Interface quality modulation, band alignment modification and optimization of electrical properties of HfGdO/Ge gate stacks by nitrogen incorporation

Abstract

Effects of nitrogen incorporation on the interfacial chemical bonding states, band alignment, electrical properties and leakage current conduction mechanisms of HfGdO-based metal-oxide-semiconductor (MOS) capacitors has been investigated by UV–Vis transmission spectroscopy, X-ray photoemission spectroscopy (XPS), and electrical measurements. XPS results indicate that incorporation of a moderate amount of nitrogen incorporation into HfGdO gate dielectrics can effectively suppress the formation of low-k GeO2 and Hf(Gd)-Ge-O interfacial layer at the interfacial region. Meanwhile, reduction in band gap and valence band offset and increase in conduction band offset have been observed after nitrogen incorporation. Electrical measurements based on MOS capacitors have shown that MOS capacitor with HfGdON/Ge stacked gate dielectric with N2 flow rate of 3 sccm exhibits small gate leakage current (1.08 × 10−3 A/cm2 at Vg = 1 V), almost disappeared hysteresis, and large dielectric constant (29.2). The involved leakage current conduction mechanisms for MOS capacitor devices with and without nitrogen incorporation also have been discussed in detail.