Date of Award

Fall 1993

Document Type

Thesis

Degree Name

Master of Science in Electrical Engineering - (M.S.)

Department

Electrical and Computer Engineering

First Advisor

William N. Carr

Second Advisor

Roy H. Cornely

Third Advisor

Edip Niver

Fourth Advisor

Durgamadhab Misra

Fifth Advisor

Robert Boris Marcus

Sixth Advisor

Anthony D. Kurtz

Abstract

A novel high-temperature pressure sensor was designed based on the principle of magnetic induction. The device is meant to correct the problems inherent in conventional Solid-State pressure transducers such as piezoresistive and capacitive at temperatures above 300°C. Prominent among these problems are increased leakage current, reduced absolute sensitivity, redistributed impurity concentration profile, and thermal mismatch.

This thesis combined the Biot Savart magnetostatic principle and the theory of deflecting clamped circular plates to obtain the microelectromechanical relationship. The problem of thermal mismatch was resolved by the symmetrical layering of a Si3N4/TaSi2/Si3N4 sandwich, thereby controlling runaway thermal expansion of TaSi2. Single-wafer and Wafer-to-Wafer fusion bonding fabrication processes are proposed for making the device.

The device operating temperature range is extended above that obtainable with piezoresistive silicon to 6500C, based on theoretical and simulation results. The full-scale Temperature Coefficient of Offset (TCO) of 771ppm/°C, and pressure sensitivities of 0.4mV/kPa and 0.54mV/kPa at 25°C and 6500C, respectively, were achieved. The output voltage Temperature Coefficient of Sensitivity (TCS) for temperatures over the range of -50 to 6500C is 800ppm/°C. The large output voltage dynamic range of over 100mV competes well with conventional sensors. The increased pressure sensitivity at high temperatures is an added advantage.

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