Fabrication and electrical characterization of Ge/GeOx/Al2O3/HfO2 MOS capacitors

Abstract: Continuous scaling of complementary metal oxide semiconductor (CMOS) devices has led to constant increase in device performance. However, as scaling becomes more difficult with every technological node, alternative channel materials that could replace silicon (Si) are being investigated [1]. Germanium (Ge) is an attractive material because of its four times higher hole mobility and twice higher electron mobility compared to silicon [2]. Nevertheless, Ge suffers from surface passivation issues that need further investigation. A modification of oxidation through a barrier layer method proposed by Takagi group[3] has been employed for the fabrication of MOS capacitors. Ozone oxidation has been performed in-situ in atomic layer deposition (ALD) chamber using Al2O3 layer as a barrier. Combinations of barrier thickness and ozone generator power have been investigated together with the influence of the oxidation time. Electrical characterization has revealed that the Ge/oxide interface is improved while employing high ozone generator power oxidation through a thin (~0.47 nm) barrier as well as prolonged oxidation times up to 15 min. Interface state density has been suppressed to lowto mid 1012 cm-2eV-1.