Pergamon Microelectron. Reliab., Vol. 36, No. 11/12, pp. 1643-1646, 1996 Copyright g~ 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0026-2714/96 $15.00 + .00 PII: S0026-2714(96)00164-3 ELECTRIC FIELD DEPENDENCE OF TDDB ACTIVATION ENERGY IN ULTRATHIN OXIDES E. VINCENT I"~, N. REVIL 1, C. PAPADAS I and G. GHIBAUDO 2 SGS-THOMSON Microelectronics, Central R&D, BP 16, 38921 Crolles, France 2 Lab. de Physique des Composants/t Semiconducteurs, BP 257, 38016 Grenoble, France Abstract: A study of the electric field dependence of the TDDB activation energy is presented for 12 nm down to 4.7 nm thin oxides. It is shown that the TDDB activation energy depends linearly on the stress electric field and that this behavior depends strongly on the oxide thickness. Moreover, a relationship between the TDDB activation energy attenuation per MV/cm and the oxide thickness has been found. As will be demonstrated, these results are of great importance for the rigorous estimation of the oxide lifetime of both present and future technologies. Copyright © 1996 Elsevier Science Ltd INTRODUCTION Oxide reliability becomes the major concern for quality in microelectronics as the critical dimensions scale down. In particular, in an industrial context, the oxide reliability has to be checked in order to qualify the technology, i.e. to guarantee the insulator properties during the whole operating lifetime of the product. Classically, oxide lifetime is estimated for the nominal biasing conditions and for various temperatures, after compiling degradation results obtained at accelerated stress conditions (electric field and/or temperature). However, this exploitation implies the use of an extrapolation model as follows: i) extrapolation at low electric field with a TDDB (Time Dependent Dielectric Breakdown) model ("E" [1] or "I/E" [2] model) and ii) extrapolation through the Arrhenius law at 125°C. In both cases, the knowledge of the TDDB activation energy is necessary for a valid extrapolation. For this reason, this paper focuses on the electric field dependence of the TDDB activation energy for very thin oxides, when using the "E" formulation as an extrapolation background. EXPERIMENTAL DETAILS The devices are pLgate oxide capacitors grown on n-substrate with oxide thickness t~ = 12 nm, 7 nm and 4.7 nm fabricated by the Centre Commun CNET/SGS-THOMSON Microelectronics (Crolles, France). Since the area of the capacitors is 10000 pm 2, this study addresses only the intrinsic oxide reliability. After having verified that the "E" model fits well the experimental data at high fields, TDDB experiments have been performed at different temperatures (from 25°C to 125°C) on more than 20 capacitors per experiment. For one temperature, two voltage stresses have been used, sufficiently far away from each other (corresponding to a difference of 2 to 3 decades in time to breakdown) in order to determine the acceleration factor with a greater precision. 36/tl/12-f 1643