Laser-Enhanced sputter or vapor deposition of thin metallic films on ceramic substrates

Abstract

Laser-assisted sputter deposition has been used to deposit thin metallic films onto ceramic substrates. This process allows the building of a film of arbitrary thickness by sequential deposition of 5- to 150-nm-thick layers alternating with laser melting. Highly adherent films of copper on sapphire and on quartz were obtained. Pulsed-laser treatment also enhances the adhesion of nickel films to sapphire substrates. This critical step in the process is the laser irradiation following each of the initial depositions. In these early stages, an interfacial reaction between film and substrate takes place during laser irradiations. An interfacial compound forms whose nature has been studied by transmission electron microscopy. The morphological features of the film, as well as the amount of film removed during these first irradiations, were analyzed as a function of laser energy density by scanning electron microscopy and by energy dispersive X-ray spectroscopy. The results were correlated with computer simulations of the thermal response of the two-media system to laser heating. The role of the interfacial thermal conductivity during laser processing is analyzed. The state of the substrate,e.g., annealed or as-polished, influences the morphology of the irradiated film. This effect is related to an enhancement of interfacial thermal conductivity.