Non-linear dielectric properties of metal–amorphous-tantalum pentoxide–metal structures

Abstract

High dielectric constant (high K) materials are becoming important due to their potential applications in embedded dynamic random access memory and radio frequency capacitors. Among high K materials that can replace silicon dioxide for these applications, tantalum pentoxide (Ta2O5) is the candidate of choice since it is already available in the semiconductor industry. One of the advantages of Ta2O5 is that it can be deposited at low temperature (<500 °C). This makes it suitable for the fabrication of metal–oxide–metal structures that require low thermal budget. The use of Ta2O5 for silicon device applications requires good electrical performances in terms of leakage current and capacitance dispersion. The roughness of the bottom electrode, as determined by atomic force microscopy measurements, is found to impact the leakage current. Capacitance voltage measurements exhibit a non-linear variation with respect to the applied bias. We suggest a model that well explains the observed capacitance variations. This model is based on the relaxation of the free carriers and the Kerr effect