Silicon carbide single crystals have become widely used as substrates for power electronic devices like diodes and electronic switches. Today, 4inch and 6inch wafer diameters are commercially available which are processed from vapor grown crystals. The state of the art physical vapor transport method may be called mature. Nevertheless, low defect density and uniform doping are still topics which can be further improved by current research and development of more sophisticated processes and process control. The aim of the paper is to review the physical vapor transport growth method as applied today. Special emphasis will be put on currently less advanced in situ growth monitoring tools based on 2D and 3D X-ray imaging that could be a tool for production monitoring. These techniques allow a precise determination of the crystal and source material evolution. Another topic will be the processing of highly conductive p-type 4H-SiC which is of particular interest for power electronic switches
In‐situ 3D computed tomography (CT) view into the hot growth cell during bulk crystallization of SiC at 2200°C. Colors indicate the evolution of SiC powder consumption (bottom) and SiC crystal growth (top).
2D and 3D in-situ X-ray visualization was applied to study the behavior of the SiC source material during PVT growth under various growth conditions. Experiments were carried out in two growth chambers for the growth of 3 inch and 4 inch crystals. Growth parameters were varied in the gas room in terms of axial temperature and inert gas pressure. The study addresses the stability of the SiC source material surface. It is shown that a higher inert gas pressure (e.g. 25 mbar) inhibits an unintentional upward evolution of the SiC feedstock that interferes with the crystal growth interface. The latter is related to a suppression of a pronounced recrystallization inside the SiC source. For a low inert gas pressure (e.g. 10 mbar) it is concluded that the axial temperature gradient inside the source material needs to be decreased to less than ca. 10 K/cm.
We developed a solution growth process related to the combination of the Vertical Bridgman and Vertical Gradient Freeze in a metal free Si-C melt at growth temperatures of 2300 °C. For this procedure we present a detailed description of the growth process and discuss the influence of different growth parameters on the surface morphology and growth rate. So far, we managed to grow SiC layers with a thickness up to 300 μm. The characterization of the crystal morphology was carried out using SEM images and the metal concentration was estimated using SIMS.
A solution growth process combined of vertical Bridgman and vertical gradient freeze in a metal free Si-C melt at growth temperatures of 2300°C is developed. The influence of the growth parameters for different growth steps and of the surface polarity of the seed is investigated. The layers are evaluated by Raman spectroscopy, scanning electron microscopy and optical profilometry. The growth of high quality SiC layers with a diameter of 30 mm and a layer thickness up to 200 µm is achieved.
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