Electrical properties of ultrathin HfO{sub}2 gate dielectrics on partially strain compensated SiGeC/Si heterostructures

摘要

Ultrathin HfO{sub}2 gate dielectrics have been deposited on strained Si{sub}0.69Ge{sub}0.3C{sub}0.01 layers by rf magnetron sputtering. The polycrystalline HfO{sub}2 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 Si{sub}0.69Ge{sub}0.3C{sub}0.01 show an equivalent oxide thickness (EOT) of 2.9 nm, with a low leakage current density of ～4.5 × 10{sup}(-7) A/cm{sup}2 at a gate voltage of -1.0 V. The fixed oxide charge and interface state densities are calculated to be 1.9 × 10{sup}12 cm{sup}(-1) and 3.3 × 10{sup}11 cm{sup}(-2)eV{sup}(-1), respectively. The temperature dependent gate leakage characteristics has been studied to establish the current transport mechanism in high-k HfO{sub}2 gate dielectric to be Poole-Frenkel one. An improvement in electrical properties of HfO{sub}2 gate dielectrics has been observed after post deposition annealing in O{sub}2 and N{sub}2 environments.