Fabrication And Characteristic Study Of BLT/PZT/BLT Ferroelectric Thin Films By Sol-Gel

Ferroelectric Random Access Memories(FeRAM) is a new kind of non-volatile memories which possesses excellent properties of low operating voltage, low power consumption, long-time retention, quick writing-operation and outstanding anti-radiation characteristics, and is very suitable for embedded application. Nowadays the ferroelectric thin films in majority of commercial FeRAM are made of PZT materials. In this paper, it is mainly focused on experimental research of improving performance of PZT ferroelectric thin films.This paper is based on the principle that multi-layered ferroelectric thin films are capable of utilizing advantages of multiple ferroelectric materials. And a series of BLT, BLT/PZT, BLT/PZT/BLT thin films were fabricated on Pt/TiO2/SiO2/p-Si(100) substrate. The ferroelectric properties of BLT thin film are investigated and subsequently the best parameters of fabrication craft are determined. We also discussed the structures and properties of sandwich structured BLT/PZT/BLT thin films and made comparison of crystal structure and performance with BLT and PZT thin films, and then obtained relationship of relative intensity and ferroelectric properties of dominating diffractive apexes which emerged in a series of BLT/PZT/BLT thin films with different structure parameters.Experimental result indicated that compared with pure PZT thin film BLT thin films exhibited excellent character of fatigue-free. Owing to the introduction of BLT layers, BLT/PZT thin films' polarization character were distinctly improved, which is apparently different from PZT thin film with limitation of polarization fatigue, and simultaneously remained excellent ferroelectric properties. The remnant polarization of BLT thin films are almost the same as PZT thin films with similar thickness. The result of XRD test demonstrated that sandwich structured BLT/PZT/BLT thin film exhibited random crystal tropism, good ferroelectric properties and enough remnant polarization. Along with changes of thickness of PZT layers and BLT layers, the crystal structures and ferroelectric properties of sandwich structured thin films exhibited inerratic changes. The sandwich structured thin films also exhibited no polarization fatigue, which was brought by BLT layers, big remnant polarization and rectangular shaped ferroelectric hysteresis loop which are PZT thin films' dominant virtues. These results suggest that the sandwich structure BLT/PZT/BLT thin film is a promising material combination for ferroelectric memory applications.