String based erase inhibit

A method of operating a memory apparatus comprising a plurality of memory strings, each memory string of the plurality of memory strings comprising a plurality of memory cells arranged between a select gate drain (SGD) transistor at a drain-side end of a memory string and a select gate source (SGS) transistor at a source-side end of the memory string, the method comprising the steps of:

• performing, for the plurality of memory strings, one erase-verify iteration in an erase operation including determining whether at least one memory string of the plurality of memory strings passes an erase-verify test;
• and
• if the at least one memory string passes the erase-verify test:
• inhibiting the at least one memory string for erase including ramping up, to an erase voltage, of a voltage applied to a gate of a SGD transistor of the at least one memory string at a time before initiating ramp up, to the erase voltage, of a voltage applied to a bit line connected to a drain-side end of the at least one memory string;
• and
• performing a next erase-verify iteration in the erase operation for remaining memory strings of the plurality of memory strings other than the at least one memory string.

An apparatus comprising:

• means for determining whether at least one memory string of a plurality of memory strings passes an erase-verify test of a first erase-verify iteration in an erase operation;
• and
• means for ramping up, to an erase voltage, of a voltage applied to a gate of a SGD transistor of the at least one memory string if the at least one memory string passes the erase-verify test;
• means for performing a next erase-verify iteration in the erase operation for remaining memory strings of the plurality of memory strings other than the at least one memory string;
• and
• means for initiating ramp up of the voltage applied to the gate of the SGD transistor of the at least one memory string at a time before ramp up, to the erase voltage, of a voltage applied to a bit line connected to a drain-side end of the at least one memory string.