Patent Number: 6,167,761

Title: Capacitance type pressure sensor with capacitive elements actuated by a diaphragm

Abstract: In a capacitance type pressure sensor, a diaphragm is formed of a fragile material using an impurity-diffused monocrystal silicon and constitutes a stable pressure-responsive structure which does not undergo a plastic deformation. Between the diaphragm and a movable electrode is formed an oxide film to diminish stray capacitance between the movable electrode and a substrate and also between the movable electrode and a impurity-diffused layer. The oxide film and the movable electrode are each divided into plural regions so that the divided regions of the movable electrode are formed on the divided regions of the oxide film, thereby diminishing stress strain induced by a difference in therm expansion coefficient among the diaphragm, oxide film and movable electrode. The upper surface of a fixed electrode is covered with a structure for the fixed electrode which structure is formed by an insulating polycrystal silicon film not doped with impurity whereby the rigidity of the electrode is enhanced and it is possible to diminish a leak current.

Inventors: Hanzawa; Keiji (Mito, JP), Yasukawa; Akio (Kashiwa, JP), Shimada; Satoshi (Hitachi, JP), Suzuki; Seikou (Hitachiohta, JP), Saito; Akihiko (Hitachi, JP), Matsumoto; Masahiro (Hitachi, JP), Miyazaki; Atsushi (Mito, JP), Ichikawa; Norio (Mito, JP), Horie; Junichi (Hitachinaka, JP), Kuryu; Seiji (Hitachinaka, JP)

Assignee: Hitachi, Ltd. and Hitachi Car Engineering Co., Ltd.

International Classification: G01L 9/00 (20060101); G01L 009/12 ()

Expiration Date: 01/02/2018