O. Krüger, G. Schöne, A. Liero, J. Würfl, and G. Tränkle

Published in:

Lasers in Manufacturing 2005 (LIM), AT-Fachverlag GmbH, International WLT-Conference on Lasers in Manufacturing, Munich, Germany, vol. 3, pp. 663-667, ISBN 3-00-016402-2 (2005).

Abstract:

UV laser processing is used to drill micro holes in contact pads of high-power microwave transistor devices. The AlGaN/GaN transistor structures that require electrical contacts from the device’s front to the backside (microvias) are fabricated on silicon carbide substrates. Direct laser ablation is an alternative to the time-consuming lithographic processing in combination with dry etching of silicon carbide. A laser drilling process using nanosecond laser pulses has been developed and implemented into semiconductor device fabrication. The microvias were drilled from the back through ~400 µm thick semi-insulating silicon carbide wafers having functioning AlGaN/GaN transistors on their front. Subsequently, by metallization of the holes an electrical connection between the backside and the front was realized. The conical microvias have a mean diameter of ~100 µm and an aspect ratio of ~4. The center of the laser spot having a diameter of ~15 µm can be positioned with an accuracy of ± 1 µm with respect to existing transistor structures. The complete process flow from CAD layout data to laser processing is available. No degradation of DC and RF properties of the AlGaN/GaN high-power transistors was observed after laser processing.

Keywords:

laser drilling, microvias, silicon carbide, gallium nitride, transistor devices, semiconductor device fabrication

© by E. Beyer, F. Dausinger, A. Ostendorf and A. Otto, WLT, Bremen, Germany 2005.
The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.

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