Mechanisms for forming copper pillar bumps
The mechanism of forming a metal bump structure described above resolves the delamination issues between a conductive layer on a substrate and a metal bump connected to the conductive layer. The conductive layer can be a metal pad, a post passivation interconnect (PPI) layer, or a top metal layer. By performing an in-situ deposition of a protective conductive layer over the conductive layer (or base conductive layer), the under bump metallurgy (UBM) layer of the metal bump adheres better to the conductive layer and reduces the occurrence of interfacial delamination. In some embodiments, a copper diffusion barrier sub-layer in the UBM layer can be removed. In some other embodiments, the UBM layer is not needed if the metal bump is deposited by a non-plating process and the metal bump is not made of copper.
1. A bump structure on a substrate, comprising:
a composite conductive layer embedded in the substrate, wherein the composite conductive layer includes a protective conductive layer over a base conductive layer, and wherein the protective conductive layer is made of a material less likely to be oxidized in presence of air or water than a material for the base conductive layer;
a dielectric layer over the composite conductive layer, wherein the protective conductive layer positioned to separate the dielectric layer from the base conductive layer;
a polymer layer over the dielectric layer; and
a metal bump, wherein the metal bump fills a second opening of a photoresist layer, wherein the second opening is formed above a first opening created in the polymer layer to make contact with the protective conductive layer of the composite conductive layer.
2. The bump structure of claim 1 , wherein an under bump metallurgy (UBM) layer lines a surface of the first opening and an interface between the polymer layer and the photoresist layer and wherein the UBM layer is part of the metal bump.
3. The bump structure of claim 2 , wherein the metal bump includes a copper layer, a copper diffusion barrier, and a solder ball, and wherein the UBM layer includes a copper seed layer.
4. The bump structure of claim 2 , wherein the UBM layer includes a diffusion barrier layer and a copper seed layer.
5. The bump structure of claim 2 , wherein the metal bump includes a copper pillar formed by plating and the UBM layer includes a copper seed layer.
6. The bump structure of claim 5 wherein the metal bump further includes a cap layer over the copper pillar, and a solder layer over the cap layer.
7. The bump structure of claim 6 , wherein the copper pillar is made of copper or copper alloy, and wherein the cap layer is made of a material selected from the group consisting of nickel, tin, tin-lead, gold, silver, palladium, indium, nickel-palladium-gold, nickel-gold, and other alloys of the above-mentioned materials, and wherein the solder layer is lead-free or contains lead.
8. The bump structure of claim 1 , wherein the metal bump includes a solder ball.
9. The bump structure of claim 1 , wherein the protective conductive layer is made of a material selected from the group consisting of Ta, TaN, Ti, TiN, and a combination thereof.
10. The bump structure of claim 1 , wherein the protective conductive layer has a thickness in a range between about 1000 Å to about 2,000 Å.
11. The bump structure of claim 1 , wherein base conductive layer is made of a material selected from the group consisting of copper, aluminum, and copper alloy.
12. The bump structure of claim 1 , wherein the composite conductive layer is a metal pad a post passivation interconnect (PPI), or a top metal layer.
13. The bump structure of claim 1 , wherein the polymer layer is made of a material selected from the group consisting of epoxy, polyimide, benzocyclobutene (BCB), and polybenzoxazole (PBO).
14. The bump structure of claim 13 , wherein the polyimide is poly(4,4′-oxydiphthalic anhydride-1,3-aminophenoxybenzene-8-azaadenine) (ODPA-APB-8-azaadenine).
15. A bump structure on a substrate, comprising:
a composite conductive layer embedded in the substrate, wherein the composite conductive layer includes a protective conductive layer over a base conductive layer, and wherein the protective conductive layer is made of a material less likely to be oxidized in presence of air or water than a material for the base conductive layer;
a dielectric layer over the composite conductive layer;
a polymer layer over the dielectric layer;
a copper bump, wherein the copper bump fills a second opening of a photoresist layer, wherein the second opening is formed above a first opening created in the polymer layer to make contact with the protective conductive layer of the composite conductive layer, and wherein the copper bump includes an under bump metallurgy (UBM) layer lining a surface of the first opening and an interface between the polymer layer and the photoresist layer, and the copper bump extends into the first opening.
16. The bump structure of claim 15 , wherein the UBM layer is a copper seed layer.
17. The bump structure of claim 15 , wherein the protective conductive layer is made of a material selected from the group consisting of Ta, TaN, Ti, TiN, and a combination thereof, and wherein the protective conductive layer has a thickness between about 1000 Å to about 2,000 Å.
18. The bump structure of claim 15 , wherein the base conductive metal layer is made of a material selected from the group consisting of copper, aluminum, and copper alloy.
19. An integrated circuit device, comprising:
a substrate;
a composite conductive layer embedded in the substrate, the composite conductive layer comprising:
a base conductive layer; and
a protective conductive layer over the base conductive layer, the protective conductive layer having a characteristic of oxidation rate slower than that of the base conductive layer in presence of air or water;
a dielectric layer over the composite conductive layer and having a first opening defined therein to expose a first portion of an upper surface of the protective conductive layer;
a polymer over the dielectric layer and having a second opening defined therein to expose a second portion of the upper surface of the protective conductive layer, the second portion being smaller than the first portion; and
a bump structure at least partially in the second opening, the bump structure being positioned over the polymer layer and the exposed second portion of the upper surface of the protective conductive layer.
20. The integrated circuit device of claim 19 , wherein the bump structure comprises a solder bump directly on the exposed portion of the upper surface of the protective conductive layer.
21. The integrated circuit device of claim 19 , wherein the bump structure comprises an under bump metallurgy (UBM) layer over the exposed second portion of the upper surface of the protective conductive layer.
22. The integrated circuit device of claim 19 , wherein the bump structure further comprises a copper pillar over the UBM layer.
23. The integrated circuit device of claim 19 , wherein the protective conductive layer is made of a material selected from the group consisting of Ta, TaN, Ti, TiN, and a combination thereof.
24. The integrated circuit device of claim 19 , wherein the protective conductive layer has a thickness ranging from 1000 Å to about 2,000 Å.
25. The integrated circuit device of claim 19 , wherein the bump structure comprises:
a metal layer having sidewalls positioned above the opening;
a cap layer over the metal layer; and
a solder layer over the cap layer.