The New Jersey Institute of Technology's
Electronic Theses & Dissertations Project

Title:	A high-temperature pressure sensor utilizing linear voltage differential transformer (LVDT) and silicon wafer-to-wafer fusion bonding technologies
Author:	Okojie, Robert Sylvester
View Online:	njit-etd1993-039 (xiii, 123 pages ~ 4.7 MB pdf)
Department:	Department of Electrical and Computer Engineering
Degree:	Master of Science
Program:	Electrical Engineering
Document Type:	Thesis
Advisory Committee:	Carr, William N. (Committee chair) Cornely, Roy H. (Committee member) Niver, Edip (Committee member) Misra, Durgamadhab (Committee member) Marcus, Robert Boris (Committee member) Kurtz, Anthony D. (Committee member)
Date:	1993-10
Keywords:	Pressure transducers. Bonding (Technology). Integrated circuits.
Availability:	Unrestricted
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.