“Laser printing for micro and nanofabrication”
– Delaporte Philippe –
Laser-induced forward transfer (LIFT) is a printing process allowing the deposition of a small amount of material in solid or liquid phase with high resolution. Many LIFT-based approaches have been developed to adapt this process to the material properties and to the targeted application. Among the different applications, the realization of conductive structures is of special interest, especially for the microelectronic applications. This presentation is focused on the transfer of metal based materials in liquid phase. The film is first deposited on a transparent substrate and the focused laser pulse irradiated the film through the substrate. That induces the motion of the film and the formation of a jet that expands toward a receiver substrate located in front of the donor one to form a droplet. Two studies will be presented: first the printing of conducting lines at high velocity and second the printing of metal at the nanoscale.
The fabrication of conducting structures has been performed from films of silver nanoparticle inks with different properties (viscosity, surface tension, ink content) and the dynamics of the jets has been studied by means of time resolved shadowgraphy. Interconnection lines of 10µm width has been printed at velocity up to 17m/s. In order to reduce the size of the printed droplet, a double pulse LIFT setup has been developed. The donor film is a solid metal layer deposited on a glass substrate and a first laser locally melts the metal while a second short pulse focused in the center of the molten pool induces the formation of the liquid metal jet and the deposition of a metal droplet on the receiver substrate. Droplets with diameter as small as 500nm has been printed thanks to this new approach.