The Effect of Multiple Interfaces on the Electrical Properties of MgO/Al₂O₃ Multilayer Gate Stacks on Si Grown by MBE

Abstract

High-κ and metal gate structures have been used to improve the performance of CMOS devices. By changing the materials and structures of the gate dielectric stacks, the flatband voltage (V FB ) and the leakage can be changed. We used bilayers and multilayer structures composed of MgO and Al 2 O 3 to verify their influence on the overall electrical properties. Films with an MgO bottom layer generally are found with less flatband voltage shift and lower leakage than with an Al 2 O 3 bottom layer. Also, the frequency dispersion and the interface state density (D it ) are higher for those with MgO bottom layers. MgO films thicker than 0.5 nm effectively shields the positive charges present in the Al 2 O 3 .