Granted Patent B2

US 9,324,667 · App. 13/350,098 · Granted Apr 26, 2016

Abstract

Claims (25)

1. A method of forming a connecting pillar to a bond pad of an integrated circuit:

forming a seed layer over the bond pad;

depositing photoresist over the seed layer;

forming a first opening in the photoresist over the bond pad, wherein a largest cross-sectional diameter of the first opening is within a perimeter of the bond pad and the first opening has substantially the same diameter from a bottom of the first opening to a top of the first opening;

forming a lower portion of a connecting pillar in the first opening by plating, wherein the lower portion is in contact with the seed layer;

forming a second photoresist layer having a second opening over the bond pad;

forming a mid portion of the connecting pillar in the second opening by plating, wherein the mid portion is in contact with the lower portion, the mid portion has a cross-sectional diameter that is less than a smallest cross-sectional diameter of the lower portion;

forming a cap portion by allowing plating to overflow sides of the second opening, the cross-sectional diameter of the mid portion is less than a cross-sectional diameter of the cap portion.

2. The method of claim 1 , further comprising etching back a central portion of the connecting pillar to reduce the diameter of the mid portion of the connecting pillar.

3. The method of claim 2 , wherein forming the connecting pillar comprises changing materials from a first material to a second material during plating, wherein the second material is in the mid portion and reduced in diameter during the step of etching back.

4. The method of claim 1 , wherein the step of forming the connecting pillar is further characterized by the connecting pillar extending above the top of the first opening.

5. The method of claim 4 , further comprising:

removing the photoresist; and

removing a portion of the seed layer using the connecting pillar as a mask.

6. The method of claim 1 , wherein

the second opening has a second diameter less than the first diameter.

7. The method of claim 6 , wherein the step of forming the connecting pillar comprises plating in the first opening prior to the step of forming the second photoresist layer.

8. The method of claim 7 , wherein the step of forming the connecting pillar comprises plating in the second opening.

9. The method of claim 1 , wherein the step of forming the connecting pillar comprises changing a material being plated so that material plated above the second photoresist layer is a different material than material plated in the first opening.

10. The method of claim 1 , further comprising plating a top of the connecting pillar with solder.

11. The method of claim 1 , wherein the step of depositing photoresist comprises:

depositing a layer of photoresist;

exposing a portion of the photoresist in a pattern of an area over the bond pad; and

applying a hardener to harden a top portion of the photoresist;

wherein the step of forming the opening comprises opening the area over the bond pad and laterally extending the area over the bond pad in a region below the top portion of the photoresist.

Assignments (22)