Abstract
Micropipe, a “killer” defect in SiC crystals, severely hampers the outstanding performance of SiC-based devices. In this paper, the etching behavior of micropipes in 4H-SiC and 6H-SiC wafers was studied using the molten KOH etching method. The spectra of 4H-SiC and 6H-SiC crystals containing micropipes were examined using Raman scattering. A new Raman peak accompanying micropipes located near −784 cm−1 was observed, which may have been induced by polymorphic transformation during the etching process in the area of micropipe etch pits. This feature may provide a new way to distinguish micropipes from other defects. In addition, the preferable etching conditions for distinguishing micropipes from threading screw dislocations (TSDs) was determined using laser confocal microscopy, scanning electron microscopy (SEM) and optical microscopy. Meanwhile, the micropipe etching pits were classified into two types based on their morphology and formation mechanism.
Highlights
The results demonstrate that under-corrosion is a suitable condition to form micropipe etch pits apart from threading screw dislocations (TSDs)
The results showed that the size of stably distributed in 7–9 μm, while the size of micropipeTSDs etchwas pitsstably was distribu distributed in 7–9 μm, while the size of micropipe etch pits was distributed in a larger larger range
We confirmed that the under-etched state was the best etching condition to distinguish micropipe etch pits from TSDs
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Bondokov et al used KOH steam to etch the (0001), (0001), (1120) and (1100) surfaces of SiC [28] This method needs to maintain the temperature at 700–1000 ◦ C under normal pressure. Mahajan et al utilized molten KOH to etch 6H n-type SiC single-crystal wafers [30]. Their results revealed that 500 ◦ C was the optimum temperature for the identification of micropipes (MPs), threading screw dislocations (TSDs), threading edge dislocations (TEDs) and basal plane dislocations (BPDs). We take advantage of the method of defect-preferred corrosion and molten KOH, successfully determining the etching condition to distinguish micropipe etch pits from TSD by etching 4H-SiC and 6H-SiC wafers for different amounts of time. The Raman performance of the micropipes are characterized, and we find a new Raman peak corresponding to micropipe etching pits
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