FILCERA

Electrical energy is essential for the devices efficiency and safety, either in civilian or military applications. Prospects for very significant gains in terms of energetic efficiency, compactness, power and strength are highly expected for power electronic systems. Such systems evolution, requiring high or very high voltage (from few kV to a few decades of kV) and severe environments, is strongly related to the emergency of new power modules based on large gap semiconductors such as silicon carbide (SiC). However, challenges remain in order to improve significantly the stability of the power electronic modules under particular ranges of power densities and voltage, especially concerning their internal electrical insulation. For demanding applications, power modules use ceramic substrates. This substrate is the mechanical support of the semiconducting chips and metallic interconnections within the power system that will be used for electrical insulation and thermal conduction. The electric field enhancement at the triple junction between the ceramic, the metallic track borders and the insulating environment is usually a critical point in the hampering device performances and a limit to the voltage increase in the future systems. This project is dedicated to the preparation and optimisation of an original insulating ceramic substrate. Our project will offer an original solution that should overcome this limit and is based on a new concept of “field grading substrate”, by a surface modification of the properties at the triple junction point. The aim is to push the limits of the materials generally used as substrates in power electronics. The substrate that will be used as the base system is the aluminium nitride (AlN). The “Materials Science” strategy will first focus on doping the AlN powder in order to locally modify the electrical and thermal properties of the material used as a field grading solution. We will then adapt the system geometry, arrange the shape and co-sinter the AlN/AlN-modified using the innovative sintering method described as the Spark Plasma Sintering (SPS). We also aim to explore new technologies, in particular the Selective Laser Sintering (SLS) and Melting (SLM) processes. The project fits perfectly with the so-called thematic “Materials, Chemistry and Energy” of the ASTRID program. It is positioned at the forehead of the system maturation and development. We expect 30 months for this research project, that intends to prove the validity of our concept by the realisation of laboratory prototypes including aluminium nitride substrates used as “field grading” that will be metallised. We aim at demonstrating a minimum of 30% improvement for the breakdown voltage. Numerical modelling, engineering and conception of novel objects will be necessary for the success of the project. The group of scientists involved in this research project shows complementary skills and knowledge based on materials chemistry and physics. Experienced scientists from the LAPLACE and CIRIMAT laboratories, specialised in the synthesis of powders, shaping or sintering processes of ceramics, preparation and characterisation of materials and high voltage insulating systems will closely collaborate and this project should prove again how their complementary skills can be successfully used for the development of power electronic devices. Also, the rich local environment in terms of scientific equipment and mutualised platforms (PNF2, 3DPhi, PRIMES, and the French FERMaT Research Federation) will be highly favourable to the project realisation and should be, in a longer term, transferred to industrial uses.