Effects of Atomic Layer Deposition-Al2O3 Interface Layers on Interfacial Properties of Ge Metal–Oxide–Semiconductor Capacitors

Abstract

We have investigated the interfacial control effects of the atomic layer deposition (ALD)-Al2O3 on the crystalline and electronic characteristics of LaAlO3/Ge metal–oxide–semiconductor (MOS) structures. X-ray photoelectron spectroscopic analysis revealed that Al2O3/Ge interfaces are much more stable than LaAlO3/Ge and La2O3/Ge interfaces for the formation of Ge oxides owing to the interfacial reaction. For the LaAlO3/ALD-Al2O3/Ge structure, Al2O3 interfacial layers with thicknesses less than 1 nm effectively suppress the interfacial reaction between LaAlO3 and Ge. The thickness of Ge oxides formed at the ALD-Al2O3/Ge interface decreases with increasing Al2O3 thickness and the stack structure is thermally stable against postdeposition annealing at 600 °C. These results indicate that interfacial reaction mainly arises during the sputtering-LaAlO3 deposition, not the ALD-Al2O3 deposition. On the other hand, capacitance equivalent oxide thickness decreases with increasing interfacial ALD-Al2O3 thickness, because the formation of Ge oxides at the interface is effectively suppressed by ALD-Al2O3 interfacial layers. It can be concluded that ALD-Al2O3 is promising as an interfacial control layer between Ge substrates and high-k dielectrics.