Comparative linewidth measurements on Chrome and MoSi structures using newly developed microscopy methods.

Inspection and linewidths measurements of subwavelength structures using optical microscopy are severely confined both by the limited resolution and by a manifold of light-structure interactions affecting the optical image. To receive a better understanding of these interactions and/or to overcome these limitations, new microscopy methods have been developed: Polarisation-interference-microscopy permits the accurate measurement of the birefringence which is induced by the form of the structures. By interferometric comparison of the TE and TM-polarized image this method provides selective edge detection and localisation in the subwavelength regime because the polarisation difference is situated at the topographical changes of the structure. Two new methods of dark field microscopy "alternating grazing incidence dark field microscopy" and "frustrated internal total reflection microscopy", make it possible to suppress optical proximity effects and to overcome the resolution limit of conventional dark field microscopy. For a characterisation of the qualitative and quantitative influence of different variables on measurements of the size of subwavelength structures we performed comparative linewidths measurements on Chrome and phase shifting MoSi photomask structures. The deliverables are compared with rigorous numerical simulations.