Effects of the Localization of the Charge in Nanocrystal Memory Cells

In this paper, we present a peculiar characteristic of nanocrystal (NC) memory (NCM) cells: The programming (P) windows measured in linear and subthreshold regions are different. A floating-gate Flash memory cell with a similar structure does not show the same behavior, and the P window (PW) is independent of the current level of the extrapolation, as expected. By performing 2-D TCAD simulations, we demonstrated that this characteristic of NCM cells is due to the localization of the charge into the NCs. We investigate the correlation between the difference of the PWs in linear and subthreshold regions and the number, width, and position of the NCs.