Sandisk Technologies Inc.

Sandisk Corporation

Alex Mak

Jian Feng Chen

Johann Alsmeier

Man Lung Mui

Seungpil Lee

Yingda Dong

Yan Li

Tien-Chien Kuo

Jun Wan

Xiying Costa

Jeffrey W Lutze

Chris Avila

Gautam Ashok Dusija

Loc Tu

Long C Pham

Masaaki Higashitani

Deepanshu Dutta

Sergey Anatolievich Gorobets

Steven Theodore Sprouse

A non-volatile storage system is disclosed that includes non-volatile memory cells designed for high endurance and lower retention than other non-volatile memory cells.

High endurance non-volatile storage

An erase operation for a 3D stacked memory device assigns storage elements to groups according to an expected erase speed. The storage elements are then erased according to their group to provide a more uniform erase depth and a tighter erase distribution. In one approach, the control gate voltages are set differently for the different groups to slow down the storage elements which are expected to have a faster programming speed. An erase or inhibit status can be set for all groups together. In another approach, the control gate voltages are common for the different groups but an erase or inhibit status is set for each group separately.

Group word line erase and erase-verify methods for 3D non-volatile memory

An erase process for a 3D stacked memory device allows a portion of a block of memory cells to be erased. In one approach, in a U-shaped NAND string configuration, memory cells in the drain- or source-side columns are erased. In another approach, such as in a U-shaped or a straight NAND string configuration, memory cells in a portion of a column of memory cells are erased, and a dummy memory cell is provided between the erased and non-erased memory cells. A dummy memory cell can be on either side (e.g., above and below) of an erase memory cell, or on either side of a non-erased memory cell. A dummy memory cell is ineligible to store user data, but prevents a downshift in the threshold voltage of an erased memory cell from changing the threshold voltage of a non-erased memory cell, due to capacitive coupling.

Selective word line erase in 3D non-volatile memory

When data from a portion of a three dimensional NAND memory array is determined to be uncorrectable by Error Correction Code (ECC), a determination is made as to whether data is uncorrectable by ECC throughout some unit that is larger than the portion. If modified read conditions provide ECC correctable data, the modified read conditions are recorded for subsequent reads of the larger unit.

Adaptive operation of three dimensional memory

Portions of data stored in a three dimensional memory array are selected based on their locations for calculation of redundancy data. Locations are selected so that no two portions in a set of portions for a given calculation are likely to become uncorrectable at the same time. Selected portions may be separated by at least one word line and separated by at least one string in a block.

Selection of data for redundancy calculation in three dimensional nonvolatile memory

An erase operation for a 3D stacked memory device assigned storage elements to groups according to an expected erase speed. The storage elements are then erased according to their group to provide a more uniform erase depth and a tighter erase distribution. In one approach, the control gate voltages are set differently for the different groups to slow down the storage elements which are expected to have a faster programming speed. An erase or inhibit status can be set for all groups together. In another approach, the control gate voltages are common for the different groups but an erase or inhibit status is set for each group separately.

Non-volatile storage devices and techniques for operating non-volatile storage are described herein. One embodiment includes accessing 'n' pages of data to be programmed into a group of non-volatile storage elements. The 'n' pages are mapped to a data state for each of the non-volatile storage elements based on a coding scheme that evenly distributes read errors across the &#x201c;n&#x201d; pages of data. Each of the non-volatile storage elements in the group are programmed to a threshold voltage range based on the data states to which the plurality of pages have been mapped. The programming may include programming the &#x201c;n&#x201d; pages simultaneously. In one embodiment, mapping the plurality of pages is based on a coding scheme that distributes a significant failure mode (for example, program disturb errors) to a first of the pages and a significant failure mode (for example, data retention errors) to a second of the pages.

Data coding for improved ECC efficiency

Memory die are provided with programmable chip enable circuitry to allow particular memory die to be disabled after packaging and/or programmable chip address circuitry to allow particular memory die to be readdressed after being packaged. In a multi-chip memory package, a memory die that fails package-level testing can be disabled and isolated from the memory package by a programmable circuit that overrides the master chip enable signal received from the controller or host device. To provide a continuous address range, one or more of the non-defective memory die can be readdressed using another programmable circuit that replaces the unique chip address provided by the pad bonding. Memory chips can also be also be readdressed after packaging independently of detecting a failed memory die.

Programmable chip enable and chip address in semiconductor memory

A memory system, comprising an array of storage elements divided into logical blocks and pages within said logical blocks and a managing circuit is provided. The managing circuit is in communication with said array of storage elements and performs programming and reading operations. The programming operations include programming a plurality of multi-state storage data. The reading operations include defining an retention margin between adjacent data thresholds, determining whether bits are present in a portion of the data retention margin, and if the number of bits in the portion of retention margin exceeds a threshold, generating an error.

Retention margin program verification

Data verification in a memory device using a portion of a data retention margin is provided. A bit count is read from the region to determine whether errors will result in the memory. A read in one or more retention margin portions is performed after the normal program verify sequence and if the number of bits in these regions is more than a pre-set the memory will fail verify status. A method of verifying data in a memory device includes the steps of: defining an retention margin between adjacent data thresholds; programming the memory device with data; determining whether bits are present in the data retention margin; and if the number of bits in the retention margin exceeds a threshold, generating an error.

Memory die are provided with programmable chip enable circuitry to allow particular memory die to be disabled after packaging and/or programmable chip address circuitry to allow particular memory die to be readdressed after being packaged. In a multi-chip memory package, a memory die that fails package-level testing can be disabled and isolated from the memory package by a programmable circuit that overrides the master chip enable signal received from the controller or host device. To provide a continuous address range, one or more of the non-defective memory die can be re-addressed using another programmable circuit that replaces the unique chip address provided by the pad bonding. Memory chips can also be also be readdressed after packaging independently of detecting a failed memory die.

Growing community of inventors

Los Altos Hills, CA, United States of America

Alex Mak