Progress of Resist Materials and Process for hp 2x-nm Devices using EUV Lithography

Extreme ultraviolet (EUV) lithography is the leading candidate for the manufacture of semiconductor devices at the hp 22 nm technology node and beyond. The Selete program covers the evaluation of manufacturability for the EUV lithography process. Then, we have begun a yield analysis of hp 2x nm test chips using the EUVI (Nikon) full-field exposure tool. However, the resist performance does not yet meet the stringent requirements for resolution limit, sensitivity, and line width roughness. We reported on Selete standard resist 4 (SSR4) at the EUVL Symposium in 2009. Although it has better lithographic performance than SSR3 does, pattern collapse limits the resolution to hp 28 nm. To improve the resolution, we need to optimize the process so as to prevent pattern collapse. An evaluation of SSR4 for the hp 2x nm generation revealed that a thinner resist and the use of a tetrabutylammonium hydroxide (TBAH) solution for the developer were effective in mitigating this problem. Furthermore, the use of an underlayer and an alternative rinse solution increased the exposure latitude by preventing pattern collapse when the resist is overexposed. These optimizations improved the resolution limit to hp 22 nm.