Electrical and Reliability Studies of “Wet ” Tunnel Oxides Grown on Silicon for Flash Memory Applications

In this paper, we report the electrical characteristics and reliability studies on tunnel oxides fabricated by "wet N₂O" oxidation of silicon in an ambient of water vapor and N₂O at a furnace temperature of 800 degC. Tunnel oxides that have an equivalent oxide thickness of 67 A are subjected to a constant-current stress (CCS) amount of -100 mA/cm² using a MOS capacitor to obtain information on stress-induced leakage current (SILC), interface, and bulk trap generation. The obtained results clearly demonstrate the superior performance features of the present tunnel oxides with reduced SILC, lower trap generation, minimum change in gate voltage, and higher charge-to-breakdown during CCS studies. X-ray photoelectron spectroscopy depth profile studies of the tunnel oxide interfaces have shown that the improved performance characteristics and reliability can be attributed to the incorporation of about 8.5% nitrogen at the oxide-silicon interface of the samples formed by the "wet N₂O" process that involves low-temperature oxidation and annealing at 800 degC.