DC leakage and failure of PZT thin film capacitors for non-volatile ferroelectric memory and dram applications

Abstract

DC leakge and dielectric breakdown of Pb(Zr_xTi_1−x)O₃ (PZT) thin films have been studied. Three regions in the time spectrum of the DC leakage current are discussed. It is emphasized that it is important to measure the time dependence of current before doing current versus voltage (I–V) measurements. Resistivity degradation is observed after a DC voltage is applied for a certain length of time. It is found that the resistivity degradation is dependent on voltage polarity and humidity of the atmosphere. It is pointed out that the time dependent dielectric breakdown (TDDB) must be distinguished from the phenomenon of resistivity degradation. It is found that breakdown in PZT thin films is defect related. The difficulty of confirming whether the breakdown mechanism is electrical (i.e., intrinsic) or thermal is discussed.

Keywords:

• ferroelectric thin film
• leakage
• dielectric breakdown
• reliability
• ferroelectric memory
• DRAM
• thin film capacitor
• degradation