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

Abstract

We compare charge carrier generation/trapping related degradation in control oxide (SiO2) and HfO2/SiO2 stack of an identical equivalent-oxide-thickness (EOT) during constant gate voltage stress of n-type metal-oxide-semiconductor (nMOS) capacitors. Irrespective of these two dielectrics, the kinetics of generation of both surface states and oxide-trapped positive charges are found to be similar. Our analysis shows that the positive oxide charge buildup during CVS is due to trapping of protons by the strained SiOSi bonds in either of the devices. We demonstrate that compared to SiO2 devices, HfO2 devices with an equal EOT better perform in CMOS logic applications. On the other hand, our results indicate that the control oxide is better in charge trapping memory devices. Furthermore, the lifetime of the control oxide devices is observed longer than that of HfO 2 devices at a given operating voltage. © 2010 Elsevier Ltd. All rights reserved.