1995 Fiscal Year Final Research Report Summary
IMPROVEMENT OF FATIGUE PROPERTIES IN FERROELECTRIC NONVOLATILE MEMORY PREPARED BY PULSED LASER ABLATION
| Project/Area Number |
06650010
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Applied materials science/Crystal engineering
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| Research Institution | KANAZAWA UNIVERSITY |
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Principal Investigator |
MORIMOTO Akiharu FACULTY OF ENGINEERING,DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING ASSOCIATE PROFESSOR, 工学部, 助教授 (60143880)
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| Co-Investigator(Kenkyū-buntansha) |
KUMEDA Minoru FACULTY OF ENGINEERING,DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING PROFESS, 工学部, 教授 (30019773)
SHIMIZU Tatsuo FACULTY OF ENGINEERING,DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING PROFESS, 工学部, 教授 (30019715)
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| Project Period (FY) |
1994 – 1995
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| Keywords | PULSED LASER ABLATION / FERROELECTRIC NON-VOLATILE MEMORY / LEAD-ZIRCONATE-TITANATE / Ni-ALLOY ELECTRODE / TITANIUM ALUMINUM NITRIDE / MAGNESIA BUFFER LAYER / SWITCHED CHARGE / FATIGUE RESISTANCE FOR SWITCHING |
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| Research Abstract |
For metal/ferroelectrics/metal (MFM) memory, ferroelectric lead-zirconate-titanate (Pb (Zr_<0.52>Ti_<0.48>) O_3 : PZT) thin-film capacitors were fabricated by ArF pulsed laser ablation (PLA) using Ni-alloy electrodes on oxidized (100) silicon. The fatigue test revealed that the increase in the frequency both for acceleration and measurement of switching pulse increases the life of polarization reversal while it decreases the switched charge density Q_<SW>. At 50 kHz, Q_W keeps the initial value even after switching above 10^<10> cycles. The measurement frequency dependence of Q_<SW> suggests that a homogeneous fatigue takes place irrespective of fast and slow domains and additional layrs of a low dielectric constant are probably formed in the ferroelectric-metal interface.
The effect of various electrodes on the ferroelectric properties of PZT films through the film structure is also presented. These experiments revealed that there is no simple correlation between the film structure and the fatigue resistance. The fatigue resistance is, however, found to be improved primarily by decreasing Q_<SW>, although the correlation shows some ambiguity. For examining the fatigue properties, titanium-aluminum-nitride (Ti-Al-N ; TAN) electrode films were proposed for PZT thin-film capacitors. Capacitors with rather randomly oriented PZT films on the TAN/(100) Si did not show a ferroelectric hysteresis loop, but the capacitor with preferentially [100] -oriented PZT film on the TAN/(100) MgO did. This suggests that a TAN-electrode film was grown on (100) MgO with a high oxidation resistance at the high temperature employed for ferroelectric oxide preparation.
For metal ferroelectrics/insulator/semiconductors-(MFIS-) FET memory, PZT/MgO/(100) Si structure was proposed. The PZT film obtained was found to be highly oriented perovskite PZT film with a ferroelectric P-E hysteresis.
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