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A novel approach for the sensitive detection and unequivocal identification of trace amounts of copper introduced into p-type silicon and its oxide during high-temperature processing is discussed. Noncontact surface voltage and surface photovoltage ͑SPV͒ measurements are employed to determine the impact of copper impurities on distinct bulk silicon, interface, and oxide properties. For oxidized p-type Si, the characteristic copper signature comprises an increased oxide charge and a pronounced decrease in the minority carrier recombination lifetime upon optically induced formation of copper precipitates in the silicon bulk. During illumination, out-diffusion of copper to the silicon-oxide interface occurs simultaneously with precipitation and results in an increased interface trap density. For a complete overview on the distribution of the copper impurity on the various defect states before and after optical activation, the recombination lifetime, the interface trap density, and the total oxide charge have to be monitored.

Copper (Cu) adsorption from diluted hydrofluoric acid (DHF) onto bare silicon surfaces strongly depends on the substrate doping. On highly phosphorus-doped silicon, the adsorption rate is up to three orders of magnitude larger than on moderately doped silicon. This may open a gap between Cu-induced semiconductor device degradation and the detection of Cu contaminations in DHF by minority carrier lifetime measurements. Using dedicated copper monitor wafers where a highly phosphorus-doped backsurface ensures strong Cu adsorption while a moderately doped frontsurface enables minority carrier lifetime measurements, we are able to improve the limit of detection for Cu in DHF by two orders of magnitude.

By using the tip of a scanning tunneling microscope (STM) as a local source for electrons (or holes) light emission can be excited from metals, semiconductors and molecules. Using this technique, it is possible to combine the high spatial resolution of STM with optical techniques. We review results obtained using a variety of modes of measurements including fluorescence spectroscopy, isochromat spectroscopy and simultaneous mapping of photon emission and surface topography. In spatial maps of the photon emission, clear contrasts are observed with lateral resolutions below 1 nm which are related to the geometric and electronic structure of the sample and the tip. In particular, recent results on atomic resolution of Au(l 10) are discussed to highlight the important role of the electromagnetic interaction of the tip and the sample for the observed photon emission.

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