Effect of annealing and plasma precleaning on the electrical properties of N2O/SiH4 PECVD oxide as gate material in MOSFETs and CCDs

Abstract

Pure SiH4 and N2O involving low total inflow of gases and very high deposition rate (1400 Å/min) have been used to deposit PECVD oxide films in a parallel-plate reactor system. The effect of long time (40 min) low temperature (450°C) annealing in N2 ambient and plasma precleaning with different gases like Ar, N2, H2, O2, CF4/50% H2, on the electrical properties of the deposited films have been studied. Flatband voltage, Vfb, fixed oxide charge density, Df, interface trap level density, Dit, dielectric breakdown strength, hysterisis and bias stress stability are the properties studied. These properties are relevant to the gate oxide in MOSFETs and CCDs. The deposited films involving annealing and plasma precleaning have been found to show electrical properties comparable to those of dry thermal oxide films grown at 1100°C. In particular films deposited on H2 plasma precleaned wafers showed no bias stress instability. © 1993.