Leif Scheick

Effects of Ion Species on SEB Failure Voltage of Power DMOSFET

This paper presents and explains test results showing the effect of ion species on the single event burnout (SEB) failure voltage using a SEB sensitive engineering power double diffused metal oxide silicon field effect transistor (DMOSFET). The analyses show the determining factor of tested SEB failure voltage is the ion species itself rather than test or beam conditions such as initial beam energy, surface linear energy transfer (LET), ion range, or ionized charge. Also, results from five test facilities and five test setups are compared to determine if there will be differences in test results when different test setups or different heavy ion accelerator facilities were used.

Charge removal from FGMOS floating gates

Radiation effects on floating-gate-metal-oxide-semiconductor (FGMOS) devices in the passive or quiescent mode are due to a combination of the removal of negative charge from the floating gate and the generation and trapping of positive charge in the gate oxide. The latter is subject to room temperature annealing but not the former. No difference was observed between the effects of trapped charge on transistors in 0 and 1 logic states. The amount of negative charge per unit dose that is removed from the floating gates by heavy ions is less than that removed by 6 MeV electrons, which at least partially explains the sublinear dependence on linear energy transfer.

GaN-based high temperature and radiation-hard electronics for harsh environments

We develop novel GaN-based high temperature and radiation-hard electronics to realize data acquisition electronics and transmitters suitable for operations in harsh planetary environments. In this paper, we discuss our research on AlGaN/GaN metal-oxide-semiconductor (MOS) transistors that are targeted for 500 °C operation and >2 Mrad radiation hardness. For the target device performance, we develop Schottky-free AlGaN/GaN MOS transistors, where a gate electrode is processed in a MOS layout using an Al2O3 gate dielectric layer. The AlGaN/GaN MOS transistors fabricated with the wide-bandgap gate oxide layer enable Schottky-free gate electrodes, resulting in a much reduced gate leakage current and an improved sub-threshold current than the current AlGaN/GaN field effect transistors. In this study, characterization of our AlGaN/GaN MOS transistors is carried out over the temperature range of 25°C to 500°C. The Ids- Vgs and Ids-Vds curves measured as a function of temperature show an excellent pinch-off behavior up to 450°C. Off-state degradation is not observed up to 400 °C, but it becomes measurable at 450 °C. The off-state current is increased at 500 °C due to the gate leakage current, and the AlGaN/GaN MOS HEMT does not get pinched-off completely. Radiation hardness testing of the AlGaN/GaN MOS transistors is performed using a 50 MeV 60Co gamma source to explore effects of TID (total ion dose). Excellent Ids-Vgs and Ids-Vds characteristics are measured even after exposures to a TID of 2Mrad. A slight decrease of saturation current (ΔIdss~3 mA/mm) is observed due to the 2Mrad irradiation.

Role of Process Variation in the Radiation Response of FGMOS Devices

UV erasure times are measured and used to determine the degree of process variation across the die of FGMOS memories. Analysis of data obtained following exposure to ionizing radiation separates SEU-like mechanisms that generate anomalous decreases in erasure time from the uniform effects of TID.

Single Event Transients (SETs) in the RH108 Operational Amplifier in Analog Circuits

The effects of various commercial power devices are presented. The devices have proved to be very fragile to single event effects, with some of the devices actually succumbing to catastrophic SEE with protons