Characterization of the aluminum-tantalum oxide-silicon dioxide-silicon charge storage (MTOS) device

A charge storage transistor is described which has several advantages as a non-volatile memory element over the MNOS (metal-silicon nitride-silicon dioxide-silicon) transistor. This device uses tantalum dioxide to replace silicon nitride as the second dielectric, resulting in an MTOS (metal-tantalum oxide-silicon dioxide-silicon) transistor. The obvious advantages of tantalum oxide are that its dielectric constant is larger than that of silicon nitride and that it has been widely used in the production of thin film capacitors, thereby making available a substantial amount of materials technology. The important characteristics of tantalum oxide and MTOS structures have been studied as they relate to the storage of interface charge, and results which will be presented show the potential advantages of MTOS transistors in applications as memory elements.