Improvement of the current-voltage characteristics of a tunneling dielectric by adopting a Si3N4/SiO2/Si 3N4 multilayer for flash memory application

Abstract

Superior characteristics of an atomic-layer-deposited (ALD) Si3 N4 layer and Si3 N4 Si O2 Si3 N4 stacked layers as a tunneling gate dielectric for nonvolatile flash memory application are reported. Compared to a single layer of Si O2 electric field-sensitive characteristics were obtained by barrier profile engineering with a stacked layer; a lower leakage current at a low field and a higher leakage current at a high field. The stacked dielectric layer showed Fowler-Nordheim tunneling. However, the interfacial potential barrier profile was somewhat smoothed by chemical interaction between the individual layers. The interfacial trap density of this dielectric with an ALD Si3 N4 bottom layer was as low as 4× 10-10 cm2 eV near the mid-gap energy state, but the reoxidation process degraded the interface quality. The degradation mechanism was studied. © 2005 American Institute of Physics.