Convective Inertial Sensors

Free convection of heated buoyant fluid is directed away from resultant acceleration. By monitoring the resulting heat plume, e.g. by measuring temperature at opposite sides of a microheater and some distance away, we can indirectly measure the magnitude of acceleration on an axis. Translational and Angular Acceleration can be measured by this method, first introduced by engineers at Humphrey, Inc, in San Diego.

V. Milanovic, E. D. Bowen, M. E. Zaghloul, N. H. Tea, J. S. Suehle, B. Payne, M.Gaitan, "Convective Accelerometer and Tilt Sensor in CMOS Technology," Applied Physics Letters, vol. 76, no. 2, Jan. 2000.

V. Milanovic, E. D. Bowen, N. H. Tea, J. S. Suehle, C. A. Zincke, M. Zaghloul, M. Gaitan, "Convection-based Accelerometer and Tilt Sensor Implemented in Standard CMOS," Proc. of Int. Mechanical Engineering Conference and Exhibition, Anaheim, CA, Nov. 18, 1998.

Multi Purpose Power Sensor Program

Ething of thermally and electrically conductive silicon substrate beneath thermoelectric and RF structure enables fabrication of efficient rms ac-dc converters in CMOS technology. The goal is low-cost fabrication of broadband microwave power sensors for multiple applications, monolithically integrated in CMOS with mixed-signal circuits. The program is funded by ONR and includes many collaborators, including SSC-SD, Oklahoma State Univ., Titan Corp., RF Microsystems, etc. 

V. Milanovic, M. Gaitan, M. E. Zaghloul, ``Micromachined Thermocouple Microwave Detector by Commercial CMOS Fabrications,'' IEEE Transactions on Microwave Theory and Techniques, Vol. 46, No. 5, pp. 550-3, May 1998.

V. Milanovic, M. Gaitan, E. D. Bowen, N. H. Tea, and M. E. Zaghloul, ``Thermoelectric Power Sensor for Microwave Applications by Commercial CMOS Fabrication,''IEEE Electron Device Letters, vol. 18, no. 9, pp. 450-452, Sep. 1997.

V. Milanovic, M. Gaitan, E. D. Bowen, N. H. Tea, and M. E. Zaghloul, ``Implementation of Thermoelectric Microwave Power Sensors in CMOS Technology,''Proc. of International Symposium on Circuits and Systems 1997, Hong Kong, Jun. 1997

V. Milanovic, M. Hopcroft, C. A. Zincke, M. Gaitan, and M. E. Zaghloul, "Optimization of CMOS MEMS Microwave Power 
Sensors,"Proceedings of Int. Symposium on Circuits and Systems - ISCAS'99, Vol. V, pp. 144-147, Orlando, FL, Jun. 1999.

V. Milanovic, M. Hopcroft, C. A. Zincke, M. Gaitan, and M. E. Zaghloul, K. S. J. Pister, "Modeling of Thermoelectric Effects in Planar Micromachined Structures Using SPICE,"6th Int. Workshop on Thermal Investigations of ICs and Systems, THERMINIC'00, Budapest, Hungary, Sep. 2000. 

Micromachined Microwave Transmission Lines in CMOS

Coplanar waveguides on CMOS substrates exhibit excessive losses due to the electromagnetic coupling into the conductive silicon substrate.  Propagation on substrates of conductivity in the 0.1-100 Ohm-cm range at frequencies from 0.1 GHz to 40 GHz was measured and modeled, and different "modes" of propagation were identified, with highly dispersive and lossy properties. The removal of Si substrate directly beneath the transmission lines by top-side or back-side micromachining techniques results in significant improvement of propagation characteristics. Such fully-suspended CPWs encapsulated in CMOS dielectrics propagate signals at near-light velocities, and with losses dominated by the finite conductivity of the Al conductors and skin effect.

M. Ozgur, V. Milanovic, C. Zincke, M. Gaitan, and M. E. Zaghloul, ``Quasi-TEM Characteristic Impedance of Micromachined CMOS Coplanar Waveguides,'' IEEE Tran. of Microwave Theory and Tech., pp. 852-854, May 2000. 

V. Milanovic, M. Ozgur, D. DeGroot, J. Jargon, M. Gaitan, M. E. Zaghloul, ``Characterization of Broadband Transmission for Coplanar Waveguides on CMOS Silicon Substrates,''IEEE Transactions on Microwave Theory and Techniques, Vol.46, No. 5, pp. 632-40, May 1998.

V. Milanovic, M. Gaitan, E. Bowen and M. E. Zaghloul, ``Micromachined Microwave Transmission Lines in CMOS Technology,'' IEEE Transactions on Microwave Theory and Techniques. Vol. 45, No. 6, Jun. 1997.

M. Ozgur, V. Milanovic, C. Zincke, M. E. Zaghloul, ``Characterization of micromachined CMOS transmission lines for RF communications,''International Symposium on Circuits and Systems 1998, Monterey, CA (ISCAS'98), Jun. 1998. 

Post-processing of Standard CMOS for Sensor, Actuator, and RF Applications

Selective removal of Si substrate by maskless top-side micromachining has many advantages in the development of a variety of thermoelectric sensors, actuators, and low-loss passive RF structures. 

N. H. Tea, V. Milanovic, J. S. Suehle, M. Gaitan, M. E. Zaghloul, and Jon Geist, ``Hybrid Post-processing Etching for CMOS-Compatible MEMS,'' IEEE/ASME Journal of Microelectromechanical Systems, vol. 6, no. 4, pp. 363-372, Dec. 1997.

B. Ghodsian and V. Milanovic, "A Method for suppressing the mechanical stress in CMOS for MEMS applications", accepted for publication at 198th Meeting of The Electrochemical Society: Microfabricated Systems and MEMS, Phoenix, Arizona, October 22-27, 2000.

B. Ghodsian, V. Milanovic and O. Villavicencio, "New standard post-procesing step for fabrication of large suspended structures on CMOS", Proceedings of SPIE: Micromachining and Microfabrication Process Technology V, Santa Clara, CA, 19-21 September, vol. 3874, pp. 120-128, 1999.

Thermoelectric Modeling and Characterization of Micromachined Planar Structures

An improved model for SPICE-based simulation of thermoelectric structures is needed for the new genre of thermoelectric devices achievable through CMOS MEMS fabrication. The new models include circuit elements for simulating thermoelectric Peltier and Thomson effects, and show greatly improved accuracy over previous models where those are neglected. The complete thermoelectric model is verified by comparing with experimental results on temperature distributions of suspended aluminum and polysilicon resistors and contacts.

V. Milanovic, M. Hopcroft, C. A. Zincke, M. Gaitan, and M. E. Zaghloul, K. S. J. Pister, "Modeling of Thermoelectric Effects in Planar Micromachined Structures Using SPICE,"6th Int. Workshop on Thermal Investigations of ICs and Systems, THERMINIC'00, Budapest, Hungary, Sep. 24-27 2000. Presentation is also available in .pdf.

V. Milanovic, M. Hopcroft, C. A. Zincke, M. Gaitan, and M. E. Zaghloul, "Optimization of CMOS MEMS Microwave Power Sensors,"Proceedings of Int. Symposium on Circuits and Systems - ISCAS'99, Vol. V, pp. 144-147, Orlando, FL, Jun. 1999.