High-spatial-resolution nulling microellipsometer using rotational polarization symmetry

We report the design and experimental testing of a high-spatial-resolution nulling microellipsometer. This microellipsometer design is based on the previously reported principle of rotational polarization symmetry to improve the signal-to-noise ratio of spatially resolved ellipsometric measurements. Through the use of an electro-optic polarization rotator, a null detection scheme is made possible and implemented. Surface profiling of a lithographically patterned microstructure is demonstrated with the nulling microellipsometer. A lateral spatial resolution of 0.48 microm is calculated with a numerical aperture of 0.9 and an illumination wavelength of 632.8 nm.