Quantitative analysis of mask error effect on wafer CD variation in ArF lithography

Abstract

This paper describes the effect of the mask errors such as mask critical dimension (CD) variation, phase and transmission error of attenuated phase shifting mask (att-PSM) on wafer CD in ArF lithography and also analyzes these errors quantitatively. Mask CD requirement using ELF and MEF is estimated firstly and mask CD should be controlled within about 7nm assuming O.7ONA ArF system with 1% illumination uniformity. Transmission error induces larger CD variation than phase error. However, phase error should be considered otherwise in that it reduces depth of focus (DOF). To control DOF degradation less than 10% in case of O.l4um and O.l6um isolated contact hole(C/H), the phase should be controlled within the range of Considering O.l4um isolated contact hole, transmission error of occupies 10% of CD tolerance. Finally, the budget of these factors are calculated in view of total wafer CD variation quantitatively except lens aberration, resist process, and etc. To reduce wafer CD variation, we should control mask CD more tightly.

Tip characterization for CD-AFM: getting to 2 nm, 3 sigma

“…CD-AFM has enjoyed success in providing detailed data about sidewall shape and undercut on line features [1] and photomasks [2,3], but contact hole CD measurements and line-edge roughness [4] have been limited by the rectangular-shaped tips. Intrinsic tool precision can be less than 1 nm, yet tip limitations such as spatial frequency sampling and batch-to-batch shape variation can ultimately limit performance in the fab.…”