Surface particle detection for the 0.07 μm generation and beyond

The detection of surface particles has become important in contamination control over the years. However, the minimum particle size required to be detect-ed has been becoming smaller as IC geometries shrink. Current visible-light detection systems can detect particles down to around 60 nm in polystyrene-latex-equivalent size and so should be adequate for geometries down to around 0.18 mu m, but a quick glance at the National Technology Roadmap for Semiconductors shows that geometries are expected to become as small as 0.07 mu dm in a little over ten years, requiring the ability to detect particles around 20 nm in diameter. This is beyond the capability of current visible-light scanners, so the Semiconductor Research Corporation has recently commissioned our group to conduct research into the limits of optical defect detection and potential of alternative detection technologies. This research centers on short-wavelength optical systems and scanned electron-beam systems as the most likely candidate technologies for high-speed nanoparticle detection. In this paper we develop a model for the analysis of the performance of hypothetical short-wavelength surface inspection systems and examine the manifold difficulties involved with using those wavelengths. The properties of scattering in the transitional region between the UV and X-ray regimes are also examined.