Researches On Radiation Effects And Radiation-hardening Of Ferroelectric Random Access Memories

Semiconductor memories play a crucial role in aerospace electronic systems. They are utilized for storage of critical data including instruction codes, flight status parameters, etc. With the development of space industry, flight system calls for higher performance of the electron devices. As the most developed novel non-volatile memory technology, ferroelectric random access memories(FRAMs) possess superior features such as short access time, low power consumption, high endurance, and suitable for embedded design. Besides, the ferroelectric materials are highly tolerant to radiation. These advantages make FRAM a promising alternative to the traditional memories used in space missions. However, the radiation performance of FRAM needs to be thoroughly studied before the practical application for the safety of spacecraft. The domestic research on the radiation effects of FRAM has just started, and few literature reports are available at present. There are many related issues remain to be studied. In this dissertation, in-depth study is conducted on the irradiation test method, radiation effects, failure mechanism, simulation method and radiation-hardening techniques of FRAMs. Specifically, the main content in this dissertation include:1. Based on the domestic ground radiation sources, the methods and procedure of the FRAM irradiation tests including the total ionizing dose(TID) effects and single event effects(SEEs) irradiation tests are studied. The FRAM test system is implemented on FPGA board for the irradiation tests. The 60 Co gamma source is used to study the TID effects of multiple types of FRAMs. The results provide reference data for the future space application and hardened design of FRAM.2. The microbeam X-ray is used to study the TID effects of internal circuits function blocks of FRAM, so that the TID sensitivity and failure mode of each block can be studied and the weak spots can be located for the hardening work to enhance the overall FRAM reliability. The difference between the microbeam X-ray and 60 Co gamma ray irradiation results is quantitatively compared. The feasibilities and limitations of the microbeam X-ray on studying the TID effects of large-scale integrated circuit are discussed.3. The SEEs of FRAM caused by the HI-13 tandem-accelerator is studied. Both the static mode and dynamic mode are tested. The linear energy transfer(LET) threshold of the single event upsets(SEUs) and single event latch-up(SEL) are evaluated, and the saturated SEU cross sections are obtained.4. The SEU mechanism of ferroelectric memory cell is studied by device simulation and circuit simulation. The impact of single event transient(SET) pulse on the polarization status of the ferroelectric thin film capacitor is simulated. The influence of the ferroelectric capacitor area and coercive electric field on the SEU sensitivity is analyzed. The changes of readout signal on bit line caused by the SET pulse and the resulting upset types are also studied based on circuit simulation.5. The CMOS-based radiation hardening techniques of FRAM are studied. The TID resistances of regular and enclosed-gate NMOSs are quantitatively compared based on standard 0.18 μm CMOS process. Under the same process, the radiation hardness of sense amplifier based on regular and enclosed-gate NMOS design are studied. The effectiveness of shunt MOS design on reducing the SET pulse in ferroelectric memory cell is simulated. A 512 bit radiation hardened FRAM based on radiation-hardened-by-design(RHBD) technique is designed for the future research work.