Charge Storage Dynamics of Nanocrystal Flash Memory Elements:
Theory and Experiment
UNAM, Bilkent University, Physics Dept.
Flash memory devices have a global market share of about 50 Billion USD annually. Simpler production and higher performance is desirable for competitive manufacturing. Nanocrystal flash memory structures have multiple controllable design parameters that offer greater flexibility in design of memory devices. Understanding the charging and discharging dynamics of such memory elements is the key to optimize designs for a specific performance parameter. In this talk, a simple model that relates the charging and discharging currents to device parameters is presented. The model assumes storage of carriers in the quantized ground state of semiconductor nanocrystals. The charging and discharging of the nanocrystals are modeled through tunneling currents into and out of the nanocrystal layer. Effects of multiple parameters such as nanocrystals size and density, tunnel dielectric material properties and thickness, device geometry, substrate doping and gate properties on device performance can be understood through the model. Experimental data for Si nanocrystals in Silicon Nitride and Ge nanocrystals in Silicon Oxide are presented. Validity of the model is discussed for various cases. Results of the theoretical model are discussed for different nanocrystal and host-matrix properties. Predictions for higher performance device designs are presented.
Aykutlu Dâna received his BS degree from Electrical Engineering Department, Bilkent University in 1995. During his MS and PhD at Stanford Universtiy, he worked on a number of topics such as NEMS and MEMS devices for high sensitivity force detection and Cryogenic Force Microscopy applied to the characterization of single electronic states at semiconductor surfaces. Since 2003, he has been doing research on fabrication, characterization and device applications of semiconductor nanocrystals at Bilkent.
Dec. 13, 2006, 13:40, FENS G032