Laser vaporization of metal films - Effect of optical interference in underlying dielectric layers

The interference of incident laser light with light reflected from dielectric interfaces is important in the completeness with which a laser beam vaporizes thin metal films, even though the dielectric layers lie underneath the metal film being vaporized. A structure consisting of titanium-platinum links on a two level dielectric consisting of silicon nitride and silicon dioxide on a silicon substrate was used to demonstrate the effect. The resistance of laser vaporized titanium-platinum links varied by more than seven orders of magnitude as the thickness of the silicon dioxide, the lower dielectric, was varied. The thicknesses of underlying dielectric layers are, therefore, parameters which must be taken into account when using a laser beam to produce high resistance open circuits in metal films.