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A microfabricated floating-element shear stress sensor using wafer-bonding technology

Journal of Microelectromechanical Systems 1992年第2期1卷 89-94页

作者： Shajii, Javad Ng, Kay-Yip Schmidt, Martin A. Microsystems Technology Laboratories Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA USA

A microfabricated floating-element (120 μm 15; 140 μm 15; 5 μm) liquid shear stress sensor has been developed using wafer-bonding technology. The sensor has been designed for high shear stresses (1-100 kPa) a... 详细信息

A microfabricated floating-element (120 μm × 140 μm × 5 μm) liquid shear stress sensor has been developed using wafer-bonding technology. The sensor has been designed for high shear stresses (1-100 kPa) and high-pressure environments (up to 6600 psi) and utilizes a piezoresistive transduction scheme. Analytical and finite-element method (FEM) modeling have been performed to predict the sensor response. The sensor has been tested for both its mechanical integrity in high-pressure environments and its output response in the controlled environment of a cone and plate viscometer. The processing steps in the fabrication of the sensor, the analytical and FEM modeling, the experimental procedures, and the results of the experiments are described.

关键词： Piezoelectric transducers

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An Integrated Airgap-Capacitor Pressure Sensor and Digital Readout with Sub-100 Attofarad Resolution

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Journal of Microelectromechanical Systems 1992年第3期1卷 121-129页

作者： Kung, Joseph T. Lee, Hae-Sueung Microsystems Technology Laboratories Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 United States Microsystems Technology Laboratories Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 United States

The fabrication and charaterization of an integrated airgap-capacitor pressure sensor is presented. The capacitor fabrication process uses standard IC processing to create NMOS circuits, and an added polysilicon layer to create poly-to-n 4- capacitors with a 0.6-pm-thick dielectric using deposited oxide. Subsequent processing is used to etch the oxide under the polysilicon from the back of the substrate (formed using bulk etching), to produce deformable, parallel-plate, airgap capacitors on the front-side alongside MOS circuits. Sensor chips are fabricated using 100 x 100 μm, 100 fF airgap capacitors with on-chip circuitry. The sensor chip is a part of a capacitive measurement system that uses a charge-redistribu-tion sense technique to achieve very high capacitance resolution. The pressure sensor chips were characterized versus applied pressure in the 0–240 kPa (0–35 psi) range using optical phase measurement interferometry to measure deflection and shape, and charge-redistribution sense techniques to measure capacitance change. Measurements indicate a sensitivity of 0.93 mV/kPa (6.40 mV/psi) with a deflection of 10 nm/kPa (70 nm/psi) from 0–69 kPa (0–10 psi). Standard deviations indicate a static pressure resolution of 0.54 kPa (0.078 psi), which translates to 30 attofarads at a sampling frequency of 11 kHz. © 1992 IEEE

关键词： MOS capacitors Circuits Sensor phenomena and characterization Fabrication Air gaps Capacitive sensors Semiconductor device measurement MOS devices Dielectrics Sensor systems

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A computer-aided design system for microelectromechanical systems (MEMCAD)

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Journal of Microelectromechanical Systems 1992年第1期1卷 3-13页

作者： Senturia, Stephen D. Harris, Robert M. Johnson, Brian P. Kim, Songmin Nabors, Keith Shulman, Matthew A. White, Jacob K. Microsystems Technnlnov Laboratories Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 United States Power Products Division Systems Technology Division IBM Corp. Endicott. Cambridge NY United States Microsystems Technology Laboratories Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology MA 07139 United States Research Laboratory of Electronics Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 United States Microsystems Technology Laboratories Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge Redmond. MA. United States Microsoft Corp. WA 98052 United States

The authors describe the MIT Microelectromechanical computer-Aided Design system (MEMCAD), in which selected commercial software packages are linked with specialized database and numerical programs to allow designers to quickly perform both mechanical and electrical analyses of structures either described directly, or derived from the design specification (mask data plus process flow). The system architecture, the various modules, and their present status are described, and present system performance is demonstrated with several examples.

关键词： Electromechanical Devices

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A COMPACT, INEXPENSIVE APPARATUS FOR ONE-SIDED ETCHING IN KOH AND HF

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SENSORS AND ACTUATORS A-PHYSICAL 1991年第3期29卷 209-215页

作者： KUNG, JT KARANICOLAS, AN LEE, HS Microsystems Technology Laboratories Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 U.S.A.

Silicon micromachining often requires the selective removal of either surface or bulk layers of material from substrates. Often it is advantageous to protect one side of a substrate while the other side is exposed to the etchant. Sometimes an etch can take as long as 8-10 h at temperatures as high as 80-degrees-C, such as in wet etching of bulk silicon in potassium hydroxide (KOH) solution. Other times, the etch may be at room temperature, and there may be prolonged periods of exposure to concentrated hydrofluoric acid (HF) when removing sacrifical layers of oxide. Both KOH and concentrated HF are effective in etching silicon and silicon dioxide respectively, but there is difficulty in finding suitable materials that mask these etchants for long periods of time. Silicon nitride is a good mask for KOH, but is deposited at a relatively high temperature (800-degrees-C), while concentrated HF tends to delaminate or etch most materials. This makes it difficult to protect layers on silicon wafers after any metal deposition. This paper describes a system designed to wet etch substrates from one side only, protecting the front side to a high degree. The one-sided etching concept is introduced, followed by the design of the apparatus with variations on the basic concept. This is followed by a particular implementation in a KOH etching system. Also described as part of the KOH etching system is a simple and economical method for solution level detection based on the conductance of the solution. This detection system compensates for loss of water in the solution due to evaporation when etching at high temperatures. Finally, an example of the usefulness of the one-sided apparatus is given.

关键词： Etching

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Mechanical Properties of Microsensor Materials: How to Deal with the Process Dependences?

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MRS Online Proceedings Library 1991年第1期239卷 3-11页

作者： Senturia, Stephen D. Barton L. Weiler Professor of Electrical Engineering Microsystems Technology Laboratories Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge

Microsensors are measurement devices fabricated using planar integrated circuit technology together with enhancements generically called “micromachining”. It is well known that the thin-film materials used in microelectronics can have properties which differ from their bulk counterparts. In addition, thin-film materials exhibit residual stress, which is known to be strongly process dependent. The sensor designer must understand how the detailed process used to fabricate a particular device impacts the specific mechanical properties, hence, the expected mechanical device performance. This paper illustrates the problem of process-dependent material properties using examples of residual stress of several materials, and then presents an object-oriented material-property database which is being developed as part of a CAD system for microelectromechan-ical systems (MEMCAD).

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An object-oriented material-property database architecture for microelectromechanical CAD

An object-oriented material-property database architecture f...

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International Conference on Solid State Sensors and Actuators (TRANSDUCERS)

作者： M.A. Shulman M. Ramaswamy M.L. Heytens S.D. Senturia Microsystems Technology Laboratories Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA USA

The authors report on the implementation of an object-oriented database for capturing the process dependence of material properties of microelectronic materials. The database is a component of the MIT MEMCAD system, but will also be useful as a stand-alone module. It can accept data in several different forms: individual numbers; tables; and an algebraic function expressing the dependence of the material property on process conditions. The architecture and operation of the database are illustrated with the example of the temperature and gas-flow dependence of the residual stress in LPCVD (low-pressure chemical vapor deposited) silicon nitride.< >

关键词： Object oriented databases Design automation Object oriented modeling Solid modeling Material properties Spatial databases Micromechanical devices Materials science and technology Microelectronics Silicon

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A liquid shear-stress sensor fabricated using wafer bonding technology

A liquid shear-stress sensor fabricated using wafer bonding ...

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International Conference on Solid State Sensors and Actuators (TRANSDUCERS)

作者： K.-Y. Ng J. Shajii M.A. Schmidt Department of Electrical Engineering and Computer Science Microsystems Technology Laboratories Massachusetts Institute of Technology Cambridge MA USA

The authors report on the fabrication and testing of a microfabricated silicon floating-element (120 mu m*140 mu m) shear-stress sensor designed to detect high shear stresses (1-100 KPa) in fluid environments. Wafer bonding technology is used to produce a thin (5 mu m) dielectrically isolated silicon layer (allowing piezoresistive transduction in a half-bridge readout scheme) which is further processed to develop the floating-element sensor. The authors describe the details of the sensor fabrication, modeling of the sensor response, and the results of testing. There is good agreement between the modeled response of the sensor and the experimental data, and the sensor has also maintained its structural integrity under severe conditions.< >

关键词： Wafer bonding Fabrication Testing Silicon Sensor phenomena and characterization Stress Isolation technology Dielectrics Piezoresistance Semiconductor device modeling

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Operational characteristics of microfabricated electric motors

Operational characteristics of microfabricated electric moto...

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International Conference on Solid State Sensors and Actuators (TRANSDUCERS)

作者： L.S. Tavrow S.F. Bart J.H. Lang Microsystems Technology Laboratories Laboratory for Electromagnetic and Electronic Systems Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA USA

The authors report on the operational characteristics of LOGOS-based microfabricated radial-gap electric motors through lifetime tests, transient measurements, modeling, and parameter extraction. It is found that the reduction of static friction (stiction) in the bearings by the incorporation of a silicon nitride film permits these micromotors to spin in normal air ambients. Frictional drag from the bearing, which results from the electric-based side-pull of the rotor, is found to be the dominant rotor retarding force and to lead to motor wearout after approximately 10000 rotor revolutions. The frictional coefficient of the nitride on the polysilicon micromotor bearing is determined to be 0.36+or-004.< >

关键词： Electric motors Rotors Micromotors Lifetime estimation Electric variables measurement Parameter extraction Friction Silicon Semiconductor films Drag

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A STUDY OF 3 MICROFABRICATED VARIABLE-CAPACITANCE MOTORS

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SENSORS AND ACTUATORS A-PHYSICAL 1990年第1-3期21卷 173-179页

作者： MEHREGANY, M BART, SF TAVROW, LS LANG, JH SENTURIA, SD SCHLECHT, MF Microsystems Technology Laboratories Laboratory for Eletromagnetic and Electronic Systems Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 U.S.A.

This paper discusses the design, microfabrication, operating principles and experimental testing of three types of rotary variable-capacitance micromotors. The advantages and disadvantages of these motors are discussed. The three motor types are top-drive, side-drive and harmonic side-drive. In this work, the micromotors are surface micromachined using heavily-phosphorus-doped polysilicon for the structural material, deposited oxide for the sacrificial layers and LPCVD nitride for electrical isolation. Frictional forces associated with electric pull-down forces on the rotor are dominant in the side-drive and harmonic side-drive motors fabricated and tested to date. Air drive and electric excitation have been used in studying these effects. Side-drive micromotors have been successfully operated by a three-phase electrical signal with the rotors air-levitated. With air levitation, successful operation is achieved at bipolar excitations greater than 80 V across 4 μm air-gap motors having eight rotor and twelve stator poles, with only half of the stator poles excited. Motor operation is sustained indefinitely.

关键词： Electric Motors

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A LOCOS PROCESS FOR AN ELECTROSTATIC MICROFABRICATED MOTOR

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SENSORS AND ACTUATORS A-PHYSICAL 1990年第1-3期23卷 893-898页

作者： TAVROW, LS BART, SF LANG, JH SCHLECHT, MF Microsystems Technology Laboratories Laboratory for Electromagnetic and Electronic Systems Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 U.S.A.

A novel process based on local oxidation of silicon (LOCOS) for fabricating planar electric micron-scale radial-gap motors is described. Issues relating to the design, fabrication and performance of these micromotors are discussed, with particular emphasis given to the LOCOS process. Functioning variable-capacitance motors with rotors of 50 μm radii are described in detail and qualitative results of their operation with air levitation are presented. Finally, the integration of electronics with the micromotors on the same substrate is discussed. We have discussed the main issues involved in designing and fabricating electric variable-capacitance motors. Radial-gap motors have been selected for controllable instability and ease of fabrication. Furthermore, by examining the fabrication requirements of high-precision thick structures, we conclude that planarization is required unless greatly increased process complexity can be tolerated. The LOCOS-based process has thus been developed because it is inherently planar, unlike standard surface micromachining processes. Micron-scale motors and other structures have been successfully fabricated using the new LOCOS-based process. These motors were spun electrostatically up to speeds over 10 00O rpm, without visible signs of wear, when levitated by an externally generated air bearing. We are investigating the use of reduced-friction coatings such as Si 3 N 4 [2] or Teflon [19] in the bearing structure to eliminate the need for external air levitation. The inherent planarization of the motor not only facilitates the fabrication but may also facilitate the development of certain applications that require some form of direct cover or package. Starting and load transients must be sensed and controlled for stable VC motor performance. Closed-loop control, however, is virtually impossible witho

关键词： Electric Motors

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