Ferroelectric Dielectrics Integrated on Silicon

Chapter 7Leakage Currents in PZTCapacitors ¹

 

 

 

7.1. Introduction

Many models have been proposed in the literature in recent years to describe the conduction mechanisms of leakage current in ferroelectric thin films. For the same material PZT, it is possible to find models based on a conduction limited by the interfaces such as Schottky injection [CHE 94a, SUD 94, WOU 95a], or tunneling [KUR 01], as well as some mechanisms limited by the bulk of film like Poole-Frenkel emission [ALS 96, CHE 98, MIH 95], or space-charge limited conduction [HUH 94, SCO 94]. The wide variety of results available in the literature comes not only from the difficulty of acquiring electrical characteristics representative of the so-called “true” leakage current material, but also from the complexity of interpretation of these characteristics.

The most common method for characterizing the leakage current conduction mode in a metal/insulator/metal structure is based on the analysis of I(V) curves obtained by applying a voltage ramp. However, in the case of capacitors made of perovskite type titanium oxides, such as PZT, the recorded current density obtained in response to the application of a constant voltage stress turns out to be characterized by very significant intensity variation over time. Thus, during the acquisition of I(V) curves, the application conditions of the voltage ramp significantly affect the measurement of current and thus the interpretation of results. Many authors point out that ...