Fabrication and electrical characteristics of ultrathin (HfO_2)_x(SiO_2)_(1-x) films by surface sol-gel method and reaction-anneal treatment

摘要

Hafnium oxide (HfO_2) films were deposited on Si substrates with a pre-grown oxide layer using hafnium chloride (HfCl_4) source by surface sol-gel process, then ultrathin (HfO_2)_x(SiO_2)_(1-x) films were fabricated due to the reaction of SiO_2 layer with HfO_2 under the appropriate reaction-anneal treatment. The observation of high-resolution transmission electron microscopy indicates that the ultrathin films show amorphous nature. X-ray photoelectron spectroscopy analyses reveal that surface sol-gel derived ultrathin films are Hf-Si-O alloy instead of HfO_2 and pre-grown SiO_2 layer, and the composition was Hf_(0.52)Si_(0.48)O_2 under 500℃ reaction-anneal. The lowest equivalent oxide thickness (EOT) value of 0.9 nm of film annealed at 500℃ has been obtained with small flatband voltage of -0.31 V. The experimental results indicate that a simple and feasible solution route to fabricate (HfO_2)_x(SiO_2)_(1-x) composite films has been developed by means of combination of surface sol-gel and reaction-anneal treatment.