An estimate of stiction force, rather than the more commonly reported surface energy, helps design reliable structures. Stiction is a major cause of failure in surface micromachined structures. We report on the modeling and estimation of the stiction force from simple I-V curves on cantilever beams which can be measured even on packaged devices. We have fabricated oxide anchored cantilever beams of polysilicon by surface micromachining. Current is measured for an applied bias between the beam and the substrate. Pull-in and pull-out voltages are determined as the points of maximum slope calculated by differentiating a cubic spline fit to the measured I-V data. The commercial package CoventorWare was used to develop an empirical model for estimating the pull-out voltage for the cases when there is no stiction and in the presence of stiction. A model is developed for finding the stiction force from the simulated and the experimental pull-out voltages. The method uses only measured values of pull-in and pull-out voltages and the beam length and does not require the value of Young's modulus. We also discuss an independent visual method to estimate the process stiction force from the cantilever beam array that is normally used to estimate the surface adhesive energy. An analytical model is developed to calculate the stiction force from the attachment length of long stuck cantilever beams that are released in the same process.

Recently, it has been proposed that sticking contact between micro-scale components may be relieved (i.e., the components may be unstuck) using structural vibrations. The means to excite these vibrations plays a critical role in the physical mechanism responsible for the initiation of stick-release. For example, it has been shown that mechanical actuation using, say, an instrumented nanoindentor is most effective near a resonant frequency. Aside from showing the fundamental mechanism responsible for the repair (resonance), it also provides insight for choosing optimal excitation parameters, such as excitation amplitude and frequency, for stick-release. In the present paper, periodic electrical excitation is explored as a means of inducing structural vibrations. It is shown that electrical excitation produces stick-release through a fundamentally different mechanism than its mechanical counterpart. Here, stick-release is achieved via unstable self-excited vibrations. This fact has a significant influence on the practical matter of choosing appropriate excitation parameters to produce the desired repair. Using the underlying physics, appropriate parameter combinations are mapped.

Large voltage differences between closely spaced MEMS structures can cause electrical breakdown and destruction of devices ^1-2. In this study, a variety of planar thin film electrode configurations were tested to characterize breakdown response. All devices were fabricated using standard surface micromachining methods and materials, therefore our test results provide guidelines directly applicable to thin film structures used in MEMS devices. We observed that planar polysilicon structures exhibit breakdown responses similar to published results for larger metal electrode configurations ^3-6. Our tests were performed in air at atmospheric pressure, with air gaps ranging from 0.5 μm to 10 μm. Our results show a sharp rise in breakdown level following increases in gap width up to about 3 μm, a plateau region between 3 μm and 7 μm, and breakdown in gaps over 7 μm following the Paschen curve. This profile indicates an avalanche breakdown process in large gaps, with a transition region to small gaps in which electrode vaporization due to field emission current is the dominant breakdown process. This study also provides information on using multiple-gap configurations, with electrically floating regions located near the energized electrodes, and the added benefit this method may provide for switching high voltage with MEMS devices. In multiple-gap configurations, we noted a transition between direct tip to tip breakdown across electrode gaps of 40 μm, and a preferential breakdown path through the electrically floating contact head region for electrode gaps over 100 μm.

Polytetrafluoroethylene (PTFE, trade name Teflon) has a wide range of unique and desirable physical, electrical and chemical properties. Its tribological properties are well-suited to anti-stiction applications, and its chemical inertness commends it as a barrier and passivation layer. However, conventional thin-film techniques are not suited for depositing Teflon films on microstructures. Spin coating is impossible because of the well-known insolubility of PTFE. Plasma polymerization of fluorocarbon monomers, ion beam and rf sputtering produce PTFE films that are deficient in fluorine. Pulsed laser deposition (PLD) using excimer and Ti:sapphire lasers is unsatisfactory because UV or near-IR laser ablation "unzips" the PTFE, and requires high-temperature annealing to re-polymerize the deposited monomeric film. We have demonstrated that a completely dry, vapor-phase coating technique - resonant infrared pulsed laser deposition (RIR-PLD) at a wavelength of 8.26 μm -produces crystalline, smooth Teflon films at low process temperatures. Indeed, the films as deposited by RIR-PLD exhibit a surprising degree of crystallinity even at room temperature. The stoichiometry and local electronic structure are preserved during the laser vaporization process, as demonstrated by IR absorption and X-ray photoelectron spectroscopy. Films deposited on microscale structures show good adhesion, excellent smoothness, and a high degree of conformability to the structures. We also discuss experiments planned for the near future to compare the tribological properties of the PTFE films deposited by RIR-PLD with those of other tribological coatings. We will also discuss the implementation of RIR-PLD in practical processing schemes for MEMS applications, including the challenge in adapting existing solid-state mid-IR laser technology for this purpose.

We have studied the corrosion of phosphorus-doped polySi when contacted to a gold metallization layer and exposed to various hydrofluoric acid (HF) based chemistries, including mixtures with HCl, C₂H₆O, H₂O, NH₄F, Triton-X-100, as well as vapor-based HF. Here, we utilize optical-, electron-, and atomic-force-microscopy, optical interferometry, as well as instrumented indentation ("nanoindentation") to characterize test and reference specimens exposed to the various HF solutions. These measurements provide information concerning the appearance, roughness, physical dimensions, hardness, elastic modulus, and reverse phase transformation activity of the various polysilicon specimens. In general, some of the chemistries produced time-dependent darkening or "staining" visibly seen on free surfaces, roughening and attack at grain boundaries, nano-scale pitting of the free surfaces, decrease in thickness, decrease in hardness and mechanical modulus, and diminished elbow and reverse excursion activity for those silicon specimens electrically connected to metal. Change in performance is attributed to the formation of a galvanic cell during the HF immersion, and the corresponding damage driven by an anodic current. The results here can be used to explain previous work, which focused on the change in performance of designated MEMS diagnostic structures.

The performance of structural films under cyclic loading conditions is a critical consideration when designing microelectromechanical systems (MEMS) based on silicon structural films. Empirical and theoretical studies have shown that silicon films are susceptible to fatigue at room temperature, but the underlying mechanistic origin is still an active topic of debate. This study characterized the fatigue behavior of electrostatically-actuated, n⁺-type, 2 μm thick polycrystalline silicon films with a thin native oxide. Electrostatically actuated resonators (natural frequency, f₀ ~ 40 kHz) were used to evaluate the stress-life fatigue behavior of the films in 30°C, 50% relative humidity (R.H.) air. These tests revealed delayed failure with increasing fatigue lives (up to 10¹¹ cycles) for decreasing stress amplitudes (down to 2.5 GPa). Long fatigue lives were associated with larger decreases in f₀ and very smooth failure origins that encompassed several grains. These findings are consistent with cyclic degradation of silicon films occurring within a surface reaction layer that forms upon exposure to the service environment and that evolves during fatigue loading.

It has been shown that the addition of single walled carbon anotubes (SWNTs) cause an increase in the resonance frequency of micromachined clamped-clamped structures. This is believed to be due to an increase in the effective stiffness of the micromachined structures due to the high Young's modulus of carbon nanotubes. These results were obtained in spite of a relatively poor control over the orientation and aerial density of the deposited SWNTs. Finite element simulations showed an increase in the resonance frequency of up to ~25% for the simulated devices. This increase in the resonance frequency of the bridges can be attributed to the high Young's modulus (~1TPa) of the carbon nanotubes.

Microsystems are potentially exposed to laser irradiation during processing, diagnostic measurements, and, in some cases, device operation. The behavior of the components in an optical MEMS device that are irradiated by a laser needs to be optimized for reliable operation. Utilizing numerical simulations facilitates design and optimization. This paper reports on experimental and numerical investigations of the thermomechanical response of polycrystalline silicon microcantilevers that are 250 μm wide, 500 μm long, and 2.25 μm thick when heated by an 808 nm laser. At laser powers above 400 mW significant deflection is observed during the laser pulse using a white light interferometer. Permanent deformation is detected at laser powers above 650 mW in the experiments. Numerical calculations using a coupled physics finite element code, Calagio, agree qualitatively with the experimental results. Both the experimental and numerical results reveal that the initial stress state is very significant. Microcantilevers deflect in the direction of their initial deformation upon irradiation with a laser.

Aluminum alloy beams having the same width but different lengths were made with semiconductor fabrication methods at the IPMS. The beams are clamped on one end with posts to the underlying plane. They are illuminated with 248 nm UV radiation created by an excimer laser and the bending was investigated in dependence on energy density and repetition rate. This behaviour is important for the development and the operation of MOEMS structures when used in UV applications. Ultraviolet radiation is used for lithography as well as material processing. The light-material interaction is well investigated for high energy densities (Ed) which are used for drilling holes or ablation of materials. In this work the influence of 248 nm low energy pulses (Ed < 200 μJ/cm²) on thin beams of aluminum alloys having a thickness of several hundreds of nanometer is analyzed. The frequency of the laser radiation is varied from 1000 to 2000 Hz. The beams have different lengths and are clamped on one end. Before illumination the beams are planar, after illumination the beams show a curvature which is related to internal stresses. The amount of curvature is dependent on the geometry of the beam, the energy density and the repetition rate of the radiation pulses. Also the relaxation behaviour of the curved beam is examined, i. e. the curvature change after the end of irradiation. The results will help to predict the practicability of materials for MOEMS in UV applications (mirror structures) and to understand their behaviour.

With their extremely low mass and volume, low power consumption and tight integration with electronics, MEMS sensors and actuators are extremely appealing for reducing the size and mass of spacecraft without sacrificing functionality. In view of the harsh and remote environment of space, reliability and qualification is the crucial issues that are holding back MEMS from playing a larger role in space applications. We examine how MEMS reliability is handled in commercial MEMS devices used in safety critical applications on earth and contrast the operating conditions on earth with those encountered during launch and in orbit. We explain the impact that vibration, mechanical and thermal shock, and radiation can have on MEMS devices fabricated using the most widespread silicon technologies. Accelerated tests adapted to space qualification are presented as a means to determine the major failure modes. Hermetic packaging is crucial to ensuring long-term reliability.

This paper presents the results of work by Teravicta Technologies to adapt semiconductor industry standards and practices to the qualification of RF MEMS switch components. This includes an overview of parametric test data including contact resistance and key RF performance indicators (insertion loss, return loss, and isolation) and reliability test results, identification of key failure modes, the development of failure accelerants and accelerated life test procedures, and final qualification results. Although some tests are unique to the RF MEMS switch, the methodology presented here provides a sound starting point for the development of qualification procedures for other MEMS devices.

Reliable operation of MEMS in liquid environments is an important design requirement for numerous MEMS devices in chemical, pharmaceutical, biomedical, consumer product, and defense industries. In this paper, reliability and long-term performance of microcantilevers in liquid environments is investigated. Single crystal silicon microcantilevers are subjected to long-term cyclic actuation (≈10⁸ -10⁹ cycles) in enclosures filled with two different liquids- de-ionized water and saline solution. Additionally, silicon microcantilevers are actuated in air to enable comparison of experimental data in air and liquids. The microcantilevers have an electroplated Permalloy layer and are magnetically actuated. The resonance frequency of the microcantilevers is periodically monitored to track changes in stiffness and mechanical performance. The microcantilevers are subjected to peak stresses ranging from 0-10 MPa, which are typical for MEMS applications like AFM tips, and resonating sensors. Since the peak stresses are small compared to the tensile strength of silicon (1-3 GPa), complete structural fatigue failure is neither expected nor observed. However, operational failures characterized by a gradual decrease in resonance frequency of the microcantilevers are observed in saline solution. Changes in resonance frequency of microcantilevers actuated in air and water were negligible to within the limits of experimental accuracy. These results demonstrate that an understanding of MEMS reliability in air cannot necessarily be extended to explain and predict device reliability in liquid environments.

We present a sensor fabricated with MEMS (Micro-Electro-Mechanical Systems) technology that upon immersion quickly measures fluid density and viscosity. The operational principal involves the influence of the fluid on the resonance frequency and quality factor of a vibrating plate oscillating normal to its plane. By performing measurements in liquids over a wide range of temperature (20 to 150 C) and pressure (0.1 to 75 MPa), we have demonstrated a maximum inaccuracy in our density and viscosity measurements of approximately +/- 1.5 % and +/- 10 % respectively, for fluids with densities between (0.6 to 1.5) g/cc and viscosities between (0.4 to 100) cP. Such measurements are required to determine the economic feasibility of recovering hydrocarbon from subterranean strata. There are numerous examples in the literature of sensors fabricated by the methods of MEMS that are claimed to measure both density and viscosity of fluids, but in most cases, the accuracy of such sensors is not been demonstrated in a wide range of fluids and moreover, their use in non-laboratory environments has not been proven.^1,2,3 Here we show that it is possible to design and package a sensor that can function with high accuracy in extreme environments while providing useful information.

Microelectromechanical systems (MEMS) radio frequency (RF) switches hold great promise in a myriad of commercial, aerospace, and military applications including cellular phones and phased array antennas. However, there is limited understanding of the factors determining the performance and reliability of these devices. Fundamental studies of hot-switched DC (gold versus gold) and capacitive (gold versus silicon nitride) MEMS RF switch contacts were conducted in a controlled air environment at MEMS-scale forces using a micro/nanoadhesion apparatus as a switch simulator. This paper reviews key experimental results from the switch simulator and how they relate to failure mechanisms of MEMS switches. For DC switch contacts, electric current had a profound effect on deformation mechanisms, adhesion, contact resistance (R), and reliability/durability. At low current (1-10 μA), junction growth/force relaxation, slightly higher R, and switching induced adhesion growth were prominent. At high current (1-10 mA), asperity melting, slightly lower R, and shorting were present. Adhesion increased during cycling at low current and was linked to the creation of smooth contact surfaces, increased van der Waals interaction, and chemical bonding. Surface roughening by nanowire formation (which also caused shorting) prevented adhesion at high current. Aging of the contacts in air led to hydrocarbon adsorption and less adhesion. Studies of capacitive switches demonstrated that excessive adhesion was the primary failure mechanism and that both mechanical and electrical effects were contributing factors. The mechanical effect is adhesion growth with cycling due to surface smoothening, which allows increased van der Waals interaction and chemical bonding. The electrical effect on adhesion is due to electrostatic force associated with trapped parasitic charge in the dielectric, and was only observed after operating the switch at 40 V bias and above. The two effects are additive; however, the electrical effect was not present until the surfaces were worn smooth by cycling. Surface smoothening increases the electric field in the dielectric, which results in trapped charges, alterations in electrostatic force, and higher adhesion. Excessive adhesion can explain decreased lifetime at high bias voltage previously reported with actual capacitive MEMS switches. Switch sticking, self actuation, failure to actuate, and self release can all be explained by the experimental results.

Reliability of electrostatically actuated ohmic contact type MEMS relays has been investigated. Multi-contact MEMS relays using electrostatic comb-drive actuators has been used in this study. The MEMS relays were fabricated using MetalMUMPs process, which uses 20 μm thick electroplated Nickel as the structural layer. A 3 μm thick gold layer was electroplated at the electrical contact surfaces. The overall size of the relay is approximately 3 mm x 3 mm. The relay consists of a movable main beam anchored to the substrate using two identical folded suspension springs. RF ports consist of five movable fingers connected to the movable main beam and six fixed fingers anchored to the substrate. Comb-drive actuators located at the top and bottom ends of the main beam enable bi-directional actuation of the RF contacts. An example MEMS relay with planar contacts of area 80 μm x 20 μm and a spacing of 10 μm between the movable and fixed contacting surfaces is discussed. Resistance versus applied voltage characteristics has been studied. For an applied DC bias voltage of 172 V, the movable fingers make contact with the fixed fingers. The resistance versus applied voltage characteristics has been measured for an applied bias voltage in the range of 172 V to 220 V. A multiscale rough surface contact model was used to estimate the actual electrical contact resistance versus applied force curve of these devices. Reliability testing has been carried out and the resistance variation of the MEMS relay over 80 x 10⁵ actuation cycles has been measured.

For state-of-the-art RF MEMS capacitive switches, a dielectric-charging model was constructed to predict the amount of charge injected into the dielectric and the corresponding shift in actuation voltage. The model was extracted from measured charging and discharging transient currents on the switch dielectric under different control voltages. The model was verified against the actuation-voltage shift under different control waveforms. Duty factor and peak voltage of the control waveform were found to be critical acceleration factors for the charging effects while actuation frequency is not an acceleration factor. The model is capable of predicting the actuation-voltage shift under complex control waveforms such as the dual-pulse waveforms. For RF MEMS capacitive switches that fail mainly due to dielectric charging, the model can be used to design control waveforms that can either prolong lifetime or accelerate failure.

This paper presents a mechanical model for a polysilicon double-ended tuning fork (DETF) that is implemented as force sensor. This sensor is integrated into a compliant, passive microgripper utilized in a microassembly of 3D MEMS structures. An expression for resonant frequency of DETF is derived. Theoretical model is introduced to analyze the quality factor (Q-factor) of the resonator. The DETF is found to have a maximum Q-factor of 863. In addition, the characteristics of the snap-fit interlocking mechanism are modeled analytically. An optimization scheme is employed to determine the optimal dimensions that provide a maximum reliable amplification factor (A-factor) of the microleverage mechanism. Based on the simulation, the maximum A-factor is 26.12. The model presented here permits a gauge factor (i.e., sensitivity) of 5000 ppm/μN at compressive force of 80μN and A-factor of 25. The superior results obtained support the feasibility of DETF as a resonant force sensor for microgripping applications.

Replicating the mechanical environments to which MEMS devices (Micro- Electro-Mechanical Systems) are exposed requires extreme test strategies. Acceleration levels in the 10's of thousands of g's is a normal occurrence in today's MEMS applications. Traditional test methods in use for over a half century are no longer adequate. New test methods are constantly required to meet the demanding quality and reliability levels of everything from emerging consumer applications to safety critical military and automotive systems.

Long-term reliability testing of Micro-Electro-Mechanical Systems (MEMS) is important to the acceptance of these devices for critical and high-impact applications. In order to make predictions on aging mechanisms, these validation experiments must be performed in controlled environments. Additionally, because the aging acceleration factors are not understood, the experiments can last for months. This paper describes the design and implementation of a long-term MEMS reliability test bed for accelerated life testing. The system is comprised of a small environmental chamber mounted on an electrodynamic shaker with a laser Doppler vibrometer (LDV) and digital camera for data collection. The humidity and temperature controlled chamber has capacity for 16 MEMS components in a 4x4 array. The shaker is used to dynamically excite the devices using broadband noise, chirp or any other programmed signal via the control software. Driving amplitudes can be varied to maintain the actuation of the test units at the desired level. The actuation is monitored optically via the LDV which can report the displacement or velocity information of the surface. A springmass accelerated aging experiment was started using a controlled environment of 5000 ppmv humidity (roughly 13% at room temperature), temperature of 29 °C, and ±80μm maximum displacement of the mass. During the first phase of the experiment, the resonant frequency was measured every 2 hours. From 114.5 to 450 hours under stress, measurements were taken every 12 hours and after that every 24 hours. Resonant frequency tracking indicates no changes in the structures for 4200 hours of testing.

Micro electromechanical systems (MEMS) and microsystems technologies are seeing increased consideration for use in military applications. Assets ranging from aircraft and communications to munitions may soon employ MEMS. In all cases, MEMS devices must perform their required functions for the duration of the equipment's mission profile. Long-term performance in a given scenario can be assured through an understanding of the predominant MEMS failure modes. Once the failure modes have been identified, standardized tests will be developed and conducted on representative devices to detect the potential for these failures. Failure mechanisms for MEMS devices in severe environments may include wear and stiction. While corrosion is not usually a concern for commercial MEMS devices, as they are made primarily of silicon, other materials, including metallics, are being considered for MEMS to provide enhanced robustness in military applications. When these materials are exposed to aggressive military environments, corrosion may become a concern. Corrosion of metallic packaging and interconnect materials may also present issues for overall performance. Considering these corrosion and degradation issues, there is a need to implement standardized tests and requirements to ensure adequate long-term performance of MEMS devices in fielded and emerging military systems. To this end, Concurrent Technologies Corporation has been tasked by the U.S. Army to initiate efforts to standardize test methods that have been developed under previous activities. This paper presents an overview of the MEMS activities under the standardization effort and the MEMS reliability test guidelines that have been drafted as a first phase of this effort.

Polytec presents its latest Micro System Analyzer for dynamic characterization of MEMS. Polytec continues to advance laser Doppler vibrometry since its introduction as a MEMS characterization tool in the 1990's and has introduced the first confocal vibrometer microscope with the Micro System Analyzer in 2005¹. Laser vibrometer out-of-plane resolution down to 0.2 pm / root 15.6 Hz is achieved by combination of highly sensitive Doppler shift measurement, digital decoding techniques and FFT signal analysis. Laser spot sizes less than 750 nm are measured for a high magnification 100X microscope objective and compared to theoretical limitations. The theoretical determination of the lateral resolution limit is discussed in detail with the implication that measurement of objects a couple orders of magnitude smaller (<10nm) can be measured. Example measurements that illustrate the unique measurement capabilities are performed on Sandia comb drive resonators and RF switches. New measurements on the Sandia comb drive show clear advances in resolution, including the ability to place and focus the measurement beam on very tiny structures such as a 2 micron comb finger. High Frequency measurements of comb drive deflection are made out to 2MHz. Furthermore, examples of stroboscopic in-plane response measurements show resolution better than 0.01 pixel. Transient response measurements are taken to determine critical performance parameters on an RF MEMS device developed by XComWireless. This includes measurements of snap down voltage, settling time, resonant frequency and three dimensional deflection shapes of transient time response.

We presented novel tool employing both low coherence interferometer, and spectrally resolved reflectometer sensor. We discuss compatibility of this metrology with high resolution Raman spectroscopy. We present measurements of the stability of the Raman spectrometer indicating that system is capable to measure stress in silicon with reproducibility corresponding to 1 MPa and below. We propose integrated tool for simultaneous measurement of stress and displacement of the micro-machined electromechanical devices. Furthermore we propose Raman system configuration allowing measurement of all independent stress tensor components on submicron scale.

The need to reach high and stable values of the Q-factor is one of the most important issues of resonant MEMS in order to make high-performance sensors. The Q-factor is strongly influenced by the internal environment of the MEMS packaging, by total pressure and by gas composition. The most experienced and technically accepted way to keep the atmosphere stable in a hermetically sealed device is to use a getter material that is able to chemically absorb active gases under vacuum or in inert gas atmosphere for the lifetime of the devices. MEMS hermetically bonded devices such as gyroscopes, accelerometers, pressure and flow sensors, IR sensors, RF-MEMS and optical mirrors requires getter thin film solutions to work properly. Getter technical solution for wafer to wafer hermetically bonded MEMS systems is PaGeWafer, a silicon, glass or ceramic wafer ("cap wafer") with patterned getter film, few microns thick. In this paper, first the theoretical evaluation of Q-factor of a MEMS resonant structure in presence of a getter film is investigated and compared to the results of a Residual Gas Analysis of the same MEMS resonant structure and with the conventional measurement of Q-factor. Using getter thin film technology, total pressures down to 10^-4 mbar with corresponding high and stable Q-factors have been achieved in MEMS resonant structures. We were therefore able to confirm that getter films can provide high Q-values, stability of sensor signal, performances stability during the lifetime, removal of dangerous gases like H₂ and H₂O in hermetically sealed MEMS resonant structures.

The pressure for reduction in cost and development time in new product, together with the need to pack more functions into smaller volumes in silicon chips has been fueling the system-on-chip (SOC) development. However, the current SOC technologies available essentially involve merging of chips fabricated with standard CMOS technology. These SOC technologies provide an integration solution with compatible fabrication processes that require little changes in process integration. There is no standard cost-effective solution to make 3D MEMS and optoelectronic devices together with CMOS on the same chip without compromising material compatibility, process complexity and system performance. One solution is to fabricate MEMS and CMOS components on separate wafer substrates and then stack them together with well isolated interconnected vias. In order to demonstrate this wafer-level 3D integration technology, a novel wafer-level bonding technology is being developed. This paper reports a detailed study of 3D MEMS (Micro Electro-Mechanical Systems) integration through multi-wafer anodic and polymeric wafer bonding. Different from previously reported wafer bonding studies, this study focuses on the optimization of the bonding process to improve the bonding quality.

Etching of quartz and glass for microsystems applications requires optimization of the etch process for high etch rates, high aspect ratios and low rms surface roughness of the etched features. Typically, minimum surface roughness of the etched feature accompanied with maximum etch rate and anisotropy are desired. In this article, we investigate the effect of different gas chemistries on the etch rate and rms surface roughness of the Pyrex(R) 7740 in an inductively coupled plasma reactive ion etching (ICP-RIE) system. The gases considered were SF6 and c-C4F8, with additives gases comprising of O2, Ar, and CH4. A standard factorial design of experiment (DOE) methodology was used for finding the effect of variation of process parameters on the etch rate and rms surface roughness. By use of 2000 W of ICP power, 475 W of substrate power, SF6 flow rate of 5 sccm, Ar flow rate of 50 sccm, substrate holder temperature of 20°C, and distance of substrate holder from ICP source to be 120 mm, we were able to obtain an etch rate of 0.536 μm/min and a rms surface roughness of ~1.97 nm. For an etch process optimized for high etch rate and minimum surface roughness using C4F8/SF6/O2/Ar gases, an etch rate of 0.55 μm/min and a rms surface roughness of ~25 nm was obtained for SF6 flow rate of 5 sccm, C4F8 flow rate of 5 sccm, O2 flow rate of 50 sccm, Ar flow rate of 50 sccm. Keeping all other process parameters the same, increasing the SF6 flow rate to 50 sccm resulted in an etch rate of 0.7 μm/min at an rms surface roughness of ~800 nm whereas increasing the C4F8 flow rate to 50 sccm resulted in an etch rate of 0.67 μm/min at an rms surface roughness of ~450 nm . Addition of CH4 did not contribute significantly to the etch rate while at the same time causing significant increase in the rms surface roughness. Regression or least square fit was used define an arbitrary etch rate number (Wetch) and rms surface roughness number (Wrms). These numbers were calculated by least square fit to the data comprising of ten correlated etch variables and enable quantization of etch parameters in terms of process parameters. The etch numbers defined in this work as function of process parameters present a very useful tool for the optimization, quantification and characterization of the dielectric etch processes developed in this work for MEMS fabrication and packaging applications.

This paper presents a new concept for bonding micro-parts with dimensions in the range of 50 μm to 300 μm. Two different kinds of adhesives - polyurethane adhesive foil and hot melt glue - were applied to a basic substrate by different techniques. The focused and concentrated hot gas stream softened glue which had been applied in a solid state. Micro-parts were then embossed in the softened glue, or covered and shielded by it. In this way, a rigid and compact bond was obtained after cooling. For the positioning of micro-parts (optical fibers), it has been necessary to manufacture adequate V-grooves. Finite element analyses using the ANSYS^TM program package were performed in order to evaluate parameters which govern the heat transfer to the adhesive and substrate respectively. Experimental results are in good agreement with results obtained by the numerical simulations. The advantages of this new approach are small system size, low capital costs, simple usage, applicability to many material combinations, easy integration into existing production lines, etc.

This paper presents hermeticity tests carried out on organically sealed MEMS micro-packages, using Fourier Transform Infra Red (FTIR) spectroscopy. Infrared spectroscopy, classically dedicated to material analysis, can be used to monitor the internal pressure of micro-packages, and to assess so their hermeticity. This technique was applied to BCB sealed micro-packages to study the influence of different parameters on their hermeticity properties, like the sealing ring dimensions or the addition of an external coating. The technique was validated for silicon micro-packages with a volume of 5 mm³ or more. Moreover, measurements carried out on micro-cavities with external parylene coatings have demonstrated that infrared spectroscopy measurements could be performed on MEMS packages with hermetic organic coatings.

In this work, a fabrication and temperature compensation analysis and electrowetting for the liquid lenses is proposed. The unique capability of controlling the lens profile during the electrowetting fabrication processes is successfully demonstrated for different ambient temperature environment. For a lens fabricated on a hydrophobic Teflon layer, it is found that when the applied voltage is increased, the focal length increases, and the curvature decreases. One challenge for the liquid lens is operating temperature range. Due to the environment temperature change, the ability of controlling the lens profile is analyzed and measured. The description of change in contact angle corresponding to the variation of ambient temperature is derived. Based on this description, we firstly derive the control of voltage vs. temperature for a fixed dioptric power. The control of lens during a focusing action was studied by observation of the image formed by the light through the transparent bottom of ITO glass. Under several conditions of ambient temperature change, capability of controlling the lens profile for a fixed focus is successfully demonstrated by experiments.

This paper compared the three different methods for determination of thin film modulus or MEMS applications: 1) scanning bending cantilever, 2) nanoindentation and 3) resonance frequency method. Surface profilometer was used to scan along the micro-machined cantilevers at different loads and produce the bending profile, from which the Youngss modulus can be extracted. Indentation profiled produced by Nano-indenter can deduce Young's modulus and hardness of the thin film materials. AFM vibrometer is used to detect the resonance of the thin film cantilever, from which the stiffness, and therefore the Young's modulus can be derived. The material properties of silicon nitride characterized by three methods are consistent and comparable with one another. The following MEMS materials: SiN, Ni, Ni/SiN bimorph, Nano-Diamond, SiC have been characterized and compared by using different method. Their advantages and disadvantages are also discussed.

This paper presented the method to detect the degradation level of insulation oil for transformer. Degradation of insulation oil for transformer is due to both mechanical and chemical deterioration. Metallic particle and organic material such as a dust are known as the main reason of mechanical deterioration. According to degradation and oxidation of insulation oil for the time of transformer operation, total acid number (TAN) will be increased, sludge will be appeared, and finally conductivity will be decreased. Designed sensor, which is an inter-digit capacitive type, was fabricated by using MEMS technology. Size of sensor is 9 mm (length) x 7 mm (width) x 1 mm (thickness). From the tested result, when the oil is aged, the capacitance increases and the impedance decreases. And the result shows the good proportionality with time.

Based on physical optics models of light propagation, scattering and transfer, a new fast computerized non-interferometric technique for 3D image reconstruction using wide-field microscopy is developed and tested that allows profilometry of M(O)EMS without compromising accuracy and spatial resolution attained by well established interferometry techniques. This non-destructive technique associated with using conventional microscope setups allows obtaining high-quality 3D profiles of structures like protecting membranes for packaging of MEMS with subsequent measurements of their mechanical properties. The comparison with conventional phase-shift interferometry-based measurements yielded encouraging results. The technique finds its potential whenever using of laser scanning confocal microscopy or phase-shifting techniques is compromised by the need to perform vibration-insensitive studies, or whenever stringent acquisition time requirements are of concern. This software technique being fully automatic, no changes to the existing hardware in the optical paths of microscopes is required. Moreover, the image acquisition protocol associated with the technique allows for simpler and cheaper measuring devices than interferometers and open the possibility for creating portable devices. The technique is tested on images acquired to control of packaging of MEMS by measuring deformations in MEMS protection membranes. The method's simplicity, its lower implementation cost and better insensitivity to vibrations with respect to established interferometric techniques makes it a potentially promising procedure for routine MEMS quality control in industrial environments.

In this paper, an analytical model of the mechanical behavior of a resonant beam sensor actuated by a bent beam thermal actuator is presented. The system is divided into two main subsystems: bent beam actuator and resonant beam sensor. Each subsystem is studied separately and then the model of the original system is derived based on the models of subsystems.