Total-dose radiation-induced degradation of thin film ferroelectric capacitors

The radiation hardness of thin-film PbZr_yTi_1-y O₃ (PZT) ferroelectric capacitors is explored. Ferroelectric capacitors were irradiated using X-ray and Co-60 sources to dose levels up to 16 Mrad(Si). The capacitors were characterized for their memory properties both before and after irradiation. The radiation hardness was process dependent. Three out of four processes resulted in capacitors that showed less than 30% radiation-induced degradation in retained polarization charge and remnant polarization after irradiating to 16 Mrad(Si). On the other hand, one of the processes showed significant radiation-induced degradation in retained polarization charge and remanent polarization at dose levels above 1 Mrad(Si). A model for simulating the observed degradation is developed. The model indicates that the data are consistent with trapping of radiation-induced charge in the ferroelectric material. The radiation hardness levels indicate that ferroelectric devices can be fabricated that can survive radiation exposures well in excess of 10 Mrad(Si)