Antiblooming imaging apparatus, systems, and methods

• US 20080122956A1
• Filed: 11/28/2006
• Published: 05/29/2008
• Est. Priority Date: 11/28/2006
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Xu, Chen, Karasev, Igor, Agranov, Gennadiy
• Granted Patent: US 7,675,093 B2
• Time in Patent Office: Days
• US Class Current: 348/249
• CPC Class Codes: H04N 25/623 by evacuation via the output or reset lines
• CPC Class Codes: H04N 25/75 Circuitry for providing, modifying or processing image signals from the pixel array
• CPC Class Codes: H04N 25/77 Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components

Abstract

Apparatus, systems and methods are described to assist in reducing dark current in an active pixel sensor. A potential barrier arrangement is configured to block the flow of charge carriers generated outside a photosensitive region. In various embodiments, a potential well-potential barrier arrangement is formed to direct charge carriers away from the photosensitive region during an integration time.

Claims

1. A method comprising:

collecting photogenerated charge in a first potential region;

blocking transfer of a charge from a second potential region to the first potential region using a first voltage; and

transferring a charge from the second potential region to a third potential region using a second voltage, wherein the second voltage is less than the first voltage during an integration time associated with collecting photogenerated charge.

2. The method of claim 1, wherein collecting a photogenerated charge includes storing photogenerated carriers for at least the integration time.

3. The method of claim 1, wherein blocking transfer of a charge includes blocking charge carriers accumulated in the second potential region.

4. The method of claim 3, wherein blocking transfer of a charge includes blocking accumulated charge carriers associated with at least one of a photogenerated charge, a drift field, and a diffusion current.

5. The method of claim 1, wherein blocking transfer of a charge includes reducing a transfer of charge carriers formed in a fourth potential region located between the first potential region and the second potential region.

6. The method of claim 5, wherein the reducing a transfer of charge includes reducing a transfer of photogenerated charge carriers collected in the second potential region.

7. The method of claim 1, wherein transferring a charge includes transferring a portion of the charge based on the difference between the first voltage and the second voltage.

8. The method of claim 1, wherein transferring a charge includes removing a portion of the second electrical charge based on a difference between at least one of the first voltage and a third voltage and the second voltage and a third voltage, wherein the second voltage is adjusted to be greater than the third voltage during the integration time.

9. A method comprising:

converting photons to electrons in a first potential energy region at a predetermined rate;

storing the electrons in the first potential energy region during an integration time; and

adjusting a first barrier energy relative to at least one of a second barrier energy and a third barrier energy to reduce the transfer of electrons from the second potential energy region to the first potential energy region during the integration time.

10. The method of claim 9, wherein converting photons to electrons includes converting photons having an energy range associated with a predetermined frequency band.

11. The method of claim 9, wherein converting photons to electrons includes converting photons associated with at least one of automobile light, sunlight, starlight, moonlight, and thermal energy.

12. The method of claim 9, wherein the converting photons to electrons includes selectively converting photons using at least one of a filter, a semiconductor band gap, and a reflective surface coating.

13. The method of claim 9, wherein storing includes accumulating electrons during the integration time using at least one of a lens and a shutter.

14. The method of claim 9, wherein storing includes accumulating electrons using a dopant atom adjusted barrier potential.

15. The method of claim 9, wherein storing includes accumulating electrons generated from photons associated with at least one of a visible wavelength, an ultraviolet wavelength, and an infrared wavelength.

16. The method of claim 9, wherein adjusting a first barrier energy relative to at least one of a second barrier energy and a third barrier energy includes applying one of a first voltage, a second voltage, and a third voltage.

17. The method of claim 9, wherein adjusting a first barrier energy relative to at least one of a second barrier energy and a third barrier energy includes using a dopant atom profile.

18. An active pixel sensor comprising:

a photosensitive region including a pinned photodiode structure, the pinned photodiode structure operatively coupled to an n-type conductivity region;

a first electron gate located adjacent to the n-type conductivity region and to the photosensitive region, the first electron gate operatively coupled to an adjustable voltage; and

a second electron gate located adjacent the n-type conductivity region and to a drain region, the second electron gate operatively coupled to the first electron gate, wherein a second electron barrier associated with the second electron gate is less than a first electron barrier associated with the first electron gate, and wherein a drain potential associated with the drain region is less than a first potential associated with the n-type conductivity region during an integration time.

19. The active pixel sensor of claim 18, wherein the first electron barrier is configured to limit the transmission of electrons from the n-type conductivity region to the photosensitive region during the integration time.

20. The active pixel sensor of claim 18, wherein the first electron barrier is greater than the second electron barrier, a third electron barrier associated with a region adjacent the pinned photodiode structure, and the drain potential.

21. The active pixel sensor of claim 18, wherein first electron barrier and the second electron barrier are formed from the same semiconductor material with different dopant profiles.

22. The active pixel sensor of claim 21, wherein the semiconductor material is selected from a group consisting essentially of Si, Ge, and C.

23. The active pixel sensor of claim 18, wherein the photosensitive material includes at least one of a Si, a SiC, a SiGe, and a SiGeC.

24. The active pixel sensor of claim 18, wherein the photosensitive region is configured to generate carriers using light of a predetermined wavelength range.

25. The active pixel sensor of claim 18, wherein the first electron barrier is configured to block transmission of electrons from the n-type conductivity region to the photoactive region using a doping profile.

26. The active pixel sensor of claim 18, wherein the pinned photodiode structure is adapted to absorb light of a predetermined wavelength range.

27. The active pixel sensor of claim 18, wherein the photosensitive region is configured to receive light using a filter material attached to a substrate supporting the photosensitive region.

28. The active pixel sensor of claim 27, wherein the photosensitive region is configured to receive light using an antireflective material attached to at least one of the filter material and the substrate.

29. An imager comprising:

a filter formed to transmit light within a predetermined wavelength range; and

a pixel matrix configured to receive the light through the filter, the pixel matrix comprising an N×

M array of selectable photosensitive elements, wherein the N×

M array comprises a pinned photodiode structure formed in a region of photosensitive semiconductor material, and an n-type conductive region positioned between a charge carrier sink and the pinned photodiode structure, and wherein a volume between the n-type conductive region and the pinned photodiode structure is configured to prevent charge carriers from entering the photosensitive semiconductor material during an integration time.

30. The imager of claim 29, wherein the filter is attached to a substrate supporting the pixel matrix.

31. The imager of claim 29, wherein the region of photosensitive semiconductor material is configured to receive light passing through an antireflective material.

32. The imager of claim 31, wherein the antireflective material is configured as a layer attached to at least one of the filter, the substrate and the region of photosensitive material.

33. The imager of claim 29, wherein the filter is configured to pass light having an energy above a band gap energy of the region of photosensitive semiconductor material.

34. The imager of claim 29, wherein the filter is coupled to receive light from at least one lens.

35. The imager of claim 29, wherein the region of photosensitive semiconductor material is configured to generate carriers at a specified rate based on the predetermined wavelength.

36. The imager of claim 29, wherein the filter is a substrate layer supporting the pixel matrix.

37. The imager of claim 29, wherein the volume between the n-type conductive region and the photosensitive semiconductor material includes a portion configured to block charge carriers using a dopant atom profile.

38. The imager of claim 29, wherein a region between the n-type conductive region and the charge carrier sink form a barrier including in-band electronic states.

39. A method comprising:

blocking non-imaging electrons from reaching a photosensitive region;

collecting the non-imaging electrons; and

generating an image using a store of charge absent the non-imaging electrons.

40. The method of claim 39, wherein blocking non-imaging electrons includes selecting an energy potential based on a material used to store photogenerated electrons.

41. The method of claim 40, wherein selecting an energy potential includes selecting a dopant atom profile.

42. The method of claim 40, wherein selecting an energy potential includes selecting a potential barrier configuration using a dopant atom profile.

43. The method of claim 39, wherein blocking non-imaging electrons includes forming a barrier including in-band electronic states.

44. The method of claim 39, wherein blocking non-imaging electrons includes adjusting an energy potential profile using at least one voltage signal.

45. The method of claim 44, wherein adjusting an energy potential profile includes adjusting to transfer non-imaging electrons to a charge drain.

46. The method of claim 39, wherein collecting the non-imaging electrons includes collecting non-imaging electrons generated in a region located between a pinned photodiode structure and charge carrier sink.

47. The method of claim 39, wherein blocking non-imaging electrons includes blocking non-imaging electrons generated in a floating gate region.

48. A pixel sensor, comprising:

a plurality of light conversion regions;

a plurality of charge carrier blocking regions, the plurality of charge carrier blocking regions operatively coupled to the plurality of light conversion regions; and

a plurality of charge removal regions configured to trap charge carriers using the charge carrier blocking regions and to transfer the charge carriers to at least one potential well with an energy above a specified threshold potential.

49. The pixel sensor of claim 48, wherein at least one of the charge blocking regions and at least one of the charge removal regions are formed as a single region.

50. The pixel sensor of claim 48, wherein the plurality of charge blocking regions includes a first potential energy barrier greater than a second potential energy barrier formed using a dopant atom profile.

51. The pixel sensor of claim 48, wherein the plurality of charge removal regions includes a potential energy barrier with in-band electronic states configured to couple the charge carriers to a charge carrier sink.

52. The pixel sensor of claim 48, wherein at least one of the plurality of light conversion regions is configured to receive light passing through at least one of a shutter, a filter, and a lens.

53. The pixel sensor of claim 48, wherein at least one of the plurality of charge conversion regions is configured to receive light having a plurality of wavelength bands.

54. The pixel sensor of claim 48, wherein the plurality of light conversion regions are configured to store photogenerated charge carriers during a specified charge carrier accumulation time.

55. The pixel sensor of claim 48, wherein the plurality of charge blocking regions are configured to block charge carriers generated outside the plurality of light conversion regions.

56. The pixel sensor of claim 48, wherein the plurality of light conversion regions is configured to absorb light associated with heat.

57. A system comprising:

a processor coupled to a memory unit;

an imaging module coupled to the processor, the imaging module comprising an array of pixel sensors, the pixel sensors configured to receive light from an illuminated object and further configured to block charge carriers generated outside a photosensitive region from entering the photosensitive region using an adjustable potential barrier, the photosensitive region comprising a pinned photodiode structure; and

a light source to illuminate the object.

58. The system of claim 57, wherein the imaging module is configured to receive a digital radiographic image.

59. The system of claim 57, wherein the imaging module is configured to receive light transmitted from an automobile.

60. The system of claim 57, wherein the imaging module is configured to receive an image of at least a portion of a human body.

61. The system of claim 57, wherein the imaging module is configured to receive light passing through a chemical vapor.

62. The system of claim 57, wherein the imaging module is configured to receive non-absorbed light from an object.

63. The system of claim 57, wherein the processor is a processor associated with a hand-held communication system.

64. The system of claim 57, wherein the imaging module includes a memory configured to store images.