Structural and electrical quality of the high-k dielectric Y2O3 on Si (001): Dependence on growth parameters

Thin films of the high-k dielectric Y2O3 are grown on Si (001) substrates by e-beam evaporation in ultrahigh vacuum (UHV), aiming at correlating structural quality with electrical behavior. Films grown at high temperature of ∼450 °C have reproducibly good epitaxial crystalline quality although they exhibit poor electrical behavior. The best electrical properties are measured in films grown at a low to intermediate temperature range around 200 °C, although these films have inferior structural quality, exhibiting texturing or polycrystallinity. A possible explanation for the observed low leakage current (∼10−6 A/cm2 at +1 V) in these films is the presence of a thick (15–20 Å) and uniform interfacial amorphous layer typically formed during growth because of the oxidation of the silicon substrate. This layer is significantly reduced in samples grown at high temperature, while it almost disappears after in situ annealing to 650 °C in UHV, producing sharp interfaces and very good, stoichiometric crystalline Y2O3 epitaxial layers.