Photoemission study on electrical dipole at SiO2/Si and HfO2/SiO2 interfaces

Electrical dipole at SiO2/Si and HfO2/SiO2 interfaces have been investigated by X-ray photoelectron spectroscopy (XPS) under monochromatized Al K alpha radiation. From the analysis of the cut-off energy for secondary photoelectrons measured at each thinning step of a dielectric layer by wet-chemical etching, an abrupt potential change caused by electrical dipole at SiO2/Si and HfO2/SiO2 interfaces has been clearly detected. Al-gate MOS capacitors with thermally-grown SiO2 and a HfO2/SiO2 dielectric stack were fabricated to evaluate the Al work function from the flat band voltage shift of capacitance-voltage (C-V) characteristics. Comparing the results of XPS and C-V measurements, we have verified that electrical dipole formed at the interface can be directly measured by photoemission measurements. (C) 2017 The Japan Society of Applied Physics