Hafnium and zirconium silicates for advanced gate dielectrics Available to Purchase

Hafnium and zirconium silicate $(HfSixOy$ and $ZrSixOy,$ respectively) gate dielectric films with metal contents ranging from ∼3 to 30 at. % Hf, or 2 to 27 at. % Zr (±1 at. % for Hf and Zr, respectively, within a given film), have been investigated, and films with ∼2–8 at. % Hf or Zr exhibit excellent electrical properties and high thermal stability in direct contact with Si. Capacitance–voltage measurements show an equivalent oxide thickness $tox$ of about 18 Å (21 Å) for a 50 Å $HfSixOy$ (50 Å $ZrSixOy)$ film deposited directly on a Si substrate. Current–voltage measurements show for the same films a leakage current of less than $2×10−6 A/cm2$ at 1.0 V bias. Hysteresis in these films is measured to be less than 10 mV, the breakdown field is measured to be $EBD∼10 MV/cm,$ and the midgap interface state density is estimated to be $Dit∼1–5×1011 cm−2 eV−1.$ Au electrodes produce excellent electrical properties, while Al electrodes produce very good electrical results, but also react with the silicates, creating a lower ε layer at the metal interface. Transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy indicate that the dielectric films are amorphous silicates, rather than crystalline or phase-separated silicide and oxide structures. TEM shows that these films remain amorphous and stable up to at least 1050 °C in direct contact with Si substrates.