X-ray topographic study of defects in Si-based multilayer epitaxial power devices

Abstract

Silicon based multilayered epitaxial structures are currently the main material for large-scale commercial fabrication of generally used power semiconductor devices such as fast recovery epitaxial diodes (FRED), isolate gate bipolar transistor (IGBT), power MOSFETs etc.Defects in silicon based multilayer epitaxial structures used as the initial material for power epitaxial-diffusion devices have been studied by X-ray topography techniques. We show that the dislocation nets with nonuniform distribution of dislocations both over thickness and layer square in the form of dense rows (dislocation walls) or slip bands were principal defects in the initial epitaxial layers and have influenced the electrical characteristics of power devices.The X-ray methods used in the work allow revealing and identifying growth and process defects in device structures, studying their distributions, analyzing their mutual interactions and obtaining valuable information on the nature and evolution of the defects during device structure fabrication processes. This information allowed us to optimize the choice of initial materials and processes aiming to reduce the content of critical electrically active structural defects in the crystals that can influence the parameters of fabricated semiconductor devices; we also increased process yield and tangibly improved semiconductor device operation reliability in severe conditions and emergency modes.