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Proceedings Paper

New structure and fabrication process for thermal-type microsensors
Author(s): Han Ji-song; Tadashi Kadowaki; Kazuo Sato; Mitsuhiro Shikida
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Paper Abstract

We describe the structure and fabrication of a one- dimensionally arrayed high density thermal-type micro fingerprint sensor. To provide thermal isolation, we designed and fabricated two sets of insulation cavities for each heater element, one for reducing the heat-transfer from the heater to the substrate, and the other one for that of heat to the wiring. The first set of cavities were etched under each heater bridge, leaving an SiO2 diaphragm with the heater bridge on it, and laterally penetrating with the cavities of neighboring heater bridges. The second ones were etched at the both ends of each heater element, leaving a set of SiO2- wiring bridges. This SiO2-wiring bridge structure was used as a thermal isolator when performing a metal-film wiring. The wiring (an electrical feed-through) was formed by a lift-off method, and runs on the SiO2 insulation surface from the heater element to the bonding pad through the SiO2-wiring bridges. The fabricated sensor device was made on a (100) SOI (silicon-on-insulator) wafer. Each heater element was 5 X 17 X 50 (micrometer3) with a pitch of 80 micrometer. Because of its small thermal capacity and effective thermal isolation, the sensor element was very sensitive. When a 0.4- V/20-microsecond pulse-voltage was applied to the heater elements, their resistance reached a steady maximum value in about 4 to approximately 5 microseconds. This level of sensitivity will be useful in variety of thermal sensors, such as micro temperature sensors and micro flow sensors, in addition to the thermal-type fingerprint sensors.

Paper Details

Date Published: 28 September 2001
PDF: 9 pages
Proc. SPIE 4557, Micromachining and Microfabrication Process Technology VII, (28 September 2001); doi: 10.1117/12.442969
Show Author Affiliations
Han Ji-song, Nagoya Univ. (Japan)
Tadashi Kadowaki, Nagoya Univ. (Japan)
Kazuo Sato, Nagoya Univ. (Japan)
Mitsuhiro Shikida, Nagoya Univ. (Japan)

Published in SPIE Proceedings Vol. 4557:
Micromachining and Microfabrication Process Technology VII
Jean Michel Karam; John A. Yasaitis, Editor(s)

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