Abstract
TaYOx-based metal-insulator-metal (MIM) capacitors with excellent electrical properties have been fabricated. Ultra-thin TaYOx films in the thickness range of 15-30 nm (EOT similar to 2.4-4.7 nm) were deposited on Au/SiO2 (100 nm)/Si (100) structures by rf-magnetron co-sputtering of Ta2O5 and Y2O3 targets. TaYOx layers were characterized by X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) to examine the composition and crystallinity. An atomic percentage of Ta:Y = 58.32:41.67 was confirmed from the EDX analysis while XRD revealed an amorphous phase (up to 500 degrees C) during rapid thermal annealing. Besides, a high capacitance density of similar to 3.7-5.4 fF/mu m(2) at 10 kHz (epsilon(r) similar to 21), a low value of VCC (voltage coefficients of capacitance, alpha and beta) have been achieved. Also, a highly stable temperature coefficient of capacitance, TCC has been obtained. Capacitance degradation phenomena in TaYOx-based MIM capacitors under constant current stressing (CCS at 20 nA) have been studied. It is observed that degradation depends strongly on the dielectric thickness and a dielectric breakdown voltage of 3-5 MV/cm was found for TaYOx films. The maximum energy storage density was estimated to be similar to 5.69 J/cm(3). Post deposition annealing (PDA) in O-2 ambient at 400 degrees C has been performed and further improvement in device reliability and electrical performances has been achieved. (C) 2009 Elsevier B.V. All rights reserved.