Fluoropolymer resists for 157-nm lithography

Fluoropolymers are key materials for single-layer resists in 157-nm lithography. We investigated main-chain fluorinated polymers and found that the incorporation of fluorine atoms into polymer backbones such as that in tetrafluoroethylene and monocyclic monomers reduced their absorption coefficients to less than 1 micrometers -1 at 157 nm, while side-chain fluorinated polymers had absorption coefficients of 2 to 3 micrometers -1. The main-chain fluorinated polymers also showed good solubility in a standard alkaline developer and their dry-etching resistance was comparable to that of a ArF resist. Prototype positive-tone resists had good sensitivities of less than 10 mJ/cm2, and they exhibited fine imaging resolution with 80-nm dense patterns. The resists can be used to obtain 300-nm-thick films.