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2005
Conference Paper
Titel
Thin Hf(x)Ti(y)Si(z)O films with varying Hf to Ti contents as candidates for high-k dielectrics
Abstract
The physical and electrical properties of high-k HfxTi ySizOq layers with different Hf:Ti ratios have been investigated. The films are prepared by MOCVD using two single-source precursors. Oxide and interface charges, leakage currents, and conduction mechanisms are found to be a strong function of the film composition. The films with low Hf content show low levels of oxide and interface charges and high dielectric constants whereas those with high 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, i.e., it is defined rather by the intrinsic properties of the layer than by its defect structure. The observed bias polarity asymmetry of the current conduction is suggested to be due to phase separation and formation of TiO2, HfO2, and SiO2 islands in the films. The degree of phase separation depends strongly on film composition.