A Study on Reliability and Failure Mechanism of T-Shaped Gate HEMTs

Takahide ISHIKAWA  Kenji HOSOGI  Masafumi KATSUMATA  Hiroyuki MINAMI  Yasuo MITSUI  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E77-A   No.1   pp.158-165
Publication Date: 1994/01/25
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Reliability)
Category: Failure Physics and Failure Analysis
T-Shaped gate HEMT,  von Mises stress,  recess depth,  stress concentration,  

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This paper describes the reliability on recess type T-shaped gate HEMTs and their major failure mechanism investigated by accelerated life tests and following failure analysis. In this study, high temperature storage tests with a DC bias condition have been conducted on three different recess depths of 100, 125, and 150 nm. The results have clarified that the shallow recess devices of under 125 nm depth have no degration in minimum noise figure Fmin or gain Ga characteristics, indicating that standard HEMT devices, whose recess depth is chosen to be far under 125 nm, possess a sufficient reliability level. However, the devices with deep recess of 150 nm have shown degradation in both Fmin and Ga. Precise failure analyses including SEM observation and von Mises stress simulation have firstly revealed that the main failure mode in deeply recessed T-shaped gate HEMTs is increase in gate electrode's parasitic resistance Rg, which is caused by separation of "head" and "stem" parts of the T-shaped gate electrode due to thermo-mechanical stress concentration.