Interface electric charge modelling and characterization with δ – distribution generator strings in thin SOI films

Today's SOI technologies are able to produce buried oxides with a thickness spectrum from 400 nm in the standard HTA SIMOX, down to tens of nm in Unibond technique. In the SOI structures, two oxide-semiconductor interfaces exist, with specific associated charges. Conventional models ignore the charges situated at the buried oxide-substrate interface, being focused just on the front and back channels conduction in the silicon film. All these fixed charges, classically expressed in e cm−2, are physically spread into a small volume that becomes significant in very thin films (nanofilms). This paper presents a new model of the flat-band voltage using δ–distribution generator strings. The model accuracy increases in the SOI nanofilms domain, accordingly with our theory and numerical simulations. On the other hand, an experimental setup is presented for the spreading parameters extraction, in the case of a HTA SIMOX wafer.