THE USE OF ADVANCED 3D SURFACE METROLOGY FOR THE CHARACTERISATION OF MICRO AND NANO SURFACE STRUCTURES

Over recent years the discipline of surface metrology has advanced greatly both in terms of instrumentation and in terms of techniques for surface characterisation. Recent developments in White Light Interferometer (WLI) instrumentation and in measurement software (particularly the so-called coherence correlation algorithm) for this technique has increased the vertical (i.e. height) resolution of these instruments to give a capability of 0.01 nm (i.e. 0.1 Angstrom), which makes it a practical tool for assessing the quality of micro and nanoscale surfaces. Whilst both WLI and AFM techniques have allowed visualisation of the 3D surface texture of surfaces at the micro and nanometer scale, a clear advantage of interferometry is that it is contactless, fast and can cover large areas, whereas the AFM technique, although it has a better measurement resolution tends not to suit the measurement of large areas and low spatial frequency components. A common flaw in the use of both of these instrument types is that despite the ?richness? of the data collected it is usually only the Ra, Rq or Rt values of the surface texture that are quoted. True surface areal texture information cannot be described by such parameters Consequently these simple amplitude based roughness parameters are inadequate for describing anything more than very simple surface-structures and as a result differing textures can often yield similar roughness values. This paper outlines the recent advances in 3D surface characterisation and the use of white light interferometry.