Voltage Shift Effect on Retention Failure in Ferroelectric Memories

Abstract

A new measurement of the thermodynamic temperature interval between the silver and the gold freezing points with an infrared pyrometer has been carried out. The value of the freezing point of gold, referred to the value of the silver point on the IPTS-68, thus obtained, is 1337.41 K (a= 0.059 K). The ratio of the spectral radiances a t the two points is 2.4428 (a= 1.2 . 10-3) at the meaneffective wavelength&= 0.9980ym (a= 0.3 nm). The resulting temperature interval is 0.17 K shorter than the IPTS-68 interval between the same points.

Mechanism of Charge Retention Loss in Ferroelectric Pt/Pb(Zr,Ti)O 3 /Pt Capacitors and Its Relation to Fatigue and Imprint

“…Figure 4 shows long-time retention data P SS (≡ P * SS − P ∧ SS ) and P OS (≡ P * OS − P ∧ OS ) as a function of baking time t b . For the same-state retention, there was practically no change in P SS , in agreement with the earlier reports [8][9][10]. However, for the opposite-state retention, about 45% loss was observed in P OS after 100 h baking at 125 • C. This result shows that the opposite-state retention loss is a much more serious issue for practical applications.…”

“…Same-state retention can be defined as the ability to retain a given logic state as time elapses after writing. A long duration after writing can cause imprint [5,6,8], and can thus affect the retention characteristic of the subsequent logic state if it were written oppositely to the previous one. The retention characteristic of this oppositely written logic state is referred to as "opposite-state" retention.…”

“…The retention loss is generally thought to be due to the presence of internal electric field [3][4][5][6][7][8][9][10][11], although, the mechanism of charge retention loss is not well understood yet. A significant amount of polarization loss was found to occur within the first second after writing pulse (short-time regime, t < 1 s) and a relatively slight decay was followed thereafter (long-time regime, t > 1 s) [3,6,7].…”

“…In the short-time regime, depolarization field is considered to be the main origin of the polarization decay [3][4][5][6]11]. On the other hand, in the long-time regime, retention loss was found to be accompanied with imprint [5,6,8] The development of internal field due to the redistribution of defect charges was thought to be responsible for the retention loss and imprint. However, the detailed process of the internal field development nor the relation between the internal field and retention loss is not well understood as yet.…”

Cell Signal Distribution and Imprint Reliability in FeRAM with Hybrid Bit Line Architecture

“…FeRAMs use two polarization states of ferroelectric capacitors as logic "1" and "0" states [1,2]. The sensing signal margin for distinguishing data is determined by the magnitude of switching charge, non-switching charge, and bit line (BL) capacitance (C BL ) [3]. Since nonuniform ferroelectric properties in the storage capacitors leads to large distribution of cell signals, the cell signal interference between neighboring BLs in FeRAMs severely reduces the sensing signal margin.…”