This paper reviews deposition, integration, and device fabrication of ferroelectric PbZrxTi1-xO3 (PZT) films for applications in microelectromechanical systems. As examples, a piezoelectric ultrasonic micromotor and pyroelectric infrared detector array are presented. A summary of the published data on the piezoelectric properties of PZT thin films is given. The figures of merit for various applications are discussed. Some considerations and results on operation, reliability, and depolarization of PZT thin films are presented.

http://iopscience.iop.org/article/10.1088/0960-1317/10/2/307/pdf

Ferroelectric thin films for micro-sensors and actuators: a review

Ceramic integration technology requires downsizing and/or improvement of device performance in many applications, such as in the fabrication of microelectromechanical systems, display devises, fuel cells, optical devices, and RF components. For these applications, realization of high-speed deposition rate, low process temperature, and fine patterning in ceramic coating are very important. The aerosol deposition (AD) method has many advantages for above requirements in comparison with conventional thin-film method or thermal spray coating technology. In this article, advantages of the AD method are highlighted by realizing a comparison with conventional thin-film methods and thermal spray technology. Challenges associated with AD method are also highlighted. At the end, examples of integration of AD method in the fabrication of electronic components are also given to show the easiness in usage and in integration of this method in the device process flow.

Room Temperature Impact Consolidation (RTIC) of Fine Ceramic Powder by Aerosol Deposition Method and Applications to Microdevices

This paper reviews deposition, integration, and device fabrication of PbZr/sub x/Ti/sub 1-x/O/sub 3/ (PZT) films for applications in micro-electromechanical systems. An ultrasonic micromotor is described as an example. A summary of the published data on piezoelectric properties is given. The figures of merit for various applications are discussed. Some considerations and results on operation, reliability, and depolarization of PZT thin films are presented. The state of the art allows some preliminary conclusions.

PZT thin films for microsensors and actuators: Where do we stand?

A ferroelectric dielectric for microwave applications is provided including a polycrystalline perovskite phase of lead zirconate titanate dielectric material. Small grain size material is provided by a low temperature process, by a rapid thermal annealing process. A layer of amorphous ferroelectric precursor material is deposited and annealed in an oxygen containing atmosphere in the presence of water vapour, preferably with the addition of a few percent of ozone, and at a temperature of less than 500° C. Advantageously, the method provides for formation of a ferroelectric material including lead zirconate titanate with a grain size less than 20 nm, with low film stress, high dielectric constant and low leakage current, which has excellent ferroelectric characteristics up to 10 GHz. This material has applications for capacitors, as filters, decoupling, coupling, and bypass elements and also for high frequency surface acoustic wave devices.

Ferroelectric dielectric for integrated circuit applications at microwave frequencies

The dielectric properties of 〈100〉-oriented epitaxial ${\mathrm{SrTiO}}_{3}$ films as used in high-${\mathit{T}}_{\mathit{c}}$ heterostructures have been studied as a function of temperature and applied electric field by using in situ grown heterostructures (Mg/${\mathrm{SrTiO}}_{3}$/${\mathrm{SrTiO}}_{3}$:Nb and Au/${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{x}}$/${\mathrm{SrTiO}}_{3}$/${\mathrm{SrTiO}}_{3}$:Nb). The dielectric behavior of these films is characterized by a rather low sample capacitance as compared to bulk single-crystal values and by occurrences of maxima in the capacitance-voltage and capacitance-temperature curves. The maximum attainable polarization was found to be 80 mC/${\mathrm{m}}^{2}$ at 4.2 K. Complementary measurements on single crystals of ${\mathrm{SrTiO}}_{3}$ and ${\mathrm{SrTiO}}_{3}$:Nb reveal that the behavior of these ${\mathrm{SrTiO}}_{3}$ thin films can be understood from the bulk properties with additional strong charge trapping at the film-substrate interface.

Dielectric properties of sputtered SrTiO 3 films

Lead zirconate titanate films have been fabricated by a dc sputtering technique with a post deposition rapid thermal annealing treatment at 650 °C for 10 s. The films exhibited good structural, dielectric, and ferroelectric properties compared to conventional furnace‐annealed films. The measured dielectric constant and loss tangent at 1 kHz were 900 and 0.04 and the remanent polarization and coercive field values were 10 μC/cm2 and 23 kV/cm, respectively. No significant fatigue in polarization was observed in the films up to 1010 cycles of bipolar stress. The films were optically transparent and showed a linear electro‐optic (EO) effect after poling with an EO coefficient of 1.5×10 −11 m/V.

Lead zirconate titanate films by rapid thermal processing

Thin PZT films 1-4 μm in thickness prepared by sputtering or sol gel methods allow PZT films to be integrated with silicon technology to achieve piezoelectric or pyroelectric structures having small size or mass. Design criteria, materials and processing techniques for such devices are discussed, and the implementation of small size devices on silicon substrates is demonstrated. Factors of importance are the piezoelectric and pyroelectric characteristics achievable in the films, mechanical strength and fatigue, and the stability and compatibility of the films and electrodes with device fabrication procedures and operating conditions.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400480826

Integrated Piezoelectric and Pyroelectric Devices from Thin Film Ferroelectrics

The preparation of ferroelectric lead zirconate titanate (PZT) thin films by rapid thermal processing (RTP) is reported. The films were deposited by chemical sol gel and physical sputter techniques. The heating rate of RTP was found to have significant influence on the crystallization behavior. Faster heating rates lead to lowering of the crystallization temperature and reduction of grain size. PZT films were obtained with dielectric constants:_ 1000, remanent polarizations between 20 and 30μC/cm2, coercive fields 20 to 60kV/cm, and no significant fatigue for 109 to 1010 stressing cycles.

Rapid Thermal Processing of Ferroelectric Thin Films

Sol gel prepared PZT films from 0.3–1.0 μm in thickness can be crystallised at temperatures down to 520°C on aluminium substrates, but such films are often non-ferroelectric. Comparison with films made on Pt substrates suggests that reduced oxygen content at the interface nucleates a cubic non-ferroelectric PZT phase.

Crystallization of Sol Gel Pzt on Aluminium and Platinum Metallizations

Ultrasonic transducers, microactuators and resonators using sol gel PZT films, polymer membranes and silicon machining techniques can take the form of cantilevers, membranes, and array sensors. Static deflections in simple electrode configurations for PZT films supported on silicon or silicon nitride membranes are of the order of 1 µm, while larger deflections can be developed under ac and resonant excitation. High frequency acoustic actuators using capacitative excitation of polymer films have been used to evaluate the performance of piezoelectric sensors.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400403660

C.V.R. Vasant Kumar

Papers

Lead zirconate titanate films by rapid thermal processing

Integrated Piezoelectric and Pyroelectric Devices from Thin Film Ferroelectrics

Rapid Thermal Processing of Ferroelectric Thin Films

Crystallization of Sol Gel Pzt on Aluminium and Platinum Metallizations

Piezoelectric and Capacitative Microactuators and Devices