Step Coverage and Dry Etching Process Improvement of Amorphous Carbon Hard Mask

Abstract

Amorphous carbon hard mask (ACHM) films have been widely applied as protective components and hard etching masks in lithography and dry etching processes. The capability of lithography is directly dependent on the step coverage (SC) of the ACHM. Poor SC may impact the protection of device patterns during the etching process and lead to overlay marks occurring in lithography. In this work, the ACHM film processing process is engineered and optimized towards better SC through the comparative study of the C2H2 and C3H6 precursors at different temperatures. Furthermore, a process parameter design of experiment (DOE), with C2H2 as a precursor to optimize the dry etching rate, is proposed. The results of the experiment show that the dry etching performance is enhanced by higher power, temperature and C2H2 flow, and a smaller gap, lower pressure and lower carrier gas flow. A selective etching ratio of SiO2 and SiN, with an improved process window, is obtained. ACHM film elimination process is also validated by characterizing the surface roughness. The demonstrated results can be instructive in terms of the optimization of etching process in future semiconductor manufacturing.