Radiation Effects on Oxynitride Gate Dtelectrics

Radiation effects on oxynitrides, SiOxNy, formed by a nitridation anneal of the thermally grown SiO2 layers in an ammonia-nitrogen ambient at lOOO°C are presented. An initial high positive charge trap density of 3 to 6x1011 charges/cm2 and low interface state density 2 to 4×1010 states/eV/cm2 are characteristics of the oxynitride films. The chemical composition using Auger Spectroscopy indicates nitrogen distribution throughout the oxynitride film with higher concentration near the surface and the interface. No mobile-ion contamination or charge injection under high field conditions have been observed. Under radiation, improvement in radiation sensitivity by a factor of 2 to 3 over thermal oxides and no increase in interface state density are shown up to a dose of 1×106 Rad (Si). A model for nitrogen incorporation near the interface satisfying positive charge traps is discussed.