Electrostatically deformographic switches

• US 4,356,730 A
• Filed: 01/08/1981
• Issued: 11/02/1982
• Est. Priority Date: 01/08/1981
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Cade, Paul E.
• Primary Examiner(s): Gill, James J.
• Application Number:
  US06/223,522
• Time in Patent Office: 663 Days
• Field of Search: 73/517 R, 73/517 B, 340/366 R, 350/484, 357/55, 358/231, 200/61.45 R
• US Class Current: 73/514.26
• CPC Class Codes: G09F 9/372 the positions of the elements being controlled by the application of an electric field
• CPC Class Codes: G11C 11/00 Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor G11C14/00 - G11C21/00 take precedence
• CPC Class Codes: G11C 13/04 using optical elements ; using other beam accessed elements, e.g. electron or ion beam
• CPC Class Codes: H01H 59/0009 making use of micromechanics

Abstract

This describes a dual electrode electrostatically deflectable deformographic switch. The switch can be driven by co-incident voltages and can be made to retain and store information. The switch can be used either as a display or a memory and has a number of engineering advantages, for it is a direct drive display which does not need either vacuum envelopes or electron beam drives. Furthermore, greater efficiencies can be realized and no refresh is necessary since the switch will operate in a standby condition. Also only two voltage levels above ground, i.e., a write voltage and a standby voltage, are required. The switch will enable copiers to be directly driven by computers.

The switch can also be used as an optical waveguide transmit/receive switch or an accelerometer.

Claims

1. An improved deformographic device comprising:

a body of semiconductive material of a first conductivity type,

a layer of semiconductive material of a second conductivity type on said body,

an opening in said layer extending through said layer and exposing said body,

a coating of insulating material disposed over said layer of said second conductivity type,

a defined beam of said insulating material extending from said coating of insulating material over said opening,

a pair of electrodes disposed on said beam, and

means coupled to said electrodes for independently applying to each of said electrodes, with respect to said body, a threshold voltage, said threshold voltage being sufficient to create an electrostatic attraction between both of said electrodes and said body sufficient to overcome the bending stresses in said beam when applied to both of said electrodes but insufficient to overcome the bending stress in said beam when applied to only one of said electrodes.

2. The device of claim 1 wherein said pair of electrodes are interdigitated and alternating down the beam from the proximal end of said beam to the distal end of said beam.

3. The device of claim 2 wherein said beam is provided with means at its proximal end for reducing the bending stress in said beam.

4. The device of claim 2 wherein said body and said layer are comprised of silicon and said coating is comprised of silicon dioxide.

5. The device of claim 3 wherein said means for reducing the bending stress in the beam comprises a reduction in thickness of the beam at the proximal end of said beam.

6. The device of claim 3 wherein said means for reducing the bending stress in the beam comprises a reduction in the width of the beam at its proximal end.

7. The device of claim 1 wherein said beam has a generally square configuration and its proximal end is located at one of the corners of said beam and its distant end is at the corner diagonally opposite to said proximal end.

8. The device of claim 7 wherein said electrodes are interdigitated and alternating down the beam from the proximal end to the distal end of said beam.

9. The device of claim 7 wherein one of said electrodes is square and the other of said electrode is circumferential to said first electrode.

10. An improved deformographic display comprising;

a substrate, a cantilevered beam supported over said substrate,

means for impressing a selective voltage on the substrate,

a pair of conductive leads on said beam,

means for applying selected voltages on each of said leads to electrically deflect the beam with respect to the substrate, said selected voltages being sufficient to create an electrostatic attraction between both of said electrodes and said body sufficient to overcome the bending stresses in said beam when applied to both of said electrodes but insufficient to overcome the bending stress in said beam when applied to only one of said electrodes, and

means for reducing said selected voltages to a standby level sufficient to maintain said deflected beam in said deflected position but insufficient to overcome the bending stress in said beam.

11. An improved deformographic device comprising:

a body of semiconductive material of a first conductivity type,

a layer of semiconductive material of a second conductivity type on said body,

an opening in said layer extending through said layer and exposing said body,

a coating of insulating material disposed over said layer of said second conductivity type,

a defined beam of said insulating material extending from said coating of insulating material over said opening,

said beam being coupled to said coating at two opposing points defining an axis of rotation for said beam,

a pair of electrodes disposed on said beam, and

means coupled to said electrodes for independently biasing said electrodes, with respect to said body, to a threshold voltage sufficient to create an electrostatic attraction between the biased electrode and said body sufficient to cause said beam to rotate about said axis.

12. An improved accelerometer comprising:

a body of semiconductive material of a first conductivity type,

a layer of semiconductive material of a second conductivity type on said body,

a first emitter base and collector region in said layer defining a first transistor,

a second emitter base and collector region in said layer defining a second transistor,

a pair of openings in said layer extending through said layer and exposing said body,

a coating of insulating material disposed over said layer of said second conductivity type,

a first defined cantilevered beam of said insulating material extending from said coating of insulating material adjacent to said first emitter region over a first one of said pair of openings,

a second defined cantilevered beam of said insulating material extending from said coating of insulating material adjacent to said second emitter region over the second said pair of openings,

a selected mass of metal disposed on the cantilevered end of said first beam sufficient to subject the emitter of said first transistor to a selected stress,

a thin film metal electrode disposed over the entire surface of said second beam,

means for biasing said first and second transistors,

means coupled to said electrode for biasing said electrode, with respect to said body, to a voltage sufficient to create an electrostatic attraction between said electrode and said body sufficient to subject the emitter of said second transistor to a selected stress, and

a differential amplifier coupled across the collectors of said first and second transistors for measuring the differential voltage created when said body is accelerated such that the inertia of said mass causes a change in the stress to which the emitter of said first transistor is subjected.

13. An improved deformographic device comprising:

a body of semiconductive material of a first conductivity type,

a layer of semiconductive material of a second type on said body,

an opening in said layer extending through said layer and exposing said body,

a first defined cantilevered beam of insulating and optically conducting material extending over said opening,

a second defined cantilevered beam of insulating and optically conducting material extending over said opening,

a first metal electrode disposed on the entire surface of said first beam,

a second metal electrode disposed over the entire surface of said second beam,

an optical waveguide disposed on said layer having an end directly opposed to and in close proximity with and optically coupled to said first and said second beams,

means coupled to each of said electrodes for independently biasing said electrodes, with respect to said body, to a threshold voltage sufficient to create an electrostatic attraction between said biased electrode and said body sufficient to overcome the bending stresses in the beam on which said biased electrode is disposed.