Irregular effect of chloride impurities on migration failure reliability:: contradictions or understandable?

Metals can exhibit dendritic short-circuits caused by electrochemical migration in conductor-insulator structures, which may result in failures and reliability problems in microcircuits. The phenomenon of electrochemical migration has been well known for several decades; the process is a transport of metal ions between two metallization stripes under bias through a continuous aqueous electrolyte. Due to the electrodeposition at the cathode, dendrites and dendrite-like deposits are formed. Ultimately, such a deposit can lead to a short circuit in the device and can cause catastrophic failure. Surface contaminants, especially ionic types, may have significant influences on the overall process. Cl- contaminant has been investigated extensively; however, many contradictory statements were published. The role of these contaminants is rather complicated in influencing the formation of migrated resistive shorts: the various effects act against each other. Theoretical explanations are discussed and strengthened by experimental results in this paper. (C) 1999 Elsevier Science Ltd. All rights reserved.