Semiconductor device and method of forming bump structure with insulating buffer layer to reduce stress on semiconductor wafer
A semiconductor wafer has a plurality of semiconductor die with contact pads for electrical interconnect. An insulating layer is formed over the semiconductor wafer. A bump structure is formed over the contact pads. The bump structure has a buffer layer formed over the insulating layer and contact pad. A portion of the buffer layer is removed to expose the contact pad and an outer portion of the insulating layer. A UBM layer is formed over the buffer layer and contact pad. The UBM layer follows a contour of the buffer layer and contact pad. A ring-shaped conductive pillar is formed over the UBM layer using a patterned photoresist layer filled with electrically conductive material. A conductive barrier layer is formed over the ring-shaped conductive pillar. A bump is formed over the conductive barrier layer. The buffer layer reduces thermal and mechanical stress on the bump and contact pad.
1. A method of making a semiconductor device, comprising:
providing a semiconductor wafer having a contact pad;
forming an insulating layer over the semiconductor wafer;
forming a buffer layer over the insulating layer and contact pad;
removing a portion of the buffer layer to expose the contact pad;
forming a first conductive layer over the buffer layer and contact pad, the first conductive layer being electrically connected to the contact pad;
forming a ring-shaped conductive pillar over the first conductive layer;
forming a second conductive layer over the ring-shaped conductive pillar; and
forming a bump over the second conductive layer.
2. The method of claim 1 , wherein the buffer layer reduces stress on the bump and contact pad.
3. The method of claim 1 , wherein forming the ring-shaped conductive pillar includes:
forming a photoresist layer over the first conductive layer;
removing a portion of the photoresist layer to create a ring-shaped opening and expose the first conductive layer;
depositing an electrically conductive material in the ring-shaped opening over the first conductive layer; and
removing the photoresist layer.
4. The method of claim 1 , wherein forming the bump includes:
forming a photoresist layer over the first conductive layer;
removing a portion of the photoresist layer to expose the first conductive layer and ring-shaped conductive pillar;
depositing bump material over the first conductive layer and ring-shaped conductive pillar; and
reflowing the bump material to form the bump.
5. The method of claim 1 , wherein the first conductive layer follows a contour of the buffer layer and contact pad.
6. The method of claim 1 , wherein the first conductive layer is an under bump metallization layer and the second conductive layer is a barrier layer.
7. A method of making a semiconductor device, comprising:
providing a semiconductor die having a contact pad;
forming an insulating layer over the semiconductor die;
forming a buffer layer over the insulating layer and contact pad;
forming a first conductive layer over the buffer layer and contact pad;
forming a conductive pillar over the first conductive layer;
forming a second conductive layer over the conductive pillar; and
forming an electrical interconnect over the second conductive layer.
8. The method of claim 7 , wherein the buffer layer reduces stress on the electrical interconnect and contact pad.
9. The method of claim 7 , wherein the conductive pillar has a ring shape.
10. The method of claim 7 , wherein the electrical interconnect includes a bump.
11. The method of claim 7 , wherein forming the conductive pillar includes:
forming a photoresist layer over the first conductive layer;
removing a portion of the photoresist layer to expose the first conductive layer;
depositing an electrically conductive material over the first conductive layer; and
removing the photoresist layer.
12. The method of claim 7 , wherein forming the bump includes:
forming a photoresist layer over the first conductive layer;
removing a portion of the photoresist layer to expose the first conductive layer and conductive pillar;
depositing bump material over the first conductive layer and conductive pillar; and
reflowing the bump material to form the bump.
13. The method of claim 7 , wherein the first conductive layer follows a contour of the buffer layer and contact pad.
14. A method of making a semiconductor device, comprising:
providing a semiconductor die having a contact pad;
forming a buffer layer over the semiconductor die and contact pad;
forming a first conductive layer over the buffer layer and contact pad;
forming a conductive pillar over the first conductive layer; and
forming an electrical interconnect over the conductive pillar and first conductive layer.
15. The method of claim 14 , further including forming an insulating layer over the semiconductor die prior to forming the buffer layer.
16. The method of claim 14 , further including forming a second conductive layer over the conductive pillar.
17. The method of claim 14 , wherein the buffer layer reduces stress on the electrical interconnect and contact pad.
18. The method of claim 14 , wherein the conductive pillar has a ring shape.
19. The method of claim 14 , wherein forming the conductive pillar includes:
forming a photoresist layer over the first conductive layer;
removing a portion of the photoresist layer to expose the first conductive layer;
depositing an electrically conductive material over the first conductive layer; and
removing the photoresist layer.
20. The method of claim 14 , wherein forming the bump includes:
forming a photoresist layer over the first conductive layer;
removing a portion of the photoresist layer to expose the first conductive layer and conductive pillar;
depositing bump material over the first conductive layer and conductive pillar; and
reflowing the bump material to form the bump.
21. A semiconductor device, comprising:
a semiconductor die having a contact pad;
an insulating layer disposed over the semiconductor die;
a buffer layer disposed over the insulating layer and contact pad;
a first conductive layer disposed over the buffer layer and contact pad;
a conductive pillar disposed over the first conductive layer; and
an electrical interconnect disposed over the second conductive layer.
22. The semiconductor device of claim 21 , wherein the buffer layer reduces stress on the electrical interconnect and contact pad.
23. The semiconductor device of claim 21 , wherein the conductive pillar has a ring shape.
24. The semiconductor device of claim 21 , further including a second conductive layer disposed over the conductive pillar.
25. The semiconductor device of claim 21 , wherein the first conductive layer follows a contour of the buffer layer and contact pad.