Energy band profile of hafnium silicates estimated by X-ray photoelectron spectroscopy

Amorphous hafnium silicate films with several composition ratios were deposited on Si substrates by plasma-enhanced chemical vapor deposition, and their energy band profiles were studied by X-ray photoelectron spectroscopy. The band gap energy estimated from the energy loss spectrum of O 1s electrons decreases monotonically and then approaches a constant value with an increase in hafnium content. The valence band offset and the conduction band offset were estimated using the sample sandwiched between an evaporated Au electrode and the Si substrate. Although the two offsets decrease until they become almost constant with an increase in hafnium content at both silicate/Si and silicate/ Au interfaces, they hold values higher than that necessary for a high-k dielectric material to maintain a good insulating performance for all the deposited silicates.