Effect of process related and haze defects on 193nm immersion lithography

Abstract

In this article, the effect of a defective mask on 193nm immersion lithography with a 6% attenuated phase-shifting mask is investigated. Two types of defect are studied: process related defect and haze defect. Several factors including defect location, size, transmission, phase, and illumination settings are considered. Exposure using a standard 45nm SRAM cell shows that the printability of a defect on a mask depends on the pattern density and defect size and it is also shown that the impact of a defect on a polysilicon gate layer is worse than that on an active layer. A defect that is adjacent to a main feature causes more critical dimension (CD) variation than that between two main features. Simulation using a through pitch line and space pattern is used to investigate the impact of a haze defect. A change in transmission results in an increase in the CD variation in the main feature but not the critical defect size. However, a larger phase difference between the defect and background would increase the CD variation and reduces the critical defect size. Illumination with a low partial coherence setting increases the CD variation caused by defects.