Memory effects of SrBi₂Ta₂O₉ capacitor on silicon with a silicon nitride buffer

Abstract

The memory effects of SrBi₂Ta₂O₉ (SBT) films deposited on Si substrates with an ultra-thin silicon nitride buffer layer have been investigated. The Capacitance-Voltage (C-V) measurements indicate low densities of interface traps, suggesting a good interface between the silicon nitride buffer layer and the Si substrate. The C-V characteristics show hysteresis that is consistent with the polarization of the SBT film, but opposite to that due to the electron injection/trapping effect. When swept back and forth between -7V and + 7V, a sizable hysteresis window of ± 2V is observed. The results from a single-pulse programming experiment suggest that the switching time is shorter than 8 ns, the shortest pulse available for the experiment. These results are all obtained on samples that exhibit remanent polarizations as low as 0.15 μC/cm². Fatigue tests show only modest degradation of the memory window after 10¹¹ switching cycles. Results from forming gas annealing experiments indicate no degradation up to 400°C of annealing temperature.

Key Words:

• Ferroelectrics
• Memory
• FET
• SrBi₂Ta₂O₉
• Silicon Nitride Buffer