Application of Broadband RF Metrology to Integrated Circuit Interconnect Reliability Analyses: Monitoring Copper Interconnect Corrosion in 3D-ICs

In this paper we describe the application of highfrequency electromagnetic wave (in microwave frequency / radio frequency (RF in the range, i.e., 3 kHz – 300 GHz) based techniques to probe material and structural changes that occur in integrated circuits. These techniques fall under the general area of “Broadband Dielectric Spectroscopy”. In this paper, we describe corrosion of the redistribution layer (RDL), required for the implementing 3-D integrated circuits (3D-ICs), during hightemperature storage. As an illustration of our techniques, we use the RF signal loss between ports 1 and 2 on a typical vector network analyzer (i.e., RF insertion loss, S21), to monitor the oxidation of the RDL copper interconnects. We compare the RF signal loss results to the direct current-resistance that was measured simultaneously with the S21. Using electrodynamic simulations, partition the RF signal loss in corroded copper interconnects, and discuss the significance of the roughness at the air-copper oxide interface.