Ferroelectric PZT/Si structure for integrated sensor applications

Pulsed laser ablation of ferroelectric PZT thin films on silicon cantilever beams to form composite structures for acceleration sensing applications i s reported. Optimal thin film growing conditions and voltage sensitivity an d linearity properties of the sensor as well as piezoelectric properties of the PZT films are presented and discussed in this paper. PZT layers have been deposited on the highly stressed part of silicon canti lever beams, by using a Nd-YAG pulsed laser. The depositions were made onto Au electrodes previously patterned on the silicon beam. The active layers were grown to a thickness of approx. 2 mu m. The substrate temperature of 3 75 degrees C was found to be sufficient to obtain a high crystallization an d orientation of the films, Moreover the moderate heating during deposition allowed to avoid damage to the Au electrode and Si substrate. The obtained films were analyzed by EDS, XRD, SIMS and SEM. After deposition the upper electrode was patterned and the silicon beam was mounted on a holder. Few d ifferent sensor structures have been constructed. An acceleration of the su pport applied by a standard vibrator device produced a variation of stress in the silicon beam which was sensed by the piezoelectric thin film whose o utput signal was amplified by a charge amplifier and calibrated with a stan dard accelerometer The Frequency response and voltage sensitivity have been obtained for each configuration. Piezoelectric coefficient and free dielec tric permittivity have been also obtained. These simple cantilever experime nts confirmed that a piezoelectric thin film structure can be used in integ rated sensors on silicon substrates.