Katsuki Ito

Leading-edge adamantyl polymers designed for 193 nm lithography

There are some practical candidates for next generation lithography (NGL). However, many subjects are left behind and there is still no effective technique. One of those subjects is reduction of line edge roughness (LER)/line width roughness (LWR). As compared with 2-methyl-2-adamantyl methacrylate which is mostly used in 193nm lithography as acid cleavable monomer, it became clear that our new monomers were effective in reduction of LER/LWR by measuring surface roughness (Ra) with the analysis of atomic force microscopy (AFM). We found out that the monomers which have acetal as acid cleavable unit has high exposure sensitivity and effective in the reduction of Ra. Moreover, we tried to synthesize high refractive index polymer by introducing a sulfur atom that is another subject of NGL. By synthesizing some monomers, it became clear that the bond type of sulfur atom affects a refractive index greatly. It was also checked that a refractive index and transparency have a relation of a trade-off. The adamantyl acrylate monomers are mostly used in 193 nm lithography due to their high transparency and excellent contrast after the development. We have designed and synthesized various monomers based on adamantane moieties from 65nm node forward the 32 nm node. So, we think that its our duty to challenge from the design of a monomer to those subjects for NGL.

Adamantane-based molecular glass resist for 193-nm lithography and beyond

The adamantane-based molecular glass resist were studied its functional capability for lithography process in this work. GR-5 represented adamantane-based molecular glass resist were described as compared with the conventional polymer for 193 nm lithography. Low molecular weight which is one of the features of the molecular glass resist are expected to reduce the line width roughness (LWR) and the line edge roughness (LER). We evaluated the surface roughness (Ra; arithmetic mean departures of roughness profile from the mean line) by using the atomic force microscopy (AFM) instead. GR-5 has actually lower Ra value of 0.345 nm after the exposure and the development process. As the result of the confirmation of the GR-5s performance between the refractive index (n) and transparency (T), although n value stood on over 1.8, T value was less than 30% at 193 nm wave length. It is not likely to solve the higher refractive index and the higher transparency simultaneously. Further the scope of the adamantane-based molecular glass resist to apply for the EUV lithograph was found.