# US 5,352,918 A · Capacitative micro-sensor with a low stray capacity and manufacturing method

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- Number: US 5,352,918 A
- Document ID: US5352918A
- Status: Granted
- Kind: A
- Application number: 08/020,077
- Filed: 1993-02-19
- Granted: 1994-10-04
- Earliest claimed: 1992-02-20
- Assignees: Sextant Avionique
- Inventors: Isabelle Thomas; Pierre O. Lefort; Christophe Legoux
- Web page: https://patentgrep.com/patent/US5352918A

## CPC

- G01L 9/0073: {using a semiconductive diaphragm}
- G01P 15/0802: {Details}
- G01P 15/125: by capacitive pick-up
- G01P 2015/0828: {the mass being of the paddle type being suspended at one of its longitudinal ends}
- G01L: MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE (weighing G01G)
- G01P: MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT (measuring or recording blood flow A61B5/02, A61B8/06; monitoring speed or deceleration of electrically-propelled vehicles B60L3/00; vehicle lighting systems adapted to indicate speed B60Q1/54; determining position or course in navigation, measuring ground distance in geodesy or surveying G01C; combined measuring devices for measuring two or more variables of movement G01C23/00; measuring velocity of sound G01H; measuring velocity of light G01J7/00; measuring direction or velocity of solid objects by reception or emission of radiowaves or other waves and based on propagation effects, e.g. Doppler effect, propagation time, direction of propagation, G01S; measuring speed of nuclear radiation G01T; measuring acceleration of gravity G01V; {measuring or recording the speed of trains B61L23/00; speed indicators incorporated in motor vehicles B60K35/00; measuring frequency or phase G01R; traffic control G08G})

## Abstract

A capacitive micro-sensor includes a sandwich of three silicon plates, each surface of the frame region of the central plate being assembled to the opposing surface of each external plate through a thin layer forming an insulating stripe. At least one of the external plates forms a first electrode, and at least one central portion of the central plate forms a variable capacity with at least one of the external plates. The frame region of the central plate is electrically disconnected from the central portion. First contact means are coupled to the frame portion. Second contact means are coupled to the central portion and form a second electrode of the variable capacity.

## Claims

### Claim 1

A capacitive micro-sensor including a sandwich of three silicon plates (1,2,3), each surface of the frame region (31) of the central plate being assembled to the opposing surface of each external plate through a thin layer forming an insulating stripe (5,6), at least one of the external plates forming a first electrode (22,23), and at least one central portion of said central plate forming a variable capacity with at least one of said external plates, wherein the frame region of said central plate is electrically disconnected from said central portion, first contact means (26) being coupled to the frame portion, and second contact means (21) being coupled to said central portion and forming a second electrode of said variable capacity.

### Claim 2 (depends on 1)

The capacitive micro-sensor of claim 1 forming an accelerometer, wherein said central portion of the central plate forms an inertia block (8) suspended to a stud (32) sandwiched between said external plates through the insulating layers (35,36).

### Claim 3 (depends on 1)

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

### Claim 4 (depends on 1)

The capacitive micro-sensor of claim 1, wherein said frame region is set (possibly in a floating manner) to the reference voltage of said central plate.

### Claim 5 (depends on 1)

The capacitive micro-sensor of claim 1, wherein said insulating layers are of silicon oxide.