Characterization of thin textured tunnel oxide prepared by thermal oxidation of thin polysilicon film on silicon

In this paper, the characteristics of thin textured tunnel oxide prepared by thermal oxidation of thin polysilicon film on Si substrate (TOPS) are studied. Because of the rapid diffusion of oxygen through the grain boundaries of the thin polysilicon film into the Si substrate and the enhanced oxidation rate at the grain boundaries, the oxidation rate of the TOPS sample is close to that of a normal oxide grown on a (111) Si substrate. Also, a textured Si/SiO₂ interface is obtained. The textured Si/SiO₂ interface results in localized high fields and causes a much higher electron injection rate. The optimum TOPS sample can be obtained by properly oxidizing the stacked α-Si film, independent of the substrate doping level. Also, the optimum TOPS sample exhibits a smaller electron trapping rate and a lower interface state generation rate when compared to the sample from a standard tunnel oxide process. These differences are attributed to a lower bulk electric field and a smaller injection area in the TOPS samples