Advances in Environmental Scanning Electron Microscopy: Semiconductor/Thin Fim Applications, Cathodoluminescence (CL) Spectroscopy, and Detector Quantum Efficiency (DQE) Comparisons.

Abstract

Charge Contrast Imaging (CCI) in the environmental scanning electron microscope (ESEM) has rapidly evolved to an important imaging technique for a range of materials. The investigation of the applicability of CCI to the examination of semiconductor and thin film (MCT) samples and devices has been highly successful. Dopant concentration and depth can be differentiated, as has been noted for variable pressure SEM. Quantification of concentration remains difficult due to the complexity of variables controlling CCI but should be achievable in the near future. The extreme sensitivity to surface contaminants previously noted on polished diamond surfaces is also seen on silicon. Monte Carlo modelling of this contrast indicates, for the examined materials, an information depth of a few nanometres for CCI, whilst using 30kV accelerating voltage. The modelling shows that CCI is capable of routine detection of contaminant layers on silicon at the nanometre scale. These results also provide the first data confirming initial suggestions that CCI is derived from the near-surface regions of the sample.CCI examination of mercury cadmium telluride (MCT) devices has also provided images with new detail. This detail is currently being interpreted. Initial examination suggests an influence of the substrate on film growth (figure 1). Unusual corner structures are visible around the mask region.