DESIGN TECHNIQUES

The design techniques used for MEMS in Japan are basically the same as those used in North America. The mechanical designers use finite element modeling (FEM) and 3-D computer-aided design to determine the original design. After testing, the models are adjusted based on the empirical data obtained. While not explicitly stated, it is apparent that analytical models are also used and corrected as test data become available.

Electrical IC modeling is used for silicon integrated MEMS devices. This is especially true of the commercial sensors that are under development where circuit simulation originally developed for LSI is applied to MEMS.

There is an effort in Japan to obtain electromechanical modeling for MEMS. This would allow a designer to obtain the performance of the total system in the minimum amount of time. Toyota demonstrated an effort to do this at Transducers '93, where the company presented its work in 3-D stress analysis in the crystal lattice to do electrical analysis in three-dimensional anisotropic conductivity (Morikawa 1993). No one has demonstrated an ability to design a MEMS totally in software, as has been done with IC designs, and to do simulations to check performance before actual fabrication. There is general agreement that the development of MEMS would be more rapid if accurate modeling tools were available.

One of the major needs in both Japan and the United States is a good microscale data bank of parameters and material properties. While there are individual efforts in Japan to do this, there is no central agency guiding the effort.

Data are required for both design and reliability modeling. Many Japanese researchers visited by the JTEC team agreed that the lack of good reliability data and a method for predicting lifetimes hinders commercialization of MEMS devices.

There is extensive use of testing and proof of concept-type demonstrations to illustrate the potential applications of MEMS. All researchers interviewed by JTEC agreed that the major requirement for an acceleration of MEMS is commercial success. To date, the technologies used to produce MEMS, especially silicon micromachining, have resulted in some commercial products. However, there are no MEMS devices in commercial use, other than sensors and some microvalves.


Published: September 1994; WTEC Hyper-Librarian