铁电存储器^(60)Co γ射线及电子总剂量效应研究

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

以型号为FM28 V100的铁电存储器为研究对象,进行了^(60)Co γ射线和2 Me V电子辐照实验.研究了铁电存储器不同工作方式、不同辐射源下的总剂量辐射损伤规律,用J-750测试部分直流参数和交流参数,分析了存储器敏感参数的变化规律.实验结果表明:对动态、静态加电、静态不加电三种工作方式下的结果进行比较.其中静态加电工作方式下产生的陷阱电荷最多,是存储器最恶劣的工作方式;器件的一些电参数随总剂量发生变化,在功能失效之前部分参数已经失效;在静态加电这种最恶劣的工作方式下,得到^(60)Co γ射线比电子造成更加严重的辐照损伤.

Ferroelectric random access memory（Fe RAM） 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 Fe RAM have not been rich in the literature so far. Experimental study of the ionizing radiation effect of Fe RAM is carried out based on Co-60 γ rays and 2 Me V electrons. And the TID radiation damages to the Fe RAM 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 Fe RAM 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 Fe RAM 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 Fe RAM 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 Fe RAM 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-60γ 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 Fe RAM and will be of great significance for studying the radiation hardening of Fe RAM.