UV and DUV microscopy for dimensional metrology on micro- and nanostructures

摘要

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. A straightforward way to improve the resolution is the reduction of the wavelength of the imaging radiation to the UV or DUV spectral range. But changing the wavelength will be accomplished by a modification also of the interaction between the light and the specimen. This modification also affects the contrast mechanism and therewith also the signal to noise ratio for various microscopy methods in a different way. Additionally the quality of the structure edge localisation may be affected due to changing field displacement effects in the field structure interaction. We investigated theoretically the changes of the contrast mechanisms for different microscopy methods between visible, UV and DUV microscopy for different materials like Chrome, SiO_2 or Silicon. The investigated methods are bright field reflection microscopy, confocal microscopy and a newly developed dark field method using alternating grazing incidence illumination. The calculations are based on rigorous diffraction calculation.