Fine pitch wafer bumping process

A fine pitch wafer bumping process comprising:

• providing a wafer that has a plurality of contact pads and a passivation layer that is formed on the surface of the wafer while exposing the plurality of contact pads, wherein the surface of each of the plurality of contact pads has respectively an under bump metal (UBM);
• forming a first mask film over the surface of the wafer, wherein the first mask film has a plurality of first openings that expose respectively the plurality of under bump metals (UBM);
• filling a first solder material respectively in the plurality of first openings;
• reflowing the first solder material to form respectively a plurality of first solder posts;
• forming a second mask film on the first mask film, wherein the second mask film has a plurality of second openings that respectively expose the plurality of first openings;
• filling a second solder material respectively in the plurality of second openings;
• reflowing the second solder material and the first solder posts to form a plurality of second solder posts;
• removing the first mask film and the second mask film;
• and
• reflowing the first and second solder posts to form a plurality of bumps.