Electrical properties of sol-gel PZT thin films for decoupling capacitor applications.

摘要

The successful development of PZT thin films for decoupling capacitor devices places stringent requirements on the dielectric and leakage properties of the films. The authors have characterized these properties for PZT thin films with compositions near the morphotropic phase boundary prepared by a sol-gel process. Capacitors were fabricated from films with thicknesses varying from 0.4 to 1.2 (mu)m. For zero applied bias, the dielectric constants of these films were in the range of 800 to 1200. The room temperature dielectric constant was observed to decrease by (approximately)25% with the application of a 5 V bias. They have also characterized the interrelationships between temperature, applied bias, and dielectric constant. The capacitors exhibited asymmetry in their leakage and breakdown characteristics with bias sign, as well as non-linear I-V behavior. Breakdown fields for undoped PZT 53/47 films were typically in the range of 750 kV/cm. They have also studied the effects of La and Nb donor doping on the leakage behavior of PZT 50/50 thin films. Doping with 2 to 5 mol % of either La or Nb resulted in a reduction in film leakage current by a factor of 10(sup 3). Leakage currents of the highly doped materials were approximately 2 (times) 10(sup (minus)9) A/cm(sup 2) under an applied field of (approximately)65 kV/cm at a temperature of 125(degrees)C.