Electrical stress-induced charge carrier generation/trapping related degradation of HfAlO/SiO2 and HfO2/SiO2 gate dielectric stacks

Abstract

A comparative study on charge carrier generation/trapping and related degradation in HfAlO/SiO2 and HfO2/SiO2 stacks with identical equivalent-oxide-thickness (EOT) is presented during constant gate voltage stress of n-type metal-oxide-semiconductor capacitors. Compared to HfO2 devices, HfAlO devices with an equal EOT show better performances in memory and logic applications. On the contrary, at a given stress voltage, the threshold voltage degradation and stress-induced leakage current degradation in HfAlO samples are higher, indicating shorter device lifetime compared to the HfO2 samples of same EOT. In addition, the mechanism of charge trapping in the oxide as well as at the Si/SiO2 interface of both capacitors is investigated and a model is proposed. A similar generation kinetics was observed for stress-induced oxide trapped positive charges and interface states in either of the devices.