Evolution of Enhanced Performance of a-IGZO TFTs With Cu/Al-Based Contacts

The amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) with Cu/Al stacked contacts to restrain the transferring of Cu to a-IGZO were prepared by thermal evaporation and magnetron sputtering. Compared to Cu contacts, the devices of stacked contacts offered improved performance and stability. When Al thickness was increased to 5 nm, the devices of stacked contacts exhibited field effect mobility ( $\mu _{\text {FE}}\text {)}$ of 25 cm2/V $\cdot $ s and the subthreshold swing (SS) of 0.49 V/dec. Particularly, the threshold voltage shift ( $\Delta $ V ${}_{\text {th}}\text {)}$ of the devices with stacked contacts was -0.29 V under the negative bias stress. Furthermore, the devices with stacked contacts of 5 nm Al presented outstanding contact characteristics by transmission line mode analysis. The results suggested that Cu/Al electrodes were expected to become useful electrodes for optimizing metal oxide TFTs.