Electrical characteristics of Ti–Ta–O based MIM capacitors

Abstract

Amorphous Ti–Ta–O thin films were deposited by the atomic-vapor deposition technique for metal-insulator-metal (MIM) applications. Depositions were carried out at 400 °C on 200-mm Si (100) wafers using TiN and TaN as bottom electrode materials. The comparison of electrical properties of MIM capacitors was done after physical-vapor deposited growth of different top electrodes, namely, Au, TiN, TaN, and Ti. Capacitance-voltage measurements revealed that the dielectric constant of 50 can be reached if Ti–Ta–O layers are deposited on TiN and if Au, TaN, or Ti is used as the top electrode. The k value is reduced to 37 if TaN is used as bottom electrode. However, if TiN is used as the top electrode, the k value of the stack is reduced by a factor of 3, from 50 to 17, independent of whether TiN or TaN are used as bottom electrodes. The lowest leakage current values (∼10−8 A/cm2) were observed when gold was used as the top electrode, whereas it increased by 3 orders of magnitude if the top electrode was changed to TiN and even more if the top electrode was changed to TaN or Ti.