Proceedings Volume 4407

MEMS Design, Fabrication, Characterization, and Packaging

Uwe F. W. Behringer, Deepak G. Uttamchandani
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Proceedings Volume 4407

MEMS Design, Fabrication, Characterization, and Packaging

Uwe F. W. Behringer, Deepak G. Uttamchandani
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 30 April 2001
Contents: 7 Sessions, 50 Papers, 0 Presentations
Conference: Microelectronic and MEMS Technologies 2001
Volume Number: 4407

Table of Contents

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Table of Contents

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  • Modeling and Design
  • Processes and Fabrication Technologies I
  • Characterization, Packaging, and Interconnection
  • Optical MEMS
  • RF and Wireless MEMS
  • Bio/Chemical/Other MEMS and Actuators
  • Poster Session
Modeling and Design
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MEMS and mil/aero: technology push and market pull
Thomas H. Clifford
MEMS offers attractive solutions to high-density fluidics, inertial, optical, switching and other demanding military/aerospace (mil/aero) challenges. However, full acceptance must confront the realities of production-scale producibility, verifiability, testability, survivability, as well as long-term reliability. Data on these `..ilities' are crucial, and are central in funding and deployment decisions. Similarly, mil/aero users must highlight specific missions, environmental exposures, and procurement issues, as well as the quirks of its designers. These issues are particularly challenging in MEMS, because of the laws of physics and business economics, as well as the risks of deploying leading-edge technology into no-fail applications. This paper highlights mil/aero requirements, and suggests reliability/qualification protocols, to guide development effort and to reassure mil/aero users that MEMS labs are mindful of the necessary realities.
Model library and tool support for MEMS simulation
Peter Schwarz, Peter Schneider
FEM simulation is often a very time-consuming process in the design optimization of complex MEMS. System-level models with reduced order and accuracy have to be generated as a basis of a multi-domain system simulation. A powerful modelling methodology is needed to develop a library of MEMS models for different physical domains (mechanical, magnetic, fluidic, ...). The components are modelled as multi-terminal elements (multipoles) in generalized KIRCHHOFFian networks and are described with VHDL-AMS or other model description languages. Numerical model generation and parameterization is supported by a tool suite. Simulator coupling offers an additional possibility for analyzing heterogeneous MEMS.
Suspended substrate stripline structures evaluation for millimeter-wave circuits application
Jeffrey S. Fu, Chao Lu, Boon Chim Kwok, et al.
Suspended Substrate Stripline (SSS) is a printed circuit technology that can be used for both broadband and narrowband filters in highpass, lowpass, bandpass, bandstop and multiplexer form. It has been widely adopted in a variety of filter designs in the upper microwave and lower millimeter-wave frequency. This paper discusses two methods of designing a suspended substrate stripline bandpass filter. The first method is based on the design equations for the capacitive transmission line filter. The second method is based on the design procedure for broadside- coupled suspended stripline. Investigation has been made so as to determine which of these two methods is a more suitable choice for incorporating into the final finline mixer design operating at 35 GHz.
Experimental investigation, modeling, and simulations for MEMS-based gas sensor used for monitoring process chambers in semiconductor manufacturing
Ijaz H. Jafri, Frank DiMeo Jr., Jeffrey W. Neuner, et al.
There is a growing demand from the semiconductor industry for multi-component gas sensing for advanced process control applications. Microelectromechanical systems (MEMS) based integrated gas sensors present several advantages for this application such as ease of array fabrication, small size, and unique thermal manipulation capabilities. MEMS based gas sensors that are produced using a standard CMOS (Complimentary Metal Oxide Semiconductor) process have the additional advantages of being readily realized by commercial foundries and amenable to the inclusion of on-chip electronics. In order to speed the design and optimization of such integrated gas sensors, a commercial software package IntelliSuiteTM was used to model the coupled thermo-electro-mechanical responses of devices known as microhotplates. Models were built based on the GDSII formatted mask layout, process sequences, and layer thicknesses. During these simulations, key parameters such as device design and structure were investigated, as well as their effect on the resultant device temperature distribution and mechanical deflection. Detailed analyses were conducted to study the resonance modes for different sensor configurations, such as fixed-end and springboard arrangements. These analyses also included a study of the effect of absorbed material on device natural frequency. The modeling results from this study predict that the first three resonant frequency modes for these devices are in the 612 to 1530 kHz range for an all pinned device, and 134 to 676 kHz for a springboard arrangement. Furthermore, the modeling suggests that the resonant frequencies will decrease linearly as a function of increasing absorbed mass, as expected for a simple spring model. The change in resonant frequency due to mass absorption is higher for an all-pinned arrangement, compared to a springboard arrangement, with the second and third (twisting mode) showing the largest change. Thermo-electro-mechanical simulations were also performed for these devices, and the predicted mechanical deformations resulting from applied voltage compare favorably with experimental observations.
Component-based assistants for MEMS design tools
Kai Hahn, Rainer Brueck, Christian Schneider, et al.
With this paper a new approach for MEMS design tools will be introduced. An analysis of the design tool market leads to the result that most of the designers work with large and inflexible frameworks. Purchasing and maintaining these frameworks is expensive, and gives no optimum support for MEMS design process. The concept of design assistants, carried out with the concept of interacting software components, denotes a new generation of flexible, small, semi-autonomous software systems that are used to solve specific MEMS design tasks in close interaction with the designer. The degree of interaction depends on the complexity of the design task to be performed and the possibility to formalize the respective knowledge. In this context the Internet as one of today's most important communication media provides support for new tool concepts on the basis of the Java programming language. These modern technologies can be used to set up distributed and platform-independent applications. Thus the idea emerged to implement design assistants using Java. According to the MEMS design model new process sequences have to be defined new for every specific design object. As a consequence, assistants have to be built dynamically depending on the requirements of the design process, what can be achieved with component based software development. Componentware offers the possibility to realize design assistants, in areas like design rule checks, process consistency checks, technology definitions, graphical editors, etc. that may reside distributed over the Internet, communicating via Internet protocols. At the University of Siegen a directory for reusable MEMS components has been created, containing a process specification assistant and a layout verification assistant for lithography based MEMS technologies.
Design of a micro-Wankel rotary engine for MEMS fabrication
Kyle C. Jiang, Philip D. Prewett, M. C. L. Ward, et al.
This paper presents the design of a micro Wankel engine for deep etching micro fabrication. The micro engine design is part of a research program in progress to develop a micro actuator to supply torque for driving micro machines. To begin with, the research work concentrates on the micro Wankel engine powered by liquid CO2. Then, a Wankel internal combustion engines will be investigated. The Wankel engine is a planetary rotation engine. It is selected because of its largely 2D structure which is suitable for lithographic processes. The engine has been simplified and redesigned to suit the fabrication processes. In particular, the fuel inlet has been moved to the top cover of the housing from the side, and the outlet is made as a groove on the housing, so that the both parts can be etched. A synchronization valve is mounted on the engine to control the supply of CO2. One of advantages of the micro engines is their high energy density compared with batteries. A research study has been conducted in comparing energy densities of commonly used fuels. It shows that the energy densities of fuels for combustion engines are 10 - 30 times higher than that of batteries. The deigns of the micro Wankel engines have been tested for verification by finite element analysis, CAD assembly, and construction of a prototype, which proves the design is valid.
SPICE modeling of liquid capacitance in micromachined silicon capillaries
Paul V. Rainey, S. J. Neil Mitchell, Harold S. Gamble
This paper investigates modeling of the conductance of liquid in a microchannel, using SPICE. When more than one liquid is present, conductance monitoring is an effective technique to measure electroosmotic flow rates. In micromachined silicon capillaries, the technique is hampered by the capacitance that exists between the bulk fluid and the silicon substrate, and leakage currents due to the thin insulating oxide layer. A SPICE model is used to simulate conductance waveforms, by using MOS transistors to model the time dependant resistance of the channel. The simulation results are used to determine the capacitance and explain the conductance waveforms measured for micromachined silicon channels.
Electromechanical analysis of microelectromechanical structures and dynamic simulations of laterally vibratory microgyroscope
Jing Fang, W. B. Zhang, C. S. Wang, et al.
Multiplefield coupling is a typical characteristic of most mechanical structures in microelectromechanical system (MEMS), that involves the effects due to mechanical, electrostatic, magnetic, thermal actions, etc. Dynamic behaviors of the microstructures in those fields are of importance to estimate the design and manufacturing of the microsystem. In this paper, electromechanical analyses of some microstructures are presented based on a combination of boundary element method (BEM) and finite element method (FEM), to show the hybrid numerical technique not only useful to analyze the flexible deformation of the structures under electrostatic forces, but also important to evaluate the parameter variations of the electronic fields as the movement of the mechanical structures in those structronic systems. The simulation procedure is verified by both analytical solutions of some examples and experimental results of some microstructures driven by electrostatic field, in which the mechanical parameters such as the divergence of the deflection solution is related to the electrical characteristic such as the critical voltages of the electrostatic forces. Based on the structures involved in a laterally vibratory polysilicon gyroscope fabricated in our institute, the control equations of microgyroscope dynamics are presented, from that the response simulations of the microgyro are performed with the changes of the characteristic parameters, such as resonant frequency, quality factors, frequency disturbance, etc. Those results are useful for the optimal design of the structronic systems and the quality evaluation of the microprocessing, which are related to the rate measurement sensitivity and the output stability of the microsystem.
Processes and Fabrication Technologies I
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Characterization and optimization of deep dry etching for MEMS applications
Alexandra L. Rickard, Mark E. McNie
Deep dry etching of silicon has become an increasingly important process for a number of applications, including optical and microinertial MEMS. The Bosch process, with alternate etch and deposition steps, has become a dominant technique. Key responses include etch rate and depth uniformity. Two of the most important factors determining these are aspect ratio dependent etching (ARDE) and loading effects: both global and local. An RSM (response surface methodology) experiment was performed as the basis for subsequent optimization of the etch with respect to ARDE. The wall angle, etch rate and uniformity across the wafer were kept within predefined limits. By sacrificing some etch rate (approximately equals 25%), it was possible to achieve more than a 50% reduction in the difference in etch depth between 2 micrometers and 20 micrometers wide features. Loading effects, dependent on the exposed surface area of silicon, cause local or global variations in the etch rate. To investigate these effects, silicon wafers were patterned with different densities to change the global exposed surface area from 1% - 27%. Local density variations were used to investigate microloading. The etch rate decreased almost linearly with global exposed silicon area. Local variations showed a less pronounced effect.
Comparison of Bosch and cryogenic processes for patterning high-aspect-ratio features in silicon
Martin J. Walker
This paper compares the two leading techniques for etching deep into silicon, namely the `Bosch' process and a cryogenically cooled process. The Bosch process is introduced first. The process is described in some detail and details are given of particular hardware requirements. Finally, three classes of MEMS process are considered. For each application, relevant aspects of the Bosch process are discussed. Next, we more on to the `cryo' process. Again, this is described, together with hardware requirements. Three applications are presented for this process, with further comments relating to the process performance. Finally, in the conclusion, the two processes are compared and contrasted.
Fabrication of silicon sidewall profiles for fluidic applications using modified advanced silicon etching
Chi-fu Wu, Lars Erdmann, Kaigham J. Gabriel, et al.
In this work, we present a new deep etching sequence for the fabrication of circular cavities in straight silicon sidewalls. This approach allows alternating anisotropic/isotropic etches without affecting the profile generated in prior etching steps. This process sequence is crucial for realizing silicon structures that enable a variety of new applications, such as turbulence promoted liquid injector to disperse liquid effectively at the minimum injection pressure for electronic cooling, micro-evaporator or micro-combustors, surface enhancement (increase boiling nucleate sites) for micro-channel heat transfer, fluid mixing enhancer, isolation of electronic microstructures and release of mechanical microstructures.
Nd:YAG laser micromachining of SiC precision structures for MEMS
Micromachining of SiC with 1(omega) , 2(omega) , 3(omega) -Nd:YAG laser radiation with pulse durations in the ps to ns regime is performed in various processing gas atmospheres as a function of processing variables showing the influence of the heat and pressure load onto the precision of geometric structures generated. The physical and chemical processes involved in micromachining with laser radiation are characterized by a machine vision system and the produced structures are analyzed by profilometry, optical and electron microscopy as well as X- photoelectron spectroscopy. 3D microstructures are produced by scanning and turning the laser beam onto the material surface, width of structures < 100 micrometers and surface roughness < 2 micrometers , for example, require an overlap < 0.8 independent of the type of processing gas under investigation.
Profile control of SU-8 photoresist using different radiation sources
Zheng Cui, Derek W.K. Jenkins, Andreas Schneider, et al.
Patterning of thick layer SU-8 photoresist has been investigated with different radiation sources, including electron beam, X-ray, i-line stepper, UV mercury lamp with collimator, as well as two different types of UV contact maskaligner. Feature profiles with thickness up to 1 mm have been compared. Among all the radiation sources, x-ray exposure from a synchrotron radiation source is found to produce the best feature dimension control and has the highest feature aspect ratio. I-line stepper can also produce features with steep side wall but is limited to less than 200 micrometers resist thickness. The illumination parallelism is the key to control the resist profile, no matter what radiation sources are used. Other issues such as process condition become important when resist layer thickness is over 500 micrometers . Conditions for better profile control with thicker layer SU-8 photoresist are suggested.
Computational synthesis of lithographic mask layouts for silicon microcomponents
Stephanus Buettgenbach, Ulli Hansen, Lars Steffensen
In order to efficiently design complex micromechanical systems there is a growing demand for layout synthesis tools that directly derive the layout description from the device description. This paper outlines a systematic method of using genetic algorithms to synthesize the lithographic mask layout of micromachined silicon devices. The procedure has been implemented in the computer program OMEA, which calculates an optimal or semi-optimal layout description from the three-dimensional device description of the component. Currently, this method is applied to chemical deep etching of silicon. To model the structuring process the program makes use of a coupled etch simulator. Synthesis results show that the design engineer is enabled to take full advantage of the possible design space of the underlying process technology. The tool is an integrated part of the CAD environment BICEPS. In order to demonstrate the capability of the concept the design process of a spring actuator is described in detail.
Advances in silicon-to-glass bonding with laser
Michael J. Wild, Arnold Gillner, Reinhart Poprawe
In this work low temperature bonding of silicon and glass wafers for MEMS applications by the application of a Nd:YAG Laser using the transmission welding principle is examined. With this method the Laser beam is transmitted through the glass wafer and absorbed by the silicon at the silicon-glass interface. The resulting heated zone leads to locally selective bonding in spot and line shape with line width of 300 micrometers and less. The scope of the work is to characterize the Laser bonding (LB) technology and the quality of the produced silicon-glass joints. The continuous Laser power applied was between 12 and 30 W and the scribing velocity was between 50 and 500 mm/min. The measurements of the thermal load in the silicon during LB performed with micro-thermocouples show temperatures near the bonding zone around 300 degree(s)C for less than one second. The produced joints were found to have tensile strength between 5 and 10 MPa, which is comparable with other bonding methods. Hermetic tightness was proved with a helium leak detector and leak rates around 3(DOT)10-8 mbar(DOT)l(DOT)s-1 were found. Finally it will be discussed in which cases LB could be a supplement to anodic bonding, which is the state of the art bonding method for silicon-glass couples. Conclusively it can be said that locally selective LB is a novel method for MEMS packaging, with high bonding velocity, low thermal load for the joining partners and high bonding quality concerning strength and hermetic tightness.
Fine-grained polysilicon films with built-in tensile strain
Mohammed Obaidur Rahman, M. Ando
Polysilicon (P-Si) refers to the structure of the silicon crystals as they are applied to the glass substrate. Polysilicon crystals are larger, more regularly shaped and more uniformly oriented in comparison with amorphous silicon (A-Si) and thus polysilicon is the most widely used structural material in current microdevices that are manufactured by surface micro machining. Polysilicon film usually show s a compressive built-in strain field. Strain diagnostic structures are used to elucidate that polysilicon films with built-in tensile strain can be achieved. We have reported that Boron doping is an indirect method for strain measurement and lattice spacing changes can be modeled by (Delta) a equals a0 X (ri - rs/rs X (Ni/Ns) where ri and r2 can be regarded as a radius of impurities and silicon atoms and Ni and Ns are the concentration of impurities and silicon.
Micro stereo lithography for fabrication of 3D polymeric and ceramic MEMS
In this paper, the applications of Micro Stereo Lithography for polymer and ceramic based microstructures and MEMS are discussed with some examples.
Characterization, Packaging, and Interconnection
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Novel equipment for friction force measurement on MEMS and microcomponents
Martin Schmidt, Andreas Wortmann, Holger Luethje, et al.
The importance of micro actuators will increase dramatically in the near future. Micro actuators are only capable of generating low forces, therefore surfaces in dynamic contact must be tribologically optimized. Since component and thin film properties may differ from their bulk material behavior and in order to investigate the influence of the components' geometries, it is important to investigate the effect of friction in micro actuators under comparable test conditions. To enable such in-situ investigations two testing units have been designed and built up at the IMT and IST. We report on the design of these devices.
Bio/chemical microsystem designed for wafer scale testing
Anders M. Jorgensen, Klaus B. Mogensen, Weimin Rong, et al.
We have designed a bio/chemical microsystem for online monitoring of glucose concentrations during fermentation. The system contains several passive microfluidic components including an enzyme reactor, a flow lamination part and a detector. Detection is based on the reaction of hydrogen peroxide, that is produced from glucose in an enzyme reactor, with luminol. This chemiluminescent reaction generates light that is detected by an integrated back-side contacted photodiode array. Various tests during fabrication are outlined with the emphasis on microwave detected photo conductance decay. The presented microsystem has both fluidic and electrical connection points accessible from the backside. This allows simultaneous testing of both fluidic and electrical parts before dicing the wafer.
Breakdown voltage behavior of electrostatic microactuators
Resh S. Dhariwal, Mohamad Fizal Ahmad, Marc P.Y. Desmulliez
Apparatus designed and built in-house has been used to study the breakdown voltage for different electrode configurations and for wobble micromotor surfaces at separations of less than 100 micrometers. The wobble micromotors studied have a diameter of 4 mm with a height of 200 micrometers and have been designed at Heriot-Watt University and manufactured using the UV-LIGA process. Results are presented for the breakdown voltage between the segments of the micromotor and also between the inner stator, outer stator and bearing. Results are also presented for the breakdown voltage between metallic flat circular and spherical electrodes having diameters of 10 and 20 mm. It is observed that the electrode area and the electrode configuration are important parameters, which affect the value of the breakdown voltage. Reducing the electrode area was found to increase the breakdown voltage. The spherical electrode configuration was found to increase the breakdown voltage, while a rod configuration, analogous to the segments of the micromotor, reduces the breakdown voltage. The breakdown voltage between the stator segments and the bearing was found to be lower than the expected theoretical value based on the separation of these surfaces.
3D-CSP: an innovative packaging method based on RMPD
Helge Bohlmann, Reiner Goetzen, Andrea Reinhardt
A major bottleneck in the applications of microtechnologies are packaging and interconnection techniques. 3D-CSP (3D-Chip-Size- Packaging), which is based on RMPDTM, solves an extremely wide range of packaging problems. RMPDTM and 3D-CSP are discussed and applications presented.
Method of localized and low-temperature wafer bonding for microsystem packaging
S.C. Shen, Chengtang Pan, Hwai-Pwu Chou
This paper presents a novel approach for bonding technique based on the concept of patternable and low temperature process. This method especially is suitable for the design of microstructure by surface micromachining. By this way, the bonding can be solved. The patternable intermediate of photoresist is applied to conduct wafer-bonding experiment. SU-8 is selected as intermediate layer the thickness of SU-8 not only can be easily controlled, but also can be patterned into any-shape by the technique. Furthermore, this method provides smooth intermediate pad to contact for bonding. The experiment of wafer-to-wafer intermediate bonding was conducted. The preliminary results show that the influences of high temperature, electric field, and void can be avoided. The tensile stress test is shown the bonding strength up to 216 kg/cm2 can be reached.
Optical MEMS
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MEMS hybridization: bridging the free-space gap
Paul Blair, Duncan McMillan, Jean Podlecki, et al.
The increasing demand for bandwidth is driving the development of new paradigms within the fibre optic telecomms industry and leading to the generation of a new range of optical components. One route being taken is the hybridization of discrete components into a single package to realize high functionality subsystems. The combination of MEMS with light guide technology is one hybridization pathway that is showing considerable potential. In the drive for novel functionality it is paramount that the performance parameters are not compromised, nor should the hybridization of discrete components lead to increased manufacturing and packaging complexity and reliability issues. A theoretical and experimental study of integration schemes has shown that it is possible to integrate MEMS components with light guide technologies using just simple air gaps while preserving key performance parameters.
Investigation of improved designs for rotational micromirrors using multiuser MEMS processes
Julianna E. Lin, Feras S. J. Michael, Andrew G. Kirk
In recent years, the design of rotational micromirrors for use in optical cross connects has received much attention. Although several companies have already produced and marketed a number of torsional mirror devices, more work is still needed to determine how these mirrors can be integrated into optical systems to form compact optical switches. However, recently several commercial MEMS foundry services have become available. Thus, due to the low cost of these prototyping services, new devices can be fabricated in short amounts of time and the designs adapted to meet the needs of different applications. The purpose of this work is to investigate the fabrication of new micromirror designs using the Multi-User MEMS Processes (MUMPs) foundry service available from Cronos Integrated Microsystems, located in North Carolina (USA). Several sets of mirror designs were submitted for fabrication and the resulting structures characterized using a phase-shifting Mirau interferometer. The results of these devices are presented.
Wafer scale packaging for a MEMS video scanner
Mark P. Helsel, Jon Barger, David W. Wine, et al.
Miniaturized scanners have proven their usefulness in a host of applications including video display, bar code reading, image capture, laser printing and optical switching. In order for these applications to reach fruition, however, the MEMS scanner component must be packaged in a manner that is compatible with the volume manufacturing capabilities of the technology. This paper describes a process that was developed to package an SVGA resolution (800 X 600) biaxial video scanner. The scanner is designed for a head mounted display product, targeted to the medical and industrial markets. The scanner is driven magnetically on one axis and capacitively on the other axis. The first level wafer scale package described here incorporates the capacitive drive electrodes into the mounting substrate. The substrate wafer and the device wafer are then bonded using a glass frit sealing technique. Finally, the scanner and substrate are hermetically sealed into a metal can at reduced pressure.
New actuation structure for the deformation of continuous mirrors for adaptive optics
Emmanuel Quevy, Lionel Buchaillot, Dominique Collard
This work demonstrates a novel technique for the realization and the actuation of continuous-membrane for adaptive optic applications. This original device exhibits, for the first time, both positive and negative membrane deflection with individual pixel displacement of +/- 10 micrometers , which is one order of magnitude larger than usual approaches, without diffractive interference.
RF and Wireless MEMS
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Silicon MEM technology for millimeter-wave applications
Katia M. Grenier, D. Dubuc, Patrick Pons, et al.
This paper presents a new silicon technology that is used for innovative components such as a MicroElectroMechanical Systems for microwave and millimeter-wave applications. This technology is based on two different bulk and surface silicon micro- machining processes. The former one, the bulk micro-machining, is well fitted to the realization of low loss microwave circuits suspended on a thin membrane, whereas the surface one allows the realization of actuable devices. This confers to the structure an interesting MEM behavior particularly important in millimeter- wave applications. As a demonstration of the advantage of combining surface and bulk micromachining a low loss (< 0.1 dB at 100 GHz), high isolation (approximately equals 30 dB at 10 GHz) capacitive switch has been designed, processed and measured. A distributed switch with enhanced performance has also been investigated.
Infrastructure needs for RF MEMS production
RF MEMS activities until now has been driven by universities. For production of these enabling components a new industry is needed. RF MEMS processing is very different and even incompatible with traditional IC processing for at least two reasons: (1) the metals used are unfamiliar and often forbidden in semiconductor processing, (2) making free standing structures needs a specialist knowledge of the properties and the processing of these metals. Even for experienced MEMS institutes/companies making these products is a challenge, and as a result, they can only fulfill the first demands of the customers: i.e. testing of the possibilities of this new technology and proving its feasibility. These first players are generalists, having a broad knowledge of MEMS processes and applications. However, upcoming demand from the market asks different capabilities. Most customers nowadays are not looking for a few `breadboard' samples based on the latest available processes. They need non-technical capabilities like: reproducibility, reliability, timely delivery, etc. Much work has to be done to fit the design demands into the foundries and bring the production processes to a level comparable to mature industries such as semiconductor or magnetic head industries.
Low-cost in-line phase shifter (IPS) using electrostatic MEMS for large antenna arrays
Seong-Hwoon Kim, Jeff Dean, Leslie D. Kramer
This paper describes the In-line Phase Shifter concept and presents some preliminary results of implementing a cost effective phase shifter utilizing electrostatic MEMs actuators.
Wireless surface acoustic wave and MEMS-based microsensors
The integration of SAW (Surface Acoustic Wave), MEMS and required microelectronics and conformal antennas to realize programmable microsensors suitable for many engineering and biomedical applications will be presented in this talk. This unique combination of technologies results in novel conformal sensors that can be remotely sensed by a wireless communication system with the advantage of no power requirements at the sensor site (passive sensor). The required features in many of these applications are high precision, wide dynamic range and wide frequency range. MEMS-SAW based devices presented possess typical advantages of MEMS sensors including the additional benefits of robustness, excellent sensitivity, surface conformability and durability. After a brief overview of SAW sensors and MEMS, the paper is focused on the design and fabrication of MEMS devices for a few engineering applications such as accelerometer and gyroscopes for automobile, inertial navigation sensors and tire pressure sensor.
MEMS technologies for rf communications
Qun Wu, B. K. Kim
Microelectromechanical system (MEMS) represents an exciting new technology derived from the same fabricating processes used to make integrated circuits. The trends of growing importance of the wireless communications market is toward the system with minimal size, cost and power consumption. For the purpose of MEMS R&D used for wireless communications, a history and present situation of MEMS device development are reviewed in this paper, and an overview of MEMS research topics on RF communication applications and the state of the art technologies are also presented here.
Bio/Chemical/Other MEMS and Actuators
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Electrothermal modeling of silicon PCR chips
Zheng Cui, Zhan Zhao, Shanhong Xia
Polymerase chain reaction (PCR) on a microchip has drawn considerable attention in recent years. Although a microchip can have must fast heating and cooling rate, the delicacy in its structure makes the PCR experiment difficult and cracks often occurs particularly for the thin membrane type of PCR chips. Electrothermal modeling of PCR chips is presented using commercial MEMS software tool IntelliSuiteTM, with the aim of identifying the problems encountered in experiment and finding an optimum chip structure. Heating characteristics of four different heater designs have been compared, so have the PCR chambers with fixed frame and with suspended frame. The thermal stress analysis has shown that the structure and heater design can make significant difference in heating characteristics and in reducing the failure of PCR chips. The computer simulation has confirmed what has been found in experiment the reason of membrane cracks. Improvement in PCR chip design has been proposed.
Microfabrication and application of reservoir pins for liquid transfer in biotechnology
Jonathan Pearson, David F. Moore, William I. Milne, et al.
Microarraying involves laying down genetic elements onto a solid substrate for DNA analysis on a massively parallel scale. Microarrays are prepared using a pin-based robotic platform to transfer liquid samples from microtitre plates to an array pattern of dots of different liquids on the surface of glass slides where they dry to form spots diameter < 200 micrometers . This paper presents the design, materials selection, micromachining technology and performance of reservoir pins for microarraying.
Fabrication of microshutter arrays for space application
Mary J. Li, I. S. Aslam, Audrey J. Ewin, et al.
Two-dimensional microshutter arrays are being developed at NASA Goddard Space Flight Center for the Next Generation Space Telescope (NGST) for use in the near-infrared region. Functioning as object selection devices, the microshutter arrays are designed for the transmission of light with high efficiency and high contrast. The NGST environment requires cryogenic operation at 45K. Arrays are close-packed silicon nitride membranes with a pixel size of 100 X 100 micrometers . Individual shutters are patterned with a torsion flexure permitting shutters to open 90 degrees with a minimized mechanical stress concentration. The mechanical shutter arrays are fabricated with MEMS technologies. The processing includes a RIE front-etch to form shutters out of the nitride membrane, an anisotropic back-etch for wafer thinning, and a deep RIE (DRIE) back-etch down to the nitride shutter membrane to form frames and to relieve shutters from the silicon substrate. Two approaches for shutter actuation have been developed. Shutters are actuated using either a combined mechanical and electrostatic force or a combined magnetic and electrostatic force. A CMOS circuit embedded in the frame between shutters allows programmable shutter selection for the first approach. A control of row and column electrodes fulfills shutter selection for the second approach.
Novel fabrication process for 3D meander-shaped microcoils in SU-8 dielectric and their application to linear micromotors
Volker Seidemann, Stephanus Buettgenbach
This paper reports on an optimized fabrication process for three dimensional coil structures such as meander or helical coils wound around in plane magnetic structures. The process consists of UV depth lithography employing AZ4562 and SU8 photo resists and electroplating of copper and nickel-iron. Furthermore SU8 is used as the embedding dielectric due to its excellent planarization properties and high structural aspect ratio. Special emphasis was laid on the decrease of via interconnect resistance by electroplating the vias and upper conductors in a single step thus avoiding a large number of resistive interfaces. This was achieved by sacrificial wiring and structured seed layers. The developed technology is applied to a variable reluctance micro motor with a novel design that avoids high friction. The presented concept makes use of a stator traveler configuration generating complementary attraction forces. The technology and design concept is presented and first results are demonstrated.
Design and performance of a polysilicon surface micromachined microengine realized with arrays of asymmetrical electrothermal microactuators
Edward S. Kolesar Jr., Matthew D. Ruff, Simon Y. Ko, et al.
Several microactuator technologies have recently been investigated for positioning individual elements in large-scale microelectromechanical systems (MEMS). Electrostatic, magnetostatic, piezoelectric and thermal expansion are the most common modes of microactuator operation. This research focuses on the design and experimental characterization of two types of asymmetrical MEMS electrothermal microactuators. The motivation is to present a unified description of the behavior of the electrothermal microactuator so that it can be adapted to a variety of MEMS applications.
Poster Session
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Operation cycle modeling for electrostatic-type microrelay
Georgy I. Efremov, Nikolay Ivanovich Mukhurov
Micro-switching devices, in particular, micro-relays occupy a prominent place in the family of MEMS/MOEMS devices. Such devices offer an advantage of insignificant power consumption and good compliance with requirements of integrated microelectronics technology. This paper presents theoretical analysis of the micro-relay operation cycle as a basic process for designing various miniature threshold devices. It is known that operation of electrostatic micro-relays is the result of interaction of active electrostatic forces arising between control circuit electrodes and reactive mechanical forces created by elastic holders of a movable electrode.
Modeling and simulation of a silicon microdiaphragm piezoresistive pressure sensor using finite element analysis (FEA) tools
A. J. Pang, Marc P.Y. Desmulliez
In this paper, diaphragm deflection and output voltage obtained by applying a series of pressure loads to a silicon piezoresistive micro-diaphragm with built-in edges are presented. A silicon pressure sensor with diaphragm of 1 mm in length and 10 mm in thickness is modelled. Finite Element Analysis results are compare with other experimental and numerical results. A series of simulation on sensor with diaphragm of 3.4-mm in length and various thicknesses, meshing densities and resistor lengths is performed. Discussion of results are based upon (1) effect of different resistor lengths on output voltage and sensitivity and (2) effect of different diaphragm thicknesses on output are presented.
High-level simulation of an electrostatic micromotor
Aitor Endemano, Matthew Dunnigan, Marc P.Y. Desmulliez
To date, electrostatic microactuators have mostly bee simulated using tools that involve accurate but complex finite element analysis methods. When such an analysis forms part of a full electro-mechanical simulation, the quantity of computations necessary is excessively demanding whenever rapid results are required. High-level simulation of electrostatic actuation that includes closed-form expressions of the static and dynamic behaviors of the device, seems a best alternative for rapid prototyping. The work presented in this article is focused on the high-level simulation of a particular class of actuators, the wobble electrostatic micromotor. The high-level simulation of the motor and its surrounding electronics (control loop, power supply, sensory circuitry) shows aspects of its performance that cannot be seen by any other means. As in conventional electronic systems, this approach also offers a faster and cheaper way of designing and debugging system models, by exchanging Intellectual Property blocks across different designer teams.
Integrated microsystems in standard CMOS technology with applications in the field of chemical sensors
In this paper some recent results, regarding the research activity currently in progress in the field of MEMS at the DEES, University of Catania, are reported. In particular some microsystem prototypes, realized by using a standard CMOS process (AMS 0.8 micrometers CMOS) through the EuroPractice service, are described. A novel IC has been realized, it contains several different structures designed both for particular applications and for technology characterization purposes. A set of devices has been realized through 'front side bulk micromachining' and some other novel structures where the polysilicon layer is used as sacrificial layer have been investigated. In order to ensure fully compatibility with CMOS electronics, a wet etching process has been performed by using TMAH. Characterizations of the wet etching process are being performed in order to exploit the absence of crystallographic structure in polysilicon to allow for isotropic etching micromachining. Some applications of Microsystems in different fields are also presented.
High-volume production cost savings methods in MEMS fabrication
Joe Brown
Aligned substrate bonding has developed into high volume production solutions that meet the ever-increasing needs for fabrication and performance criteria. This presentation will update the audience on recent developments for high volume production of MEMS/MST.
Coplanar waveguides on SOI and OPS substrates
Harold S. Gamble, Kam On Leong, Syed H. Raza, et al.
Silicon is being investigated as a low cost, low loss substrate for MMICs. The conflicting requirements of low resistivity silicon for active device fabrication and very high resistivity silicon for low microwave transmission losses have been met by two differing technologies. In one technology the low loss CPW lines are fabricated on oxidized porous silicon (OPS) formed on 1-3 (Omega) -cm (100) silicon substrates. In the other technology SOI substrates are produced by bonding 1-3 (Omega) -cm silicon wafers to 2-4 k(Omega) -cm handle wafers which are covered with a layer of silicon dioxide on a layer of polycrystalline silicon. To minimize bowing of the silicon substrate it was found necessary to limit the OPS thickness to 10 micrometers . For the CPW lines the microwave losses on the OPS substrates were 8.5 dB/cm at 30 GHz and on the SOI wafers they were 2.2 dB/cm. The SOI wafers offer considerable promise for reliable low cost low loss MMIC substrates.
Novel silicon bulk micromachining process for submillimeter rectangular waveguide fabrication
Micromachining of ultra-high frequency waveguide structures requires etching with vertical sidewalls and flat bottoms simultaneously. The required geometries can be difficult to achieve using a single-step orientation dependent etching (ODE) process without incurring a severe mask-undercutting penalty. This may inhibit the production of isolated convex structures, such as the central pillars that are required to couple radiation into the waveguide. In this paper we will described a new technique for ODE of deep, vertical sidewall structures in (100) Si with reduced undercut etching. The process uses a two stage KOH/IPA etch with a mask pattern that is designed to compensate for the differing etch rates on the Si planes. To date we have achieved overall etch depths of 350 microns, with a lateral undercut of as little as 275 microns, compared with a 350 micron undercut for a single-stage etch. The sidewalls are at exactly 90 degrees to the surface of the (100) Si, and the bottoms of the trenches are smooth and flat. Using the process we have also been able to routinely fabricate isolated, square pillars as small as 50 X 50 square microns, and over 300 microns high. The process enables structures to be made that might previously only have been possible with high-density-plasma dry etch techniques. The new technique has clear advantages of low cost and high throughput.
Development of a laser micromachining toolbox and its application to the production of 3D microstructures
As laser micromachining has developed in recent years, there has emerged a need for the simplification of the process to produce MEMS structures where the stages of manufacture do not require an in-depth knowledge of laser micromachining techniques. This paper describes the initial stages of such an approach - the laser micromachining 'toolbox' - which enable the optimum machining choices to be made from various design requirements. Some of the elements of the toolbox are introduced and quantified in the particular case of excimer laser micromachining. These features are then used to produce a 3D microstructure to demonstrate the capabilities of this approach. Future developments in this area are discussed.
Micro-CT for nondestructive 3D reconstruction of MEMS and sensors
The combination of x-ray microscopy with tomographical reconstruction allows getting 3D information about the internal microstructure by a non-destructive way. A desktop high- resolution X-ray micro-CT (microtomograph) has been developed for 3D reconstruction and realistic visualization of the internal microstructure with spatial resolution in the micron range. The instrument was successfully tested for inspection, defectoscopy and back engineering in MEMS and integrated multichip sensors.
Heterogeneous substrates for high-temperature and optical applications
Manfred Reiche, V. Dragoi, M. Alexe, et al.
Further applications of MEMS require the combination of different materials in order to combine different functions in one and the same system. Besides conventional techniques (layer deposition methods) semiconductor wafer direct bonding is expected to be an effective method to produce heterogeneous materials. Different examples for optical and high-temperature applications are presented (Si-based heterostructures, Si/GaAs heterostructures).
Self-parking fiber and self-latching vertical mirror for fiber optical switch array
S.C. Shen, Cheng-Tang Pan, Hwai-Pwu Chou
The paper presents an innovative concept of self-parking ideal in v-groove and self-latching vertical mirror on the suspension diaphragm with technique out of plane fiber-optical switch arrays was fabricated. The self-parking ideal offers an integration by which the distance between optical fiber and mirror can be minimizes. The self-latching vertical mirror located on the suspension diaphragm that is supported by four cantilever beams. At first, it is achieved by bulk micromachining and is ablated by mask projection of 248 nm excimer laser. The vertical mirror structure was fabricated by thick photoresist as SU-8 through UV lithography and then sputters gold films. The fiber-optical switch solves in plane micro-optical that require large moving space, microassembly problem of fiber to mirror distance and reducing the roughness of mirror surface. In the experiment, out of plane micro-optical switch are successfully achieved by above key process. By the measurement of roughness of mirror must be less than 20 nm rms. The reflectivity of the gold films mirror by a wavelength of 1310 nm is higher than 85%. The micro-optical switch has maximum displacement 48 micrometers and switching time is below 0.4 ms with driving voltage 100 V DC.
Transport in a deformable microchannel flow
W. Kwang-Hua Chu, Jing Fang
Investigation of the entrainment of fluids induced by a wavy deformation along walls in a confined falt-plane microchannel is conducted by using the relaxed Navier-Stokes model with velocity- slip boundary conditions. Both no-slip and slip flow cases are presented with the former ones matched with the previous results. Flow patterns tuned by critical reflux values a0 and Reynolds number are demonstrated especially for the free pumping case. a0 decreases due to slip-flow effects after we compared them with no-slip cases.
Microwave frequency acoustic resonators implemented on monolithic Si/AIN substrates
Cinzia Caliendo, Enrico Verona, Alessandro Cimmino
Basing on the performances of high quality AlN piezoelectric films, acoustic resonators exploiting the propagation of both surface and bulk waves (SAW, BAW) and operating at microwave frequencies have been studied and experimented. Because of the high values of the acoustic wave velocities in both AlN and Si substrates, high frequency operations can be easily achieved. The expected frequency limit can be so high as 5 GHz and 10 - 15 GHz for SAW and BAW devices, respectively.
Vertical hall sensor of high sensitivity and excellent confinement fabricated on the (110) silicon substrate
Hong-Wei Chiu, Sheyshi Lu, Hai Lan
A vertical Hall sensors fabricated on a (110) silicon substrate with good sensitivity and carrier confinement was demonstrated. It is known that sensitivity of a Hall sensor is related to carrier confinement and the thickness of a Hall plate. However, traditional vertical Hall plates fabricated on a (100) silicon substrate have difficulty in achieving high aspect ratio of the depth (corresponding to the width of a Hall plate) to the width (corresponding to the thickness of a Hall plate) of an etched `wall' for carrier confinement. Wet etching tends to form sloped sidewalls due to the formation of V-grooves on (100) silicon substrates while drying etching takes much time to form deep trenches. Therefore we propose to fabricate vertical Hall plates fabricated on (110) silicon substrate in this paper. It is well known that deep vertical walls can be fabricated on (110) silicon substrates by TMAH an-isotropic etching, which means that vertical Hall plates with high aspect ratio can easily formed by this simple wet etching. Experimental results from the vertical Hall sensors on (110) substrates showed a sensitivity of 64.1 V/AT, which is higher than that obtained by micro-machined vertical Hall sensor on (100) substrate.