Potential Characterization of Interconnect Corrosion by Kelvin Probe and Electrostatic Force Microscopies

The fine-scale potential observation was performed by Kelvin probe force microscopy (KFM) and electrostatic force microscopy (EFM) using tungsten interconnects in which the minimum width was 43 nm. It was confirmed that the line connected to pads and/or a transistor has a peculiar KFM potential by comparing it with the surrounding pattern. Only the plugs attached to this line were corroded, while the other plugs remained intact. By comparing the results of KFM and EFM observations, the peculiar potential of the line can be attributed to the electron charge up in the bulk of the sample. Charged electrons induced corrosion not only in the line itself but also in the connected structure. It was also revealed that the particular potential can be suppressed by a wet treatment.