Wafer level package and method
A copper pillar bump semiconductor packaging method patterns an organic insulation layer formed under the copper pillar bumps to areas surrounding and in the vicinity of the copper pillar bumps only. The organic insulation layer, typically a thin film polymer layer, acts as a barrier layer for the copper pillar bumps to protect the semiconductor wafer during the copper pillar flip chip bonding process. The copper pillar bump semiconductor packaging method limits the areas where the organic insulation layer is applied to reduce the stress introduced to the semiconductor wafer by the organic insulation layer. In another embodiment, a copper pillar bump semiconductor packaging method patterns an organic insulation layer formed under the copper pillar bumps to areas surrounding the copper pillar bumps and along the path of a redistribution layer without using a large and continuous organic insulation layer.
1. A method of forming a copper pillar bump semiconductor package, comprising:
providing a finished semiconductor wafer comprising a semiconductor substrate having a passivation layer formed thereon covering a top surface of the semiconductor substrate and exposing a bond pad;
forming a first organic insulation layer on the semiconductor wafer;
patterning the first organic insulation layer to cover a first area at an interface of the bond pad and the passivation layer, to cover a second area of a bump pad to be formed, and to form islands of the first organic insulation layer along a path of a redistribution layer to be formed from the bond pad to the bump pad, the first organic insulation layer being removed from the bond pad and from the remaining area of the semiconductor wafer outside the first area, the second area and the islands of first organic insulation layer;
forming a first seed metal layer on the first organic insulation layer and the semiconductor wafer;
forming the redistribution layer on the semiconductor wafer over the bond pad and the first organic insulation layer, the redistribution layer being formed to include the bump pad being spaced apart from the bond pad and a conductive trace connecting the bond pad to the bump pad, the bump pad being formed over the second area of the first organic insulation layer and the conductive trace being formed over the islands of the first organic insulation layer;
removing the first seed metal layer not formed under the redistribution layer;
forming a second seed metal layer on the redistribution layer and the semiconductor wafer;
forming a copper pillar bump on the second seed metal layer and above the bump pad;
removing the second seed metal layer not formed under the copper pillar bump; and
reflowing the copper pillar bump.
2. The method of claim 1 , wherein forming the first organic insulation layer on the semiconductor wafer comprises:
forming the first organic insulation layer on the semiconductor wafer, the first organic insulation layer comprising a thin film polymer material.
3. The method of claim 2 , wherein the first organic insulation layer comprises polyimide (PI) or polybenzoxazole (PBO).
4. The method of claim 1 , wherein patterning the first organic insulation layer to cover the first area at the interface of the bond pad and the passivation layer comprises:
patterning the first organic insulation layer to cover the first area at the interface of the bond pad and the passivation layer, the first organic insulation layer overlapping the interface with an overlap width, the first organic insulation layer being removed from the bond pad and from the remaining area of the semiconductor wafer outside the first area, the second area and the islands of first organic insulation layer.
5. The method of claim 4 , wherein patterning the first organic insulation layer to cover the first area at the interface of the bond pad and the passivation layer comprises:
patterning the first organic insulation layer in a circular shape to cover the first area at the interface of the bond pad and the passivation layer, the first organic insulation layer overlapping the interface with an overlap width, the first organic insulation layer being removed from the bond pad and from the remaining area of the semiconductor wafer outside the first area, the second area and the islands of first organic insulation layer.
6. The method of claim 4 , wherein patterning the first organic insulation layer to cover the area at the interface of the bond pad and the passivation layer comprises:
patterning the first organic insulation layer in a rectangular shape to cover the first area at the interface of the bond pad and the passivation layer, the first organic insulation layer overlapping the interface with an overlap width, the first organic insulation layer being removed from the bond pad and from the remaining area of the semiconductor wafer outside the first area, the second area and the islands of first organic insulation layer.
7. The method of claim 1 , wherein forming the first organic insulation layer on the semiconductor wafer and patterning the first organic insulation layer comprises:
forming the first organic insulation layer to cover the entire surface of the semiconductor wafer; and
patterning the first organic insulation layer to remove the organic insulation layer from the surface of the semiconductor wafer except at the first area at the interface of the bond pad and the passivation layer, the second area of the bump pad to be formed and the islands of the first organic insulation layer.
8. The method of claim 1 , wherein forming the redistribution layer on the semiconductor wafer comprises:
patterning the semiconductor wafer to expose areas where the redistribution layer is to be formed; and
forming, by plating, a copper layer in the exposed areas as the redistribution layer on the semiconductor wafer.
9. The method of claim 1 , further comprising:
after removing the first seed metal layer and before forming the second seed metal layer, forming a second organic insulation layer on the semiconductor wafer over the redistribution layer; and
patterning the second organic insulation layer to cover a third area over and around the bond pad, to cover a fourth area around the bump pad, and to form islands of the second organic insulation layer along the path of the redistribution layer from the bond pad to the bump pad, the second organic insulation layer being removed from the bump pad and from the remaining area of the semiconductor wafer outside the third area and the fourth area,
wherein the second seed metal layer is formed on the semiconductor wafer over the bump pad formed by the redistribution layer and the second organic insulation layer.
10. The method of claim 9 , wherein the islands of the second organic insulation layer are formed offset from the islands of the first organic insulating layer.
11. The method of claim 9 , wherein forming the second organic insulation layer on the semiconductor wafer over the redistribution layer comprises:
forming the second organic insulation layer on the semiconductor wafer over the redistribution layer, the second organic insulation layer comprising a thin film polymer material.
12. The method of claim 11 , wherein the second organic insulation layer comprises polyimide (PI) or polybenzoxazole (PBO).
13. The method of claim 9 , wherein forming the second organic insulation layer on the semiconductor wafer and patterning the second organic insulation layer comprises:
forming the second organic insulation layer to cover the entire surface of the semiconductor wafer over the redistribution layer; and
patterning the second organic insulation layer to remove the second organic insulation layer from the surface of the semiconductor wafer except at the third area over and around the bond pad, the fourth area around the bump pad, and the islands of the second organic insulation layer.