IMAGING MODULE WITH SYMMETRICAL LENS SYSTEM AND METHOD OF MANUFACTURE

• US 20090323206A1
• Filed: 06/25/2008
• Published: 12/31/2009
• Est. Priority Date: 06/25/2008
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Micron Technology, Inc.
• Inventors: Oliver, Steve, Duparre, Jacques, Viens, Jeff, Lake, Rick, Hegde, Shashikant
• Granted Patent: US 7,710,667 B2
• Time in Patent Office: Days
• US Class Current: 359/776
• CPC Class Codes: G02B 13/003 having two lenses
• CPC Class Codes: G02B 13/006 at least one element being a compound optical element, e.g. cemented elements
• CPC Class Codes: G02B 13/0085 employing wafer level optics
• CPC Class Codes: G02B 3/0012 characterised by the manufacturing method
• 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 27/14687 Wafer level processing
• CPC Class Codes: H01L 31/0232 Optical elements or arrangements associated with the device H01L31/0236 takes precedence; for photovoltaic cells H01L31/054; for photovoltaic modules H02S40/20
• CPC Class Codes: H04N 23/57 Mechanical or electrical details of cameras or camera modules specially adapted for being embedded in other devices

Abstract

An imaging module and method of fabrication. The method comprises forming a first lens wafer with a plurality of outer negative lenses and forming a second lens wafer with a plurality of inner negative lenses The method further comprises bonding the first lens wafer and second lens wafer to create a bonded stack; forming a plurality of inner positive lenses on the second lens wafer and bonding a spacer wafer to the second lens wafer; and forming a plurality of outer positive lenses on the first lens wafer.

Claims

1. An imaging module comprising:

a first transparent substrate having a first aperture layer on a first side and a second aperture layer on a second side, the first aperture layer comprising a first aperture and the second aperture layer comprising a second aperture such that the first aperture and the second aperture are optically aligned;

a first lens replication layer comprising a first positive lens on a first side of the first transparent substrate, the first aperture layer being between the first lens replication layer and the first side of the first transparent substrate and the first positive lens being optically aligned with the first aperture;

a second lens replication layer comprising a first negative lens on a second side of the first transparent substrate, the second aperture layer being between a first side of the second lens replication layer and the second side of the first transparent substrate and the first negative lens being optically aligned with the second aperture;

a second transparent substrate having a third aperture layer on a first side and a fourth aperture layer on a second side, the third aperture layer comprising a third aperture and the fourth aperture layer comprising a fourth aperture such that the third aperture and the fourth aperture are optically aligned;

a third lens replication layer comprising a second negative lens on a first side of the second transparent substrate, the third aperture layer being between a first side of the third lens replication layer and the first side of the second transparent substrate and the second negative lens being optically aligned with the third aperture;

a fourth lens replication layer comprising a second positive lens on a second side of the second transparent substrate, the fourth aperture layer being between the fourth lens replication layer and the second side of the second transparent substrate and the second positive lens being optically aligned with the fourth aperture; and

an image sensor comprising a pixel array optically aligned with said lenses and apertures,

wherein a second side of the second lens replication layer is attached to a second side of the third lens replication layer such that the first, second, third and fourth apertures are optically aligned.

2. The imaging module of claim 1, further comprising an encapsulating material on each side of the imaging module.

3. The imaging module of claim 1, further comprising a through-wafer interconnect substrate holding the image sensor.

4. The imaging module of claim 2, further comprising a spacer between the fourth lens replication layer and the through-wafer interconnect substrate layer.

5. The imaging module of claim 2, further comprising solder balls connected to the image sensor through the through-wafer interconnect substrate layer.

6. The imaging module of claim 1, wherein the lens replication layers comprise an ultraviolet-curable hybrid polymer.

7. The imaging module of claim 1, wherein the aperture layers comprise a light-absorbing material.

8. The imaging module of claim 1, further comprising a lens hood affixed to an image receiving side of the imaging module.

9. The imaging module of claim 1, wherein the first and second transparent substrates comprise a boro-float glass.

10. The imaging module of claim 9, wherein the boro-float glass has a coefficient of thermal expansion between 2 and 5.

11. The imaging module of claim 1, further comprising an infrared cut filter.

12. The imaging module of claim 1, wherein the second aperture is an system stop and the first, third and fourth apertures are field stops.

13. The imaging module of claim 1, wherein at least one of the first positive lens, first negative lens, second negative lens and second positive lens have 6th order aspheric coefficients.

14. The imaging module of claim 1, wherein at least one of the first positive lens, first negative lens, second negative lens and second positive lens has an Abbe number greater than 50.

15. The imaging module of claim 1, wherein at least one of the first positive lens and second positive lens have an Abbe number greater than 50 and the first negative lens and second negative lens have an Abbe number less than 50.

16. A method of fabricating an imaging module comprising:

forming a first lens wafer with a plurality of outer negative lenses;

forming a second lens wafer with a plurality of inner negative lenses;

bonding the first lens wafer and second lens wafer to create a bonded stack;

forming a plurality of inner positive lenses on the second lens wafer;

bonding a spacer wafer to the second lens wafer;

forming a plurality of outer positive lenses on the first lens wafer; and

affixing a through-wafer interconnect substrate wafer to the bonded stack, the through-wafer interconnect substrate wafer comprising an image sensor.

17. The method of claim 16, wherein the step of forming a first lens wafer with a plurality of outer negative lenses further comprises:

forming an infrared cut filter on a first surface of the first lens wafer;

forming a light absorbing material on the first surface and a second surface opposite the first surface of the first lens wafer;

removing the light absorbing material from a plurality of first areas on the first surface of the first lens wafer to form first apertures;

removing the light absorbing material from a plurality of second areas on the second surface of the first lens wafer to form second apertures, each second aperture being optically aligned with a respective first aperture;

forming a lens replication material on the second surface of the first lens wafer; and

forming the plurality of outer negative lenses in the lens replication material, each outer negative lens being optically aligned with a second aperture.

18. The method of claim 17, wherein the light absorbing material is a black matrix polymer.

19. The method of claim 17, wherein the lens replication material comprises an ultraviolet-curable hybrid polymer.

20. The method of claim 19, further comprising curing the lens replication material while the outer negative lenses are formed.

21. The method of claim 17, further comprising:

bonding a temporary carrier to the first lens wafer before forming the lens replication material; and

debonding and removing the temporary carrier after said lenses are formed.

22. The method of claim 16, wherein the step of forming a second lens wafer with a plurality of inner negative lenses further comprises:

forming a light absorbing material on first and second surfaces of the second lens wafer;

removing the light absorbing material from a plurality of first areas on the first surface of the second lens wafer to form first apertures;

removing the light absorbing material from a plurality of second areas on the second surface of the second lens wafer to form second apertures wherein each second aperture is optically aligned with a respective first aperture;

forming a lens replication material on the second surface of the second lens wafer; and

forming the plurality of inner negative lenses in the lens replication material, each inner negative lens being optically aligned with a second aperture.

23. The method of claim 22, wherein the light absorbing material is selected from the group consisting of PSK™

2000, JSR 812, black chromium, and dark silicon.

24. The method of claim 22, wherein the lens replication material comprises an ultraviolet-curable hybrid polymer.

25. The method of claim 24, further comprising curing the lens replication material while the inner negative lenses are formed.

26. The method of claim 16, wherein the step of bonding the first and second lens wafers further comprises:

forming an adhesive material on the second surface of either the first lens wafer or second lens wafer; and

attaching the second surfaces of the first and second lens wafers such that the plurality of outer and inner lenses of the first and second lens wafers are optically aligned.

27. The method of claim 16, wherein the step of forming a plurality of inner positive lenses on the second lens wafer further comprises:

forming a lens replication material on a first surface of the second lens wafer; and

forming the plurality of inner positive lenses in the lens replication material, each inner positive lens being optically aligned with an inner negative lens.

28. The method of claim 27, wherein the lens replication material comprises an ultraviolet-curable hybrid polymer.

29. The method of claim 28, further comprising curing the lens replication material while the inner positive lenses are formed.

30. The method of claim 27, wherein at least one of the plurality of inner negative lenses is formed in the lens replication material such that the entire lens is formed deeper in the lens replication material than a top surface of the lens replication material, such top surface facing away from the second lens wafer.

31. The method of claim 27, further comprising forming spacers into the lens replication material.

32. The method of claim 16, wherein the step of bonding a spacer wafer to the second lens wafer further comprises:

forming an adhesive material on a first side of a spacer wafer; and

affixing the first side of the spacer wafer to the first side of the second lens wafer.

33. The method of claim 16, wherein the step of forming a plurality of outer positive lenses on the first lens wafer further comprises:

forming a lens replication material on the first surface of the first lens wafer; and

forming the plurality of outer positive lenses in the lens replication material, each outer positive lens being optically aligned with an outer negative lens.

34. The method of claim 16, wherein the step of affixing a through-wafer interconnect substrate wafer to the bonded stack further comprises:

dicing the bonded stack connected to the through-wafer interconnect to create a plurality of lens stacks;

placing at least one lens stack on a through-wafer interconnect substrate wafer having a pixel array for each of the at least one lens stacks, such that the spacer wafer is over and touching the through-wafer interconnect substrate wafer;

encapsulating each lens stack; and

dicing the lens stacks to create a plurality of imaging modules.

35. The method of claim 16, wherein the step of affixing a through-wafer interconnect substrate wafer to the bonded stack further comprises:

placing the bonded stack on a through-wafer interconnect substrate wafer having an image sensor for each inner positive lens, such that the spacer wafer is over and touching the through-wafer interconnect substrate wafer;

dicing the bonded stack connected to the through-wafer interconnect to create a plurality of imaging modules; and

encapsulating each imaging module.

36. The method of claim 34, further comprising

forming solder bumps that connect to the image sensor through the through-wafer interconnect substrate wafer.

37. A method of fabricating an imaging module comprising:

forming a first lens wafer with a plurality of inner negative lenses and a plurality of inner positive lenses;

bonding the first lens wafer to a first spacer wafer to form a first stack;

forming a second lens wafer with a plurality of outer negative lenses and a plurality of outer positive lenses;

aligning and fastening the second lens wafer to a second spacer wafer;

aligning the plurality of outer and inner lenses in the first and second stacks;

bonding the first stack to the second stack to create a bonded stack; and

affixing a through-wafer interconnect substrate wafer to the bonded stack, the through-wafer interconnect substrate wafer comprising an image sensor.

38. The method of claim 37, wherein the step of forming a first lens wafer with a plurality of inner negative lenses and a plurality of inner positive lenses further comprises:

forming a light absorbing material on first and second surfaces of the first lens wafer;

removing the light absorbing material from a plurality of first areas on the first surface of the first lens wafer to form first apertures;

removing the light absorbing material from a plurality of second areas on the second surface of the first lens wafer to form second apertures, each second aperture being optically aligned with a respective first aperture;

forming a lens replication material on the second surface of the first lens wafer;

forming the plurality of inner negative lenses in the lens replication material, each inner negative lens being optically aligned with a second aperture;

forming a lens replication material on the first surface of the first lens wafer; and

forming the plurality of inner positive lenses, each inner positive lens being optically aligned with a first aperture.

39. The method of claim 38, wherein the light absorbing material is a black matrix polymer selected from the group consisting of PSK™

2000, JSR 812, black chromium, and dark silicon.

40. The method of claim 38, wherein the steps forming the plurality of inner negative lenses and forming the plurality of inner positive lenses occur simultaneously.

41. The method of claim 37, wherein the step of bonding the first lens wafer to a first spacer wafer to form a first stack further comprises:

applying an adhesive material to a first side of the first spacer wafer; and

affixing the first side of the first spacer wafer to first side of the first lens wafer, wherein a plurality of holes in the first spacer wafer is optically aligned with the plurality of positive lenses on the first lens wafer.

42. The method of claim 37, wherein the step of forming a second lens wafer with a plurality of outer negative lenses and a plurality of outer positive lenses further comprises:

forming an infrared cut filter on a first surface of the second lens wafer;

forming a light absorbing material on the first surface and a second surface of the second lens wafer;

removing the light absorbing material from a plurality of first areas on the first surface of the second lens wafer to form first apertures;

removing the light absorbing material from a plurality of second areas on the second surface of the second lens wafer to form second apertures, wherein each second aperture is optically aligned with a respective first aperture;

forming a lens replication material on the second surface of the second lens wafer;

forming the plurality of outer negative lenses, each outer negative lens being optically aligned with a second aperture;

forming a lens replication material on the first surface of the second lens wafer; and

forming the plurality of outer positive lenses in the lens replication material, each outer positive lens being optically aligned with a first aperture.

43. The method of claim 42, wherein the steps forming the plurality of outer negative lenses and forming the plurality of outer positive lenses occur simultaneously.

44. The method of claim 37, wherein the second lens wafer and second spacer wafer are fastened together by a temporary adhesive material.

45. The method of claim 37, wherein the first stack and the second stack are bonded together using an adhesive material.

46. The method of claim 37, wherein the step of affixing a through-wafer interconnect substrate wafer to the bonded stack further comprises:

dicing the bonded stack to create a plurality of lens stacks;

placing at least one lens stack on a through-wafer interconnect substrate wafer having a pixel array for each of the at least one lens stacks, such that the spacer wafer is over and touching the through-wafer interconnect substrate wafer;

encapsulating each lens stack; and

dicing the lens stacks through the through-wafer interconnect substrate wafer to create a plurality of imaging modules.

47. The method of claim 37, wherein the step of affixing a through-wafer interconnect substrate wafer to the bonded stack further comprises:

placing the bonded stack on a through-wafer interconnect substrate wafer having a having an image sensor for each inner positive lens, such that the spacer wafer is over and touching the through-wafer interconnect substrate wafer;

dicing the bonded stack through the through-wafer interconnect substrate wafer to create a plurality of imaging modules; and

encapsulating each imaging module.

48. The method of claim 46, further comprising

forming solder bumps that connect to the image sensor through the through-wafer interconnect substrate wafer.

49. The method of claim 37, wherein the second spacer is removed.

50. An imaging module comprising:

a first substrate supporting a first lens assembly;

a second substrate supporting a second lens assembly;

a spacer substrate; and

a through-wafer interconnect substrate supporting an image sensor with a pixel array arranged to receive an image through said first and second lens assemblies.