Resists for sub-100 nm patterning at 193 nm exposure

摘要

Current resist materials suffer from a number of problems which must be addressed to allow continued scaling of memory and logic devices. The incompatibility of the photoacid generator (PAG) and the polymer matrix is addressed in this study. This incompatibility leads to lowered acid generation efficiency, non-uniform acid distribution and migration, and phase separation. These issues ultimately lead to undesirable, premature and non-uniform deprotection reactions in the chemically amplified resist. To alleviate these problems, it is proposed that PAG units be incorporated in the resist chain to make a one-component resist, rather than blending monomeric PAG with the resist polymer. Also, polymer bound PAG resists exhibit higher stability, lower outgassing, and lower line edge roughness (LER) than corresponding resists. The polymer bound PAG resists, poly (γ-butyrolactone methacrylate-co-2-ethyl-2-adamantyl methacrylate-co-PAG), were synthesized using free radical polymerization. PAG incorporated resists, as well as PAG blended resists were exposed using the 193 nm ASML 5500/9xx optical lithography system, with 0.63 NA. Exposed wafers were evaluated using SEM. The triflate PAG incorporated resists provided 110 nm (220 nm pitch) line space features, and 80 nm isolated features. The PAG blended resists provided 130 nm (260 nm pitch) line space features. The associated photospeed for the 110 nm line space features was 8.2 mJ/cm~2, which is within road map standards.