Memory cell that includes a carbon-based reversible resistance switching element compatible with a steering element, and methods of forming the same
View Patent ↗Memory cells, and methods of forming such memory cells, are provided that include a steering element coupled to a carbon-based reversible resistivity switching material that has an increased resistivity, and a switching current that is less than a maximum current capability of the steering element used to control current flow through the carbon-based reversible resistivity switching material. In particular embodiments, methods and apparatus in accordance with this invention form a steering element, such as a diode, having a first width, coupled to a reversible resistivity switching material, such as aC, having a second width smaller than the first width.
1. A method of forming a memory cell, the method comprising:
forming a steering element having a first width;
forming a silicide-forming metal adjacent the steering element;
forming a reversible resistance switching element coupled to the steering element;
forming a masking feature;
shrinking the masking feature to a width less than the first width;
reducing a width of the reversible resistance switching element to a second width substantially equal to the shrunken masking feature width by employing the shrunken mask feature;
forming a hard mask above the reversible resistance switching element;
using the shrunken masking feature to pattern and etch the hard mask to a width substantially equal to the shrunken masking feature width; and
forming a liner on exterior surfaces of the hard mask and the reduced-width reversible resistance switching element, so that a width of the hard mask, reversible resistance switching element and liner substantially equals the first width,
wherein reducing comprises using the etched hard mask to pattern and etch the reversible resistance switching element to the second width.
2. The method of claim 1 , wherein the masking feature comprises photoresist.
3. The method of claim 2 , wherein shrinking comprises using an oxygen plasma to shrink the photoresist masking feature.
4. The method of claim 1 , wherein reducing comprises using the shrunken masking feature to pattern and etch the reversible resistance switching element to the second width.
5. The method of claim 1 , further comprising using the liner, hard mask and reversible resistance switching element to pattern and etch the steering element to the first width.
6. The method of claim 1 , wherein forming the steering element comprises forming a p-n or p-i-n diode.
7. The method of claim 1 , wherein the first width comprises a minimum photolithography feature size of a semiconductor process.
8. The method of claim 1 , wherein the first width between about 10 nanometers to about 100 nanometers.
9. The method of claim 1 , wherein the first width is between about 10 nanometers to about 50 nanometers.
10. The method of claim 1 , wherein the first width is about 43 nanometers.
11. The method of claim 1 , wherein the reversible resistance switching element comprises amorphous carbon.
12. The method of claim 1 , wherein the second width is between about 5 nanometers to about 50 nanometers.
13. The method of claim 1 , wherein the second width is between about 5 nanometers to about 20 nanometers.
14. The method of claim 1 , wherein the second width is about 19 nanometers.
15. A memory cell formed using the method of claim 1 .
16. A method of forming a memory cell, the method comprising:
forming a steering element having a first width;
forming a silicide-forming metal adjacent the steering element;
forming a cavity adjacent the steering element, wherein the cavity has a width smaller than the first width; and
using the cavity to form a reversible resistance switching element coupled to the steering element, wherein the reversible resistance switching element has a second width substantially equal to the cavity width,
wherein forming a cavity comprises:
forming a sacrificial layer adjacent the steering element;
patterning and etching the sacrificial layer and the steering element to the first width;
forming a dielectric layer adjacent the etched sacrificial layer and steering element;
removing the sacrificial layer to form a void in the dielectric layer; and
forming a liner inside the void to form the cavity.
17. The method of claim 16 , wherein forming the liner comprises forming a liner having a bottom portion adjacent a bottom of the void and sidewall portions adjacent sidewalls of the void.
18. The method of claim 17 , wherein the liner further comprises removing the bottom portion of the liner.
19. The method of claim 18 , further comprising forming the reversible resistance switching element between the sidewall portions of the liner.