Improvement for bond pads discolor (sic) of CMOS image sensor products

The CMOS image sensor is covered with a color filter. Bond pads discoloration was found after the color filter process. SEM analysis showed metal loss of the bond pads, and residues in the discolored area. EDS results showed the residues contained mostly C and O elements, indicating photoresist residues. These defects caused package reliability problems based on a bondability test. Color filter processes are composed of multicolor photoresist layers. During several development processes most of the metal was lost, inducing metal film roughness and then causing photoresist residues on the bond pads. In order to improve bond pads discoloration, two methods for the color filter processes were evaluated: (1) decreased rework (development process) frequency, and (2) added bond pads protection, which showed some success.