MEMS Switch

• US 20150311003A1
• Filed: 04/25/2014
• Published: 10/29/2015
• Est. Priority Date: 04/25/2014
• Status: Active Grant

• Current Assignee: Analog Devices International Unlimited Company (Analog Devices, Inc.)
• Original Assignee: Analog Devices Global Unlimited Company (Analog Devices, Inc.)
• Inventors: Fitzgerald, Padraig L., Wong, Jo-ey, Goggin, Raymond C., Schirmer, Mark, Stenson, Bernard P., Lambkin, Paul
• Granted Patent: US 9,748,048 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H01H 1/0036 Switches making use of microelectromechanical systems [MEMS] for electromagnetic relays H01H50/005; for electrostatic relays H01H59/0009
• CPC Class Codes: H01H 2001/0084 with perpendicular movement of the movable contact relative to the substrate
• 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

Several features are disclosed that improve the operating performance of MEMS switches such that they exhibit improved in-service life and better control over switching on and off.

Claims

1. A MEMS component, comprising:

a substrate;

a support;

a movable structure;

a control electrode;

and the support extends from the substrate and holds a portion of the movable structure adjacent the substrate, and the movable structure overlaps with the control electrode, wherein the movable structure is delimited by an edge, and the control electrode extends past the edge of the movable structure.

2. A MEMS component as claimed in claim 1 further comprising a first switch contact, and the movable structure extends in a first direction from the support towards and over the first switch contact.

3. A MEMS component as claimed in claim 2 in which a spatial extent of the control electrode in a second direction is greater than the spatial extent of the movable structure in the second direction.

4. A MEMS component as claimed in claim 2 in which the movable structure has an end wall distal from the support, and the control electrode extends beyond the end wall, except in a region of a contact carrier portion of the movable structure.

5. A MEMS component as claimed in claim 4 in which the contact carrier portion carries a contact and one or both of a length of the contact carrier portion or a height of the contact are selected to reduce a force from charge trapped adjacent an edge of the control electrode to below a threshold value.

6. A MEMS component as claimed in claim 5 in which at least one of the contact carrier and the substrate adjacent the contact carrier have a surface recess formed therein.

7. A MEMS component as claimed in claim 2 in which a second portion of the movable structure extends in a third direction from the support, the third direction being substantially opposed to the first direction, and where the second portion overlaps with a second control electrode.

8. A MEMS component as claimed in claim 7 in which, in use, the second control electrode can be selectively connected to a voltage in order to attract the second portion of the movable structure and thereby to urge the movable structure away from engagement with the first switch contact.

9. A MEMS component comprising:

a deformable structure supported at a first position by a support, the deformable structure carrying a contact for making contact with a further contact surface and passing adjacent but separated from a control electrode, and where a potential difference between the control electrode and the deformable structure exerts a force on the deformable structure causing it to deform, wherein the deformable structure is modified to limit the peak stress occurring in the deformable structure.

10. A MEMS component as claimed in claim 9 in which the length is increased to limit peak stress.

11. A MEMS component as claimed in claim 9 in which the thickness of the deformable structure is increased.

12. A MEMS component as claimed in claim 9 in which a width of the deformable structure is non-uniform.

13. A MEMS component as claimed in claim 9 in which a length of the contact is increased to increase a peak stress before contact between the deformable member and the control electrode occurs.

14. A MEMS switch, comprising:

a substrate;

a support;

a movable structure;

a control electrode;

arranged such that the movable structure is held by the support above the substrate and extends over the control electrode, and wherein at least one of the substrate and the movable structure has at least one structure formed thereon to hold the movable structure spaced apart from the control electrode during use.

15. A MEMS switch as claimed in claim 14 wherein a depending bumper or support is formed on the movable structure and arranged not to touch the control electrode.

16. A MEMS switch as claimed in claim 15 in which the depending bumper is formed to one side of the control electrode.

17. A MEMS switch as claimed in claim 15 in which the depending bumper is formed on the movable structure in a region overlapping the control electrode, and an aperture is formed in a corresponding portion of the control electrode.

18. A MEMS switch as claimed in claim 14 in which the structure comprises an insulator formed between the control electrode and the movable structure.

19. A MEMS component, comprising:

a substrate having a first coefficient of thermal expansion;

a support extending from the substrate, and having a second coefficient of thermal expansion;

the MEMS component further comprising an expansion modification structure formed at or adjacent an interface between the substrate and the support, and having a third coefficient of expansion greater than the first coefficient of expansion, and arranged to exert a thermal expansion force on the substrate in the vicinity of the interface so as to simulate a fourth coefficient of expansion different from the first coefficient in the substrate in the vicinity of the interface.

20. A MEMS component as claimed in claim 19 in which the third coefficient of thermal expansion is greater than the second coefficient of thermal expansion.

21. A MEMS component as claimed in claim 19 in which the expansion modification structure comprises a plate or block like structure buried beneath a foot of the support.

22. A MEMS component as claimed in claim 21 in which the expansion modification structure is separated from the support by a portion of the substrate.

23. A MEMS component as claimed in claim 19 in which the expansion modification structure extends beyond an edge of the support.

24. A MEMS component as claimed in claim 19 in which the expansion modification structure is formed of Aluminum or Copper.

25. A MEMS component as claimed in claim 19 in which the MEMs component is a switch and a switch member is supported by the support.

26. A MEMS component as claimed in claim 25 in which the support has slots formed therein to divide the support into a plurality of upstanding elements.

27. A MEMS component as claimed in claim 26 in which the slots extend through the support dividing it into a plurality of pillars.

28. A MEMS component as claimed in claim 26 in which the switch member is slotted along a portion of its length.

29. A MEMS component as claimed in claim 19 further comprising a recess or channel formed adjacent an edge of the foot of the support to reduce thermal stress exerted between the substrate and the support.

30. A MEMS switch as claimed in claim 25 further including a first switch contact having a region thereof formed as a cantilever or beam over a void such that the first switch contact can deflect in response to pressure exerted on it by the switch member.

31. A MEMS component having a support extending upwardly from a substrate and carrying a structure that extends over a surface of the substrate or a depression formed in the substrate, and wherein the structure is provided with a plurality of slots and/or apertures therein to facilitate chemical removal of material from beneath the structure.

32. A MEMS component as claimed in claim 31 in which the MEMS component is a switch having a switch member (32) extending over the substrate towards a first switch contact, and at least one apertures and/or slot is formed in the switch member such that a portion of the switch member is always less than 20 microns from an edge or aperture.

33. A MEMS switch comprising:

a substrate;

a support;

a switch member supported by the support at a position such that a portion of the switch member extends away from the support in a first direction towards a first switch contact and over a first control electrode;

wherein the MEMS switch further comprises a second control electrode adjacent a portion of the switch member such that an attractive force acting between the second control electrode and the switch member urges the switch member to move away from the first switch contact.

34. A MEMS switch as claimed in claim 33 in which the first and second control electrodes are positions in opposing semicircular areas with respect to the support.

35. A MEMS switch as claimed in claim 33 in which the switch member further comprises a second portion extending from the support in a third direction opposed to the first direction and over the second control electrode.

36. A MEMS switch as claimed in claim 33 in which the second control electrode is connected to the first control electrode via an electrostatic protection or overvoltage protection device.

37. A MEMS switch as claimed in claim 33 in which the second control electrode is connected to the first control electrode by a high impedance path such that a voltage at the second control electrode lags a voltage of the first control electrode.

38. A MEMS switch as claimed in claim 33 in which the voltage at the second control electrode tends to a fraction of the voltage at the first control electrode as set by a potential divider.

39. A MEMS switch comprising:

a first switch contact;

a second switch contact;

a control electrode;

a substrate;

a support;

a spring;

and a conduction element;

wherein the support is formed away from the first and second switch contacts, and the spring extends from the support towards the first and second switch contacts, and carries the conduction element such that the conduction element is held above but spaced from at least one of the first and second contacts, and the spring and/or the conduction element pass adjacent to the control electrode.

40. A MEMS switch as claimed in claim 39 in which at least one of the length, width, thickness and material used for the spring is selected for a desired restoring force.

41. A MEMS switch as claimed in claim 39 in which at least one of the length, width, thickness and material of the conduction element is selected so as to span the distance between the first and second switch contacts whilst giving a breakdown voltage above a first threshold.

42. A MEMS component comprising a support, a movable element, a control electrode adjacent the movable element and a torsional arm extending between the movable element and the support.

43. A MEMS component as claimed in claim 42 comprising first and second supports disposed on opposing sides of the movable element and connected thereto by first and second arms.

44. A MEMS component as claimed in claim 43, which this the first and second supports are aligned with each other along a direction parallel to the rotational displacement in the arm when a voltage is applied to the control electrode.

45. A MEMS component a claimed in claim 42 in which the movable element extends in opposing directions either side of the torsional arm, and wherein first and second control electrodes are provided such that applying a voltage to the first control electrode urges the movable element to rotate about the torsional arm in a first direction and applying a voltage to the second control electrode urges the movable element to rotate about the torsional arm in a second direction opposite to the first.

46. A MEMS component as claimed in claim 42 in which the component is a switch and the movable element carries a switch contact.