Wide range work function modulation of binary alloys for MOSFET application

This paper explores the characteristics of the binary alloys Ta-Pt and Ta-Ti for gate electrode application. With a proper composition of high and low work function metals, the work function of the metal alloys can be modulated from 4.16 eV to 5.05 eV continuously. The alloys show good thermal stability and inner chemical activity on both silicon dioxide and hafnium dioxide. Thermal stress generated from the alloy film increases interface state density and hence effective oxide charges. This problem can be greatly reduced with a W/Ta-Pt stack structure, where W acts as the main conducting metal and Ta-Pt acts as work function control metal. All of these properties make them suitable for use in all device applications.