IONIZING RADIATION-INDUCED ASYMMETRIES OF THE RETENTION CHARACTERISTICS OF FERROELECTRIC THIN-FILMS

A new failure mode in ferroelectric, non-volatile memories in a radiat ion environment has been identified. Exposure to ionizing radiation in combination with a series of unipolar pulses, which could be found in a read-only or read-mostly memory application, has been found to crea te a preferred memory state in the ferroelectric storage cell. This pr eferred memory state, or imprint, causes a significant asymmetry in th e retention of polarization. While ferroelectric materials remain high ly radiation tolerant, a new, more stringent testing method should be adopted for hardness assurance. The creation of a preferential memory state, or 'imprint,' in ferroelectric films and memories has previousl y only been reported in elevated temperature situations.