Remote plasma-deposited GeO_2 with quartz-like Ge- and O-local bonding: Band-edge state and O-vacancy comparisons with SiO_2

摘要

X-ray absorption spectroscopy (XAS) and many-electron theory are combined to describe symmetries and degeneracies for intrinsic bonding defects in remote plasma-deposited (rpd-) non-crystalline (nc-), rpd-nc-GeO_2 and rpd-nc-SiO_2, hereafter simply GeO_2 and SiO_2. GeO_2 is emerging as an alternative gate dielectric for nano-CMOS devices. High resolution O-vacancy spectral features in 0 K pre-edge spectra for SiO_2 have been assigned to multiplet transitions and negative ion states based on an extended d2 equivalent model, including both weaker singlet and as well the stronger triplet transitions discussed in previous publications. This has revealed predominantly mid-gap Ge and Si singlet and triplet bonding arrangements for the electrons in O-vacancy sites. These have been examined as a function of post deposition rapid thermal annealing in Ar ambients for GeO_2 deposited at 300 ℃ on both Si and Ge substrates, identifying different post-deposition thermal budget processing windows for low defect density GeO_2 on Si and Ge substrates. For ultra thin nitrided SiO_x, x < 2 interfacial layers on Si, this is at least 700 ℃, but on Ge, independent of surface processing it less than 600 ℃