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 describes logic and analog test schemes that improve the testability of a pixel-parallel fingerprint identification circuit. The pixel contains a processing circuit and a capacitive fingerprint sensor circuit. For the logic test, we propose a test method using a pseudo scan circuit to check the processing circuits of all pixels simultaneously. In the analog test, the sensor circuit employs dummy capacitance to mimic the state of a finger touching the chip. This enables an evaluation of the sensitivity of all sensor circuits on logical LSI tester without touching the chip with a finger. To check the effectiveness of the schemes, we applied them to a pixel array in a fingerprint identification LSI. The pseudo scan circuit achieved a 100% failure-detection rate for the processing circuit. The analog test determines that the sensitivities of the sensor circuit in all pixels are in the proper range. The results of the tests confirmed that the proposed schemes can completely detect defects in the circuits. Thus, the schemes will pave the way to logic and analog tests of chips integrating highly functional devices stacked on a LSI.

A historical overview of microoptomechatronics technologies is presented for positioning of microoptomechatronics, accompanied with a future view based on the current state of art nanotechnologies. How the technologies have been developed for realizing practical precision and information devices based on optics or photonics is also mentioned, citing a few examples.

Photonic crystal waveguide switches with movable micro-electro-mechanical actuators are proposed and fabricated by silicon micromachining. The switch structure consists of in-line input and output photonic crystal waveguide slabs, and a switching slab to bridge the gap between the waveguides. By driving the switching slab with a micro electro-mechanical actuator, the transmission between the waveguides is modulated. For driving the slabs, two kinds of actuator, i.e., vertical and parallel motion actuators are proposed for the respective switches. The switching characteristics are also investigated by calculations using the finite-difference time-domain method.

This paper presents the design, fabrication and characterization of a low actuation voltage capacitive shunt RF-MEMS switch for microwave and millimeter-wave applications based on a corrugated electrostatic actuated bridge suspended over a concave structure of coplanar waveguide (CPW), with sputtered nickel as the structural material for the bridge and gold for CPW line, fabricated on high-resistivity silicon (HRS) substrate using IC compatible processes for modular integration in a communication devices. The residual stress is very low because having both ends corrugated structure of the bridge in concave structure. The residual stress is calculated about 3-15 MPa in corrugated bridge and 30 MPa in flat bridge. The corrugated bridge of the concave structure requires lower actuation voltages 20-80 V than 50-100 V of the flat bridge of the planar structure in 0.3 to 1.0 µm thick Ni capacitive shunt RF-MEMS switch, in insertion loss 1.0 dB, return loss 12 dB, power loss 10 dB and isolation 28 dB from 0.5 up to 40 GHz. The residual stress of the bridge material and structure is critical to lower the actuation voltage.

RF system and circuit approaches for cognitive radios, based on software defined radio technology, are discussed. The increasing use of digital techniques, combined with wideband data converters and tunable front-end technologies, will enable these systems to become cost effective in the coming years.

Adaptive array antennas, which control their own patterns by means of feed-back or feed-forward control, are effective tools for gain enhancement and interference suppression. However, when applying them to mobile terminals, the problems of hardware complexity and power consumption need to be taken into consideration. One solution is the use of analog device-based adaptive array antennas, such as Reactively Steered Adaptive Array (RESAA) antennas and phased array antennas, which have the attractive characteristics of low cost and power consumption. In this paper, we propose an adaptive beamforming method based on a one-dimension search algorithm for phased array antennas with Micro Electro Mechanical Systems (MEMS) phase shifters, taking into consideration their slow operating speed due to mechanical structure of the devices. Furthermore, a smoothing processing is introduced to prevent the effect of noise and a multi-resolution alogrithm is proposed to help the system form beams more quickly and stably. Numerical results based on the IEEE 802.11a Wireless Local Area Network (WLAN) standard show that the proposed method has good interference suppression and gain enhancement capabilities in multipath fading channels.

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.

We proposed a new electric contact device that suppresses the arc phenomena. The functions of electric contacts are divided into energizing and switching for arc suppression. Switching contacts consist of multielectrodes and each electrode current is suppressed by the series resistance. For realization of multicontacting, cantilever beam array electrodes were formed on a silicon substrate using micro-electromechanical systems (MEMS) technology. The finite element method was used to optimize the structure. The fabrication process of the cantilever was examined. Au-Au contact current of 0.97 A was broken without arc ignition.

The relation between resonant frequency of micromirror with vertical combdrives and applied voltage between the upper and lower comb teeth was analyzed. Resonant frequency of the micromirror was controlled by stiffness of the torsion hinge. Resonant frequency of the mirror was proportional to the applied voltage between the upper and lower comb teeth at the same tilt angle.

The paper reviews methods for the measurement and analysis of high precision surfaces. A number of measurement techniques are discussed with the emphasis on the application of con-focal methods. The various techniques are compared in terms of measurement times, data density, and the ability to detect near vertical surfaces, and steps. The two sensing methods discussed are the auto-focus laser method and the white light methods. Particular applications considered are in the measurement of eroded electrical contact surfaces, spherical and near spherical surfaces, and MEMS. The particular emphasis here is on the metrology of such surfaces and devices and methods for the assessment of complex micro-machined surfaces. The paper points to a number of directions for improved metrology and discusses these in the context of the application given.

The lithography process on the deep trench pattern above the large cavity is proposed to fabricate the MEMS structure. Generally, bubbles generated on the trench patterns when it was baked after coating resist. The probability of the generation of bubbles was reduced by decreasing the backing rate. The fast scanning micromirror with 50.8 kHz resonant frequency was fabricated by controlling the backing rate.

A new concept of changing inductance values has been proposed, where a part of meander inductor is short circuited to reduce effective line length. Microwave characteristics of the short-circuited meander inductors and the meander inductor without the short circuit have been designed and fabricated on resin circuit boards. The reduction of inductance values by 40% has been successfully realized for the microwave frequency range from 0.5 GHz to 5 GHz for both designed and measured results. Using the proposed structure, low pass filters having two different cut-off frequencies have been designed and tested. Measured cut-off frequency changed 3.0 GHz to 4.2 GHz.

We have developed a novel self-alignment process using the surface tension of the liquid resin for assembly of electronic and optoelectronic devices. Due to their characteristics of low surface tension, however, the parametric design guidelines are necessary for resin self-alignment capability. In this paper, a shape prediction mathematical model and a numerical method are developed. The developed system is capable of achieving the liquid joint geometry and the parametric design for self-alignment capability. The influences of geometric parameters such as liquid volume, component weight, pad radius, liquid surface tension on the shape of liquid joint are investigated. Furthermore, the parametric design guidelines considered the process-related practical matters of misalignment level, distribution of the supplied liquid volumes and coplanarity deviation includes difference of the height between the pads are provided.

As new applications of THz waves emerge, new active and passive components need to be developed. The efficiency of wave guiding systems can be significantly increased with the use of MEMS approaches as well as with the development of new planar antenna concepts with high bunching properties. Generation of sufficient THz power relies on new active devices like Heterostructure Barrier Varactors and cascaded quantum structures, but also in the optimisation of new generation concepts. One of these is photomixing in non-linear materials with very short carrier lifetimes, like low-temperature-grown GaAs.

Some electromechanical devices and systems produced using MEMS fabrication processes are detailed. Two precision measurement metrologies for inspecting electromechanical products are also described. As the trend of electromechanical devices has been towards smaller and smaller sizes possessing robust mechanisms and powerful functions, micro-electric-mechanical system (MEMS) devices are becoming more the choice for meeting such requirements. Three MEMS examples are discussed in detail in this paper: CMOS compatible sensors, RF/microwave components, and packaged and integrated passive devices. The design thinking of a new free-fall sensor, which is an accelerometer and possesses a surprisingly low frequency response and broad bandwidth, is mentioned. In addition, an AVID (dvanced ibrometer/nterferometer evice) system for measuring tiny displacement as well as a Morphinscope system that has the advantage of a confocal microscope combined with a photon tunneling microscope and both developed by NTU's MEMS/NEMS group, are discussed. The excellent sensing ability of the free-fall sensor and the accuracy resolution of the two measurement systems are proved by experimental verification.

We propose a new scheme of indoor optical wireless LAN based on a special CMOS image sensor (CIS), which realizes a low-power compact communication module with large uplink capacity due to space division multiple access. In our scheme, all nodes and a hub utilize the CIS as a photoreceiver as well as a position-sensing device for finding the positions of the communication modules, while a single large photodiode is used in the conventional systems. Although conventional image sensors cannot detect modulated signals because they integrate photocurrents, our CIS has a high-speed readout function for receiving optical data from the specific pixels receiving optical signals. The advantages of the proposed scheme are 1) compact embodiment of the communication module due to no need of the bulky mechanical components for searching the other modules, 2) space division multiple access, which leads to 3) large capacity of uplink, and 4) applicability of simple modulation and coding schemes for optical signals. In our scheme, diffusive and narrow beam lights are complementally used for position detection and communication, respectively, which leads to the advantage 5) low power consumption of both light emitter and receiver circuits. To demonstrate two basic functional modes of our CIS: an IS (image sensor) mode and a COM (communication) mode, we fabricate an 88-pixel CIS by use of a 0.8µm BiCMOS technology. In the experiments, the image of a light source is successfully captured in the IS mode for integration time of 29.6msec and optical power of 1.1nW. After the functional mode of the pixel receiving the light is changed to the COM mode, the eye pattern of the modulated light is obtained from the pixel at frequency of 1MHz. We also fabricate a test pixel circuit with in-pixel amplifier, with which operation speed is improved to 100MHz.

We describe in this paper our experience of developing a large-scale, highly distributed multi-agent system using wireless-networked sensors. We provide solutions to the problems of localization (position estimation) and dynamic, real-time mobile object tracking, which we call PET problems for short, using wireless sensor networks. We propose system architectures and a set of distributed algorithms for organizing and scheduling cooperative computation in distributed environments, as well as distributed algorithms for localization and real-time object tracking. Based on these distributed algorithms, we develop and implement a hardware system and software simulator for the PET problems. Finally, we present some experimental results on distance measurement accuracy using radio signal strengths of the wireless sensors and discuss future work.

Recently the applications of MEMS (micro electro mechanical systems) have made remarkable progress in many filelds. The optical application of MEMS is one of the most promising because it provides micro mechano optical devices, the key components for high-perfromance systems in optical communication networks and data storage devices. This paper disucces the impacts of MEMS techologies on optical systems. Furthermore, state-of-the-art exmaples of micro optical switches, pig-tailed tunable filters and two-dimensional MEMS optical scanners are described.

We report on a novel micromechanical photonic integrated circuits (PIC) for integrating free-space optical systems on a chip. Using polysilicon surface-micromachining technique, micro-optical elements, three-dimensional optomechanical structures, and microactuators are monolithically integrated on silicon substrate. We will discuss the basic building blocks of the micromechanical PIC, including XYZ micropositioners, 2-axis tilting micromirrors, scanning microlenses, and their integration with vertical cavity surface-emitting lasers. We will also discuss their applications in reconfigurable optical interconnect and active alignment in parallel free-space optical interconnect systems.