Document Type
Thesis
Date of Award
9-30-1990
Degree Name
Master of Science in Electrical Engineering - (M.S.)
Department
Electrical and Computer Engineering
First Advisor
William N. Carr
Second Advisor
N. M. Ravindra
Third Advisor
Durgamadhab Misra
Abstract
This thesis details the first designs for microengineered vacuum pressure gauges based on silicon microelectronic technology. A monolithic polysilicon air-bridge structure (supported at both ends), within a Wheatstone bridge circuit, is used as a pressure sensor. The device utilizes the change of the thermal conductivity of a gas with ambient gas pressure. The doubly supported beam functions as a temperature sensitive resistor with a negative temperature coefficient of resistivity. Thermal change of resistance monitored as a measure of ambient pressure constitutes the basis of operation for this sensor. The sensor operates over the pressure ranging from 1 Torr to 10-3 Torr, with sensitivity ranging from 0.14 to 0.9 mV/Torr based on the design model developed.
Two different processing sequences are presented which are limited to standard silicon VLSI processing. The first one involves the etching of the silicon substrate using an aqueous ethylene diamine pyrocatechol solution to free the beam from the substrate. The second process involves the etching of a sacrificial oxide layer below the beam to release it from the substrate. The devices have been designed with beam widths varying from 5 to 20 microns and lengths varying from 50 to 300 microns. The entire design is based on industry compatible CMOS 2.0 micron technology with double-level metal and single-level polysilicon. This design uses 8 mask levels including passivation.
Recommended Citation
Talreja, Sanjay, "Microengineered thermal conductivity vacuum pressure sensor" (1990). Theses. 2964.
https://digitalcommons.njit.edu/theses/2964
