Profilometry

Stylus profilers are typically used in micro- and nanofabrication for measuring the thickness of films or etch depth. The tip radius is on the order of a few micrometers, so it is not suitable for very fine structures. The simple principle of dragging a tip across a surface while registering vertical tip movement makes the method insensitive to variations in film clarity or refractive index, providing rapid and unambiguous measurements of step height (or roughness) down to the nanometer level.

Optical profilers work via the principle of white light interferometry (WLI), where fringes of equal order indicate positions of equal height. It can easily resolve height differences down to around 1nm and rapidly provide detailed 3D maps at the scale of the optical objective (around 1x1mm for the 10x objective provided with the Nanolab system). It should be noted however, that the measurement is dependent on refractive index of the sample. This becomes an issue when measuring on thin transparent (or partially transparent) films, often used in micro- and nanofabrication. It is therefore very useful to obtain quick 3D maps, but should generally be used in combination with other methods (e.g. SEM, AFM or stylus profilometry).