Isotope Tracing Study of GeO Desorption Mechanism from GeO2/Ge Stack Using 73Ge and 18O

Abstract

GeO desorption from a GeO2/Ge stack is a critical concern in Ge metal oxide semiconductor field effect transistors (MOSFETs). In this contribution, we focus on a uniform-desorption region and unveil the GeO desorption mechanism from a GeO2/Ge stack by 73Ge and 18O isotope tracing in thermal desorption spectroscopy (TDS) analysis, in which the Ge and O diffusion kinetics in GeO2 and the interfacial reaction kinetics have been investigated. Through 73Ge isotope tracing, we have clarified that Ge in the desorbed GeO dominantly comes from the GeO2 surface. Moreover, the self-diffusivity of oxygen was evaluated to be much larger than Ge in GeO2. Furthermore, owing to the difference among GeO desorptions from GeO2/Ge stacks with various substrate orientations, the reaction at the GeO2/Ge interface was attributed to the redox reaction kinetics. On the basis of our experimental findings, we have proposed an oxygen vacancy diffusion model of the GeO desorption mechanism.