This study is to develop the manufacturing processes of thin film bulk acoustic device by MEMS technology, including lithography, wet etching, dry etching and rf Magnetron sputtering.LPCVD is used to deposit SiNx as the membranes and mask for etching of silicon wafer. The electrodes of molybdenum metal (Mo) and piezoelectric layer of aluminum nitride (AlN) on top side are prepared by dc and rf sputtering,respectively. The acoustic cavity on back side is achieved by 30%wt 100¢J KOH solution and reactive ion etching (RIE). In this study, the crystallography of the coated films was analyzed by X-ray diffraction. The surface and cross-sectional morphologies of AlN films were investigated by electron microscope. The piezoelectric layer of AlN thin film prepared by rf magnetron sputtering shows the highly c-axis preferred orientation and fine morphology under the optimal sputtering parameters of rf power of 200W, sputtering pressure of 3 mTorr, substrate temperature of 400¢J and nitrogen concentration of 25%. The frequency responses of fabricated FBAR devices are evaluated using the Hewlett-Packard 8720-ET network analyzer. Moreover, the optimal thickness of 1500Å SiNx film prepared by LPCVD revealed the excellent masking effect and non-stress for membrane. The yield for the fabrication of acoustic cavity is maximum of 85% can be achieved by using the combined etching steps of wet and dry etching.

The conventional techniques of manufacturing large-size structures in a very large plate pose severe challenges in making microstructures. In contrast, semiconductor process that employs lithographic processes to form micro scale features is limited in its wafer size. In ordre to modify the defeat of shadow mask. This thesis propose to use TMAH anisotropic wet etching process and 2D- joining technique to fabricate silicon shadow mask. The potential of this technique would be significant for a very large plate beyond a wafer size with microstructures, and provides a new approach with a high replication and potentially low cost. In the numerical analysis, this study uses the finite element software, ANSYS, to simulate shadow mask with different size, material, and temperature displacement situation. The results shows the feasibility of silicon shadow mask used in the thermal evaporation process. It indicates that this design could have smoother pattern and reduce the limitation of Organic Light-Emitting Diode resolution.

Zugl.: Wien, Techn. Univ., Diss., 2009

A microelectromechanical systems (MEMS) optical microphone that measures the interference of light resulting from its passage through a diffraction grating and reflection from a vibrating diaphragm (JASA, v. 122, no. 4, 2007) is described. In the present embodiment, both the diffractive optical element and the sensing diaphragm are micromachined on silicon. Additional system components include a semiconductor laser, photodiodes, and required readout electronics. Advantages of this optical detection technique have been demonstrated with both omni-directional microphones and biologically inspired directional microphones. In efforts to commercialize this technology for hearing-aids and other applications, a goal has been set to achieve a microphone contained in a small surface mount package (occupying 2mm x 2mm x 1mm volume), with ultra-low noise (20 dBA), and broad frequency response (20Hz–20kHz). Such a microphone would be consistent in size with the smallest MEMS microphones available today, but would have noise performance characteristic of professional-audio microphones significantly larger in size and more expensive to produce. This paper will present several unique challenges in our effort to develop the first surface mount packaged optical MEMS microphone. The package must accommodate both optical and acoustical design considerations. Dynamic models used for simulating frequency response and noise spectra of fully packaged microphones are presented and compared with measurements performed on prototypes. / text

MEMS technology is a growing field that requires more automative tools to lower the cost of production. Current industry standards of tele-operated 3D manipulated MEMS parts to create new devices are labor intensive and expensive process. Using computer vision as a main feedback tool to recognize parts on chip, it is possible to program a close loop system to instruct a computer to pick and assemble parts on the chip without the aid of a user. To make this process a viable means, new chip designs, robotic systems and computer vision algorithms working along side with motion controllers have to be developed. / Graduate / 0548 / 0544 / 0771 / hsukardi@uvic.ca

Capacitive micromachined ultrasonic transducers (CMUTs) have proven themselves to be excellent candidates for medical ultrasonic imaging applications. The use of semiconductor fabrication techniques facilitates the fabrication of high quality arrays of uniform cells and elements, broad acoustic bandwidth, the potential to integrate the transducers with the necessary electronics, and the opportunity to exploit the benefits of batch fabrication. In this thesis, the design, fabrication and testing of one- and two-dimensional CMUT arrays using a novel wafer bonding process whereby the membrane and the insulation layer are both silicon nitride is reported. A user-grown insulating membrane layer avoids the need for expensive SOI wafers, permits optimization of the electrode size, and allows more freedom in selecting the membrane thickness, while also enjoying the benefits of wafer bonding fabrication. Using a row-column addressing scheme for an NxN two-dimensional array permits three-dimensional imaging with a large reduction in the complexity of the array when compared to a conventional 2D array with connections to all N2 elements. Only 2N connections are required and the image acquisition rate has the potential to be greatly increased. A simplification of the device at the imaging end will facilitate the integration of a three-dimensional imaging CMUT array into either an endoscope or catheter which is the ultimate purpose of this research project. To date, many sizes of transducers which operate at different frequencies have been successfully fabricated. Initial characterization in terms of resonant frequency and, transmission and reception in immersion has been performed on most of the device types. Extensive characterization has been performed with a linear 32 element array transducer and a 32x32 element row-column transducer. Two- and three-dimensional phased array imaging has been demonstrated.

No description available.

A delay line phase shifter for the 30-70 GHz range is presented that uses an aluminum micro-ribbon array fabricated in the ground plane of a microstrip transmission line. Phase shift is achieved by changing the propagation velocity of an RF signal in the transmission line by controlling the effective permittivity of the substrate. This is done by actuating the micro-ribbons away from the substrate. This phase shifter has the benefits of analog phase shifts and high Figure of Merit. Simulations were done to model the micro-ribbon deflections, transmission line performance and phase shift. Arrays of 5, 10, and 20 μm wide micro-ribbons were fabricated and tested. At 40.80 GHz, the 20 μm wide micro-ribbons had a measured phase shift of 33º with an actuation voltage of 120 V. The corresponding Figure of Merit was a negative value indicating that there was no line loss due to ribbon deflection.

A frequency selective surface (FSS) based on switchable slots in the ground plane is presented. The switching is done using an actuating MEMS bridge over the slot. The intent is to demonstrate the control of the resonance frequency of the FSS by deflecting the bridge. It is shown that by applying a voltage between the bridge and the ground plane, the bridge displaces and changes the system capacitance which in turn changes the resonance frequency. Two analyses are presented; (1) Electromechanical analysis to show how the bridge deflects by the voltage, (2) Electromagnetic analysis to show how the resonance frequency changes by the bridge deflection. The device was fabricated and tested. The measurement results are presented for two up and down positions of the MEMS bridge to verify the correctness of the theory and design.

The Kelvin Probe Force Microscope is a type of scanning probe instrument that is used to discern the different work functions of a sample. A sharp probe at the end of a cantilever is lowered onto a substrate where electrostatic forces, caused by the difference in work function cause the cantilever to oscillate at the modulated frequency. Using this instrument, high resolution images can be obtained, mapping the surface electronic characteristics. However, developments of this instrument have generally been limited to obtaining higher resolution images as well as reducing noise in the output, limiting the widespread appeal of this expensive instrument. There exist many applications where extremely cheap, low footprint and easy-to-use Kelvin Probe Force Microscopes would be beneficial. In order to cheaply produce this microscope in batch, a post-processed CMOS-MEMS device is utilized. The polysilicon resistors act as a strain gauge such that a conventional optical system will not have to be employed. The ability to use integrated bimorph actuators on chip allow for movement of the cantilever without the employment of large piezoelectric stages with creep effects. Embedded electronics can be fabricated with the CMOS process alongside the MEMS device, allowing full integration of an on board amplifier and read out system. In general, a large table top system can be minimized onto the size of a <1 mm2 area, a microcontroller and a computer. In this work, a Kelvin Probe Force Microscope is designed, fabricated and validated. A MEMS device was designed following similar characteristics of a generic cantilever beam. The stiffness, length, resonant frequency, and other tip characteristics can be mimicked with careful design. The resultant designs were fabricated using a CMOS-MEMS process. In order to obtain a sharper tip with modified characteristics, various methods were employed; such as gallium-aluminum alloy tip formation as well as electroless plating onto the tip of the device. Finally, the resultant device is tested against a sample. It was seen that the MEMS device followed similar characteristics of the conventional microscope itself, validating the equations that define the method. Bimorph actuators were tested to show movement, allowing the integration of the cantilever with the XYZ-stage. Work function changes are observed while scanning different materials. It is shown throughout the course of this thesis, that a true Kelvin Probe Force Microscope can be designed, fabricated and validated using CMOS-MEMS technology.