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 progess is connected with the optimization of gate multilayer success. The aim of this work is the investigation of the electrical properties of thin nanocomposite SiO(2)(Si) films as a model for the charge storage. The silicon enriched SiO(x) films were deposited by plasma enhanced chemical vapor deposition (PE CVD) method. The film composition was controlled charging the ratio of the flows of reactive gases SiO(4) and N(2)O in a vaccum chamber. Subsequent thermal annealing let to the phase separation in SiO(x) films with a formation of nanocomposite SiO(2)(Si) structure of Si nanocrystals in dielectric matrix. Capacity-voltage and current-voltage measurements of MIS structures with gate nanocomposite SiO(2)(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 SiO(2)(Si) films used equivalent circuit with the capacityof nanocrystals connected in parallel to the capacity of dielectric. The decrease of capacity in the accumulation region caused by nanocrystals was observed. The mechaaism of current transport through the SiO(2)(Si) films was analyzed. It is determined to occur by tunneling through the SiO(2) layers between the Si nanocrystals. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim