Methods, structures and devices for increasing memory density
Non-volatile memory devices comprising a memory string including a plurality of vertically superimposed diodes. Each of the diodes may be arranged at different locations along a length of the electrode and may be spaced apart from adjacent diodes by a dielectric material. The electrode may electrically couple the diodes of the memory strings to one another and to another memory device, such as, a MOSFET device. Methods of forming the non-volatile memory devices as well as intermediate structures are also disclosed.
1. A non-volatile memory device, comprising:
a plurality of transistors on a substrate, each transistor of the plurality of transistors electrically coupled to a word line and a bit line;
a plurality of memory strings over the plurality of transistors, each memory string of the plurality of memory strings comprising a plurality of diodes;
an electrode electrically connecting at least two memory strings of the plurality of memory strings to at least one transistor of the plurality of transistors, the plurality of diodes arranged at locations spaced along a length of the electrode; and
a dielectric material between and electrically isolating at least another two memory strings of the plurality of memory strings.
2. The non-volatile memory device of claim 1 , wherein the electrode comprises a metal contact plug having at least one of a metal or a ceramic material on sidewalls thereof.
3. The non-volatile memory device of claim 1 , wherein the electrode comprises a phase change material.
4. The non-volatile memory device of claim 1 , wherein each memory string of the plurality of memory strings further comprises at least one barrier material between the plurality of diodes and the electrode.
5. The non-volatile memory device of claim 1 , wherein each diode of the plurality of diodes comprises an intrinsic region between oppositely doped regions, the intrinsic region and the oppositely doped regions extending perpendicular to a length of the electrode.
6. The non-volatile memory device of claim 1 , wherein the plurality of diodes are aligned in a first direction to form a plurality of columns and are aligned in a second direction substantially perpendicular the first direction to form a plurality of rows.
7. A semiconductor structure comprising:
a plurality of diodes overlying a substrate and vertically superimposed over one another to form a plurality of columns, each diode of the plurality of diodes comprising an intrinsic region between oppositely doped regions, the plurality of diodes of adjacent columns being mirror images of one another; and
a dielectric material between at least two adjacent columns of the plurality of columns to isolate the plurality of diodes of the at least two adjacent columns from one another.
8. The semiconductor structure of claim 7 , further comprising an electrode between at least two columns of the plurality of columns.
9. The semiconductor structure of claim 7 , further comprising a transistor array underlying the plurality of diodes and comprising a plurality of transistors, each of the plurality of transistors between a source region and a drain region in the substrate and electrically coupled to a cell plug.
10. The semiconductor structure of claim 7 , wherein each of the plurality of diodes in one of the plurality of columns is substantially horizontally aligned with each of the plurality of diodes in another of the plurality of columns.
11. The semiconductor structure of claim 7 , wherein at least one of the oppositely doped regions and the intrinsic region extend along a length of the substrate in a direction substantially perpendicular to the plurality of columns.
12. The semiconductor structure of claim 7 , further comprising a contact electrically coupled to an electrode via a semiconductive material extending between the contact and the electrode.
13. The semiconductor structure of claim 9 , wherein at least one of the plurality of columns at least partially overlies a portion of the cell plug.
14. A method of forming a semiconductor structure, comprising:
forming a plurality of alternating first regions and second regions to form a cell stack over a foundation material overlying a transistor array, the transistor array comprising a plurality of transistors electrically coupled to a plurality of cell plugs;
removing portions of the first regions and second regions exposed through a mask to form a plurality of first slots therethrough, each of the plurality of first slots overlying one of the plurality of cell plugs;
introducing a dopant to exposed portions of the first regions to form a plurality of first doped regions;
forming a silicide material over each of the plurality of first doped regions;
forming a fill material over the semiconductor structure to at least fill the plurality of first slots;
removing portions of the first regions and second regions exposed through another mask to form a plurality of second slots laterally spaced apart from each of the plurality of first slots; and
introducing a dopant to exposed portions of the first regions to form a plurality of second doped regions, an intrinsic region of the first region disposed between the plurality of second doped regions and the plurality of first doped regions.
15. The method of claim 14 , wherein removing portions of the first regions and second regions exposed through a mask to form a plurality of first slots therethrough comprises removing the portions of the first regions and second regions exposed through the mask to form a plurality of elongate trenches therethrough.
16. The method of claim 14 , wherein forming a plurality of alternating first regions and second regions to form a cell stack over a foundation material overlying a transistor array comprises:
attaching a wafer comprising crystalline silicon to the foundation material; and
separating a portion of the wafer to leave a first semiconductive region overlying the foundation material.
17. The method of claim 14 , further comprising removing the mask from the semiconductor structure to form protruding regions of the fill material in each of the first slots.
18. The method of claim 14 , wherein removing portions of the first regions and second regions exposed through another mask to form a plurality of second slots comprises:
forming spacers on protruding regions of the fill material;
forming at least one material over the spacers, the at least one material having a plurality of openings exposing portions of the cell stack between the first slots; and
removing the exposed portions of the cell stack to form the plurality of second slots.
19. The method of claim 14 , wherein removing portions of the first regions and second regions exposed through another mask to form a plurality of second slots comprises removing portions of the first regions and second regions exposed through the another mask to form a plurality of second slots, each of which circumscribes at least one of the plurality of first slots.
20. The method of claim 14 , further comprising removing portions of the first regions and second regions to form a plurality of tiers in a peripheral region of the cell stack, each of the plurality of tiers comprising an exposed surface of one of the plurality of first regions.
21. The method of claim 14 , further comprising forming at least one of a ceramic material, a conductive material, and a phase change material over sidewalls of the plurality of second slots.
22. The method of claim 14 , further comprising removing a portion of the foundation material to expose surfaces of the plurality of cell plugs.
23. The method of claim 18 , wherein forming spacers on protruding regions of the fill material comprises forming the spacers having a width sufficient to overlie the first doped regions.
24. The method of claim 20 , further comprising:
introducing a dopant to exposed portions of the first regions on the tiers to form doped material; and
converting at least a portion of the doped material to a silicide material to form contacts.