Carlo methods) both the deterministic (cumulative dose) and stochastic (single event) aspects of the problem. Based on this model the survival probability assessment in space heavy ion environment with high LETs was proposed.

Simulation of Bipolar Transistor Degradation at Various Dose Rates and Electrical Modes for High Dose Conditions

Radiation response of bipolar devices irradiated under various electrical modes and dose rates at high doses has been studied. A nonlinear numerical model including ELDRS effects and electric field reduction at high doses has been developed and validated. Dose degradation of a bipolar transistors gain factor at different dose rates and electrical modes has been simulated and explained in a unified way, based on dependence of the charge yield in isolation oxides on dose rates and electric fields. It has been shown that at high doses one needs to use a nonlinear, self-consistent numerical approach, accounting for simultaneous suppression of the oxide electric field induced by trapped charge. Correspondingly, two types of degradation saturation have been revealed: (i) due to simultaneous thermal annealing, and (ii) due to total dose dependent electric field reduction in oxides. The former implies proportionality of the saturation dose and degradation level to dose rate, the latter permits dose rate independent saturation levels of degradation.

Multiple Cell Upset Cross-Section Uncertainty in Nanoscale Memories: Microdosimetric Approach

We found that the energy deposition fluctuations in the sensitive volumes may cause multiplicity scatters in the multiple cell upsets (MCU) in the nanoscale (with feature sizes less than 100 nm) memories. Microdosimetric model of the MCU cross- section dependence on LET is proposed. It was shown that ideally a staircase-shaped cross-section vs LET curve spreads due to energy-loss straggling into a quasi-linear dependence with a slope depending on the memory cell area, the cell critical energy and the efficiency of charge collection.

New Insight into Heavy Ion Induced SEGR: Impact of Charge Yield

In this work an experimental evidence of a crucial role of the charge yield in the heavy ion induced single-event gate rupture (SEGR) process in SiO2 is reported. The results of SEGR cross-sections and charge yield measurements are presented for different heavy ions with atomic number Z from 26 to 83. The dependence of breakdown voltage on deposited energy was derived taking statistical variations in the heavy ion deposited energy into account. It is shown that the SEGR breakdown voltage is a linear function of residual charge remaining after recombination in ion track.

Physical Mechanisms of Radiation Response in Thick Isolation Oxides for Different Temperatures and Dose Rates

Temperature behavior of the charge yield and degradation saturation due to the interface precursor depletion has been modeled and simulated. Competition between the time-dependent and true dose rate (ELDRS) effects has been simulated and discussed.

Kinetics of Radiation -Induced Optical Losses in Undoped Fiber for Different Temperatures: Experiment and Modeling

An analytical model of the radiation-induced optical absorption in undoped optical fiber has been developed, based on self-trapped holes light absorption. The model correctly describes the dependences obtained in our investigation of gamma-radiation induced fiber absorption for different temperatures in the 1450 ~ 1600 nm wavelength range.

Modeling of single event gate rupture in power MOSFETs under heavy ion irradiation

Destructive single event gate rupture (SEGR) occurring in the gate oxides of power MOSFETs under impact of heavy ions is studied and modeled. SEGR cross section of power MOSFET with 70 nm oxide thickness as function of gate voltage was measured for four types of heavy ions. A predictive formula for the SEGR cross section is derived and validated. This formula can be used as a predictive instrument for computation of survival probability in a given spectrum of heavy ions in space environments.