Imaging validation for LS of dark field low-n vs Ta-based absorber masks

Abstract

In this work we continue to validate both by experiment and simulations the lines and spaces (LS) printing performance in terms of background printing and mask 3D effects with a dark field (DF) low-n absorber mask with 13% absorber reflectivity vs. a traditional Ta-based absorber mask. The brightness of the low-n absorber is the reason for a brighter background, what can have an impact on the remaining resist height after exposure. We experimentally verify by AFM the remaining resist height for different pitches through dose and through focus vs. the background for exposure with low-n and Ta-based absorber masks. It is also expected that such low-n absorber masks are more sensitive to mask 3D effects. Therefore, we study M3D effects on horizontal LS and 2Bars. There we evaluate Pattern Shift through focus as well as a 2Bar CD asymmetry through slit and through focus. We also measure MEEF for various LS pitches,