Investigation of Retention Characteristics Caused by Charge Loss for Charge Trap NAND Flash Memory

Abstract

In this paper, we investigate the retention characteristics cause by loss of trapped charges in charge-trap NAND flash memory. We fabricated silicon-oxide-nitride-oxide-silicon (SONOS) flash memory devices having different widths and lengths for setting up a more accurate retention model. For higher accuracy in the measurement results, we have set up a fast-response measurement scheme to have a closer look at the retention characteristics, using a waveform generator and a fast-measurement unit. Drain current can be measurement immediately after a program operation with a mu s-level resolution. Transient analysis on the retention characteristics over a very short time period is performed along with the long-time measurement results. As the result, a more succinct set of clues for understanding the initial charge loss and the charge redistribution are provided.