Sandisk Technologies Inc.

Sandisk Technoloiges LLC

Xiaochen Zhu

Lito De La Rama

Jiahui Yuan

Xiang Yang

Jiacen Guo

Yi Song

Yihang Liu

Feng Gao

Anubhav Khandelwal

Sarath Chandran Puthenthermadam

Abu Naser Zainuddin

Heguang Li

Vishwanath Basavaegowda Shanthakumar

Jie Liu

Suanbin Loh

Yuanyuan Wu

Jimmy Yeh

Norman Lay

A duration of a program pulse used to program non-volatile memory cells such as NAND may be increased responsive to a programming failure using a shorter duration program pulse. The duration of at least one program pulse may be increased for at least one group of memory cells in response to a failure to program a group using a default program pulse duration. The group that experiences the increased duration program pulse may be the same group for which the program operation failed using the shorter program pulse or may be a different group than the group for which the program operation failed using the shorter program pulse.

Program pulse duration increase for NAND program failure

A rotatable transmission electron microscope (TEM) grid holder includes first and second legs orthogonally positioned with respect to each other. Each clamp holder leg is configured to be received within a hole in a main stage supporting the rotatable TEM grid holder. When the first leg of the clamp holder is affixed within the main stage, the sample has a first orientation with respect to the FIB, and when second leg of the clamp holder is affixed within the main stage, the sample has a second orientation with respect to the FIB, rotated 90° relative to the first orientation. The sample may be rotated back and forth between the first and second orientations multiple times as needed to produce a sample which may be clearly imaged by the TEM system, substantially free of curtaining effects.

Rotatable TEM grid holder for improved FIB thinning process

A non-volatile memory system detects a memory operation failure. In response to the memory operation failure, the system determines whether adjusting an overdrive voltage applied to a word line avoids the memory operation failure. If adjusting the overdrive voltage applied to the word line avoids the memory operation failure, then future memory operations are performed by applying the adjusted overdrive voltage to the word line.

Non-volatile memory with smart control of overdrive voltage

Technology is disclosed herein for early erase termination as a counter-measure for erase disturb. Multiple erase blocks of NAND memory cells are erased in parallel during an erase procedure. Erasing multiple erase blocks in parallel can place considerable strain on the circuitry that generates the erase voltage. If there is significant leakage current in one of the erase blocks the magnitude of the erase voltage for all of the erase blocks may drop. The erase blocks are tested sequentially for leakage current during the first erase loop while the erase voltage is applied to only the erase block under test. If any erase block fails the leakage current test that erase block is removed from the erase procedure. One or more additional erase loops are then performed with only those erase blocks that passed the leakage current test simultaneously receiving an erase voltage, thereby preventing erase disturb with early termination.

NAND early erase termination based on leakage current test

A non-volatile memory system separately performs a memory operation for multiple sub-blocks of a block in order from previously determined slowest sub-block of the block to a previously determined faster sub-block of the block. As a slower sub-block is more likely to fail, this order of is more likely to identify a failure earlier in the process thereby saving time and reducing potential for a disturb. In some embodiments, the proposed order of operation can be used in conjunction with a programming process that concurrently programs blocks in multiple planes using completion of programming of a fastest plane to a data state as a trigger to test for program failure of other planes to the data state.

Non-volatile memory with optimized operation sequence

A non-volatile memory system limits the amount of programming for a first type of group of non-volatile memory cells based on a first parameter such that a maximum number of programming pulses applied to the first type of group of non-volatile memory cells to program to the last data state after the first type of group of non-volatile memory cells completed programming to the other data states is X programming pulses. The non-volatile memory system limits the amount of programming for a second type of group of the non-volatile memory cells based on a second parameter such that a maximum number of programming pulses applied to the second type of group of non-volatile memory cells to program to the last data state after the second type of group of non-volatile memory cells completed programming to the other data states is Y programming pulses.

Non-volatile memory with zoned control for limiting programming for different groups of non-volatile memory cells

An erase process for a group of non-volatile memory cells comprises applying doses of erasing to the group and performing erase verify between pairs of successive doses of erasing. The time needed to complete the erase process can be reduced by optimizing the order of performing erase verify. For example, erase verify can be performed by separately performing erase verify for multiple portions of the group in order from previously determined slowest erasing portion of the group to previously determined fastest erasing portion of the group, and aborting the performing of erase verify prior to completion of erase verify for all of the portions of the group in response to a number erase errors exceeding a limit.

Non-volatile memory with optimized erase verify sequence

To prevent loss of data due to a word line to memory hole short (or another defect), it is proposed to perform an erase process for a plurality of memory cells, detect that a subset of the plurality of memory cells are slow to erase, and prevent successfully programming for at least some of the memory cells that are slow to erase. This technique uses the erase process to predict future word line to memory hole shorts and prevent programming of memory cells predicted to have a future word line to memory hole short so no data will be lost when the short manifests.

Non-volatile memory with short prevention

Technology is disclosed herein for a memory system that compensates for different programming speeds in two sets of memory cells when reading those two sets of memory cells. The memory system programs a group of the memory cells to one or more data states. In one aspect, the memory cells are not verified during programming. The group has a first set of memory cells that program at a first speed and a second set of memory cells that program at a second speed. The memory system reads the first set of the memory cells with a first set of read parameters and reads the second set of the memory cells with a second set of read parameters. The first set of read parameters are different from the second set of read parameters to compensate for the different programming speeds.

Memory cell group read with compensation for different programming speeds

An apparatus is provided that includes a word line coupled to a word line driver circuit, bit lines, a plurality of non-volatile memory cells each coupled to the word line and a corresponding one of the bit lines, and a control circuit coupled to the word line and the bit lines. The control circuit is configured to program the memory cells by causing the word line driver to apply a program pulse to the word line, and biasing each bit line to a corresponding bit line voltage that has a value that varies based on a distance between the word line driver and the corresponding bit line.

Variable bit line bias for nonvolatile memory

To save power during a read process, NAND strings of each sub-block of a block have independently controlled source side select lines connected to source side select gates and drain side select lines connected to drain side select gates so that NAND strings of unselected sub-blocks can float and not draw current. To prevent read disturb in NAND strings of unselected sub-blocks, after all word lines are raised to a pass gate voltage, unselected word lines nearby the selected word line are lowered to respective intermediate voltages while lowering the voltage on the selected word line in order to achieve a channel potential gradient in the floated NAND strings of the unselected sub-blocks that does not result in read disturb. Subsequently, the selected word line is raised to the appropriate read compare voltage so the selected memory cells can be sensed.

Non-volatile memory with engineered channel gradient

A memory apparatus and method of operation are provided. The apparatus includes memory cells connected to one of a plurality of word lines and arranged in strings and configured to retain a threshold voltage. A control means is coupled to the plurality of word lines and the strings. The control means is configured to apply a primary predetermined voltage to a primary location of the memory apparatus following an erase operation of the memory cells while simultaneously applying a secondary predetermined voltage being lower than the primary predetermined voltage to a secondary location of the memory apparatus and measuring a leak current at the primary location. The control means then determines the erase operation passed in response to the leak current measured not being greater than a predetermined leak threshold.

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Milpitas, CA, United States of America

Xiaochen Zhu