High performance TaYOx-based MIM capacitors

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 ∼ 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 °C) during rapid thermal annealing. Besides, a high capacitance density of ∼3.7–5.4 fF/μm2 at 10 kHz (εr ∼ 21), a low value of VCC (voltage coefficients of capacitance, α and β) 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 ∼5.69 J/cm3. Post deposition annealing (PDA) in O2 ambient at 400 °C has been performed and further improvement in device reliability and electrical performances has been achieved.