Wafer Bow Tuning with Stealth Laser Patterning for Vertical High Voltage Devices with Thick GaN Epitaxy on Sapphire Substrates
E. Brusaterra, E. Bahat Treidel, A. Külberg, F. Brunner, M. Wolf and O. Hilt
Published in:
Int. Conf. on Compound Semiconductor Manufacturing Technology (CS ManTech 2024), Tucson, USA, May 20-23, p. 4.1.4.2024 (2024).
Abstract:
In this work we present a systematic study on a novel method to reduce the very strong bow of 4-inch GaN-on-sapphire wafers with more than 15 μm thick epitaxy. Laser scribing of the epitaxial grown sapphire substrates results in monotonically increase of the wafers radius of curvature and a bow reduction from 300 μm to 50 μm with respect to the scribing pitch. Quasi-vertical pn-diodes are used to electrically-monitor changes to the epitaxial layers as a result of the substrate laser scribing process. The quasi-vertical pn-diodes manufactured in industrial process line on bow-reduced wafers have demonstrated median reverse bias blocking strength of ~1150 V and specific on-state resistance of ~1.5 mΩ·cm2. It was identified that the reverse bias current is mostly dominated by the pre-existing epitaxial defects and that the substrate laser scribing did not hinder the epitaxy performances.
Ferdinand-Braun-Institut gGmbH, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin, Germany
Keywords:
Vertical GaN devices, drift region, sapphire substrates, laser patterning, bow reduction
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