Tapered cantilever beam for sensors

• US 5,209,117 A
• Filed: 10/22/1990
• Issued: 05/11/1993
• Est. Priority Date: 10/22/1990
• Status: Expired due to Fees

• Current Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Bennett, Paul T.
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): Dombroske, George M.
• Application Number:
  US07/600,949
• Time in Patent Office: 932 Days
• Field of Search: 73/517 R, 73/517 B, 73/517 R, 73/517 B, 73/516 R, 361/280, 361/283, 324/658
• US Class Current: 73/514.16
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/123 by piezo-resistive elements, e.g. semiconductor strain gauges
• CPC Class Codes: G01P 15/125 by capacitive pick-up

Abstract

A method of making a sensor with a mass (14) that is supported by at least one tapered cantilever beam (11). Tapered cantilever beam or beams (11) can be used in either capacitive or piezo-resistive structure. Increased sensitivity and decreased fragility is obtained by using the tapered cantilever beam.

Claims

1. A sensor which comprises:

a substrate;

a first electrically conductive area supported by the substrate which is part of a capacitor;

a suspended mass which is electrically conductive but, is suspended above and is isolated from the first electrically conductive area; and

a tapered support means including a cantilever beam having a first end and a second end with the second end attached to the substrate and extending upwards from the substrate, wherein the cantilever beam is further extended from the upward extension of the second end toward the suspended mass, and is continuously tapered with the first end being narrower than the second end, the first end being attached to the suspended mass, and wherein the suspended mass serves as part of a capacitor that moves.

2. The sensor of claim 1 wherein the suspended mass is supported by a plurality of tapered support means.

3. The sensor of claim 1 wherein the mass is rectangular shaped and is supported at each of its corners.

4. The sensor of claim 1 wherein additional material is added to the suspended mass to increase sensitivity.

5. The sensor of claim 1 wherein the first electrical conductive area is divided into two separate halves.

6. A sensor as claimed in claim 1 wherein the first conductive area further comprises:

a fixed capacitor plate extension having a first end and a second end, the first end attached to the first electrically conductive area, wherein the first end of the fixed capacitor plate extension is narrower than the second end of the fixed capacitor plate extension such that a continuous taper is formed between the first end and the second end of the fixed capacitor plate extension, thereby sensing capacitive changes in the fixed capacitive plate extension from movement of the cantilever beam.

7. A sensor as claimed in claim 1 further comprising:

a dielectric layer formed on the substrate before the electrically conductive area is formed, wherein the dielectric layer serves to electrically insulate the first electrically conductive area from the substrate.

8. A sensor which comprises:

a substrate;

a first electrically conductive area supported by the substrate which is part of a capacitor;

a suspended mass which is electrically conductive but, is suspended above and is isolated from the first electrically conductive area; and

a tapered support means including a cantilever beam having a first end, a second end, a first side, and a second side with the second end attached to the substrate and extending upwards from the substrate, wherein the cantilever beam is further extended from the upward extension of the second end toward the suspended mass, and the first and second sides are continuously tapered with the sides of the first end being narrower than the sides of the second end, the first end being attached to the suspended mass, and wherein the suspended mass serves as part of a capacitor that moves.

9. A sensor which comprises:

a substrate;

a first electrically conductive area supported by the substrate which is part of a capacitor;

a suspended mass which is electrically conductive but, is suspended above and is isolated from the first electrically conductive area; and

a plurality of cantilever beams, each cantilever beam having a first end and a second end with the second end attached to the substrate and extending upwards from the substrate located diagonally across from each other, wherein each cantilever beam is further extended from the upward extension of the second end toward the suspended mass, and is continuously tapered with the first end being narrower than the second end, the first end being attached to the suspended mass, and wherein the suspended mass serves as a part of a capacitor that moves, the tapered support means having its narrower end attached to the suspended mass.