The Investigation of Fluorine Effects on Charge Trapping and Interface State Generation in Mos Structures

Abstract

ABSTRACTThe bulk and interface charge trapping phenomena of fluorinated oxides have been studied by various electronic measurements. Fluorine is introduced into dry oxides by low energy (25kev) implantation followed by a 1000°C N2 ambient anneal to remove physical damage. Both the flat band and the mid gap voltage shifts of such MOS devices are measured during avalanche electron injection. We have developed techniques to separate effects due to interface state generation from bulk trapping effects. The bulk electron traps in the fluorinated oxides have a different cross section from the known water-related traps in conventional oxides. The generation of fast and slow interface states for different dosages of fluorine implantation is discussed based on Q-V and C-V measurements. The fast interface donor states, generated during avalanche injection, are charged at flat band but discharged at mid gap and beyond. An optimum dosage of fluorine implantation is found to suppress the so called turn-around effect during avalanche injection due to the formation of slow donor states. Finally, injection under high temperature (120°C-150°C) anneals out most of these donor states.