Non-volatile memory with erase verify skip

Abstract

A non-volatile storage apparatus is configured to perform erase verify during an erase process in order to account for differences in erase speed. In order to reduce the time used to perform the erase process (which includes the erase verify), the erase verify operation is skipped for certain memory cells based on a system parameter. For example, when erasing a block of memory cells, a series of erase voltage pulses are applied to the NAND strings in outer sub-blocks and inner sub-blocks of the block. Erase verify is performed between erase voltage pulses for NAND strings in the outer sub-blocks while skipping erase verify for NAND strings in the inner sub-blocks. Performing erase verify between erase voltage pulses for NAND strings in the inner sub-blocks is started at a predetermined number of erase voltage pulses after the NAND strings in the outer sub-blocks successfully erase verify.