Sensor

• US 20070138395A1
• Filed: 10/20/2006
• Published: 06/21/2007
• Est. Priority Date: 01/26/2005
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Hynes, Eamon, Coyne, Edward, Lane, William
• Granted Patent: US 8,487,260 B2
• Time in Patent Office: Days
• US Class Current: 250/353
• CPC Class Codes: G01J 1/04 Optical or mechanical part supplementary adjustable parts
• CPC Class Codes: G01J 1/0411 using focussing or collimating elements, i.e. lenses or mirrors; Aberration correction
• CPC Class Codes: G01J 5/0014 for sensing the radiation from gases, flames
• CPC Class Codes: G01J 5/02 Constructional details
• CPC Class Codes: G01J 5/0225 Shape of the cavity itself or of elements contained in or suspended over the cavity
• CPC Class Codes: G01J 5/024 Special manufacturing steps or sacrificial layers or layer structures
• CPC Class Codes: G01J 5/045 Sealings; Vacuum enclosures; Encapsulated packages; Wafer bonding structures; Getter arrangements getter arrangements per se H01L23/26 and H01L21/3221
• CPC Class Codes: G01J 5/06 Arrangements for eliminating effects of disturbing radiation; Arrangements for compensating changes in sensitivity for adjusting of solid angle of collected radiation G01J5/07; means for wavelength selection G01J5/0801
• CPC Class Codes: G01J 5/064 Ambient temperature sensor; Housing temperature sensor; Constructional details thereof
• CPC Class Codes: G01J 5/07 Arrangements for adjusting the solid angle of collected radiation, e.g. adjusting or orienting field of view, tracking position or encoding angular position optical collimating elements G01J5/0806
• CPC Class Codes: G01J 5/08 Optical arrangements
• CPC Class Codes: G01J 5/0803 Arrangements for time-dependent attenuation of radiation signals
• CPC Class Codes: G01J 5/0806 Focusing or collimating elements, e.g. lenses or concave mirrors
• CPC Class Codes: G01J 5/0846 having multiple detectors for performing different types of detection, e.g. using radiometry and reflectometry channels
• CPC Class Codes: G01J 5/10 using electric radiation detectors
• CPC Class Codes: G01J 5/24 Use of specially adapted circuits, e.g. bridge circuits
• CPC Class Codes: H01L 2924/16235 Connecting to a semiconductor or solid-state bodies, i.e. cap-to-chip
• CPC Class Codes: H01L 31/0203 Containers; Encapsulations , e.g. encapsulation of photodiodesfor photovoltaic devices H01L31/048; for organic photosensitive devices H10K30/80
• CPC Class Codes: H01L 31/02164 for shielding light, e.g. light blocking layers, cold shields for infrared detectors
• CPC Class Codes: H01L 31/0232 Optical elements or arrangements associated with the device H01L31/0236 takes precedence; for photovoltaic cells H01L31/054; for photovoltaic modules H02S40/20
• CPC Class Codes: H01L 31/02325 : the optical elements not being integrated nor being directly associated with the device

Abstract

The invention provides a sensor including a first sensor element formed in a first substrate and at least one optical element formed in a second substrate, the first and second substrates being configured relative to one another such that the second substrate forms a cap over the first sensor element, the at least one optical element being configured to guide incident radiation on the cap to the first sensor element. The sensor also includes a reference sensor element whose output can be used to reference the output of the first sensor element.

Claims

1. An electromagnetic radiation sensor having first and second sensor elements formed in a first substrate, and a first and second cap formed in a second substrate, the first and second substrates being arranged relative to one another such that each of the first and second sensor elements having a respective cap provided thereabove thereby providing first and second cells, and wherein the first cell provides an output based on a first response characteristic and the second cell provides an output based on a second response characteristic.

2. The sensor as claimed in claim 1 wherein the output of the second cell is lower than that of the first cell.

3. The sensor as claimed in claim 1 wherein the response characteristics of each of the first and second cells are a function of at least one of the following properties of each cell:

a) the optical response characteristic,

b) the electrical response characteristic,

c) the thermal response characteristic,

d) the nature of the radiation source used to illuminate each of the first and second cells.

4. The sensor as claimed in claim 1 wherein the cap for the first sensor element allows a transmission of incident radiation through the cap and onto the sensor element and the cap for the second sensor element blocks a transmission of radiation through the cap and onto the second sensor element.

5. The sensor as claimed in claim 1 wherein the cap for the second sensor element filters at least a portion of radiation that is incident on the second cell.

6. The sensor of claim 1 wherein the cap for the first sensor element includes an optical element configured to provide a focusing of the incident radiation onto the first sensor element.

7. The sensor of claim 1 wherein the cap for the second sensor element includes a reflective coating which reflects radiation incident on the cap.

8. The sensor of claim 1 wherein the cap for the second sensor element includes an optically opaque coating so as to prevent transmission of radiation through the cap and onto the second sensor element.

9. The sensor as claimed in claim 1 wherein the arrangement of the first and second substrates relative to one another define a cavity between each of the caps and their respective sensor elements.

10. The sensor as claimed in claim 9 wherein each of the cavities for the first and second sensor elements are in fluid communication with one another.

11. The sensor as claimed in claim 9 wherein each of the cavities for the first and second sensor elements are isolated from the other of the cavities for the first and second sensor element.

12. The sensor as claimed in claim 1 wherein the first and second substrates are provided in silicon.

13. The sensor as claimed in claim 1 wherein the first and second sensor elements are infra-red sensor elements.

14. The sensor as claimed in claim 6 wherein the at least one optical element is a diffractive optical element.

15. The sensor as claimed in claim 6 wherein the at least one optical element is a refractive optical element.

16. The sensor as claimed in claim 9 wherein the ambient conditions and composition within the cavities can be specified.

17. The sensor as claimed in claim 16 wherein the cavities are provided at a pressure lower than ambient pressure.

18. The sensor as claimed in claim 16 wherein the cavities are populated with a gaseous composition selected for the application with which the sensor is to be used.

19. The sensor as claimed in claim 18 wherein the gaseous composition comprises a gas having a thermal conduction less than the thermal conduction of nitrogen.

20. The sensor as claimed in claim 6 wherein the optical element is formed in an inner surface of the cap, adjacent to the cavity.

21. The sensor as claimed in claim 6 wherein the optical element is formed in an outer surface of the cap, remote from the cavity.

22. The sensor as claimed in claim 1 wherein optical elements are formed in both an outer surface and inner surface of the cap for the first sensor element, the combination of the optical elements adjacent to and remote from the cavity forming a compound lens.

23. The sensor as claimed in claim 6 wherein a plurality of sensor elements are formed and the optical element is configured to selectively guide radiation of specific wavelengths to preselected ones of the plurality of sensor elements.

24. The sensor as claimed in claim 1 wherein the caps for the first and second element are formed in the same second substrate, the sensor additionally comprising an outer cap, the outer cap being orientated over the second substrate, the outer cap including an optical element.

25. The sensor as claimed in claim 1 wherein on arranging each of the first and second substrates relative to one another each of the caps are formed by side walls extending upwardly from the first substrate and supporting a roof therebetween, the roof being in a plane substantially parallel to the sensor elements.

26. The sensor as claimed in claim 25 wherein each of the first and second sensor elements are adjacent to one another, the caps provided thereabove sharing a common central column, that extends downwardly from the roof, thereby defining chambers for each of the first and second sensor elements.

27. The sensor as claimed in claim 26 wherein the chamber for the second sensor element is treated to prevent a transmission of radiation through the cap and onto the second sensor element.

28. The sensor as claimed in claim 27 wherein the treatment includes a doping of the side walls of the chamber.

29. The sensor as claimed in claim 27 wherein the treatment includes the application of a reflective coating on the roof of the cap for the second sensor element.

30. The sensor as claimed in claim 26 wherein the central column does not extend fully from the roof to the first substrate, such that a gap is defined between a lower surface of the column and an upper surface of the first substrate.

31. The sensor as claimed in claim 30 wherein the width of the gap is comparable with the wavelength of the incident radiation being sensed.

32. The sensor as claimed in claim 30 wherein the provision of the gap allows for an equalisation of pressure between the chambers for the first and second sensor element.

33. The sensor as claimed in claim 1 wherein each of the first and second sensor elements are provided as a bolometer.

34. The sensor as claimed in claim 1 wherein at least a portion of one of the first and second sensor elements are suspended over a cavity defined in the first substrate, the cavity providing thermal insulation between the first substrate and the sensor element.

35. The sensor as claimed in claim 1 wherein the first and second sensor elements are arranged in a Wheatstone bridge configuration.

36. The sensor as claimed in claim 35 wherein the Wheatstone bridge configuration is provided by the first sensor element having a first pair of resistive elements and the second sensor element having a second pair of resistive elements, resistors from each pair defining opposite legs of the Wheatstone bridge.

37. The sensor as claimed in claim 36 wherein each of the resistors on opposite legs of the Wheatstone bridge are co-located on a thermally insulated table.

38. The sensor as claimed in claim 36 wherein the thermally insulated table is fabricated using micro-electro-mechanical techniques.

39. The sensor as claimed in claim 1 wherein the first substrate includes a trench arrangement located outside the sensor, the trench arrangement providing thermal insulation between the sensor and other elements on the first substrate.

40. The sensor as claimed in claim 39 wherein the trench arrangement includes at least two adjacent trenches etched in the first substrate, each of the at least two trenches being filled with a thermally insulating material and being separated from one another by an intermediary region, the intermediary region having a different thermal coefficient to either of the at least two trenches.

41. The sensor as claimed in claim 39 wherein the trench arrangement is located around the sensor element so as to define a thermal barrier around the sensor element.

42. The sensor as claimed in claim 39 wherein the trench arrangement is located between the sensor and a heat source provided on the first substrate.

43. The sensor as claimed in claim 39 wherein the trench arrangement includes a plurality of trenches.

44. The sensor as claimed in claim 43 wherein the plurality of trenches are provided in sets of trenches, each of the sets having at least two trenches separated from one another by an intermediary region, the intermediary region having a different thermal coefficient to either of the two trenches.

45. The sensor as claimed in claim 40 wherein the intermediary region is an evacuated cavity.

46. The sensor as claimed in claim 45 wherein the evacuated cavity is formed by etching a region of the substrate between the trenches.

47. The sensor as claimed in claim 46 wherein the depth of the evacuated cavity corresponds with the depth of at least one of the trenches.

48. The sensor as claimed in claim 47 wherein the etch defining the evacuated cavity is such that the evacuated cavity extends beneath at least a portion of the sensor.

49. The sensor as claimed in claim 48 wherein the horizontal dimension of the evacuated cavity is defined by the depth of the trenches.

50. The sensor as claimed in claim 40 wherein the first substrate is located on a buried silicon-on-insulator layer and the depth of the trenches forming the trench arrangement is such as to extend to the buried layer.

51. The sensor as claimed in claim 1 further including a plurality of die temperature sensors, the plurality of the die temperature sensors providing an output indicative of the temperature of the die on which the sensor is located.

52. The sensor as claimed in claim 51 wherein the plurality of die sensors are arranged about the die, so as to give a plurality of output measurements, each of the output measurements being related to the temperature at the location of that die temperature sensor.

53. A sensor array including a plurality of sensors, each of the sensors having an active sensor element and a reference sensor element, the active sensor element being formed in a first substrate and having an optical element formed in a second substrate, the first and second substrates being configured relative to one another such that the second substrate forms a cap over the sensor element, the optical element being configured to guide incident radiation on the cap to the sensing element, the reference sensor element also being formed in a first substrate and having a cap formed in a second substrate, the first and second substrates being configured relative to one another such that the cap is located over the reference sensor element, the cap serving to modify the intensity of incident radiation transmitted through to the reference sensor element such that the active and reference sensors have a different response characteristic.

54. The sensor array of claim 53 wherein an output of the sensor array defines an image plane.

55. A discriminatory sensor system configured to provide a signal on sensing a heat emitting body, the system including a first sensor configured to provide a signal on sensing the body a first distance from the sensor and a second sensor configured to provide a signal on sensing the object a second distance from the sensor, each of the first and second sensors including at least two sensing elements formed in a first substrate, each of the at least two sensing elements having a cap formed in a second substrate provided thereabove, and wherein the cap for the first sensing elements includes an optical element, the optical element being configured to guide incident radiation on the cap to the at least first sensing element to provide a signal indicative of the incident radiation on the first sensing element, the second sensing element provided a reference output.

56. The discriminatory sensor of claim 55 wherein the sensing elements of each of the first and second sensors are formed in the same substrate.

57. The discriminatory sensor of claim 55 wherein the object is a human torso.

58. A gas analyser including at least one sensor element formed in a first substrate and at least one optical element formed in a second substrate, the first and second substrates being configured relative to one another such that the second substrate forms a cap over the at least one sensor element, the at least one optical element being configured to guide incident radiation on the cap to the at least one sensor element, the incident radiation guided having a wavelength indicative of the presence of a specific gas, the gas analyser including at least one reference sensor element formed in the first substrate and having a cap for the at least one reference sensor element formed in a second substrate, the reference sensor element providing an output that useable with the output of the at least one sensor element to provide an analysis of the gas.

59. The analyser of claim 58 wherein the output of the reference sensor element is independent of the output of the at least one sensor element.

60. The analyser of claim 59 wherein the cap of the reference sensor element shields the reference sensor element from the incident radiation on the cap such that the reference sensor element provides an output independent of the intensity of the incident radiation.

61. The gas analyser of claim 58 including a plurality of sensor elements and a plurality of associated optical elements therefore, each of the combined sensor elements and optical elements being configured for specific wavelength analysis such that the output of the plurality of sensor elements may be used to provide a gas wavelength signature spectrum.

62. A method of forming a sensor, the method including the steps of:

forming at least one sensor element and at least one reference sensor element in a first substrate,

forming an optical element and a shielding cap in a second substrate,

bonding the first and second substrates together such that the second substrate provides the optical element over the sensor element, the optical element being configured to guide incident radiation onto the sensor element, and the second substrate provides the shielding cap over the reference sensor, the shielding cap serving to modify a transmission of radiation incident on the cap through and onto the reference sensor element.

63. An electromagnetic radiation sensor fabricated in a semiconductor process, the sensor including first and second sensing elements formed in a first substrate, each of the first and second substrates having a respective cap defined thereabove, the caps being formed in a second substrate and being mountable onto the first substrate and wherein the cap formed over the first sensing element allows a transmission of radiation through the cap onto the sensing element and the cap formed over the second sensing element filters the transmission of radiation through the cap onto the sensing element so as to reduce the radiation incident onto the second sensing element relative to that incident onto the first sensing element.