UETP-MEMS Course Proceedings, FSRM Neuchatel, Switzerland
University Enterprise Training Partnership MEMS project
with the support of the European Programme COMETT
Modeling and numerical simulation of both the fabrication process and the operation of single devices and entire integrated systems are more and more necessary. Computer aided design (CAD) can reduce the number of costly trial and error steps in the development of microsystems. No totally integrated toolsexist for layout design, process simulation and device simulation, but many existing tools can be used by the designer of a micro device to avoid the traditional experimental way. By the end of the course, participants will have a greater knowledge of existing CAD tools with emphasis on the judicious interpretation of numerical results, which is the key issue for using simulation programs with success.
The course addresses designers and engineers involved in the development of microdevices. Knowledge of the technology is recommended, but not essential.
Content of the course
- CAD of MEMS: Objectives, approaches, state of the art
- Layout design
- Practical demonstrations of etch simulators
- Modeling of fabrication processes for MEMS
- Device simulation
- Practical demonstrations and exercises
SILICON BASED MICROMECHANCAL SENSORS AND ACTUATORS IN SYSTEMS
Modeling of MEMS
Modeling and numerical simulation of miniaturized sensors and actuators together with the electronic devices encountered in the circuitry and signal conditioning environment is considered to be advantageous, as it constitutes a cost-effective and time-economizing alternative in the development of microtransducers compared to the traditional experimental approach “by straight-forward trial and error”.
Moreover, the device designer is equipped with an enhanced understanding of the microscopic physical effects, which occur in the interior of a microtransducer or electronic device and, therefore, are not immediately accessible by experimental methods. This allows to draw conclusions for an improved or even optimized re-design. Computer-aided design (CAD) optimization accounts for the progessively stringent user specifications resulting from the availability of highly precise process technology.
While the numerical simulation of microelectronic devices has already attained high standards on a professional level, reliable and easy-to-use CAD tools applicable to the simulation of the fabrication process and operation of semiconductor microsensors and actuators have still to be developed. To some extent, also the formulation of a proper theoretical framework (e.g., basic model equations) must be extended and completed. In the proposed project, these two objectives shall be pursued with the view to supporting the research and development activities in LESIT project.
The simulation programs to be used for CAD shall be validated with reference to properly selected test structures. If necessary, their functionality shall be supplemeted by new options in order to allow for the more complex requirements of integrated microtransducer modeling. In particular, the simulation tools presently available at the PEL shall be made applicable to the coupled treatment of mechanical, thermal, and electrical effects in the operation of microtransducers (MEMCAD).
- H. Baltes, D. Moser, R. Lenggenhager, O. Brand, D. Jaeggi: “Thermomechanical Microtransducers by CMOS and Micromachining”, Micromechanical Sensors, Actuators, and Systems, DSC-32, ASME, New York, 1991, pp. 61-75.
- H. Baltes, “Microtransducers by industrial IC technologies and micromachining”, Tech. Digest 10th Sensor Symposium, IEE Japan, Tokyo, 1992, pp. 17-23.
- B. E. Deal and A. S. Grove, “General Relationship for the Thermal Oxidation of Silicon”, J. Appl. Phys. 36, 1965, p. 3770 ff.
DEVICE SIMULATION – DYNAMICAL FINITE ELEMENT CALCULATIONS
by Thomas Fabula
Introduction to Dynamical Problems in Micromechanics
The study of structural dynamics is essential for understanding, evaluating and predicting the performance of micromechanical sensors and actuators. The knowledge of the dynamic response is fundamental to guarantee satisfactory operation of MEMS. Modal analysis, the calculation of eigenfrequencies and mode shapes, provides a definitive description of the response of a microstructure and allows the microengineer to investigate the effects of structural modifications.
Dynamical finite element analysis (FEA) is a powerful tool to model the dynamical response and to predict how a microstructure will perform under changed operating conditions. We will consider several stationary problems, like free vibrations of MEMS, and also transient behaviour of MEMS under time-dependent loads, i.e. forced vibrations due to harmonic or pulse excitation.
Typical applications for dynamical FEA are the estimation of the dynamical range for statically operating microsensors for pressure, force or acceleration measurement. The large field of resonant sensor applications which have a resonating element changing its resonance frequency as a function of a parameter to be measured will be a main point of our view. The design and realisation of microactuators, i.e. microswitches, microvalves and micropumps needs also advanced dynamic modeling techniques.
- Alavi, M., Fabula, Th., Schumacher, A., Wagner, H.-J.: Monolithic Microbridges in Silicon Using Laser Machining and Anisotropic Etching, EUROSENSORS VI, San Sebastian (1992), published in Sensors and Actuators
- Allik, H., Hughes, J.R.: Finite Element for Piezoelectric Vibration, Int. Journal Numerical Methods of Engineering, No. 2 (1970)
- Boley, B.A., Weiner, J.H., Theory of thermal stresses, R.E.Krieger Publishing Comp., John Wiley & Sons (1985)
- Bouwstra, S., Resonating microbridge mass flow sensor, Thesis, University of Twente, Enschede, The Netherlands (1990)
- Fabula, Th., Schroth, A.: Simulation des dynamischen Verhaltens mikromechanischer Membranen, VDI-Fachtagung für Geräte- und Mikrosystemtechnik, TU Chemnitz (1992), VDI-Bericht 960, VDI-Verlag Düsseldorf (1992)
- Fabula, Th.: Dynamische Berechnungen in der Mikromechanik – Simulation / Messung, 10. ANSYS Users’ Meeting, Arolsen, 28.-30.10.1992
- Ikeda, Takuro: Fundamentals of Piezoelectricity, Oxford University Press, Oxford (1990)
- Landolt-Börnstein: Zahlenwerte und Funktionen aus Naturwissenschaft und Technik, Gruppe III, Band 17a, Berlin, Springer Verlag (1982)
- Lerch, Reinhard: Simulation of piezoelectric devices by two- and three-dimensional finite elements, IEEE Transactions on UFFC, Vol. 37, No. 2 (1990)
- Naillon, M., Coursant, R.H., Besnier, F.: Analysis of piezoelectric structures by a finite element method, Acta Electronica, 25,4 (1983) 341-362
- Nye, J.F: Physical properties of crystals, Oxford science publ., Clarendon Press, Oxford (1990)
- Roszhart, T.V., The effect of internal friction on the Q of micromachined silicon resonators, IEEE Solid-State Sensor & Actuator Workshop, Hilton Head Island, South Carolina (1990)
- Stemme, G., Resonant silicon sensors, J. Micromech. Microeng. 1 (1991) 113-125
- Tichy, J., Gautschi, G.: Piezoelektrische Meßtechnik, Springer Verlag, Berlin (1980)
A course developed by UETP-MEMS (University Enterprise Training Partnership for Micro Electro Mechanical Systems) with the support of the European Programme COMETT (Community Programme for Education and Training in Technology).
(C) 1994, UETP-MEMS, FSRM, Switzerland