Ionizing Radiation On The Effect Of Electrical Properties Of Mfis Ferroelectric Field Effect Transistor

Ferroelectric field effect transistors(FeFET), due to their exceptional advantages such as high density, non-volatile storage, simple structure, and high radiation hardness, have many application potentials in the modern electronic industry especially in the defense technology. Because the ferroelectric film and the silicon substrate of the Metal-Ferroelectric-Silicon field effect transistor(MFS-FET) may react which leads to decreased performance of the device, an insulating layer is used which forms the Metal-Ferroelectric-Insulator-Silicon field effect transistor(MFIS-FET). Although the ferroelectric film and ferroelectric capacitor have high radiation hardness, no direct evidence exists for MFIS-FET. Furthermore, because of the miniaturization of electronic device, each unit layer of the device will interact with each other, leading to complex device behavior. As a result, the original radiation hardness of the ferroelectric thin film may change. So far, the radiation hardness of FeFET is unknown. In this thesis, the radiation hardness of MFIS-FET was studied using computational approach. In particular, the effects of ionizing radiation were studied. Firstly, we studied the change in the polarization of ferroelectric layer under irradiation and its impact on the performance of MFIS-FET; Secondly, we studied the effects of the electric charge density of Silicon substrate on the performance of MFIS-FET; Lastly, we studied that the electric charge transport in the ferroelectric layer and its influence on the performance of MFIS-FET. The main results from our study include:(1)We modified the Miller model such that it is suitable for the polarization simulation of ferroelectric layer under ionization radiation, and the new model was then used to simulate MFIS-FET. The results of the simulation showed that all physical quantities of MFIS-FET under the 10 Mrad ionization radiation environment change very little compared to those without radiation. When MFIS-FET was exposed to 100 Mrad ionization radiation, the capacitance, source-drain current and other physical quantities changed obviously, which implied that the device may fail under high dosage.(2) We derived a new expression of silicon substrate surface charge in ionization radiation environment. This new expression was applied to simulate MFIS-FET. With the increase of ionizing radiation dose, we found that the change of electric charge density of the inversion layer and charge mobility of the device are small, which the change in the source-drain current was even smaller. However, the silicon surface potential changed obviously. It illustrated that ionizing radiation on silicon substrates have little effect on the performance of the device.(3)We built a charge transport model of ferroelectric layer in ionization radiation environment and the model was applied to simulate the MFIS-FET. When the proportion of charge transport was constant while the total dose of radiation increased, the curves of capacitance and source-drain current moved toward the negative voltage, and the value of source-drain current increased. When the value of total dose of radiation was constant, the curves of capacitance and source-drain current ranged within limits with the change of the block rate of insulating layer hindering electron transport. Under the ionization radiation, the existence of insulating layer was in favor of regulating and controlling the performance of the device.