To characterize Ea and S DC AC electrical
To characterize Ea and γ·S, DC/AC electrical parameters will be determined from MIL standard measurements in a temperature range of −55 to +200°C. It is therefore necessary also to characterize the junction temperatures and hot points by infra-red or electrical method. The accelerated aging, representative of equipment mission profile, will provide time to failure TTF.
Characterization/modeling of immunity to natural radiations Wide bandgap semiconductor presents a significant technological breakthrough compared to silicon semiconductor. Main benefits of these materials are higher junction temperature, higher critical electrical field allowing higher breakdown voltages, lower thermal resistivity, excellent reverse recovery inducing lower switching losses and allowing higher switching frequencies. GaN transistors foreseen in high power switching application (DC-DC converters, boosters, …) shows better performance than Si or SiC transistors in terms of ratio “On resistance value/voltage breakdown”, which is the most important figure of merit for a power switch. Fig. 3 illustrates the efficiency ratio comparison between Si and GaN for power switching. We have proceeded to a detailed physical analysis of manufacturing processes of the GaN normally-off commercial used in power conversion. Considered GaN transistors were EPC 2019 (200V/10A) and GaN Systems GS66508P (650V/19A). The cross section analysis as shown by Fig. 4 enables to know about transistor\'s epitaxy. A fine analysis was made at the level of the active area. This analysis shows that active area (drain to source distance ~7μm for EPC and ~21μm for GaN Systems transistor) is made of a complex multiple set of AlGaN layers grown on a Si substrate. We have also proceeded to the identification of the constituent materials of the chip as well as analysis of the assembly of the chip into the package. This construction analysis has been used to build TCAD (Technology Computed Aided Design) transistor model as illustrated by Fig. 5. Measurements of the static electrical characteristics allowed calibrating and validating this adenosine deaminase TCAD model. Immunity to natural radiations will be simulated under TCAD (Sentaurus) in a temperature range of −55 to +200°C to quantify the fullness of reactions, locate theoretically sensitive areas and to identify trigger mechanisms. Unlike Si MOS transistor, some previous works regarding RF HEMT , ,  suggest that SEEs into AlGaN/GaN HEMTs are mainly due to displacement damage more than to ionization effects. However, todays TCAD radiation models cannot take into account displacement damage, which would be the reason why TCAD tools are not yet well-suited to these new technologies and finally the study may become unsuccessful. Fig. 6 shows the very first results obtained after a simulation of heavy ion impact. For the same LET (Linear Transfer Energy) of 1pC/μm but two different drain to source voltages VDS, we reproduce two levels of transients, one at VDS = 200V with IDSmax > 3 A (red curve) the other at VDS = 50V with IDSmax = 1.2 A. Fig. 7 shows the evolution of electron density along the time. At t0, an ElectroMagnetic field is created between the impacts by ionization points. At t1, we observe the beginning of avalanche phenomena. At t2, we observe holes injection near the drain. At t3, we may observe the SEB. Knowledge of the natural radiation environment for different applications (automotive, aeronautical and space) will then assess the Failure in Time (FIT) for a given application. Electrical characterization after campaigns under beams will allow the correlation of the measure with the modeling developed in the WP1. This WP will lead to enrich the predictive reliability model defined in WP1, determining the γ·S linked to natural radiations.
Characterization/modeling of EMC behavior (emission, immunity, signal integrity) and immunity to transients This WP will address proven technologies for functions commonly used in aeronautical or automotive ECUs. As illustrated by Fig. 8, an application demonstrator called ELECIS (Electronic board for Long term Electromagnetic Compatibility Issues Simulation) has been designed around a FPGA addressing different types of memory (flash, MRAM, DDR3), communicating thru an external ETHERNET bus and supporting analog functions as Analog to Digital Converter (ADC), reference voltage and supplied by linear and switched power supplies.