Conductive structure and method for forming the same

A method for forming a conductive structure of a semiconductor chip, the semiconductor chip comprising a semiconductor substrate, a plurality of first pads, a plurality of second pads, a passivation layer and an under bump metal layer, wherein each of the first pads and each of the second pads are alternately arranged on a pad area of the semiconductor substrate, the pad area defines a first area, a second area and a third area, the first area is located between the second area and the third area, each of the first pads and each of the second pads are interlaced with each other on the first area, and the first area is extending toward the second area and the third area respectively, and wherein the passivation layer formed on the semiconductor substrate has a plurality of first openings to partially expose the first pads and the second pads, and the under bump metal layer is formed on the passivation layer and covers each of the first pads and each of the second pads through each of the first openings formed in the passivation layer to electrically connect with each of the first pads and each of the second pads, the method comprising the steps of:

• (a) forming a patterned insulation layer on the under bump metal layer, the patterned insulation layer being formed with a plurality of second openings to partially expose the under bump metal layer, wherein each of the second openings has a first opening-width in the first area and a second opening-width in one of the second area and the third area, and the first opening-width is smaller than the second opening-width;
• (b) forming a conductive bump within each of the second openings to partially cover the under bump metal layer, the conductive bumps being disposed on each of the first pads and each of the second pads, wherein a shape of each of the conductive bumps corresponds to a shape of each of the second openings in such a way that a first bump-width of the conductive bump corresponds to the first opening-width and a second bump-width of the conductive bump corresponds to the second opening-width, and the first bump-width is smaller than the second bump-width;
• and
• (c) removing the patterned insulation layer to expose each of the conductive bumps.