System and methods for adaptive program-verify control in nand programming

A memory system comprising:

• a memory device;
• a controller in communication with the memory device and configured to control the memory device, wherein the controller is configured to:
• apply program pulses to the memory cells;
• apply a series of program-verify pulses to the memory cells to identify the memory cells having improper voltage thresholds short of the program-verify pulse levels;
• for the memory cells having the improper voltage thresholds, apply a non-zero bias to bit lines of the memory cells to program the memory cells, having the improper voltage thresholds, to proper voltage thresholds;
• and
• selectively determine which memory cells are first subject to both the program pulses and the program-verify pulses based on a programming speed of the memory cells.