YMnO3 and YbMnO3 thin films for FET type FeRAM application

We have been proposing the use of RMnO3 (R: rare earth elements) films for metal-ferroelectric-semiconductor field effect transistor (MFSFET)-type ferroelectric random access memories (Ferroelectric RAMs). This report describes the progress of YMnO3 and YbMnO3 films for FET type FeRAM application. Although highly (0001)-oriented YMnO3 films are easily obtained on a MgO, ZnO/Sapphire, Pt/Sapphire and Pt/Si substrates, it was very hard to obtain the crystalline films directly on Si or on SiO2/Si substrate. A Y-Mn-O buffer layer improved the crystallinity of the YMnO3 films on Si, and we got the C-V curve with ferroelectric hysteresis. The real ferroelectric component responsible for the C-V hysteresis was calculated to be just 8.4 nC/cm(2) by pulse measurements. On the other hand, Y2O3 buffer layer drastically improved the dielectric properties. The window width of the C-V hysteresis does not change by changing the sweep rate and measurement frequency.