WAFER LEVEL ELECTROLESS COPPER METALLIZATION AND BUMPING PROCESS, AND PLATING SOLUTIONS FOR SEMICONDUCTOR WAFER AND MICROCHIP
(19)AUSTRALIAN PATENT OFFICE (54) Title WAFER LEVEL ELECTROLESS COPPER METALLIZATION AND BUMPING PROCESS, AND PLATING SOLUTIONS FOR SEMICONDUCTOR WAFER AND MICROCHIP (51)6 International Patent Classification(s) HOI L 021/60 HOI L 023/538 HOI L 023/488 (21) Application No: 2003269066 (22) Application Date: 2003.05.14 (87) WIPONo: WO03/098681 (30) Priority Data (31) Number (32) Date 60/378,049 2002.05.16 (33) Country US (43) Publication Date : 2003.12.02 (43) Publication Journal Date : 2004.01.29 (71) Applicant(s) NATIONAL UNIVERSITY OF SINGAPORE (72) Inventor(s) LU, Haijing; GONG, Hao; WONG, Chee , Khuen, Stephen (H) Application NoAU2003269066 A1(19)AUSTRALIAN PATENT OFFICE (54) Title WAFER LEVEL ELECTROLESS COPPER METALLIZATION AND BUMPING PROCESS, AND PLATING SOLUTIONS FOR SEMICONDUCTOR WAFER AND MICROCHIP (51)6 International Patent Classification(s) HOI L 021/60 HOI L 023/538 HOI L 023/488 (21) Application No: 2003269066 (22) Application Date: 2003.05.14 (87) WIPONo: WO03/098681 (30) Priority Data (31) Number (32) Date 60/378,049 2002.05.16 (33) Country US (43) Publication Date : 2003.12.02 (43) Publication Journal Date : 2004.01.29 (71) Applicant(s) NATIONAL UNIVERSITY OF SINGAPORE (72) Inventor(s) LU, Haijing; GONG, Hao; WONG, Chee , Khuen, Stephen A process is used to produce copper bumps on a semiconductor chip or a wafer containing several microchips. The chip or wafer has a layer incorporating a plurality semiconductor devices and a passivation layer having openings. Conductive pads within the openings and are in contact with the semiconductor devices. In the process, a conductive adhesive material is deposited onto the conductive pads to form adhesion layers. A conductive metal is deposited onto the adhesion layers to form barrier layers and the passivation layer is subjected to an acid dip solution to remove particles of the conductive adhesive material which can be attached to the passivation layer. Copper is then deposited onto the barrier layers to form the copper bump. Each one of the deposition steps are performed electrolessly. Furthermore, plating solutions and a wafer and a microchip produced by the above process and are provided. WE CLAIM: 1. A process for producing copper bumps on a semiconductor wafer incorporating a plurality of semiconductor devices, the semiconductor wafer also having a passivation layer having openings and conductive pads, within the openings, in contact with the semiconductor devices, the process comprising the steps of: performing electroless deposition of a conductive adhesive material onto the conductive pads to form adhesion layers ; performing electroless deposition of a conductive metal onto the adhesion layers to form barrier layers; subjecting the passivation layer to an acid dip solution to remove any particles containing at least one of the conductive adhesive material and the conductive metal, which may be attached to the passivation layer ; and performing electroless deposition of Copper onto the barrier layers to form the copper bumps.
2. A process according to claim 1 comprising applying a resist on a backside of the semiconductor wafer prior to the step of performing electroless deposition of a conductive adhesive material onto the conductive pads to form adhesion layers.
3. A process according to claim 1 or 2 comprising removing oxidation layers on the conductive pads using an alkaline cleaner prior to the step of performing electroless deposition of a conductive adhesive material onto the conductive pads to form adhesion layers. <Desc/Clms Page number 24> 4. A process according to anyone of claims 1 to 3 wherein the step of performing electroless deposition of a conductive adhesive material onto the conductive pads to form adhesion layers comprises electrolessly depositing Zinc onto the conductive pads.
5. A process according to claim 4 wherein the electrolessly depositing Zinc onto the conductive pads comprises immersing the semiconductor wafer in an adhesive plating solution containing Zn++ (Zinc++) ions and allowing the Zn++ ions to absorb onto the conducting pads in a reaction with Al (Aluminium), the conductive pads comprising Al.
6. A process according to anyone of claims 1 to 5 wherein the step of performing electroless deposition of a conductive metal onto the adhesion layers to form barrier layers comprises electrolessly depositing Pd (Palladium) onto the adhesion layers.
7. A process according to anyone of claims 1 to 5 wherein the step of performing electroless deposition of a conductive metal onto the adhesion layers to form barrier layers comprises electrolessly depositing Ni (Nickel) onto the adhesion layers.
8. A process according to claim 6 wherein the electrolessly depositing Pd onto the adhesion layers comprises immersing the semiconductor wafer in a barrier plating solution containing Pd++ ions and allowing the Pd++ ions to absorb onto the adhesive layers by reacting with Zn, the adhesion layers comprising Zn.
9. A process according to claim 6 wherein the electrolessly depositing Pd onto the adhesion layers comprises immersing the semiconductor wafer in a barrier plating solution <Desc/Clms Page number 25> containing a reducing agent for electrolessly depositing additional Pd onto the adhesion layers in a follow-up reaction.
10. A process according to anyone of claims 1 to 9 wherein the step of subjecting the passivation layer to an acid dip solution to remove any particles containing at least one of the conductive adhesive material and the conductive metal, which may be attached to the passivation layer comprises subjecting the passivation layer to the acid dip solution wherein the acid dip solution contains a Sulfate Acid or a Nitric Acid.
11. A process according to anyone of claims 1 to 9 wherein the step of subjecting the passivation layer to an acid dip solution to remove any particles containing at least one of the conductive adhesive material and the conductive metal, which may be attached to the passivation layer comprises subjecting the passivation layer to the acid dip solution to depress any active centers that may be present on the passivation layer.
12. A process according to anyone of claims 1 to 11 wherein the step of performing electroless deposition of Copper onto the barrier layers to form the copper bumps comprises immersing the semiconductor wafer in a copper plating solution containing copper ions, one of Sodium Hydroxide and Potassium Hydroxide, a complexing agent and a reducing agent.
13. A process according to anyone of claims 1 to 12 further comprising performing electroless deposition of an anti-tarnish chemical to produce a cap layer over the copper bumps and the passivation layer.
14. A semiconductor chip incorporating a plurality of semiconductor devices, the semiconductor chip also having a <Desc/Clms Page number 26> passivation layer having openings and conductive pads, within the openings, in contact with the semiconductor devices for providing contacts between the semiconductor devices and outside circuitry, within each one of the openings the semiconductor chip comprising: an adhesion layer of a conductive adhesive material in contact with a respective one of the conducting pads ; a barrier layer of a conductive metal in contact with the adhesion layer ; and a layer of Copper in contact with the barrier layer, the layer of Copper forming a copper bump.
15. A semiconductor chip according to claim 14 wherein the conducting pads comprise Aluminium.
16. A semiconductor chip according to claim 14 wherein the adhesion layer comprises Zinc.
17. A semiconductor chip according to claim 16 wherein the barrier layer comprises Palladium or Nickel.
18. A semiconductor chip according to claim 14 wherein the conducting pads comprise Aluminium, the adhesion layer comprises Zinc and the barrier layer comprises Palladium or Nickel.
19. A semiconductor wafer comprising a plurality of semiconductor chips according to the semiconductor chip of anyone of claims 14 to 18.
20. A plating solution for electrolessly depositing Copper onto a layer of Nickel or Palladium, the plating solution comprising: <Desc/Clms Page number 27> Copper ions for a reaction with the Nickel or Palladium for deposition of Copper ; and an alkaline, a complexing agent and a reducing agent for additional deposition of the Copper in a follow-up reaction.
21. A plating solution according to claim 20 comprising Copper Sulfate or Copper Surphonamides for providing the Copper ions in the plating solution.
22. A plating solution according to claim 20 or 21 wherein the alkaline comprises Sodium Hydroxide or Potassium Hydroxide.
23. A plating solution according to anyone of claims 20 to 22 comprising a surface control agent for providing a smooth surface of the Copper being deposited.
24. A plating solution according to claim 23 wherein the surface control agent comprises Tetramethylammonium and 2, 2'- dipyridyl.
25. A plating solution according to anyone of claims 20 to 24 wherein the complexing agent is EDTA-2Na and the reducing agent is Formaldehyde.
26. A plating solution for electrolessly depositing a layer of Nickel or Palladium onto a layer of Zinc, the plating solution comprising: Nickel or Palladium ions for a reaction with the Zinc for deposition of the Nickel or Palladium ; and a reducing agent for additional deposition of the Nickel or Palladium in a follow-up reaction. <Desc/Clms Page number 28> 27. A plating solution according to claim 26 comprising Nickel Chloride or Nickel Sulfate to provide the Nickel ions.
28. A plating solution according to claim 26 comprising Palladium Chloride or Palladium Sulfate to provide the Palladium ions.
29. A plating solution according to anyone of claims 26 to 28 comprising Ammonium Chloride, Ammonia and Hydrogen Chloride.
30. A plating solution according to anyone of claims 26 to 29 wherein the reducing agent comprises Sodium Phosphinate Monohydrate.