Nucleation and growth of low resistivity copper thin films on polyimide substrates by low-temperature atomic layer deposition

Abstract

The metallization of polyimide (PI) remains a formidable challenge when using an atomic layer deposition of copper. The present study employs Cu(hfac)2 and Et2Zn to deposit the copper thin films that are highly conformal and continuous, and possess low resistivity (5.6 μΩ·cm), through a low-temperature atomic layer deposition (120 °C) with multi-pulse of Cu(hfac)2 process on a treated polyimide surface. The process exhibited both self-limiting ALD and CVD-like reactions with a growth rate of 0.079 nm/cycle. The findings demonstrate that an increase in functional groups and adsorption area on the surface of treated PI substrates enhances the adsorption of Cu(hfac)2. A model has been developed to describe the nucleation and growth kinetics of atomic layer deposition of copper on polyimide substrates, based on the adsorption mechanism of Cu(hfac)2 and the interface structure of ALD-Cu/treated PI onto the surface and into the near-surface region of the PI substrates. The academic developing in this work provides theoretical and experimental basis for the deposition using other copper precursors onto polymeric substrates in the future.