The effect of extra doses at the pattern edges on negative electron resist profiles

Abstract

Theoretical and experimental studies have been performed to improve a quality of negative electron resist patterning of an infinite array of 1, 2, and 3 μm lines and spaces. We examined the effect of extra doses at the line pattern edges on their cross sectional profiles. Experiments were carried out using a PGMA resist with an electron beam exposure system of EBMG-40 at 10 keV. The cross sections were observed with a scanning electron microscope. It was found that a horned shape at the edges produced by extra doses had a favorable effect on the profiles during O2 plasma treatment to remove scum. It kept the edges from rounding due to a faster etching rate. The results showed some improvement in both the linewidth and the edge slope. An analysis of experimental cross sections has also been performed based on the so-called contrast curve. From a comparison between theory and experiment we found that the patterns seemed to shrink by 30% to 50% in the lateral direction, depending on the linewidth. A theoretical approach is useful for investigations into the characteristics of negative electron resists.