Research in the Microelectromagnetic Device Group

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Micromachined Sensors and Actuators

This work concentrates on the design of new micro-sensors and actuators, constructed using integrated circuit fabrication techniques and silicon micromachining. Since there are many classical devices that sense most quantities of interest, it is critical to first identify an application that will benefit from the application of IC-like fabrication. This suggests either very high volume requirements (since IC fabrication can produce parts of low cost, but generally only if the devices are produced in very large numbers), or situations in which the size of the device must be quite small.

Current emphasis is the design-for-manufacture of optically-interrogated pressure micro transducers, and in the fabrication of a new inductive proximity sensor. We are also applying micromachining to a completely new area, hydrodynamic bearings. This work should produce patterned surfaces that maximize the performance of mechanical bearings, as well as allow the integration of sensors directly into a bearing. We are also studying the use of micromachined devices for chemical and biological agent sensors .

Slide Shows:

Y. Kim and D. P. Neikirk, "Surface Micromachined Fabry-Perot Pressure Transducer with Optical Fiber Interconnect," volume SPIE 2642, Micromached Devices and Components, Austin, Texas, USA, 23-24 October, 1995, pp. .

V. Gupta and D. P. Neikirk, "Design of an Inductive Proximity Sensor using a Two-Coil Planar Transformer," volume SPIE 2642, Micromached Devices and Components, Austin, Texas, USA, 23-24 October, 1995, pp. 173-182.

J. Han and D. P. Neikirk, "Deflection behavior of Fabry-Perot pressure sensors having planar and corrugated membrane," SPIE's Micromachining and Microfabrication '96 Symposium: Micromachined Devices and Components II, R. Roop and K. Chau, Proc. SPIE 2882, Austin, Texas, USA, 14-15 October, 1996, pp. 79-90.

J. J. Lavigne, S. Savoy, M. B. Clevenger, J. E. Ritchie, B. McDoniel, S.-J. Yoo, E. V. Anslyn, o. T. McDevitt, J. B. Shear, and D. Neikirk, "Solution-Based Analysis of Multiple Analytes by a Sensor Array: Toward the Development of an "Electronic Tongue"," JACS, vol. 120, July 1, 1998, pp. 6429-6430.

Relavent References:

Some Publications on Micromachined Sensors and Actuators

Quantum Interference Devices

Today it is possible to fabricate semiconductor structures with layers as thin as only a few tenths of a nanometer. The behavior of such structures is governed by quantum mechanical phenomena. Our research in this area concentrates on the use of tunneling structures built using molecular beam epitaxy, in particular quantum well devices. We have done extensive work on double barrier resonant tunneling diodes (DBRTDs) and their application to microwave and millimeterwave oscillators. We have also studied a new phenomena in these diodes that gives rise to memory switching that may have interesting applications in digital logic and information storage.

Slides Shows:

Relavent References:

Some Publications on Quantum Well Devices

• DBRTD oscillators
• A patent on memory switching devices.
• QWITT Diodes
• InGaAs RTD oscillators

Electromagnetics in Integrated Circuits, Packages, and Multi-Chip Modules

Electromagnetics-based Interconnect Parameter Extraction from Geometry

In this phase of our work we have concentrated on the development of efficient methods for the modeling of frequency-dependent resistance and inductance in MCM interconnects. Since the geometrical cross-sections of MCM-level (i.e., inter-chip interconnects) interconnects are relatively large (compared to intra-chip interconnects) their resistance can be quite low, and so their behavior is influenced by not only their capacitance and resistance, but also by their inductance. In addition, inductive cross-talk may be significant for inter-chip interconnects. These effects are intimately related to the distribution of current across the cross-section of the interconnects, that in turn, is influenced by interactions with other conductors (external proximity effects) and by the skin effect (internal proximity effects). Although these processes can be approximated using magneto-quasi-statics, they are inherently frequency dependent. Conventional "full wave" electromagnetic calculations of the frequency dependent series impedance (i.e., the resistance and inductance of the interconnect) are numerically intensive, making them unsuitable for CAD tools. We have developed several new approaches that provide excellent accuracy, along with a significant improvement in computation speed. For instance, by combined a new effective internal impedance with the current-filament method for extraction we have achieved excellent accuracy with at least a 100 times reduction in computation time. Comparison between conventional and our new "surface-ribbon" calculations (see our Interconnect Series Impedance Calculator) over a wide range of conductor geometries (including high aspect ratio cross-sections, such as square conductors) has shown excellent agreement from dc to 100 GHz.