Novel polarised ferroelectric thin films for silicon integrated devices

• Research unit: COST
• Project number: C94.0012

Key words (English)

Lithium tantalate thin films; polarised ferroelectric; pyroelec; polarisation; ruthenium oxide

Research programs (English)

COST-Action 514 - Ferroelectric ceramic thin films

Short description (English)

See abstract

Partners and International Organizations (English)

B, CH, D, DK, E, F, FIN, I, IRL, P, S, SI, TR, UK

Abstract (English)

ABSTRACT Microelectronic devices based on ferro-, pyro- and piezo-electric thin films can make useful contributions to certain sensors and actuators. The present project concentrated on polycrystalline lithium tantalate (LiTaO3) deposited by sputtering. The first goals of a successful deposition of pyroelectric layers are the obtention of the correct stoichiometry and the achievement of a good line-up of the domains (poling). A saturation polarization of 30.x10-6 C/cm2 and a coercitive field of 12 kV/cm could be obtained. These values compare well with those reported for ceramic films of the same material. The most crucial problem with sputtered pyro- and ferro-electric films is the understanding and control of interfacial reactions taking place during the crystallization heat treatment. Reactions generating non pyro-electric phases cause a serious degradation of the functional properties of the films. Such undesired phases may develop at grain boundaries and at the film/electrode interfaces. Main conclusion: The correct stoichiometry has been obtained by sputtering in an oxygen/argon mixture. The interfacial reactions have been minimized by sputtering on top of SiO2, and depositing the electrodes after the crystallization heat treatment. The effects of the grain boundaries have been analyzed by impedance spectroscopy. One special interest of sputtered pyroelectric films deposited on a silicon substrate is the possibility of fabricating thermal sensors with a very small mass thanks to an anisotropic back etching of the substrate. A prototype of a thermal detector has shown a better performance than a commercial device between 10 Hz and 10 kHz.

References in databases (English)

Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. [phone] Swiss Project-Number: C94.0012