Effects of Gas-Flow-Rate Ratio on Electrical Characteristics and Fowler-Nordheim Stress Resistance of Si Oxynitride Grown with Helicon-Wave-Excited N₂–Ar plasma

Abstract

The effects of the gas-flow-rate ratio on the electrical characteristics and the Fowler-Nordheim (FN) current stress resistance were investigated for Si oxynitride grown with helicon-wave excited (HWP) N2–Ar plasma. The flow-rate ratio of N2 [N2/(N2+Ar)] was varied from 100% (N2 only) to 60%. The X-ray photoelectron spectroscopic data (XPS) indicated that uniform Si oxynitride (probably Si2N2O) was formed through the entire film thickness when the N2 gas-flow-rate ratio was 100% (N2 only), though a small amount of Si suboxide was included. The capacitance–voltage (C–V) measurements revealed that the interface-state density was the lowest in this flow-rate ratio case, as the grown layer was postannealed at moderate temperatures (300–500°C). Fowler-Nordheim current injection was performed using the metal/Si-oxynitride/Si capacitors thus fabricated. The shift of the threshold voltage was the lowest for the sample grown without Ar mixing. It was smaller than that for the thermal Si oxide (SiO2) grown at 900°C. The results of FN current stress resistance experiments were explained in terms of the surface plasmon and avalanche breakdown models.