Rapid thermal reduction of inkjet printed Cu interconnects on glass substrate

We report on rapid thermal reduction of inkjet-printed Cu interconnects in nitrogen and hydrogen mixture ambient to change the insulating Cu₂O to conductive Cu for solution-based all printable thin film transistors fabricated on a glass substrate. By ink-jetting and rapid thermal annealing of nano Cu ink with an average size of ∼6 nm, we were able to obtain directly patterned Cu interconnects with resistivity of 2.2 × 10^-6 ω cm and line width of ∼50 m. Synchrotron x-ray scattering and x-ray photoelectron analysis showed that as-printed Cu interconnect, which existed in the Cu₂O phase was completely transformed to metallic Cu interconnects after rapid thermal annealing due to effective reduction by H ₂ gas and sintering of inkjet-printed Cu that have a lower melting point than bulk Cu.