The analysis of 3-Level Charge Pumping in SOHOS Flash Memory

This paper discusses the 3-level charge pumping method in planar-type Silicon-Oxide-High-k-Oxid e-Silicon (SOHOS) and Silicon-Oxide-Nitride-Oxide-Silicon (SONOS) devices to find out the reason for degradation of data retention properties. In the CP thechnique, a pulse is applied to the gate of the MOSFET which alternately fills the traps withe electrons and holes, thereby causing a recombination current Icp to flow in the substrate. A 3-level charge pumping method may be used to determine not only interface trap densities but also capture cross sections as a function of trap energy. By applying this method, SOHOS device found to have a higher interface trap density than SONOS device. Therefore, degradation of data retention characteristics is attributed to the many interface trap sites.