Super-resolution 3D optical imaging of semiconductors using coherence microscopy

摘要

Recently, several techniques have been proposed for sectioning deep surface relief using the narrow coherence function of white light interference fringes, classified under the general heading of `coherence microscopy'. The maximum value of the coherence function is used as a probe plane at a known height of Z(x,y), which is scanned over the depth of the sample. Nanometric vertical resolution over a range of many tens of microns is attainable by this means. An interesting feature of coherence microscopy is that the high depth discrimination due to the temporal coherence of the illumination beam also leads to super-resolution laterally. This feature is useful in many microelectronics applications where there is a requirement for profiling structures such as grooves, wires and technological layers at a submicron scale laterally and with a nanometric resolution vertically over a depth of many microns. In this work, we present results using coherence microscopy for profiling a variety of micron sized structures with near 0.2 $mu@m lateral resolution over a depth of field of 5 $mu@m. Comparisons are made with SEM and AFM in order to raise some of the issues involved in a correctly interpreting high resolution synthetic images.