Fabrication And Neutron Radiation Effect Of MFIS Structured Capacitors

Ferroelectric field-effect transistors structured with a metal-ferroelectric-insulatorsemiconductor(MFIS-FET) have been considered as potential candidates for nonvolatile FET-type memory devices for future space applications because of their significant advantages, such as a simple device structure, a low power consumption, the possibility for a nondestructive readout operation and especially the good radiation hardness. And MFIS-FETs have attractive prospect in aerospace. In order to study the performance of MFIS-FETs on the condition of radiation, ground simulation experiments are typically used to evaluate the radiation damage. In this paper, the MFIS capacitors using Pt/Bi3.15Nd0.85Ti3O12(BNT) /Sr Ti O3(STO)/Si were fabricated via sol-gel method and then exposed to neutron radiation with fluence of 1.0×1015 n/cm2 and 1.0×1014 n/cm2, respectively. The main contents and results are given as follows:(1) The MFIS capacitors structured with Pt/BNT/STO/Si(100) were fabricated by the sol-gel method. The electrical properties of the MFIS capacitors were investigated. The STO as an insulating layer shows relatively high dielectric constant and good electrical properties. The MFIS structure exhibits a memory window of 2.5 V, a low leakage current density of 10-8 A/cm2 and a long retention time of over 7.5 hours. The experimental results show that this MFIS structure is suitable for ferroelectric field-effect transistors. And lay a foundation for neutron radiation experiments.(2) The prepared samples were subjected to neutron radiation with fluence of 1.0×1015 n/cm2 and 1.0×1014 n/cm2, respectively. The microscopic structure and electrical properties of the Pt/BNT/STO/Si capacitors were also measured. The comparative analysis of microstructure and performances before and after radiation were presented. The results indicate that it is not greatly to change the crystal structure when BNT and STO films were subjected to 1.0×1015 n/cm2 neutron radiation. But with the increase in fluence, the memory window decreases, the leakage currents are higher and a decay of the retention time occurs. The degradation can be explained as the migration of oxygen vacancies induced by neutron radiation.