Method of forming coating film on a substrate

Abstract

According to the invention disclosed, application liquid such as spin-on-glass (SOG) is dropped on the surface of a substrate such as a semiconductor wafer having irregularities thereon and is dispersed on the substrate surface using a centrifugal force generated by rotating the substrate. The rotation of the substrate is performed in a first rotational action at a low speed and a second rotational action at a high speed, the first and second rotational actions being separated by a time interval. The second rotation may be at a constant speed. Alternatively, the rotational speed of the second rotational action may comprise rotation at an intermediate speed continuously followed by rotation at a higher speed. The time interval between the first and second rotational actions is ten times the duration of the first rotational action or longer. The duration of the second rotational action is three times that of the first rotational action or longer. Such time interval and relative durations make the application liquid more conformable to the substrate surface and causes the application liquid to be sufficiently dispersed on the substrate to provide a film having the desired thickness on the substrate, even though the substrate has irregularities thereon.