LEAKAGE CURRENT CHARACTERISTICS OF LEAD-ZIRCONATE-TITANATE THIN-FILM CAPACITORS FOR MEMORY DEVICE APPLICATIONS

The leakage cut-rent of ferroelectric thin film capacitors is comprise d of electronic conduction current and polarization current. In this w ork, the origin of these leakage current components in lead-zirconate- titanate (PZT) thin film capacitors is studied by means of two differe nt methods. The first method distinguishes the current components by m easuring the leakage current with different delay times. The second me thod determines the current components by measuring the charging and d ischarging currents when a specified voltage is turned on and off. Bot h measurements show that the polarization current is dominant in an el ectric field lower than 100 kV/cm. The polarization current is modeled using Debye-type electric polarization. The relaxation times and equi valent capacitances of the polarization current are extracted from the discharging current. The electronic conduction current obtained by me asuring the leakage current with long delay time can be explained to b e due to ohmic conduction in a low field (lower than 40 kV/cm) and Poo le-Frenkel emission in a high field (higher than 40 kV/cm). The total leakage current calculated by the sum of the polarization current and the electronic conduction current agrees well with the measured result .