Fraunhofer IKTS: Better semiconductor substrates for power electronics

The aim of SiC crystal growth is to produce large and defect-free single crystals. Their quality depends on many parameters, e.g. the starting crystal, the temperature gradient during the growth process, the quality of the SiC raw material (powder), the evaporation rate of the SiC powder and also the design of the furnace interior of the crystal growing system. The SaxCrystalPower project focuses on these process parameters, their specific influence on the resulting SiC single crystal and the atomically resolved characterization of the resulting single crystal structures.

The production of high-purity SiC powder is central to SiC single crystal growth. This is extremely complex and has so far only been realized on a pilot plant scale. The powder is introduced into the furnace as a bulk material in order to deposit on the starting crystal at high temperatures of over 2000 °C. For the deposition of larger single crystals, more powder would have to be introduced into the furnace, which is only possible by compacting the powder particles due to the limited furnace volume.

In the SaxCrystalPower project, Fraunhofer IKTS is tackling these challenges and building on the institute’s extensive expertise in material development, powder characterization and sintering processes. In a first step, the influence of particle size and temperature on the formation of certain SiC polytypes will be investigated experimentally. The synthesized powders will then be examined with regard to their suitability for crystal growth and evaluated with regard to their possible densification by sintering.

In order to fundamentally evaluate the resulting qualities of the SiC single crystals and for their application as wide bandgap semiconductor substrates, a new high-resolution transmission electron microscope (TEM) is being set up at Fraunhofer IKTS. With this new and powerful nanoanalytics technique, the relationships between technology parameters during sintering and the formation of crystal defects can be investigated at atomic resolution. Another unique feature is that defect densities and defect types in the crystals can be characterized in 3D. This goes far beyond the usual crystallography of defects in 2D.

Further crystal growth conditions are to be investigated later in a new SiC single crystal growth system. To this end, the experimentally produced single crystals will be examined with regard to the dimensions achieved, the mass changes and the crystallographic properties and the system will be adapted accordingly. Various measurement methods will be combined to determine the type of defects and defect densities in the single crystals: starting with atomically resolved crystallographic examinations in the TEM, through chemical analyses to prove the purity or the precise setting of dopants. This work by Fraunhofer IKTS will make valuable contributions to correlations between the properties of SiC single crystals and the corresponding process parameters of the single crystal growing system. This lays the foundation for promising further developments in SiC single crystal development. With a new high-resolution TEM, the project will also create a research infrastructure at Fraunhofer IKTS that will significantly advance electronics and materials research as a whole.

Project name: Material/technology basis for SiC semiconductor production and processing to strengthen Saxony’s power electronics industry (SaxCrystalPower-FuE)
Project period: May 2024 – August 2027
Funding: ERDF
Project website: https://www.xn--europa-frdert-sachsen-oec.de/de/projekte/49566

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Further links

👉 www.ikts.fraunhofer.de 

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