Top layers of metal for integrated circuits
View Patent ↗The present invention adds one or more thick layers of polymer dielectric and one or more layers of thick, wide metal lines on top of a finished semiconductor wafer, post-passivation. The thick, wide metal lines may be used for long signal paths and can also be used for power buses or power planes, clock distribution networks, critical signal, and re-distribution of I/O pads.
1. A method for forming a wirebond and a post-passivation metallization system for an integrated circuit, comprising:
providing a silicon substrate, a MOS device in and on said silicon substrate, a first metallization structure over said silicon substrate, wherein said first metallization structure comprises a first metal layer and a second metal layer over said first metal layer, a dielectric layer between said first and second metal layers, and a passivation layer over said first metallization structure and over said dielectric layer;
forming a first polymer layer on said passivation layer, wherein said forming said first polymer layer comprises depositing a photosensitive polymer on said passivation layer;
forming a second metallization structure over said first polymer layer, wherein said second metallization structure comprises a metal line having a sheet resistance smaller than 7 milliohms per square, and wherein said forming said second metallization structure comprises forming a first adhesion/barrier layer over said first polymer layer, forming a first gold layer on said first adhesion/barrier layer, performing a photolithography process to form a photoresist layer on said first gold layer, an opening in said photoresist layer exposing said first gold layer, wherein said photoresist layer has a thickness between 2 and 100 micrometers and wherein said performing said photolithography process comprises using a 1X stepper or aligner, electroplating a second gold layer having a thickness between 2 and 100 micrometers on said first gold layer exposed by said opening in said photoresist layer, removing said photoresist layer, removing said first gold layer not under said second gold layer, and removing said first adhesion/barrier layer not under said second gold layer; and
wirebonding to a contact point of said second metallization structure, wherein said contact point is directly over said polymer layer and directly over said MOS device.
2. The method of claim 1 , wherein said first metallization structure comprises a damascene copper and a second adhesion/barrier layer under said damascene copper and at a sidewall of said damascene copper.
3. The method of claim 1 , wherein said passivation layer comprises a nitride layer having a thickness greater than 0.3 micrometers.
4. The method of claim 1 , wherein said passivation layer comprises an oxide layer and a nitride layer over said oxide layer.
5. The method of claim 1 , wherein said second metallization structure connects multiple separate portions of said first metallization structure.
6. The method of claim 1 , wherein said forming said first adhesion/barrier layer comprises sputtering a titanium-tungsten-alloy layer with a thickness between 0.01 and 3 micrometers over said first polymer layer.
7. The method of claim 1 , further comprising forming a polymer layer over said second metallization structure.
8. The method of claim 1 , wherein said forming said first gold layer comprises sputtering said first gold layer with a thickness between 0.05 and 3 micrometers on said first adhesion/barrier layer.
9. The method of claim 1 , wherein said forming said first gold layer comprises a sputtering process.
10. The method of claim 1 , wherein said forming said first adhesion/barrier layer comprises a sputtering process.
11. The method of claim 1 , wherein said forming said first adhesion/barrier layer comprises forming a titanium-containing layer over said first polymer layer.
12. The method of claim 1 , wherein said forming said first adhesion/barrier layer comprises sputtering a titanium layer with a thickness between 0.01 and 3 micrometers over said first polymer layer.
13. A method for forming a post-passivation metallization system for an integrated circuit chip, comprising:
providing a silicon substrate, multiple MOS devices in and on said silicon substrate, a first metallization structure over said silicon substrate, wherein said first metallization structure is formed by a process comprising using a 5X stepper or scanner, and wherein said first metallization structure comprises a damascene copper and a first adhesion/barrier layer under said damascene copper and at a sidewall of said damascene copper, and a passivation layer over said first metallization structure, wherein said passivation layer comprises a topmost oxynitride layer of said integrated circuit chip;
forming a first polymer layer on said passivation layer, wherein said forming said polymer layer comprises depositing a photosensitive polymer on said passivation layer; and
forming a second metallization structure over said first polymer layer, wherein said second metallization structure connects said multiple MOS devices through separate portions of said first metallization structure, and wherein said second metallization structure comprises a metal line having a sheet resistance smaller than 7 milliohms per square, wherein said forming said second metallization structure comprises forming a second adhesion/barrier layer over said first polymer layer, forming a seed layer on said second adhesion/barrier layer, performing a photolithography process to form a photoresist layer on said seed layer, an opening in said photoresist layer exposing said seed layer, wherein said performing said photolithography process comprises using a 1X stepper, electroplating a bulk metal layer on said seed layer exposed by said opening in said photoresist layer, wherein the material of said bulk metal layer is the same as that of said seed layer, removing said photoresist layer, removing said seed layer not under said bulk metal layer, and removing said adhesion/barrier layer not under said bulk metal layer.
14. The method of claim 13 , wherein said passivation layer comprises a nitride layer having a thickness greater than 0.3 micrometers.
15. The method of claim 13 , wherein said passivation layer comprises an oxide layer and a nitride layer over said oxide layer.
16. The method of claim 13 , further comprising forming a second polymer layer over said second metallization structure.
17. The method of claim 13 , wherein said forming said second adhesion/barrier layer comprises sputtering a titanium-tungsten-alloy layer over said first polymer layer.
18. The method of claim 13 , wherein said forming said second adhesion/barrier layer comprises sputtering a titanium layer over said first polymer layer.
19. The method of claim 13 , wherein said forming said seed layer comprises a sputtering process.
20. The method of claim 13 , wherein said electroplating said bulk metal layer comprises electroplating a gold layer with a thickness between 2 and 100 micrometers on said seed layer exposed by said opening in said photoresist layer.
21. The method of claim 13 , wherein said forming said adhesion/barrier layer comprises a sputtering process.
22. The method of claim 13 , wherein said electroplating said bulk metal layer comprises electroplating a copper layer with a thickness between 2 and 100 micrometers on said seed layer exposed by said opening in said photoresist layer.
23. The method of claim 13 , wherein said second metallization structure comprises a wirebonding pad.
24. The method of claim 13 , further comprising forming a solder bump connected to said second metallization structure.
25. The method of claim 13 , wherein an undercut with an edge of said second adhesion/barrier layer recessed from an edge of said bulk metal layer is between 0.03 and 2 micrometers.
26. The method of claim 20 , wherein said electroplating said bulk metal layer comprises electroplating a palladium layer on said seed layer exposed by said opening in said photoresist layer.
27. A circuit component comprising:
an integrated circuit chip comprising a silicon substrate, a MOS device in and on said silicon substrate, a first metallization structure over said silicon substrate, wherein said first metallization structure comprises a first metal layer and a second metal layer over said first metal layer, a dielectric layer between said first and second metal layers, a passivation layer over said first metallization structure and over said dielectric layer, a second metallization structure over said passivation layer, wherein said second metallization structure comprises a metal line having a sheet resistance smaller than 7 milliohms per square and having a width greater than 2 micrometers, and wherein said second metallization structure comprises a first adhesion/barrier layer over said passivation layer, a first gold layer on said first adhesion/barrier layer, and a second gold layer on said first gold layer, wherein said first adhesion/barrier layer has a thickness between 0.01 and 3 micrometers, said first gold layer has a thickness between 0.05 and 3 micrometers, and said second gold layer has a thickness between 2 and 100 micrometers, and a first polymer layer over said second metallization structure; and
a wirebond connecting a contact point of said second metallization structure to an external circuit, wherein said contact point is directly over said MOS device.
28. The circuit component of claim 27 , further comprising a second polymer layer between said second metallization structure and said passivation layer.
29. The circuit component of claim 27 , wherein said first adhesion/barrier layer comprises a titanium layer over said passivation layer.
30. The circuit component of claim 27 , wherein said first metallization structure comprises a damascene copper and a second adhesion/barrier layer under said damascene copper and at a sidewall of said damascene copper.
31. The circuit component of claim 27 , wherein said passivation layer comprises a nitride layer having a thickness greater than 0.3 micrometers.
32. The circuit component of claim 27 , wherein said passivation layer comprises an oxide layer and a nitride layer over said oxide layer.
33. The circuit component of claim 28 , wherein said second polymer layer comprises polyimide.
34. The circuit component of claim 28 , wherein said second polymer layer has a thickness between 2 and 100 micrometers.
35. The circuit component of claim 27 , wherein said first adhesion/barrier layer comprises a titanium-tungsten-alloy layer over said passivation layer.
36. The circuit component of claim 27 , wherein an undercut with an edge of said first adhesion/barrier layer recessed from an edge of said first gold layer is between 0.03 and 2 micrometers.
37. An integrated circuit chip comprising:
a silicon substrate;
multiple MOS devices in and on said silicon substrate;
a first metallization structure over said silicon substrate, wherein said first metallization structure comprises a first metal layer and a second metal layer over said first metal layer;
a passivation layer over said first metallization structure and over said dielectric layer, wherein said passivation layer comprises a topmost nitride layer of said integrated circuit chip;
a first polymer layer over said passivation layer;
a second metallization structure over said first polymer layer, wherein said second metallization structure connects multiple MOS devices through separate portions of said first metallization structure, wherein said second metallization structure comprises a third metal layer and fourth metal layer over said third metal layer, wherein one of said third and fourth metal layers comprises a first adhesion/barrier layer over said first polymer layer, a seed layer on said first adhesion/barrier layer, and an electroplated metal layer on said seed layer, and wherein said second metallization structure comprises a metal line having a sheet resistance smaller than 7 milliohms per square; and
a second polymer layer between said third and fourth metal layers.
38. The circuit component of claim 37 , wherein said first polymer layer has a thickness between 2 and 100 micrometers.
39. The circuit component of claim 37 , wherein said first polymer layer comprises polyimide.
40. The circuit component of claim 37 , wherein said first polymer layer comprises benzocyclobutene.
41. The circuit component of claim 37 , wherein said passivation layer comprises a nitride layer having a thickness greater than 0.3 micrometers.
42. The integrated circuit chip of claim 37 , wherein said passivation layer comprises an oxide layer and a nitride layer over said oxide layer.
43. The integrated circuit chip of claim 37 , wherein said electroplated metal layer comprises a gold layer with a thickness between 2 and 100 micrometers.
44. The integrated circuit chip of claim 37 , wherein said electroplated metal layer comprises a copper layer with a thickness between 2 and 100 micrometers.
45. The integrated circuit chip of claim 37 , wherein said electroplated metal layer comprises a palladium layer.
46. The integrated circuit chip of claim 37 , wherein said first adhesion/barrier layer comprises titanium.
47. The integrated circuit chip of claim 37 , wherein said first metallization structure comprises a damascene copper and a second adhesion/barrier layer under said damascene copper and at a sidewall of said damascene copper.
48. The integrated circuit chip of claim 37 , wherein said one of said third and fourth metal layers further comprises a nickel layer on said electroplated metal layer.