Effects of Dot Size and its Distribution on Electron Number Control in Metal-Oxide-Semiconductor-Field-Effect-Transistor Memories Based on Silicon Nanocrystal Floating Dots

Effects of dot size and dot size distribution on electron number control in silicon floating dot memories at room temperature are investigated by numerical calculation. When the dot size is sufficiently small and the size distribution is negligible, the number of electrons in the dot is precisely controlled by the Coulomb blockade and the electron number shows a staircase feature as a function of gate voltage. As the dot size increases and the size distribution increases, the staircase feature disappears due to the averaging effects. It is found that, to obtain a distinct staircase feature, the size distribution should be less than 7% for the 8-nm-diameter dot size and 12% for the 3-nm-diameter dot. These results provide good guidelines for setting device parameters for fabricating silicon floating dotmemories.