K. Li, P. Liu, J. Teong, Chartered Semiconductor Manufacturing Ltd, Singapore, Singapore

Summary: This paper presents a step-by-step logic thinking process for a field return high via reistance issue. It involves electrical fault isolation, process commonality check, physical characterization, design of experiment and logic thinking. It is found that the non-optimized via cleaning recipe (due to the introduction of CO2 into DI water) causes damage to the Al at the via bottom, and the single via on big metal structure has rigorous stress condition. Therefore this structure is more vulnerable to Al intrusion and high via resistance. A redesign of the structure, such as adding one more via onto the big metal piece, will alleviate the rigorous stress condition and reduce the failure rate.