Relation between breakdown mode and location in short-channel nMOSFETs and its impact on reliability specifications

A method to determine the breakdown position in short channel nMOSFETs is introduced. We find that soft breakdown occurs exclusively in the transistor channel, while the hardest circuit-killing breakdowns occur above the source and drain extension regions. Since these breakdowns make up only a small fraction of all breakdowns, a relaxation of the reliability specification is possible.

I. Introduction

Predicting the oxide reliability in circuit conditions has always been a challenging task because of the many extrapolations and assumptions involved in the procedure. The first problem arises when time-to-breakdown () results obtained at high-voltage stress conditions have to be extrapolated down to low device operation voltage. Many papers discuss the possible extrapolation laws and the underlying physical mechanism [1]–[3]. Although a reasonable consensus has been reached on the breakdown mechanism, accurate extrapolations in a wide voltage range remain a subject of discussion.