A method of detecting, by a nonvolatile memory system, a defective memory cell block from among memory cell blocks, includes performing, after performing an erase operation, a read operation on at least some memory cells included in a target memory cell block based on an off-cell detection voltage that is different from a read reference voltage that distinguishes an off-cell on which no data is written from an on-cell on which data is written; counting a number of hard off-cells having a higher threshold voltage than the off-cell detection voltage from among the memory cells based on a result of performing the read operation; and identifying whether the target memory cell block is a defective memory cell block based on the number of counted hard off-cells.

A method for performing an operation in a memory device is provided. The method includes the following steps. An erasing operation is performed on one selected word line of the memory device to ensure that a plurality of first cells to be programed and a plurality of second cells to be erased connected to the selected word line have threshold voltages lower than a first predetermined level. A programming operation is performed on the selected word line, such that the first cells are suffered a first program bias and the second cells are suffered a second program bias which is lower than the first program bias.

Disclosed in some examples are systems, methods, memory devices, and machine readable mediums for a fast secure data destruction for NAND memory devices that renders data in a memory cell unreadable. Instead of going through all the erase phases, the memory device may remove sensitive data by performing only the pre-programming phase of the erase process. Thus, the NAND doesn't perform the second and third phases of the erase process. This is much faster and results in data that cannot be reconstructed. In some examples, because the erase pulse is not actually applied and because this is simply a programming operation, data may be rendered unreadable at a per-page level rather than a per-block level as in traditional erases.

A memory cell of a memory cell array includes a well region, a first doped region, a second doped region, a first gate structure, and a storage structure. The first doped region and the second doped region are formed in the well region. The first gate structure is formed over a first surface between the first doped region and the second doped region. The storage structure is formed over a second surface and the second surface is between the first surface and the second doped region. The storage structure is covered on a portion of the first gate structure, the second surface and an isolation structure.

A post over-erase correction (POEC) method with an auto-adjusting verification mechanism and a leakage degree detection function detects g.sub.m degradation or leakage degree of flash cells before or after entering the POEC process. When a preset condition is satisfied, the auto-adjusting verification mechanism of the POEC is switched on to further reduce leakage current. After cycling, the POEC repairs Vt of over-erased cells to a higher level to solve leakage issues. The erase shot count increases due to slower erase speeds after cycling. Therefore, the cycling degree of flash cells is detected by observing the shot number that the erase operation used. When the leakage phenomenon becomes serious, the bit line (BL) leakage current, amount of repaired BLs, and over-erase correction (OEC) shot number will increase during the OEC procedure. Therefore, the leakage degree of flash cells can be detected by inspecting the above data.

A memory device, and a method of operating the memory device, includes a memory block configured to include a plurality of memory cells that are stacked to be spaced apart from each other on a substrate and to include word lines coupled to the plurality of memory cells, and bit lines and a source line coupled to both ends of strings including the plurality of memory cells, and peripheral circuits configured to perform an erase operation on the memory block, wherein the peripheral circuits are configured to perform the erase operation on the plurality of memory cells included in the memory block, and thereafter perform a defect detection operation on memory cells selected from among the plurality of memory cells depending on sizes of the plurality of memory cells.

A block erase method for a flash memory is provided. The block erase method is to perform block erase on a block with a predetermined block size. The block erase method includes: performing an erase verification on bytes byte-by-byte in the block when performing the block erase; checking an erase step of the byte when the byte does not pass the erase verification; when the erase step of the byte exceeds a predetermined threshold value, performing the block erase with a partitioned block smaller than the predetermined block size, and returning to an erase verification stage to perform the erase verification; and when the erase step of the bytes does not exceed the predetermined threshold value, continuing to perform the block erase with the predetermined block size, and returning to the erasure verification stage to continue to perform the erase verification.

An erase voltage compensation mechanism for group erase mode with bit line leakage detection comprises performing a block erase operation by applying an erase voltage. Continue block erasing until bit line leakage is detected upon which the erase voltage is latched and over-erase correction is performed. A compensation voltage value is calculated by finding the difference between an upper bound of a threshold voltage distribution and an erase verify point when the bit line leakage was detected. The latched erase voltage is increased by the compensation voltage to create a compensated voltage. A group erase operation is performed and the group address is incremented by 1 and the compensated voltage value is loaded. Then the group erase operation is performed on the next group. The address is incremented, the compensated voltage is loaded, and the group erase operation is performed until the group is the last group.

A memory apparatus and method of operation is provided. The apparatus includes a block of memory cells each connected to one of a plurality of word lines and arranged in strings and configured to retain a threshold voltage. A control circuit couples to the word lines and the strings determines a program lower tail voltage of a distribution of the threshold voltage following a first program pulse. The control circuit calculates a second program voltage of a second program pulse based on the program lower tail voltage and applies the second program pulse to each of selected ones of the plurality of word lines associated with the memory cells to program the memory cells such that the distribution of the threshold voltage of the memory cells have a desired program lower tail voltage without further program pulses.

Some embodiments include apparatus and methods using access lines, first memory cells coupled to an access line of the access lines, and a control unit including circuitry. The control unit is configured to apply a first voltage to the access line; check first threshold voltages of the first memory cells after applying the first voltage; obtain offset information based on a determination that at least one of the first threshold voltages is greater than a selected voltage; generate a second voltage, the second voltage being a function of the first voltage and the offset information; and apply the second voltage to one of the access lines during an operation of storing information in second memory cells.