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

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.