Pulse-agitated self-convergent programming for 4-bit per cell dual charge storage layer flash memory

A pulse-agitated (PA) self-convergent programming (SCP) scheme is proposed for 4-bit per cell vertically dual charge storage layer (DCSL) Flash memory operation in NOR-circuits. PA substrate hot electron injection (PASHEI) is used for programming, and hot hole injection (HHI) is used for erasing. Localized PASHEI enables separated data nodes, while clear electron energy modulation gives rise to accurate multi-level threshold voltage (Vth) control in the step-up potential wells of the DCSL devices. Excellent 4-bit cell reliability is maintained for the DCSL devices throughout the 105 programming/erasing (P/E) cycles, and inter-cell disturbances are suppressed.