Memory devices with isolation structures
Memory devices and methods of programming and forming the same are disclosed. In one embodiment, a memory device has memory cells contained within dielectric isolation structures to isolate them from at least those memory cells in communication with other bit lines, such as to facilitate forward-bias write operations. The dielectric isolation structures contain an upper well having a first conductivity type and a buried well having a second conductivity type. By forward biasing the junction from the buried well to the upper well, electrons can be injected into charge-storage nodes of memory cells that are contained within the dielectric isolation structures.
1. A memory device, comprising:
an array of memory cells arranged in rows and columns; and
a plurality of bit lines in communication with the columns of the memory cells of the array;
wherein at least one first memory cell of the array in communication with a first bit line of the plurality of bit lines has a first conductive region contained within a first dielectric isolation structure, wherein the first dielectric isolation structure electrically isolates the first conductive region of the at least one first memory cell from at least one of the columns of the memory cells of the array that is in communication with one bit line of the plurality of bit lines other than the first bit line; and
wherein the first dielectric isolation structure is a closed structure containing the first conductive region of the at least one first memory cell.
2. The memory device of claim 1 , wherein the at least one first memory cell of the array in communication with the first bit line of the plurality of bit lines comprises at least two memory cells of the array coupled to the first bit line of the plurality of bit lines and having source/drain regions contained within the first dielectric isolation structure.
3. The memory device of claim 1 , wherein each of the at least one first memory cells of the array in communication with the first bit line of the plurality of bit lines has source/drain regions contained within the first dielectric isolation structure.
4. The memory device of claim 1 , further comprising:
wherein at least one second memory cell of the array in communication with a second bit line of the plurality of bit lines has a second conductive region within a second dielectric isolation structure, wherein the second dielectric isolation structure electrically isolates the second conductive region of the at least one second memory cell of the array in communication with the second bit line of the plurality of bit lines from at least one of the columns of the memory cells of the array in communication with one bit line of the plurality of bit lines other than the second bit line.
5. The memory device of claim 4 , wherein the first dielectric isolation structure and the second dielectric isolation structure share a trench isolation structure.
6. The memory device of claim 1 , further comprising:
wherein the first conductive region contained within the first dielectric isolation structure comprises an upper well having a first conductivity type and a buried well having a second conductivity type;
wherein the upper well is formed overlying the buried well; and
wherein the buried well is adapted to receive a different bias than the upper well.
7. The memory device of claim 6 , further comprising:
a first contact coupled to the upper well of the first conductive region;
one or more other conductive regions passing through the upper well of the first conductive region to the buried well of the first conductive region; and
a second contact coupled to the buried well of the first conductive region through the one or more other conductive regions passing through the upper well of the first conductive region.
8. The memory device of claim 7 , wherein the first contact is isolated from the second contact by an isolation region formed in the upper well of the first conductive region between the first contact and the second contact.
9. The memory device of claim 6 , wherein the first conductivity type is a p-type conductivity and the second conductivity type is an n++-type conductivity.
10. The memory device of claim 6 , wherein the upper well is an epitaxial silicon.
11. The memory device of claim 1 , wherein the array of the memory cells has a NAND architecture and wherein the at least one first memory cell comprises at least one NAND string of the memory cells of the array in communication with the first bit line, wherein each memory cell of the at least one NAND string has its first conductive region contained within the first dielectric isolation structure.
12. The memory device of claim 11 , wherein the at least one NAND string of the memory cells is formed within the first dielectric isolation structure.
13. The memory device of claim 1 , wherein the first dielectric isolation structure comprises a buried dielectric formed in a support structure, and trench isolation structures formed to be in contact with the buried dielectric and to define the closed structure.
14. The memory device of claim 13 , wherein the buried dielectric is a dielectric material selected from the group consisting of an oxide and a nitride.
15. The memory device of claim 13 , wherein one of the trench isolation structures of the first dielectric isolation structure is generally T-shaped.
16. The memory device of claim 13 , wherein one of the trench isolation structures of the first dielectric isolation structure is laterally separated from an adjacent one of the dielectric isolation structures containing the at least one of the columns of the memory cells of the array in communication with the one bit line of the plurality of bit lines other than the first bit line of the plurality of bit lines.
17. The memory device of claim 13 , wherein the at least one first memory cell of the array in communication with the first bit line of the plurality of bit lines comprises a charge storage node overlying the first dielectric isolation structure.
18. The memory device of claim 17 , wherein the charge storage node extends over portions of the trench isolation structures of the first dielectric isolation structure.
19. The memory device of claim 17 , wherein the charge storage node is laterally separated from the trench isolation structures of the first dielectric isolation structure.
20. The memory device of claim 1 , wherein the array of the memory cells has a NOR architecture.
21. The memory device of claim 20 , wherein each memory cell of the array in communication with the first bit line of the plurality of bit lines has source/drain regions contained within the first dielectric isolation structure.
22. A memory device, comprising:
an array of memory cells arranged in rows and columns and having a NAND architecture; and
a plurality of bit lines in communication with the columns of the memory cells of the array;
wherein at least one NAND string of the memory cells of the array in communication with a first bit line of the plurality of bit lines, each memory cell of the at least one NAND string having a conductive region contained within a first dielectric isolation structure, wherein the first dielectric isolation structure electrically isolates the conductive regions of the memory cells of the at least one NAND string from at least one of the columns of the memory cells of the array in communication with one bit line of the plurality of bit lines other than the first bit line;
wherein the first dielectric isolation structure is a closed structure containing the conductive regions of the memory cells of the at least one NAND string;
wherein the conductive regions of the memory cells of the at least one NAND string comprise an upper well having a first conductivity type and a buried well having a second conductivity type;
wherein the upper well is formed overlying the buried well; and
wherein the buried well is adapted to receive a different bias than the upper well.