Detailed and analytical approach in the discovery of cracks on thin passivation layer underneath the polyimide structure of a die

Defects or deformations on the polyimide layer of a particular die can be caused by many factors. Additionally, it is rather inaccurate to determine the extent of the damage to the whole die by just observing or analysing the topmost polyimide layer. Classical physical failure analysis approach would usually employ tools such as optical microscopy, SEM-EDX and FIB cross section. In rare cases, STEM-EDX, Auger, XPS and AFM would also be employed. Most of these tools (with the exception of FIB) deals with top surface analyses and would prove to be futile in investigating layers underneath the thick polyimide structure. This manuscript describes in detail the analytical approach used in determining the extent of the damage from a deformed polyimide layer. Physical deformations such as tool imprints, scratches or even dents on the polyimide layer of a die could impact the layers underneath in various ways. Thus, it is of great importance to perform a thorough investigation to determine the extent of the damage, and whether the damage could possibly impact the reliability of the die and its application