Molecular design and development of photoresists for ArF excimer laser lithography

Positive-tone and negative-tone resists for ArF excimer laser lithography are developed from novel polymers, which are called functionally-integrated polymers having polar alicyclic units. The fundamental unit of the polymers is an acrylate having a tetracyclododecane group with a carboxyl end group, which satisfies a lot of the requirements of ArF resists. A typical monomer is carboxy-tetracyclo[4.4.0.12,5.17,10]dodecyl methacrylate. In 1996, we established 0.15-µm “positive” line-and-space patterns at 21.8 mJ/cm2 using an ArF exposure system (0.55 numerical aperture), which meet the design rule requirement for fabricating 1-gigabit dynamic random access memories (DRAMs). This fundamental polymer unit has also been used to develop negative-tone resists for ArF lithography. In 1999, we also established 0.13-µm “negative” isolated line pattern at 7.1 mJ/cm2 using an ArF exposure system which fulfills the design rule requirement for logic circuits combined with gigabit DRAMs.