A simultaneous volumetric thickness-profile measurement method based on an acousto-optic tunable filter for transparent film deposited upon pattern structures is described. The nondestructive thickness profilometer prevents the destruction of samples such as one encounters in using a scanning-electron microscope and provides good accuracy. The information on the volumetric thickness profile is obtained through least-squares fitting with a phase model, ø(model)(k)=2kh+? (k, d)+(offset) , which has three unknowns: surface profile h, thickness d, and an indeterminate initial phase offset. Accurate phase information in the spectral domain can be obtained by introduction of the concept of spectral carrier frequency. Experimental results for a metal patterned sample show that the volumetric thickness profile can be determined within an error range of ~10 nm .
A white light on-axis digital holographic microscopy based on spectral phase shifting is described. We show experimentally that the spectral phase shifting based on-axis digital holographic microscopy can be used as an alternative to the PZT based phase shifting digital holographic microscopy. The proposed spectral phase shifting approach can provide a speckle-free capability since it employs the partial coherent source produced by combining a white light source and a spectral tunable filter. Another benefit of the proposed white light on-axis digital holographic microscopic system stemmed from spectral phase shifting approach is in the capability of providing a full color 3-D spectral section imaging.
In this communication, we describe a fast thickness profile
measurement method for a transparent film, thinner than the
white-light coherence length of 3-4 µm that is deposited on
pattern structures. A visible acousto-optic tunable filter is
employed for real-time wavelength scanning and the three-dimensional
volumetric thin-film thickness profile information is obtained using
a simple peak detection method in the spectral domain. The key idea
is to divide the measurement into two states using a beam blocking
mechanism to separately obtain the two unknowns of thickness and
surface profile. Such separate measurements are required to
compensate for the phase change effect caused by the multi-reflected
beams from the thin film. The final thin-film surface profile
information is measured by obtaining the number of peaks and phase
deviations from the two separately scanned spectral intensity values.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.