Impact of nitrogen incorporation on the interface between Ge and La2O3 or Y2O3 gate dielectric : a study on the formation of germanate

摘要

La2O3 and Y2O3 are used as gate dielectric in Ge MOS capacitors, and their electrical and interfacial properties are comparatively studied. Due to the much higher reactivity of La2O3 with Ge than Y2O3, thicker germanate interlayer is formed, leading to better interface quality for the former. Moreover, it is found that N incorporation in the oxides reduces the formation of both germanate and GeOx, with much more obvious effect for La2O3 and thus the best interface quality (a low interface-state density of 4.96 × 1011 cm-2eV-1), which gives promising electrical properties: large equivalent dielectric constant (18.8), small flat-band shift (0.37 V), low gate leakage current (2.89 × 10-4 A/cm2 at Vg = Vfb + 1 V), and high reliability under electrical stress.