Cobalt and nickel for improved aluminum-indium tin oxide contact metallurgy in polysilicon TFT display applications

Among the issues associated with the fabrication of polysilicon thin film transistor (TFT) active matrix displays is the contact resistance between indium tin oxide (ITO) pixel electrodes and the aluminum data lines. We have investigated the use of Co and Ni for use as barrier layers between the Al and ITO in order to provide good ohmic contacts. For comparison, a titanium barrier layer has also been used and measured. A thin, 10 nm Co layer sufficed to provide good ohmic contacts in an ITO-Co-PII stack, while a thicker layer was required in the case of Ni in order to form a similar good ohmic contact. The contacts have been characterized using resistance measurements in conjunction with X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) in order to correlate the electrical results with the physical metallurgy of the contacts.