Effects of interfacial NH3/N2O-plasma treatment on the structural and electrical properties of ultra-thin HfO2 gate dielectrics on p-Si substrates

The interfacial characteristics of high-κ HfO2 on NH3- and N2O-plasma treated p-Si substrates have been investigated using high-resolution transmission electron microscopy (HRTEM), time-of-flight secondary ion mass spectroscopy (ToF-SIMS), and auger electron spectroscopy (AES). NH3- and N2O-plasma treated films show the formation of a nitrogen-rich Hf-silicate interfacial layer between the deposited HfO2 and Si substrates. The electrical characteristics have been studied using metal-oxide-semiconductor (MOS) structures. Interfacial nitrogen increases the capacitances by ∼33% for NH3 and ∼47% for N2O-treated Si as compared to the untreated surface. A dielectric constant of ∼26 for HfO2 film, ∼6.0 for Hf-silicate, ∼9.0 for NH3- and ∼11.0 for N2O-treated interfacial layers have been calculated from the accumulation capacitances of the MOS capacitors. The relatively higher dielectric constant, lower capacitance equivalent thickness (CET), lower leakage current and higher breakdown voltage for N2O-plasma treated film makes it attractive for scaled Si MOSFET applications.