Laser scanners have been an integral part of MEMS research for more than three decades. During the last decade, miniaturized projection displays and various medical-imaging applications became the main driver for progress in MEMS laser scanners. Portable and truly miniaturized projectors became possible with the availability of red, green, and blue diode lasers during the past few years. Inherent traits of the laser scanning technology, such as the very large color gamut, scalability to higher resolutions within the same footprint, and capability of producing an always-in-focus image render it a very viable competitor in mobile projection. Here, we review the requirements on MEMS laser scanners for the demanding display applications, performance levels of the best scanners in the published literature, and the advantages and disadvantages of electrostatic, electromagnetic, piezoelectric, and mechanically coupled actuation principles. Resonant high-frequency scanners, low-frequency linear scanners, and 2-D scanners are included in this review.

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MEMS Laser Scanners: A Review

We demonstrate piezoelectrically actuated, electrically tunable nanomechanical resonators based on multilayers containing a 100-nm-thin aluminum nitride (AlN) layer Efficient piezoelectric actuation of very high frequency fundamental flexural modes up to ~80 MHz is demonstrated at room temperature Thermomechanical fluctuations of AlN cantilevers measured by optical interferometry enable calibration of the transduction responsivity and displacement sensitivities of the resonators Measurements and analyses show that the 100 nm AlN layer employed has an excellent piezoelectric coefficient, d_(31)=24 pm/V Doubly clamped AlN beams exhibit significant frequency tuning behavior with applied dc voltage

/pdf/piezoelectric-nanoelectromechanical-resonators-based-on-1zbory7dp3.pdf

Piezoelectric nanoelectromechanical resonators based on aluminum nitride thin films

Piezoelectric Actuators and Motors: Materials, Designs, and Applications

Pb(Zrx,Ti1−x)O3 thin films of homogeneous composition were synthesized by means of a modified sol-gel route on Pt(111)∕TiOx∕SiO2∕Si substrates The gradient in B-site composition as obtained by standard routes could be lowered, reducing Zr concentration fluctuations form ±12to±25at% The 2μm thick, dense and crack-free films exhibited a {100}-texture index of 984% Grain diameters increased by 50% Dielectric and piezoelectric properties were remarkably improved The relative dielectric constant e33,f was obtained as 1620, and the remanent transverse piezoelectric coefficient e31,f was measured as −177Cm2

Growth and properties of gradient free sol-gel lead zirconate titanate thin films

A silicon resonant torsional micro-mirror excited by piezoelectric bimorph actuators is presented. The bimorph actuators consist of a single-crystal silicon flexible beam or membrane and a PZT thin film. The mechanical elements are etched in the 20 μm thick superficial layer of a SOI substrate, thereby ensuring the flatness of the 500 μm-diameter gold-coated mirror. This device achieves optical beam scanning with large angular deflection at high frequency. In air, we have measured scanning up to 19.8° at 1.8 kHz, 99.1° at 10.6 kHz and 40.8° at 25.4 kHz. The applied driving voltage is sinusoidal with an amplitude under 42 V PP and with a 6 V DC bias voltage. At large oscillation amplitude, a non-linear hard-spring effect has been observed. In vacuum, a 78° optical scanning has been obtained with less than 1 V PP .

Resonant micro-mirror excited by a thin-film piezoelectric actuator for fast optical beam scanning

A wafer level package is produced by forming a photo definable polymer into a frame structure around a device located on a device wafer while maintaining the polymer in a partially cured state. Additional polymer material is used form a cap structure on a carrier wafer. The cap structure is attached to the frame structure so as to place the device within a cavity, wherein sufficient pressure is applied to the cap structure to hold the frame structure via a bonding of the partially cured photo definable polymers. The bonding is characterized by adhesion strength greater than the adhesion strength securing the cap structure to the carrier wafer. The carrier wafer is separated from the device wafer with a force sufficient for separating the carrier wafer from the cap structure while the cap structure remains attached to the frame structure.

Wafer Level Package and Manufacturing Method Using Photodefinable Polymer for Enclosing Acoustic Devices

Piezoelectric and ferroelectrics films are very promising materials for micro-actuators in MEMS applications. In this paper, we present the fabrication and characterization of silicon membranes actuated by thin piezoelectric films. The influence of the membrane length implementation has been carefully analysed. Si/SiO2/PZT square membranes have been elaborated by DRIE etching using a SOI wafer, and a sputtering process for PZT thin films has been specifically developed. We have investigated the dynamic and static behaviour of these Si/SiO2/Ti/Pt/PZT/Pt membranes. We have a good correlation between electrical and mechanical measurements in dynamic characterisations. Sputtered PZT on 4 in. wafers leads to high quality material well suited for large membrane deflection up to several microns. Detailed processing information is given.

Development and characterization of membranes actuated by a PZT thin film for MEMS applications

A modified free vibrating beam method has been developed in order to characterize the effective e31 piezoelectric transversal coefficient and the leakage resistance of piezoelectric thin films deposited onto a silicon beam. The main advantage of this method is that it requires no extra electrical measurements. Experiment was realized on lead zirconate titanate thin films.

Modified free vibrating beam method for characterization of effective e31 coefficient and leakage resistance of piezoelectric thin films

This work presents the elaboration and the characterization of PZT film bulk acoustic resonators Resonators are elaborated by deep reactive ion etching of silicon Resonators present quite small electromechanical characteristics (k/sub 33//sup 2/ and Q) Ferroelectric properties of the PZT thin film make possible the tuning of the frequency resonance Butterfly dependencies were both observed for series and parallel resonances

http://ieeexplore.ieee.org/iel5/9697/30606/01418330.pdf

Christophe Zinck

Papers

Resonant micro-mirror excited by a thin-film piezoelectric actuator for fast optical beam scanning

Wafer Level Package and Manufacturing Method Using Photodefinable Polymer for Enclosing Acoustic Devices

Development and characterization of membranes actuated by a PZT thin film for MEMS applications

Modified free vibrating beam method for characterization of effective e31 coefficient and leakage resistance of piezoelectric thin films

Design, integration and characterization of PZT tunable FBAR