Model of coating and drying process for flat polymer film fabrication

The coating procedure of polymer solutions by the scanning technique is developed for LSI technologies at the next generation, where a polymer solution as resists and inter-layer dielectric films is coated on a flat substrate, and then only the solvent is vaporized and removed, and finally the thin film is remaining there. In case of applying to the photo-lithography process, scan coating and its drying processes work together for astonishing flatness in 1% fluctuation range. When the coated polymer solution is dried under reduced pressure or vacuum, the thickness distribution of the resultant film should be accurately prospected and controlled by parameters. The film thickness is generally thicker at the edge and thinner inside from there than the average thickness. A typical thickness profile of a resist film is shown in Figure 1 . The phenomena are always observed, but have not been analyzed numerically. In this paper, we report a numerical model of the drying process of liquid film including polymers and give the essential parameters to the coating and drying processes. The parameters are focused on a vaporization rate, diffusion coefficients, coated solution thickness and intrinsic viscosity, which were calculated by simplified dynamical models of Langmuir's vaporization rate equation and Einstein relation at complex polymer solutions.