The effect of adsorbed cationic surfactant on the pattern collapse of photoresist lines in photolithographic processes

Abstract

A crucial problem in the manufacturing of high aspect ratio structures in the microchip production is the collapse of photoresist patterns caused by unbalanced capillary forces. A new concept to reduce the pattern collapse bases on the reduction of the capillary forces by adsorption of a cationic surfactant. The application of a cationic surfactant rinse step in the photolithographic process leads to a reduction of the pattern collapse. Physicochemical investigations elucidate the mechanism of surfactant adsorption and its effect on the surface properties of the photoresist. It is shown that the best pattern collapse reduction is obtained at a surfactant concentration referring to monolayer coverage. In this concentration range the capillary forces are minimized due to a hydrophobizing of the processed photoresist by adsorbed cationic surfactant. © Springer-Verlag Berlin Heidelberg 2006.