Silver metallization for advanced interconnects

Silver metal has the highest room-temperature electrical conductivity of any substance; however, it has found limited acceptance in the electronic industry (e.g., silver filled epoxy) due to the high rate of metal corrosion and migration causing dendrites and electrical failures. With decreasing transistor feature sizes, device-operating voltages have scaled down considerably. In this paper, the reliability of silver and potential benefits of silver metallization are discussed in terms of future trends in microelectronic interconnections. Experimental data supports existing reliability models indicating that electrochemical migration failure modes may not be operative at low voltages. Silver metal corrosion and migration are studied under accelerated test conditions to obtain a qualitative understanding of the failure mechanism.