Evaluation of oxide and non-oxide ferroelectric thin films on Si surfaces

摘要

Recently, much attention has been dveoted to ferroelectric thin films from the viewpoint of the application for nonvolatile memories. Among various types of ferroelectric memories, metalferroelectric-semiconductor field effect transistors (MFSFETs) are especially the promising ferroelectric random access memorier (FeRAM) becasue MFSFETs are categorized as the nondestructive memory which makes use of a remnant polarization of the ferroelectric thin films. Not only the advantage of the nondestructive properties but also the benefit from saving electricity power and decreasing memory cell size inspire the developments of FERAM by depositing ferroelectric thin films on semiconductor, especially on Si surfaces. Hoever, even if the crystalined ferroelectric thin films are grown, it is difficult to fabricate such FeRAMs involving the ferroelectric materials like Pb(Zr_xTi_(1-x))O_3 (PZT) and SrBi_2Ta_2O_9(SBT) directly on Si surfaces because of the inevitable oxidation of the Si substrate. In other workds, the success for the development of FeRAM lies not only in the crystallinity of the deposited ferroelectric films but also in avoiding the interface from oxidation.