Doped, organic carbon-containing sensor for infrared detection and a process for the preparation thereof

• US 6,489,616 B2
• Filed: 03/19/2001
• Issued: 12/03/2002
• Est. Priority Date: 03/19/2001
• Status: Expired due to Term

• Current Assignee: Board of Governors of Southwest Missouri State University
• Original Assignee: Board of Governors of Southwest Missouri State University
• Inventors: Giedd, Ryan E.
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): MORAN, TIMOTHY J
• Application Number:
  US09/811,908
• Publication Number:
  US 20020134939A1
• Time in Patent Office: 624 Days
• Field of Search: 250/338.1, 250/338.3, 250/339.14, 250/340, 250/330, 250/332
• US Class Current: 250/338.1
• CPC Class Codes: G01J 5/04 Casings
• CPC Class Codes: G01J 5/046 Materials; Selection of thermal materials
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• CPC Class Codes: H01L 27/14669 Infrared imagers

Abstract

The present invention is directed to an uncooled, infrared detector which includes a sensor having an amorphous surface layer containing organic carbon and a high dopant concentration which possesses an improved temperature coefficient of resistivity, as well as improved responsivity, and which may be patterned to form a focal plane array by means of common microlithographic techniques. The present invention is additionally directed to an “ion beam mixing” process for preparing the present infrared sensor.

Claims

1. An infrared detector comprising:

a substrate;

a sensor having a segment thermally isolated from the substrate and a resistivity which varies as a function of temperature, the segment comprising an amorphous layer containing organic carbon and a dopant, the concentration of the dopant in the amorphous layer being at least about 1×

10²⁰ atoms/cm³, the dopant being aluminum, an element having an atomic number greater than 18, or a mixture thereof; and

,

contacts electrically connected to the segment, the segment being energizable via said contacts.

2. The detector of claim 1 wherein the concentration of the dopant in the amorphous layer is at least about 1×

10²¹ atoms/cm³.

3. The detector of claim 1 wherein the concentration of the dopant in the amorphous layer is at least about 1×

10²² atoms/cm³.

4. The detector of claim 1 wherein the dopant is selected from silver, gold, copper, chromium, strontium, lead, tin, indium, cadmium, bismuth, antimony, zinc, thallium, germanium, gallium, tellurium, arsenic or a mixture thereof.

5. The detector of claim 4 wherein the dopant is selected from copper, chromium, silver, tellurium or a mixture thereof.

6. The detector of claim 1 wherein the organic carbon of the amorphous layer is derived from an organic polymer selected from a substituted or unsubstituted vinyl polymer, polyether, polyamide, polyimide, polyester or copolymer thereof.

7. The detector of claim 6 wherein the polymer is a substituted or unsubstituted vinyl polymer selected from polystyrene, polyacrylonitrile or copolymer thereof.

8. The detector of claim 6 wherein the polymer is poly(etheretherketone) and the dopant is tellurium.

9. The detector of claim 1 further comprising readout or processing circuitry disposed between the sensor and the substrate and in electrical contact with the sensor.

10. The detector of claim 1 wherein the substrate is selected from the group consisting of non-conductive, inorganic insulators and polymers.

11. The detector of claim 10 wherein the substrate is a non-conductive, inorganic insulator selected from the group consisting of glass, quartz, aluminum oxide, silicon dioxide and silicon nitride.

12. The detector of claim 10 wherein the substrate is a non-conductive polymer selected from the group consisting of polyimides, polyesters and halogenated vinyl polymers.

13. The detector of claim 1 wherein the substrate is a metal or semiconductor, the detector further comprising an insulating layer disposed between the substrate and the sensor.

14. The detector of claim 1 wherein the thermally isolated segment of the sensor is spaced from and above the substrate surface, forming a bridge there over.

15. The detector of claim 1 wherein, at the bridge apex, the distance between the bottom of the sensor and the substrate is about one-quarter the wavelength of the infrared radiation to be detected.

16. The detector of claim 15 wherein said infrared radiation has a wavelength ranging from about 1 to about 3 micrometers.

17. The detector of claim 15 wherein said infrared radiation has a wavelength ranging from about 3 to about 5 micrometers.

18. The detector of claim 15 wherein said infrared radiation has a wavelength ranging from about 8 to about 14 micrometers.

19. The detector of claim 1 wherein the sensor has an average emmisivity ranging from greater than about 0.75 to less than about 0.95.

20. The detector of claim 1 wherein the sensor has a temperature coefficient of resistivity of at least about 2%/K at room temperature.

21. The detector of claim 1 wherein the detector is a bolometer, said bolometer detector having a thermal time constant of less than about 20 microseconds.

22. The detector of claim 1 wherein the sensor has a responsivity of at least about 5000 V/W.

23. The detector of claim 1 wherein the sensor has a resistivity of less than about 20 Mohms/square.

24. The detector of claim 1 wherein an array of said sensors are present on the substrate surface, each sensor having contacts electrically connected to the sensor segment.

25. The focal plane array detector of claim 24 wherein the array comprises at least about a 480×

640 configuration of sensor on the substrate.

26. The focal plane array detector of claim 25 wherein the resistivity of each sensor in the array differs by less than about 2%.

27. The focal plane array detector of claim 25 wherein the array has a fill factor ranging from about 90% to about 95%.

28. An infrared detector comprising:

a substrate;

a sensor having a segment thermally isolated from the substrate and a resistivity which varies as a function of temperature, the segment comprising an amorphous layer containing organic carbon and a dopant, the sensor having a responsivity of at least about 5000 V/W; and

,

contacts electrically connected to the segment, the segment being energizable via said contacts.

29. The detector of claim 28 wherein the responsivity ranges from about 6,500 to less than about 10,500 V/W.

30. The detector of claim 28 wherein the concentration of the dopant in the amorphous layer is at least about 1×

10²¹ atoms/cm³.

31. The detector of claim 30 wherein the dopant is selected from copper, chromium, silver, tellurium or a mixture thereof.

32. The detector of claim 28 wherein the organic carbon of the amorphous layer is derived from an organic polymer selected from a substituted or unsubstituted vinyl polymer, polyether, polyamide, polyimide, polyester or copolymer thereof.

33. The detector of claim 32 wherein the polymer is poly(etheretherketone) and the dopant is tellurium.

34. The detector of claim 28 wherein the sensor has a temperature coefficient of resistivity of at least about 2%/K at room temperature.

35. The detector of claim 28 wherein an array of said sensors are present on the substrate surface, each sensor having contacts electrically connected to the sensor segment, the resistivity of each sensor in the array differing by less than about 2%.

36. An infrared detector comprising:

a substrate;

a sensor having a segment thermally isolated from the substrate and a resistivity which varies as a function of temperature, the segment comprising an amorphous layer containing organic carbon and a dopant, the sensor having a temperature coefficient of resistivity of at least about 2%/K; and

,

contacts electrically connected to the segment, the segment being energizable via said contacts.

37. The detector of claim 36 wherein the temperature coefficient of resistivity ranges from about 2%/K to about 4.5%/K at room temperature.

38. The detector of claim 36 wherein the responsivity is at least about 5000 V/W.

39. The detector of claim 36 wherein the concentration of the dopant in the amorphous layer is at least about 1×

10²¹ atoms/cm³.

40. The detector of claim 39 wherein the dopant is selected from copper, chromium, silver, tellurium or a mixture thereof.

41. The detector of claim 36 wherein the organic carbon of the amorphous layer is derived from an organic polymer selected from a substituted or unsubstituted vinyl polymer, polyether, polyamide, polyimide, polyester or copolymer thereof.

42. The detector of claim 41 wherein the polymer is poly(etheretherketone) and the dopant is tellurium.

43. The detector of claim 36 wherein an array of said sensors are present on the substrate surface, each sensor having contacts electrically connected the sensor segment, the resistivity of each sensor in the array differing by less than about 2%.

44. An infrared detector comprising:

a substrate;

a sensor having a segment thermally isolated from the substrate and a resistivity which varies as a function of temperature, the segment comprising an ion beam mixed layer containing organic carbon and a dopant other than carbon, the concentration of the dopant in the ion beam mixed layer being at least about 1×

10²⁰ atoms/cm³, the ion beam mixed layer being formed by ion beam mixing of a target layer and an organic layer wherein the target layer comprises a source of the dopant; and

,

contacts electrically connected to the segment, the segment being energizable via said contacts.

45. The detector of claim 44 wherein the dopant in the ion beam mixed layer is p-type, n-type, a metal or a mixture thereof.

46. The detector of claim 44 wherein the concentration of the dopant in the ion beam mixed layer is at least about 1×

10²¹ atoms/cm³.

47. The detector of claim 44 wherein the dopant is selected from silver, gold, copper, chromium, strontium, lead, tin, indium, cadmium, bismuth, antimony, zinc, thallium, germanium, gallium, tellurium, arsenic, aluminum, lithium, manganese or a mixture thereof.

48. The detector of claim 47 wherein the dopant is selected from copper, chromium, silver, tellurium or a mixture thereof.

49. The detector of claim 44 wherein the organic carbon of the amorphous layer is derived from an organic polymer selected from a vinyl polymer, a polyether, a polyamide, a polyimide, a polyester or copolymer thereof.

50. The detector of claim 44 wherein the sensor has a temperature coefficient of resistivity of at least about 2%/K at room temperature.

51. The detector of claim 44 wherein the sensor has a responsivity of at least about 5000 V/W.

52. The detector of claim 44 wherein an array of said sensors are present on the substrate surface, each sensor having contacts electrically connected the sensor segment, the resistivity of each sensor in the array differing by less than about 2%.

53. A process for detecting infrared radiation, the process comprising:

passing an electrical current through a sensor of an infrared detector, the sensor having a segment thermally isolated from a substrate of the detector and a resistivity which varies as a function of temperature, the segment comprising an amorphous layer containing organic carbon and a dopant, the concentration of the dopant in the amorphous layer being at least about 1×

10²⁰ atoms/cm³, the dopant being aluminum, an element having an atomic number greater than 18, or a mixture thereof; and

,

detecting a resistivity change in the sensor caused by the absorption of heat from infrared radiation impinging the sensor.

54. The process of claim 53 wherein the concentration of the dopant in the amorphous layer is at least about 1×

10²¹ atoms/cm³.

55. The process of claim 53 wherein the dopant is selected from silver, gold, copper, chromium, strontium, lead, tin, indium, cadmium, bismuth, antimony, zinc, thallium, germanium, gallium, tellurium, arsenic or a mixture thereof.

56. The process of claim 55 wherein the dopant is selected from copper, chromium, silver, tellurium or a mixture thereof.

57. The process of claim 53 wherein the organic carbon of the amorphous layer is derived from an organic polymer selected from a vinyl polymer, a polyether, a polyamide, a polyimide, a polyester or copolymer thereof.

58. The process of claim 53 wherein the thermally isolated segment of the sensor is spaced from and above the substrate surface, wherein the thermally isolated segment of the sensor forms a bridge.

59. The process of claim 53 wherein, at the bridge apex, the distance between the bottom of the sensor and the substrate is about one-quarter the wavelength of the infrared radiation to be detected.

60. The process of claim 59 wherein said infrared radiation has a wavelength ranging from about 1 to about 3 micrometers.

61. The process of claim 59 wherein said infrared radiation has a wavelength ranging from about 3 to about 5 micrometers.

62. The process of claim 59 wherein said infrared radiation has a wavelength ranging from about 8 to about 14 micrometers.

63. The process of claim 53 wherein the detection of a resistivity change occurs at room temperature.

64. The process of claim 53 wherein the sensor has a temperature coefficient of resistivity of at least about 2%/K at room temperature.

65. The process of claim 53 wherein said sensor has a responsivity of at least about 5,000 V/W.

66. A process for preparing an infrared detector, the process comprising:

forming an organic layer on a substrate;

forming a target layer comprising a dopant on the organic layer; and

,

contacting the target layer with an ion beam to form an infrared sensor on the substrate, the sensor having a segment thermally isolated from the substrate and a resistivity which varies as a function of temperature, the segment comprising an ion beam mixed layer containing organic carbon derived from the organic layer and a dopant other than carbon from the target layer, the concentration of the dopant in the ion beam mixed layer being at least about 10²⁰ atoms/cm³.

67. The process of claim 66 further comprising, prior to said organic layer formation, forming an insulating layer on the substrate.

68. The process of claim 67 further comprising forming readout or processing circuitry, said circuitry being disposed between the insulating layer and the organic layer.

69. The process of claim 68 further comprising forming electrical current supplying and receiving pathways, said pathways being disposed between the circuitry and the organic layer and comprising gold, nickel, copper, titanium, tungsten or a mixture thereof.

70. The process of claim 66 further comprising forming an array of discrete regions of the sensor on the substrate.

71. The process of claim 70 further comprising forming electrical current supplying and receiving pathways to each sensor in the array.

72. The process of claim 70 wherein thermal isolation of the segment of each sensor in the array is achieved by etching a portion of the substrate beneath each segment to form an absorption cavity, each segment being. spaced from and above the cavity.

73. The process of claim 72 wherein the array comprises at least about a 480×

640 configuration of sensors.

74. The process of claim 73 wherein the resistivity of each sensor in the array differs by less than about 2%.

75. The process of claim 73 wherein the array has a fill factor ranging from about 90% to about 95%.

76. The process of claim 66 wherein the dopant in the ion beam mixed layer is p-type, n-type, a metal or a mixture thereof.

77. The process of claim 66 wherein the concentration of the dopant in the ion beam mixed layer is at least about 1×

10²¹ atoms/cm³.

78. The process of claim 66 wherein the dopant is selected from silver, gold, copper, chromium, strontium, lead, tin, indium, cadmium, bismuth, antimony, zinc, thallium, germanium, gallium, tellurium, arsenic, aluminum, manganese, lithium or a mixture thereof.

79. The process of claim 78 wherein the dopant is selected from copper, chromium, silver, tellurium or a mixture thereof.

80. The process of claim 66 wherein the organic layer is an organic polymer layer, the polymer being selected from a vinyl polymer, a polyether, a polyamide, a polyimide, a polyester or copolymer thereof.

81. The process of claim 66 wherein the sensor has a temperature coefficient of resistivity of at least about 2%/K at room temperature.

82. The process of claim 66 wherein the sensor has a responsivity ranging from at least about 5,000 to less than about 15000 V/W.

83. The process of claim 66 wherein the ion beam dose ranges from about 1×

10¹⁴ ions/cm² to about 1×

10¹⁷ ions/cm².

84. The process of claim 66 wherein the ion beam energy ranges from about 25 to about 100 KeV.