Condensation Mechanism for the Formation of Relaxed SiGe Layer Grown-on-Insulator

Abstract

ABSTRACTThe condensation method to grow a strained SiGe layer-on-insulator (ε-SGOI) has attracted interests for the application of high speed complementary metal–oxide–semiconductor field-effect transistors (CMOSFETs) because of high quality properties and effective process cost. Although many reports presented its superiority in a device performance to bonding and dislocation sink technologies, the mechanism by which the condensation method produces ε-SGOI has also not been clearly explained and the surface properties have not been evaluated. Thus, we investigated condensation mechanism in detail by characterizing a surface property and Ge profile in SiGe layer. For the experiment, first, a SiGe layer on silicon-on-insulator layer was epitaxally grown at 550 °C, and three different oxidation thicknesses were grown at 950 °C, i.e., 40, 60, 90 nm. From our investigation results, we found that there are three steps in producing ε-SGOI. For the first step, by the 40-nm-thick oxidation, a diffusion of Ge atoms in SiGe layer into Si layer-on-insulator was generated and Ge atoms were segregated into only surface oxide. It was observed that Ge profile of SiGe layer was shown a less graded profile. And, in the second step with 60-nm-thick oxidation, Ge atoms in SiGe layer into Si layer-on-insulator was diffused further than a first step did and Ge atoms were segregated into surface oxide. It was observed that Si layer was shown a fully graded profile. Lastly, in the third step with 90-nm-thick oxidation, the diffusion of Ge atoms in SiGe layer into Si layer-on-insulator was finished completely and Ge atoms were segregated into both surface and buried oxides. It was confirm that Ge profile of SiGe layer was shown a Gaussian profile rather than a graded profile, and dislocation sink occurred. Therefore, our talk will focus on the explanation for the mechanism by which condensation method produces ε-SGOI via characterizing a surface property, SiGe thickness, a remained Si thickness on insulator, and Ge concentration in SiGe layer.