Top electrode for device structures in interconnect
Some embodiments relate to an integrated circuit device. The integrated circuit device includes a resistive random access memory (RRAM) cell, which includes a top electrode and a bottom electrode that are separated by a RRAM dielectric layer. The top electrode of the RRAM cell has a recess in its upper surface. A via is disposed over the RRAM cell and contacts the top electrode within the recess.
1. A device structure arranged within an interconnect structure over a semiconductor substrate, the device structure comprising:
a lower electrode disposed over the semiconductor substrate and over a lowermost conductive layer in the interconnect structure;
an upper electrode disposed over the lower electrode and having an upper surface that exhibits a u-shaped or v-shaped cross-section;
a u-shaped or v-shaped dielectric layer separating the lower electrode from the upper electrode; and
a conductive via in electrical contact with the upper electrode, the via having lower via sidewalls that contact inner sidewalls of the u-shaped or v-shaped cross-section.
2. The device structure of claim 1 , further comprising:
a blocking layer arranged under the via and contacting an inner upper surface of the u-shaped or v-shaped cross-section.
3. The device structure of claim 1 , wherein the device structure is disposed over a metal interconnect layer which is disposed over the semiconductor substrate, the device structure further comprising:
an etch stop layer disposed over the metal interconnect layer, wherein the etch stop layer has a hole through it; and
wherein the device structure is disposed over the hole and is wider than the hole.
4. The device structure of claim 3 , wherein the upper surface of the device structure is recessed in an area over the hole.
5. The device structure of claim 1 , wherein the upper electrode comprises:
a peripheral upper electrode portion having a peripheral upper surface; and
a central upper electrode portion circumscribed by the peripheral upper electrode portion, the central upper electrode portion having a central upper surface that is recessed relative to the peripheral upper surface.
6. The device structure of claim 5 , wherein the device structure further comprises:
sidewall spacers disposed over the lower electrode and along outer sidewalls of the peripheral upper electrode portion.
7. The device structure of claim 5 , wherein the via has outer via sidewalls that directly contact inner sidewalls of the upper electrode which extend downwardly from the peripheral upper surface to the central upper surface.
8. The device structure of claim 7 , further comprising:
a blocking layer arranged under the via and having a bottom surface that contacts the central upper surface of the upper electrode, the blocking layer having outer sidewalls that contact the inner sidewalls of the upper electrode.
9. The device structure of claim 5 , wherein the central upper electrode portion has a first thickness and the peripheral upper electrode portion has a second thickness that is greater than the first thickness.
10. The device structure of claim 9 , wherein the first thickness is half of or less than half of the second thickness.
11. A device structure arranged within an interconnect structure over a semiconductor substrate, the device structure comprising:
a lower electrode disposed over the semiconductor substrate and over a lowermost conductive layer in the interconnect structure;
a dielectric layer disposed over the lower electrode;
an upper electrode disposed over the dielectric layer and having an upper surface that exhibits a u-shaped or v-shaped cross-section;
a via in electrical contact with the upper electrode, the via having outer via sidewalls that contact inner sidewalls of the u-shaped or v-shaped cross-section; and
a blocking structure arranged between a lower portion of the via and a bottom inner surface of the u-shaped or v-shaped cross-section;
wherein the device structure is disposed over a metal interconnect layer which is disposed over the semiconductor substrate, the device structure further comprising:
an etch stop layer disposed over the metal interconnect layer, wherein the etch stop layer has a hole through it; and
wherein the device structure is disposed over the hole and is wider than the hole.
12. The device structure of claim 11 , wherein the device structure is a memory cell.
13. The device structure of claim 11 , wherein the lower electrode has a first thickness ranging from 20 angstroms to 200 angstroms, the dielectric layer has a second thickness ranging from 30 angstroms to 70 angstroms, and the upper electrode has a third thickness ranging from 100 angstroms to 400 angstroms.
14. The device structure of claim 13 :
wherein the lower electrode comprises: Al, Ti, Ta, Au, Pt, W, Ni, Ir, or Cu;
wherein the dielectric layer is a transitional metal oxide; and
wherein the upper electrode comprises: Al, Ti, Ta, Au, Pt, W, Ni, Ir, or Cu.
15. The device structure of claim 11 , wherein the upper electrode comprises:
a peripheral upper electrode portion having a peripheral upper surface; and
a central upper electrode portion having a central upper surface that is recessed relative to the peripheral upper surface.
16. The device structure of claim 15 , wherein the via has outer via sidewalls that directly contact inner sidewalls of the upper electrode which extend downwardly from the peripheral upper surface to the central upper surface.
17. The device structure of claim 15 , wherein the central upper electrode portion has a first thickness and the peripheral upper electrode portion has a second thickness that is greater than the first thickness.
18. A device structure arranged within an interconnect structure over a semiconductor substrate, the device structure comprising:
a lower electrode disposed over the semiconductor substrate and over a lowermost conductive layer in the interconnect structure, the lower electrode having a first width as measured between its outermost sidewalls;
a dielectric layer disposed over the lower electrode;
an upper electrode disposed over the dielectric layer and having an upper surface that exhibits a u-shaped or v-shaped cross-section, the upper electrode comprising a central upper electrode portion having a first thickness and a peripheral upper electrode portion having a second thickness that is greater than the first thickness; and the upper electrode having a second width as measured between its outermost sidewalls, the second width being less than the first width;
a via in electrical contact with the upper electrode, the via having outer via sidewalls that contact inner sidewalls of the u-shaped or v-shaped cross-section; and
a sidewall spacer structure disposed over an upper surface of the lower electrode and about the outermost sidewalls of the upper electrode, the sidewall spacer structure spanning a lateral distance that is substantially equal to the first width minus the second width.
19. The device structure of claim 18 , further comprising:
a blocking layer arranged under a bottom surface of the via and making contact with lower portions of the inner sidewalls of the u-shaped or v-shaped cross-section.
20. The device structure of claim 18 :
wherein the lower electrode comprises: Al, Ti, Ta, Au, Pt, W, Ni, Ir, or Cu;
wherein the dielectric layer is a transitional metal oxide; and
wherein the upper electrode comprises: Al, Ti, Ta, Au, Pt, W, Ni, Ir, or Cu.