A Solenoid-type Inductors have been realized using electroplating technique mainly used for 2 Ghz band CMOS RF VCO applications. The integrated spiral inductor has low Q factor due to substrate loss and skin effects. And it also occupies large area compared to solenoid-type inductor. The direction of flux of the solenoid-type inductor is parallel to the substrate, which can lower substrate loss and other interference with integrated passive components. In this research, Solenoid-type inductors are simulated and modeled as equivalent circuit for CMOS RF VCO based on extracted S- parameters. The electroplated solenoid-type inductors are fabricated on both a standard silicon substrate and glass substrate by thick PR photolithography and copper electroplating. The achieved inductance varies range from 1 nH to 5 nH, and maximum Q factor over 10. The inductors are scheduled to be integrated on CMOS RF VCO with RF MEMS capacitor for future.
High frequency, micromechanical bandpass filter, with tunable frequency and bandwidth are demonstrated in a polysilicon surface micromachining technology. These filter utilized a parallel-resonator architecture, in which properly phased outputs from two or more micromechanical resonators are combined to yield a desired filter spectrum. Damping effect was shown to have a significant factor in affecting the flat passband of the filter and will be further analyzed in this paper.
Area-varying tunable MEMS (MicroElectroMechanical Systems) capacitor with 608 comb fingers is developed. The 6 um-thick single crystal silicon MEMS structure is bonded to the pyrex glass substrate using the glass-silicon anodic bonding technique and chemical mechanical polish to make the designed capacitor. The pyrex glass is used as a substrate instead of the silicon for reducing the RF losses through the substrate. The measured capacitor shows the nominal capacitance of 1.4 pF, Q-factor of 4 at 1 GHz. The capacitor model is also developed and proved by Serenade software of Ansoft Corporation.
Both electrical and mechanical models, exemplified with a micromachined capacitive switch with simple bridge structure, accurately describing its electrical and mechanical characteristics are described in this paper. The electrical model is represented as a RLC circuit, while the mechanical model is represented as a fixed-fixed beam. The advantage of these models is that it is possible to pre- determine various characteristics, such as the switching time of micromachinecd capacitive switches, during the design stage. These models can be used to accurately design micromachined capacitive switches for microwave applications. An illustrated fabrication process is also discussed.
Microfabrication technologies for use as practical methods in > 10-micrometers featured high-speed device fabrication have been developed: the thick polyimide-used damascene process, electroless plating of Ru/Ni on Cu interconnections, the area-restricted chemical mechanical planarization to polish thick polyimide films. Applying their technologies to fabricate RF-components and millimeter-wave components on Si demonstrates excellent characteristics: high-quality factor (Q-factor) in spiral inductor, low transmission loss for sidewall coplanar waveguide (CPW), high-power radiation in CPW-fed sot antenna. The Si-technology-based approach to achieve seamless integration of different kinds of devices, i.e., photonic devices, ULSIs, RF-devices, and millimeter- wave devices are promising ways to fabricate high-speed systems on Si.
Design and fabrication of a 32 X 32 uncooled IR focal plane array based on Si micromachining technique is presented. Ferroelectric lead zirconate titanate (PZT) thin film was used as the sensing material in the array. The PZT thin film was deposited on the top of Si substrate coated with silicon dioxide, silicon nitrite, titanium and platinum. Sol-gel method was used to deposit the PZT film. Size of the sensing element is 60 X 80 micrometers 2 and pixel size is 80 X 100 micrometers 2, yields a filling factor of 60%. In order to eliminate the thermal loss from the PZT elements to silicon substrate to improve the response of the IR sensor, silicon substrate under the sensing element was etched off using KOH micromachining technique. Membrane composed of silicon dioxide and silicon nitride was formed. Membrane size as large as 3.2 X 3.8 mm2 is fabricated. Results proved that micromachining is an effective way in fabricating uncooled IR focal plane array based on ferroelectric thin films. The process is totally compatible with standard IC fabrication techniques.
An X-ray microcalorimeter that consists of an x-ray absorber to transfer the incident photon energy to the temperature rise, a temperature sensor to detect the temperature change and suspending beams for thermal isolation from the substrate have been fabricated. Titanium/Gold thin film transition edge sensor (TES) is used as the temperature sensor. We fabricated and tested the first prototype in the previous study and obtained the transition temperature of 0.52 K, energy resolution of 550 eV (FWHM) for 6 keV radiation. These values were smaller than that of expected. We applied a Sn absorber and redesigned the microstructure of the x-ray microcalorimeter. Consequently, we have obtained 158 eV at 5.9 keV radiation of the energy resolution, which is about 4 times higher than that of the first prototype. This value is nearly equal to the conventional X-ray CCD. The highest energy resolution of the x-ray microcalorimeter of our design is estimated to approximately 5 eV at the operating point of 0.2 K. To realize such a good energy resolution calorimeter array, we are going to improve the sensitivity of the TES by optimizing the process condition. A Sn absorber formed by electroplating is also under evaluating simultaneously. It is necessary to fabricate uniform array structures.
Micro temperature sensors are needed for non-contact measurement of temperatures of micro devices and components. The miniaturization of existing temperature sensors for non- contact temperature measurement are limited by their sensing methods which sense the temperatures by measuring the radiation energy. In this study, a micro sensor for non- contact surface temperature measurement is designed using a new approach in which the temperature is determined by measuring the blackbody radiation wavelength corresponding to the surface temperature, based on Plank's law for blackbody thermal radiation and Wien's theorem for the relationship between wavelength of radiation and the corresponding blackbody temperature. The radiation wavelength is determined through measuring the electrical field of the radiation waves, based on the theory of electromagnetic field of blackbody radiation. The micro temperature sensor designed using this approach comprises a group of probes in micrometer or nanometer scales for collecting electrical signals from the electric field of blackbody radiation and a data processing circuit for signal amplification as well as for determining the surface temperature according to the measured radiation wavelength. In this way, the sensor requires no calibration. The measurable range of temperatures is determined by the size of the probes, and the precision of the measurement is determined by the precision of the probes.
Silicon micromachining technology provides a cheap, massproduceable means to manufacture simple, low power consumption integrated metal oxide thin film gas sensors for industrial, environmental and medical purposes. Small size, low power consumption, low noise, low manufacturing cost, fast response time, long term stability under harsh conditions such as high temperature and aggressive gas atmospheres, as well as high selectivity are the basic requirements for the new micromachined gas sensor developed in this paper. The developed semiconductor gas sensor can be fabricated by the techniques that are compatible with IC fabrication. According the results of thermal simulation of the present gas sensor, the thermal isolation structure can work effectively. Uniform temperature distribution can be obtained while heating the suspended membrane. The supporting bridges can resist the heat transfer from membrane to silicon frame effectively. In the meantime, the heating response is very fast, and the power consumption is below 10 mW at the operating temperature of 300 centigrade.
In this paper, the feasibility of a self-oscillating anemometer is examined. A 2D numerical study of a novel self-oscillating anemometer that can be fabricated using micromachining techniques is performed. The device is essentially a square cylinder suspended in the fluid flow by a fixed beam. The flow velocity can be easily measured by determining the frequency of oscillation obtained from capacitance sensing. Anemometer with different length scales can be fabricated to enable different ranges of velocities to be measured.
In this paper, simulation studies to determine the feasibility of producing filaments using `drop and demand' techniques are presented. These filaments will break up into droplets due to the phenomena caused by Rayleigh instability. In the biomedical applications, for effective pulmonary drug delivery of insulin, for example, the drug particles must be in the range of 1 to 5 microns in size. This stringent requirement is also encountered in gas flow seeding for Laser Doppler Velocimetry studies. A piezoelectrically actuated MEMS atomizer based on Rayleigh instability-driven break-up of filaments has been designed to meet this requirement. Although the formation of droplets from jets has been used extensively in ink-jet printing, the currently presented mode of droplet formulation has yet to be demonstrated in a MEMS device.
We report the fabrication of a microfluidic biochip integrated with an acoustic wave sensor that can be used to characterize the contraction of single cardiac (heart) muscle cells. The work will lead to rapid analysis of single muscle cells in response to various drugs by determining changes in mass and viscoelastic properties during cell contraction and relaxation. The microfabricated device is a combination of a top cover plate which is a glass substrate containing etched channels and a bottom plate which is an AT-cut quartz crystal with excitation electrodes. The glass plate is micromachined with a network of channels and chambers, which is intended for delivery of fluids, selection and retention of single muscle cells. The bottom plate (quartz crystal) comprises all the patterned electrodes for acoustic wave launching and detection. The quartz plate is operated in the thickness-shear acoustic wave mode.
The principles of dynamic vibration absorbers or shock absorbers are used in a novel way to provide magnification rather than to suppress the unwanted vibration amplitude. The dynamic vibration magnifier (DVM) can be realized as a multi-degree freedom of systems or simply just two degrees of freedom system. The concept of DVM can be applied in the field of microelectromechanical systems, particularly in resonating microsensors for example resonating microgyroscope, micropump and microbridges. These sensors and other micromechanical resonating structures require large displacement or vibration amplitude for improving their working range or sensitivity and hence the DVM can provide an excellent method of magnification. The concept presented in this paper is two-fold; the DVM method can be used as an actuator as well as a sensor.
This paper presents an optimized out-of-plane microgyroscope layout generator using AutoCAD R14 and MS ExcelTM as a first attempt to automating the design of resonant micro- inertial sensors. The out-of-plane microgyroscope with two degrees of freedom lumped parameter model was chosen as the synthesis topology. Analytical model for the open loop operating has been derived for the gyroscope performance characteristics. Functional performance parameters such as sensitivity are ensured to be satisfied while simultaneously optimizing a design objective such as minimum area. A single algorithm will optimize the microgyroscope dimensions, while simultaneously maximizing or minimizing the objective functions: maximum sensitivity and minimum area. The multi- criteria objective function and optimization methodology was implemented using the Generalized Reduced Gradient algorithm. For data conversion a DXF to GDS converter was used. The optimized theoretical design performance parameters show good agreement with finite element analysis.
This paper presents a single crystal silicon low-g open loop microaccelerometer designed and fabricated through a spreadsheet optimization methodology. The paper begins with the theoretical formulation and analysis of the differential capacitive accelerometer with full-scale measurement range of +/- 2 g and mg resolution. The `House of Quality' was then used to model and analyze the sensor design variables and device specifications qualitatively. The optimization was implemented using the Excel SolverTM and MATLAB. The effects of electrostatic spring constant on the natural frequency and sensitivity of the accelerometer have been thoroughly discussed. The ratiometric error for this system has been optimized and is well below 2% with a cross axis sensitivity of less than 3%. The operating voltage is 5 V DC. The construction is based on a hybrid two-chip design and the sensing element is wire bonded to a CMOS ASIC.
Thin film shape-memory alloys have been recognized as a promising and high performance material in the field of microelectromechanical systems applications. In this investigation, TiNi films were prepared by sputtering Ti and Ni target in argon gas using a magnetron sputtering system. Chemical composition, crystallography, microstructure and phase transformation behaviors of the deposited TiNi film were studied. Differential scanning calorimeter results showed that a two-stage transformation occurs in a sequence of monoclinic martensitic phase to rhombohedral phase, then to B2 phase upon heating, and vice versa on cooling. X-ray diffraction analysis also revealed the crystalline structure changes with the change of the temperatures. Nano- indentation reveals the elastic modulus of the film is about 5.11 GPa and the film intrinsic hardness is 2.84 +/- 0.5 GPa. By depositing TiNi films on the bulk micromachined Si cantilever structures, we obtained micro-grippers exhibiting a good shape-memory effect.
The relationship between the resist layer thickness, the masking layer thickness and x-rays wavelength was investigated to optimize submicron structures formation in 10 - 100 micrometer resist layers. It was shown that the optimal wavelength for 50 - 100 micrometer resist layer exposure is 0.4 nm. A specially designed medium-power soft x-ray tube with a water-cooled exchangeable anode was built for experiments in a high aspect ratio structures formation. Experimental investigations were carried out for 0.417 and 1.33 nm wavelength radiation. Test x-ray masks with 0.1 micrometer Si3N4 membrane and a gold absorption layer with 0.2 - 0.7 micrometer thickness were used for high aspect ratio structures formation in ERP-9 and UVIII resists with thickness from 2 to 10 micron. The 3 micrometer thick gold mesh with 15 micrometer pitch was used as a mask for structures formation in 100 micrometer thick SU8 resist layer with 0.417 nm x-rays.
A successful ablation of Indium Tin Oxide (ITO) coated on PET substrate without damage the substrate is presented in this paper. ITO is a thin film coated on glass and plastic plates as used in flat panel displays (FPD). The conventional machining method is practiced by a wet chemical etching process. This process includes photoresist coating, exposure, development, wet etching, and stripping. Since the ITO coated on PET have the advantages of low cost, less weight, and ductility over than conventional ITO coated on glass. It takes more attentions on this material combination. However, direct-write laser to pattern ITO films on glass has been reported. The ablation of ITO coated on PET is unexplored so far. The experiment of this study uses the KrF ((lambda) equals 248 nm) excimer laser to selectively ablate ITO patterns coated on PET, it generates successful results. Since the excimer laser with short wavelength, high energy density, and short pulse period. It suddenly evaporates the material and minimizes the heat effect on the substrate. The micromachined profile of ITO patterns coated on PET is measured by an atomic force microscopy. The minimum line width can be down to 10 micrometers and avoid any damage to the substrate.
Diamond microstructures were patterned over silicon/silicon dioxide substrate using the processes combined with bulk or surface micromachining, selective growth of diamond and plasma etching technique. Polycrystalline diamond films were prepared using microwave plasma enhanced chemical vapor deposition and a gas mixture of hydrogen and methane. (111)- and (100)-oriented diamond films were synthesized and smooth (100)-textured thin films were successfully deposited on silicon structures, such as trenches, corners, edges, forming a good heat-diffusing and insulating layer as well as a protective wear-resistant surface. Two types of techniques for precise patterning of diamond microstructures were investigated in this paper. The first one was to selectively grow diamond films in the desired region by pre- depositing a Pt interlayer on silicon dioxide layer. The second one was to selectively etch the deposited diamond film by oxygen/argon plasma under an Al mask. Different microstructures, for example, diamond membrane, microgear, microrotor, comb drive structure, etc. were successfully fabricated.
We present the design and characterization of a new 4 X 4 switch based on the previously developed 2 X 2 fiber switch. The switching principle uses plasma etched vertical mirrors that can be moved in and out of two pairs of optical fibers with the integrated electrostatic actuator. The 4 X 4 switch is built by connecting 16 individual 2 X 2 switches in a common package (100 X 50 X 35 mm). Instead of integrating the 16 switch elements on the same chip, we preferred assembling the switches by fusion splicing. The insertion loss is less than 1.8 dB for each state.
This paper reports the design, fabrication and test of a monolithically-integrated 4 X 4 free-space optical crossconnect using microfabricated polysilicon 3D-mirror to enable light-path switching for optical communication applications. The switch consists of 16 pairs of 3D movable mirrors and draw-bridge plate actuators, and four input and output fiber-optic guiding rails. The draw-bridge plates actuated by the electrostatic force drive the 3D-mirrors up and down to cut off the light beam or to let the light beam pass through. The optical crossconnect is fabricated using three-layer-polysilicon surface micromachining technology. The size of the whole structures is 5 mm X 5 mm. The maximum driving voltage is about 45 V, and its resonant frequency is about 5 KHz (200 micrometers switch time). The optical insertion loss of about 1.5 dB and the crosstalk of less than -60 dB have been obtained while using GRIN- lens to collimate the input optical signals.
This paper describes the development of a novel, flexible, with appropriate accuracy dynamic characteristics measurement system for optical scanning micromirror. With the system, we can measure dynamic behavior such as transient response, scan speed, scan angle, scan repeatability, and scan non-linearity of the canning micromirror devices. Moreover, the optical system performances such as scan spot size and even scan spot intensity can also be obtained.
Two monolithically-integrated tunable lasers have been analyzed, designed and fabricated. The potential applications for WDM have also been studied. The tunable lasers use 3D micromirrors integrated with single-mode Fabry-Perot laser diodes and anti-reflection coated optical fibers. The difference between the two tunable lasers is that one uses the movable 3D micromirror driven by comb- drive to change the external cavity length, and the other uses the rotatable 3D micromirror driven by thermal-actuator to change the external feedback strength. For the frequency tuner that uses movable 3D micromirror, a wavelength tunability of 16 nm is obtained using 3V driving voltage. As for the frequency tuner that uses rotatable 3D micromirror, a wavelength tunability of 7 nm is obtained while using 10 mA driving current.
The construction of self supporting or suspended structures is one of the fundamental challenges of MEMS, with many technologies existing for the fabrication of such structures, such as bulk micromachining and surface machining. Generally surface micromachining techniques rely on the high temperature deposition process such as LPCVD, which produce high quality films. Process technologies exist for the deposition of material at substantially reduced temperatures, in particular PECVD that can deposit films at temperatures <300 degree(s)C. Plasma Enhanced Chemical Vapor Deposition (PECVD) of silicon nitride has not been used extensively in MEMS structures due to the material limitations created via the deposition technique, primarily controllability of the intrinsic stress and etch selectivity of the deposited film. We show here that PECVD silicon nitride can be used successfully in MEMS structures, and that the intrinsic stress is controllable through variations in the PECVD deposition parameters. A MEMS based Fabry-Perot cavity was fabricated using PECVD silicon nitride as the membrane layer with ZnS as the sacrificial material. Devices with an initial 1-micron cavity length typically provide a displacement of 320 nm across a 300 micrometers membrane span for an applied bias of 2.4 V.
This paper presents a micromachining technique to solve the precision machining difficult for multi-fiber ferrule production. The LIGA technology is applied to make 1.2 mm thick V-groove mold inserts with dimensional tolerance 1 micrometers . It stars with x-ray mask fabrication, x-ray exposure, Ni-Co electroforming, and planarization to complete the metallic ferrule mold inserts. X-ray mask is developed here in low cost and accessible in Taiwan. The absorber thickness can be achieved to 30 micrometers in straightness. The single x- ray exposure can generate 1.2 mm thick PMMA after development process. This development proves the feasibility of many applications in x-ray micromachining. In the optical fiber passive components, connectors play a joint role int he whole system. Ferrule i the key part of a fiber connector. Since the development of the LIGA technology, high precision micro-components such the ferrule is considered to be applied. All multi-fiber ferrules require the same accuracy of pitch distance between two channels. The mold insert for ferrule fabrication becomes the most important part. Conventional precision machining has certain limitations on machining micro-components due to machining tool size and material wears. The LIGA technique can overcome these problems. It utilizes x-ray to penetrate polymer material and create molds, then applies electroforming to make metallic molds. These molds can be applied for molding process in mass production.
The patterning of diamond thin films by RIE etching must use hard mask. Ni and NiTi thin films are better candidate to be used as diamond mask based on mask selective ratio and patterning process. NiTi thin film mask has higher etching selective ratio than that of Ni thin film, Ni thin film plating through mask is applicable to small microstructure fabrication because of moderate etching selective ratio, accurate in dimension control and easy to make multilayer microstructure. The diamond thin film microstructure using NiTi and Ni thin film masks fabricated by RIE etching have straight line and sharp sidewall.
Reactive Ion Etching is an effective method for etching of diamond films, in this paper, the influences of maskant, system pressure and the composition of reactive gas on the etch rate and etched surface of diamond were studied. A gas mixture of O2 and Ar was used as the reactive agent, the concentration of Ar in this mixture is in the range of 0 to 100% (V/V), and the etching result reveals that argon is not necessary. The system pressure plays the dominant effect on the etched surface and etched contours of diamond structures. The highest etch rate appears in the range of 60 - 100 Torr, very low and very high pressure both result in etch rate decreasing. The maskant plays an important role in etching process, it can be sputtered and re-deposited on the etched surface of diamond and act as a micro mask, results in rougher etched surface in some conditions. The optimum processing parameters were achieved, and combined this patterning process with conventional photolithography and sacrificial wet etching process, we have formed a new type of surface micromachining technique for fabrication of diamond MEMS structures. Typical MEMS structures such as cantilever beams, diamond micro hinge and diamond tips array have been fabricated successfully.
Variable angle spectroscopic ellipsometry (VASE) has been used to monitor the deposition of silicon nitride (SiNx) and polycrystalline silicon (poly-Si) by low pressure chemical vapor deposition. SiNx with different nitrogen content and poly-Si were deposited onto Si wafers with a thin layer of thermal oxide. Ellipsometric data was acquired over the spectral range 270 nm - 1700 nm at multiple angles of incidence. For each material, two optical function models were used for fitting of the ellipsometric spectra. In the case of SiNx, the Cauchy model and the parametric semiconductor model resulted in fits of comparable quality and the optical functions of SiNx depend on the flow ratio of the dichlorosilane and ammonia used for the deposition. For poly-Si, the parametric semiconductor model was found to give a better fit than the Bruggeman effective medium approximation. In addition, some of the poly-Si samples were diffusion doped and in-situ doped with phosphorus. Using the same optical function models, it was found that diffusion doping resulted in increased crystallinity of the poly-Si. For the in-situ doped poly-Si, there was little change in the optical functions before and after annealing at 1000 degree(s)C. These results demonstrate that VASE is useful for in-line monitoring of thin film deposition in microelectronic processing.
The authors have been carrying out investigations on the fabrication of micro-tools such as medical devices. Until now, demands for higher productivity of micro tools have been overcome by applying molding technologies. On the other hand, demands for higher shape freedom have been satisfied by the use of cutting technologies. Generally, machining processes using the end mill are applied for creating complicated shapes. However, the minimum size of an ordinary end mill is about 0.1 mm, and grooves smaller than this size cannot be machined. In the previous report, the authors proposed a special oblique-cut mill. This tool has a very simple shape made by diagonally cutting a cylindrical tool material. It can be made even more miniature easily. However, in return for the simplification of the tool fabrication process, the cutting performance drops. To avoid this, optimum cutting conditions must be selected. In this study, the appropriate cutting conditions were reviewed based on the measurement results of the cutting force. At the same time, 3D shapes were also created using the special oblique-cut mill.
Research into Microelectromechanics (MEMS) and Nanotechnology covers the range of feature dimensions from submillimeter to nanometer scales. It relies upon tools and processes for lithography and pattern transfer drawn largely but not exclusively from the silicon semiconductor industry. Optical lithography systems, particle beam nanowriter tools and X-ray sources may be regarded as the `machine tools' for MEMS and Nanotechnology, each with their unique advantages and limitations. They are being exploited for R&D applications ranging from customized MEMS to vacuum microelectronics and novel nanotools such as electron microcolumns and multiple tip scanning probe systems.