Outlook for 157-nm resist design

We have measured the transparencies of a number of candidate resist materials for 157 nm, with an emphasis on determining which chemical platforms would allow resists to be used at maximum thicknesses while meeting requirements for optical density. Assuming an ideal resist optical density of 0.4, our findings show that all existing commercially available resists would need to be <90 nm thick, whereas specialized hydrocarbon resists could be made similar to 120 nm thick, and new resists based on hydrofluorocarbons, siloxanes, and/or silsesquioxanes could be engineered to be used in thicknesses approaching 200 nm. We also assess the tradeoff between these thicknesses and what current information exists regarding defects as a function of resist thickness.