Photonic crystal-based filter for use in an image sensor

• US 20070170349A1
• Filed: 03/26/2007
• Published: 07/26/2007
• Est. Priority Date: 06/01/2004
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Inventors: Mouli, Chandra
• Granted Patent: US 7,683,311 B2
• Time in Patent Office: Days
• US Class Current: 250/208.100
• CPC Class Codes: G02B 5/20 Filters polarising elements G02B5/30
• CPC Class Codes: H01L 27/14621 Colour filter arrangements
• CPC Class Codes: H01L 27/14625 Optical elements or arrangements associated with the device
• CPC Class Codes: H01L 27/14685 Process for coatings or optical elements
• CPC Class Codes: H01L 31/02165 using interference filters, e.g. multilayer dielectric filters interference filters G02B5/28

Abstract

The invention, in various exemplary embodiments, incorporates a photonic crystal filter into an image sensor. The photonic crystal filter comprises a substrate and a plurality of pillars forming a photonic crystal structure over the substrate. The pillars are spaced apart from each other. Each pillar has a height and a horizontal cross sectional shape. A material with a different dielectric constant than the pillars is provided within the spacing between the pillars. The photonic crystal filter is configured to selectively permit particular wavelengths of electromagnetic radiation to pass through.

Claims

1. An image sensor comprising:

a pixel cell comprising a photo-conversion device; and

at least one substantially flat photonic crystal filter over at least said pixel cell and configured to selectively permit electromagnetic wavelengths to reach the photo-conversion device.

2. The image sensor of claim 1, wherein the at least one photonic crystal filter comprises a first portion over a first photo-conversion device and at least a second portion over at least a second photo-conversion device, the first portion having a different photonic crystal structure than the at least second portion such that the first portion selectively permits a first group of electromagnetic wavelengths to reach the first photo-conversion device and the second portion selectively permits a second different group of electromagnetic wavelengths to reach the at least second photo-conversion device.

3. The image sensor of claim 1, further comprising an array of pixel cells comprising respective photoconversion devices and wherein the photonic crystal filter comprises a first plurality of portions over respective photoconversion devices and having a photonic crystal structure configured to select green wavelengths of light, a second plurality of portions over respective photoconversion devices and having a photonic crystal structure configured to select red wavelengths of light, and a third plurality of portions over respective photoconversion devices and having a photonic crystal structure configured to select blue wavelengths of light.

4. The image sensor of claim 3, wherein the first, second, and third portions are arranged in a Bayer pattern.

5. The image sensor of claim 1, further comprising an array of pixel cells comprising respective photoconversion devices and wherein the photonic crystal filter comprises a first comprising a fourth plurality of portions over respective photoconversion devices and having a photonic crystal structure configured to select infrared wavelengths of light.

6. The image sensor of claim 1, further comprising an array of pixel cells comprising respective photoconversion devices and wherein the photonic crystal filter is a part of a layer over said array having a uniform photonic crystal structure.

7. The image sensor of claim 6, wherein the photonic crystal structure is configured to select infrared wavelengths of light.

8. The image sensor of claim 1, further comprising a least two substantially flat photonic crystal filters arranged one above the other over the pixel cell.

10. The image sensor of claim 8, further comprising a dielectric layer between the first and second photonic crystal filters.

11. The image sensor of claim 1, wherein the photonic crystal filter comprises a plurality of pillars spaced apart from each other.

12. The image sensor of claim 11, wherein the photonic crystal filter further comprises a material within the spacing between the pillars, the material having a dielectric constant that is lower than a dielectric constant of the pillars.

13. The image sensor of claim 11, wherein the pillars comprise aluminum oxide.

9. (canceled)

14. An image sensor comprising:

an array of pixel cells at a surface of a substrate, each pixel cell comprising a photo-conversion device; and

at least one substantially flat photonic crystal filter over at least one of the array of pixel cells, said photonic crystal filter having portions over respective pixel cell for filtering different colors.

15. The image sensor of claim 14, wherein the photonic crystal filter comprises a plurality of pillars spaced apart from each other, a material within the spacing between the pillars has a dielectric constant that is different than a dielectric constant of the pillars.

16. The image sensor of claim 15, wherein the dielectric constant of the material within the spacing is lower than the dielectric constant of the pillars.

74. The image sensor of claim 14, wherein said image sensor being part of an image processing system.

75. The image sensor of claim 14, wherein said image sensor being part of a camera system.

17-58. -58. (canceled)

59. An image sensor comprising:

an array of pixel cells, each pixel cell comprising;

a photo-conversion device;

a micro-lens; and

a substantially flat color filter comprising;

a photonic crystal structure over the photo-conversion device and beneath the micro-lens, the photonic crystal structure being configured to permit light of predetermined wavelengths to reach the photo-conversion device.

60. The image sensor of claim 59, wherein the photonic crystal structure over a first photo-conversion device and the photonic crystal structure over a second photo-conversion respectively pass light of different wavelengths to the first and second photo-conversion devices.

61. The image sensor of claim 59, wherein photonic crystal structure over a first photo-conversion device is configured to pass green wavelengths of light, a photonic crystal structure over a second photo-conversion device is configured to pass red wavelengths of light, and a photonic crystal structure over a third photo-conversion device is configured to pass blue wavelengths of light.

62. The image sensor of claim 61, wherein the first, second, and third photo-conversion devices and photonic crystal structures are arranged in a Bayer pattern.

63. The image sensor of claim 59, wherein a photonic crystal structure over a respective photo-conversion device is configured to pass infrared wavelengths of light.

64. The image sensor of claim 59, wherein the photonic crystal structure over respective photo-conversion devices are part of a photonic crystal structure layer provided over said array.

65. The image sensor of claim 59, wherein the photonic crystal structure includes a plurality of photonic crystal structure layers arranged one over another.

66. The image sensor of claim 59, wherein the photonic crystal structure includes a single photonic crystal structure layer.

67. The image sensor of claim 65, further comprising a dielectric layer between the photonic crystal structure layers.

68. The image sensor of claim 59, wherein the photonic crystal structure comprises a plurality of pillars spaced apart from each other.

69. The image sensor of claim 68, wherein the photonic crystal structure further comprises a material within the spacing between the pillars, the material having a dielectric constant that is lower than a dielectric constant of the pillars.

70. The image sensor of claim 68, wherein the pillars comprise aluminum oxide.

76. The image sensor of claim 59, wherein said image sensor being part of an image processing system.

77. The image sensor of claim 59, wherein said image sensor being part of a camera system.

71. An image sensor comprising:

an array of photo-conversion devices;

an array of micro lenses respectively associated with the photo conversion devices; and

an array of color filters respectively over the photo-conversion devices and beneath the micro-lens, each color filter comprising a photonic crystal structure for passing light of a predetermined wavelength to an associated photo conversion device, where said array of color filters is substantially flat.

72. The image sensor of claim 71, wherein each photonic crystal structure comprises a plurality of pillars spaced apart from each other and wherein each photonic crystal structure further comprises a material within the spacing between the pillars which has a dielectric constant that is different than a dielectric constant of the pillars.

73. The image sensor of claim 72, wherein the dielectric constant of the material within the spacing is lower than the dielectric constant of the pillars.

78. The image sensor of claim 71, wherein said image sensor being part of an image processing system.

79. The image sensor of claim 71, wherein said image sensor being part of a camera system.