Length calibration standards for nano-manufacturing

The physical dimensions of nanoscale objects are an important indicator of their functionality. However, measuring feature size from a SEM image is difficult not only because of fundamental considerations, such as the nature of beam interactions and the information transfer properties of the microscope, but because the magnification of the SEM image from which a measurement will be made is completely uncalibrated and additionally is subject to local distortions and variations. Nano-gauges fabricated by electron beam lithography - one or two dimensional structures on the size scale of the objects of interest - provide a local length standards within the image field from which the relative size of features can be accurately determined. In order to provide an absolute measurement of size the dimensions of the nano-gauge structure must themselves be calibrated against some primary standard. Because there are no convenient standards of appropriate scale available we propose that this can be done using a moire fringe technique to bridge the gap between the nanoscale and common length standards such as ruled diffraction gratings.