Constant-charge-injection programming for 10-MB/s multilevel AG-AND flash memories

Abstract

The demand for high-density, high-speed programming in flash memories has been increasing because their expanding applications in portable equipment such as digital still cameras and music players. A multilevel technique is one of the most effective approaches for improving memory density. But long cell programming time and precise control of the memory cell's threshold voltage (Vth) degrade its programming performance. To realize fast cell programming, we have developed a so-called assist-gate (AG)-AND-type flash cell, in which programming is performed by source side channel hot electron injection (SSI). In this paper, we developed a constant-charge-injection programming, which realizes fast precise control of Vth by suppressing the characteristic deviation. By utilizing proposed scheme, we achieved. 10.3-MB/s programming throughput in multilevel AG-AND flash memories.