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A novel self-aligned vertical electrostatic combdrives actuator has been developed and demonstrated, which enhances the capabilities and applications of high aspect ratio silicon-on-insulator microelectromechanical systems (SOI-MEMS) by enabling additional independent degrees of freedom of operation: both upward and downward vertical pistoning motion as well as bi-directional rotation. The present method utilizes four aligned masks greatly simplifying the existing SOI-MEMS fabrication methods for manufacturing high performance scanning micromirrors. Results from the micromirror device for the novel vertical combdrives show that a mechanical tilt angle of ±1° at 100 Vdc was achieved for a 450 µm diameter micromirror. The scanning micromirror can scan a large angle 62° at the resonance frequency of 10.46 kHz with a sinusoidal voltage input of 60 V in amplitude.

The implementation of differential Pirani gauge for accurately measuring wafer-level package pressures was demonstrated. We proposed a multiple-sensor-solution, where two Pirani gauges were constructed under different pressures; one in sealed micro-cavity for measuring pressures and the other one in opened micro-cavity as a reference. Ambient pressure, structural dimension variations, and resistivity differences among wafers/lots, were captured through the differential scheme for error compensations, allowing accurate pressure determinations. Presented Pirani utilized small gaps (∼2µm) between heater and dual heat sinks to obtain wide operation range (0.05∼100 Torr) and high sensitivity (∼10000 ppm/Torr). With 5X error reductions and high stabilities, the proposed device was successfully used in examining reliabilities and monitoring processes of wafer-level packages.

The undercut process of the micromachined structures on a (1 1 1) oriented silicon wafer is studied in this paper. As observed in the experiment, the undercut of a cantilever on (1 1 1) wafer is along the width of the beam. According to the undercut mechanism, the advantages of fabricating a cantilever on (1 1 1) wafer are three-fold: (1) significantly reduce the etching time and obtain an ideal clamped boundary in the mean time; (2) the thickness as well as the moment of inertia of the cantilever is closer to the ideal case; (3) the flexural rigidity of the cantilever is constant along the beam axis. Consequently, the micromachined cantilever on a (1 1 1) wafer is more appropriate in various applications. For instance, it is more appropriate to fabricate the diagnostic microstructures on the (1 1 1) wafer than on the (1 0 0) wafer in determining the thin film residual stress.

Micromachining on (111)-oriented silicon in various alkaline solutions was studied. By means of spoke and donut-like etching patterns, the experiment shows that 〈110〉 directions have the highest etch rate and the final emergent periphery is hexagon bounded on the bottom surface plane. The six sidewalls are defined by {111} planes, which can be derived from its crystal geometry, having three facets with inclining angles of 70.5° and another three with declining angles of 109.5° respect to the (111) surface plane. SEM pictures show that aqueous KOH solution results in smooth surface morphology due to its higher etch rate of residual oxide existed in the silicon, while the other etchants such as hydrazine (N2H4) and tetramethyl ammonium hydroxide (TMAH) induce seriously wavy roughness. Moreover, various concentrations of KOH solution have been studied to determine the (110)/(111) etch ratio, and the ratio more than 100 were demonstrated. Using this method, suspended single-crystal silicon (c-Si) microstructures were fabricated for some potential uses such as thermopile, silicon bolometer, mass flow transducer and other force microsensors. As an application example, shallow-gap μ-Pirani vacuum sensor demonstrated its high pressure measuring capability as high as 103 Torr.

A sensitive micro-Pirani vacuum sensor has been fabricated. With effective schemes of ambient-temperature compensation and stabilization, it is capable of measuring vacuum pressure linearly from 1 torr down to 10 −7 torr, a three orders-of-magnitude improvement in resolution over conventional gauges. A special electrothermal SPICE model, complementary to the conventional analog representation of thermal parameters, is also proposed. It allows a high-level sensor-circuit integrated simulation based on the most fundamental principle and thermal variables. Good agreement between the measured data obtained from a constant-temperature readout circuit and the simulation result is demonstrated.

The characteristic thermal parameters of a platinum-film microbolometer are extracted from the data of two measuring methods. A simple and accurate equivalent circuit model, along with its thermal behavior, is proposed for the device. Applying the model to simulate some device circuits results in good agreement with the experimental data. Furthermore, an effective method of ambient temperature compensation, proposed previously by our laboratory, is demonstrated both experimentally and by simulation using the same model. The established electro-thermal model therefore serves as an useful tool for SPICE simulations in the design of microbolometers.

As an extension of previous work in our laboratory, a wide‐range Pirani gauge that is capable of measuring vacuum pressure down to 10−7 Torr reproducibly has been built. The micromachined Pirani sensor used in the experiments has a suspended membrane that is supported by the nearly radiation‐limited, thermally insulating beam leads crossing over a V‐groove cavity. A method of partial dummy compensation, as proposed previously by Weng and Shie for eliminating the ambient drift, is proved here to be very effective with a thermal drift as small as only 5.7 μV/°C. It has also been found that a thermal‐stress‐induced piezoresistive effect, which has a profound influence on the limitation of measurement, appears in the constant‐bias operation wherein the sensor temperature rises with the reduction of gas pressure and therefore thermal conduction. This effect causes the irreproducibility of pressure measurements by the device below 10−5 Torr. In addition to its inherently higher sensitivity, a constant‐temperatu...

MEMS technology development and MEMS manufacturing activities at TSMC are presented. Two models for process development, i.e. customer product/process “phase-in” and internally developed “platform” are discussed. The latter is a TSMC-MEMS platform for motion sensors and other devices.

A method of fabricating low-stress dielectric thin film as the supporting material of micromachined devices is reported. The film is processed by post thermal oxidation of silicon-rich nitride (SN) deposited on a silicon substrate by LPCVD. Due to the compensation on the nitride by its top oxide, an ultra-low residual stress less than 10 MPa can be obtained with a proper oxidation scheme. Characteristics of the oxidized nitride were analyzed by Auger electron spectroscopy (AES) and ellipsometry. Large floating membranes of 4/spl times/4 cm/sup 2/ and 400-nm thick can be made by this method with TMAH etching.

A novel micromachined accelerometer based on thermal-bubble technology is proposed and demonstrated in this work. Unlike the other techniques, the only moving element in the accelerometer is a small thermal-bubble created by using a high flux heater to vaporize the liquid contained in the micro-chamber. The basic physical characteristics including the heat transfer and fluid flow behavior of this sensor have been analyzed and discussed. The feasibility and performance of the proposed accelerometer are verified using numerical simulations and demonstrated experimentally using a designed test setup. The results conclude that the presented design has better response and higher sensitivity comparing to its counterparts.

In this study, a novel thermal-bubble-based micromachined accelerometer with advantages of no proof mass, preferable frequency response, and high sensitivity is presented. Unlike the other techniques, the only moving element in the proposed device is a small thermal-bubble created by using a high flux heater to vaporize the liquid contained in the micro chamber. In order to improve the performance of the accelerometer, the basic physical characteristics of this sensor have been analyzed. Numerical simulations are conducted to study the heat transfer and fluid flow behavior of the device and to demonstrate the feasibility of our design. The temperature profile and the velocity field distribution under different applied acceleration have been acquired. Moreover, a method for manufacturing the accelerometer by using the techniques of micromachining is provided and the performance of the presented design has been examined. The results concluded that the proposed design has better response and sensitivity comparing to its counterparts.Copyright © 2004 by ASME

In this study, a novel thermoelectric infrared microsensor (TIMS) is designed by using commercial CMOS IC processes with subsequent bulk-micromachining process. This microsensor has the advantages of high fill factor, low noise equivalent temperature difference (NETD), and simple fabrication process. The key feature is that thermocouple cantilever beams with low solid thermal conductance have been placed under the membrane of thermoelectric infrared microsensor. In order to improve the performance of the infrared sensor, the basic physical characteristics of this sensor have been analyzed. Finite element analysis is used to simulate the electro-thermo-mechanical behavior of the device and to demonstrate the feasibility of our design. Besides, a method for manufacturing the infrared microsensor is also provided and the performance of the presented design has been examined. The analytical results concluded that lowering down the number of the thermocouples does not affect the responsivity but do reduce the total resistance. Also, the detectivity and responsivity are obviously increased for the proposed TIMS. Finally, the deviation between the theoretical and the simulated results is discussed.

A conventional Pirani vacuum sensor is converted into a device able to measure high gas pressure. By referring to infinite pressure, heat-loss change from the reference to a measured pressure induces electrical signal on the resistive sensor. 0.3 /spl mu/m shallow gap is formed for the floating microsensors to increase its sensitivity. This results in a measurable range from 10/sup 5/ down to 10/sup -1/ Torr. The thermal microsensor differs from the piezoresistive or capacitive type in sensing mechanisms. It also has advantages in smaller size and simpler structure.

We present the development of a tunable phase grating using CMOS process in this paper. With CMOS processes, structure feature of sub-micrometer can be easily approached. In the design of our grating devices, we have ribbons of 0.7um and minimum separate spacing of 0.65um between ribbons. We used aluminum as ribbon material in our design, The ribbons were released via RIE to remove the SiO2 sacrificial layer. In our devices, we have successfully released the ribbons with the width from 0.7um up to 2um. The dry etching processes, which we developed to release ribbons in our devices, can avoid sticking problems and structure destruction. For electrostatic actuator, we use partial electrode design to obtain wider flat-reflection sections, and larger steady tuning distance. In this paper, we describe design, modeling, simulation, and measurement results of our tunable grating devices.

Phase-locked loop ( PLL ) , as well known, is a very popular and cheap tool for pulse generation with almost constantfrequency. On the other hand, a user-friendly and cheap tool for micro-displacement/capacitance servo control system stilllacks in the market, although it is increasing the need in MEMS (micro-electro-mechanical system) industries. In this article,a cheap ( for a micro capacitance/displacement scan movement, without the need of A/D and D/A converters ) and stablemicro-displacement/capacitance measurement and control system is proposed. Simulations and experimental results showthat, if the properties of the electronic components used in the PLL remain close to their nominal values, the proposedsystem can achieve good capacitance/displacement measurement and/or servo control accuracy with high resolution.Application examples show that it is very useful in the micro-positioning system and MEMS industries. Keywords: capacitance measurement, micro-displacement servo control, MEMS, phase-locked loop

A novel technique to fabricate binary microlens on polymer substrates by 248 nm KrF excimer laser micromachining is proposed. A successfully fabricated eight-level binary microlens with diameter 1.25 mm and focal length 43 mm on polycarbonate (PC) sheet is also reported. Using this technique, microlens patterns are mask-projected on the polymer materials via the laser ablation effect instead of complicated multi-stepped lithography and etching processes. Moreover, the precise ablated depth of microlens can be achieved by adequately controlling the number of laser pulses. In order to reduce alignment complexity and offset, multiple mask patterns are produced in one quartz plate and the mask holder is loaded by a servo-controlled x-y stage. SEM pictures and optical interference inspections show that the etched surface and sidewall have roughness deviation less than 30 nm, which is compatible with those results obtained by other techniques. This technique can fabricate a 2 X 2 array of eight-level binary microlens in about several seconds. He-Ne laser and proper optics arrangements are used to measure the diffraction efficiency of the fabricated devices. Experimental results show that the unique technique can produce the multi- level microlens with submicrometer feature size, high-quality surface morphology, and satisfactory optical characteristics.

Anisotropic etching characteristics of (111)-oriented silicon in alkaline solutions was studied. Through a spoke pattern, it was found that (110) planes have the highest etching rate rather than high-index ones such as (211) or (331). With a round open, the final emergent periphery is hexagonal. The six sidewalls are defined by other (111) facets from its crystal geometry with three inclining angles of 70.5 degrees and another three declining angles of 109.5 degrees. The etched bottom surface morphology was also investigated by SEM pictures observation. Results show that aqueous KOH solution results in smooth surface due to its higher etching rate of residual oxide existed in the silicon, while the other etchants such as hydrazine (N2H4) and tetramethyl ammonium hydroxide (TMAH) induce seriously wavy roughness. As an application example, floating single-crystal silicon (c-Si) structures were fabricated with some potential functions as thermopile, silicon bolometer, mass flow transducer and other force microsensors.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

PMMA (polymethyl methacrylate) has been widely used as x-ray LIGA material for its good features of electrical acid plating of all common metals to industrial applications. Unlike the tough characteristics of polyimide in almost all alkaline and acid solutions, PMMA is easily removed in chemical etchants after electroplating process. For this reason, ablation- etching characteristics of PMMA material for 3D microstructures fabrication using a 248 nm KrF excimer laser were investigated. Moreover, the uses of the laminated dry film were also studied in this work. Experimental results show that PMMA microstructures can produce the near-vertical side- wall profile as the laser fluence up to 2.5 J/cm2. PMMA templates with high aspect ratio of around 25 were demonstrated, and the sequential electroplating processes have realized the metallic microstructures. Moreover, the microstructures fabricated in dry film show the perfect side- wall quality, and no residues of debris were found.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.