Self aligned bump passivation

摘要

A method of fabricating multiple conductor layers utilizing the same seed layer is described. In an embodiment a stud bump structure is described in which the seed layer is encapsulated by the passivation layer. By forming the stud bump prior to the passivation layer, the height of the stud bump extending from the top surface of the passivation layer can be controlled.

主权项

1. A method comprising:
blanket depositing a seed layer on a surface of a substrate; forming a first photoresist layer over the substrate and patterning a first opening in the first photoresist layer exposing a portion of the seed layer; electroplating a redistribution layer on the portion of the seed layer exposed in the first opening; removing the first photoresist layer using a sodium carbonate or potassium hydroxide based solution; forming a second photoresist layer over the substrate and patterning a second opening in the second photoresist layer exposing a portion of the redistribution layer; forming a self-aligned stud bump by sequentially electroplating a bulk metal layer on the portion of the redistribution layer exposed in the second opening and a cap layer on the bulk metal layer to form a completed stud bump in the opening without forming an additional photoresist layer; removing the second photoresist layer from the substrate to expose a portion of the seed layer using a sodium carbonate or potassium hydroxide based solution; removing the exposed portion of the seed layer; screen printing a passivation layer over the substrate, seed layer, redistribution layer and the completed stud bump; and etching back the passivation layer to expose a portion of the cap layer, so that a top surface of the stud bump is above a top surface of the passivation layer, and the seed layer, the redistribution layer, the bulk metal layer and at least a portion of sidewalls of the cap layer are encapsulated by the passivation layer.