Optimization and characterization of drop-on-demand inkjet printing process for platinum organometallic inks

Inkjet printing has been extensively used over the past 30 years in the graphic arts and packaging industries. This technology involves dispensing accurately positioned droplets of ink onto a substrate, which then solidifies through the evaporation of the constituent solvent, the cross-linking of a polymer or through crystallization. The mask-less, flexible, rapid and low cost nature of inkjet printing, combined with the development of a range of functional inks, has led to the adoption of this technology in system manufacturing. The SMART Microsystems research project underway at the Institute for Integrated Systems is investigating the use of this technique in the rapid customization of CMOS foundry wafers for More-than-Moore applications. This paper presents results obtained during the development and optimization of a drop-on-demand inkjet printing process for initial batches of platinum organometallic inks. Drop-on-Demand (DOD) inkjet printing works by inducing a transient pressure pulse in the ink reservoir through electrical excitation of either a thermal or piezoelectric element. The correct implementation of this excitation signal is necessary to produce a pressure pulse capable of reproducibly and reliably generating a series of droplets. The effects of system parameters on the formation of these droplets are investigated. Methods used to characterize droplet ejection are also described.