Nonvolatile Memory Devices and Methods of Operating Same to Inhibit Parasitic Charge Accumulation Therein

• US 20090129165A1
• Filed: 08/14/2008
• Published: 05/21/2009
• Est. Priority Date: 11/21/2007
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Lee, Chang Hyun, Choi, Jung-Dal, Lim, Young-Ho, Suh, Kang-Deog
• Granted Patent: US 7,864,582 B2
• Time in Patent Office: Days
• US Class Current: 365/185.170
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: G11C 16/16 for erasing blocks, e.g. arrays, words, groups

Abstract

Methods of operating a charge trap nonvolatile memory device include operations to erase a first string of nonvolatile memory cells by selectively erasing a first plurality of nonvolatile memory cells in the first string and then selectively erasing a second plurality of nonvolatile memory cells in the first string, which may be interleaved with the first plurality of nonvolatile memory cells. This operation to selectively erase the first plurality of nonvolatile memory cells may include erasing the first plurality of nonvolatile memory cells while simultaneously biasing the second plurality of nonvolatile memory cells in a blocking condition that inhibits erasure of the second plurality of nonvolatile memory cells. The operation to selectively erase the second plurality of nonvolatile memory cells may include erasing the second plurality of nonvolatile memory cells while simultaneously biasing the first plurality of nonvolatile memory cells in a blocking condition that inhibits erasure of the first plurality of nonvolatile memory cells.

Claims

1. A method of operating a nonvolatile memory device, comprising:

erasing a first string of nonvolatile memory cells in the nonvolatile memory device by selectively erasing a first plurality of nonvolatile memory cells in the first string and then selectively erasing a second plurality of nonvolatile memory cells in the first string, which are interleaved with the first plurality of nonvolatile memory cells.

2. The method of claim 1, wherein said erasing the first string of nonvolatile memory cells comprises:

erasing the first plurality of nonvolatile memory cells while simultaneously biasing the second plurality of nonvolatile memory cells in a blocking condition that inhibits erasure of the second plurality of nonvolatile memory cells; and

erasing the second plurality of nonvolatile memory cells while simultaneously biasing the first plurality of nonvolatile memory cells in a blocking condition that inhibits erasure of the first plurality of nonvolatile memory cells.

3. The method of claim 2, wherein the first string of nonvolatile memory cells is a NAND-type string.

4. The method of claim 3, wherein each of the nonvolatile memory cells in the first string is a charge-trap nonvolatile memory cell.

5. The method of claim 3, wherein the first string of nonvolatile memory cells comprises a charge storage layer.

6. The method of claim 2, wherein the first string of nonvolatile memory cells is disposed in a semiconductor well region of first conductivity type;

and wherein erasing the first plurality of nonvolatile memory cells while simultaneously biasing the second plurality of nonvolatile memory cells in a blocking condition comprises biasing the word lines associated with the first and second pluralities of nonvolatile memory cells at unequal voltages so that a voltage difference between the word lines associated with the first plurality of nonvolatile memory cells and the semiconductor well region is greater than a voltage difference between the word lines associated with the second plurality of nonvolatile memory cells and the semiconductor well region.

7. A nonvolatile memory device, comprising:

an array of nonvolatile memory cells electrically coupled to a plurality of functional word lines that extend over corresponding channel regions of the nonvolatile memory cells in said array and a plurality of dummy word lines that respectively extend between corresponding pairs of functional word lines.

8. The memory device of claim 7, wherein the dummy word lines extend opposite corresponding source/drain regions of the nonvolatile memory cells in said array.

9. The device of claim 7, further comprising a word line driver electrically coupled to the plurality of functional word lines and the plurality of dummy word lines, said word line driver configured to drive the plurality of functional word lines and the plurality of dummy word lines with erase voltages and blocking voltages, respectively, that are unequal, during an operation to erase the array of nonvolatile memory cells.

10. A method of operating a string of nonvolatile memory cells, comprising:

erasing at least a first nonvolatile memory cell within the string by biasing a first word line associated with the first nonvolatile memory cell at a first voltage having a magnitude sufficient to establish or exceed a critical erase voltage between the first word line and a channel region of the first nonvolatile memory cell while concurrently biasing a second word line associated with a second nonvolatile memory cell extending immediately adjacent the first nonvolatile memory cell at a second voltage having a magnitude insufficient to establish a critical erase voltage between the second word lines and a channel region of the second nonvolatile memory cell.

11. The method of claim 10, further comprising erasing the second nonvolatile memory cell by biasing the second word line at the first voltage while concurrently biasing the first word line at the second voltage.

12. A nonvolatile memory device, comprising:

a nonvolatile memory cell comprising a word line on a semiconductor substrate and first and second source/drain regions within a semiconductor substrate; and

first and second dummy word lines on the first and second source/drain regions, respectively.

13. The memory device of claim 12, wherein said nonvolatile memory cell comprises a charge storage layer extending between the first and second dummy word lines and the first and second source/drain regions.

14. A memory device, comprising:

a nonvolatile memory array having a plurality of rows of charge trap memory cells therein that are electrically coupled to a respective plurality of word lines; and

a voltage generator electrically coupled to the plurality of word lines, said voltage generator configured to drive a first plurality of the word lines with an erase voltage and concurrently drive a second plurality of the word lines with a blocking voltage, unequal to the erase voltage, during an operation to erase the nonvolatile memory array.

15. The memory device of claim 14, wherein said voltage generator is configured to drive the first plurality of the word lines with the erase voltage and concurrently drive the second plurality of the word lines with the blocking voltage during a first-half of the operation to erase the nonvolatile memory array;

and wherein said voltage generator is further configured to drive the second plurality of the word lines with the erase voltage and concurrently drive the first plurality of the word lines with the blocking voltage during a second-half of the operation to erase the nonvolatile memory array.

16. The memory device of claim 14, wherein said voltage generator is further configured to generate pass and read voltages;

and wherein said voltage generator is configured to generate the blocking voltage at a voltage equivalent to the pass voltage or the read voltage or a power supply voltage.

17. The memory device of claim 14, wherein the memory device is a flash memory device.

18. The memory device of claim 17, in combination with components of a memory card, including an error checking and correction circuit, a processing unit and a host interface circuit.

19. The memory device of claim 17, in combination with components of a memory system, including a memory controller, a processing unit and an interface circuit.

20. The memory device of claim 15, in combination with components of a memory card, including an error checking and correction circuit, a processing unit and a host interface circuit.

21. The memory device of claim 15, in combination with components of a memory system, including a memory controller, a processing unit and an interface circuit.

22. A method of operating a nonvolatile memory device, comprising:

erasing a first memory cell in a string of nonvolatile memory cells by establishing a first voltage difference between a gate of the first memory cell and a well region of the first memory cell while concurrently establishing a second voltage difference, which is less than the first voltage difference, between a gate of a second memory cell in the string and a well region of the second memory cell.

23. The method of claim 22, wherein said erasing comprises:

erasing a first plurality of memory cells in the string while simultaneously biasing a second plurality of memory cells in the string in a blocking condition that inhibits erasure of the second plurality of memory cells.

24. The method of claim 23, wherein said erasing comprises:

erasing the second plurality of memory cells in the string while simultaneously biasing the first plurality of memory cells in the string in a blocking condition that inhibits erasure of the first plurality of memory cells.

25. The method of claim 22, wherein the nonvolatile memory cells in the string are charge-trap memory cells comprising charge storage layers.

26. The method of claim 23, wherein erasing the first plurality of memory cells in the string comprises driving word lines associated with the first plurality of memory cells in the string with an erase voltage;

and wherein biasing the second plurality of memory cells in the string in a blocking condition comprises driving word lines associated with the second plurality of memory cells in the string with a blocking voltage having a magnitude greater than the erase voltage.

27. The method of claim 26, wherein erasing the first plurality of memory cells in the string comprises driving a p-well region associated with the first plurality of memory cells in the string with a p-well voltage having a magnitude greater than a minimum critical erase voltage necessary to erase the first plurality of memory cells during said erasing.

28. The method of claim 26, wherein erasing the first plurality of memory cells in the string comprises driving a p-well region associated with the first plurality of memory cells in the string with a p-well voltage having a magnitude greater than a sum of a minimum critical erase voltage necessary to erase the first plurality of memory cells during said erasing and the erase voltage.

29. The method of claim 22, wherein said erasing comprises:

erasing a first plurality of memory cells in the string while simultaneously electrically floating the gate of the second memory cell.