Strong impact of slight trench direction misalignment from [11(2)over-bar0] on deep trench filling epitaxy for SiC super-junction devices

A trench filling epitaxial growth technique using hot-wall chemical vapor deposition with HCl gas has been developed for SiC super-junction (SJ) device fabrication. 2-6 kV class SJ devices require p/n column structures with depths of over 10 mu m. However, rapid trench closure before the trench backfilling process is complete makes these structures difficult to realize. Stripe trenches that were intentionally inclined within +/- 2 degrees on a surface plane towards the [11 (2) over bar0] direction were formed on an off-angled wafer, and the effects of trench direction misalignment from the off-direction were investigated. Slight trench direction misalignment was found to affect the tilt angle of the mesa top epi-layer strongly. Tilted growth on the mesa top reduced the filling rate at the trench bottom and caused void formation. When a wafer with high orientation-flat accuracy relative to the [11 (2) over bar0] direction was used, 25-mu m-deep trench backfilling was successfully demonstrated. (C) 2017 The Japan Society of Applied Physics