Planarization of substrate topography by spin coating.

This paper reports the results of a study of topographic substrate planarization with films applied by a spin-coating process. We show that spin coating produces conformal films over wide (>50micron) gaps on the substrate and that filling of the gaps only occurs after spinning has ceased provided the film is able to flow. A comparison of the major forces acting on the film leads to the conclusion that the flow is driven primarily by capillary forces when the width of the gap is less than 5000micron. A theory is developed that relates the time required to fill the gaps to their width and height and to the thickness and viscosity of the film. The results of experiments performed to test the theory are presented and discussed.