Time and temperature dependencies of imprint characteristics in SrBi2Ta2O9 capacitors

et al. 2005

Jpn. J. Appl. Phys.

Self Cite

We investigated hysteresis shifts in SrBi2Ta2O9 capacitors during high-temperature storage in an attempt to understand the mechanism underlying imprint degradation. We found that the activation energy (E a) of imprint degradation is derived from the temperature dependence of the hysteresis shift, but is almost independent of the size of the capacitors (about 0.2 eV). On the other hand, E a is strongly dependent on the size of contact areas on the upper electrodes of the capacitors (0.1 to 0.2 eV). This result suggests that imprint degradation is mainly due to the characteristics of ferroelectric-electrode interfaces, and is not due to the edges of the capacitors. We reached this conclusion because the dependence on the contact areas is related to process-induced damage near the upper electrode.

Section: Introductionmentioning

confidence: 65%

Section: Methodsmentioning

confidence: 99%

Dependences of Process-Induced Damage on Imprint Characteristics in SrBi₂Ta₂O₉ Capacitors

Ashikaga¹,

Takaya²,

et al. 2005

Jpn. J. Appl. Phys.

Self Cite

“…It was found that the hysteresis shifts are the most important parameters for understanding the imprint characteristics. 6) In this paper, we focus on the conditions for measuring imprint characteristics.…”

Section: Introductionmentioning

confidence: 99%

Effects of Storage Conditions on Imprint Characteristics in SrBi₂Ta₂O₉ Capacitors

Ashikaga¹,

Takaya²,

et al. 2006

jjap

Self Cite

The effects on the imprint characteristics of SrBi2Ta2O9 capacitors of various storage conditions were investigated. It was observed that the hysteresis shifts due to imprint degradations were smaller in the case in which the both electrodes of the capacitors were connected after increasing the temperature of the capacitors that were polarized at room temperature than in the case in which the electrodes were not connected. The acceleration ratio (Racc) of the slope of the hysteresis shift in the capacitors without connected electrodes to that with connected electrodes is 1.35 at 125 °C in device-size capacitors, and the ratio is much less dependent on temperature than the hysteresis shift. Moreover, it was also found that Racc was smaller in the case in which the process-induced damage located near the interfaces was larger.

“…Therefore, the imprint degradations were improved by postmetallization annealing because the hysteresis shifts are related to the intrinsic imprint characteristics. 6) As mentioned, two kinds of damage are induced in capacitors during contact hole formation on a tungsten plug and during first-metal formation, and these kinds of damage seem to be recovered by low-temperature postmetallization annealing. However, it is unlikely that the kinds of damage which degrade the ferroelectric characteristics are eliminated completely by annealing at 400 C. Hydrogen and water are known to degrade ferroelectric characteristics.…”

mentioning

confidence: 98%

“…The sequence for imprint measurement was described in detail elsewhere. 6) Two parameters are used to determine the imprint characteristics: hysteresis shift (ÁV) and switching characteristic (ÁQ). ÁV corresponds to ½V c ðþÞ þ V c ðÀÞ=2.…”

mentioning

confidence: 99%

Reduction of Process-induced Damage and Improvement of Imprint Characteristics in SrBi₂Ta₂O₉ Capacitors by Postmetallization Annealing

Ashikaga¹,

Takaya²,

et al. 2007

jjap

Self Cite

We investigated the effect of process damage induced after capacitor etching procedures in the process of ferroelectric random access memory (FeRAM) fabrication for SrBi 2 Ta 2 O 9 capacitors. We found that this damage was suppressed by postmetallization annealing (400 C, 30 min in O 2 ) and that imprint characteristics were improved by the annealing, because active elements such as hydrogen and water induced during contact hole formation on tungsten plugs and first-metal formation are adsorbed effectively by the annealing before they penetrate into these capacitors.