Hitachi, Ltd.

Hitachi Car Engineering Co., Ltd.

Other

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

Seiji Kuryu

Satoshi Shimada

Junichi Horie

Yasuo Onose

Norio Ichikawa

Akihiko Saito

Masahiro Matsumoto

Keiji Hanzawa

Atsuo Watanabe

Atsushi Miyazaki

Akio Yasukawa

Shinya Satou

Hiroshi Moriya

Seikou Suzuki

Naohiro Momma

A sensor with built-in circuits can be improved in the stability of the operation or characteristics. A circuit region and a sensor region are covered by a passivation film. The sensor region is partially covered by the passivation film. The sensor region and circuit region are protected by the passivation film, and an effect of the passivation film on the mechanical displacement of a diaphragm portion can be alleviated so that the sensor with built-in circuits may be improved in the stability of the operation or characteristics.

Sensor with built-in circuits and pressure detector using the same

The object of the present invention is to propose an etch channel sealing structure characterized by excellent impermeability to moisture and resistance to temporal change of the diaphragm in the pressure sensor produced according to the sacrificial layer etching technique, and to provide a pressure sensor characterized by excellent productivity and durability. After a very small gap is formed by the sacrificial layer etching technique, silicon oxide film is deposited by the CVD technique or the like, thereby sealing the etch channel. Further, impermeable thin film of polysilicon or the like is formed to cover the oxide film. This allows an etch channel sealing structure to be simplified in the pressure sensor produced according to the sacrificial layer etching technique, and prevents entry of moisture into the cavity, thereby improving moisture resistance. Moreover, sealing material with small film stress reduces temporal deformation of the diaphragm.

Semiconductor pressure sensor and pressure sensing device

By sealing a diaphragm with less processes and lower cost and reducing deformation due to remaining stress, a stable and highly reliable pressure sensor construction is proposed. The pressure sensor is low in measurement error and small in floating capacitance and leakage current and good in characteristic. As a means to attain the above object, a polycrystalline silicon diaphragm is sealed with a silicon oxide film deposited through a LPCVD method and then completely covered. The diaphragm is placed on a surface of a semiconductor substrate with a nearly constant gap of 0.15 to 1.3 &#x3bc;m, and has difference-in-grade constructions of a deformation reducing means due to remaining stress.

Capacitive type pressure sensor

A pressure sensor of electric capacitance type which includes a plurality of pressure sensor units connected in parallel with one another and each formed on a substrate by an electrode, a cavity region and a diaphragm having an electrically conductive film which is disposed in opposition to the electrode with the cavity region intervening between the electrode and the diaphragm, wherein diaphragm fixing portions are disposed internally of the cavity region so that a single sheet of the diaphragm is partitionarily and regionally allotted to regions of the plural pressure sensor units, respectively. With this structure of the capacitance-type pressure sensor, ineffective region for capacitance detection is minimized and hence the parasitic capacitance can be reduced with the detection accuracy of the sensor being improved.

Capacitance-type pressure sensor

Dynamic quantitative displacement is converted stably and straight into voltage (D.C. output) by using a high speed detection driving frequency without restricting a response of an operational amplifier. When a dynamic quantity detection electrostatic capacitance changes according to a dynamic quantity, electric charges stored in this element and in a reference electrostatic capacitance become unbalanced to produce a difference value, and an output of an operational amplifier changes according to the difference in electric charge quantity. However, the output becomes finally stable when the electric charges in the dynamic quantity detection electrostatic capacitance and in the reference electrostatic capacitance become equal. The output is proportional to a reciprocal of the dynamic quantity detection electrostatic capacitance and it is a D.C. voltage. Further, output without depending on integration feedback capacitance (feedback condenser) CF can be obtained.

Electrostatic capacitance type dynamical quantity sensor

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.

Capacitance type pressure sensor with capacitive elements actuated by a diaphragm

Growing community of inventors

Hitachinaka, Japan

Seiji Kuryu