Abstract: The interfacial and electrical characteristics of Ge metal-oxide-semiconductor (MOS) devices with a dual passivation layer of ZrON/GeON formed by NH₃- or N₂-plasma treatment are investigated. The experimental results show that the NH₃-plasma treated sample exhibits significantly improved interfacial and electrical properties as compared to the samples with N₂-plasma treatment and no treatment: a lower interface-state density at the midgap (1.64 × 10¹¹ cm^-2·eV^-1) and gate leakage current (9.32 × 10^-5 A/cm² at V_fb+ 1 V), a small capacitance equivalent thickness (1.11 nm) and a high k value (32). X-ray photoelectron spectroscopy is used to analyze the involved mechanisms. It is indicated that more GeON and less GeO_x (x <2) are formed on the Ge surface during NH₃-plasma treatment than the N₂-plasma treatment, resulting in a high-quality high-k/Ge interface, because H atoms and NH radicals in NH₃-plasma can enhance volatilization of the unstable low-k GeO_x, creating high-quality GeON passivation layer. Moreover, more nitrogen incorporation in ZrON/GeON induced by NH₃-plasma treatment can build a stronger N barrier and thus more effectively inhibit in-diffusion of O and Ti from high-k gate dielectric and out-diffusion of Ge.

Key words: Ge MOS, NH₃ plasma, interface properties, ZrON/GeON dual passivation layer