Programming memory devices

• US 7,345,924 B2
• Filed: 10/11/2006
• Issued: 03/18/2008
• Est. Priority Date: 05/11/2005
• Status: Expired due to Fees

• Current Assignee: Round Rock Research LLC
• Original Assignee: Micron Technology, Inc.
• Inventors: Louie, Benjamin, Yip, Aaron, Han, Jin-Man, Nguyen, Dzung H., Nazarian, Hagop A.
• Primary Examiner(s): Hoang; Huan
• Application Number:
  US11/546,171
• Publication Number:
  US 20070047326A1
• Time in Patent Office: 524 Days
• Field of Search: 365/185.28, 365/185.17, 365/185.18
• US Class Current: 365/185.28
• CPC Class Codes: G11C 16/10 Programming or data input circuits

Abstract

A target memory cell of a memory device is programmed by applying a programming voltage to a word line that includes the target memory cell, determining whether the target memory cell is programmed, and increasing the programming voltage by a step voltage if it is determined that the target memory cell is not programmed. An initial programming voltage and the step voltage are each selectable after fabrication of the memory device.

Claims

1. A method of programming a target memory cell of a memory device, comprising:

applying a first voltage, at a first time, to a word line that includes the target memory cell;

applying a second voltage, at the first time, to word lines that do not include the target memory cell;

applying a third voltage, at the first time, to a bit line selectively coupled to a string of memory cells that includes the target memory cell;

increasing the first and second voltages at substantially the same rate, starting at a second time after the first time, until the first and second voltages reach a pass voltage level at a third time after the second time;

increasing the first voltage from the pass voltage, starting at the third time, to an initial programming voltage level at a fourth time after the third time;

maintaining the first voltage at the initial programming voltage level until a fifth time after the fourth time; and

determining whether the target memory cell is programmed after the fifth time; and

increasing the initial programming voltage level by a step voltage if it is determined that the target memory cell is not programmed;

wherein the initial programming voltage, the step voltage, the pass voltage, a length of time between the second and third times, and a length of time between the third and fifth times are each selectable after fabrication of the memory device.

2. The method of claim 1 further comprises maintaining a fourth voltage applied to a source select line coupled to a control gate of a source select gate that selectively couples a source line to the string of memory cells that includes the target memory cell at Vss from the first time until after the fifth time.

3. The method of claim 2 further comprises increasing a fifth voltage applied to the source line from about 0 volts, starting at the first time, to Vcc at the second time and maintaining the fifth voltage at Vcc from the second time until after the fifth time.

4. The method of claim 3 further comprises increasing a sixth voltage applied to a drain select line coupled to a control gate of a drain select gate that selectively couples the bit line to the NAND string that includes the target memory cell from about zero volts, starting at the first time, to Vcc before the second time, decreasing the fifth voltage from Vcc to a third voltage level, at the second time, that is selectable after fabrication of the memory device, and maintaining the sixth voltage at the third voltage level from the second time until after the fifth time.

5. The method of claim 1 further comprising decreasing the first and second voltages to about 0 volts after the fifth time, but before determining whether the target memory cell is programmed.

6. The method of claim 1, wherein applying the third voltage, at the first time, to a bit line further comprises maintaining the third voltage at about 0 volts from the first time until after the fifth time or increasing the third voltage from about 0 volts, starting at the first time, to an inhibit voltage at the second time and maintaining the third voltage at the inhibit voltage from the second time until after the fifth time.

7. A method of programming a memory device, comprising:

applying a first voltage, at a first time, to a first word line that includes a plurality of memory cells to be programmed;

applying a second voltage, at the first time, to second word lines that include memory cells not to be programmed;

applying a third voltage, at the first time, to one or more first bit lines selectively coupled to the first word line and the second word lines for programming one or more first memory cells, of the plurality of memory cells of the first word line to be programmed, at a first logic level;

applying a fourth voltage, at the first time, to one or more second bit lines selectively coupled to the first word line and the second word lines for programming one or more second memory cells, of the plurality of memory cells of the first word line to be programmed, at a second logic level;

increasing the first and second voltages at substantially the same rate, starting at a second time after the first time, until the first and second voltages reach a pass voltage level at a third time after the second time;

increasing the first voltage from the pass voltage, starting at the third time, to an initial programming voltage level at a fourth time after the third time;

maintaining the first voltage at the initial programming voltage level until a fifth time after the fourth time; and

determining whether the one or more first memory cells are programmed at the first logic level after the fifth time; and

increasing the initial programming voltage level by a step voltage if it is determined that the one or more first memory cells are not programmed at the first logic level;

wherein the initial programming voltage, the step voltage, the pass voltage, a length of time between the second and third times, and a length of time between the third and fifth times are each selectable after fabrication of the memory device.

8. The method of claim 7 further comprises maintaining a fifth voltage applied to a source select line, coupled to control gates of source select gates of the memory device, at Vss from the first time until after the fifth time, wherein each source select gate selectively couples a corresponding string of memory cells that includes one of memory cells to be programmed to a common source line.

9. The method of claim 8 further comprises increasing a sixth voltage applied to the common source line from about 0 volts, starting at the first time, to Vcc at the second time and maintaining the fifth voltage at Vcc from the second time until after the fifth time.

10. The method of claim 9 further comprises increasing a seventh voltage applied to a drain select line, coupled to control gates of drain select gates of the memory device, from about zero volts, starting at the first time, to Vcc before the second time, decreasing the seventh voltage from Vcc to a third voltage level, at the second time, that is selectable after fabrication of the memory device, and maintaining the seventh voltage at the third voltage level from the second time until after the fifth time, wherein each drain select gate selectively couples a corresponding string of memory cells that includes one of memory cells to be programmed to one of the first or second bit lines.

11. The method of claim 7 further comprising decreasing the first and second voltages to about 0 volts after the fifth time, but before determining whether the one or more first memory cells are programmed at the first logic level.

12. The method of claim 7, wherein applying a third voltage, at the first time, to one or more first bit lines further comprises maintaining the third voltage at about 0 volts from the first time until after the fifth time.

13. The method of claim 12, wherein applying a fourth voltage, at the first time, to one or more second bit lines further comprises increasing the fourth voltage from about 0 volts, starting at the first time, to an inhibit voltage at the second time and maintaining the fourth voltage at the inhibit voltage from the second time until after the fifth time.

14. A NAND memory device comprising:

a memory array comprising;

a plurality of rows of memory cells, each row connected to a word line; and

a plurality of columns of NAND strings of memory cells, each NAND string selectively connected to a bit line through a drain select gate of the respective column and to a source line through a source select gate of the respective column;

control circuitry coupled to the memory array, the control circuitry adapted to perform a method for programming a target memory cell of the memory array, comprising;

applying a first voltage, at a first time, to a word line that includes the target memory cell;

applying a second voltage, at the first time, to word lines that do not include the target memory cell;

increasing the first and second voltages at substantially the same rate, starting at a second time after the first time, until the first and second voltages reach a pass voltage level at a third time after the second time;

increasing the first voltage from the pass voltage, starting at the third time, to an initial programming voltage level at a fourth time after the third time;

maintaining the first voltage at the initial programming voltage level until a fifth time after the fourth time;

determining whether the target memory cell is programmed after the fifth time; and

increasing the initial programming voltage level by a step voltage if it is determined that the target memory cell is not programmed;

a first register for storing a value corresponding to the pass voltage level, the first register programmable after fabrication and coupled to the control circuitry;

a second register for storing a value corresponding to the initial programming level, the second register programmable after fabrication and coupled to the control circuitry;

a third register for storing a value corresponding to the voltage step, the third register programmable after fabrication and coupled to the control circuitry;

a fourth register for storing a value corresponding to the length of time between the second and third times, the fourth register programmable after fabrication and coupled to the control circuitry; and

a fifth register for storing a value corresponding to a length of time between the third and fifth times, the fifth register programmable after fabrication and coupled to the control circuitry.

15. The NAND memory device of claim 14, wherein the method further comprises maintaining a third voltage applied to a source select line coupled to a control gate of a source select gate that selectively couples a source line to a NAND string of memory cells that includes the target memory cell at Vss from the first time until after the fifth time.

16. The NAND memory device of claim 15, wherein the method further comprises maintaining a fourth voltage applied to a bit line selectively coupled to the NAND string of memory cells that includes the selected memory cell at about 0 volts from the first time until after the fifth time or increasing the fourth voltage from about 0 volts, starting at the first time, to an inhibit voltage at the second time and maintaining the fourth voltage at the inhibit voltage from the second time until after the fifth time.

17. The NAND memory device of claim 16, wherein method further comprises increasing a fifth voltage applied to the source line from about 0 volts, starting at the first time, to Vcc at the second time and maintaining the fifth voltage at Vcc from the second time until after the fifth time.

18. The NAND memory device of claim 17, wherein the method further comprises increasing a sixth voltage applied to a drain select line coupled to a control gate of a drain select gate that selectively couples the bit line to the NAND string that includes the target memory cell from about zero volts, starting at the first time, to Vcc before the second time, decreasing the sixth voltage from Vcc to a third voltage level at the second time, and maintaining the sixth voltage at the third voltage level from the second time until after the fifth time.

19. The NAND memory device of claim 18 further comprises a sixth register for storing a value corresponding to the third voltage level, the sixth register programmable after fabrication and coupled to the control circuitry.

20. The NAND memory device of claim 14, wherein the method further comprises decreasing the first and second voltages to about 0 volts after the fifth time, but before determining whether the target memory cell is programmed.