Method for forming bump of semiconductor package

1. A method for forming bumps of a semiconductor package to suppress a final height difference between main bumps and support bumps that is caused by a height difference between areas of an underlying layer when viewed on a cross-section, the method comprising:

forming first seed layer patterns and second seed layer patterns which are disposed in the areas and are electrically separated from each other, over the underlying layer having the height difference; and

forming the main bumps and the support bumps by an electroplating process using the first seed layer patterns and the second seed layer patterns as electrodes,

wherein the electroplating process is performed under a condition that a voltage applied to the first seed layer patterns and a voltage applied to the second seed layer patterns are different from each other so that upper ends of the main bumps and upper ends of the support bumps are located at the same level.

2. The method according to claim 1 , wherein the underlying layer includes a semiconductor chip which has electrode pads disposed at a center portion of a top surface thereof and an insulation layer formed over the top surface in such a way as to expose the electrode pads.

3. The method according to claim 1 , wherein the underlying layer includes a semiconductor chip which has electrode pads disposed over a top surface thereof, a first insulation layer formed over the top surface in such a way as to expose the electrode pads, redistribution lines formed over the electrode pads and the first insulation layer and a second insulation layer formed over the first insulation layer in such a way as to expose ends of the redistribution lines.

4. The method according to claim 1 , wherein the underlying layer includes an interposer which has electrode pads disposed at a center portion of a top surface thereof and an insulation layer formed over the top surface in such a way as to expose the electrode pads.

5. The method according to claim 1 , wherein the forming of the first seed layer patterns and the second seed layer patterns comprises:

forming a seed layer over the underlying layer having the height difference;

forming, over the seed layer, a photoresist pattern which exposes main bump forming areas, portions of the seed layer therebetween, support bump forming areas and portions of the seed layer therebetween;

etching the seed layer by using the photoresist pattern as an etch mask; and

removing the photoresist pattern.

6. The method according to claim 1 , wherein the forming of the first seed layer patterns and the second seed layer patterns comprises:

disposing, over the underlying layer having the height difference, a shadow metal mask having a structure which exposes main bump forming areas, portions therebetween, support bump forming areas and portions therebetween;

depositing selectively a seed layer over the exposed areas of the underlying layer by using the shadow metal mask as a deposition mask; and

removing the shadow metal mask.

7. The method according to claim 1 , wherein the first seed layer patterns and the second seed layer patterns are formed in the shapes of lines which extend in a vertical direction and are alternately disposed in a horizontal direction or extend in the horizontal direction and are alternately disposed in the vertical direction and in which ends of the lines are connected with one another.

8. The method according to claim 1 , wherein the first seed layer patterns are formed in the shapes of lines each of which extends in a horizontal direction and includes, at intermediate portions thereof, branch portions extending in a vertical direction, and the second seed layer patterns are formed in the shapes of plates which surround the first seed layer patterns.

9. The method according to claim 1 , wherein the forming of the main bumps and the support bumps is performed under a condition that a magnitude of the voltage applied to the first seed layer patterns and a magnitude of the voltage applied to the second seed layer patterns are different from each other.

10. The method according to claim 9 , wherein the forming of the main bumps and the support bumps is performed in such a way as to sequentially form copper pillars and a solder through electroplating.

11. The method according to claim 10 , wherein the electroplating is performed in such a way as to control a plating thickness of at least one of the copper pillars and the solder.

12. The method according to claim 2 , wherein the semiconductor chip includes any one among a memory chip, a logic chip, a DDI (display driver IC) and a CMOS image sensor chip.

13. The method according to claim 1 , wherein the forming of the main bumps and the support bumps is performed under a condition that a voltage application time length to the first seed layer pattern and a voltage application time length to the second seed layer pattern are different from each other.