Recovery of forming gas damaged Pb(Nb, Zr, Ti)O3 capacitors

The ferroelectric property and leakage current of metalorganic chemical vapor deposition (MOCVD)-Pt/SrBi2Ta2O9 (SBT)/Pt and dc-sputtered Pt/SBT/Pt capacitors are evaluated with the microstructures of Pt top electrodes before and after hydrogen forming gas anneal. The SBT films with MOCVD-Pt top electrodes of large grain size and dense structure show a surprising decrease of leakage current density and still exhibit ferroelectric properties after hydrogen forming. On the other hand, SBT films with dc-sputtered Pt top electrodes of small grain size show an increase of leakage current density and then polarization switching properties cannot be measured due to fairly high leakage current. The microstructures of Pt top electrodes play an important role in improving the ferroelectric and leakage current characteristics after forming gas anneal. MOCVD-Pt top electrodes can prevent the complete loss of ferroelectricity and improve the leakage current properties during forming gas treatment.

supporting

confidence: 93%

Improvements in electrical properties of hydrogen-treated SrBi2Ta2O9 capacitors with chemical vapor deposited Pt top electrode

Choi

Yoon

Lee

2001

“…A similar result had been reported for LiNbO 3 and LiTaO 3 , 10 in which hydrogen corresponding to the FTIR absorption peak of 3280 cm Ϫ1 is also only metastable. On the other hand, when incorporated hydrogen forms an O-H bond with an oxygen ion, such as in Pb͑Nb,Zr,Ti͒O 3 , 14 it shows a higher stability and it is driven out only at some elevated temperatures.…”

mentioning

confidence: 99%

Spontaneous recovery of hydrogen-degraded TiO2 ceramic capacitors

Chen

Wang

Dai

et al. 2004

Degradation of TiO 2 -based ceramic capacitors was observed after hydrogen incorporation on the termination electrodes of the capacitors via electrolysis of water. Fourier-transform infrared ͑FTIR͒ absorption spectra analysis of polished rutile single crystals clearly showed that hydrogen was incorporated into the TiO 2 lattice through the treatment. Hydrogen reduces Ti 4ϩ to Ti 3ϩ and increases the concentration of charge carriers. The degradation was found to exhibit a strong dependence on time at room temperature. The degraded properties were spontaneously recovered through an aging process, showing a spontaneous recovery unique to TiO 2 -based ceramic capacitors. It is proposed that hydrogen is metastable in TiO 2 and that hydrogen-induced degradation has different stabilities among various oxide-based components and devices. © 2004 American Institute of Physics. ͓DOI: 10.1063/1.1637942͔The effects of hydrogen incorporation in materials have been extensively studied, particularly on metals ͑hydrogen embrittlement͒ and silicon-based devices ͑passivation of dangling bonds͒. In recent years, however, more and more attention has been paid to the reactions between hydrogen and metal oxide materials. [1][2][3] In our previous studies, we found that hydrogen reacts with many metal oxides at an ambient temperature in some electrochemical processes, including electroplating 4 and the electrolysis of water. 5,6 These ambient temperature reactions usually induce obvious degradations in the properties of these oxide-based components and devices. A systematic understanding of the reactions is of great importance for improving the reliability of metal oxide-based electronic components and devices. 7For many oxide-based components and devices, the degradation induced by the reaction of hydrogen is permanent and stable at room temperature. Sometimes, an annealing in an oxidizing atmosphere can recover the degraded properties. 4,8 Obviously, the hydrogen-induced defects in those oxides responsible for the degradation can only be eliminated by high-temperature oxidizing reactions. When we studied hydrogen-induced degradation in TiO 2 -based ceramic capacitors, however, we obtained a quite unexpected result. Although hydrogen induces an obvious degradation in the capacitors, the degraded properties exhibit a strong dependence on time, and the degradation is gradually recovered through an aging process without any thermal treatment. This indicates that hydrogen-induced defects are only metastable in TiO 2 -based ceramic capacitors at room temperature, in contrast to hydrogen-induced defects in many other oxides.The composition and sintering of the TiO 2 -based temperature-compensating ceramic capacitors used in the present investigation were reported in another paper. 9 The capacitors were 0.70 mm thick and 7.5 mm in diameter, with a 4.5 mm diameter silver electrode on one surface and a 5.5 mm diameter silver electrode on the other surface. Some capacitors were placed in a 0.01 M NaOH solution and dc voltages were imposed betwe...

“…The partial recovery of degraded ferroelectric properties after the O 2 annealing was also observed in the FGA-treated SBT capacitor. 7 In this case, however, no study was reported on the degree of recovery after the N 2 annealing.…”

mentioning

confidence: 86%

“…Contrary to this, it was reported that ferroelectric properties of the FGA-treated PZT-based capacitor were fully recovered by thermal annealing in a N 2 atmosphere. 7 This suggests that the recovery mechanism of FGA-treated capacitors depends on the nature of ferroelectric materials involved.…”

mentioning

confidence: 99%

“…The following recovery process has been delineated from the present study: ͑i͒ the removal of impregnated protons from the degraded capacitor due to the chemical potential difference of protons between the forming-gas-annealed capacitor and the contacting atmosphere, and ͑ii͒ the restoration of perovskite BLT phase with the help of replenishment of the Bi and oxygen losses via diffusion from the neighboring intact region to the Bi-depleted columnar region located beneath the top Pt electrode. 7,8 the Pt/BLT/Pt 9,10 capacitor seriously degrades its ferroelectric properties during the forming-gas-annealing ͑FGA͒ step. Thus, one of the most important remaining subjects in the practical implementation of the BLT capacitor to high-density FRAM is to establish a convenient recovery method of the degraded capacitor.…”

mentioning

confidence: 99%

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Recovery process of degraded ferroelectric properties in the forming-gas-annealed Pt/Bi4−xLaxTi3O12/Pt capacitor

Chon

Jang

2003

The recovery of ferroelectric properties in the forming-gas-annealed Pt/Bi4−xLaxTi3O12/Pt (Pt/BLT/Pt) capacitor was studied by examining changes in ferroelectric responses, phase evolution, and spatial distributions of relevant species during the recovery annealing. The degraded ferroelectric properties were practically restored to their original values after the recovery annealing at 600 °C for 10 min in an O2 atmosphere. The following recovery process has been delineated from the present study: (i) the removal of impregnated protons from the degraded capacitor due to the chemical potential difference of protons between the forming-gas-annealed capacitor and the contacting atmosphere, and (ii) the restoration of perovskite BLT phase with the help of replenishment of the Bi and oxygen losses via diffusion from the neighboring intact region to the Bi-depleted columnar region located beneath the top Pt electrode.