Thermal stabilities of metal bottom electrodes for Ta2O5 metal-oxide-metal capacitor structure

Abstract

Abstract Thermal stabilities of various metal bottom electrodes were examined by using a Ta 2 O 5 metal-oxide-metal (MOM) capacitor structure. After depositing 10-nm thick Ta 2 O 5 on metal-electrode/poly-Si, we performed rapid thermal oxidation (RTO) at 850 °C for 60 s in an O 2 ambient. A chemical-vapor-deposition (CVD) WSi 2 electrode showed satisfactory thermal stability after the RTO, while other examined electrode materials exhibited thermal degradation caused by oxidation failure or interfacial reaction between the substrate poly-Si and the Ta 2 O 5 . After post-annealing at 650 °C for 30 min (in N 2 condition) with CVD TiN top electrode, an effective oxide thickness ( T ox ) of ∼32 A and a leakage current density of ∼10 7 A/cm 2 at 1.25 V were obtained from the MOM capacitor with the WSi 2 bottom electrode. Other electrode materials, such as TiN, TiSi x , WN x , W, and Ta, were severely oxidized during the RTO in the MOM structures, and very poor capacitor properties were obtained in terms of T ox and leakage current.