Leakage current mechanisms of Metal-Ta2O5-metal capacitors for memory device applications

摘要

[[abstract]]Tantalum oxide (Ta2O5) is an important material for future dynamic random access memory capacitor and metal oxide semiconductor field effect transistor gate oxide applications. In this work, the electrical and material properties of amorphous Ta2O5 metal insulator-metal capacitors deposited by plasma-enhanced chemical vapor deposition (PECVD) on a tungsten bottom electrode are studied. The minimum thickness of Ta2O5 is 14 nm which is equivalent to a SiO2 thickness of 2.58 nm. High-quality dielectric characteristics such as a leakage current density of 3 × 10–8 A/cm2 at 0.75 V for both voltage polarities, a capacitance of 13.8 fF/µm2, and a breakdown strength of 8.23 MV/cm when the bias is negative, are obtained. These high-quality characteristics are most likely due to the complete decomposition of the precursor Ta(OC2H5)5 by oxygen plasma during plasma deposition. The current conduction mechanism of amorphous Ta2O5 is investigated. A comparison between Ta2O5 deposited by PECVD and by low-pressure chemical vapor deposition is also studied.