Abstract
The aggressive scaling of gate length and gate oxide thickness in CMOS transistors for high performance and circuit density aggravates the problems of gate leakage current, standby power consumption and gate oxide reliability. High-dielectric-constant films can potentially be used to replace SiO2 as gate dielectrics at sub-100 nm technology nodes. In this thesis, MOS capacitors and MOSFETs incorporating ZrO2, HfO2 or La2O3 were fabricated and investigated. The conduction mechanisms of these high-k films are studied. The dominant conduction mechanisms of the Al/ZrO2/p-Si structure at high temperatures are Poole-Frenkel emission, modified Schottky emission and Schottky emission in low, medium and high electric fields, respectively. The Al/ZrO2 barrier height, the trap level, the electronic mobility, and the mean-free-path are determined to be 0.92 eV, 1.1 eV, 12-13 cm2/V-s, and 16.2-17.4 nm, respectively. The conduction mechanism of the Al/HfO2/p-Si structure is Schottky emission at high temperatures (513~578 K). The Al/HfO2 barrier height is about 1.02 eV and the effective barrier height between the composite HfO2/interfacial layer (IL) and Si is about 0.94 eV. The metal/oxide/IL/Si energy band diagrams associated with ZrO2 and HfO2 are proposed. The dominant conduction mechanism of the Al/La2O3/p-Si MOS capacitors is space-charge-limited current from 300 K to 465 K. The activation energy, electronic mobility in La2O3, trap density, dielectric relaxation time and density of states in the conduction band were obtained. The electrical properties of the HfO2/Si interface were also studied by using the gated-diode method. The generation current Igen, interface-trapped charge density Nit, surface recombination velocity so, minority carrier lifetime in the field-induced depletion region tFIJ, and effective capture cross section ss of the HfO2 gated diode were obtained.