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Microelectromechanical Systems, Journal of

Issue 1 • Date March 2000

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Displaying Results 1 - 21 of 21
  • JMEMS Reviewers - 1999

    Publication Year: 2000 , Page(s): 2
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    Freely Available from IEEE
  • Localized silicon fusion and eutectic bonding for MEMS fabrication and packaging

    Publication Year: 2000 , Page(s): 3 - 8
    Cited by:  Papers (79)  |  Patents (52)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    Silicon fusion and eutectic bonding processes based on the technique of localized heating have been successfully demonstrated. Phosphorus-doped polysilicon and gold films are applied separately in the silicon-to-glass fusion bonding and silicon-to-gold eutectic bonding experiments. These films are patterned as line-shape resistive heaters with widths of 5 or 7 /spl mu/m for the purpose of heating and bonding. In the experiments, silicon-to-glass fusion bonding and silicon to gold eutectic bonding are successfully achieved at temperatures above 1000/spl deg/C and 800/spl deg/C, respectively, by applying 1-MPa contact pressure. Both bonding processes can achieve bonding strength comparable to the fracture toughness of bulk silicon in less than 5 min. Without using global heating furnaces, localized bonding process is conducted in the common environment of room temperature and atmospheric pressure. Although these processes are accomplished within a confined bonding region and under high temperature, the substrate temperature remains low. This new class of bonding scheme has potential applications for microelectromechanical systems fabrication and packaging that require low-temperature processing at the wafer level, excellent bonding strength, and hermetic sealing characteristics. View full abstract»

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  • Surface micromachined polysilicon heart cell force transducer

    Publication Year: 2000 , Page(s): 9 - 17
    Cited by:  Papers (38)
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    A microelectromechanical systems (MEMS) force transducer system, with a volume less than 1 mm/sup 3/ millimeter, has been developed to measure forces generated by living heart muscle cells. Cell attachment and measurement of contractile forces have been demonstrated with a commercially fabricated surface-micromachined hinged polysilicon device. Two freestanding polysilicon clamps, each suspended by a pair of microbeams, hold each end of a heart cell. When the cell contracts, the beam bend and force is determined from the measured deflection and the spring constant in the beams. The average maximal force over seven contractile experiments using a calcium solution stimulus was F/sub max/=12.6/spl plusmn/4.66 /spl mu/N. Normalizing to a cross-sectional area, F/sub max//area was 23.7/spl plusmn/8.6 mN/mm/sup 2/. These force data were also correlated to optically imaged striation pattern periodicity. Intermediate forces were also measured in response to a calcium solution gradient and showed similar behavior to those measured in other laboratories. This MEMS force transducer demonstrates the feasibility of higher fidelity measurements from muscle cells and, thus, an improved understanding of the mechanisms of muscle contraction. View full abstract»

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  • A miniature pressure system with a capacitive sensor and a passive telemetry link for use in implantable applications

    Publication Year: 2000 , Page(s): 18 - 23
    Cited by:  Papers (51)  |  Patents (5)
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    A miniature telemetric pressure-measuring system is presented in this paper. The system uses passive telemetry to transfer power to the transponder and pressure data to the remote base unit. Such telemetric systems are becoming ever more important in the biomedical field as the interest for in-vivo measurements of different biological parameters both of humans and animals is increasing. A novel capacitive-type pressure sensor based on an SiGeB diaphragm is used as a sensing element. The merits of combining a capacitive pressure sensor and passive telemetry lies in the inherent low-power consumption of the sensor and the continuous availability of power through induction. The pressure sensor is connected to an integrated interface circuit, which includes a capacitance to frequency converter and an internal voltage regulator to suppress supply voltage fluctuations on the transponder side. In addition, the sensor and accompanying interface circuit take up very little space so as to be suitable for implantation. View full abstract»

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  • A three-dimensional shape memory alloy microelectrode with clipping structure for insect neural recording

    Publication Year: 2000 , Page(s): 24 - 31
    Cited by:  Papers (31)
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    A microelectrode, with clipping structure for neural recording from a free-moving insect, was designed and fabricated using a shape memory alloy (SMA) thin film. The SMA thin films (titanium nickel; Ti-48 at.%Ni) are deposited by RF magnetron sputtering and patterned by HF-HNO/sub 3/ wet etching. The transformation temperatures of the SMA thin films were measured at 54/spl deg/C (A*) and 50/spl deg/C (M*). The SMA microelectrode consists of a "hook" structure (720 /spl mu/m/spl times/480 /spl mu/m) and two "C"-shape probes (600 /spl mu/m/spl times/70 /spl mu/m). The electrode impedance is about 5 k/spl Omega/ at 1 kHz. The desired three-dimensional (3D) shape is given to the electrode by a bonded wire. The clinging force of the electrode to the nerve is enhanced by the 3-D structures. The SMA microelectrode can clip a nerve cord tightly. The damages of the nerve by thermal actuation of the clip are not observed by physiological analysis. The neural activity from a living insect was successfully recorded with this SMA microelectrode. View full abstract»

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  • Design and performance of a micro-sized biomorphic compound eye with a scanning retina

    Publication Year: 2000 , Page(s): 32 - 37
    Cited by:  Papers (7)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (211 KB)  

    Proposes a design of a biomorphic micro visual sensor equipped with a mechanical scanning system. The sensor is inspired by the structure of the fly's compound eye, which was found to possess a unique muscle and tendon actuation system for its scanning retina. The improvement in micro-opto-electro-mechanical systems encourages the design of reliable, efficient, and integrated smart visual sensors for robotic applications, in particular, for the autonomous visually guided navigation of mobile robots. The authors have verified the effect of retinal scanning for a robotic visual system through the construction of a large-scale prototype at the millimeter scale. The performance of a newly fabricated microelectromechanical system prototype whose size approaches the order of the insects' compound eyes is then evaluated in comparison with that of the large-scale prototype. The micro-sized visual sensor is composed of a scanning microlens array (120 /spl mu/m in lens diameter) and a photo-diode array. The actuation of the microlens array induces a rotation of the visual axes. According to the principle of retinal scanning, the micro-sensor is able to retrieve the local angular velocity with enhanced reliability. View full abstract»

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  • Optimal performance of CMOS compatible IR thermoelectric sensors

    Publication Year: 2000 , Page(s): 38 - 46
    Cited by:  Papers (13)
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    This paper presents a theoretical and empirical study of the optimal performance of CMOS compatible infrared thermoelectric sensors with varying pixel area and different aspect ratio of the pixels for two possible sensor structures: cantilever and bridge types. Optimal performance is analyzed analytically, using simplifying assumptions. This analysis is verified by comparing with the exact simulations as well as by comparing with measured results. The resistance of optimized sensors in the sense of minimal noise equivalent power (NEP) is shown to be independent of aspect ratio, but proportional to the third root of the pixel area. The product of the optimal NEP and the square root of the time constant is shown to be constant with varying aspect ratios, while the same applies with the time constant to the power of 3/8 for varying areas. The measured sensors exhibit NEP's down to 13.5 nW in a 300-Hz bandwidth and time constants up to 30 ms. View full abstract»

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  • Micromachining of diamond film for MEMS applications

    Publication Year: 2000 , Page(s): 47 - 51
    Cited by:  Papers (17)
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    We realized two diamond microdevices: a movable diamond microgripper and a diamond probe for an atomic force microscope (AFM), consisting of a V-shaped diamond cantilever and a pyramidal diamond tip, using a microfabrication technique employing semiconductive chemical-vapor-deposited diamond thin film. The microgripper was fabricated by patterning the diamond thin film onto a sacrificial SiO/sub 2/ layer by selective deposition and releasing the movable parts by sacrificial layer etching. The diamond AFM probe was fabricated by combining selective deposition for patterning a diamond cantilever with a mold technique on an Si substrate for producing a pyramidal diamond tip. The cantilever was then released by removing the substrate. We report the initial results obtained in AFM measurements taken using the fabricated diamond probe. These results indicate that this diamond probe is capable of measuring AFM images. In addition, we have developed the anodic bonding of diamond thin film to glass using Al or Ti film as an intermediate layer for assembly. This bonding technique will allow diamond microstructures to be used in many novel applications for microelectromechanical systems. View full abstract»

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  • Air-bearing sliders and plane-plane-concave tips for atomic force microscope cantilevers

    Publication Year: 2000 , Page(s): 52 - 57
    Cited by:  Papers (3)  |  Patents (15)
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    This paper explores strategies for fabricating and maintaining a sharp atomic force microscope (AFM) tip suitable for AFM data storage applications. To this end, AFM cantilevers have been incorporated into micromachined sled carriers and air-bearing sliders. These supports act to limit the maximum loading force on the AFM tip and allow for improved vibration immunity for the AFM cantilever in comparison to macroscopic loading schemes. Readback from a patterned rotating disk has been demonstrated using these devices. Silicon-carbide AFM cantilevers with diamond tips have been fabricated in a process compatible with that of the sleds and sliders. Molded silicon-nitride tips defined by the intersection of three surfaces have also been fabricated for AFM cantilevers. The molds for plane-plane-concave tips are defined by two silicon {111} planes and a silicon-dioxide curved surface. By geometry, the three surfaces necessarily have a unique intersection point, which may improve the consistency in sharpness of these tips relative to conventional pyramidal tips. View full abstract»

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  • A high-performance planar piezoresistive accelerometer

    Publication Year: 2000 , Page(s): 58 - 66
    Cited by:  Papers (55)  |  Patents (6)
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    The micromachined piezoresistive accelerometer is now 20 years old. Design variations have been investigated, but commercial devices have generally maintained a consistent topology with incremental improvements. In this paper, a new approach is introduced to the design and construction of this device that offers functional and manufacturing advantages. Piezoresistive accelerometers are described that combine deep reactive ion etching and oblique ion implantation to form self-caging proof masses and flexures with vertical sidewalls and sidewall piezoresistive strain sensors. These devices deflect in-plane rather than out-of-plane, which allows one to form multiaxis accelerometers on one substrate. Performance is comparable to inexpensive commercial capacitive accelerometers and is limited by 1/f noise. The design, fabrication, and experimental characterization is presented. This new topology provides the foundation for a new category of piezoresistive accelerometers. View full abstract»

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  • The flow structure inside a microfabricated inkjet printhead

    Publication Year: 2000 , Page(s): 67 - 75
    Cited by:  Papers (58)  |  Patents (4)
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    A micrometer resolution particle image velocimetry system has been adapted to measure instantaneous velocity fields in an inkjet printhead. The technique uses 700-nm-diameter fluorescent flow tracing particles, a pulsed Nd:YAG laser, an epi-fluorescent microscope, and a cooled interline transfer charge-coupled device camera to record images of flow tracing particles at two known instances in time. Instantaneous velocity vector fields are obtained with spatial resolutions of 5-10 /spl mu/m and temporal resolutions of 2-5 /spl mu/s. The relationship between instantaneous velocity fields is compared to instantaneous shapes of the meniscus. The flow in the nozzle is highly unsteady and characterized by a maximum velocity of 8 ms/sup -1/, Reynolds numbers of Re=500, and accelerations of up to 70 000 times gravity (i.e., 70 000 g). Since the flow field is periodic for each ejection cycle, the instantaneous measurements can be phased averaged to determine the evolution of the average flow field. The ejection cycle period is 500 /spl mu/s, and consists of four primary phases: infusion, inversion, ejection, and relaxation. During infusion, the actuator plate is deflected downward creating a low pressure that draws fluid into the inkjet cavity through the orifice and pulls the meniscus into the cavity through the nozzle. The meniscus grows, begins to decrease in size, and then deforms in shape, becoming inverted for approximately 6 /spl mu/s. The meniscus exits the cavity through the nozzle during droplet ejection. During relaxation, the flow undergoes viscously-damped oscillations, and reaches equilibrium before the next ejection cycle begins. View full abstract»

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  • Three-dimensional micro-channel fabrication in polydimethylsiloxane (PDMS) elastomer

    Publication Year: 2000 , Page(s): 76 - 81
    Cited by:  Papers (367)  |  Patents (123)
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    This paper describes a fabrication technique for building three-dimensional (3-D) micro-channels in polydimethylsiloxane (PDMS) elastomer. The process allows for the stacking of many thin (less than 100-/spl mu/m thick) patterned PDMS layers to realize complex 3-D channel paths. The master for each layer is formed on a silicon wafer using an epoxy-based photoresist (SU 8). PDMS is cast against the master producing molded layers containing channels and openings. To realize thin layers with openings, a sandwich molding configuration was developed that allows precise control of the PDMS thickness. The master wafer is clamped within a sandwich that includes flat aluminum plates, a flexible polyester film layer, a rigid Pyrex wafer, and a rubber sheet. A parametric study is performed on PDMS surface activation in a reactive-ion-etching system and the subsequent methanol treatment for bonding and aligning very thin individual components to a substrate. Low RF power and short treatment times are better than high RF power and long treatment times, respectively, for instant bonding. Layer-to-layer alignment of less then 15 /spl mu/m is achieved with manual alignment techniques that utilize surface tension driven self-alignment methods. A coring procedure is used to realize off-chip fluidic connections via the bottom PDMS layer, allowing the top layer to remain smooth and flat for complete optical access. View full abstract»

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  • Trench-Hall devices

    Publication Year: 2000 , Page(s): 82 - 87
    Cited by:  Papers (3)  |  Patents (4)
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    A trench-Hall device sensitive to magnetic inductions parallel to the chip surface is reported in this paper. The vertically oriented active region is defined by two parallel trenches with a distance of only 2.4 /spl mu/m. Deep contacts connect the active region of the device at its bottom at a depth of 20 /spl mu/m. These deep contacts allow a symmetrical operating condition of the active region analogous to a lateral symmetrical Hall plate, which is favorable for dynamic offset reduction. With the presented technology, trench-Hall devices with a sensitivity of 320 V/A with a nonlinearity below 0.1% are realized. Additionally, the presented fabrication technique enables the electrically insulated cointegration of sensor and circuitry on a single CMOS chip. View full abstract»

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  • Lamb-wave microdevices fabricated on monolithic single crystal silicon wafers

    Publication Year: 2000 , Page(s): 88 - 93
    Cited by:  Papers (5)
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    Reliable and inexpensive microdevices that can be used in physical, chemical, biological, and environmental applications are in great demand. Lamb-wave (LW) ultrasonic devices have been shown to be extremely useful for applications in liquid environments. Working LW devices have been fabricated in this investigation on monolithic single crystal membranes using well-established integrated-circuit technology. The detailed fabrication procedure, photoacoustic testing of the piezoelectric material film, and a demonstration of device performance are presented in this paper. In practice, device performance was very sensitive to the surface quality of the membrane structure. This process presents the possibility for further size reduction, increased integration, and large-scale production. View full abstract»

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  • Micromachining of buried micro channels in silicon

    Publication Year: 2000 , Page(s): 94 - 103
    Cited by:  Papers (62)  |  Patents (85)
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    A new method for the fabrication of micro structures for fluidic applications, such as channels, cavities, and connector holes in the bulk of silicon wafers, called buried channel technology (BCT), is presented in this paper. The micro structures are constructed by trench etching, coating of the sidewalls of the trench, removal of the coating at the bottom of the trench, and etching into the bulk of the silicon substrate. The structures can be sealed by deposition of a suitable layer that closes the trench. BCT is a process that can be used to fabricate complete micro channels in a single wafer with only one lithographic mask and processing on one side of the wafer, without the need for assembly and bonding. The process leaves a substrate surface with little topography, which easily allows further processing, such as the integration of electronic circuits or solid-state sensors. The essential features of the technology, as well as design rules and feasible process schemes, will be demonstrated on examples from the field of /spl mu/-fluidics. View full abstract»

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  • Micromachined silicon resonant strain gauges fabricated using SOI wafer technology

    Publication Year: 2000 , Page(s): 104 - 111
    Cited by:  Papers (9)
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    The optimum mode of double-ended tuning-fork-style resonators is a lateral vibration in the plane of the wafer. Lateral vibrations are typically excited using the comb drive approach, but this requires modification to the resonator structure. This paper reports a simple method for exciting and detecting lateral vibrations without modifying the resonator, thereby enabling the optimum dynamically balanced structure to be used. This approach uses plane electrodes positioned parallel to the resonator's tines to excite the vibrations while the change in resistance along the length of the resonator enables the vibrations to be detected. Test devices have been fabricated in single-crystal silicon using the buried oxide in silicon-on-insulator wafers as a sacrificial layer. The resonators are 340-/spl mu/m long, 3-/spl mu/m thick with tines 2-/spl mu/m wide. The gap between the tines and the electrode is 2 /spl mu/m. Visual inspection in a scanning electron microscope and electrical tests have confirmed the validity of this approach. View full abstract»

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  • Microfabricated small metal cantilevers with silicon tip for atomic force microscopy

    Publication Year: 2000 , Page(s): 112 - 116
    Cited by:  Papers (16)  |  Patents (4)
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    Atomic force microscopy with small cantilevers is faster due to higher resonant frequencies and has a lower noise level. We report a new process to microfabricate small metal cantilevers with integrated silicon tips. This process is used to fabricate gold cantilevers that are 13-40-/spl mu/m long, 5-10-/spl mu/m wide, and 100-160-nm thick. The tip is first formed at the free end of a sacrificial oxide cantilever. The cantilever layer of the desired metal is then deposited on the nontip side of the sacrificial oxide cantilever. The oxide layer is removed to form the cantilevers with tips on them in a batch process. The highly stressed cantilevers are rapid thermal annealed for 60 s at 300/spl deg/C to relieve the stress. The gold cantilevers have been characterized through their thermal spectra and used to image in tapping mode. The process can be used, not only for gold, but also for any metal or compound that can withstand removal of sacrificial oxide cantilevers. View full abstract»

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  • Quality factors in micron- and submicron-thick cantilevers

    Publication Year: 2000 , Page(s): 117 - 125
    Cited by:  Papers (219)  |  Patents (18)
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    Micromechanical cantilevers are commonly used for detection of small forces in microelectromechanical sensors (e.g., accelerometers) and in scientific instruments (e.g., atomic force microscopes). A fundamental limit to the detection of small forces is imposed by thermomechanical noise, the mechanical analog of Johnson noise, which is governed by dissipation of mechanical energy. This paper reports on measurements of the mechanical quality factor Q for arrays of silicon-nitride, polysilicon, and single-crystal silicon cantilevers. By studying the dependence of Q on cantilever material, geometry, and surface treatments, significant insight into dissipation mechanisms has been obtained. For submicron-thick cantilevers, Q is found to decrease with decreasing cantilever thickness, indicating surface loss mechanisms. For single-crystal silicon cantilevers, significant increase in room temperature Q is obtained after 700/spl deg/C heat treatment in either N/sub 2/ Or forming gas. At low temperatures, silicon cantilevers exhibit a minimum in Q at approximately 135 K, possibly due to a surface-related relaxation process. Thermoelastic dissipation is not a factor for submicron-thick cantilevers, but is shown to be significant for silicon-nitride cantilevers as thin as 2.3 /spl mu/m. View full abstract»

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  • Electrostatic model for an asymmetric combdrive

    Publication Year: 2000 , Page(s): 126 - 135
    Cited by:  Papers (41)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    This paper presents an analytical solution to the electrostatic actuation of an asymmetric combdrive in out-of-plane and torsional motions. The exact solutions to force in the out-of-plane motion and the integral for torque in the torsional motion are obtained. The dependence of the peak force on the thickness of the movable fingers and the amount of overlap of the combs is given in closed form. Using our model, the shift of the natural resonant frequency due to a dc bias is analyzed. Furthermore, our solution also applies to the in-plane motion of an in-plane interdigitated combdrive. We found that an in-plane interdigitated combdrive generates a constant force within 0.1% when the minimum initial engagement length of the combs is twice the separation gap. View full abstract»

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  • Process-dependent thin-film thermal conductivities for thermal CMOS MEMS

    Publication Year: 2000 , Page(s): 136 - 145
    Cited by:  Papers (67)  |  Patents (2)
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    The thermal conductivities /spl kappa/ of the dielectric and conducting thin films of three commercial CMOS processes were determined in the temperature range from 120 to 400 K. The measurements were performed using micromachined heatable test structures containing the layers to be characterized. The /spl kappa/ values of thermally grown silicon oxides are reduced from bulk fused silica by roughly 20%. The /spl kappa/ of phosphosilicate and borophosphosilicate glasses are 0.94/spl plusmn/0.08 W m/sup -1/ K/sup -1/ and 1.18/spl plusmn/0.06 W m/sup -1/ K/sup -1/, respectively, at 300 K. A plasma-enhanced chemical-vapor-deposition silicon-nitride layer has a thermal conductivity of 2.23/spl plusmn/0.12 W m/sup -1/ K/sup -1/ at 300 K. This value is between published data for atmospheric-pressure CVD and low-pressure CVD nitrides. For the metal layers, we found thermal conductivities between 167 W m/sup -1/ K/sup -1/ and 206 W m/sup -1/ K/sup -1/, respectively, at 300 K, to be compared with 238 W m/sup -1/ K/sup -1/ of bulk aluminum. The temperature-dependent product /spl kappa//spl rho/ of /spl kappa/ with the electrical resistivity /spl rho/ agrees better than 8.2% between 180-400 K with that of pure bulk aluminum. The /spl kappa/ values of the polysilicon layers are between 22.4 W m/sup -1/ K/sup -1/ and 37.3 W m/sup -1/ K/sup -1/ at 300 K. They are reduced from similarly doped bulk silicon by factors of between 2.0-1.3. The observed discrepancies between thin film and bulk data demonstrate the importance of determining the process-dependent thermal conductivities of CMOS thin films. View full abstract»

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  • Self-buckling of micromachined beams under resistive heating

    Publication Year: 2000 , Page(s): 146 - 151
    Cited by:  Papers (37)  |  Patents (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    Self-buckling behavior of micromachined beams under resistive heating is described by an electromechanical model with experimental verifications. This model consists of both electrothermal and thermoelastic analyses for beam-shape polysilicon microstructures that are fabricated by a standard surface micromachining process. When an input electrical current is applied, Joule-heating effects trigger the thermal expansion of beam structures and cause mechanical buckling. The standard testing devices are clamped-clamped bridges, 2-/spl mu/m wide, 2-/spl mu/m thick, and 100-/spl mu/m long. It is found that a minimum current of 3.5 mA is required to cause beam buckling. Under an input current of 4.8 mA, a lateral deflection of 2.9/spl plusmn/0.2 /spl mu/m at the center of the bridge is measured with a computer image processing scheme. The experimental measurements are found to be consistent with analytical predictions. A discussion of modeling considerations and process variations is presented. View full abstract»

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Aims & Scope

The topics of interest include, but are not limited to: devices ranging in size from microns to millimeters, IC-compatible fabrication techniques, other fabrication techniques, measurement of micro phenomena, theoretical results, new materials and designs, micro actuators, micro robots, micro batteries, bearings, wear, reliability, electrical interconnections, micro telemanipulation, and standards appropriate to MEMS. Application examples and application oriented devices in fluidics, optics, bio-medical engineering, etc., are also of central interest.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Christofer Hierold
ETH Zürich, Micro and Nanosystems