A non-volatile MOSFET memory device based on mobile protons in SiO2 thin films

It is shown how mobile H+ ions can be generated thermally inside the oxide layer of Si/SiO2/Si structures. The technique involves only standard silico n processing steps: the non-volatile field effect transistor (NVFET) is bas ed on a standard MOSFET with thermally grown SiO2 capped with a poly-silico n layer. The capped thermal oxide receives an anneal at similar to 1100 deg rees C that enables the incorporation of the mobile protons into the gate o xide. The introduction of the protons is achieved by a subsequent 500-800 d egrees C anneal in a hydrogen-containing ambient, such as forming-gas (N-2 : H-2 95:5). The mobile protons are stable and entrapped inside the oxide l ayer, and unlike alkali ions, their space-charge distribution can be contro lled and rearranged at room temperature by an applied electric field. Using this principle, a standard metal-oxide-semiconductor (MOS) transistor can be converted into a non-volatile memory transistor that can be switched bet ween 'normally on' and 'normally off'. Switching speed, retention, enduranc e, and radiation tolerance data are presented showing that this non-volatil e memory technology can be competitive with existing Si-based nonvolatile m emory technologies such as the floating gate technologies (e.g. Flash memor y). (C) 1999 Published by Elsevier Science B.V. All rights reserved.