Total ionizing dose effect of ferroelectric random access memory under Co-60 gamma rays and electrons

Abstract

Ferroelectric random access memory (FeRAM) has superior features such as low power consumption, short write access time, low voltage, high tolerance to radiation. Data about the total ionizing dose (TID) radiation effects of FeRAM have not been rich in the literature so far. Experimental study of the ionizing radiation effect of FeRAM is carried out based on Co-60 γ rays and 2 MeV electrons. And the TID radiation damages to the FeRAM in the dynamic biased, static biased and unbiased case are studied. The direct current and alternating current parameters are tested by J-750. The test results indicate that the stored information about the memory cell has no change before failure, the ferroelectric capacitors are still able to hold the data. Accordingly, the TID failure of the FeRAM should be mainly ascribed to the poor TID hardness of the peripheral complementary metal oxide semiconductor circuits. Besides, three types of electric fields from three working conditions can result in different generation and recombination rates of electronhole pairs. For static biased case, the internal electric field in the FeRAM is constant. It can lead to high net production of the electronhole pairs and a great number of trapped charges. Hence the radiation damage in the static biased case is most serious. With the increase of the total radiation dose, the electrical parameters of FeRAM have different degradations. Part of the parameters that can be detected by J-750, may lapse before they are detected online. Standby current, operating power supply current, leakage current and output low voltage are radiationsensitive parameters of FeRAM through analyzing the test data. And, other parameters, which have slight changes, have small effect on the degradation of the device. Furthermore, the electron accelerator is used in electron irradiation experiment. By comparing the results of the two kinds of radiation tests, it is discovered that the electrons tend to cause lighter TID degradation than Co-60 γ rays because of the high density of electrons in the electron irradiation environment and low net production rate of electronhole pairs. In addition, the electrons have weaker penetration than Co-60 γ rays due to low energy. The device packaging, the upper metal layers can also influence the experimental result of electron irradiation. The above conclusions provide a reference value for the total dose effect of FeRAM and will be of great significance for studying the radiation hardening of FeRAM.