Spectrally tunable detector

• US 20030173504A1
• Filed: 03/18/2002
• Published: 09/18/2003
• Est. Priority Date: 03/18/2002
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Cole, Barrett E., Higashi, Robert E., Subramanian, Arunkumar, Krishnankutty, Subash
• Granted Patent: US 7,015,457 B2
• Time in Patent Office: Days
• US Class Current: 250/226
• CPC Class Codes: G01B 11/272 using photoelectric detection means
• CPC Class Codes: G01J 3/26 using multiple reflection, e.g. Fabry-Perot interferometer, variable interference filters
• CPC Class Codes: G01J 3/36 Investigating two or more bands of a spectrum by separate detectors
• CPC Class Codes: G01J 3/427 Dual wavelengths spectrometry
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G02B 5/284 of etalon type comprising a resonant cavity other than a thin solid film, e.g. gas, air, solid plates etalons for fibre optic multiplexing G02B6/29358; etalons for spectral measurement G01J3/26
• CPC Class Codes: H01L 2224/05568 the whole external layer protruding from the surface
• CPC Class Codes: H01L 2224/05573 Single external layer
• CPC Class Codes: H01L 2224/13 of an individual bump connector
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 27/14621 Colour filter arrangements
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 31/02024 Position sensitive and lateral effect photodetectors; Quadrant photodiodes
• CPC Class Codes: H01L 31/02162 for filtering or shielding light, e.g. multicolour filters for photodetectors
• CPC Class Codes: H01L 31/02325 the optical elements not being integrated nor being directly associated with the device

Abstract

A spectrally tunable optical detector and methods of manufacture therefore are provided. In one illustrative embodiment, the tunable optical detector includes a tunable bandpass filter, a detector and readout electronics, each supported by a different substrate. The substrates are secured relative to one another to form the spectrally tunable optical detector.

Claims

1. A spectrally tunable detector, comprising:

a tunable bandpass filter having a first at least partially reflective plate and a second at least partially reflective plate separated by a separation gap, the tunable bandpass filter is selectively tuned to a bandpass wavelength by moving the first plate and/or the second plate relative to one another to change the separation gap; and

a detector positioned adjacent the tunable bandpass filter to receive one or more wavelengths that are passed by the tunable bandpass filter and to provide an output signal in response thereto.

2. A spectrally tunable detector according to claim 1 wherein the tunable bandpass filter and the detector are fixed relative to one another.

3. A spectrally tunable detector according to claim 1 wherein the tunable bandpass filter is provided on a first substrate and the detector is provided on a second substrate, the first substrate and the second substrate being substantially transparent to the one or more wavelengths that are passed by the tunable bandpass filter.

4. A spectrally tunable detector according to claim 3 wherein first substrate is fixed relative to the second substrate.

5. A spectrally tunable detector according to claim 3 wherein an incoming light beam enters the tunable bandpass filter and subsequently passes through the first substrate.

6. A spectrally tunable detector according to claim 5 wherein the incoming light beam subsequently enters the detector through the second substrate.

7. A spectrally tunable detector according to claim 6 wherein the first plate and the second plate of the tunable bandpass filter are positioned on a surface of the first substrate that is opposite to the surface that is adjacent the second substrate.

8. A spectrally tunable detector according to claim 7 further comprising a read out circuit provided on a third substrate.

9. A spectrally tunable detector according to claim 8 wherein the detector is electrically connected to the read out circuit.

10. A spectrally tunable detector according to claim 8 wherein the third substrate is mounted to a package.

11. A spectrally tunable detector according to claim 3 wherein a lens is positioned adjacent the first substrate.

12. A spectrally tunable detector, comprising:

a tunable bandpass filter for selectively passing a band of wavelengths from a predetermined spectral range of wavelengths, the tunable bandpass filter having an etalon with a top plate and a bottom plate that are separated by a separation gap, both the top plate and the bottom plate having a reflective portion that is at least partially reflective, the top plate and/or bottom plate adapted to move relative to the other plate to vary the separation gap across a predetermined range of separation gaps, the separation gap at least partially determining the band of wavelengths that are passed by the tunable bandpass filter and the predetermined range of separation gaps at least partially determining the predetermined spectral range of wavelengths; and

a detector positioned adjacent the tunable bandpass filter, the detector being sensitive to the predetermined spectral range of wavelengths.

13. A spectrally tunable detector according to claim 12 wherein the etalon is a Micro Electro Optical Mechanical System (MEOMS) etalon.

14. A spectrally tunable detector according to claim 13 wherein the bottom plate is positioned atop a substrate.

15. A spectrally tunable detector according to claim 14 wherein the top plate is positioned above the substrate, and mechanically connected to the substrate by one or more support legs.

16. A spectrally tunable detector according to claim 15 further including one or more top electrodes coupled to the top plate.

17. A spectrally tunable detector according to claim 16 further including one or more bottom electrodes coupled to the substrate.

18. A spectrally tunable detector according to claim 17 further comprising a control circuit for applying a voltage between one or more of the top electrodes and one or more of the bottom electrodes to pull at least part of the top plate closer to at least part of the bottom plate via an electrostatic force to thereby reduce the separation gap between the reflective portion of the top plate and the reflective portion of the bottom plate.

19. A spectrally tunable detector according to claim 18 wherein the substrate is Pyrex.

20. A spectrally tunable detector according to claim 12 wherein the detector is an AlGaN diode.

21. A spectrally tunable detector according to claim 12 further comprising a lens for directing an incoming light beam to the tunable bandpass filter.

22. A spectrally tunable detector according to claim 12 wherein the bandpass filter is adapted to allow only a single band of wavelengths from the predetermined spectral range of wavelengths for each separation gap in the predetermined range of separation gaps.

23. A tunable bandpass filter comprising:

a substrate;

a lower at least partially reflective mirror secured to the substrate;

one or more lower electrodes secured to the substrate;

an upper at least partially reflective mirror suspended above the lower mirror by a support member; and

one or more upper electrodes suspended above the one or more lower electrodes, the one or more upper electrodes secured to the support member;

whereby when a voltage is applied between the one or more lower electrodes and the one or more upper electrodes, an electrostatic force causes at least part of the support member to move closer to the substrate which causes the upper mirror to move closer to the lower mirror.

24. A tunable bandpass filter according to claim 23 wherein the support member is secured to the substrate through one or more posts that extend upward from the substrate.

25. A tunable bandpass filter according to claim 24 wherein the electrostatic force causes the support member to deform between one or more of the posts and the upper mirror.

26. A tunable bandpass filter according to claim 25 wherein the one or more upper electrodes are electrically connected through one or more of the posts to a conductive element that is secured to the substrate.

27. A tunable bandpass filter according to claim 25 wherein the voltage that is applied between a first lower electrode and a first upper electrode is different from the voltage that is applied between a second lower electrode and a second upper electrode.

28. A tunable bandpass filter according to claim 25 wherein the upper at least partially reflective mirror is positioned closer to the substrate than the one or more upper electrodes.

29. A method for making a tunable bandpass filter, comprising:

providing a first substrate;

providing a support layer adjacent the first substrate;

providing an upper mirror adjacent the support layer;

patterning the upper mirror;

providing an upper electrode layer adjacent the support layer;

patterning the upper electrode layer to provide one or more upper electrodes;

providing a second substrate;

providing a lower mirror adjacent the second substrate;

providing a lower electrode layer adjacent the second substrate;

patterning the lower electrode layer to provide one or more lower electrodes that are in substantial registration with the one or more upper electrodes;

providing one or more posts that extend in an upward direction relative to the second substrate;

providing a sacrificial layer over the upper mirror and the one or more upper electrodes, and/or over the lower mirror and the one or more lower electrodes;

positioning the first substrate and the second substrate together so that the upper mirror and the one or more upper electrodes are facing and are in substantial registration with the lower mirror and the one or more lower electrodes, respectively, with the sacrificial layer situated therebetween;

applying heat and pressure, and then cooling;

removing the first substrate;

patterning the support layer to expose at least part of the upper mirror while maintaining a mechanical connection between the upper mirror and the support layer; and

removing the sacrificial layer.

30. A method according to claim 29 further comprising securing the support layer to one or more of the posts.

31. A method according to claim 29 wherein the sacrificial layer providing step includes:

providing a first sacrificial layer of a first type over the lower mirror and the one or more lower electrodes;

providing a second sacrificial layer of a second type over the first sacrificial layer; and

providing a third sacrificial layer of the second type over the upper mirror and the one or more upper electrodes.

32. A method for making a tunable bandpass filter, comprising:

providing a substrate;

providing a lower mirror above the substrate;

providing a lower electrode layer above substrate;

patterning the lower electrode layer to provide one or more lower electrodes and one or more upper electrode pads;

providing a sacrificial layer adjacent the one or more lower electrodes, the one or more upper electrode pads, and the lower mirror;

providing holes through the sacrificial layer, selected holes being in registration with the one or more upper electrode pads;

providing a conductive layer above the sacrificial layer;

patterning the conductive layer to provide one or more upper electrodes that are in registration with the one or more lower electrodes, and to provide a conductive path from the one or more upper electrodes to one or more of the holes;

providing an upper mirror;

providing a support layer over the upper mirror;

patterning the support layer and any intervening layers between the support layer and the upper mirror to expose at least part of the upper mirror while maintaining a mechanical connection between the upper mirror and the support layer; and

removing the sacrificial layer.

33. A method according to claim 32 wherein the support layer extends into the one or more etched holes.

34. A method according to claim 32 wherein the conductive layer extends into the one or more etched holes and makes electrical connection to the one or more upper electrode pads.

35. A method according to claim 34 wherein the first sacrificial layer is Alumina passivation.

36. A method according to claim 34 wherein the second sacrificial layer is polyimide.

37. A method according to claim 34 wherein the first sacrificial layer is removed using a wet etch.

38. A method according to claim 34 wherein the second sacrificial layer is removed using a dry etch.

34-1. A method for making a tunable bandpass filter, comprising:

providing a substrate;

providing a lower mirror above the substrate;

providing a lower electrode layer above substrate;

patterning the lower electrode layer to provide one or more lower electrodes and one or more upper electrode pads;

providing a first sacrificial layer adjacent the lower mirror;

providing an upper mirror adjacent the first sacrificial layer;

providing a second sacrificial layer above the upper mirror;

providing holes through the second sacrificial layer, selected holes being in registration with the one or more upper electrode pads and selected holes being in registration with the upper mirror;

providing a conductive layer above the sacrificial layer;

patterning the conductive layer to provide one or more upper electrodes that are in registration with the one or more lower electrodes, and to provide a conductive path from the one or more upper electrodes to one or more of the holes and eventually to one or more upper electrode pads;

providing a support layer adjacent the second sacrificial layer;

patterning the support layer and any intervening layers between the support layer and the upper mirror above at least part of the upper mirror while maintaining a mechanical connection between the upper mirror and the support layer; and

removing the first and second sacrificial layers.

39. An electrostatically actuated structure, comprising:

a substrate;

one or more lower electrodes secured relative to the substrate;

one or more upper electrodes suspended above the one or more lower electrodes; and

the one or more upper electrodes positioned on a support layer, wherein the support layer has two or more elongated legs that extend in at least two lateral directions away from the one or more upper electrodes, each leg is secured to a supporting post that extends upward from the substrate.

40. An electrostatically actuated structure according to claim 39 wherein the support layer has two legs, each leg extending on an opposite direction from the one or more upper electrodes.

41. An electrostatically actuated structure according to claim 40 wherein each of the two legs extends substantially the same distance from the one or more upper electrodes.

42. An electrostatically actuated structure according to claim 39 wherein the support layer is “

H”

shaped having a first electrode leg portion and a second electrode leg portion spaced from one another and connected by a bridge portion, the first electrode leg portion having a first elongated support leg extending outward in a first direction to a first supporting post and a second elongated support leg extending outward in the opposite direction to a second supporting post, the second electrode leg portion having a first elongated support leg extending outward in the first direction to a third supporting post and a second elongated support leg extending outward in the opposite direction to a fourth supporting post, the electrostatically actuated structure further having another support leg extending from the bridge portion in the space between the first electrode leg portion and the second electrode leg portion.

43. An electrostatically actuated structure according to claim 42 wherein the support leg extending from the bridge portion is connected to a support structure that supports a mirror that is suspended above the substrate.

44. An electrostatically actuated structure according to claim 39 wherein the support layer has a first electrode leg portion and a second electrode leg portion spaced from one another and connected by a bridge portion, the first electrode leg portion and the second electrode leg portion being laterally offset relative to one other but overlapping at least at the bridge portion, the first electrode leg portion having a first elongated support leg extending outward in a first direction to a first supporting post and a second elongated support leg extending outward in the opposite direction to a second supporting post, the second electrode leg portion having a first elongated support leg extending outward in the first direction to a third supporting post and a second elongated support leg extending outward in the opposite direction to a fourth supporting post, the electrostatically actuated structure further having another support leg extending from the bridge portion in the space between the first electrode leg portion and the second electrode leg portion.

45. An electrostatically actuated structure according to claim 44 wherein the first electrode leg portion includes a first electrode and a second electrode, wherein the first electrode is positioned adjacent the bridge portion and the second electrode §

is positioned adjacent to but substantially electrically insulated from the first electrode.

46. An electrostatically actuated structure according to claim 45 wherein the first electrode can be separately energized from the second electrode.

47. An electrostatically actuated structure according to claim 45 wherein the second electrode leg portion includes a first electrode and a second electrode, wherein the first electrode is positioned adjacent the bridge portion and the second electrode is positioned adjacent to but substantially electrically insulated from the first electrode.