Interfacial and electrical properties of radio frequency sputtered ultra-thin TiO2 film for gate oxide applications

The electrical responses of ultra-thin TiO2 films in the form of Al/TiO2/Si capacitors prepared by rf sputtering, have been studied in a wide frequency range as a function of post deposition annealing temperature. Thickness, interfacial and surface roughnesses of the heterostructures were extracted by fitting the specular X-ray reflectivity data. The TiO2 film annealed at 800 A degrees C exhibited negligible hysteresis in the capacitance-voltage curve with the lowest interface trap density of 3.18 x 10(11) cm(-2) eV(-1) extracted using Hill-Coleman method. Minimum equivalent oxide thickness (EOT) of 1.67 nm was obtained for the film annealed at annealed at 800 A degrees C with leakage current density of 7.4 x 10(-4) A/cm(2) at -2 V. Space charge limited current (SCLC) conduction mechanism has been found to be dominant for the film annealed at 400 A degrees C; however for the film annealed at 800 A degrees C, it was found that at lower voltage (< 2.5 V) the conduction mechanism is governed by SCLC with a transition to Fowler-Nordheim tunnelling at voltages higher than 2.5 V.