Dual antireflection layers for ARC/hard-mask applications

Abstract

As the semiconductor feature size continues to shrink, the high NA lithography has become a reality. Coupling with high NA lithography, both the critical dimension control and the insufficient resist thickness for etch mask are becoming major challenges for lithographers. Hence two things are highly desired, one is an effective anti-reflective coating (ARC) strategy to maintain low reflectance for good critical dimension (CD) uniformity (CDU) control, and the other is combined ARC and hard-mask concept to satisfy both lithography and etch performance needs for feature patterning. In this study, a dual dielectric anti-reflective coating (dual-DARC) was first demonstrated as an effective ARC for contact application with high NA lithography. The ordinary single DARC is very sensitive to the thickness variation of underlying films, resulting in a >45nm contact CD variation at interlayer dielectric (ILD) thickness variation of ±150nm induced by CMP process. Unlike the single DARC, the dual-DARC performs a less CD variation of ~5nm at the same film thickness variation. By extending the dual-DARC concept to combined ARC/hard-mask application to contact and poly patterning, several ARC/hard-mask schemes were compared by reflectance control, CD uniformity control and etch hard-mask performance. Apart from the good reflectance and CD uniformity control of dual-DARC-like schemes, the most attractive is that the proper use of dual-DARC concept to hard-mask application, the tight thickness control is not necessary for the bottom layer and you can just tailor the bottom layer's thickness to meet the individual process needs.