Growth and characteristics of La_2O_3 gate dielectric prepared by low pressure metalorganic chemical vapor deposition

摘要

Ultrathin La_2O_3 gate dielectric films were prepared on Si substrate using La(tmhd)_3 source by low pressure metalorganic chemical vapor deposition (MOCVD). The growth processing, interfacial structure and electrical properties have been investigated by various techniques. The ultrathin films deposited at 600 show amorphous structure with smaller roughness of ～0.2 nm and larger band gap of E_g = 6.18 eV. This is attributed to the interfacial layer existence of compositionally graded La-Si-O silicate. Due to the chemical instability of La_2O_3 films in ambient, it can absorb vapor and carbon dioxide, which leads to the deterioration of electrical properties. By introducing Al_2O_3 capping layer, the reliable value of equivalent oxide thickness around 1.8 nm of La_2O_3/Si has been achieved.