Passivation layer for packaged chip

A packaged integrated circuit (IC) chip, comprising:

• a metal bump formed over a metal pad;
• a testing pad, wherein the testing pad is electrically connected to devices in the packaged integrated circuit chip;
• a first passivation layer over a portion of the testing pad and a portion of the metal bump, wherein the first passivation layer defines a testing region of the testing pad and a bump-formation area of the metal bump;
• and
• a second passivation layer covering a surface of the testing pad and a portion of the first passivation layer surrounding the testing region of the testing pad, wherein a distance between edges of the second passivation layer covering the surface of the testing pad to edges of the testing pad is in a range from about 2 mm to about 15 mm.

A method of forming a packaged integrated circuit (IC) chip, comprising:

• forming a metal layer on a substrate, wherein the substrate has integrated circuits and an interconnect, and wherein the substrate is part of the packaged IC chip, and wherein the interconnect provides electrical connections between the integrated circuits and the metal layer;
• forming a first passivation layer over the metal layer, wherein the first passivation layer defines a testing pad region and a metal pad region, and wherein the metal pad region is for forming a metal bump;
• forming a second passivation layer over the first passivation layer, wherein the second passivation layer limitedly covers the testing pad region and a portion of the metal pad region, wherein the second passivation layer does not cover surfaces away from the testing pad region and the metal pad region;
• forming an under bump metallurgy (UBM) layer on the substrate, wherein the UBM layer comes in contact with at least a portion of the metal pad region, and wherein the UBM layer includes a diffusion barrier layer, and wherein the diffusion barrier layer is deposited by a sputtering process;
• and
• forming a metal bump over the UBM layer, wherein the metal bump is over the metal pad region.