ToF-SIMS study of adhesive residuals on device contact pads after wafer taping and backgrinding

Wafer thinning prior to bonding and packaging of integrated circuits (IC) is accomplished by back-surface grinding using abrasive tools. At this stage of device fabrication, most of the IC surface but the contact pads is covered by the passivation layer. Being unprotected, the pads could thus be easily contaminated by particles and chemicals. An adhesive tape is commonly used to shield the IC front surface. However, adhesive residuals that can detrimentally affect the pad/wire bonding and seriously alter the sticking of the package plastic with the device surface can be likely present as a consequence. TOF-SIMS was used to investigate the adhesive residuals on the contact pads after using different tapes, allowing to recognise the compounds transferred from time to time on the IC surface. Semi-quantitative evaluations of the adhesive residual amount after exploiting several cleaning recipes were also obtained, allowing the tailoring of the cleaning process parameters after contamination identification