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

Abstract

AbstractIt has been previously demonstrated that accurate measurement of x in the Si1−xGex (x ≤ 0.3) alloy can be achieved using a variety of O2+ 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 O2+ 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 © 2010 John Wiley & Sons, Ltd.