Double Shockley Stacking Fault Formation in Higher Doping Regions of PVT-Grown 4H-SiC Wafers

Due to the influence of facet, the dopant concentration is higher than that other region inside the boule during PVT grown 4H-SiC. A [0001] facet can be observed on top of the boule. The facet region is visible as an oval region of darker contrast indicating a higher doping concentration in c-plane wafers sliced from N-doped 4H-SiC boules. With the help of synchrotron white beam X-ray topography techniques, we have carried out detailed studies on the facet regions in 4H-SiC wafers from different boules. We observed the double Shockley stacking faults piling up insider the facet after the wafer has been subject to chemical mechanical polishing followed by high temperature heat treatment. The partials bonding the stacking faults are along the Peierls valley which is along <11-20> for 4H-SiC. The contrast of double Shockley stacking faults, which are formed by the gliding of two leading partial dislocations on adjacent basal planes, is found only inside the facet region. Our study indicates that the presence of scratch or the other surface source and a higher concentration of N doping within the facet gives rise to the double Shockley faults formation. Moreover, within the facet, the lower minority carrier lifetimes compare to the rest area of the wafer characterized by lifetime mapping measurements also indicates a high density of stacking faults.Due to the facet effect, the dopant concentration is higher than that other region inside the boule during PVT grown 4H-SiC. A [0001] facet can be observed on top of the boule. The facet region is visible as an oval region of darker contrast indicating a higher doping concentration in c-plane wafers sliced from N-doped 4H-SiC boules. With the help of synchrotron white beam X-ray topography techniques, we have carried out detailed studies on the facet regions in 4H-SiC wafers from different boules. We observed the double Shockley stacking faults piling up inside the facet after the wafer has been subject to chemical mechanical polishing followed by the high temperature heat treatment. The partials bonding the stacking faults are lying inside the Peierls valley which is along <11-20> for 4H-SiC. The contrast of double Shockley stacking faults, which are formed by the gliding of two leading partial dislocations on adjacent basal planes, is found only inside the facet region. Our study indicates that the presence of scratch or the other surface source and a higher concentration of N doping within the facet gives rise to the double Shockley faults formation. Moreover, within the facet, the lower minority carrier lifetimes compare to the rest area of the wafer characterized by lifetime mapping measurements also indicates a high density of stacking faults.