Studies on the structure and electrical characteristics of oxide layers synthesized by reactive ion implantation into tantalum

High purity (99.9%), 0.25 mm thick, tantalum samples were implanted with oxygen reactive ions (16O+) at 100 keV energy at fluence levels ranging from 1 × 1016 to 5 × 1017 ions-cm− 2 to synthesize tantalum oxide layers. The structure of the ion beam synthesized layers was analyzed by FTIR spectroscopy studies. The electrical characteristics were investigated on Al/ Tantalum oxide/Ta (MIM) structures by current–voltage (I–V) and capacitance/dielectric loss-frequency measurements. The FTIR studies show the formation of amorphous tantalum oxide layers of complex structures- tantalum pentaoxide (Ta2O5) and suboxides of tantalum depending on the implantation and post annealing conditions. The I–V studies show ohmic conduction for low voltages and space charge limited conduction (SCLC) at high voltages. The leakage current density of the samples was found to depend on the processing conditions. The electrical resistivity of the tantalum after oxygen implantation is found to increase with ion fluence. The capacitance of the MIM devices fabricated with ion beam synthesized tantalum oxide layers show small variation with frequency. In general, an enhancement in the capacitance and reduction in the dielectric loss were observed upon annealing on samples synthesized with low fluence level indicating gradual transformation into good dielectric layer.