Multi-pulse programming cycle of non-volatile memory for enhanced de-trapping

摘要

When writing a multi-state non-volatile memory, a de-trapping operation is included in the programming cycle. To reduce the performance penalty of including a de-trapping operation, the programming cycle of a single series of increasing pulses alternating with verify operations is replaced with a cycle including a pulse from each of two or more staircases, where each staircase is for a corresponding subset of the data states. After the multiple pulses, but before the following verify, a de-trapping operation is inserted in the programming cycle.

主权项

1. In a non-volatile memory circuit having an array of non-volatile, multi-state memory cells, a method of performing a write operation on a plurality of memory cells formed along a first word line from a first state to one of a plurality of second states, the second states including a first subset of one or more memory states and a second subset of one or more memory states, where the threshold voltages of the states of the second subset are higher that the threshold voltages of the states of the first subset, the method comprising:
performing a sequence of one or more programming cycles, a cycle comprising:
applying a first programming pulse to the first word line while program inhibiting non-selected cells along the first word line, program inhibiting selected cells along the first word line to be programmed to a state of the second subset, and program enabling selected cells along the first word line to be programmed to a state of the first subset;subsequently applying a second programming pulse to the first word line while program inhibiting non-selected cells along the first word line, program inhibiting selected cells along the first word line to be programmed to a state of the first subset, and program enabling selected cells along the first word line to be programmed to a state of the second subset;subsequently performing a de-trap operation on the selected cells along the first word line of both subsets; andsubsequently performing a verify operation the selected cells along the first word line of both sets, wherein those of the cells that successfully verify are inhibited prior to performing the nest cycle of the sequence.