Topographic Substrate Leveling During Spin Coating.

The effect of spinning speed, hole width w, initial film thickness h sub o, hole depth and radical position of the hole R on the leveling (planarization) of square holes on a silicon substrate during spin coating was investigated. The degree of leveling increased with decreasing spinning speed, decreasing hole width and increasing film thickness, but was independent of hole depth. Holes nearer the center of the spinning substrate were planarized better than those nearer the substrate edge. Experimental data for a liquid epoxy film that was hardened during spin coating by uv irradiation fell on a single curve when planarization was plotted against omega sup 2 w sup 3 R/h sub o where omega is the substrate angular velocity. The data for a positive photoresist film that hardened when the spinning solvent evaporated formed a similar curve, but at lower planarization values because the solvent evaporation caused film shrinkage and degradation of planarization. Topographic substrate leveling during spin coating is determined by the forces acting on the film and film shrinkage. It is shown that these two factors can be treated separately to predict the degree of topographic substrate leveling during spin coating.