S.A. Chevtchenko, M. Schulz, E. Bahat-Treidel, W. John, S. Freyer, P. Kurpas, J. Würfl

Published in:

Microelectron. Reliab., vol. 54, no. 9-10, pp. 2191-2195 (2014).

Abstract:

A comparison of reliability by means of mean-time-to-failure (MTTF) determined from three-temperature accelerated life time tests for two groups of AlGaN/GaN heterojunction field effect transistors is presented. The two groups differ by gate trench fabrication technology, namely by RF bias and power levels used for the reactive ion etching of gate trenches in a SiN_x layer. The extrapolated MTTF at T_channel = 150°C was found to be ∼2.6 × 10⁸ h and ∼2.6 × 10⁵ h for transistors with gate trenches etched using RF power/bias 30 W/100 V and 15 W/30 V, respectively. The experimental results are explained based on the outcomes of simulations performed using Silvaco-"Atlas" 2D semiconductor device simulator. The simulations revealed higher electric field at the corner of the gate on drain side and increased electron concentration in the vicinity of the gate for the group of transistors processed with lowered RF power/bias. We conclude that the higher electric field and electron density increase transistors degradation rate.

Keywords:

AlGaN/GaN; HFET; Reliability; MTTF; Reactive ion etching (RIE); Gate technology

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