Capacitive micro-sensor with a low stray capacity and manufacturing method

• US 5,381,300 A
• Filed: 02/19/1993
• Issued: 01/10/1995
• Est. Priority Date: 02/20/1992
• Status: Expired due to Fees

• Current Assignee: Sextant Avionique
• Original Assignee: Sextant Avionique
• Inventors: LeFort, Pierre O., Thomas, Isabelle, Legoux, Christophe
• Primary Examiner(s): Reynolds, Bruce A.
• Assistant Examiner(s): SWITZER, MICHAEL
• Application Number:
  US08/020,079
• Time in Patent Office: 690 Days
• Field of Search: 361/280, 361/283.1, 361/283.2, 361/283.3, 361/283.4, 29/25.41, 29/25.42, 177/210.6, 73/718, 73/715, 73/517 R
• US Class Current: 361/280
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends

Abstract

A capacitive micro-sensor includes a sandwich of three silicon wafers, a peripheral stripe of each surface of the central plate being assembled to a corresponding stripe of an opposing external plate through an insulating layer. At least one of the external plates forms a first electrode, the central plate forms a second electrode and at least one portion of the central plate forms a variable capacity with at least one of the external layers. At least one of the insulating layers is formed by a sandwich of a first insulating layer, a conductive layer and a second insulating layer, the conductive layer being associated with connection means.

Claims

1. A capacitive micro-sensor including a sandwich of three silicon wafers (1,2,3), a peripheral stripe of each surface of the central plate being assembled to a corresponding stripe of an opposing external plate through an insulating layer (5,6), at least one of said external plates forming a first electrode (22,23), the central plate forming a second electrode (21) and at least one portion of said central plate forming a variable capacity with at least one of said external plates, wherein at least one of said insulating layers is formed by a sandwich of a first insulating layer (5-1,6-1), a conductive layer (5-2,6-2) and a second insulating layer (5-3,6-3), said conductive layer being associated with connection means (25,26).

2. The capacitive micro-sensor of claim 1 forming an accelerometer, wherein said portion of the central plate forms an inertia block (8)

3. The capacitive micro-sensor of claim 1 forming a pressure sensor, wherein the lower plate includes a thinner portion (11) forming a diaphragm, said central plate including a stud (12) mounted onto said diaphragm, and a stripe extending between said stud and a peripheral portion of said central plate, said stripe forming with said upper plate a capacitive resonator whose characteristics vary as a function of the applied pressure.

4. The capacitive micro-sensor of claim 1 , wherein said conductive layer is set to the reference voltage of the central plate.

5. The capacitive micro-sensor of claim 1, wherein said first and second insulating layers are of silicon oxide and said conductive layer is of polysilicon.

6. The capacitive micro-sensor of claim 1, wherein said first and second insulating layers are of silicon oxide and said conductive layer is of single-crystal silicon.