Possible line edge roughness reduction by anisotropic molecular resist

Abstract

Extreme ultra-violet (EUV) lithography technology is being developed for the patterning of sub-22nm node. Line edge roughness (LER) is the one of the important issues together with the resist performance like resolution and sensitivity. There are some novel resists for EUV lithography that can be used for obtaining the target resolution and sensitivity, while the line edge roughness do not reached the target values in most resist yet. In order to reduce the LER, the molecular resist has been widely studied due to their small size compared to the conventional polymer resist. There is another approach to reduce the LER by reducing the acid diffusion length, but it is not easy to reduce down the acid diffusion length. We tried a new approach to reduce down the LER by changing the shape or structure of the molecular resist. A new molecular resist shape that shows the anisotropic structure is tried to see the LER and whether this anisotropic resist can be used for LER reduction. It turns out that the LER is minimum when the molecular chain alignment is along the depth, while LER is maximum when the molecular chain is randomly distributed.