MICRO-ELECTRO-MECHANICAL SWITCH, AND METHODS OF MAKING AND USING IT

• US 20040124073A1
• Filed: 05/07/2002
• Published: 07/01/2004
• Est. Priority Date: 05/07/2002
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Forehand, David I., Pillans, Brandon W.
• Granted Patent: US 6,791,441 B2
• Time in Patent Office: Days
• US Class Current: 200/181
• CPC Class Codes: B81B 2201/014 having a cantilever fixed on one side connected to one or more dimples
• CPC Class Codes: B81B 2203/0118 Cantilevers
• CPC Class Codes: B81B 2203/04 Electrodes
• CPC Class Codes: B81B 3/0008 Structures for avoiding electrostatic attraction, e.g. avoiding charge accumulation
• CPC Class Codes: B81B 3/001 Structures having a reduced contact area, e.g. with bumps or with a textured surface
• CPC Class Codes: H01H 1/06 characterised by the shape or structure of the contact-making surface, e.g. grooved
• CPC Class Codes: H01H 2059/0018 Special provisions for avoiding charge trapping, e.g. insulation layer between actuating electrodes being permanently polarised by charge trapping so that actuating or release voltage is altered
• CPC Class Codes: H01H 2059/0072 with stoppers or protrusions for maintaining a gap, reducing the contact area or for preventing stiction between the movable and the fixed electrode in the attracted position
• CPC Class Codes: H01H 59/0009 making use of micromechanics

Abstract

A micro-electro-mechanical (MEMS) switch (10, 110) has an electrode (22, 122) covered by a dielectric layer (23, 123), and has a flexible conductive membrane (31, 131) which moves between positions spaced from and engaging the dielectric layer. At least one of the membrane and dielectric layer has a textured surface (138) that engages the other thereof in the actuated position. The textured surface reduces the area of physical contact through which electric charge from the membrane can tunnel into and become trapped within the dielectric layer. This reduces the amount of trapped charge that could act to latch the membrane in its actuated position, which in turn effects a significant increase in the operational lifetime of the switch.

Claims

1. An apparatus comprising a micro-electro-mechanical switch which includes:

a base having a first section which includes an electrically conductive part; and

a membrane having first and second ends supported at spaced locations on said base, and having between said ends a second section which includes an electrically conductive portion, said membrane being capable of resiliently flexing so as to move between first and second positions, said conductive part and said conductive portion being physically closer in said second position than in said first position, one of said first and second sections having a textured surface and the other thereof having a further surface which faces said textured surface, said textured surface having mutually exclusive first and second portions which are respectively in physical contact with and free of physical contact with said further surface when said membrane is in said second position, said first portion of said textured surface having an area which is substantially less than a total area of said textured surface.

2. An apparatus according to claim 1, wherein said first portion of said textured surface is defined by a plurality of separate regions of said textured surface which are spaced from each other.

3. An apparatus according to claim 1, wherein one of said first and second sections includes a dielectric material having thereon one of said textured and further surfaces, the other of said textured and further surfaces being provided on one of said conductive part and said conductive portion.

4. An apparatus according to claim 1,

wherein said second section includes a dielectric material having said textured surface on a side thereof facing said first section, said conductive portion being disposed on an opposite side of said dielectric material from said first section;

and

wherein said further surface is provided on said conductive part of said membrane.

5. An apparatus according to claim 4,

wherein said conductive portion has a textured surface on a side thereof nearest said first section;

and

wherein said dielectric material is a dielectric layer provided over and conforming a shape of said textured surface on said conductive portion so as to define on said dielectric layer said textured surface having said first and second portions.

6. An apparatus according to claim 4,

wherein said base includes a portion having a textured surface on a side thereof nearest said first section;

wherein said conductive portion is a conductive layer provided over and conforming to a shape of said textured surface on said portion of said base so as to define on a side of said conductive layer facing said first section a textured surface; and

wherein said dielectric material is a dielectric layer provided over and conforming to said textured surface on said conductive part so as to define on said dielectric layer said textured surface having said first and second portions.

7. An apparatus according to claim 6, wherein said portion of said base includes a base surface which faces said first section, and includes a plurality of nodules fixedly provided on said base surface, said textured surface on said portion of said base being defined by surface portions disposed on said nodules and said layer.

8. An apparatus according to claim 1,

wherein said second section includes a dielectric material having said further surface on a side thereof facing said first section, said conductive portion being disposed on an opposite side of said dielectric material from said first section;

and

wherein said textured surface is provided on said conductive part.

9. A method of switching through use of a micro-electro-mechanical switch that includes a base having a first section which includes an electrically conductive part, and a membrane having first and second ends supported at spaced locations on said base, and having between said ends a second section which includes an electrically conductive portion, one of said first and second sections having a textured surface and the other thereof having a further surface which faces said textured surface, comprising the step of:

responding to an applied voltage between said conductive part and said conductive portion by resiliently flexing said membrane so that said conductive part moves closer to said conductive portion as said membrane moves from a first position to a second position, including the step of causing mutually exclusive first and second portions of said textured surface to respectively be in physical contact with and free of physical contact with said further surface when said membrane is in said second position, said first portion of said textured surface having an area which is substantially less than a total area of said textured surface.

10. A method according to claim 9, including the step of configuring said first portion of said textured surface as a plurality of separate regions of said textured surface which are spaced from each other.

11. A method according to claim 9, including the step of configuring one of said first and second sections to include a dielectric material having one of said textured and further surfaces thereon, the other of said textured and further surfaces being provided on one of said conductive part and said conductive portion.

12. A method of fabricating a micro-electro-mechanical switch, comprising the steps of:

forming on a base a first section which includes an electrically conductive part;

forming a resiliently flexible membrane having first and second ends engaging spaced portions of said base disposed on opposite sides of said first section, and having between said ends a second section which includes an electrically conductive portion, said membrane being capable of resiliently flexing so as to move between first and second positions so that said conductive part and said conductive portion are physically closer in said second position than in said first position; and

forming on one of said first and second sections a textured surface and on the other thereof a further surface which faces said textured surface, said textured surface having mutually exclusive first and second portions which are respectively in physical contact with and free of physical contact with said further surface when said membrane is in said second position, said first portion of said textured surface having an area which is substantially less than a total area of said textured surface.

13. A method according to claim 12, wherein said step of forming said textured surface includes the step of configuring said first portion of said textured surface as a plurality of separate regions of said textured surface which are spaced from each other.

14. A method according to claim 12, including the step of configuring one of said first and second sections to include a dielectric material having thereon one of said textured and further surfaces, the other of said textured and further surfaces being provided on one of said conductive part and said conductive portion.

15. A method according to claim 12, wherein said step of forming said first section includes the steps of:

forming on a surface of said base a plurality of nodules;

forming over said nodules and said surface of said base a conductive layer which is said conductive portion and which conforms to a shape of said nodules and said surface of said base so as to define on a side of said conductive layer facing said first section a textured surface; and

forming over said conductive layer a dielectric layer which conforms to a shape of said textured surface on said conductive layer so as to define on said dielectric layer said textured surface having said first and second portions.