| 摘要 |
In the present invention, an etching hole 21 is formed in a polysilicon film 14 as a cavity-wall member. Through the etching hole 21 , hydrofluoric acid is injected, so as to dissolve a silicon oxide film 13 , thereby forming a cavity 22 . In the cavity 22 , a detecting unit 12 of a sensor is in an exposed condition. Next, by sputtering, an Al film 16 is deposited in the etching hole 21 and on an upper face of a substrate. Thereafter, a portion of the Al film 16 positioned on the polysilicon film 14 is removed by etching back, thereby leaving only a metal closure 16 a of Al which closes the etching hole. The sputtering step is performed under a pressure of 5 Pa or less, so that the pressure in the cavity can be held to be low.
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