Semiconductor pressure sensor utilizing capacitance change

• US 6,631,645 B1
• Filed: 09/01/2000
• Issued: 10/14/2003
• Est. Priority Date: 02/22/2000
• Status: Expired due to Fees

• Current Assignee: Hitachi Car Engineering Company Limited (Hitachi, Ltd.), Hitachi, Ltd.
• Original Assignee: Hitachi Car Engineering Company Limited (Hitachi, Ltd.), Hitachi, Ltd.
• Inventors: Satou, Shinya, Miyazaki, Atsushi, Hanzawa, Keiji, Shimada, Satoshi, Monma, Naohiro
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): JENKINS, JERMAINE L
• Application Number:
  US09/653,165
• Time in Patent Office: 1,138 Days
• Field of Search: 737/16--28
• US Class Current: 73/718
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm
• CPC Class Codes: G01L 9/125 with temperature compensating means non electric temperature compensating means G01L19/04

Abstract

An S/N ratio of an output of a semiconductor pressure sensor is improved, the sensor being of an electrostatic capacitance type pressure sensor for generating an output based upon a ratio between capacitances of a pressure sensitive capacitance element and a reference capacitance element. This semiconductor pressure sensor has: a pressure sensitive capacitance element having an electrostatic capacitance Cs changing with a pressure to be detected; a reference capacitance element having an electrostatic capacitance Cr not changing with the pressure; and a unit for detecting the pressure by outputting a signal corresponding to a ratio between the capacitances Cs and Cr, wherein an initial value Cr₀ of the capacitance Cr and an initial value Cs₀ of the capacitance Cs are defined by 1.2<Cr₀/Cs₀<1.8. The Cr₀/Cs₀ ratio is adjusted by changing the electrode area or the like of both the elements. In this manner, it is possible to obtain a large pressure gauge output ΔV, lower an amplification factor of the amplifier, and provide a high precision of the sensor.

Claims

1. A semiconductor pressure sensor comprising:

a pressure sensitive capacitance element having an electrostatic capacitance Cs changing with a pressure to be detected;

a reference capacitance element having an electrostatic capacitance Cr not changing with the pressure; and

means coupled to receive output signals from said pressure sensitive and reference capacitance elements, indicative of Cs and Cr respectively, for detecting pressure by outputting a signal corresponding to a ratio between the capacitances Cs and Cr;

wherein an initial value Cr₀ of the capacitance Cr and an initial value Cs₀ of the capacitance Cs are defined by 1.2<

Cr₀/Cs₀<

1.8.

2. The pressure sensor according to claim 1, wherein:

each of the pressure sensitive and reference capacitive elements comprises first and second electrodes having respective surface areas separated by a gap having a dielectric material therein; and

the surface areas of the electrodes of the pressure sensitive capacitive element differ from the surface areas of the electrodes of the reference capacitive element, such that 1.2<

Cr₀/Cs₀<

1.8 is set.

3. The pressure sensor according to claim 1, wherein:

each of the pressure sensitive and reference capacitive elements comprises first and second electrodes having respective surface areas separated by a gap having a dielectric material therein; and

a width of the gap in the pressure sensitive capacitive element differs from a width of the gap in the reference capacitive element, such that 1.2<

Cr₀/Cs₀<

1.8 is set.

4. The pressure sensor according to claim 1, wherein:

each of the pressure sensitive and reference capacitive elements comprises first and second electrodes having respective surface areas separated by a gap having a dielectric material therein; and

a dielectric constant of the material in the gap of the pressure sensitive capacitive element differs from a dielectric constant of a material in the gap of the reference capacitive element, such that 1.2<

Cr₀/Cs₀<

1.8 is set.