High-k dielectric oxides obtained by PLD as solution for gates dielectric in MOS devices

Abstract

The aim of this work was to find the suitable high-k dielectric compound to be used as gate dielectric in MOS devices. Thin films of zirconia (ZrO 2), zirconium silicate (ZrSi x O y ), hafnia (HfO 2) and hafnium silicate (HfSi x O y ) with thickness in the nanometer range have been obtained by pulsed laser deposition (PLD), assisted or not by radio-frequency discharge. For thin films of ZrO 2 and HfO 2, high purity targets of metallic Zr and Hf, respectively, have been ablated in oxygen reactive atmosphere. Alternative ablation of Zr and Si, respectively, Hf and Si targets in oxygen reactive atmosphere was used to obtain thin films of ZrSi x O y and HfSi x O y . Laser fluence (3–6 J/cm 2), oxygen pressure (10 −3 to 10 −1 mbar) and laser wavelength (355 and 532 nm) were varied during deposition. The thin films were investigated using X-ray diffraction, atomic force microscopy (AFM) and secondary ion mass spectroscopy, electrical characterization. Low leakage current values (in the range of 10 −3 to 10 −7 A/cm 2) were measured for all thin films deposited by radio-frequency beam assisted pulsed laser deposition (RF-PLD). Scanning electron microscopy (SEM) and atomic force microscopy investigations showed surface roughness of the order of a few angstroms, for films deposited by RF-PLD.