Abstract
Scanning White Light Interferometry is a well-established technique for providing accurate surface roughness measurements and three dimensional topographical images. Here we report on the use of a variant of Scanning White Light Interferometry called coherence correlation interferometry which is now capable of providing accurate thickness measurements from transparent and semi-transparent thin films with thickness below 1μm. This capability will have many important applications which include measurements on optical coatings, displays, semiconductor devices, transparent conducting oxides and thin film photovoltaics. In this paper we report measurements of thin film thickness made using coherence correlation interferometry on a variety of materials including metal-oxides (Nb2O5 and ZrO2), a metal-nitride (SiNx:H), a carbon-nitride (SiCxNy:H) and indium tin oxide, a transparent conducting oxide. The measurements are compared with those obtained using spectroscopic ellipsometry and in all cases excellent correlation is obtained between the techniques. A key advantage of this capability is the combination of thin film thickness and surface roughness and other three-dimensional metrology measurements from the same sample area.
Highlights
Thin film thickness measurements with sub-nanometre accuracy are important in a range of applications such as thin film optical coatings, displays, semiconductor devices, thin film photovoltaics, thin film transparent conducting oxides
These metrology measurements are made using a variety of techniques including stylus profilometry, Atomic Force Microscopy, Scanning Electron Microscopy and Scanning White Light Interferometry (SWLI)
We report on the use of a variant of SWLI called coherence correlation interferometry (CCI) [1] which is capable of combining sub-nanometre thin film thickness measurements with quantitative three-dimensional metrology and imaging from the same thin film sample area
Summary
Thin film thickness measurements with sub-nanometre accuracy are important in a range of applications such as thin film optical coatings, displays, semiconductor devices, thin film photovoltaics, thin film transparent conducting oxides. In display or photovoltaic devices, roughness of the transparent conducting oxide contact can lead to shunting of the devices These metrology measurements are made using a variety of techniques including stylus profilometry, Atomic Force Microscopy, Scanning Electron Microscopy and Scanning White Light Interferometry (SWLI). We report on the use of a variant of SWLI called coherence correlation interferometry (CCI) [1] which is capable of combining sub-nanometre thin film thickness measurements with quantitative three-dimensional metrology and imaging from the same thin film sample area. The technique provides these measurements quickly and. Measurements include root mean square roughness (Sq), average roughness (Sa), maximum peak height (St), step height, groove width and depth, etc
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