| 摘要 |
A group of memory cells is programmed respectively to their target states in parallel using a multiple-pass programming method in which the programming voltages in the multiple passes are correlated. Each programming pass employs a programming voltage in the form of a staircase pulse train with a common step size, and each successive pass has the staircase pulse train offset from that of the previous pass by a predetermined offset level. The predetermined offset level is less than the common step size and may be less than or equal to the predetermined offset level of the previous pass. Thus, the same programming resolution can be achieved over multiple passes using fewer programming pulses than conventional method where each successive pass uses a programming staircase pulse train with a finer step size. The multiple pass programming serves to tighten the distribution of the programmed thresholds while reducing the overall number of programming pulses.
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