Series and shunt mems RF switch

• US 6,373,007 B1
• Filed: 04/19/2000
• Issued: 04/16/2002
• Est. Priority Date: 04/19/2000
• Status: Expired due to Fees

• Current Assignee: Air Force Government of The United States of America As Represented By The Secretary
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Strawser, Richard E., Lesniak, Christopher D., Calcatera, Mark C.
• Primary Examiner(s): FRIEDHOFER, MICHAEL A
• Application Number:
  US09/552,547
• Time in Patent Office: 727 Days
• Field of Search: 735/141.6, 735/143.6, 735/143.7, 148/402, 148/553, 200/181, 200/259, 200/168, 200/160, 200/512, 200/61.48, 200/275, 200/262-270, 251/129.02, 257/418, 257/419, 257/773, 257/784, 257/580, 310/309, 310/328, 330/278, 330/295, 330/307, 333/262, 334/55, 337/139, 337/140, 359/230, 361/233, 361/234, 385/16, 385/20
• US Class Current: 200/181
• CPC Class Codes: H01G 5/18 due to change in inclination, e.g. by flexing, by spiral wrapping
• CPC Class Codes: H01G 5/40 Structural combinations of variable capacitors with other electric elements not covered by this subclass, the structure mainly consisting of a capacitor, e.g. RC combinations
• CPC Class Codes: H01H 2059/0027 Movable electrode connected to ground in the open position, for improving isolation
• CPC Class Codes: H01H 59/0009 making use of micromechanics
• CPC Class Codes: H01P 1/184 Strip line phase-shifters H01P1/181, H01P1/185, H01P1/19 take precedence

Abstract

A micromechanical electrical systems (MEMS) metallic micromachined electrical switch usable on the die of an integrated circuit and inside the integrated circuit package for controlling radio frequency signal paths while incurring desirably small signal losses. The switch is of the single pole single throw mechanical type with provision for grounding one open-switch position node in the interest of limiting capacitance coupling across the switch in its open condition. Cantilever beam switch element suspension is included along with normally open and normally closed switch embodiments, electrostatic switch actuation and signal coupling through the closed switch by way of capacitance coupling. Low loss radio frequency operation above one gigahertz in frequency is provided.

Claims

1. Integrated circuit radio frequency transmission line metallic mechanical electrical switching apparatus comprising the combination of:

an integrated circuit substrate member;

a plurality of semiconductor material layers disposed on said substrate member, said semiconductor material layers including a plurality of electrical transistor members;

a pair of parallel disposed metallic transmission line ground members traversing an upper surface portion of said semiconductor material layers;

a metallic first radio frequency energy transmission line signal conveying member disposed between said pair of parallel disposed metallic transmission line ground members on said upper surface portion of said semiconductor material layers;

said metallic first radio frequency energy transmission line signal conveying member interconnecting a switch output port location on said surface portion of said semiconductor material layers with one of a transmission line radio frequency source and load member;

a second metallic radio frequency energy transmission line signal conveying member disposed between said pair of parallel disposed metallic transmission line ground members in extended alignment with said first radio frequency energy transmission line signal conveying member;

said second metallic radio frequency energy transmission line signal conveying member including a selectively movable portion extending in overlap with a switch output port location part of said first metallic radio frequency energy transmission line signal conveying member and normally resident in one of;

open switch relaxed spring physical segregation from said upper surface portion of said semiconductor material layers and said substrate member; and

closed switch relaxed spring physical segregation from said upper surface portion of said semiconductor material layers and said substrate member and in proximity with an overlapping raised extended portion of said metallic first radio frequency energy transmission line signal conveying member;

a metallic bridge member extending between said pair of parallel disposed metallic transmission line ground members, said bridge member being disposed in one of;

being received on said upper surface portion of said semiconductor material layers and grounding said selectively movable portion of said second metallic radio frequency energy transmission line signal conveying member in a deformed spring, open switch, condition of said second metallic radio frequency energy transmission line signal conveying member; and

being a raised center span metallic backstop member extending between said pair of parallel disposed metallic transmission line ground members over said selectively movable portion of said second radio frequency energy transmission line signal conveying member

electrostatic force generating electrical potential apparatus connected between said first metallic radio frequency energy transmission line signal conveying member and said second metallic radio frequency energy transmission line signal conveying member and selectively generating a deformed spring electrical potential.

2. The integrated circuit radio frequency transmission line metallic mechanical electrical switching apparatus of claim 1 wherein:

said switching apparatus comprises a normally open electrical switch normally resident in a relaxed spring condition of said second metallic radio frequency energy transmission line signal conveying member selectively movable portion; and

said bridge member comprises said raised center span metallic backstop member extending over said selectively movable portion of said second radio frequency energy transmission line signal conveying member engaging and grounding said selectively movable portion of said second metallic radio frequency energy transmission line signal conveying member.

3. The integrated circuit radio frequency transmission line metallic mechanical electrical switching apparatus of claim 1 wherein:

said switching apparatus comprises a normally closed electrical switch normally resident in a relaxed spring condition of said second metallic radio frequency energy transmission line signal conveying member selectively movable portion; and

said bridge member is received on said upper surface portion of said semiconductor material layers grounding said selectively movable portion of said second metallic radio frequency energy transmission line signal conveying member in a deformed spring, open switch condition of said second metallic radio frequency energy transmission line signal conveying member.

4. The integrated circuit radio frequency transmission line metallic mechanical electrical switching apparatus of claim 1 wherein said electrostatic force generating electrical potential apparatus comprises a source of direct current electrical in combination with a source of said radio frequency energy.

5. The integrated circuit radio frequency transmission line metallic mechanical electrical switching apparatus of claim 1 wherein said substrate member and said semiconductor material layers are comprised of one of the materials of silicon and gallium arsenide.

6. The integrated circuit radio frequency transmission line metallic mechanical electrical switching apparatus of claim 1 wherein said parallel disposed metallic transmission line ground members and said metallic first and second radio frequency energy transmission line signal conveying members comprise portions of a coplanar transmission line.

7. The integrated circuit radio frequency transmission line metallic mechanical electrical switching apparatus of claim 1 wherein said movable second metallic radio frequency energy transmission line signal conveying member is connected with a source of radio frequency energy.

8. The integrated circuit radio frequency transmission line metallic mechanical electrical switching apparatus of claim 1 wherein said movable second metallic radio frequency energy transmission line signal conveying member is connected with a radio frequency energy load member.

9. The integrated circuit radio frequency transmission line metallic mechanical electrical switching apparatus of claim 1 wherein said electrostatic force generating electrical potential apparatus generates an electrical potential of less than twenty five volts.

10. The integrated circuit radio frequency transmission line metallic mechanical electrical switching apparatus of claim 1 wherein said closed switch operating condition comprises a position of increased capacitive coupling close spacing with respect to said first metallic radio frequency energy transmission line signal conveying member and said position of increased capacitive coupling has a capacitance ratio of between fifty and two hundred times that of an open switch operating condition.

11. The method of performing electrical switching in a metallic conductor signal path of a radio frequency integrated circuit electrical device, said method comprising the steps of:

interrupting a lengthwise extent of said signal path with a movable metallic conductor-inclusive electrical switching member having said movable metallic conductor selectably disposable by incorporated spring tension in one of an electrically open switching position and an electrically closed switching position;

changing said switching member movable metallic conductor switching position with electrostatic force generated by an electrical potential switch control signal;

limiting spring tension urged movable metallic conductor movement arc and switch element spacing gap of said movable metallic conductor electrical switching member with a metal stopping member selectively disposed along a switch position-changing swing path thereof;

coupling radio frequency electrical signal between said movable metallic conductor-inclusive electrical switching member and a switch output conductor member using increased electrical capacitance coupling achieved between said members in said electrically closed switching position;

limiting capacitance-accomplished electrical signal coupling between said movable metallic conductor electrical switching member and said switch output conductor member by grounding said movable metallic conductor electrical switching member to a grounded electrical potential metal stopping member in said switch electrically open position.

12. The method of performing electrical switching in a metallic conductor path of a radio frequency integrated circuit electrical device metallic conductor of claim 11 wherein:

said movable metallic conductor-inclusive electrical switching member quiescently resides in a normally open electrical switching condition;

said step of limiting spring tension urged movable metallic conductor movement arc and switch element spacing gap includes spring tension urging of said movable metallic conductor away from said switch output conductor member into proximity with an overhanging grounding potential metal stopping member while entering said normally open electrical switching condition.

13. The method of performing electrical switching in a metallic conductor path of a radio frequency integrated circuit electrical device metallic conductor of claim 11 wherein:

said movable metallic conductor-inclusive electrical switching member quiescently resides in a normally closed electrical switching condition;

said step of limiting spring tension urged movable metallic conductor movement arc and switch element spacing gap includes spring tension urging of said movable metallic conductor away from a grounding electrical stop member and into proximity with an overhanging location of said switch output conductor member while entering said normally closed electrical switching condition.

14. The method of performing electrical switching in a metallic conductor path of a radio frequency integrated circuit electrical device metallic conductor of claim 11 wherein a first of said movable metallic conductor electrical switching member and said switch output conductor member comprises a source of radio frequency energy and a second of said members comprises a radio frequency load connection and wherein said step of limiting capacitance-accomplished electrical signal coupling comprises one of the steps of shunt loading said source of radio frequency energy and shunt paralleling a signal load member.

15. The method of performing electrical switching in a metallic conductor path of a radio frequency integrated circuit electrical device metallic conductor of claim 11 wherein said radio frequency integrated circuit electrical device has an operating frequency in the range of integral numbers of gigahertz.

16. The method of performing electrical switching in a metallic conductor path of a radio frequency integrated circuit electrical device metallic conductor of claim 11 wherein said step of coupling radio frequency electrical signal between said movable metallic conductor-inclusive electrical switching member and a switch output conductor member using increased electrical capacitance coupling includes coupling signal through a capacitance increased by a factor of between fifty and two hundred times by said electrically closed switching position.

17. The method of performing electrical switching in a metallic conductor path of a radio frequency integrated circuit electrical device metallic conductor of claim 11 wherein said step of changing said switching member movable metallic conductor position with electrostatic force generated by an electrical potential switch control signal includes generating an electrostatic field using an electrical potential of less than twenty five volts.

18. The method of performing electrical switching in a metallic conductor path of a radio frequency integrated circuit electrical device metallic conductor of claim 11 further including the step of determining said spring tension of said spring tension-urged, electrically open first switching position by selecting characteristic parameters of said metallic conductor during fabrication of said integrated circuit.

19. The method of performing electrical switching in a metallic conductor path of a radio frequency integrated circuit electrical device metallic conductor of claim 11 wherein said signal path of a radio frequency integrated circuit electrical device comprises one of an inter stage signal coupling path within said integrated circuit, a signal output path of said integrated circuit and a signal gain controlling path within said integrated circuit.

20. Integrated circuit electrical device metallic signal conductor path electrical switching apparatus comprising:

a lengthwise extended metallic signal conductor extending across a semiconductor layer surface of said integrated circuit;

an arcuate movable metallic conductor-inclusive electrical switching element located in said metallic signal conductor and in electrical series with opposed ends of said signal conductor;

a fixed position electrical switch output element also located in said metallic signal conductor and disposed at an end portion thereof on said semiconductor layer surface;

an end portion-removed section of said fixed position electrical switch output element being located within arcuate reach of said movable metallic conductor-inclusive electrical switching element;

said movable metallic conductor electrical switching element being electively disposable in either of spring tension-urged, electrically open and electrically closed switching positions of smaller and larger capacitance coupling respectively between said movable metallic conductor electrical switching element and said fixed position electrical switch output element;

electrostatic force generating electrical potential source means for moving said switching member movable metallic conductor arcuately from said electrically open switching position into said electrically closed switching position;

metal stopping member means selectively disposed in an opening swing arcuate path of said switching member movable metallic conductor for limiting spring tension urged switch opening arcuate travel and open switch element spacing gap of said movable metallic conductor electrical switching member in said electrically open switching position;

said metal stopping member means being disposed at zero signal electrical potential of said integrated circuit for shunt loading movable metallic conductor electrical switching element electrical signal to zero potential in said electrically open switching position. spring tension-urged.

21. The integrated circuit electrical device metallic signal conductor path electrical switching apparatus of claim 20 wherein said arcuate movable metallic conductor-inclusive electrical switching element is of a cantilever configuration.

22. The integrated circuit electrical device metallic signal conductor path electrical switching apparatus of claim 21 wherein said arcuate movable metallic conductor-inclusive electrical switching element and said lengthwise extended metallic signal conductor are of a single common metallization.