Use of low temperature plasma methods for synthesis of epitaxial films and nanostructures: Application to management of III-V high power high frequency devices

It is recognized that performance of microwave and electro-optical devices, circuits and subsystems currently used in modern communication systems, are drastically impacted by thermal issues. Microwave Circuits generate large amount of heat that must be removed for proper functioning of the device to offer suitable power performance, reliability and safety. The present work aims to develop innovative thermal management solutions through thin films with good thermal and dielectric properties. In that study which aims to replace the SiO2 thin films generally used for the passivation of such à components, we focused on aluminium nitride material and NTC structures thanks to their thermal properties. Nevertheless, it is necessary to synthesize such thin films and nanostructure at low temperature (< 250 °C). In this presentation, we report on thick epitaxial aluminium nitride films by DC magnetron sputtering on AlGaN substrate at substrate temperature < 250°C [1, 2]. Moreover, thermal conductivity measurements were performed on all the substrates thanks to an original home made sensor, thermal conductivity as high as 250 W.m-1K-1 were obtained for the optimized AlN/Si structures. The results will be reported and discussed In order to improve further the thermal performances of AlN films, oriented nanostructures consisting of carbon nanotubes – nanowalls - nanowires were embedded into such aluminium nitride matrix. Results on the synthesis of the CNT by PECVD, their encapsulation on the AlN matrix using DC magnetron and HiPIMS techniques and the thermal properties of such structures will also be presented and discussed.

Abdou Djouadi is Professor of University of Nantes since 2002, he is doing his research in Institut des Matériaux Jean Rouxel of Nantes. He received his PhD in 1993 from University Paris XI (IEF). He worked eight years in ENSAM School of Engineer on the development of oxides and nitrides coatings and obtained his habilitation (HDR) in 2001 from University of Nancy. His current research interests include thin films and nanotubes synthesis by different plasma methods (DC and HiPIMS, PECVD, …) and their application for thermal management. He is mainly interested by the development and use of new thermal methods and sensors in order to measure the thermal properties at micrometric and nanometric scale and therefore ensure the thermal management of opto and microelectronic devices. Since 1990, Prof. A. Djouadi has intensively studied aluminium and boron nitride thin films by several plasma methods which he also used for the synthesis of nano-compounds, nanotubes or nanofibers. Professeur Djouadi and colleagues successfully synthesized well crystallised AlN films and even epitaxial AlN films on AlN buffer layer, AlGaN and epitaxial ZnO layer on AlN. Moreover, thanks to in situ diagnostics (OES, Mass spectrometry, …) they succeeded to synthesize such a difficult materials using HiPIMS. Prof. Djouadi published more than 145 papers in peer reviewed journals and participated to 150 conferences with up to 60 invited talks. He also supervised or co-supervied 33 PhD thesis works.

These researches were also in close connexion with industrial problems and in this frame Prof. Djouadi leaded several industrial contracts (BatsCap, ALCATEL-THALES, MHS, Béliers Associés, GLADU, Platit, PSA, …). He also leaded several European projects as CRAFT HOBS and KNIWOOD in connection with SME’s and TEMPUS MEDA program which was more academic. He was also a scientific responsible for Nantes University for the European project TIPS (2015-2018) which is dealing with thermal management in photonics and laser cascade (QCL) devices. He was the coordinator of ANR HIPPOPP project (2008-2010), ANR PNano NanothermIC (2010- 2012), ANR CREATIVEPI (2011-2012) and the scientific responsible for ANR Fichtre (2014- 2017) and ANR SALSA (2015-2018). He is now the scientific responsible for Nantes University and CNRS of the M-GIMS project dealing with multi-sensors embedded in cutting tool for grinding and turning applications. Prof. A. Djouadi was also the French representative of European COST Action MP0804 involving up to 40 countries in the field of HiPIMS technique. He was in charge of the Workgroup V, HiPIMS deposition in reactive mode.