A Step Toward High Temperature Intelligent Power Modules Using 1.5kV SiC-BJT

International audienceLooking back to the development of inverters using SiC switches, it appears that SiC devices do not behave like their silicon counterparts. Their ability to operate at high temperature makes them attractive. Developing drivers suitable for 200˚C operation is not straightforward. In a perspective of high integration and large power density, it is wise to consider a monolithic integration of the driver parts for the sake of reliability. Silicon is not suitable for high ambient temperature; silicon-on-insulator offers better performances and presents industrial perspectives. The paper focuses on a SiC BJT driver: it processes logical orders from outside, drives adequately the BJT to turn it either on or off, monitors the turn-off and turn-on state of the device, and acts accordingly to prevent failure. SiC BJT imposes specific performances different from the well known ones of SiC JFET or MOSFET. The paper addresses a preliminary analysis of a SOI driver, anticipating the behavior of SiC-BJT and the change in behavior at high temperature. A discret driver as been design and fabricated. Elementary functionnal blocks have been validated, and a BJT conveter successfully operated at high temperature with high efficiency (η = 88%)

Pulse characterization of optically triggered SiC thyristors

International audienceThis paper deals with the pulse capabilities of 4H-SiC optically triggered thyristors. The device structure and the fabrication process are presented. The results of pulse characterizations are shown. Two types of current pulses were used, a short (pulse width of 10 μs) and a long (pulse width of 650 μs). Peak current densities of 17 kA.cm -2 and 4 kA.cm -2 were attained with short and long pulses respectively. The failures and degradation caused by these experiments are also shown in this paper

VTH subthreshold hysteresis technology and temperature dependence in commercial 4H-SiC MOSFETs

VTH subthreshold hysteresis measured in commercially available 4H-SiC MOSFET is more pronounced in trench than in planar ones. All planar devices from different manufacturers exhibit an inverse temperature dependence, with the hysteresis amplitude reducing as the temperature increases, whereas all trench devices from different manufacturers exhibit the opposite behaviour. A physical interpretation is proposed, based on experimental evidence, which demonstrates that temperature dependence of the VTH subthreshold hysteresis is related to the technology. The findings are relevant to the ongoing discussion on SiC bespoke validation standards development and contribute important new insight

Influence of the Masking Material and Geometry on the 4H-SiC RIE Etched Surface State

International audienceThe roughness of etched SiC surfaces must be minimized to obtain surfaces with a smooth aspect, avoiding micromasking artifacts originating from re-deposited particles during the etching process. Four varieties of masks, Al, Ni, Si and C, were deposited on the SiC surface by photolithographic process. The C structures were formed by annealing conversion of patterned thick photoresist. On these surfaces, dry etching was performed with an SF6/O2 plasma produced in a Reactive-Ion-Etching (RIE) reactor. Although a better aspect of the surface is obtained with Ni in comparison with Al mask, micromasking could also occur even with Ni if the mask design was not enough spaced out. With C and Si masks, which produce fluorides species with negative boiling temperature, smooth etched surface was obtained without micromasking, even for tight masks covering up to 90% of the SiC surface

Very low R/sub ON/ measured on 4H-SiC accu-MOSFET high power device

International audienceThis paper describes the I-V characteristics obtained from a 4H-SiC current limiting device. Some specific aspects of the specific on-resistance are discussed in simulation with the DESSIS ISE software. The device behaviors place it in the field of the best Implanted Channel MOSFET (IC-MOSFET) obtained in the literature. The best on-resistance measured is 13 mWcm 2 and the saturation current density reaches 900 Acm-2

OBIC measurements on 1.3 kV 6H-SiC bipolar diodes protected by Junction Lateral Extension

International audienceDue to its good electrical properties, mainly a high critical electric field and a large bandgap, silicon carbide has demonstrated potentialities for high power devices. We have designed and realised bipolar diodes to sustain a reverse voltage of about 1.3 kV. We present below the experimental breakdown voltage we achieved, and results of OBIC measurements

Les réseaux HVDC multi-terminaux : des défis multiples en génie électrique

National audienceLes systèmes électriques à très haute tension ont besoin d'être renforcés pour faciliter les échanges, maintenir la sécurité de fonctionnement, et raccorder des sources offshore. Certaines limites des réseaux alternatifs apparaissent alors. Les réseaux à courant continu haute tension (HVDC) multiterminaux peuvent être une alternative sous réserve de trouver des solutions aux barrières scientifiques et technologiquesexistantes. Les défis rencontrés sont au coeur du génie électrique, tant au niveau du matériau, du composant que du système. Cetarticle présente les principaux challenges à relever dans le domaine du génie électrique pour rendre possible l'exploitationfiable et sûre des réseaux HVDC.</p

Investigations on Ni-Ti-Al ohmic contacts obtained on p-type 4H-SiC

International audienceTransfer Length Method (TLM) based-structures were fabricated on 0.8 µm-thick epitaxial p-type Silicon Carbide (4H-SiC) layers. TLM mesas were defined by a 2 µm height using an SF 6 /O 2 reactive ion etching. TLM metal patterns were obtained by a lift-off procedure and electron beam deposition of Ni, Ti, Al and Pt. The patterned samples were annealed in Argon ambient at temperature ranging from 700°C up to 1000°C in a RTA furnace with a rapid heating ramp (up to 50°C/s) to complete the ohmic contact with the p-type SiC layer. Specific contact resistances were extracted from current/voltage measurements. To identify and follow the profile evolution of constituting element in the contacts and at the SiC/contact interface, the ohmic contacts were characterized using Secondary Ion Mass Spectrometry and Energy-Dispersive X-Ray spectroscopy before and after annealing. Ohmic contacts are obtained only for the Ni/Ti/Al and Ni/Ti/Al/Ni stacking layers and not for the Ti/Al/Ti/Ni and Ti/Al/Ti/Pt/Ni compositions. The specific contact resistance of Ni/Ti/Al/Ni stacking layers was observed to decrease from 2.7×10-4  .cm 2 at 700°C and 6.3×10-5 .cm 2 at 750°C to a minimal value of 1.5×10-5  .cm 2 at 800°C. Ohmic contacts are obtained with a reproducibility of 80 %

Effects of the laser beam size on the Optical Beam Induced Current (OBIC) for the study of Wide Band Gap (WBG) Semi-Conductor Devices

International audienceUV Laser is used to generate electron-hole pairs into Wide Band-Gap (WBG) semiconductors (SiC, GaN or Ga2O3). In the space charge region, the electric field drives the collected carriers and a current, so-called Optical Beam induced Current (OBIC), can be measured. The induced current is then directly related to the electrical field in the device. The OBIC, is a non-destructive technique, which has been previously successfully used to characterize High Voltage (HV) SiC devices [1, 2, 3, 4]. In order to fully benefit of the advantages provided by WBG semiconductors materials and to avoid premature breakdown of the high voltage devices, it is mandatory to have efficient peripheral protections such as a MESA, a JTE and JTE rings…The OBIC characterization can help the technology computer-aided design (TCAD) and the device process to optimize the efficiency of the periphery protection by analyzing the electric field distribution in the structure and especially at the junction periphery. In this talk, we will present an in-house testbench called micro-OBIC which will allow us to characterize HV PiN diodes with a micro-meter spatial resolution

V TH -Hysteresis and Interface States Characterisation in SiC Power MOSFETs with Planar and Trench Gate

International audienceThis paper contributes to investigations on the threshold-voltage (VTH) hysteresis in SiC power MOSFETs. Such effect is of relevance mainly for sub-threshold operation of the devices, but needs to be told apart from stress-related VTH-drift phenomena for technology maturity and reliability validation goals. Important differences exist in commercially available devices, particularly in relation to their gate technology, planar or trench, the latter also showing a marked temperature dependence of the hysteretic range. Based on the experimental characterization of the interface capacitance and charge, this paper puts forward a methodology for determining the types of traps affecting the various devices, with the aim of contributing a tool to assist driving of technological maturity in future generation devices. This paper also shows the potential of capacitance hysteresis measurement to the estimation of the distribution of interface