Low-temperature preparation of SrBi2Ta2O9 ferroelectric thin film by pulsed laser deposition and its application to metal-ferroelectric-insulator-semiconductor structure with nitride buffer layers

SrBi 2 Ta 2 O 9 (SBT) ferroelectric thin films have been deposited at temperatures as low as 500 degree(s)C by Pulsed Laser Deposition method on silicon nitride (SiN x ) and silicon oxynitride (SiON), being insulating barrier against inter-diffusion. Metal-Ferroelectric-Insulator-Semiconductor (MFIS) structures has been fabricated using SiN x /SiO 2 /Si and SiON/Si and shows good C-V hystereses. It is confirmed by RBS analysis and C-V characteristics that the SiN x layer shows good barrier effect compared with SiO 2 layer. It is also clarified from the direction and voltage-scanning speed of in the C-V curve that their MFIS structures show hysteresis induced by ferroelectric polarization. An Al/SBT/SiO 2 /Si structure shows a large memory window in C-V curve and a smaller shift than those in the Al/SBT/SiO 2 /Si structure. An Al/SBT/SiON/Si structure also shows good C-V characteristics whose gradient corresponding to the SiO 2 /Si interface trap is very small. Moreover, retention characteristics of the memorized states of the capacitance have been measured and analyzed, taking into account leakage current through ferroelectric and insulator films.