Effects of deposition temperature on the conduction mechanisms and reliability of radio frequency sputtered TiO2 thin films

The electrical conduction mechanisms and reliability characteristics of rf-sputtered TiO2 thin films deposited at different temperatures have been systematically investigated. Analytical results revealed that adequate sputtering temperature not only provided a superior polycrystallized TiO2 film as well as a less leakage current, but also reduced the oxygen vacancy, resulting in the Frenkel-Poole (FP) conduction mechanism of low-temperature (400-500degreesC) sputtered samples transiting to the Schottky emission (SE) process of medium-temperature (600-700degreesC) sputtered samples. However, for samples sputtered by higher temperature (750-800degreesC), the evident oxygen deficiency due to the deteriorated crystallinity and significant Si diffusion contamination in the TiO2 films were asserted to be the two main causes leading to the SE conduction process in medium-temperature (600-700degreesC) sputtered samples transiting to the FP conduction mechanism in high-temperature (750-800degreesC) sputtered samples again. Besides, the excellent agreement between the E model and the time-dependent-dielectric-breakdown data suggested strongly that the exhibited best long-term reliability of metal-oxide-semiconductor capacitors with TiO2 gate oxide sputtered at 700degreesC was due to the possession of superior crystallinity and less interface hole trap density at the junction of TiO2/Si, resulting in a higher thermal activation energy E-a of 0.709 eV at 5 MV/cm, reducing the breakdown occurrence. (C) 2002 American Vacuum Society.