Effect of needle-like silicon nanosurface on the charge storage characteristics of silicon nanocrystals embedded within silicon nitride matrix

In this work, a metal-insulator-silicon (MIS) structure with a silicon nitride (SiNx) film, in which silicon nanocrystals (Si-NCs) are embedded as a gate insulator layer, was fabricated on needle-like silicon nanosurfaces. The MIS structure with Si-NCs embedded within the SiNx on the needle-like silicon nanosurface can be used to fabricate nonvolatile memory (NVM) devices with increased charge storage capacities compared to planar structures. In this study, as part of a strategy to overcome the technological and physical constraints involved in scaling down of NVM devices, the charge storage effects associated with the electronic properties of the MIS structure with a silicon substrate having a needle-like nanostructure were evaluated. For fabrication of the needle-like silicon nanosurfaces, polystyrene-block-polymethyl methacrylate (PS-d-PMMA) block copolymer composed of polystyrene (PS) and polymethyl methacrylate (PMMA) was used. The hysteresis width of the capacitance-voltage (C-V) characteristics of the MIS structures embedded with Si-NCs on the silicon substrates of the needle-like nanostructure was greater than that of the MIS structure embedded with Si-NCs fabricated on a planar structure. The interface trap density between the SiNx and uniform needle-like silicon nanosurface was also lower than that of the MIS structure fabricated on a planar structure. Therefore, NVM devices with increased charge storage capacity compared to those fabricated on a planar structure can be realized with a needle-like silicon nanosurface.