Quantification of Ge in Si_(1-x)Ge_x by using low-energy Cs~+ and O_2 ~+ ion beams (Conference Paper)

摘要

Several studies have been reported on the quantification of Ge in Si _(1-x)Ge_x using SIMS with oxygen or cesium primary ions. Most of them were limited to lower Ge concentrations. In this paper, we discussed procedures to quantify Ge content in Si_(1-x)Ge_x with x ranging from 0.11 to 0.70 by using low-energy Cs~+ and O _2 ~+ primary beams. The results showed that at impact energy of 250 eV, the Ge secondary ion yield changed dramatically against the SiGe matrix composition with a Cs~+ primary beam, whereas the change was minimal with an O_2 ~+ primary beam. As a result, quantification by using the reference signal inside Si substrate became difficult as no linear correlation exists between the Ge intensity and the Ge concentration in the case of Cs~+ primary ions. However, the correlation between the ratios of secondary intensities I(Ge)/I(Si) within the SiGe layers and the composition ratio [Ge]/[Si] is monotonic (although nonlinear). Hence, quantification based on the ratios of the secondary ion intensities versus the ratios of the corresponding contents worked for both Cs~+ and O_2 ~+ primary beams to quantify the Ge content of an unknown SiGe sample. In addition to this, we reported the angular (incidence angles between 0° and 70°) dependence of the sputter yield of SiGe as a function of Cs+ primary ion energy (150-500 eV).