Lifetime Extrapolation of PZT Capacitors

Abstract

We propose a new methodology for lifetime determination of PZT capacitors, based on accelerated tests performed at low voltages and high temperatures. We believe that such a methodology is the only way to characterize the relevant failure mechanism for Time-Dependent Dielectric Breakdown of PZT capacitors. The capacitors lifetime at operating conditions is found to exceed 20 years. PURPOSEOver the last few years, thin films of PbZr x Ti 1−x O 3 (PZT) have been the focus of extensive research for filtering and decoupling capacitor applications. The essential requirements for such applications include a high dielectric constant, low dissipation factor, low leakage current, and acceptable capacitor lifetime. Among these properties, the reliability and the comprehension of failure mechanisms have already been investigated [1-4], but we believe that this issue needs to be explored further. From our first Wafer Level Reliability (WLR) results, we identified two different degradation mechanisms, depending on the applied electrical field [5]. In this paper, we expose the statistical data representative of these two mechanisms and we propose a testing methodology which enables to characterize only the relevant mechanism for lifetime extrapolation. This methodology is based on cumulated temperature and voltage accelerations. Our reliability model, which describes the dielectric lifetime as a function of voltage and temperature, is discussed in the last section.

Characterization and reliability studies towards piezoelectrically actuated RF-MEMS switches

“…The high voltage model explains the breakdown by resistance degradation and thermal runaway. Applying a constant voltage stress from 30 to 36 V at 85°C, the Weibull shape parameter β is 1.3, which is much lower than the β measured at low voltages [102].…”

“…The low voltage model explains the breakdown by percolation theory. Applying a 12 V constant voltage stress from 125°C to 220°C, β is 3.7 over the whole temperature range [102]. At low voltage, a resistance restoration phenomenon is clearly detected before breakdown: the current decreases with time.…”

“…This thesis also treats the temperature extrapolation in chapter 7. The extrapolation result of the low voltage model fits both E model and √ E model well in [102].…”

“…The measured time to breakdown can be fitted well by the Arrhenius law [102]. Not much study of Arrhenius law in PZT reliability is found, and it deserves more research.…”

“…[102]. The observation is based on the measurements of PZT samples with 250 nm thickness and a Zr/Ti ratio of 52/48, using spin-on sol-gel processing [102,103].…”