High performance TaYO x-based MIM capacitors

Abstract

TaYO x -based metal–insulator–metal (MIM) capacitors with excellent electrical properties have been fabricated. Ultra-thin TaYO x films in the thickness range of 15–30 nm (EOT ∼ 2.4–4.7 nm) were deposited on Au/SiO 2 (100 nm)/Si (100) structures by rf-magnetron co-sputtering of Ta 2O 5 and Y 2O 3 targets. TaYO x 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/μm 2 at 10 kHz ( ε r ∼ 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 TaYO x -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 TaYO x films. The maximum energy storage density was estimated to be ∼5.69 J/cm 3. Post deposition annealing (PDA) in O 2 ambient at 400 °C has been performed and further improvement in device reliability and electrical performances has been achieved.