A 76-GHz Gunn voltage-controlled oscillator (VCO) with a high output power and a wide tuning-frequency range was fabricated by optimizing VCO circuits and using laser micromachining. The tuning-frequency range of the fabricated Gunn VCO was more than two times higher than that attained in our previous experiments by optimizing VCO circuits. The VCO attained a tuning-frequency range of 493 MHz, output power variation of 1.0 dB, and tuning-frequency linearity of 6.1% over a tuning-voltage range from 0 to 10 V. Its power consumption was 2.0 W at operation voltage of 3.6 V. And it measured output power was 13.3 dBm with DC-RF conversion efficiency of 1.0% at 76.5 GHz. Moreover, under fundamental-mode operation, it achieved low phase noise of -107.8 dBc/Hz at an offset frequency of 1 MHz. Since laser micromachining was used in fabricating the Gunn VCO, the reproducibility of its RF performance was improved.

This letter reports a high-performance Ka-band equilateral triangular microstrip patch (ETMP) antenna suspended on a thin dielectric membrane. The membrane is released using a silicon bulk-micromachining technique. A set of closed-form expressions to calculate the resonant frequency of the proposed antenna on the micromachined substrate is also presented. The measured performance of the antenna structure is verified using the finite element method (FEM) based Agilent High Frequency Structure Simulator (version 5.5). The fabricated antenna exhibited a wide -10 dB return loss bandwidth of 1.2 GHz at 35.4 GHz. The measured antenna cross-polarization level is less than -15 dB in both the E- and H-planes.

An ultra-deep polymer cavity structure exposed using deep X-ray lithography is used as a template for metal electroforming to produce a 24-GHz cavity resonator. The metal cavity is 1.8 mm deep and has impressive structure, including extremely vertical and smooth sidewalls, resulting in low conductor loss. The measured resonator has an unloaded quality factor of above 1800 at a resonant frequency of 23.89 GHz.

This paper presents high-performance millimeter-wave passive devices using MEMS technology. The purpose of this paper is to show the possibility of MEMS technology as an enabling technology for millimeter-waves. The loss and cost issues, which have been the inherent barrier for commercialization of mm-waves, can be solved by RF MEMS technology. Successful demonstrations of MEMS technology for mm-waves include novel CPW transmission lines, digital impedance tuners, analog tunable band-pass filters, reconfigurable low-pass filters, V-band digital distributed phase shifters and 2-D mechanical beam-steering antennas. All these circuits were implemented for 30-65 GHz frequency range, and show the state-of-the-art performance, which is beyond the limit set by the conventional technology.

A fully integrated broadband distributed frequency tripler, periodically loaded with HBV devices, has been designed and fabricated and has demonstrated the generation of a broad range of output frequencies of up to 570 GHz. Key to the design is the principle that the entire frequency tripler circuit is produced monolithically and incorporates novel HBV devices electrically and mechanically interconnected by a thin low-loss SU-8 membrane. With the device fabrication approach used, the novel HBV devices are able to produce a higher capacitance-voltage swing ratio whilst simultaneously minimizing the device series and contact resistances to achieve the optimum conversion efficiency. The entire concept of this work was to design a cost effective fully integrated waveguide package, with the frequency tripler circuit mounted at the E-plane of a micromachined waveguide which was constructed with stepped height and width to prevent the propagation of higher order modes inside the waveguide sections. The micromachined waveguide sections exhibit high dimensional accuracy and a good surface finish which is necessary for the efficient propagation of high frequency signals. The frequency tripler circuit and the accompanying micromachined waveguide sections are mounted in a specifically designed metal test fixture to form a compact and cost-effective subcomponent with great commercial potential for broadband harmonic generation of up to terahertz frequencies. This paper presents the design methodology and techniques used to produce the frequency tripler package, together with some initial measurement results.

This paper presents a high resolution long array thermal ink jet (TIJ) printhead which has been developed and demonstrated to operate successfully by combining two functional Si wafers, a bubble generating heater plate fabricated using LSI process and a channel plate fabricated using Si bulk micromachining technology. The heater plate consists of logic LSIs, high voltage MOS transistor, polycrystalline Si (Poly Si) heating resistor and polyimide protective layer. The polymide layer is patterned by O2 plasma reactive ion etching (RIE) and is applicable to high resolution heater array. The Si channel plate consists of an ink chamber and an ink inlet formed by KOH etching, and a nozzle formed by inductively coupled plasma RIE (ICP RIE). The nozzle formed by RIE has squeezed structures which contribute to high energy efficiency of drop ejector and therefore successful ejection of small ink drop. These two wafers are directly bonded by using a novel electrostatic bonding of full-cured polyimide to Si. The adhesive-less bonding provided an ideal shaped small nozzle orifice. And also, the bonding method enabled to use an on-chip LSI wafer because of the contamination free material and the suitable processing conditions (low temperature). The bonded wafer is diced to form printhead chip. No delamination or displacement of the chip was observed even though the chip was subjected to thermal stress during assembly process. This is because of no difference in thermal expansion coefficient between both chips (Si and Si). And therefore it is suitable for long chip concept. With the above technologies, we have fabricated a 1.3" long printhead with 1024 nozzles having a 800 dots per inch (dpi) resolution, a 2.7 pl. ink drop volume, 14 m/sec. ink drop velocity and 18 kHz jetting frequency. And we have confirmed high speed printing and high quality printing.

Fiber-optic MEMS which is fabricated by combining direct photo-lithography of optical fiber and silicon micro-machining is proposed. Preliminary results of micro-machining of optical fiber and variable telecommunication devices are presented.

We propose a three-dimensional structure on a planar substrate employing micromachining technology. A low-loss suspended structure incorporating a BCB membrane employing deep trench etching technology has been newly proposed. A micromachined suspended line structure using BCB membrane film enables us to realize a low loss planar resonator, which achieved an unloaded quality factor (Q-factor) of more than 280 at 60 GHz. We design low-loss filters and antennas built into silicon in a 60 GHz band. A low-loss filter realizes an insertion loss of 1.0 dB at 60 GHz and a patch antenna obtains a 3% bandwidth. In addition, we demonstrate a 60 GHz receiver front-end IC incorporating the planar filter and the antenna, and obtain good results. These techniques enable us to integrate various functions into a compact package even in millimeter-wave bands.

A novel temperature insensitive wavelength filter consisting of GaAlAs/GaAs distributed Bragg reflectors (DBRs) has been demonstrated. This micromachined DBR is mechanically tuned by differential thermal expansion. The strain-induced displacement of one mirror can generate wavelength tuning and trimming functions with an adjustable temperature dependence. We succeeded in the control of temperature dependence in this micromachined semiconductor filter by properly designing a vertical cavity structure. The achieved temperature dependence was as small as +0.01 nm/K, which is one-tenth of that of conventional semiconductor based optical filters. Also, a wavelength trimming of over 20 nm was demonstrated after completing the device fabrication. In addition, we demonstrated a 4 4 multiple wavelength micromachined vertical cavity filter array. The multi-wavelength filter array with a wavelength span of 45 nm was fabricated by partially etching off a GaAs wavelength control layer loaded on the top surface of device.

A novel temperature insensitive wavelength filter consisting of GaAlAs/GaAs distributed Bragg reflectors (DBRs) has been demonstrated. This micromachined DBR is mechanically tuned by differential thermal expansion. The strain-induced displacement of one mirror can generate wavelength tuning and trimming functions with an adjustable temperature dependence. We succeeded in the control of temperature dependence in this micromachined semiconductor filter by properly designing a vertical cavity structure. The achieved temperature dependence was as small as +0.01 nm/K, which is one-tenth of that of conventional semiconductor based optical filters. Also, a wavelength trimming of over 20 nm was demonstrated after completing the device fabrication. In addition, we demonstrated a 4 4 multiple wavelength micromachined vertical cavity filter array. The multi-wavelength filter array with a wavelength span of 45 nm was fabricated by partially etching off a GaAs wavelength control layer loaded on the top surface of device.

A tunable optical Fabry-Perrot filter was designed by setting a single-mode optical fiber normal to the diaphragm of a capacitive pressure sensor. The silicon diaphragm is deflected by the electrostatic force generated by applying a voltage to the capacitive electrodes. According to the movement of the diaphragm, the peak wavelength changed from 1546 to 1551 nm when applied voltage was increased from 20 to 50 V. The relationship of the wavelength change to the applied voltage was derived from the silicon diaphragm deflection theory. That measured change of the wavelength agrees well with the wavelength change calculated from this relationship. The commercial pressure sensors are expected to be able to be used as a tunable optical filter.

A new silicon capacitive pressure sensor with center clamped diaphragm is presented. The sensor has a silicon-glass structure and is fabricated by batch-fabrication processes. Since deformed diaphragm has a doughnut-shape, parallel-like displacement is realized and therefore better linearity of 0.7% which is half of the conventional flat diaphragm sensor is obtained. It is clarified both analytically and experimentally that the capacitive pressure sensor with center clamped diaphragm is advantageous in terms of linearity.

The growing availability of commercial foundry processes allows easy implementation of micro-opto-electro-mechanical systems (MOEMS) for a variety of applications. Such applications go beyond single devices to include whole optical systems on a chip, consisting of mirrors, gratings, Fresnel lenses and shutters, for example. Hinged and rotating structures, combined with powerful and compact thermal actuators, provide the means for positioning and operating these optical components. This paper presents examples of such systems built in a commercial polycrystalline silicon surface-micromachining process, the ARPA-sponsored Multi-User MEMS ProcesS (MUMPS). Examples range from optical sub-components to large mirror arrays, communication components, and micro-interferometers. Using the examples discussed in this paper, a designer can take advantage of commercially available surface-micromachining processes to design and develop MOEMS without the need for extensive in-house micromachining capabilities.

This paper describes the fabrication of micro-pipes and their applications to splicing parts and optical switches using single-mode fibers. Micro-pipes having almost the same inner diameter of bare fiber (125 µm) and lengths of around 5 mm are successfully mass-produced by using micromachining technology. We fabricate various kinds of metal pipes such as Au, Cu, Ni, and an FeNi alloy by selecting the appropriate electro-plating bath. We use an Au micro-pipe having a small slitted portion running along its axis (slitted micro-pipe) to splice single-mode fibers. We also use an FeNi alloy micro-pipe to construct a single-mode fiber switch. These new single-mode fiber devices employing micro-pipes show excellent optical and mechanical characteristics. Splicing losses are in the range of 0.2-0.4 dB. The developed 1 2 latching type single-mode fiber switches exhibit a low insertion loss of 0.35 dB, a minimum switching speed of 2 ms with a driving power of 9 mW, and stable operation for more than 108 switchings without damage. A practical application of the developed switch for testing optical devices is also demonstrated.

GaAs-based micromachining is a very attractive technique for integrating mechanical structures and active optical devices, such as laser diodes and photodiodes. For monolithically integrating mechanical parts onto laser diode wafers, the micromachining technique must be compatible with the laser diode fabrication process. Our micromachining technique features three major processes: epitaxitial growth (MOVPE) for both the structural and sacrificial layers, reactive dry-etching by chlorine for high-aspect, three-dimensional structures, and selective wet-etching by peroxide/ammonium hydroxide solution to release the moving parts. These processes are compatible with laser fabrication, so a cantilever beam structure can be fabricated at the same time as a laser diode structure. Furthermore, a single-crystal epitaxial layer has little residual stress, so precise microstructures can be obtained without significant deformation. We fabricated a microbeam resonator sensor composed of two laser diodes, a photodiode, and a micro-cantilever beam with an area of 400700 µm. The cantilever beam is 3 µm wide, 5 µm high, and either 110µm long for a 200-kHz resonant frequency or 50 µm long for a 1-MHz resonant frequency. The cantilever beam is excited by an intensity-modulated laser beam from an integrated excitation laser diode; the vibration signal is detected by a coupled cavity laser diode and a photodiode.