High-dynamic-range areal profilometry using an imaging, dispersion-encoded low-coherence interferometer

This work presents the design and characterization of an approach for areal surface profilometry with sub-nm axial resolution. The developed approach is based on a low-coherence interferometer enhanced by an dispersive element to control the axial resolution and measurement range. Optical path differences are detected by an imaging spectrometer where equalization wavelengths are determined as a basis for fitting spectra. This enables the acquisition of surface profiles with a length of up to 1.5 mm without mechanical scanning where a minimal resolution of 0.1 nm in an axial measurement range of nearly 80 µm was achieved. The resolution calculation was based on the standard deviation of measured feature heights. In addition to the system design, its capabilities are demonstrated on samples such as height standards.