Determining constant voltage lifetimes for silicon nitride capacitors in a GaAs IC process by a step stress method

The lifetimes of metal-insulator-metal (MIM) capacitors are predicted from voltage step stress data. Capacitor areas of 400, 5625 and 11250 μm² are investigated. The reliability of capacitors subjected to a single or triple DC pulse prior to a breakdown voltage ramp test is predicted at use conditions (5 V). The method of maximum likelihood is employed in this analysis. With this approach, it is found that the effect of capacitor area on the linear field acceleration parameter, γ, is not statistically significant. Also, it is demonstrated that either a single or a triple DC pulse seriously reduces both the MTTF and γ. Further, the triple DC pulse can change the failure distribution from lognormal to Weibull. The data are also fitted to the reciprocal field model and the predicted failure times under use conditions are too large to be physically reasonable, favoring the linear field model. A graphical method is suggested for discerning between the lognormal and Weibull distributions.