Conduction mechanisms and an evidence for phonon-assisted conduction process in thin high-k HfxTiySizO films

Electrical behavior of high-k HfxTiySizO layers with different Hf:Ti ratios in the film have been investigated. The films are prepared by MOCVD using novel single-source precursors chemistry. Oxide and interface charges, leakage currents and conduction mechanisms are found to be a strong function of the film composition. The films with lower Hf content show lower level of oxide and interface charges and higher dielectric constant whereas those with higher Hf content have better leakage current properties. It is established that in the films with lower Hf content the conduction is governed by a phonon-assisted process. The change of the conduction mechanism from Poole-Frenkel emission to phonon-assisted tunneling is assigned to possible structural changes which take place when changing the composition of the films.