Crossbar resistive memory array with highly conductive copper/copper alloy electrodes and silver/silver alloys electrodes
Embodiments of the present invention provide systems and methods for the fabrication of a crossbar array fabrication of resistive random access memory (RRAM) cells. The array structure contains large grain copper and its alloy or silver and its alloy. A metal cap and spacer are used to protect copper or silver from chemical modifications during memory cell patterning.
1. A method comprising:
depositing a first electrode, a first metal cap, a first metal film, and a first hardmask (HM) on a silicon surface, wherein the deposited first metal film contains one or more crystal grains, wherein the one or more crystal grains in the first metal film contain a plurality of respective grain boundaries;
increasing respective sizes of the plurality of respective grain boundaries in the one or more crystal grains in the first metal film by subtractive etching;
forming a resistive random access memory (RRAM) cell, wherein the RRAM cell contains a critical dimension that is inversely proportional to a diameter of each respective crystal grains in the first metal film;
depositing the RRAM cell over the deposited first electrode;
depositing a second electrode, a second metal cap, a second metal film, and a second hardmask (HM) over the deposited RRAM cell, wherein the second metal film contains one or more crystal grains, wherein a diameter of each of the one or more crystal grains of the second film corresponds inversely to the critical dimension of the RRAM cell; and
depositing a spacer over the second HM.
2. The method of claim 1 , wherein depositing the first electrode, the first metal cap, the first metal film, and the first HM, comprises:
etching the deposited first HM; and
etching the deposited first electrode.
3. The method of claim 2 , further comprising:
etching the deposited first metal cap; and
etching the deposited first metal film.
4. The method of claim 3 , further comprising:
coating a trench with a first dielectric material; and
implementing chemical mechanical planarization (CMP) on the first dielectric layer.
5. The method of claim 1 , wherein depositing the second electrode, the second metal cap, the second metal film, and the second HM, comprises:
patterning the deposited second HM.
6. The method of claim 5 , further comprising:
patterning the deposited second metal film; and
patterning the deposited second metal cap.
7. The method of claim 1 , further comprising:
providing a protective layer by etching the spacer, wherein the spacer has a thickness between 1 nm to 20 nm.
8. The method of claim 7 , further comprising:
coating with a second dielectric material around the etched spacer; and
implementing CMP on: the second dielectric material and the etched spacer.
9. The method of claim 1 , wherein the one or more crystal grains in the first metal film and the second metal film, comprises:
performing a planarization process on a metal layer in the first electrode and on a metal layer in the second electrode, wherein the planarization process sets a thickness of the metal layer in the first electrode and a thickness of the metal layer in the second electrode equal to an average grain size of the one or more crystal grains in the first metal film and second metal film.