Failure analysis and elimination method of pitting problem on microchip Al bond pads in wafer fabrication

Bond pad reliability is very important for either copper or aluminum back-end process. Pits on bond pad causes bonding sticking issue, brings reliability failure and the mechanism has been studied by [1][2], however no solution to solve this problem totally was provided in those two works. In this article, we designed a series of experiments including bond pad deposition, pad etch, strip and wet tank to study pits mechanism and methods of removing them on bond pad. The results, analysis and the limitation of implementation for different approach are discussed for every experiment; and a novel solution by DI wafer sequence which can solve pits problem was reported for the first time.