Fine pattern fabrication property of binary mask and attenuated phase shift mask

Abstract

For 45nm and 32nm node technology, the challenges for resolution and CD control of mask patterns become the steeper mountain path. Especially, Sub Resolution Assist Feature (SRAF) is the smallest pattern on mask and amplifies the difficulty of mask fabrication. In order to improve the resolution of fine patterns, the influence of wet processing cannot be neglected, because it causes the pattern collapsing. Wet processing of mask-making can be divided into resist development and cleaning.In this study, the root causes of pattern collapsing are investigated at each wet processing. It is confirmed that thin resist can enhance the resolution limit of resist pattern and hard-mask blank, such as OMOG: Opaque MoSi On Glass, is suitable for thinner resist under 1500A. The pattern collapsing of OMOG is compared with that of Att.PSM at the cleaning before and after Cr stripping. Mask inspection finds that pattern collapsing can be suppressed by OMOG at both cleanings. It is because OMOG has lower cleaning stress than Att.PSM due to lower aspect-ratio. This benefit is demonstrated by cleaning stress simulation. Additionally, it is found that the SRAF size of OMOG can be wider than Att.PSM by optical simulation. From these results, OMOG has much advantage of fine pattern fabrication and is the optimal blank for 32nm node and beyond.

Hybrid source mask optimization for robust immersion lithography

“…In addition, a SPM is proposed to reduce the complexity of the source pattern. Hereafter, we focus on the 6% attenuated phase-shifting mask (AttPSM) due to its extensive application for the 45 nm technology node [ 21,22]. Through some minor modifications, the proposed algorithms in this paper can be straightforwardly applied to the applications of binary masks, alternating phase-shifting masks (AltPSMs), or unpolarized sources.…”