Capacitive pressure sensor

• US 6,564,643 B1
• Filed: 04/12/2001
• Issued: 05/20/2003
• Est. Priority Date: 10/12/1998
• Status: Expired due to Term

• Current Assignee: Hitachi Car Engineering Company Limited (Hitachi, Ltd.), Hitachi, Ltd.
• Original Assignee: Hitachi Car Engineering Company Limited (Hitachi, Ltd.), Hitachi, Ltd.
• Inventors: Saitou, Akihiko, Onose, Yasuo, Miyazaki, Atsushi, Hanzawa, Keiji, Horie, Junichi, Shimada, Satoshi, Ichikawa, Norio
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): JENKINS, JERMAINE L
• Application Number:
  US09/807,325
• Time in Patent Office: 768 Days
• Field of Search: 737/24, 737/18, 361/283--28
• US Class Current: 73/724
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm

Abstract

A high-accuracy high-stability capacitor type pressure sensor which eliminates a parasitic capacitance between a reference capacitor and a semiconductor substrate. A capacitor type pressure sensor comprising, on a semiconductor substrate 10, an active capacitor 100 whose capacitance varies as the surrounding pressure varies, a reference capacitor 200 whose capacitance will not vary substantially as the surrounding pressure varies, and a circuit which is electrically connected to both said active and reference capacitors 100 and 200, detects the difference or ratio thereof, and uses the potential of a semiconductor substrate, wherein an electrode 30a of said reference capacitor is formed on the semiconductor substrate 10 with a dielectric 20 therebetween.

Claims

1. A capacitor type pressure sensor comprising an active capacitor between electrodes whose capacitance varies as the surrounding pressure varies, a reference capacitor between electrodes whose capacitance will not vary substantially as the surrounding pressure varies, and a circuit which is electrically connected to both said active and reference capacitors, detects the difference or ratio thereof, and uses the potential of a semiconductor substrate, wherein said reference capacitor is configured to act as a conductive electrode and is provided on the semiconductor substrate through an intervening dielectric substance.

2. A capacitor type pressure sensor in accordance with claim 1, wherein said active capacitor is formed on said semiconductor substrate with said dielectric therebetween.

3. A capacitor type pressure sensor in accordance with claim 1, wherein said reference capacitor contains a dielectric between electrodes.

4. A capacitor type pressure sensor in accordance with claim 1, wherein said reference capacitor has a cavity between the electrodes and the electrodes and the cavity of said reference capacitor are simultaneously formed with the same material as the active capacitor.

5. A capacitor type pressure sensor in accordance with claim 4, wherein one electrode of said reference capacitor has a diaphragm structure of the active capacitor, said diaphragm structure being secured by scaffolds to the semiconductor substrate, and the other electrode of said reference capacitor is placed near the scaffolds in an area delineated by the scaffolds.