Hafnium and zirconium silicates for advanced gate dielectrics

Hafnium and zirconium silicate (HfSixOy and ZrSixOy, respectively) gate dielectric films with metal contents ranging from similar to 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 similar to 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 t(ox) of about 18 Angstrom (21 Angstrom) for a 50 Angstrom HfSixOy (50 A ZrSixOy) film deposited directly on a Si substrate. Current-voltage measurements show for the same films a leakage current of less than 2x10(-6) A/cm(2) at 1.0 V bias. Hysteresis in these films is measured to be less than 10 mV, the breakdown field is measured to be E(BD)similar to 10 MV/cm, and the midgap interface state density is estimated to be D(it)similar to 1-5x10(11) 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 epsilon 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 degrees C in direct contact with Si substrates. (C) 2000 American Institute of Physics. [S0021- 8979(00)00701-5].