Document Type
Thesis
Date of Award
9-30-1988
Degree Name
Master of Science in Electrical Engineering - (M.S.)
Department
Electrical Engineering
First Advisor
William N. Carr
Second Advisor
W. H. Warren Ball
Abstract
This thesis details the design for a solid-state humidity sensor which utilizes state-of-the-art silicon technology. The sensor design utilizes a microengineered surface which includes a polysilicon airbridge structure as heater and sensor element in an integrated device.The operation of this device depends upon the small variation of thermal convection coefficient which effects the temperature of the heated element within the device. The temperature of the polysilicon bridge is monitored by means of a resistance bridge. In one design(sensor I) a single polysilicon airbridge is used for both the heater and resistance sensing element. Also a second inferior design (sensor II) has been detailed for comparison in which the heater and the resistance sensing element are physically separated on the monolithic silicon substrate. The thermal characteristics of the device are modeled using ANSYS a finite element modeling program supplied by Swanson Analysis Systems, Inc.
The final design specific, a device with a single airbridge measuring 10 x 100 microns in size and thickness 0.5 microns of polysilicon deposited by low pressure chemical vapor deposition techniques. The modeled sensitivity of the optimal device at room temperature is 0.023 0C per percent relative humidity. The minimum detectable temperature differential of 0.023°C corresponds to a voltage differential meassured across the sensing polysilicon resistor of 0.055 mv. Further improvements are possible to use the lower thermal conductivity material to replace air cavity or to make air layer thicker than 4 microns.
Recommended Citation
Chen, Uei-Yanq, "Analysis and design of a surface microengineered silicon humidity sensor" (1988). Theses. 3033.
https://digitalcommons.njit.edu/theses/3033
