Ion, sputter and useful ion yields for accurate quantification of Si1-xGex (0 < x < 1) using ultra low energy O2+ SIMS

It has been previously demonstrated that accurate measurement of x in the Si1-xGex (x = 0.3) alloy can be achieved using a variety of O-2(+) SIMS conditions. With SiGe device technology still developing to exploit its full potential, the useful matrices now extend from 0 <= x <= 1. Using the previously established conditions, we have found that roughening of the material occurs when x approaches 1. To overcome this limitation we have developed a set of conditions that enables the whole Si1-xGex (0 <= x <= 1) range to be quantified. This is achieved by using an O-2(+) primary beam energy of <= 500 eV at near-normal incidence. Here, we present a comprehensive study of the measured (Si and Ge) ion, useful ion and sputter yield behavior as a function of matrix composition and incident beam energy (250 eV - 1 keV), from which these new conditions have been established. For the extended Si1-xGex (0 <= x <= 1) range and primary beam energies used here, the measured Si and Ge ion yields were found to be well described by quartic, cubic or quadratic dependences as a function of x. The useful ion yields and sputter yields all showed moderate matrix effects, with the former decreasing monotonically for increasing x except in the case of Ge at 250 eV. Here, the useful Ge ion yield was found to be invariant with x while its measured ion yield (for all x) was observed to be proportional to its sputter yield. Copyright (C) 2010 John Wiley & Sons, Ltd.