A Novel Plasma Treatment Method to Improve DUV Photoresist Footing on Inorganic Anti-Reflective Layer (ARL)

摘要

In this paper, a novel plasma treatment technique is propc sed to resolve DUV photoresist footing problem on inorganic ARL. The inorganic dual ARL layers for damascene application have been developed with optimal refractive index (n), extinction coefficient (k) and thickness (T) composition. These dual layers provided better critical dimension control than single ARL layer. However resist footings were observed on the developed DUV resist. Therefore, different plasma treatments were tried to examine the usefulness of removing surface amino groups. The plasma treatment chemistries used in this study are O_2, Ar, N2 am N_2O. ESCA high-resolution spectrum was used to identify the mechanism of this nterface reaction. The chemical bonds of Si-NH-Si and Si-NH_2 groups are presented on the surface of PECVD DARL from ESCA analysis. The PECVD ARL was also examined by FTIR. The interesting thing is that these amino groups can not be detected in film except Si-N (850 cm~(-1)) by FTIR. Therefore it is concluded that the amino groups only exist on the surface of PECVD DARL rather than in the bulk of film. The ESCA results indicate that the Ar plasma is most effective treatment to remove amino groups on surface. The detailed comparison of various plasma treatments in term of final surface roughness, reflectance and damascene application is given in this paper.