COMBINED FLOW AND EVAPORATION OF FLUID ON A SPINNING DISK

Fluid flow and fluid evaporation both contribute to the overall rate o f thinning during spinning of a fluid on a disk. Laser interferometry of solvent thinning behavior on spinning silicon wafers was performed to yield plots of solvent thickness evolution. These plots of thicknes s versus time were then analyzed to understand the respective contribu tions of viscous flow and evaporation to the thinning. A technique is described for extracting both the viscosity and the evaporation rate f rom the interference data. Well understood solvent systems are examine d as test cases for this deconvolution. It is also demonstrated that n onevaporating fluids can be analyzed, even though their thickness evol ution has no easily referenced endpoint to the thinning, in contrast t o the volatile solvents which are rapidly spun dry. (C) 1997 American Institute of Physics.