Metal-Oxide-Semiconductor Structures with Two and Three-Region Gate Dielectric Containing Silicon Nanocrystals: Structural, Infrared and Electrical Properties

D. Mateos, A. Arias, N. Nedev, M. Curiel, V. Dzhurkov, E. Manolov, D. Nesheva, O. Contreras, B. Valdez, I. Bineva, O. Raymond, J.M. Siqueiros
Autonomous University of Baja California, MX

Keywords: Si nanocrystals, MOS, TEM, I-R, I-V, C-V, two step annealing

Summary:

MOS structures with two and three-region gate dielectrics containing Si nanocrystals are prepared and characterized by TEM, IR spectroscopy and electrical measurements. c Si/SiO2 containing Si NCs/SiO2/Al structures were obtained by high temperature annealing of SiO1.15 films deposited on n-type Si first in pure N2 and then in 90% N2 + 10% O2 atmospheres. The three-region MOS structures (c-Si/SiO2/SiO2-Si NCs/SiO2/Al) were fabricated by thermal oxidation of n-cSi, followed by the steps described above. TEM results proved the formation of two regions in the SiO1.15 films: the first one, far from the top surface exhibits Si nanocrystals (~ 3-4 nm), while the second one close to the top surface shows a uniform amorphous SiO2 phase. IR measurements indicate phase separation and formation of nanocrystals in a SiO2 matrix as well as complete oxidation of the excess Si in the top region. I-V measurements on two-region MOS structures showed that the top SiO2 has high quality dielectric properties. C-V measurements revealed that the density of states at the c-Si/SiO2-Si NCs interface is high. In contrast the three-region MOS structures display excellent C-V as well as I-V characteristics.