Scanning Electron Microscopy (SEM) is the process whereby a tightly focused electron beam is scanned onto the surface to be imaged. As the primary electrons hit the atoms in the surface, a number of secondary electrons are emitted, and collected by the instrument’s detector, which assigns a level of grey accordingly, thereby creating a pixel for a digital image. The machines can routinely image features down to about 10nm, and in some special cases down to several nm in size.SEM is a key tool for process characterisation of surface topography. Most samples fabricated in the cleanroom undergoes at least one round of SEM imaging, in order to assess the quality of the fabrication and its defects. This information is fed into the process optimisation loop until a satisfying sample is produced. The tool is also used to image samples such as fixated cells and failed components.