A. Sanseverino

An improved model for extraction of strongly spatial dependent lifetimes with the AC lifetime profiling technique

In this work, we present an improvement of the extraction method for the AC lifetime profiling technique using a more accurate evaluation of the abscissa x where the lifetime is measured. By this model, a very good extraction of strongly variable lifetime profiles is obtained.

Power converters for future LHC experiments

The paper describes power switching converters suitable for possible power supply distribution networks for the upgraded detectors at the High Luminosity LHC collider. The proposed topologies have been selected by considering their tolerance to the highly hostile environment where the converters will operate as well as their limited electromagnetic noise emission. The analysis focuses on the description of the power supplies for noble liquid calorimeters, such as the Atlas LAr calorimeters, though several outcomes of this research can be applied to other detectors of the future LHC experiments. Experimental results carried on demonstrators are provided.

Experimental and numerical investigation about SEB/SEGR of power MOSFET

We present a 3-D simulation analysis related to an experimental study which clarifies the role played by the parasitic BJT activation on the interaction between generated charge and electric field during ion impact in SEB/SEGR of power MOSFET. This activation is caused by the movement of the holes deposited during the ion impact and gives rise to a huge amount of charge that is sustained by avalanche multiplication. During SEGR phenomena this generated charge interact with the high electric field that is formed underneath the gate oxide thus causing damages to it. During SEB phenomena the generated charge causes a double injection phenomenon to take place that induces an electrical instability and, then, the MOSFET destruction.

Determination of energy levels of recombination centers in low-doped Si layers by temperature dependence of recombination lifetime

Abstract The recombination lifetime dependence on temperature and injection level is largely due to the actual position of the recombination centers in the bandgap. However in the literature few data have been presented concerning the energy levels of the recombination centers in “good” low-doped silicon. In this paper an experimental evaluation of the energy position and the spatial distribution of the different recombination centers in low-doped N -type Si samples is made, from the temperature dependence of lifetime, by using a differential measurement technique. Results show that the energy levels of the most relevant recombination centers detected in such samples are far from being “deep”, but rather quite “shallow”, explaining the large variation on lifetime with temperature and injection found experimentally.

Developments on DC/DC converters for the LHC experiment upgrades

Prototypes of DC/DC power and Point of Load (PoL) converters were designed and built with the aim of satisfying the foreseen working parameters of the High Luminosity (HL) LHC experiments, using both Silicon (Si) MOSFETs and/or more recent devices substantiated of better power performance, like Silicon Carbide (SiC) and Gallium Nitride (GaN) transistors. Optimization of their design, based on the comparison between the simulated and measured thermal, electrical and mechanical performance, is in progress, and many improvements with respect to the previous versions are under implementation. We discuss in this paper the results of the last modifications. In addition, many tens of discrete component samples, chosen among the devices commercially available in the three different technologies (Si, SiC and GaN), were electrically characterized and tested under γ-rays, neutron, proton and heavy ion radiation, also using a combined run method. We have also planned to test some commercial DC/DCs under the extreme conditions of radiation and magnetic field expected in the upgrades of the LHC experiments. Here we show the first results on few samples.

Reliability oriented design of power supplies for high energy physics applications

Abstract The paper describes the design of switching converters suitable for power supply application in the LHC proton accelerator, in operation since 2010 at the European Organization for Nuclear Research (CERN) in Geneva (Switzerland). Experiments running at LHC must reliably operate in a harsh environment, due to radiation, high magnetic fields, and stringent thermal constraints. The followed approach takes into account the very tight reliability requirements during all the design stages, from the choice of circuit topologies and radiation hard power components, to the thermal layout and material optimization. Results carried out on prototypes are reported.

Heavy-Ion Induced Single Event Gate Damage in Medium Voltage Power MOSFETs

Starting from a physical model of the electric field that develops in the gate oxide during heavy-ion irradiation, we have experimentally and numerically investigated the single event gate damage observed in medium voltage power MOSFETs. Simulation results reveal that the total electric field reached during the heavy-ion impact is close to the one that is known to trigger the formation of latent damages during electro-static discharge (ESD) experiments.

Analysis of Heavy Ion Irradiation Induced Thermal Damage in SiC Schottky Diodes

A study is presented aimed at describing phenomena involved in Single Event Burnout induced by heavy ion irradiation in SiC Schottky diodes. On the basis of experimental data obtained for 79Br irradiation at different energies, electro-thermal FEM is used to demonstrate that the failure is caused by a strong local increase of the semiconductor temperature. With respect to previous studies the temperature dependent thermal material properties were added. The critical ion energy calculated by this model is in agreement with literature experimental results. The substrate doping dependence of the SEE robustness was analyzed, proving the effectiveness of the developed model for device technological improvements.

High Frequency Capacitive behavior of field stop trench gate IGBTs operating in Short Circuit

A wide experimental characterization about the input capacitance of Field Stop Trench Gate IGBTs is presented. It was achieved thanks to a novel experimental set-up which allows us to measure the input capacitance in the active region where the device operate during the Short Circuit (SC). The experimental results have been interpreted with the help of FEM simulations which confirm that negative capacitance is correlated with the accumulation of holes at the interface between N- IGBT base and gate oxide.

Thermal damage in SiC Schottky diodes induced by SE heavy ions

Abstract The failure of SiC Schottky diodes due to the impact of high energy heavy ions is investigated by means of electro-thermal and thermal finite element simulations. In particular, 3D ATLAS simulation of a small portion of the diode structure is used for computing the dissipated power density, which is subsequently used as input for the thermal COMSOL simulation of the complete system including chip and packaging. Results show that, as a consequence of the ion penetrating through the device, the temperature at the Schottky barrier becomes bigger than the SiC melting point for a time large enough to cause permanent damages to the SiC lattice. Simulation results are in good agreement with experiments presented in the literature.