Application of pixel-based mask optimization technique for high transmission attenuated PSM

Abstract

Sub-resolution assist features (SRAF) insertion using mask synthesis process based on pixel-based mask optimization schemes has been studied in recent years for various lithographical schemes, including 6% attenuated PSM (AttPSM) with off-axis illumination. This paper presents results of application of the pixelbased optimization technology to 6% and 30% AttPSM mask synthesis. We examine imaging properties of mask error enhancement factor (MEEF), critical dimension (CD) uniformity, and side-lobe printing for random contact hole patterns. We also discuss practical techniques for manipulating raw complex shapes generated by the pixel-based optimization engine that ensure mask manufacturability.

Inverse lithography for 45-nm-node contact holes at 1.35 numerical aperture

“…17. 9 MEEF was measured at three dense pitches near the resolution limit and was about 30% lower for 30% AttPSM, shown in Fig. 18, and so confirmed the simulated tendency.…”

“…These larger AF will be easier to resolve during the mask making process. 9 The conversion and simplification optimization procedure discussed in Sec. 2 was performed for a 30% AttPSM with an identical target layout.…”