Synthesis of High Dielectric Constant Titanium Oxide Thin Films by Metalorganic Decomposition

Abstract

Titanium-containing alkoxide (Ti[i-OCH(CH3)2]4) dissolved in 2-methoxyethanol was directly deposited onto silicon by the metalorganic decomposition (MOD) technique. Titanium oxide (TiO2) thin films are formed uniformly on Si after high-temperature annealing. Raman and X-ray diffraction measurements indicate that the structure changes completely from anatase to rutile phase at an annealing temperature of 700°C. During the crystallization, however, the reaction starts at the TiO2/Si interface, resulting in the formation of interfacial SiO2 layer with a thickness of 2.6 nm. In contrast, the TiO2 thickness was fairly constant. The capacitance-voltage characteristics revealed that with annealing temperature, the dielectric constant increases to a maximum (εmax=48) at 700°C. However, the dielectric constant decreases again above 700°C due to the occurrence of interfacial SiO2 growth. For the well crystallized TiO2 films, the leakage current decreases to 7×10-8 A/cm2 at 2 MV/cm and the maximum breakdown field is 3.3 MV/cm. The TiO2 thin films formed by MOD are expected to act as a suitable dielectric in place of conventional thin SiO2 for future integrated circuits.