Plenary session

The role of material science in power electronics

S. Coffa
Robert Bosch GmbH, Reutlingen ­- Mobility Electronics Department, Power Semiconductors and Modules

In this talk the importance of new materials introduction in semiconductor processing is highlighted. In particular, cases in which materials science innovation have been combined with proper industrial exploration of the new materials properties will be discussed. As known, performances of power devices are of paramount importance in energy consumption reduction in many practical applications.  The roadmaps of modern power devices is driven by three major development pillars; a) novel elementary cell structure; b) advanced interconnects; c) use of different semiconductor materials (moving from Si to  SiC and GaN). Improvements in any of these pillars are strongly driven by new materials introduction. The focus of the presentation is to show how the introduction of  SiC and GaN with their superior electronic and thermal properties (and in spite of problems linked to defects and higher costs compared to Si) has revolutionized the field of power devices. Today semiconductor companies are heavily using SiC and GaN in the production of power devices. This has been made possible by the huge work of the material science community (improvement in crystal growth, epitaxy, defect reduction and screening, use of ion implantation on compound semiconductor, etc). Finally, it will be shown that the lower defect density, the larger availability, the possibility to use large area substrates and the overall reduction in costs achieved for SiC, is offering the possibility to use the material for other applications (SiC integrated photonics, quantum computing and others still to come)

Imaging the Properties of Atoms and Fields down to the Picometer Scale inside Materials and Devices

David A Muller
School of Applied Physics, Cornell University, USA; David.A.Muller@cornell.edu

With recent advances in detector technology and ptychographic phase-retrieval algorithms to unscramble multiple scattering, the resolution of the electron microscope is now limited only by the dose applied to the sample, and thermal vibrations of the atoms themselves.  At high doses, these approaches have allowed us to image the detailed vibrational envelopes of individual atom columns as well as locating individual interstitial atoms.  The three-dimensional nature of the reconstruction means surface relaxations can be distinguished from the bulk structure, and atomic-scale interface roughness and step edges inside devices can be resolved – including gate-all-around transistors and Josephson junctions. Even the location of all atoms in thin amorphous films now seems within reach. The reduced sensitivity to chromatic aberrations also makes these ptychographic-like approaches of interest for thick biological or polymer samples or operando liquid-cell experiments, where we have been able to demonstrate a fivefold improvement in dose efficiency over conventional cryo-EM.