Masashi Takeuchi

Static Characteristics of Piezoelectric Thin Film Buckling Actuator

We have developed a diaphragm piezoelectric microactuator. The diaphragm consists of a Pb(Zr, Ti)O3 (PZT) thin film, electrode layers, an isolation layer and a Si substrate. The diaphragm is deflected by transverse stress in the PZT thin film which is fabricated by a sputtering and annealing process. The PZT thin film has a piezoelectric coefficient d31 of -100 pC/N, which is comparable to that of bulk PZT. A diaphragm deflection of 3 µ m was obtained at an electric field of 16 V/µm.

Sputtered high |d/sub 31/| coefficient PZT thin film for microactuators

High |d/sub 31/| coefficient PZT thin film for Si-based microactuators has been developed. Piezoelectric coefficient d/sub 31/ of around -100 pC/N was obtained and it is comparable to that of thick film or bulk PZT. The film was deposited on Pt/Ti/LTO/Si substrate by magnetron sputtering and annealed for obtaining perovskite structure. It was made clear that a <111> strongly oriented film has a higher |d/sub 31/| coefficient. Crystal orientation preference was controlled by ramp rate at post anneal process. Built-in stress and Youngs modulus of PZT thin film have also been evaluated. It was shown that post anneal process significantly increases both mechanical characteristics. 10 minutes-annealed PZT thin film which has d/sub 31/ of -100 pC/N has a built-in stress of 380 MPa and a Youngs modulus of 75 GPa.

Pb-based ferroelectric thin film actuator for optical applications

Novel PZT thin film actuators for optical applications were proposed. Key issues for realizing the actuators such as PZT thin film processes, mechanical properties evaluation of thin films, and design for laminated structure were described. [1 1 1]-oriented PZT films were obtained by anneal/non-anneal sputtering process. Also for PZT dry etching, it was made clear low pressure and low temperature conditions were advantageous for high selectivity and etch rate. ECR etcher was used and etch rate of 1000 A/min and selectivity of 0.56 to photoresist mask were obtained. Young’s modulus and built-in stress of PZT film, measured by load-deflection method, were 72 GPa, −335 MPa respectively. Using these results, calculated deflection of each actuator was on the order of a few microns to 20 microns. It was confirmed that deflection of actuators would be enough for the application.

An image processing method to detect road surface condition using optical spatial frequency

A road surface recognition method at fixed positions on the road is presented, with which a light source and a CCD camera are employed. The method has a certain optical configuration and two factors: road gloss and spatial frequency spectra of the road surface. Experimental results show that the road surface conditions that were expected to be discriminated in cold districts were recognized. Therefore, the method should be very useful for a traffic information system.

Liquid Phase Epitaxial Growth of lnGaAsP on GaAs1-yPy Substrates (y=0.31 and 0.39)

Lattice matched InGaAsP mixed crystals with various energy bandgaps were grown by liquid phase epitaxy (LPE) on GaAs1-yPy substrates (y=0.31 and 0.39). The growth layers had smooth and shiny surfaces with undulated morphology reflecting the cross-hatching pattern of GaAsP substrates. The influences of offset angle and crystal composition of the InGaAsP growth layer on the surface morphology of the InGaAsP growth layer were investigated. The offset angle was not the main cause of the undulated morphology in our experiments. Photoluminescence spectra and X-ray rocking curves of the growth layers were measured in order to determine their energy bandgaps and lattice constants. The doping characteristics of zinc and tellurium were also investigated. The growth conditions and properties of the InGaAsP layers on GaAsP substrates are described in detail.

Two-dimensional silicon micromachined optical scanner integrated with a photodetector

A highly miniaturized optical scanner integrated with a photo detector has been developed for miniaturization of scanning type of optical sensors. The scanner is fabricated by silicon micromachining technologies and is driven by a piezoelectric actuator. It is capable of two dimensional scanning and photo detection. The scanning angle is over 40 deg X 30 deg and the photo detecting sensitivity is 0.49 A/W for 680 nm wavelength light.

Nitrogen Profile Study for SiON Gate Dielectrics of Advanced Dynamic Random Access Memory

Nitrogen profile variations were systematically studied for the plasma nitridation process of the dynamic random access memory (DRAM) gate dielectrics, using angle-resolved X-ray photoelectron spectroscopy (AR-XPS), and their influences to the boron blocking and the device performances including negative bias temperature instability (NBTI) were investigated. Nitrogen atoms incorporated are localized in the surface vicinity within 1.5 nm of the thickness and at the peak positions around 0.5 nm. The high pressure and high temperature conditions of plasma nitridation are preferred for improving the NBTI and the tool productivity. Post nitridation anneal stabilizes the nitrogen atoms incorporated, and improves the immunity against the boron penetration into the gate dielectrics. Both of re-oxidation and the out-diffusion of nitrogen atoms take place simultaneously near the surface during the queue time after the plasma nitridation. Microwave plasma with the radial line slot antenna (RLSA) is a successful SiON gate insulator formation technology in the manufacturing of DRAM as well as logic devices.

CW Lasing Characteristics of Visible InGaAsP Lasers Grown on GaAsP Substrates

Continuous wave operation of visible-light emitting InGaAsP injection lasers grown on GaAs0.61P0.39 substrates by liquid phase epitaxy was obtained in the temperature range of 98?197 K. Their lasing wavelength was 630 nm at 197 K. The characteristic temperature T0 was estimated to be 58 K.

Basic Characteristics Of A Piezoelectric Buckling Type Of Actuator

An actuator which utilizes buckling motion due to piezoelectric transverse stress is present. It will be a key part of Micro Focusing Device(MFD) which changes focal length of light from a light source. Sputtered PZT(Pb(Zr/sub x/ Ti/sub 1-x/)O3:x=0.54) was used as piezoelectric material and piezoelectric coefficient(d/sub 31/) of 45 pC/N was obtained. It was confirmed that the actuator can produce enough deflection for MFD application by non-linear elastic theory calculation with thin film mechanical characteristics and d/sub 31/ data.

Study on mechanical characteristics of PZT thin film for sensors and actuators

Piezoelectric thin films are very promising materials for MEMS applications because they have application flexibility and compatibility with semiconductor and micromachining processes. How to design MEMS devices with piezoelectric thin films, the mechanical characteristics, and how those characteristics can be controlled by process conditions is discussed in this paper. In addition, piezoelectric/electric characteristics must be understood. With this background, mechanical characteristics (Youngs modulus and built-in stress) measurements of sputtered Pb(Zrx, Ti1 - x) O3 thin film, one of piezoelectric materials, have been carried out using the load-deflection method. Relationships between post anneal conditions and those characteristics are discussed. It was shown from the experiment results that Youngs modulus increases as anneal temperature/time increases. The maximum value was 76.6 GPa(700 degrees C/3600 sec) which is more than three times larger than that of as-depo film. Built-in stress is also affected by post anneal process and ranges from 0.04 GPa(as-depo) to 0.41 GPa(700 degrees C/60 sec). SEM observation results made it clear that it was caused by film shrinkage due to grain enlargement during anneal process.