The relation between germanium monoxide (GeO) desorption and either improvement or deterioration in electrical characteristics of metalGeO(2)Ge capacitors fabricated by thermal oxidation has been investigated. In the metalGeO(2)Ge stack, two processes of GeO desorption at different sites and at different temperatures were observed by thermal desorption spectroscopy measurements. The electrical characteristics of as-oxidized metalGeO(2)Ge capacitors shows a large flat-band voltage shift and minority carrier generation due to the GeO desorption from the GeO(2)Ge interface during oxidation of Ge substrates. On the other hand, the electrical properties were drastically improved by a postmetallization annealing at low temperature resulting in a metal catalyzed GeO desorption from the top interface.
The relations between physical structural transformations and improvement of electrical properties of metal/GeO 2 /Ge systems using low temperature oxidation and the post metal deposition annealing (PDA) have been investigated. In metal/GeO 2 /Ge systems, we found that the electrical properties were drastically improved by the oxidation and the PDA. The oxidation at low temperature achieves no C-V hysteresis because of suppression of GeO desorption. on the other hand, according to results of X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS), the improvement mechanism of electrical properties of metal/GeO 2 /Ge structures after the PDA was clearly shown as follows. Once the metals were deposited on the GeO 2 , GeO x layer was formed at the surface region of the GeO 2 due to reduction of the oxide by the metals. The sub-oxide layer at the interface causes a large negative flat-band voltage (V FB ) shift on the capacitance-voltage (C-V) characteristics of the metal/GeO 2 /Ge structures. Then, during the PDA process at low temperature, the sub-oxide layer is disappeared with desorbing as germanium monoxide (GeO) gas, and the V FB shifts of the metal/GeO 2 /Ge systems were drastically improved and also their accumulation capacitances were increased because of disappearance of the sub-oxide layer.
Impacts of structural transformations of top and bottom interface of metal/GeO 2 /Ge structure on electrical properties were investigated. The GeO 2 /Ge interface that was formed by low temperature oxidation achieved negligible hysteresis because of suppressing GeO volatilization. On the other hand, the metal/GeO 2 interface with post metal deposition annealing attained disappearance of V FB shift. XPS and TDS measurements show that GeO x at the interface of the as-deposited metal/GeO 2 vanished after annealing. It suggests that the improvement of the V FB shift was achieved by volatilization of GeO x including defects at the metal/GeO 2 interface.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.