A Review of Thickness Measurements of Thick Transparent Layers Using Optical Interferometry

Thickness is a typical parameter related to length, of which measurements are conducted in various industrial fields, such as the automotive, aviation, ship-building, semiconductor, and display industries. Among various measurement techniques, optical interferometry is very attractive in terms of reliability owing to the direct realization of the metre. Moreover, the nature of this non-contact method is such that it does not damage samples. In this review, optical interferometric methods for measuring thicknesses of thick transparent layers are introduced through a discussion of basic principles and applications. With consideration of optical layouts and analysis methods of interference signals, monochromatic laser interferometry, low-coherence interferometry, and spectral interferometry are introduced and discussed in chapters 2, 3 and 4, respectively. With regard to spectral interferometry, the two different key technologies of spectrally resolved interferometry and wavelength-scanning interferometry are covered in different subsections of chapter 4.