High etching selectivity of spin-on-carbon hard mask process for 22nm node and beyond

As part of the trend toward finer semiconductor design rules, the resist film thickness is getting thinner, and the etching technology that uses resist masking is getting more difficult. To solve such a problem in recent years, the film structure used in the resist process also is changing from the single-layer process (BARC and resist stacked film) to the multi-layer process (Carbon hard-mask, middle layer and resist stacked film) The carbon hard-mask of multi-layer process can be divided into two kinds, which are the CVD-carbon (CVD-C) that uses the chemical vapor deposition method and Spin-on-carbon (SOC) that uses the spin-coating method. CVD-C is very attractive for ensuring the high etching selection ratio, but still has major challenges in particle reduction, lower planarization of substrate and high process cost. On the other hand, SOC is very attractive for low cost process, high level of planarization of substrate and no particles. Against this background, we verify the development of the SOC that had the high etch selection ratio by improving etching condition, material and SOC cure condition. Moreover, we can fabricate below 30nm SiO2 patterning and the possibility of development with extreme ultraviolet lithography (EUVL) was suggested. This paper reports on the results of a comprehensive process evaluation of a SOC based multi-layer technology using lithography clusters, etching tools.