Analysis and modeling of photomask edge effects for 3D geometries and the effect on process window

Abstract

Simulation was used to explore boundary layer models for 1D and 2D patterns that would be appropriate for fast CAD modeling of physical effects during design. FDTD simulation was used to compare rigorous thick mask modeling to a thin mask approximation (TMA). When features are large, edges can be viewed as independent and modeled as separate from one another, but for small mask features, edges experience cross-talk. For attenuating phase-shift masks, interaction distances as large as 150nm were observed. Polarization effects are important for accurate EMF models. Due to polarization effects, the edge perturbations in line ends become different compared to a perpendicular edge. For a mask designed to be real, the 90 o transmission created at edges produces an asymmetry through focus, which is also polarization dependent. Thick mask fields are calculated using TEMPEST and Panoramic Technologies software. Fields are then analyzed in the near field and on wafer CDs to examine deviations from TMA.

Extensions of boundary layer modeling of photomask topography effects to fast-CAD using pattern matching

“…1 In addition to amplitude errors induced by electromagnetic field (EMF) effects, phase errors are present and create asymmetric imaging through focus. Additionally, these effects are dependent on λ, not resolution and therefore do not scale with technology node.…”