Modelling of Pyrolytic Laser Direct-Writing from Thin Metalorganic Films

ABSTRACTA one-dimensional model for pyrolytic laser direct-writing of metal features from thin metalorganic films is presented. The model extends previous results for scanning laser crystallization by including separate but coupled mass and energy balances and allowing for variations in the optical properties and thermal conductivity in the film as it decomposes. A finite element approach is used to obtain solutions to the steady state and transient model forms. The model predicts the existence of multiple steady states for a range of laser powers when the optical absorbance is a nonlinear function of the fractional conversion in the film. These predictions agree qualitatively with multiple steady states that have been observed in direct-writing of palladium features from palladium acetate films. Experimental results that demonstrate multiplicity in the palladium acetate system are presented. The model also predicts the existence of periodic solutions that correspond to the periodic features that have been reported for direct-writing of gold features from organogold films.