Evaporation Behaviour of a Thinning Liquid Film in a Spin Coating Setup:
Comparison Between Calculation and Experiment
Abstract
We present comprehensive measurements of the evaporation behaviour, E,
of a thinning film during a hydrodynamic-evaporative spincoating
experiment. E, ω (rotational speed), and \nu (viscosity)
are the main control parameters of the process. The evolution of the
entire film thinning process can be described theoretically quite well
based on the bulk value of \nu of the deposited liquid
and with a process-specific (constant) E. The weighing in values of
\nu are easily accessible (calculations, literature
values, simple measurements). E is specific for the experimental
conditions and values cannot be found in literature. There is also no
generally accepted strategy to calculate E in advance. We analyzed our
experimental results in view of a theoretical prediction for E, which
was presented already some time ago by Bornside, Macosco, and Scriven,
but never tested experimentally. We find good agreement between theory
and experiment for many solvents and different! Accordingly, this
approach permits in advance the calculation of the evolution of the
entire hydrodynamic-evaporative film thinning in a spincoating process.
In addition, we present a general formula, which allows in the case of
spincoating mixtures of volatile solvents and nonvolatile solutes the
prediction of the final solute deposit based on literature data only.