A selective verify scheme for achieving a 5-MB/s program rate in 3-bit/cell flash memories

The demand for high density and high-speed programming in flash memories has grown because of audio- and video- storage applications. A multilevel technique is the most effective approach to improving memory density, but it requires precise control of a memory cell's Vth that doesn't degrade programming performance. To enable this, we have developed a selective verify scheme for high-speed programming based on simultaneous multilevel programming. A selective verify scheme with asymmetrical cell operation and two-bank operation makes 5-MB/s programming throughput in 3-bit/cell flash memories attainable.