Front-end processing of nickel plated bond pads
View Patent ↗A front-end method of fabricating nickel plated caps over copper bond pads used in a memory device. The method provides protection of the bond pads from an oxidizing atmosphere without exposing sensitive structures in the memory device to the copper during fabrication.
1. A method of forming a memory device, the method comprising:
forming a circuit over a semiconductor substrate;
forming at least one first insulating layer over said circuit;
forming a conductive bond pad within said at least one first insulating layer which is connected to said circuit;
forming at least one second insulating layer over said bond pad;
forming an opening in said at least one second insulating layer over said bond pad;
forming a conductor over said bond pad; and
forming memory cells over said at least one second insulating layer after said conductor is formed.
2. The method of claim 1 , wherein the bond pad comprises copper.
3. The method of claim 1 , wherein the step of forming a conductor over said bond pad comprises forming a nickel cap.
4. The method of claim 3 , wherein said step of forming a nickel cap comprises plating nickel over said bond pad.
5. The method of claim 4 , wherein the step of forming a nickel cap comprises performing an electroless nickel bath emersion.
6. The method of claim 5 , wherein said step of performing an electroless nickel solution comprises a nickel salt and a reducing agent.
7. The method of claim 6 , wherein the temperature of the bath is maintained at or below approximately 80 degrees Celsius.
8. The method of claim 3 , wherein said step of forming a nickel cap comprises forming a layer of nickel having a thickness of about 4000 Angstroms.
9. The method of claim 1 , wherein said step of forming at least one first insulating layer comprises forming an oxide layer.
10. The method of claim 9 , wherein said step of forming at least one second insulating layer comprises forming a nitride layer over the oxide layer.
11. The method of claim 1 , wherein the memory cells are resistance variable memory cells.
12. The memory cell of claim 11 , wherein the memory cells are PCRAM memory cells.
13. The method of claim 12 , wherein the step of forming said memory cells comprises forming at least one layer of germanium selenide glass.
14. The method of claim 13 , wherein the step of forming said memory cells further comprises forming at least one layer comprising silver in communication with said at least one layer of germanium selenide glass.
15. The method of claim 1 , further comprising the step of forming an electrode layer over the memory cells.
16. The method of claim 1 , further comprising the step of forming at least one conductive path through said at least one first and second insulating layers.
17. The method of claim 16 , wherein the step of forming at least one conductive path comprises forming a conductive via filled with tungsten.