Nand memory array incorporating multiple series selection devices and method for operation of same
First Claim
1. An integrated circuit comprising a memory array including memory cells arranged in a plurality of series-connected NAND strings, said memory cells comprising modifiable conductance switch devices, said NAND strings including at a first end thereof a respective plurality of series selection devices.
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Abstract
An exemplary NAND string memory array provides for capacitive boosting of a half-selected memory cell channel to reduce program disturb effects of the half selected cell. To reduce the effect of leakage current degradation of the boosted level, multiple programming pulses of a shorter duration are employed to limit the time period during which such leakage currents may degrade the voltage within the unselected NAND strings. In addition, multiple series select devices at one or both ends of each NAND string further ensure reduced leakage through such select devices, for both unselected and selected NAND strings. In certain exemplary embodiments, a memory array includes series-connected NAND strings of memory cell transistors having a charge storage dielectric, and includes more than one plane of memory cells formed above a substrate.
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Citations
60 Claims
- 1. An integrated circuit comprising a memory array including memory cells arranged in a plurality of series-connected NAND strings, said memory cells comprising modifiable conductance switch devices, said NAND strings including at a first end thereof a respective plurality of series selection devices.
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39. An integrated circuit including a memory array arranged in a plurality of blocks, said integrated circuit comprising:
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a first memory block comprising a first bias node;
a plurality of global bit lines traversing across the first block in a first direction;
a plurality of word lines traversing across the first block in a second direction different than the first direction;
a first group of one or more select lines traversing across the first block generally parallel to and disposed on one side of the plurality of word lines;
a second group of more than one select lines traversing across the first block generally parallel to and disposed on the other side of the plurality of word lines; and
a plurality of series-connected NAND strings, each comprising, at a first end thereof, a first group of one or more series select devices each responsive to a respective one of the first group of one or more select lines, further comprising a plurality of memory cell devices each responsive to a respective one of the plurality of word lines, and further comprising, at a second end thereof, a second group of more than one block select devices each responsive to a respective one of the second group of more than one select lines. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53)
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55. A method for programming a memory cell in a memory array, said memory array having at least one plane of memory cells, said memory cells comprising modifiable conductance switch devices arranged in a plurality of series-connected NAND strings, said method comprising:
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selecting a block of the array, a NAND string within the selected block, and a memory cell within the selected NAND string;
coupling a first end of the selected NAND string to a selected global bit line by turning on each of a group of one or more series select devices at the first end of the selected NAND string;
de-coupling a second end of the selected NAND string from a first shared bias node by turning off at least one of a plurality of series select devices at the second end of the selected NAND string;
impressing a bit line programming voltage onto the selected global bit line to program the selected memory cell or a bit line inhibit voltage to inhibit programming of the selected memory cell; and
pulsing the selected word line to a word line programming voltage, to conditionally program the selected memory cell in accordance with the voltage impressed on the selected global bit line. - View Dependent Claims (56, 57, 58, 59, 60)
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Specification