In this work, time-dependent dielectric breakdown (TDDB) studies were performed on 6.5 nm, 9 nm, 15 nm, and 22 nm thick intrinsic SiO₂ films over a wide range of stress temperatures and electric fields both static and dynamic stress conditions. Results indicate that it is necessary to obtain data over a wide range of electric field to distinguish between the E and the 1/E models. Above 7 MV/cm both models fit well to the TDDB data. At lower electric fields, near operating conditions, oxide failure times vary exponentially with linear electric field and not with reciprocal field. The field acceleration parameter, gamma, is observed to be insensitive to temperature and has a value of approximately 1 decade/MV/cm for the range of oxide thicknesses studied. The thermal activation energy, E_a, ranged between 0.7 to 0.95 eV for electric fields below 9 MV/cm. Contrary to the earlier studies, these results seem to provide consistent electric field and temperature dependencies for TDDB stress conditions indicating that the oxide films processed from different technologies have similar properties. Bipolar stress tests were performed at electric fields as low as 6 MV/cm and frequencies ranged from 1 kHz to 100 kHz. The results show that the increased lifetime observed under bipolar stress conditions diminishes as the stress electric field and oxide thickness are reduced. Capacitance-voltage measurements reveal different charge trapping characteristics at high and low electric fields of both static and dynamic stress. The results provide evidence that the mechanism of oxide breakdown at low electric fields is different from that at high electric fields and these two mechanisms appear to be a function of electric field and oxide thickness.

Date Published: 12 September 1996
PDF: 11 pages
Proc. SPIE 2874, Microelectronic Manufacturing Yield, Reliability, and Failure Analysis II, (12 September 1996); doi: 10.1117/12.250820

Published in SPIE Proceedings Vol. 2874:
Microelectronic Manufacturing Yield, Reliability, and Failure Analysis II
Ali Keshavarzi; Sharad Prasad; Hans-Dieter Hartmann, Editor(s)