Thermally stable, amorphous HfO2 thin films deposited using atomic layer deposition have been studied as a diffusion barrier between Cu and the Si substrate. 4 nm thick as-deposited HfO2 films deposited on Si are characterized with X-ray photoelectron spectroscopy. Cu/HfO2/<Si> samples are annealed at different temperatures, starting from 500 °C, in the presence of N2 atmosphere for 5 min and characterized using sheet resistance, X-ray diffraction and scanning electron microscopy. Ultrathin HfO2 films are found to be effective diffusion barrier between Cu and Si with a high failure temperature of about 750 °C.

A capillary bridge printing technique has been used to deposit copper interconnects using homogeneous solutions of a Cu(II) precursor in a series of low boiling primary alcohols. The rheological properties of the solutions have been measured first to determine their printability. The as-printed lines with subsequent annealing at relatively low temperatures (∼200 °C), in order to evaporate the volatile solvents and facilitate dissociation of the precursor deposit, produced conducting interconnects. The precursor has been demonstrated to be self-reducing and requires no reducing environment (e.g. H2) thus making the interconnect formation easier. Moreover, successful decomposition of the precursor into metallic Cu at such low temperatures holds promise for applications involving flexible polymer substrates.