On/off ratio for non-volatile memory device and method
A switching device includes a first dielectric material formed overlying a substrate. A bottom wiring material and a switching material are sequentially formed overlying the first dielectric material. The bottom wiring material and the switching material are patterned and etched to form a first structure having a top surface region and a side region. The first structure includes a bottom wiring structure and a switching element having the top surface region including an exposed region. A second dielectric material is formed overlying the first structure. A first opening region is formed in a portion of the second dielectric layer to expose a portion of the top surface region. A dielectric side wall structure is formed overlying a side region of the first opening region. A top wiring material including a conductive material is formed overlying the top surface region to be directly contact with the switching element.
1. A switching device, comprising:
a substrate having a surface region;
a first dielectric material overlying the surface region of the substrate;
a bottom wiring structure overlying the first dielectric material;
a first structure comprising at least a contact material overlying the bottom wiring structure and a switching material overlying the contact layer, the first structure having a top surface region substantially parallel to the surface region of the substrate, the top surface region including a top region of the switching material, wherein the switching material is configured to allow a conductive filament to form therein;
a second dielectric layer overlying the first structure, wherein the second dielectric layer comprises a sidewall and an opening region exposing a first portion and a second portion of the top region of the switching material;
a side wall spacer structure disposed within the sidewall of the opening region of the second dielectric layer, wherein the side wall spacer structure covers the first portion of the top surface of the switching material but not the second portion of the top surface region of the switching material, the side wall spacer structure being formed using a third dielectric material;
a conductive material overlying the side wall spacer structure, the conductive material overlying and in contact with the second portion of the top surface region of the switching material but not the first portion of the top surface region of the switching material, and wherein the conductive material is a source of conductive particles for the conductive filament; and
a top wiring structure overlying the conductive material.
2. The device of claim 1 wherein the first dielectric material comprises silicon oxide or silicon nitride or a silicon oxide on silicon nitride on silicon oxide stack.
3. The device of claim 1 wherein the second dielectric material comprises silicon oxide.
4. The device of claim 1 wherein the third dielectric material comprises silicon nitride, silicon oxide, or a dielectric stack, the dielectric stack comprises a silicon oxide on silicon nitride on silicon oxide (ONO) stack.
5. The device of claim 1 wherein the second portion of the top surface region of the switching material defines an active device region.
6. The device of claim 1 further characterized by an on-state current and an off-state current, the on-state current being independent of an area of the second portion of the top surface-region and the off-state current being inversely proportional to the area.
7. The device of claim 1 wherein the top wiring structure and the bottom wiring structure are spatially arranged in a crossbar configuration.
8. The device of claim 1 wherein the substrate is a semiconductor substrate.
9. The device of claim 1 wherein the substrate comprises one or more COMS device formed thereon, the one or more CMOS devices being operably coupled to the switching device.
10. The device of claim 1 wherein at least a portion of the top wiring structure and at least a portion of the bottom wiring structure comprise a metal material selected from a group consisting of: tungsten, copper, and aluminum.
11. The device of claim 1 wherein the contact material comprises a polysilicon material having a p+ impurity characteristic, the p+ impurity characteristic being provided by a boron species at a concentration ranging from about 10 17 cm 3 to about 10 21 cm 3 .
12. The device of claim 1 wherein the polysilicon material has a thickness ranging from about 50 Angstroms to about 2000 Angstroms.
13. The device of claim 1 wherein the polysilicon material has a thickness ranging from about 100 Angstroms to about 500 Angstroms.
14. The device of claim 1 wherein the switching material comprises an amorphous silicon material having an intrinsic semiconductor characteristic.
15. The device of claim 14 wherein the amorphous silicon material has a thickness ranging from about 50 Angstroms to about 2000 Angstroms.
16. The device of claim 14 wherein the amorphous silicon material has a thickness ranging from about 100 Angstroms to about 500 Angstroms.
17. The device of claim 1 wherein the conductive material is a metal material selected from a group consisting of: gold, silver, platinum, and palladium.
18. The device of claim 17 wherein the conductive material comprises a silver material having a thickness ranging from about 50 Angstroms to about 2000 Angstroms.
19. The device of claim 17 wherein the conductive material comprises a silver material having a thickness ranging from about 100 Angstroms to about 500 Angstroms.