Preparation and characterization of TaAlOx high-κ dielectric for metal–insulator–metal capacitor applications

Metal–insulator–metal (MIM) capacitors with excellent electrical properties have been fabricated using high-κ TaAlOx-based dielectrics. TaAlOx films having thickness of 11.5–26.0 nm, with equivalent oxide thickness (EOT) of ~ 2.3–5.3 nm were deposited on top of Au/SiO2 (180 nm)/Si (100) structures by radio frequency magnetron co-sputtering of Ta2O5 and Al2O3 targets. The surface chemical states of the as-deposited TaAlOx films were characterized by high-resolution X-ray photoelectron spectroscopy. The crystallinity of the TaAlOx films for various post-deposition annealing treatments was characterized by grazing incident X-ray diffraction, which reveals that an amorphous phase is still retained for rapid thermal annealing up to 500 °C. Besides a high capacitance density (~ 5.4 to 6.6 fF/μm2 at 1 kHz), a low value of voltage coefficients of capacitance and a stable temperature coefficient of capacitance have also been obtained in MIM capacitors with TaAlOx films. Degradation phenomenon of TaAlOx-based MIM capacitors under constant current stressing at 20 nA is found to be strongly dependent on dielectric thickness. It is shown that Al-incorporated Ta2O5 (TaAlOx) films with high band gap and good thermal stability, low leakage current and good voltage linearity make it one of the most promising candidates for metal–insulator–metal capacitor applications.