Aerial image contrast using interferometric lithography: Effect on line-edge roughness

Interferometric lithography affords the unique ability to independently control dose, pitch and aerial image contrast during photolithographic exposure. In this report, we describe the use of a deep-UV interferometric lithography exposure tool to study the impact of aerial image contrast on resist imaging properties. A wide range of high resolution resist materials was surveyed, including positive- and negative-tone systems, chemically amplified and conventional diazonaphthoquinone imaging chemistries, and aqueous- and solvent-developed systems. In all cases, resist line-edge roughness was observed to increase as aerial image contrast was decreased, though the precise behavior varied with resist material. Polymer molecular weight was systematically varied in a negative-tone chemically amplified resist formulation. The results indicate that molecular weight is a significant factor influencing the magnitude and type of line-edge roughness at low aerial image contrast.