Memory device having via landing protection
A memory cell with a hard mask and a sidewall spacer of different material is provided. The memory cell may be manufactured by a method comprising forming a multi-layer stack and patterning the same to form the hard mask layer, the top electrode layer and the switching dielectric layer to form a hard mask, a top electrode and a switching dielectric. A sidewall spacer is formed alongside the hard mask, the top electrode, and the switching dielectric with a material different than the hard mask. The bottom electrode layer is patterned according to the sidewall spacer to form a bottom electrode. A dielectric layer is formed surrounding the bottom electrode, the sidewall spacer and overlying the hard mask. An etch is performed followed by a conductive material filling to form a top electrode via extending through the dielectric layer and the hard mask to reach on the top electrode.
1. A method for manufacturing a memory cell, the method comprising:
forming a multi-layer stack comprising a bottom electrode layer, a switching dielectric layer over the bottom electrode layer, a top electrode layer over the switching dielectric layer, and a hard mask layer over the top electrode layer;
patterning the hard mask layer, the top electrode layer and the switching dielectric layer to form a hard mask, a top electrode and a switching dielectric;
forming a sidewall spacer layer along an outer contour of the bottom electrode layer, the switching dielectric, the top electrode, and the hard mask;
performing a first etch to the sidewall spacer layer to expose the hard mask and to form a sidewall spacer alongside the hard mask, the top electrode, and the switching dielectric, wherein the sidewall spacer is formed of a material different than the hard mask;
performing a second etch to the bottom electrode layer with the sidewall spacer in place to form a bottom electrode;
forming a dielectric layer surrounding the bottom electrode, the sidewall spacer and overlying the hard mask; and
performing an etch followed by a conductive material filling to form a top electrode via extending through the dielectric layer and the hard mask to reach the top electrode.
2. The method of claim 1 , wherein the etch has an etching rate ratio for the hard mask and the sidewall spacer in a range of from 1:3 to 1:10.
3. The method of claim 1 , wherein the top electrode via is formed contacting the sidewall spacer at a position vertically between a top surface and a bottom surface of the hard mask.
4. The method of claim 1 , wherein the dielectric layer is formed directly contacting the sidewall spacer and the hard mask.
5. The method of claim 1 , wherein the top electrode via is formed directly interfacing a top surface of the sidewall spacer below a top surface of the hard mask.
6. The method of claim 1 , wherein the sidewall spacer is formed to have a top surface higher than that of the top electrode.
7. The method of claim 1 , wherein forming the multi-layer stack further comprises:
prior to patterning the hard mask layer, the top electrode layer and the switching dielectric layer, forming patterning layers over the hard mask layer for patterning the memory cell, the patterning layers comprising a conductive layer over the hard mask layer and one or more hard mask materials over the conductive layer.
8. The method of claim 7 , wherein the conductive layer is comprised of copper, titanium (Ti), tantalum (Ta), titanium nitride (TiN), or tantalum nitride (TaN).
9. The method of claim 7 , wherein the one or more hard mask materials is comprised of one or more of an advanced pattern film (APF) and/or silicon oxynitride (SiON).
10. The method of claim 7 , wherein the conductive layer is removed from the multi-layer stack when forming the sidewall spacer and/or the bottom electrode.
11. A method for manufacturing a memory cell, the method comprising:
forming a multi-layer stack comprising a bottom electrode layer, a switching dielectric layer over the bottom electrode layer, a top electrode layer over the switching dielectric layer, and a hard mask layer over the top electrode layer;
forming a conductive layer over the hard mask layer and one or more hard mask materials over the conductive layer;
patterning the hard mask layer, the top electrode layer and the switching dielectric layer using the one or more hard mask materials to form a hard mask, a top electrode and a switching dielectric;
forming a sidewall spacer alongside the hard mask, the top electrode, and the switching dielectric, wherein the sidewall spacer is formed of a material different than the hard mask, and wherein the topmost surface of the sidewall spacer directly contacts a sidewall of the hard mask and is located lower than a top surface of the hard mask; and
patterning the bottom electrode layer according to the sidewall spacer to form a bottom electrode;
forming a dielectric layer surrounding the bottom electrode, the sidewall spacer and overlying the hard mask; and
performing an etch followed by a conductive material filling to form a top electrode via extending through the dielectric layer and the hard mask to reach the top electrode.
12. The method of claim 11 , wherein the top electrode via is made to have the entire interface with the sidewall spacer lower than the top surface of the hard mask.
13. The method of claim 11 , wherein the conductive layer is removed to expose the hard mask when forming the sidewall spacer and/or the bottom electrode.
14. The method of claim 11 , wherein the etch has an etching rate ratio for the hard mask and the sidewall spacer in a range of from 1:3 to 1:10.
15. The method of claim 11 , wherein the top electrode via is formed directly contacting the sidewall spacer at a position vertically between the stop surface and a bottom surface of the hard mask.
16. The method of claim 11 , wherein the dielectric layer is formed directly contacting the sidewall spacer and the hard mask.
17. A method for manufacturing a memory cell, the method comprising:
forming a bottom electrode, a switching dielectric, and a top electrode one stacked over another over a substrate, the switching dielectric having a variable resistance;
forming a hard mask over the top electrode;
forming a sidewall spacer extending upwardly along sidewalls of the switching dielectric, the top electrode, and the hard mask;
forming a dielectric layer over the substrate, along and directly contacting sidewalls of the sidewall spacer, and overlying the hard mask; and
forming a top electrode via extending through the dielectric layer and the hard mask to reach the top electrode, wherein the top electrode via is made to have the entire interface with the sidewall spacer lower than a top surface of the hard mask.
18. The method of claim 17 , wherein the hard mask is made of silicon carbide and the sidewall spacer is made of silicon nitride.
19. The method of claim 17 , wherein a top the topmost surface of the sidewall spacer directly contacts the sidewall of the hard mask and is located lower than the top surface of the hard mask.
20. The method of claim 17 , wherein the top surface of the hard mask directly contacts the dielectric layer.