Improved Electrical Resistivity of Atomic-Layer-Deposited Copper Thin Films on Polyimide Substrates by an In Situ ZnO Interlayer.

ABSTRACT

The low-temperature atomic layer deposition of metal on polymer surfaces is often challenging owing to the deficiency of functional groups and reactivity. Here, the deposition of ALD-Cu employing Cu(hfac)2 and Et2Zn at a low temperature (120 °C) on polyimide (PI) substrates is improved by the utilization of an in situ ultrathin ALD-ZnO buffer layer. A conformal and continuous ALD-Cu thin film with low resistivity (6.07 µΩ cm) is fabricated on an ALD-ZnO/PI substrate. The findings demonstrate that the ALD-ZnO buffer layer provides chemisorption and a nucleation site for the initial growth of ALD-Cu. Transmission electron microscopy and energy-dispersive X-ray analysis reveal that the ALD-ZnO layer plays a buffer role in the fitness of ALD-Cu on PI substrates and its ability to elicit the formation of an ALD-ZnO nanocluster and polar surface. ALD-ZnO can be effectively utilized as a buffer layer for polymer-based ALD-metal processes, showing potential in flexible electronic applications.