Control of Interfacial Properties of Al_2O_3/Ge Gate Stack Structure Using Radical Nitridation Technique

摘要

We have investigated the control of the intertacial properties of Al_2O_3/Ge gate stack structures by the radical nitridation technique. In the Al2O_3/ Ge structures formed by the atomic layer deposition method, the interface state density increases with the deposition temperature due to the decrease in the thickness of the Ge oxide interlayer. On the other hand, the hysteresis width of the capacitance-voltage (C-V) characteristics decreases with increasing deposition temperature, which indicates a decrease in the oxide trap density near the interface. We also investigated the control of the interfacial structure by the radical nitridation of Al_2O_3/Ge to form an intertacial structure after the deposition of a high-/c dielectric layer. The results of X-ray photoelectron spectroscopy reveal that an Al_2O_3/Ge_3 N_4/GeO_2/Ge stack structure is formed after the radical nitridation owing to the minimal oxygen diffusion into the Al_2O_3/Ge interface. Furthermore, the interfacial mixing is suppressed after radical nitridation at less than 300℃. As a result, we can decrease the interface state density of the Al_2O_3/Ge sample after the radical nitridation by more than one order of magnitude compared with that without radical nitridation.