Investigation of New Slection Citeria for an Otimized Imersion Process

Since the introduction of immersion lithography, leaching has become an important topic in screening new resist materials. It is considered as a possible source for lens contamination, but also it is expected to introduce new defect mechanisms. Protective topcoats have proven their use as leaching barriers, but care is needed when introducing them. They can have an impact on CD control and the defect behaviour of the immersion process. In this paper, a method is proposed to characterize leaching. It has been applied to investigate several cases. Next to that, water uptake and the formation of an intermixing layer in between resist and topcoat have been investigated with respect to their contribution to CD variations and defectivity.