Retention Characteristics of a Ferroelectric Memory Based on SrBi₂(Ta, Nb)₂O₉

Abstract

The polarization decay process in SrBi2(Ta, Nb)2O9 capacitors and retention characteristics of a 288-bit ferroelectric memory device fabricated from SrBi2(Ta, Nb)2O9 were studied. The remanent polarization decay at room temperature showed good linearity when plotted against logarithmic retention time over a wide range of 10-3–105 s. The distribution of times to failure of a 288-bit memory was fit to a model having a linear relationship between log (log t f) and 1/T for the period of infant failures and to the Arrhenius model having the form log t f vs 1/T for the period of random failures, where t f is the time to failure and T is the temperature. The activation energy was found to be 0.35 eV for infant failures and 1.15 eV for random failures. Possible causes for the difference in activation energies are discussed.

Retention properties with high‐temperature resistance in (Bi,Pr)(Fe,Mn)O3 thin film capacitor

“…Furthermore, PZT thin films showed serious polarization losses at high temperature due to their weak heat-resistance [4][5][6]. Note that this polarization loss was also observed in other ferroelectric materials with high-Tc such as SrBi2Ta2O9 (SBT) [9,14].Pb-free ferroelectric BiFeO3 (BFO) has attracted much attention due to its high Curie temperature (830 °C) [15][16][17][18][19]. In addition, recent reports of a large spontaneous polarization (over 100 µC/cm 2 ), which enable to integrate…”

“…Furthermore, PZT thin films showed serious polarization losses at high temperature due to their weak heat-resistance [4][5][6]. Note that this polarization loss was also observed in other ferroelectric materials with high-Tc such as SrBi2Ta2O9 (SBT) [9,14].…”

“…However, it is known that remnant polarization in PZT film capacitors shows serious polarization loss at high temperature [4][5][6]. Many researchers have focused on revealing the mechanism of polarization loss [4,[6][7][8][9][10][11][12]. It was explained that the internal field, which is formed by redistribution of defects charges near the interface between electrodes and ferroelectric layer, initiates the polarization back-switching during the retention time.…”

Retention characteristics in Bi3.25La0.75Ti3O12 thin films prepared by the polymeric precursor method

“…In most retention studies, ferroelectric capacitors exhibited a significant loss in retained polarization within the first 1 s after writing and then a relatively slight decay thereafter. [3][4][5][6][7] Retention loss causes a reduction in the difference between switched ͑P * ͒ and nonswitched ͑Pˆ͒ polarizations, i.e., ⌬P = ͑P * ͒ − ͑Pˆ͒ and leads to an inability to distinguish between the two logic states. Therefore, it is quite important to have good retention properties for any ferroelectric material to be utilized for FRAM applications.…”

Formation of PZT thin‐film capacitors over W‐plugs and low‐voltage operation for high‐density LSIs

“…Here, if the doubled remanent polarization 2Pr, nv at time t is expressed by 2Pr, nv P 0 mlogt [5], their coefficients m indicating time dependence are distinctly different. As shown in Fig.…”