The effect of Pb stiochiometry on switching behavior of Pt/lead zirconate titanate/Pt ferroelectric capacitors
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J. Maes and E. Coppye Department of Metallurgy and Materials Engineering, KU Leuven, De Croylaan 2, B3001 Leuven, Belgium
Laura Fe` and D. Wouters Interuniversity Microelectronics Center (IMEC), Kapeldreef 75, B3001 Leuven, Belgium
O. Van der Biest Department of Metallurgy and Materials Engineering, KU Leuven, De Croylaan 2, B3001 Leuven, Belgium (Received 6 April 2000; accepted 19 July 2000)
A promising approach to control Pb stoichiometry during crystallization of sol-gel-derived lead zirconate titanate (PZT) layers is presented. Pyrolyzed layers were encapsulated in a quartz ampoule containing PbZrO3 powder and crystallized in a lamp furnace. For moderate heating rates, the PbO ambient created by the powder resulted in a pronounced sharpening of the preferential (111) texture, while the remanent polarisation Pr increased by 50% compared to nonencapsulated samples. A significant reduction of the coercive field was seen for layers crystallized under PbO ambient, reflected in a lowering of the switching voltage by 0.5 V compared to standard hotplate crystallized films. The results highlighted the key role of Pb stoichiometry control for further lowering the switching voltage of PZT films.
I. INTRODUCTION
Ferroelectric oxides are rapidly gaining importance in microelectronics as the enabling materials in nonvolatile memories [ferroelectric random-access memory (FERAM)] based on destructive readout of ferroelectric capacitors. Among the different candidate materials, [Pb(Zr,Ti)O3; (PZT)] offers the advantages of low processing temperature and a large value for the remanent polarization. Because of the relatively high coercive field of PZT, the use of layers with reduced thickness (
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