| 摘要 |
PROBLEM TO BE SOLVED: To realize a thermal flow-rate sensor in which a heater resistance value is not changed, in which a diaphragm itself used to form a heater is not broken down and which is of high reliability. SOLUTION: A silicon diaphragm 5 is doped. Heaters 7 and sensors 8, 9 are formed at the inside of the silicon diaphragm 5. Insulating films 4, 6 are executed to the surface and the rear surface of the silicon diaphragm 5. Insulating layers 10 are executed at the inside of the silicon diaphragm 5 between the heaters 7 and the silicon diaphragm 5. Consequently, in the heaters 7, a resistance change due to a piezoelectric effect is suppressed, an increase in the resistance value due to the diffusion of ions is suppressed, and the bad influence of waterdrops which are stuck to the surface of the silicon diaphragm 5 is suppressed. The thickness of the silicon diaphragm 5 is made thick (2μm or more), the thickness of the heaters 7 is made thick, and the silicon diaphragm 5 has a structure whose upper part and lower part are nearly symmetrical with reference to the center line in its face direction. As a result, the strength of the silicon diaphragm 5 is enhanced.
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