Non-uniformities in ultra-thin oxide layers and their effect on the properties of tunnel MOS, MOM, and SOS devices

In an MOS, MOM, or SOS tunnel device there exists a very thin oxide layer at the interface. For such a layer by statistical considerations it is shown that a non-uniformity must exist in its thickness. The thickness distribution obtained by solving general equations for the rate of growth can be approximated either as a Poisson or as a Gaussian distribution. In either case an excess current exists across the layer and the effective tunneling thickness is less than the average thickness. Expressions are obtained for the effective tunneling thickness in terms of the average thickness of the oxide layer and its growth parameters.