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Abstract

An apparatus and method are provided for efficiently and effectively coating a substantially flat surface, i.e., a substrate, with a high-viscosity liquid chemical, such as photoresist. The flat surface is oscillated by rotating the surface in one direction and then repeatedly reversing the direction of rotation of the surface. The chemical is spread by both the centrifugal force of the rotation of the surface and the tangential force of the angular acceleration of the surface. The tangential force helps spread the chemical without prematurely overcoming the surface tension of the chemical resulting in a particularly effective coating using substantially less chemical. Chemical is alternatively spread by vibrating the flat surface. Vibrating applies to the chemical, in addition to radial, centrifugal force, if any, non-radial forces which are not directly opposed by surface tension. The chemical is therefore spread more evenly and efficiently without overcoming the surface tension of the chemical. Vibrating is accomplished either (i) by oscillating the surface with a low amplitude and a high frequency or (ii) by quickly moving the surface in a small, circular motion.

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First Claim