Electrical properties of ultrathin HfO2 gate dielectrics on partially strain compensated SiGeC/Si heterostructures

Ultrathin HfO2 gate dielectrics have been deposited on strained Si0.69Ge0.3C0.01 layers by rf magnetron sputtering. The polycrystalline HfO2 film with a physical thickness of ∼6.5 nm and an amorphous interfacial layer with a physical thickness of ∼2.5 nm have been observed by high resolution transmission electron microscopy (HRTEM). The electrical properties have been studied using metal-oxide-semiconductor (MOS) structures. The fabricated MOS capacitors on Si0.69 Ge0.3C0.01 show an equivalent oxide thickness (EOT) of 2.9 nm, with a low leakage current density of ∼4.5 × 10 − 7 A/cm2 at a gate voltage of –1.0 V. The fixed oxide charge and interface state densities are calculated to be 1.9 × 1012 cm− 2 and 3.3 × 10 11 cm− 2eV−1, respectively. The temperature dependent gate leakage characteristics has been studied to establish the current transport mechanism in high-k HfO2 gate dielectric to be Poole–Frenkel one. An improvement in electrical properties of HfO2 gate dielectrics has been observed after post deposition annealing in O2 and N2 environments.