Electrical characterization of SiO2(Si) films as a medium for charge storage

At present, the nonvolatile memory devices based on different kinds of nanocrystals are intensively developed. The important problem for further progress is connected with the optimization of gate multilayer structure. The aim of this work is the investigation of the electrical properties of thin nanocomposite SiO2(Si) films as a medium for the charge storage. The silicon enriched SiOx films were deposited by plasma enhanced chemical vapor deposition (PE CVD) method. The film composition was controlled changing the ratio of the flows of reactive gases SiH4 and N2O in a vacuum chamber. Subsequent thermal annealing led to the phase separation in SiOx films with a formation of nanocomposite SiO2(Si) structure of Si nanocrystals in dielectric matrix. Capacity‐voltage and current‐voltage measurements of MIS structures with gate nanocomposite SiO2(Si) films allowed to optimize the technological conditions of the formation of MIS structures with good charge storage properties. The value and the sign of stored charge were determined from the shift of C‐V characteristics. Analysis of the C‐V characteristics of MIS structures with nanocomposite SiO2(Si) films used equivalent circuit with the capacity of nanocrystals connected in parallel to the capacity of dielectric. The decrease of capacity in the accumulation region caused by nanocrystals was observed. The mechanism of current transport through the SiO2(Si) films was analyzed. It is determined to occur by tunneling through the SiO2 layers between the Si nanocrystals. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)