Integrated circuit including memory array incorporating multiple types of NAND string structures
View Patent ↗A monolithic integrated circuit includes a memory array having first and second groups of NAND strings, each NAND string comprising at least two series-connected devices and coupled at one end to an associated global array line. NAND strings of the first and second groups differ in at least one physical characteristic, such as the number of series-connected devices forming the NAND string, but both groups are disposed in a region of the memory array traversed by a plurality of global array lines. The memory array may include a three-dimensional memory array having more than one memory plane. Some of the NAND strings of the first group may be disposed on one memory plane, and some of the NAND strings of the second group may be disposed on another memory plane. In some cases, NAND strings of both groups may share global array lines.
1. A monolithic integrated circuit comprising a memory array, said memory array comprising first and second groups of NAND strings, each NAND string comprising at least two series-connected devices and coupled at one end thereof to an associated global array line, wherein NAND strings of the first group differ in at least one physical characteristic from NAND strings of the second group, wherein NAND strings of both the first and second group are disposed in a region of the memory array traversed by a plurality of global array lines, and wherein the second group of NAND strings are configured to store configuration data hidden during normal operation of the integrated circuit.
2. The integrated circuit as recited in claim 1 wherein the physical characteristic comprises drive strength, and NAND strings of the first group have a different drive strength than NAND strings of the second group.
3. The integrated circuit as recited in claim 1 wherein each NAND string comprises a group of one or more memory cell devices in series with at least one select device.
4. The integrated circuit as recited in claim 1 wherein the physical characteristic comprises the respective number of series-connected devices forming the respective NAND string, and wherein NAND strings of the first group have a larger number of series-connected devices than NAND strings of the second group.
5. The integrated circuit of claim 1 embodied in computer readable descriptive form suitable for use in design, test or fabrication of the integrated circuit.
6. A monolithic integrated circuit comprising a memory array, said memory array comprising first and second groups of NAND strings, each NAND string comprising at least two series-connected devices and coupled at one end thereof to an associated global array line, wherein NAND strings of the first group differ in at least one physical characteristic from NAND strings of the second group, wherein NAND strings of both the first and second group are disposed in a region of the memory array traversed by a plurality of global array lines, wherein the physical characteristic comprises the respective number of series-connected devices forming the respective NAND string, and wherein NAND strings of the first group have a larger number of series-connected devices than NAND strings of the second group, and wherein:
the memory array comprises a three-dimensional memory array having more than one memory plane; and
at least some of the NAND strings of the first group are disposed on at least a first memory plane; and
at least some of the NAND strings of the second group are disposed on at least a second memory plane different than the first memory plane.
7. The integrated circuit as recited in claim 6 further comprising write circuitry shared by both NAND strings of the first and second groups.
8. The integrated circuit as recited in claim 7 further comprising read circuitry shared by both NAND strings of the first and second groups.
9. The integrated circuit as recited in claim 6 wherein:
each NAND string comprises a group of one or more memory cell devices in series with at least one select device;
NAND strings on more than one memory plane share global array lines; and
at least some of the NAND strings of both the first and second groups share global array lines.
10. The integrated circuit as recited in claim 9 wherein:
memory cells of at least the first or second group comprise a charge storage dielectric.
11. The integrated circuit as recited in claim 9 wherein NAND strings of the second group each includes at most two memory cell devices and a single select device at each end thereof.
12. The integrated circuit as recited in claim 9 wherein the select devices and the memory cell devices of both first and second groups comprise thin film devices having a charge storage dielectric.
13. The integrated circuit as recited in claim 9 wherein the second group of NAND strings are configured to store configuration data hidden during normal operation of the integrated circuit.
14. The integrated circuit as recited in claim 13 wherein the configuration data comprises redundancy information for the memory array.
15. The integrated circuit as recited in claim 9 wherein the memory array further comprises NAND strings of a third group having a different number of series-connected devices than the first and second groups of NAND strings.
16. The integrated circuit as recited in claim 9 comprising NAND strings of the second group disposed laterally displaced from NAND strings of the first group.
17. The integrated circuit as recited in claim 16 wherein:
NAND strings of the first group are disposed on more than one plane;
NAND strings of the second group are disposed on more than one plane; and
NAND strings of both the first and second groups share global array lines.
18. The integrated circuit as recited in claim 9 comprising on a first memory plane NAND strings of the first group which are disposed above or below NAND strings of the second group on a second memory plane.
19. The integrated circuit as recited in claim 18 wherein NAND strings of the second group are disposed on one or more memory planes closest to a substrate of the integrated circuit.
20. The integrated circuit as recited in claim 18 comprising on the second memory plane more than one NAND string of the second group disposed in the same region generally corresponding to a single NAND string of the first group on the first memory plane.
21. The integrated circuit as recited in claim 20 comprising an odd number of NAND strings of the second group disposed in the same region corresponding to a single NAND string of the first group, said odd number of NAND strings being generally in-line and coupled together to define a respective common node connecting each such NAND string, said respective common nodes alternately coupled to a vertical global array line connection and a vertical bias node connection.
22. The integrated circuit as recited in claim 18 wherein the memory array comprises:
a first set of contiguous memory planes comprising NAND strings of the first group; and
a second set of contiguous memory planes comprising NAND strings of the second group; and
a first group of vertical connections, each respectively connecting at least one NAND string on each memory plane to a respective global array line on a first global array line layer.
23. The integrated circuit as recited in claim 22 wherein NAND strings of the second group each consists of a single memory cell device and a single select device at each end thereof.
24. The integrated circuit as recited in claim 22 further comprising a second group of vertical connections, each respectively connecting at least one NAND string on each memory plane of the second set to a respective global array line on the first global array line layer, without connecting to any NAND string on memory planes of the first set.
25. The integrated circuit as recited in claim 22 wherein, on each memory plane of the first and second sets, both NAND strings of an adjacent pair of NAND strings are respectively coupled at the same end thereof to a respective associated global array line on the first global array line layer.
26. The integrated circuit as recited in claim 22 further comprising:
a third group of vertical connections, each respectively connecting at least one NAND string on each memory plane of the first set to a respective global array line on a second global array line layer different than the first global array line layer.
27. The integrated circuit as recited in claim 26 wherein:
for an adjacent pair of NAND strings on a memory plane of the first set, one NAND string of the adjacent pair is associated with a global array line on the first global array line layer, and the other NAND string of the adjacent pair is associated with a global array line on the second global array line layer.
28. The integrated circuit as recited in claim 27 wherein:
for an adjacent pair of NAND strings on a memory plane of the second set, one NAND string of the adjacent pair is coupled at one end thereof, and the other NAND string of the adjacent pair is coupled at the opposite end thereof, both to one associated global array line on the first global array line layer.
29. The integrated circuit of claim 6 embodied in computer readable descriptive form suitable for use in design, test or fabrication of the integrated circuit.