Influence of Beam Conditions and Energy for SEE Testing

Neutron test campaigns on silicon (Si) and silicon carbide (SiC) power MOSFETs and IGBTs were conducted at the TRIGA (Training, Research, Isotopes, General Atomics) Mark II (Pavia, Italy) nuclear reactor and ChipIr-ISIS Neutron and Muon Source (Didcot, U.K.) facility. About 2000 power transistors made by STMicroelectronics were tested in all the experiments. Tests with thermal and fast neutrons (up to about 10 MeV) at the TRIGA Mark II reactor showed that single-event burnout (SEB) failures only occurred at voltages close to the rated drain-source voltage. Thermal neutrons did not induce SEB, nor degradation in the electrical parameters of the devices. SEB failures during testing at ChipIr with ultra-fast neutrons (1-800 MeV) were evaluated in terms of failure in time (FIT) versus derating voltage curves according to the JEP151 procedure of the Joint Electron Device Engineering Council (JEDEC). These curves, even if scaled with die size and avalanche voltage, were strongly linked to the technological processes of the devices, although a common trend was observed that highlighted commonalities among the failures of different types of MOSFETs. In both experiments, we observed only SEB failures without single-event gate rupture (SEGR) during the tests. None of the power devices that survived the neutron tests were degraded in their electrical performances. A study of the worst-case bias condition (gate and/or drain) during irradiation was performed.

The gate oxide layer and parasitic bipolar junction transistor are inherent elements of vertical double-diffused power metal–oxide–semiconductor field-effect transistors (MOSFETs). Single-event gate rupture (SEGR) and single-event burnout (SEB) may be triggered by penetration of energetic ions through sensitive regions of such MOSFET devices when used in space environments. Based on the recombination mechanism in a heavily doped P+ buried layer and the higher breakdown voltage when using a thick oxide layer, a new structure for power MOSFETs that are irradiation hardened against SEGR and SEB was developed in this work, based on three typical characteristics: an N+ buried layer, a P+ buried layer, and a thick oxide above the neck. The results reveal that the safe operation region of such an N-channel power MOSFET in a single-event irradiation environment is enhanced by 300 % for a linear energy transfer value of 98 MeV cm2/mg. Such structures could be widely used when designing single-event irradiation-hardened power MOSFETs.

In recent years, a new type of problem has occurred in radiation-borne electronic systems, known as Single Event Upsets (SEU). Radiation hardened electronic components are to be used for nuclear power plants, defence equipments, satellites, etc due to various kinds of radiation particles in the space. Here, the main focus is to measure the phenomena of SEU by building our own microcontroller test board for the effects of protons on the electronic devices under different radiation levels. The SEU results from the level change of stored information due to photon radiation and temperature fluctuations in the space environment which are prevalent in the geosynchronous, cosmic rays, high energy explosion which are common during wartime. The impacts of SEU in all defense electronic systems which make use of bipolar memory (ROM/RAM/EEPROM/SRAM) devices are studied. In this paper, the radiation hardening test was carried out at three different levels (beam current and energy) and the measurements of SEU carried out are listed. The possible reasons for SEU are addressed. A simple effective and powerful test technique to measure the phenomenon of SEU is suggested, and the results are presented for the analysis and future reference.

Ground testing has shown that power MOSFETs are susceptible to burnout when irradiated with heavy ions and protons. Satellite data from the Cosmic Ray Upset Experiment (CRUX) demonstrate that single event burnouts (SEBs) on 100-volt and 200-volt power MOSFETs can and do occur in space. Few SEBs occurred on the 100-volt devices, all at L/sup 1/>3. The 200-volt devices experienced many SEBs at L<3 when drain-to-source voltage (V/sub D-S/) was greater than 85% of maximum rated voltage. CRUX flight lot devices were ground tested with protons. The SEB rates calculated with the cross-sections from the ground tests show close agreement with the measured rates.

Analysis techniques on a 90 nm deep trench capacitor have provided the physical evidence for a heavy ion induced single event gate rupture (SEGR). The trench capacitor is from a 90 nm bulk complementary metal oxide semiconductor technology and is used for the reduction of single event upsets. SEGR damaged trench oxides are identified via a voltage contrast technique using a focused ion beam. The focused ion beam was used to delayer and expose the deep trenches. A wet chemical etch was used to identify the location of the SEGR leakage path. The oxide rupture location was observed at the top of the deep trench capacitor.

Proton single event upset (SEU) cross sections and proton total dose hardness of commercially available MIPS R3000 microprocessors (CPU) and R3010 floating point units (FPU) were obtained by exposing these parts to 256 MeV protons from the linear accelerator (LINAC) at the Los Alamos Meson Physics Facility (LAMPF). Parts from several manufacturers were tested. The CPUs and FPUs were tested dynamically during radiation exposure with specially designed assembly language codes which exercised a subset of the available instructions. Cross sections derived from the SEU data were used to calculate expected upset rates for a 500-km, 60-degree inclination orbit during quiet solar conditions and during the August 4. 1972, King solar fire event modeled by J.H. Adams et al. (1981).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper gives and explains the simulation results of single-event burnout (SEB) hardening in a power metal-oxide semiconductor field-effect transistor U-Shape Metal Oxide Semiconductor Field Effect Transistor (trench-gate MOSFET). It includes p+ plug enlargement and adds a buffer layer that is between the epitaxial layer and substrate. These two hardening solutions are compared and the optimized structure that can prevent SEB is given. The single event gate-rupture (SEGR) threshold voltages in different linear energy transfers are also compared with SEB results. In addition, the simulation results show that the change of gate bias can influence the occurrence of SEGR, and the natural radiation environment at cryogenic temperatures is also considered.

The temperature dependence of single-event burnout (SEB) in n-channel power MOSFETs is investigated experimentally and analytically. Experimental data are presented which indicate that the SEB susceptibility of the power MOSFET decreases with increasing temperature. A previously reported analytical model that describes the SEB mechanism is updated to include temperature variations. This model is shown to agree with the experimental trends. >

The experimental results of single event burnout induced by heavy ions and 252Cf fission fragments in power MOSFET devices have been investigated. It is concluded that the characteristics of single event burnout induced by 252Cf fission fragments is consistent to that in heavy ions. The power MOSFET in the “turn-off" state is more susceptible to single event burnout than it is in the “turn-on" state. The thresholds of the drain-source voltage for single event burnout induced by 173 MeV bromine ions and 252Cf fission fragments are close to each other, and the burnout cross section is sensitive to variation of the drain-source voltage above the threshold of single event burnout. In addition, the current waveforms of single event burnouts induced by different sources are similar. Different power MOSFET devices may have different probabilities for the occurrence of single event burnout.

The effects of striking of ions on a low-voltage power MOSFET have been investigated in this work. Special emphasis has been given on the study of Single Event Gate Rupture (SEGR) event. The physics-based device simulation tools: Silvaco ATHENA and ATLAS are used for process and device simulations and characterize the electrical properties of a power MOSFET suitable for space applications.

Robustness and reliability review of Si and SiC FET devices for more-electric-aircraft applications

The results of recent Single Event Gate Rupture and Single Event Burnout testing on power MOSFETS are presented. The recent test data show a considerable drop in failure voltage in comparison to manufacturer data for device ratings over 130V. The effect of range is considered to account for this difference. The methods and practices for testing and data analyses that need to be used for adequate SEE testing of power MOSFETs are also presented. I. INTRODUCTION any space applications are demanding more power and higher voltages. Unfortunately, the technology behind high blocking voltages in discrete devices is susceptible to radiation effects. The large feature sizes and low-doped regions of silicon are the underlying liable areas of these devices to radiation. The application of power devices can be especially stressful when power or voltage requirements are demanding, or the mission environment is hostile. Most power solutions for design approaches in space employ the vertical power MOSFET, but these devices present limitations and trade challenges to projects that require high speed or very large power for high current applications. This work presents the results from various testing of power MOSFETs with rigorous test conditions. This study aims to refine the methodology for adequate hardness assurance of power MOSFETs for space missions.

Dissociative chemisorption of oxygen on Ir(110) as a function of surface coverage

The heavy-ion fluence required to induce Single-Event Gate Rupture (SEGR) in power MOSFETs is measured as a function of the drain bias, V/sub DS/, and as a function of the gate bias, V/sub GS/. These experiments reveal the abrupt nature of the SEGR-voltage threshold. In addition, the concepts of cross-section, threshold, and saturation in the SEGR phenomenon are introduced. This experimental technique provides a convenient method to quantify heavy-ion effects in power MOSFETs.

A detailed analysis of 2728 intensity modulated proton therapy (IMPT) fields that were clinically delivered to patients between 2007 and 2013 at Paul Scherrer Institute (PSI) was performed. The aim of this study was to analyze the results of patient specific dosimetric verifications and to assess possible correlation between the quality assurance (QA) results and specific field metrics. Dosimetric verifications were performed for every IMPT field prior to patient treatment. For every field, a steering file was generated containing all the treatment unit information necessary for treatment delivery: beam energy, beam angle, dose, size of air gap, nuclear interaction (NI) correction factor, number of range shifter plates, number of Bragg peaks (BPs) with their position and weight. This information was extracted and correlated to the results of dosimetric verification of each field which was a measurement of two orthogonal profiles using an orthogonal ionization chamber array in a movable water column. The data analysis has shown more than 94% of all verified plans were within defined clinical tolerances. The differences between measured and calculated dose depend critically on the number of BPs, total thickness of all range shifter plates inserted in the beam path, and maximal range. An increase of the dose difference was observed with smaller number of BPs (i.e., smaller tumor) and smaller ranges (i.e., superficial tumors). The results of the verification do not depend, however, on the prescribed dose, NI correction, or the size of the air gap. There is no dependency of the transversal and longitudinal spot position precision on the beam angle. The value of NI correction depends on the number of spots and number of range shifter plates. The presented study has shown that the verification method used at Centre for Proton Therapy at Paul Scherrer Institute is accurate and reproducible for performing patient specific QA. The results confirmed that the dose discrepancy is dependent on the size and location of the tumor.