Photonic crystal-based filter for use in an image sensor

• US 20050263675A1
• Filed: 06/01/2004
• Published: 12/01/2005
• Est. Priority Date: 06/01/2004
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Micron Technology, Inc.
• Inventors: Mouli, Chandra
• Granted Patent: US 7,250,591 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:

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

at least one photonic crystal filter over at least one of the pixel cells 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, wherein the photonic crystal filter comprises a first plurality of portions having a photonic crystal structure configured to select green wavelengths of light, a second plurality of portions having a photonic crystal structure configured to select red wavelengths of light, and a third plurality of portions 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 3, further comprising a fourth plurality of portions having a photonic crystal structure configured to select infrared wavelengths of light.

6. The image sensor of claim 1, wherein the photonic crystal filter is a layer 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 photonic crystal filters over at least one of the pixel cells.

9. The image sensor of claim 8, wherein the first photonic crystal filter is provided over the second photonic crystal filter.

10. The image sensor of claim 9, 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 being 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.

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 filter over at least one of the pixel cells, the at least one filter having a photonic crystal structure.

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.

17. A processor system comprising:

(i) a processor; and

(ii) an image sensor coupled to the processor, the image sensor comprising;

a substrate,

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

at least one photonic crystal filter over at least one of the pixel cells configured to selectively permit electromagnetic wavelengths to reach at least one photo-conversion device.

18. The processor system of claim 17, wherein the image sensor is a CMOS image sensor.

19. The processor system of claim 17, wherein the image sensor is a charge coupled device image sensor.

20. A photonic crystal filter for an image sensor, the filter comprising:

a substrate;

a plurality of pillars forming a photonic crystal structure over the substrate, the pillars being spaced apart from each other; and

a material within the spacing between the pillars having a dielectric constant that is different than a dielectric constant of the pillars, the photonic crystal structure configured to be selective for particular wavelengths of electromagnetic radiation.

21. The photonic crystal filter of claim 20, wherein the dielectric constant of the material within the spacing is lower than the dielectric constant of the pillars.

22. The photonic crystal filter of claim 20, wherein the pillars have a height within the range of approximately 100 Å

to approximately 5000 Å

.

23. The photonic crystal filter of claim 20, wherein a ratio of the spacing between the pillars to a height of the pillars is within the range of approximately 1 to approximately 10.

24. The photonic crystal filter of claim 20, wherein the pillars each have a circular horizontal cross sectional shape.

25. The photonic crystal filter of claim 20, wherein the pillars each have a pentagonal horizontal cross sectional shape.

26. The photonic crystal filter of claim 20, wherein the pillars each have a rectangular horizontal cross sectional shape.

27. The photonic crystal filter of claim 20, wherein the pillars comprise aluminum oxide.

28. The photonic crystal filter of claim 20, wherein the pillars comprise tantalum oxide.

29. The photonic crystal filter of claim 20, wherein the pillars comprise zirconium oxide.

30. The photonic crystal filter of claim 20, wherein the pillars comprise hafnium oxide.

31. The photonic crystal filter of claim 20, wherein the pillars comprise a hafnium-based silicate.

32. The photonic crystal filter of claim 20, wherein the material within the spacing is spun on glass.

33. The photonic crystal filter of claim 20, wherein the material within the spacing is silicon dioxide.

34. A method of forming an image sensor, the method comprising:

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

forming at least one photonic crystal filter over at least one of the pixel cells, the photonic crystal filter configured to selectively permit electromagnetic wavelengths to reach at least one photo-conversion device.

35. The method of claim 34, wherein the act of forming the at least one photonic crystal filter comprises forming a first portion over a first photo-conversion device and a second portion over at least a second photo-conversion device, the first portion having a different photonic crystal structure than the 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.

36. The method of claim 35, wherein the act of forming the at least one photonic crystal filter comprises forming a plurality of first portions having a photonic crystal structure configured to select green wavelengths of light, a plurality of second portions having a photonic crystal structure configured to select red wavelengths of light, and a plurality of third portions having a photonic crystal structure configured to select blue wavelengths of light.

37. The method of claim 36, wherein the act of forming the at least one photonic crystal filter comprises arranging the first, second, and third portions in a Bayer pattern.

38. The method of claim 36, further comprising forming a plurality of fourth portions having a photonic crystal structure configured to select infrared wavelengths of light.

39. The method of claim 34, wherein the act of forming the photonic crystal filter comprises forming a layer having a uniform photonic crystal structure.

40. The method of claim 39, wherein the photonic crystal structure is configured to select infrared wavelengths of light.

41. The method of claim 34, further comprising forming a least two photonic crystal filters over at least one of the pixel cells.

42. The method of claim 34, wherein the act of forming the at least one photonic crystal filter comprises forming a plurality of pillars spaced apart from each other.

43. The method of claim 42, wherein the act of forming the at least one photonic crystal filter further comprises placing a material within the spacing between the pillars, the material having a dielectric constant that is different than a dielectric constant of the pillars.

44. The method of claim 43, wherein the material placed within the spacing has a lower dielectric constant than the dielectric constant of the pillars.

45. A method of forming an image sensor, the method comprising:

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

forming a dielectric layer over the pixel cells; and

forming at least one photonic crystal filter on the dielectric layer by;

forming a layer of photonic crystal material on the dielectric layer,

etching the photonic crystal material layer to form a plurality of pillars spaced apart from each other, each pillar formed having a height and a horizontal cross sectional shape,

depositing over and between the pillars a layer of a material having a dielectric constant different than a dielectric constant of the pillars, the pillar height, the pillar shape, and the material layer formed such that the filter selectively permits electromagnetic wavelengths to reach at least one photo-conversion device, and

planarizing the material layer and the pillars.

46. A method of forming a photonic crystal filter for an image sensor, the method comprising:

providing a substrate;

forming a layer of a photonic crystal material over the substrate;

patterning the photonic crystal material layer to form a plurality of pillars forming a photonic crystal structure, the photonic crystal structure formed to be selective for particular wavelengths of electromagnetic radiation, the pillars formed spaced apart from each other and each having a height and a horizontal cross sectional shape; and

placing a material having a lower dielectric constant than a dielectric constant of the pillars within the spacing between the pillars.

47. The method of claim 46, wherein the act of forming a layer of a photonic crystal material comprises forming the photonic crystal material layer having a thickness within a range of approximately 100 Å

to approximately 5000 Å

.

48. The method of claim 46, wherein the act of patterning the photonic crystal material layer comprises forming the pillars such that a ratio of the spacing between the pillars to the height of the pillars is within the range of approximately 1 to approximately 10.

49. The method of claim 46, wherein the act of patterning the photonic crystal material layer comprises forming each of the pillars with a circular horizontal cross sectional shape.

50. The method of claim 46, wherein the act of patterning the photonic crystal material layer comprises forming each of the pillars with a rectangular horizontal cross sectional shape.

51. The method of claim 46, wherein the act of patterning the photonic crystal material layer comprises forming each of the pillars with a pentagonal horizontal cross sectional shape.

52. The method of claim 46, wherein the act of forming the layer of a photonic crystal material comprises forming a layer of aluminum oxide.

53. The method of claim 46, wherein the act of forming the layer of a photonic crystal material comprises forming a layer of tantalum oxide.

54. The method of claim 46, wherein the act of forming the layer of a photonic crystal material comprises forming a layer of zirconium oxide.

55. The method of claim 46, wherein the act of forming the layer of a photonic crystal material comprises forming a layer of hafnium oxide.

56. The method of claim 46, wherein the act of forming the layer of a photonic crystal material comprises forming a layer of a hafnium-based silicate.

57. The method of claim 46, wherein the act of placing the material within the spacing comprises depositing spun on glass.

58. The method of claim 46, wherein the act of placing the material within the spacing comprises depositing silicon dioxide.