Manufacturing of nanoscale thickness gold lines by laser curing of a discretely deposited nanoparticle suspension

The present work is focused on a novel method for the manufacturing of electric microconductors for semiconductors and other devices. Three different technologies are combined in this technique: controlled (drop on demand) printing, laser curing, and the employment of nanoparticles of matter, possessing markedly different properties (here, melting point) than their bulk counterparts. A modified on demand ink jet process is utilized to print electrically conducting line patterns from a suspension of gold nanoparticles in toluene. Microdroplets of 60–100 μm diameter are generated and deposited on a moving substrate such that the droplets form continuous lines. Focused laser irradiation is utilized in order to evaporate the solvent, melt the metal nanoparticles in the suspension, and sinter the suspended particles to form continuous, electrically conducting gold microlines on a substrate. The ultrafine particles in the suspension have a diameter size range of 2–5 nm. Due to curvature and surface effects of such small particles, the melting point is markedly lower than that of bulk gold (1063 C). Atomic force microscopy and scanning electron microscopy have been employed to investigate the topology of the cured line. In situ visualization of the curing process has been conducted. Results on the effect of the laser irradiation power on the topology and width of the cured line, which is directly related to the electrical conductivity, are reported.