Interferometric precision measurement of highly reflective thin film using wavelength tuning Fizeau interferometry

摘要

Indium tin oxide (ITO) thin films have been widely used in displays such as liquid crystal displays and touch panelsbecause of their favorable electrical conductivity and optical transparency. The surface shape and thickness of ITO thinfilms must be precisely measured to improve their reliability and performance. Conventional measurement techniquestake single point measurements and require expensive systems. In this paper, we measure the surface shape of an ITOthin film on top of a transparent plate using wavelength-tuning Fizeau interferometry. The surface shape was determinedby compensating for the phase error introduced by optical interference from the thin film, which was calculated using thephase and amplitude distributions measured by wavelength-tuning. The proposed measurement method achieved noncontact,large-aperture, and precise measurements of transparent thin films. The surface shape of the sample wasexperimentally measured to an accuracy of 40 nm, mainly limited by the accuracy of the reference surface of 30 nm.