Method and apparatus providing graded-index microlenses

• US 20070217020A1
• Filed: 05/02/2007
• Published: 09/20/2007
• Est. Priority Date: 08/11/2005
• Status: Active Grant

• Current Assignee: Apting Imaging Corporation
• Original Assignee: Apting Imaging Corporation
• Inventors: Li, Jiutao, Li, Jin
• Granted Patent: US 7,564,631 B2
• Time in Patent Office: Days
• US Class Current: 359/652
• CPC Class Codes: G02B 3/0012 characterised by the manufacturing method
• CPC Class Codes: G02B 3/0087 with index gradient
• CPC Class Codes: H01L 27/14625 Optical elements or arrangements associated with the device
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H01L 27/14685 Process for coatings or optical elements

Abstract

Microlenses are fabricated with a refractive-index gradient. The refractive-index gradient is produced in a microlens material such that the refractive index is relatively higher in the material nearest the substrate, and becomes progressively lower as the layer gets thicker. After formation of the layer with the refractive-index gradient, material is etched from the layer through a resist to form microlenses. The index of refraction can be adjusted in the microlens material by controlling oxygen and nitrogen content of the microlens materials during deposition. High-oxide material has a lower index of refraction. High-oxide material also exhibits a faster etch-rate. The etching forms the material into a lens shape. After removal of the resist, the microlenses have a lower relative refractive index at their apex, where the index of refraction preferably approaches that of the ambient surroundings. Consequently, light loss by reflection at the ambient/microlens interface is reduced.

Claims

1-7. -7. (canceled)

8. A solid-state imaging device comprising a photoelectric transducer and an associated lens, the lens having an apex and a base, the lens comprising a lens-material having a changing index of refraction.

9. A solid-state imaging device as in claim 8, wherein an oxygen content of the lens-material varies inversely with a nitrogen content of the lens material with respect to a thickness of the lens from the base to the apex of the lens.

10. A solid-state imaging device as in claim 9, wherein the oxygen content is highest toward an apex of the lens.

11. A solid-state imaging device as in claim 9, wherein the nitrogen content is highest toward a base of the lens.

12. A solid-state imaging device as in claim 9, wherein the oxygen content x is zero toward the base of the lens.

13. A solid-state imaging device as in claim 9, wherein the nitrogen content y is zero toward the apex of the lens.

14. A solid-state imaging device as in claim 8, wherein the lens material is arranged in discrete layers.

15. A solid-state imaging device as in claim 8, wherein the lens material is arranged in continuous layers.

16. A solid-state imaging device as in claim 8, wherein the lens is convex.

17. A lens structure comprising:

a substrate containing a photodevice; and

a microlens having a base and a thickness measured from the base, formed of oxygen and nitrogen-containing materials disposed over the substrate and in optical communication with the photodevice, a ratio of oxygen-content to nitride-content in the materials disposed on the substrate increasing with the thickness of the microlens.

18. A lens structure as in claim 17, wherein the microlens material is inorganic.

19. A lens structure comprising:

a substrate supporting a photodevice; and

a microlens having a base and having a thickness measured from the base, and formed of a microlens material disposed over the substrate and in optical alignment with the photodevice, an index of refraction of the microlens material decreasing with the thickness of the microlens.

20. A microlens array comprising a plurality of microlenses, each microlens comprising a microlens material disposed on the substrate to provide a thickness measured from the substrate, an index of refraction of the microlens material decreasing with the thickness of the microlens.

21. A microlens array as in claim 20, wherein the array if provided in an imaging device.

22. A microlens array as in claim 21, wherein the imaging device is part of a processing system.

23-31. -31. (canceled)