Metal deposit process
Method and system for controllable deposit of copper onto an exposed surface of a workpiece, such as a semiconductor surface. A seed thickness of copper is optionally deposited onto the exposed surface, preferably using oxygen-free liquid ammonia to enhance this deposition. The workpiece exposed surface is then immersed in an electroplating solution, including copper and liquid ammonia at a suitable pressure and temperature, and copper is caused to plate onto the exposed surface at a controllable rate. When the copper deposited on the exposed surface reaches a selected total thickness, electroplating is discontinued, the electroplating solution is removed, and the gaseous and liquid ammonia are recovered and recycled for re-use.
1. A method for controllable deposit of a metal on a surface of an object, the method comprising:
contacting an electroplating solution including a selected metal and liquid ammonia (NH 3 ) with an exposed surface of a selected object; and
causing the selected metal in the electroplating solution to deposit on the exposed surface of the selected object until a selected thickness of the selected metal has been deposited on the exposed surface of the object.
2. The method of claim 1 wherein said metal is selected from a group of metals consisting of Cu, Ag, Au, Ni, Pd, Pt, Fe, Co, Zn and Cd.
3. The method of claim 1 where the electroplating deposit process is performed at a temperature ranging from −78° Celcius to 90° Celcius.
4. The method of claim 1 wherein the electroplating deposit process is performed at a temperature of 20° Celcius.
5. The method of claim 4 wherein the electroplating deposit process is performed at a pressure of 150 psig.
6. The method of claim 1 further comprising removing the remaining electroplating solution and rinsing the exposed surface of the object in liquid ammonia when a second selected thickness of the selected metal has been deposited on the object exposed surface.
7. The method of claim 1 further comprising choosing Cu as said selected metal.
8. The method of claim 1 further comprising choosing said object to include a semiconductor material.
9. The method of claim 1 wherein causing the selected metal in the electroplating solution to deposit on the exposed surface of the selected object occurs at a selected rate.
10. The method of claim 1 further comprising rotating said object about an axis that is transverse to said object surface during at least a portion of said electroplating deposit process.
11. The method of claim 1 further comprising providing an electrically conducting plate within the electroplating solution.
12. The method of claim 11 further comprising providing a selected voltage difference ΔV between the exposed surface of the object and the electrically conducting plate of Δt least about 0.3 volts for a time interval of selected length At in a range of 15 sec≦Δt≦300 sec.
13. A method for controllable deposit of a metal on a surface of a object, the method comprising:
using electroless deposition to provide a thickness of copper metal on an exposed surface of a selected object wherein the process of electroless deposition of the metal on the object exposed surface comprises:
contacting the exposed surface of the object with a fluid that includes a mixture of liquid ammonia and a selected electroless electrolyte including a selected metal; and
allowing a portion of the selected metal in the electroless electrolyte to deposit on the exposed surface of the object.
14. The method of claim 13 wherein the electroless electrolyte is a copper halide.
15. The method of claim 13 wherein the electroless electrolyte is a copper amine.
16. The method of claim 13 further comprising adding a reducing agent.
17. The method of claim 13 where the electroless deposition process is performed at a temperature ranging from −78° Celcius to 90° Celcius and at a pressure ranging from 0 to 350 psig.
18. The method of claim 13 wherein the electroless deposition process is performed at a temperature of 20° Celcius.
19. The method of claim 18 wherein the electroless deposition process is performed at pressure of 150 psig.
20. A method for controllable deposit of a metal on a surface of a object, the method comprising:
using electroless deposition to provide a seed thickness of a selected metal on an exposed surface of a selected object; and
contacting an electroplating solution including the selected metal and liquid ammonia with the exposed surface of the selected object; and
causing the selected metal in the electroplating solution to deposit on the exposed surface of the selected object.
21. The method of claim 20 where the metal is selected from a group of metals consisting of Cu, Ag, Au, Ni, Pd, Pt, Fe, Co, Zn and Cd.
22. The method of claim 20 wherein electroless deposition of the metal on the exposed surface of the object comprises:
contacting the exposed surface of the object with a fluid that includes a mixture of liquid ammonia and a copper halide or a copper amine; and
allowing a portion of the copper in the copper halide or copper amine to deposit on the exposed surface of the object.
23. The method of claim 22 further comprising performing said electroless deposition process at a pressure p in a selected range 0 psig≦p≦350 psig and at a selected temperature T in the range −78° Celcius≦T≦90° Celcius.
24. The method of claim 22 wherein said electroless deposition occurs at a temperature of 20° Celcius.
25. The method of claim 24 wherein said pressure is 150 psig.
26. A method for controllable deposit of a metal on a surface of a wafer, the method comprising:
contacting an electroplating solution including a selected metal and liquid ammonia (NH 3 ) with an exposed surface of a selected semiconductor material; and
causing the selected metal in the electroplating solution to deposit on the exposed surface of the selected semiconductor material.
27. The method of claim 26 wherein the metal is selected from a group of metals consisting of Cu, Ag, Au, Ni, Pd, Pt, Fe, Co, Zn and Cd.
28. The method of claim 26 further comprising providing an electrically conducting plate within the electroplating solution.
29. The method of claim 28 further comprising providing a selected voltage difference ΔV between the exposed surface of the wafer and the electrically conducting plate of at least about 0.3 volts for a time interval of selected length Δt in a range 15 sec≦Δt≦300 sec.
30. The method of claim 26 wherein said semiconductor material is a wafer.
31. The method of claim 26 wherein said selected semiconductor material includes a circuit.
32. The method of claim 31 further comprising generating a surface comprised of said selected metal in the circuit of the selected semiconductor material.
33. The method of claim 31 further comprising generating a contact comprised of said selected metal in the circuit of the selected semiconductor material.
34. The method of claim 26 further comprising generating surface comprised of said selected metal in the selected semiconductor material.
35. The method of claim 26 further comprising generating a contact comprised of said selected metal in the selected semiconductor material.