Temperature effects in the photolytic LCVD of platinum

The photolytic laser chemical vapor deposition (LCVD) rate of platinum from its bishexafluoroacetylacetonate precurser has been measured in situ and in real time. Optical transmission of the 350 nm photolysis light through the deposited platinum film and a transparent glass substrate is monitored and analysed in detail. From these measurements, as well as measurements of the reflected light, the fraction of the laser beam power absorbed in the metal film is found. The latter allows a simple estimate of the laser-induced temperature rise at the metal surface. It is shown that even rather small temperature increases of the order of several tens of degrees centigrade can completely change the photolysis mechanism and hence drastically influence the photolytic LCVD rate. A simple modification of Lax's model, in which a temperature dependent thermal conductivity of the substrate is introduced, is used to describe the laser-induced heating of a strongly absorbing thin metal film on a glass substrate.