Atomic scale investigations of high dielectric constant nanostructures
The material of choice for gate dielectrics has been silicon dioxide because of its excellent insulator properties, low defect densities, and its thermal stability. Yet, the use of ultrathin silicon oxide gate dielectrics below ~ 2 nm-thick is reaching fundamental limits due to serious operation and reliability problems, such as a high tunneling current. These problems can be avoided by either the replacement of the silicon oxide film with a thicker high dielectric constant () film or a stacked structure that involves multiple high- layers. Also, the recent development of powerful experimental and theoretical methods to characterize surfaces and interfaces with atomic scale resolution makes it possible to address precisely issues upon which further progress in reducing device size depends.
The proposed project will focus on studies of high dielectric constant thin film structures.16-18 The focus will be on hafnium oxide on silicon, to enable the fundamentals of the films of interest to be developed. Specifically, the goals will be to:
• develop a fundamental understanding of the atomic scale processes behind the deposition of high- structures on Si substrates, and
• study the atomic scale nature of the resulting interfaces.
It will include two undergraduate students, one on the modeling of high dielectric constant materials and one on the process – structure relationships of such stacked nanostructures.
16. Roy Chowdhuri A., D.-U. Jin, J. Rosado, C. G. Takoudis, “Strain and substoichiometry at the Si(100)/silicon dioxide interface,” Phys. Rev. B 67., 245305/1 (2003).
17. Roy Chowdhuri A. and C.G. Takoudis, Investigation of the aluminum oxide/Si(100) interface formed by chemical vapor deposition," Thin Solid Films 446, 155 (2004).
18. Deshpande A., R. Inman, G. Jursich, C.G. Takoudis, “Atomic Layer Deposition and Characterization of Hafnium Oxide Grown on Silicon from tetrakis(diethylamino)Hafnium and Water Vapor,” J. Vac. Sci. Technol. A, in press (2004).