Generation mechanism and reduction methods of post-passivation-etch silklike polymers

Silk-like polymers (SLP) are inspected after photoresist stripping at the post-passivation-etch stage. They mainly distribute on the scribe lines between the die chips, but partially generate from the bonding pads and stay on the passivation films. Their width is around 100 - 200 nm, but the length could be extended to several hundred micrometers. The SLP will act as a mask with respect to the following low-power CF4 plasma treatment and leave the SLP-shaped replicas on the passivation films. They even remain on the bonding pads to affect the bonding performance. An O2 plasma cleaning chemicals was found with the ability to successfully remove the SLP. The formation mechanism of the SLP will be investigated and the prevention methods also discussed in the study.