Development of Multi-Function Hard Mask to Simplify Process Step

摘要

ArF lithography has been driven into sub-100 nm dimensions using high numerical apertures, phase-shift mask, modified illumination, and optical proximity correction. As feature size continues to shrink, photoresist thickness as an imaging layer has been decreased for the improvement of lithographic process window and pattern collapse margin. Moreover, ArF photoresist has the inherent demerit of poor etch resistance in comparison with KrF photoresist and we have to use inorganic hard mask materials such as silicon-nitride, -oxide, poly-silicon, and silicon oxynitride as a pattern transfer layer. The cost-of-ownership (COO) of CVD process related to the application of inorganic hard mask is much more expensive than that of spin-on process. Therefore, several processes including bi-layer resist process (BLR), and tri-layer resist process (TLR) have been investigated. This paper will focus on TLR process consisted of multi-function hard mask (MFHM) material and spin on carbon (SOC) material.