Vertical switch three-dimensional memory array
View Patent ↗Methods of forming memory devices include providing a substrate, forming source, channel, and drain layers over the substrate, and patterning the source, channel, and drain layers into an array of memory switches each having a cross-sectional area less than 6 F 2 . The channel layer has a doping type different from a doping type of the source layer, and the drain layer has a doping type different from a doping type of the channel layer.
1. A method of forming a memory device, the method comprising:
providing a substrate;
forming a source layer on the substrate;
forming a channel layer over the source layer, the channel layer having a doping type different from a doping type of the source layer;
forming a drain layer over the channel layer, the drain layer having a doping type different from a doping type of the channel layer; and
patterning the source, channel, and drain layers into an array of memory switches each having a cross-sectional area less than 6 F 2 ,
wherein patterning the source, channel, and drain layers comprises:
forming a plurality of generally parallel isolation trenches intersecting the source, channel, and drain layers;
depositing a dielectric material into the plurality of isolation trenches; and
planarizing the dielectric material such that a top surface of the dielectric material is substantially coplanar with a top surface of the drain layer.
2. The method of claim 1 , wherein patterning the source, channel, and drain layers further comprises:
forming a plurality of generally parallel gate trenches intersecting the isolation trenches,
wherein each memory switch is bounded by intersecting isolation trenches and gate trenches.
3. The method of claim 2 , wherein the cross-sectional area of each memory switch is less than approximately 4 F 2 .
4. The method of claim 2 , further comprising:
forming a gate dielectric in contact with the channel layer within the gate trenches;
depositing a gate contact material in the gate trenches; and
planarizing the gate contact material such that a top surface of the gate contact material is substantially coplanar with a top surface of the dielectric material in the isolation trenches.
5. The method of claim 1 , wherein forming the source, channel, and drain layers each comprises ion implantation of dopants into the substrate.
6. The method of claim 1 , wherein forming the source, channel, and drain layers each comprises deposition of a semiconductor material over the substrate.
7. The method of claim 1 , further comprising, substantially simultaneously with patterning the source, channel, and drain layers into an array of memory switches, patterning the source, channel, and drain layers into a plurality of peripheral devices disposed proximate the array of memory switches.
8. The method of claim 7 , further comprising electrically connecting the peripheral devices to the array of memory switches.
9. The method of claim 1 , further comprising:
forming a conductive post over a memory switch; and
forming a programmable material in contact with the conductive post, thereby forming a programmable memory cell.
10. The method of claim 9 , wherein the programmable material comprises at least one of phase-change material, a resistive-change material, or a one-time-programmable material.
11. The method of claim 9 , wherein forming the programmable material comprises etching at least a portion of a dielectric material disposed around the conductive post to form a recess, at least substantially filling the recess with the programmable material, and planarizing the programmable material such that a top surface of the programmable material is substantially coplanar with a top surface of the conductive post.
12. The method of claim 11 , wherein the conductive post has a substantially quadrilateral cross-sectional area, and the programmable material is disposed in contact with only one corner of the conductive post.
13. The method of claim 11 , wherein the conductive post has a substantially quadrilateral cross-sectional area, and the programmable material is disposed in contact with only two corners of the conductive post.
14. The method of claim 1 , wherein the cross-sectional area of each memory switch is less than approximately 4 F 2 .
15. The method of claim 1 , wherein the memory switches comprise four-layer diodes.
16. The method of claim 1 , wherein the memory switches comprise MOS transistors.
17. A method of forming a memory device, the method comprising:
providing a substrate;
forming a source layer on the substrate;
forming a channel layer over the source layer, the channel layer having a doping type different from a doping type of the source layer;
forming a drain layer over the channel layer, the drain layer having a doping type different from a doping type of the channel layer;
patterning the source, channel, and drain layers into an array of memory switches each having a cross-sectional area less than 6 F 2 ;
forming a conductive post over a memory switch; and
forming a programmable material in contact with the conductive post, thereby forming a programmable memory cell.
18. The method of claim 17 , wherein the programmable material comprises at least one of phase-change material, a resistive-change material, or a one-time-programmable material.
19. The method of claim 17 , wherein forming the programmable material comprises etching at least a portion of a dielectric material disposed around the conductive post to form a recess, at least substantially filling the recess with the programmable material, and planarizing the programmable material such that a top surface of the programmable material is substantially coplanar with a top surface of the conductive post.
20. The method of claim 19 , wherein the conductive post has a substantially quadrilateral cross-sectional area, and the programmable material is disposed in contact with only one corner of the conductive post.
21. The method of claim 19 , wherein the conductive post has a substantially quadrilateral cross-sectional area, and the programmable material is disposed in contact with only two corners of the conductive post.
22. The method of claim 17 , wherein patterning the source, channel, and drain layers comprises:
forming a plurality of generally parallel isolation trenches intersecting the source, channel, and drain layers;
depositing a dielectric material into the plurality of isolation trenches;
planarizing the dielectric material such that a top surface of the dielectric material is substantially coplanar with a top surface of the drain layer; and
forming a plurality of generally parallel gate trenches intersecting the isolation trenches,
wherein each memory switch is bounded by intersecting isolation trenches and gate trenches.
23. The method of claim 22 , further comprising:
forming a gate dielectric in contact with the channel layer within the gate trenches;
depositing a gate contact material in the gate trenches; and
planarizing the gate contact material such that a top surface of the gate contact material is substantially coplanar with a top surface of the dielectric material in the isolation trenches.
24. The method of claim 17 , wherein the cross-sectional area of each memory switch is less than approximately 4 F 2 .
25. The method of claim 17 , wherein forming the source, channel, and drain layers each comprises ion implantation of dopants into the substrate.
26. The method of claim 17 , wherein forming the source, channel, and drain layers each comprises deposition of a semiconductor material over the substrate.
27. The method of claim 17 , further comprising, substantially simultaneously with patterning the source, channel, and drain layers into an array of memory switches, patterning the source, channel, and drain layers into a plurality of peripheral devices disposed proximate the array of memory switches.
28. The method of claim 27 , further comprising electrically connecting the peripheral devices to the array of memory switches.
29. The method of claim 17 , wherein the memory switches comprise four-layer diodes.
30. The method of claim 17 , wherein the memory switches comprise MOS transistors.