Copper Interconnects Based on Copper(I) Oxide Particle-Based Precursor Ink Technology-Material Composition Optimization and Reliability

Abstract

Recently, printed electronic devices built on flexible plastic substrates have gained considerable market share in the consumer electronics area. In these devices, the conducting metal lines connecting various components are typically fabricated using a low-cost metal or metal oxide particles-based ink technology in contrast to conventional/expensive photolithography with subtractive or additive metal deposition technology. In this paper, fabrication of Cu metal lines over glass was evaluated by application of Cu(I) oxide Cu2O nano-particle-based ink precursor material consisting of an organic polymer reducing agent dispersed in a simple organic solvent and subsequently reducing the oxide particles through a laser beam-based sintering/ reduction process. The ink precursor composition was optimized for the lowest specific resistivity values of the fabricated Cu lines by varying the Cu2O particle weight %, ratio of nano-particle to the organic polymer reducing agent and the molecular wt. of the polymer. The reliability of these Cu lines was tested by baking them upto 400 degrees C and it was determined that the use of an organic polymer reducing agent can protect the Cu from oxidation around 370 degrees C without affecting the specific resistivity value. Detailed analyses of the metal lines fabricated with this technology are discussed using X-ray diffraction study for metal/metal oxides contents and Fourier transform infrared spectroscopy for an organic polymer degradation mechanism. In addition, application of Cu2O nano-particle-based precursor technology to repair open circuit lines has been demonstrated.