Structural, optical and electrical properties of DC reactive magnetron sputtered (Ta2O5)1−x(TiO2)x thin films

Abstract

Tantalum pentoxide (Ta2O5) is promising as gate dielectric for the next generation memory devices. Titanium doped Ta2O5 thin films leads to reduction in the leakage current density of the device. Thin films of (Ta2O5)1−x(TiO2)x (x =0 to 0.18) were deposited on quartz and p-Si (100) substrates by DC reactive magnetron sputtering. X-ray diffraction studies revealed the presence of tantalum oxide, and the size of crystallite in the (Ta2O5)1−x(TiO2)x films was decreased with the increase of composition x. The surface stoichiometry of (Ta2O5)1−x(TiO2)x thin films (x =0.00 to 0.18) has been studied by X-ray photoelectron spectroscopy. The binding energies for various core level electrons of the different elements present in these films have been determined. FTIR study confirmed the presence of titanium oxide in the tantalum oxide films. The Optical band gap of the (Ta2O5)1−x(TiO2)x films formed on quartz substrate decreased from 4.50 to 4.32eV with the increase in the content of titanium. An Al/(Ta2O5)1−x(TiO2)x/p-Si metal–insulator–semiconductor (MIS) device was fabricated whose leakage current density decreased from 2.10×10−5 to 3.6×10−8A/cm2 with the increase of titanium, i.e., x ≤ 0.15. The Schottky barrier height values were extracted from current-voltage (I-V) characteristics of Al/(Ta2O5)1−x(TiO2)x/p-Si (MIS) structure and are found to be ranging from 0.66eV to 0.82eV for different dopant compositions. The capacitance was measured for pure Ta2O5 films at 1MHz and was found to be 4.79×10−9F. Also, it was noticed that the capacitance was found to be increased in (Ta2O5)1−x(TiO2)x films to 7.10×10−9F for the dopant composition x =0.15.