Electrical conduction and breakdown in sol-gel derived PZT thin films

The viability of lead zirconate titanate (PZT) films as a storage dielectric for DRAM applications is discussed. 4000 AA PZT films with an effective SiO/sub 2/ thickness less than 17 AA were prepared by sol-gel deposition. The films exhibited ohmic behavior at low fields and exponential field dependence at high fields. The conduction characteristics can be modeled accurately using expressions derived for ionic conductivity. At the same effective SiO/sub 2/ field, the leakage and time-dependent dielectric breakdown (TDDB) characteristics are superior to other dielectric structures. However, lifetime extrapolations to worst-case operating conditions show that TDDB may be a very serious limitation for DRAM applications. Optimization of material properties of PZT films, especially the TDDB lifetime, is necessary for reliable DRAM operation.<>