Determining read voltages for reading memory

• US 9,286,993 B2
• Filed: 05/20/2014
• Issued: 03/15/2016
• Est. Priority Date: 03/13/2013
• Status: Expired due to Fees

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Inventors: Lasser, Menahem
• Primary Examiner(s): Nguyen, Viet Q
• Application Number:
  US14/282,967
• Publication Number:
  US 20140269050A1
• Time in Patent Office: 665 Days
• Field of Search: 365/185.24, 365/185.18, 365/185.22
• US Class Current: 1/1
• CPC Class Codes: G11C 11/5642 Sensing or reading circuits; Data output circuits
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: G11C 16/26 Sensing or reading circuits; Data output circuits
• CPC Class Codes: G11C 16/3418 Disturbance prevention or evaluation; Refreshing of disturbed memory data
• CPC Class Codes: G11C 16/3422 Circuits or methods to evaluate read or write disturbance in nonvolatile memory, without steps to mitigate the problem
• CPC Class Codes: G11C 16/3427 Circuits or methods to prevent or reduce disturbance of the state of a memory cell when neighbouring cells are read or written
• CPC Class Codes: G11C 2211/5646 Multilevel memory with flag bits, e.g. for showing that a "first page" of a word line is programmed but not a "second page"
• CPC Class Codes: G11C 29/021 in voltage or current generators
• CPC Class Codes: G11C 29/028 with adaption or trimming of parameters
• CPC Class Codes: G11C 29/42 using error correcting codes [ECC] or parity check

Abstract

A method of reading data at a data storage device that includes a non-volatile memory having a three-dimensional (3D) configuration includes identifying a first set of storage elements of a first word line of the non-volatile memory that satisfy a condition. The condition is based on one or more states of one or more storage elements. The method includes determining a first read voltage corresponding to the first set of storage elements of the first word line and determining a second read voltage corresponding to a second set of storage elements of the first word line that do not satisfy the condition. The method includes reading data from the first word line by applying the first read voltage to the first set of storage elements of the first word line and applying the second read voltage to the second set of storage elements of the first word line.

Claims

1. A method of reading data, the method comprising:

at a data storage device that includes a non-volatile memory having a three-dimensional (3D) configuration and circuitry associated with operation of memory cells of the non-volatile memory, performing;

identifying a first set of storage elements of a first word line of the memory cells of the non-volatile memory that satisfy a condition, wherein the condition is based on one or more states of one or more storage elements, and

wherein identifying the first set of storage elements includes;

reading data from one or more word lines into one or more latches in the data storage device; and

performing one or more bitwise logical operations to the data in the one or more latches to generate flag data that includes one or more bits, each of the one or more bits corresponding to one of the storage elements of the first word line;

determining a first read voltage corresponding to the first set of storage elements of the first word line;

determining a second read voltage corresponding to a second set of storage elements of the first word line that do not satisfy the condition; and

reading first data from the first word line by applying the first read voltage to the first set of storage elements of the first word line and applying the second read voltage to the second set of storage elements of the first word line.

2. The method of claim 1, wherein the condition corresponds to a disturbance of a state of a storage element of the first word line due to cross-coupling with at least one of the one or more storage elements.

3. The method of claim 1, wherein the condition is based on one or more states of one or more storage elements of a second word line that is different from the first word line.

4. The method of claim 1, wherein the condition is based on one or more states of one or more storage elements of the first word line.

5. The method of claim 1, wherein the condition is based on one or more states of one or more storage elements of a second word line that is different from the first word line and based on one or more states of one or more storage elements of the first word line.

6. The method of claim 1, wherein a first group of storage elements affecting evaluation of the condition for a first storage element of the first word line differs from a second group of storage elements affecting evaluation of the condition for a second storage element of the first word line.

7. The method of claim 6, wherein the first group of storage elements affecting the evaluation of the condition for the first storage element includes the first storage element.

8. The method of claim 1, wherein identifying the first set of storage elements includes:

reading second data from a group of one or more storage elements affecting the condition to determine state information of the group of one or more storage elements; and

identifying, for each storage element of the group of one or more storage elements, whether the storage element has a state included in a corresponding set of states,

wherein storage elements of the first word line are identified as being in the first set in response to the state of each storage element of the group of one or more storage elements being included in the corresponding set of states.

9. The method of claim 8, wherein for at least one storage element of the group of one or more storage elements the corresponding set of states includes a highest-voltage state.

10. The method of claim 8, wherein for at least one storage element of the group of one or more storage elements the corresponding set of states includes a lowest-voltage state.

11. The method of claim 1, wherein a first bit value of a particular bit of the one or more bits indicates that a corresponding storage element is included in the first set of storage elements, and wherein a second bit value of the particular bit indicates that the corresponding storage element is included in the second set of storage elements.

12. The method of claim 1, wherein determining the first read voltage includes:

applying a first sequence of read voltages to the first set of storage elements of the first word line to determine a first cell voltage distribution (CVD) that corresponds to the first set of storage elements and that excludes the second set of storage elements; and

selecting the first read voltage based on the first CVD.

13. The method of claim 12, wherein determining the second read voltage includes:

applying a second sequence of read voltages to the second set of storage elements of the first word line to determine a second cell voltage distribution (CVD) that corresponds to the second set of storage elements and that excludes the first set of storage elements; and

selecting the second read voltage based on the second CVD.

14. The method of claim 1, further comprising:

applying a sequence of read voltages to the first set of storage elements of the first word line and to the second set of storage elements of the first word line to generate sensing data;

masking first values of the sensing data corresponding to storage elements in the second set of storage elements to determine a first cell voltage distribution (CVD) corresponding to the first set of storage elements and excluding the second set of storage elements; and

masking second values of the sensing data corresponding to storage elements in the first set of storage elements to determine a second CVD corresponding to the second set of storage elements and excluding the first set of storage elements,

wherein determining the first read voltage includes selecting the first read voltage based on the first CVD, and

wherein determining the second read voltage includes selecting the second read voltage based on the second CVD.

15. The method of claim 1, wherein reading the data from the first word line includes using a parallel sensing operation to apply the first read voltage to the first set of storage elements of the first word line and to apply the second read voltage to the second set of storage elements of the first word line at the same time.

16. The method of claim 1, wherein reading the data from the first word line includes using a single sensing command to apply the first read voltage to the first set of storage elements of the first word line and to apply the second read voltage to the second set of storage elements of the first word line.

17. The method of claim 1, wherein reading the data from the first word line includes using sequential sensing operations to apply the first read voltage to the first set of storage elements of the first word line and to apply the second read voltage to the second set of storage elements of the first word line.

18. A data storage device comprising:

a non-volatile memory having a three-dimensional (3D) configuration and circuitry associated with operation of memory cells of the non-volatile memory; and

a controller configured to identify a first set of storage elements of a first word line of the memory cells of the non-volatile memory that satisfy a condition, wherein the condition is based on one or more states of one or more storage elements, to determine a first read voltage corresponding to the first set of storage elements of the first word line and to determine a second read voltage corresponding to a second set of storage elements of the first word line that do not satisfy the condition,

wherein the controller is configured to identify the first set of storage elements by reading data from one or more word lines into one or more latches in the data storage device and performing one or more bitwise logical operations to the data in the one or more latches to generate flag data that includes one or more bits, each of the one or more bits corresponding to one of the storage elements of the first word line, and

wherein the controller is configured to read first data from the first word line by applying the first read voltage to the first set of storage elements of the first word line and applying the second read voltage to the second set of storage elements of the first word line.

19. The data storage device of claim 18, wherein the condition corresponds to a disturbance of a state of a storage element of the first word line due to cross-coupling with at least one of the one or more storage elements.

20. The data storage device of claim 18, wherein the condition is based on one or more states of one or more storage elements of a second word line that is different from the first word line.

21. The data storage device of claim 18, wherein the condition is based on one or more states of one or more storage elements of the first word line.

22. The data storage device of claim 18, wherein the condition is based on one or more states of one or more storage elements of a second word line that is different from the first word line and based on one or more states of one or more storage elements of the first word line.

23. The data storage device of claim 18, wherein the controller is configured to identify the first set of storage elements by reading second data from a group of one or more storage elements affecting the condition to determine state information of the group of one or more storage elements and identifying, for each storage element of the group of one or more storage elements, whether the storage element has a state included in a corresponding set of states, and wherein storage elements of the first word line are identified as being in the first set in response to the state of each storage element of the group of one or more storage elements being included in the corresponding set of states.

24. The data storage device of claim 18, wherein a first bit value of a particular bit of the one or more bits indicates that a corresponding storage element is included in the first set of storage elements, and wherein a second bit value of the particular bit indicates that the corresponding storage element is included in the second set of storage elements.

25. The data storage device of claim 18, wherein the controller is configured to determine the first read voltage by applying a first sequence of read voltages to the first set of storage elements of the first word line to determine a first cell voltage distribution (CVD) that corresponds to the first set of storage elements and that excludes the second set of storage elements and selecting the first read voltage based on the first CVD.

26. The data storage device of claim 18, wherein the controller is configured to:

apply a sequence of read voltages to the first set of storage elements of the first word line and to the second set of storage elements of the first word line to generate sensing data;

mask first values of the sensing data corresponding to storage elements in the second set of storage elements to determine a first cell voltage distribution (CVD) corresponding to the first set of storage elements and excluding the second set of storage elements; and

mask second values of the sensing data corresponding to storage elements in the first set of storage elements to determine a second CVD corresponding to the second set of storage elements and excluding the first set of storage elements,

wherein determining the first read voltage includes selecting the first read voltage based on the first CVD, and

wherein determining the second read voltage includes selecting the second read voltage based on the second CVD.

27. The data storage device of claim 18, wherein the controller is configured to use a parallel sensing operation to apply the first read voltage to the first set of storage elements of the first word line and to apply the second read voltage to the second set of storage elements of the first word line at the same time to read the data from the first word line.

28. The data storage device of claim 18, wherein the controller is configured to use a single sensing command to apply the first read voltage to the first set of storage elements of the first word line and to apply the second read voltage to the second set of storage elements of the first word line to read the data from the first word line.

29. The data storage device of claim 18, wherein the first read voltage and the second read voltage correspond to a first state boundary and wherein the controller is configured to determine a third read voltage and a fourth read voltage corresponding to a second state boundary, wherein the third read voltage corresponds to the first set of storage elements and wherein the fourth read voltage corresponds to the second set of storage elements.

30. A data storage device comprising:

a non-volatile memory having a three-dimensional (3D) configuration and circuitry associated with operation of memory cells of the non-volatile memory; and

a controller configured to identify a first set of storage elements of a first word line of the memory cells of the non-volatile memory that satisfy a condition, wherein the condition is based on one or more storage elements, to determine a first read voltage corresponding to the first set of storage elements of the first word line and to determine a second read voltage corresponding to a second set of storage elements of the first word line,

wherein the controller is configured to identify the first set of storage elements by reading data from one or more word lines into one or more latches in the data storage device and performing one or more bitwise logical operations to the data in the one or more latches to generate flag data that includes one or more bits, each of the one or more bits corresponding to one of the storage elements of the first word line, and

wherein the controller is configured to apply the first read voltage to the first set of storage elements of the first word line and to apply the second read voltage to the second set of storage elements of the first word line.