Electromagnetic radiation detectors having a micromachined electrostatic chopper device

• US 6,586,738 B2
• Filed: 04/13/2001
• Issued: 07/01/2003
• Est. Priority Date: 04/13/2001
• Status: Expired due to Fees

• Current Assignee: Research Triangle Institute
• Original Assignee: MCNC, Inc.
• Inventors: McGuire, Gary E., Dausch, David E.
• Primary Examiner(s): Porta, David
• Assistant Examiner(s): Berchem, Troy A
• Application Number:
  US09/834,825
• Publication Number:
  US 20020148964A1
• Time in Patent Office: 809 Days
• Field of Search: 250/338.3, 250/350, 250/351
• US Class Current: 250/338.3
• CPC Class Codes: B81B 3/0035 Constitution or structural means for controlling the movement of the flexible or deformable elements
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 26/0866 the reflecting means being moved or deformed by thermal means

Abstract

The present invention provides for an improved electromagnetic radiation detector having a micromachined electrostatic chopping device. The MEMS flexible film chopping device provides reliability, efficiency, noise reduction and temperature fluctuation compensation capabilities to the associated electromagnetic radiation detector. An electromagnetic radiation detector having an electrostatic chopper device comprises a detector material element, first and second electrodes in electrical contact with the detector material element and electrically isolated from one another. Additionally, the chopper device will incorporate a flexible film actuator overlying the detector material layer and moveable relative thereto. The flexible film actuator will typically include an electrode element and a biasing element such that the actuator remains in a fully curled, open state absent electrostatic voltage and moves to a fully uncurled, closed state upon the application of electrostatic voltage. Arrays that incorporate a plurality of electromagnetic radiation detectors and/or electrostatic chopping devices are additionally provided for.

Claims

1. An electromagnetic radiation detector having an electrostatically driven microelectromechanical system (MEMS) chopper device, comprising:

a detector material element;

first and second electrodes in electrical contact with said detector material element; and

a flexible film actuator overlying said detector material element and moveable relative thereto to alternately allow passage of electromagnetic radiation to said detector material element and block passage of radiation to said detector material element.

2. The detector of claim 1, further comprising a substrate that supports the detector material element.

3. The detector of claim 2, wherein the substrate further comprises a silicon substrate having a read-out circuit disposed thereon.

4. The detector of claim 2, further comprising a thermal isolation bridge disposed on the substrate that supports the dielectric material element and provides thermal isolation between the detector material layer and the substrate.

5. The detector of claim 2, wherein the detector material element further comprises a detector material layer and the first and second electrodes further comprise first and second electrode layers disposed on opposite sides of the detector material layer and supported by the substrate.

6. The detector of claim 1, wherein the flexible film actuator further comprises a third electrode and a biasing element, the actuator having a fixed portion attached to an underlying surface and a distal portion moveable relative to an underlying electrode.

7. The detector of claim 6, further comprising a fourth electrode disposed between the flexible film actuator and the second electrode, the distal portion of the actuator being moveable relative to the fourth electrode.

8. The detector of claim 7, further comprising an insulating element disposed between the fourth electrode and the first and second electrodes.

9. The detector of claim 1, further comprising an electromagnetic radiation-absorbing element disposed between the detector material element and the flexible film actuator.

10. The detector of claim 1, wherein the detector material element further comprises a detector material chosen from the group consisting of lead zirconate titanate (PZT), lithium tantalate (LiTaO₃), lead titanium oxide (PbTiO₃), barium strontium titanate (BST), polyvinylidene fluoride (PVDF) and vanadium oxide.

11. The detector of claim 1, further comprising a transparent substrate disposed proximate the detector material element and a transparent electrode disposed on the transparent substrate, wherein the flexible film actuator is supported by and affixed to said transparent substrate.

12. The detector of claim 11, further comprising an air gap separating the detector material element from the transparent substrate.

13. An electromagnetic radiation detector having an electrostatically driven MEMS chopper device, comprising:

a substrate;

a thermal isolation bridge disposed on said substrate;

a first electrode layer disposed on said thermal isolation bridge;

a detector material layer overlying on said thermal isolation bridge and in electrical contact with said first electrode layer;

a second electrode layer overlying said thermal isolation bridge, electrically isolated from said first electrode layer and in electrical contact with said detector material layer; and

a flexible film actuator overlying the detector material layer and having a third electrode layer and at least one biasing layer, the actuator having a fixed portion attached to an underlying surface and a distal portion movable with respect to the second electrode layer.

14. The detector of claim 13, wherein said substrate further comprises a read-out circuit disposed on the substrate.

15. The detector of claim 13, further comprising an air gap between the substrate and the detector material layer.

16. The detector of claim 13, wherein the detector material layer is disposed between the first electrode layer and the second electrode layer.

17. The detector of claim 13, wherein the first and second electrode layers further comprise a material chosen from the group consisting of gold, platinum, chromium, titanium, LSCO or ruthenium oxide.

18. The detector of claim 13, wherein the detector material layer further comprises a detector material chosen from the group consisting of lead zirconate titanate (PZT), lithium tantalate (LiTaO₃), lead titanium oxide (PbTiO₃), barium strontium titanate (BST), polyvinylidene fluoride (PVDF) and vanadium oxide.

19. The detector of claim 13, further comprising an electromagnetic radiation-absorbing layer disposed between said second electrode layer and said flexible film actuator.

20. The detector of claim 13, wherein the flexible film actuator device further comprises a third electrode layer disposed between a first biasing layer and a second biasing layer.

21. The detector of claim 13, further comprising an insulating layer disposed on the electromagnetic radiation-absorbing layer.

22. The detector of claim 21, further comprising a fourth electrode layer disposed on the insulating layer, wherein the distal portion of the flexible film actuator is moveable with respect to the fourth electrode layer.

23. An electromagnetic radiation detector having an electrostatically driven MEMS chopper device, comprising:

a substrate;

a thermal isolation bridge disposed on said substrate;

a first electrode layer disposed on said thermal isolation bridge;

a detector material layer overlying on said thermal isolation bridge and in electrical contact with said first electrode layer;

a second electrode layer overlying said thermal isolation bridge, electrically isolated from said first electrode layer and in electrical contact with said detector material layer;

a support structure disposed on the substrate;

a transparent substrate attached to the support structure;

a transparent third electrode layer disposed on the transparent substrate; and

a flexible film actuator overlying the transparent third electrode and the detector material layer, the flexible film actuator having a fourth electrode layer and at least one biasing layer, a fixed portion attached to the transparent substrate and a distal portion movable with respect to the third electrode layer.

24. The detector of claim 23, wherein said substrate further comprises a read-out circuit disposed on the substrate.

25. The detector of claim 23, further comprising a first air gap between the substrate and the detector material layer.

26. The detector of claim 25, further comprising a second air gap between the transparent substrate and the absorbing layer.

27. The detector of claim 23, wherein the detector material layer is disposed between the first electrode layer and the second electrode layer.

28. The detector of claim 23, wherein the first and second electrode layers further comprise a material from the group consisting of gold, platinum, chromium, titanium, LSCO or ruthenium oxide.

29. The detector of claim 23, wherein the detector material layer further comprises a detector material chosen from the group consisting of lead zirconate titanate (PZT), lithium tantalate (LiTaO₃), lead titanium oxide (PbTiO₃), barium strontium titanate (BST), polyvinylidene fluoride (PVDF) and vanadium oxide.

30. The detector of claim 23, further comprising a an electromagnetic radiation absorbing layer overlying said first and second electrode layers and said detector material layer.

31. The detector of claim 23, wherein the fourth electrode layer of the flexible film actuator is disposed between a first biasing layer and a second biasing layer.

32. An electromagnetic radiation detector array having an electrostatically driven microelectromechanical system (MEMS) chopper array, comprising:

a substrate;

a plurality of detector pixels supported by said substrate, said detector pixels comprising;

a detector material layer; and

first and second electrodes in electrical contact with said detector material layer; and

a plurality of flexible film actuators, each actuator overlying said detector material layer of a corresponding detector pixel and moveable relative thereto to alternately allow passage of radiation to said detector material layer and block passage of radiation to said detector material layer.

33. The detector array of claim 32, wherein the substrate further comprises a silicon substrate having a read-out circuit disposed thereon.

34. The detector array of claim 32, further comprising a plurality of thermal isolation bridges disposed on the substrate that support the detector material layer corresponding to a detector pixel and provides thermal isolation between the detector pixel and the substrate.

35. The detector array of claim 32, wherein the plurality of detector pixels further comprises first and second electrodes disposed in layered formation on opposite sides of the detector material layer.

36. The detector array of claim 32, wherein the plurality of flexible film actuators further comprise a third electrode and a biasing element, each actuator having a fixed portion attached to an underlying surface and a distal portion moveable relative to the second electrode of the corresponding detector pixel.

37. The detector array of claim 32, further comprising a radiation-absorbing layer disposed between the plurality of flexible film actuators and the plurality of detector pixels.

38. The detector array of claim 32, wherein the detector material layer further comprises a detector material chosen from the group consisting of lead zirconium titanate (PZT), lithium tantalate (LiTaO₃), lead titanium oxide (PbTiO₃), barium strontium titanate (BST), polyvinylidene fluoride (PVDF) and vanadium oxide.

39. The detector array of claim 32, further comprising a transparent substrate supported by said substrate and a transparent electrode disposed on the transparent substrate, wherein the plurality of flexible film actuators are supported by and affixed to said transparent substrate and wherein said transparent substrate and transparent electrode are transparent to the electromagnetic radiation being detected.

40. The detector array of claim 39, further comprising an air gap separating the plurality of detector pixels from the transparent substrate.

41. The detector array of claim 39, further comprising a support structure disposed on the substrate for positioning and supporting said transparent substrate.

42. The detector array of claim 39, wherein the support structure further comprises a plurality of solder bumps.

43. The detector array of claim 39, wherein the support structure further comprises at least one epoxy attachment.

44. A method for pixel modulation in an electromagnetic radiation detector array, the method comprising:

providing for a plurality of electrostatically activated flexible film actuators, each actuator corresponding to one or more detector pixels in an electromagnetic radiation detector array;

pulsing one or more flexible film actuators to block passage of electromagnetic radiation and to allow passage of electromagnetic radiation to the one or more detector pixels corresponding to the flexible film actuator;

causing a temperature change in the one or more detector pixels as a result of the pulsing of the corresponding flexible film actuator;

changing an electrical property of the one or more detector pixels as a result of the temperature change in one or more detector pixels; and

generating a read-out current as a result of the change in the electrical property of the one or more detector pixels.

45. The method of claim 44, wherein pulsing one or more flexible film actuators further comprises:

activating, electrostatically, one or more flexible film actuators to block passage of electromagnetic radiation to the corresponding one or more detector pixels; and

deactivating, by releasing the electrostatic force, one or more flexible film actuators to allow passage of electromagnetic radiation to the corresponding one or more detector pixels.

46. The method of claim 44, wherein changing an electrical property of the one or more detector pixels further comprises changing a property of the one or more detector pixels chosen from the group consisting of polarization, capacitance or resistance.