Anomalous NMOSFET hot carrier degradation due to trapped positive charge in a DGO CMOS process

Abstract

It has been reported that MOSFET hot carrier (HC) performance is degraded by back-end-of-line (BEOL) processing steps such as interlayer dielectric film deposition, passivation, and H/sub 2/ annealing. These effects are associated with the incorporation of additional hydrogen at the Si-SiO/sub 2/ interface states to passivate dangling bonds. This paper focuses on an unusual (anomalous) I/sub Dsat/ HC degradation behavior seen on a (DGO) NMOSFET device that was determined to be caused by a dielectric (SiON) contact etch stop process step. This paper presents a novel NMOSFET HC degradation behavior model based on HC injected positive trapped charge that is spatially separated from the normal HC trapped electron charge. This paper shows that this charge separation and positive charge injection creates a secondary impact ionization site that is within the device channel and results in anomalous and accelerated I/sub Dsat/ HC degradation behavior.