Modelling the degradation in the subthreshold characteristics of submicrometre LDD PMOSFETs under hot-carrier stressing

Abstract

Hot-carrier injection is observed increasingly to degrade the subthreshold characteristics with the scaling of LDD PMOSFETs. A physical subthreshold current model is applied to the fresh and hot-carrier-stressed submicrometre channel length devices. The channel length reduction is subsequently extracted. An empirical relationship is developed to characterize the degradation parameters as a function of stress time and channel length. With the use of this relationship, we can determine the device lifetime or predict the minimum allowable channel length (for a certain percentage of degradation and lifetime) that is applicable for a specific technology. The degradation of the PMOSFET subthreshold current, which imposes a major limit on device reliability for deep-submicron technology and low-power applications, is fully described by a physical analytical model.