Scanning electron and polarization microscopy study of the variability and character of hollow macro-defects in silicon carbide wafers

Abstract

Polarization microscopy is a suitable tool for studying strain in appropriately cut SiC single crystals. The outline shape examined by electron microscopy and the induced interference pattern observed by polarization microscopy were both used to study the variation and character of macro-defects present in SiC wafers. While voids are usually in a relaxed state, hollow-core dislocations are characterized by large interference halos up to ∼100 µm in diameter. Conoscopy, i.e. evaluation of the interference pattern created by inserting an Amici Bertrand lens, is used to examine these optical phenomena in more detail and gain additional knowledge on the inclination of wafers cut towards the c-axis. The discrepancy between the simulated and observed interference patterns for (0001)-SiC strongly indicates that pipes are not pure screw dislocations, as commonly thought, but have an edge component.

Keywords:

• silicon carbide
• hollow defects
• stress-induced birefringence

Acknowledgments

This work was supported by the Deutsche Forschungsgemeinschaft (DFG) through Ni299/12-1. The authors would like to thank Dr. Th. Wenzel and Dr. N. Peranio (University Tübingen) for valuable discussion and help during the simulation phase.