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.

Option of resolution enhancement technology in advanced lithography

“…DL-BARCs design has been studied in order to reduce standing wave and CD swings in hyper-NA lithography by different methods [2][3][4] . However most studies emphasize the optimization of thickness of BARCs by getting minimum reflectivity at the interface of resist /BARC or resist/air.…”

“…However hyper-NA immersion lithography and adoption of RET cause light to diffract at big angles. The image in a resist are formed by oblique waves, where the oblique incident angle and polarization will yield increased reflectance both at air/resist and resist/substrate interfaces, consequently results in an increase in both the standing wave and critical dimension (CD) swing [1][2][3] . On the other hand a cross talk of PSM, OAI, polarization effect, and resist process design impact on lithography performance significantly.…”

“…Hence an option of RET in conjunction with polarized illumination and optimization of DL-BARC structure is required to maintain a small CD, good CD uniformity (CDU), reasonable process window (PW) and fidelity of resist profile. The optimized l DL-BARC structure has been studied in hyper-NA immersion lithography previously [2][3][4] . People were trying to explored the feasible parameters of DL-BARC that does not depend on the polarization, illumination conditions, pattern size and pitches for cases of NA being 1.0, 1.1, 1.2, and 1.3 to 1.4 with tunable complex index of BARC 4 .…”