Abstract

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, ${\varphi }_{\mathrm{model}}\left(k\right)=2\mathit{kh}+\psi \left(k,d\right)+(\mathrm{offset})$, 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 $\sim 10 \mathrm{nm}$.

© 2002 Optical Society of America

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