Methods of fabricating optoelectronic IC modules

• US 20030032209A1
• Filed: 08/13/2001
• Published: 02/13/2003
• Est. Priority Date: 08/13/2001
• Status: Active Grant

• Current Assignee: Kaiwood Technology Company Limited
• Original Assignee: Optics Technology, Inc.
• Inventors: Zhai, Jinhui, Yeh, Jang-Hun, Wen, Xueya
• Granted Patent: US 6,692,979 B2
• Time in Patent Office: Days
• US Class Current: 438/22
• CPC Class Codes: G02B 6/4204 the coupling comprising intermediate optical elements, e.g. lenses, holograms encapsulated active devices H01S5/02208, H01L33/52
• CPC Class Codes: G02B 6/4214 the intermediate optical element having redirecting reflective means, e.g. mirrors, prisms for deflecting the radiation from horizontal to down- or upward direction toward a device G02B6/4246 takes precedence
• CPC Class Codes: G02B 6/4249 comprising arrays of active devices and fibres
• CPC Class Codes: H01S 5/0216 using an intermediate compound, e.g. a glue or solder
• CPC Class Codes: H01S 5/0217 Removal of the substrate
• CPC Class Codes: H01S 5/141 using a wavelength selective device, e.g. a grating or etalon H01S5/146 takes precedence
• CPC Class Codes: H01S 5/18305 with emission through the substrate, i.e. bottom emission
• CPC Class Codes: H01S 5/18311 using selective oxidation
• CPC Class Codes: H01S 5/423 having a vertical cavity

Abstract

A optoelectronic module comprises one or more VCSELs electrically connected to an IC and optically connected to a fiber optic faceplate. The fiber optic faceplate, comprising a closely packed bundle of optical fibers, permits efficient capture of light from the VCSELs. Precise alignment of the faceplate with respect to the VCSELs is not needed since light not collected by one fiber is captured by another nearby optical fiber. One method of fabricating the module comprises forming substrate layers on both sides of the VCSELs such that features can be formed on the first substrate layer while the second temporary substrate layer provides structural support. The method further comprises forming apertures on the first substrate layer by etching. An etch stop buffer layer positioned between the first substrate layer and the VCSELs protects the VCSELs from being etched in the process. The second temporary substrate layer is removed after the fiber optic faceplate is mounted on the first substrate side. An alternate method of VCSEL fabrication comprises forming an aperture by patterning a dielectric layer above an active layer within the VCSEL. The aperture in the dielectric layer can be formed with a high degree of precisely using conventional patterning techniques. The dielectric layer is part of a current confinement element that concentrates current in an active region. A top DBR can also be formed of multiple layers of dielectric.

Claims

1. A method of forming an optoelectronic module, comprising:

forming a plurality of optoelectronic devices on a substrate;

removing at least a portion of the substrate; and

mounting a faceplate at the location of the removed substrate to form an optical path to said optoelectronic devices.

2. The method of claim 1, wherein said optoelectronic devices comprise Vertical Cavity Surface Emitting Lasers (VCSELs).

3. The method of claim 2, wherein said at least a portion of said substrate is removed by chemical mechanical polishing (CMP).

4. The method of claim 2, wherein after said removal of at least a portion of said substrate, said substrate has a thickness no more than about 150 microns.

5. The method of claim 2, further comprising etching openings through the substrate for light from said VCSELs to pass.

6. The method of claim 2, wherein said faceplate comprises a fiber optic faceplate.

7. The method of claim 2, wherein the faceplate is mounted to said substrate with adhesive that is substantially optically transmissive to light output by said VCSEL.

8. The method of claim 7, wherein said adhesive is thermally cured.

9. The method of claim 2, further comprising affixing a temporary substrate to the VCSELs prior to mounting said faceplate to stabilize said VCSELs after said at least a portion of said substrate is removed.

10. The method of claim 9, wherein interstices between said VCSELs are filled with a filler material and said temporary substrate is attached to said filler material.

11. The method of claim 10, wherein said filler material is selected from the group of materials consisting essentially of wax, glue, polymer, and combinations thereof.

12. The method of claim 10, further comprises removing said temporary substrate after mounting said faceplate.

13. The method of claim 2, further comprising optically coupling an optical element to said faceplate.

14. The method of claim 13, wherein said faceplate is optically coupled to a fiber optic bundle.

15. The method of claim 13, wherein said faceplate is optically coupled to a wedge-shaped fiber optic faceplate comprising a plurality of optical fibers aligned lengthwise parallel to each other, wherein said wedge-shaped fiber optic faceplate has a reflective surface oriented at an angle with respect to said lengthwise parallel optical fibers to couple light thereinto.

16. The method of claim 2, further comprising providing an etch stop layer between the plurality of VCSELs and said substrate.

17. The method of claim 16, wherein said etch stop layer has a thickness between approximately 0.1 to 2 micrometers (μ

m).

18. The method of claim 16, wherein said etch stop layer comprises AlGaAs.

19. The method of claim 16, wherein said etch stop layer is formed on an upper surface of the substrate by epitaxial growth using molecular beam epitaxy (MBE) or metal-organic chemical vapor deposition (MOCVD).

20. The method of claim 1, wherein said optoelectronic devices comprise optical detectors that convert optical signals into electrical signals.

21. The method of claim 20, wherein said at least a portion of said substrate is removed by chemical mechanical polishing (CMP).

22. The method of claim 20, wherein after said removal of at least a portion of said substrate, said substrate has a thickness no more than about 150 microns.

23. The method of claim 20, further comprising etching openings through the substrate to form optical paths for accessing said optical detectors.

24. The method of claim 20, wherein said faceplate comprises a fiber optic faceplate.

25. The method of claim 20, further comprising affixing a temporary substrate to the optical detectors prior to mounting said faceplate to stabilize said optical detectors after said at least a portion of said substrate is removed.

26. The method of claim 20, wherein interstices between said optoelectronic devices are filled with a filler material and a rigid material is attached to said filler material.

27. The method of claim 26, wherein said filler material is selected from the group of materials consisting essentially of wax, glue, polymer, and combinations thereof.

28. The method of claim 26, further comprises removing said temporary substrate after mounting said faceplate.

30. The method of claim 20, wherein said faceplate is optically coupled to a wedge-shaped fiber optic faceplate comprising a plurality of optical fibers aligned lengthwise parallel to each other, wherein said wedge-shaped fiber optic faceplate has having a reflective surface oriented at an angle with respect to lengthwise parallel optical fibers to couple light thereinto.

32. The method of claim 20, further comprising providing an etch stop layer between the plurality of optical detectors and said substrate.

33. The method of claim 1, further comprising mounting said plurality of optoelectronic devices on an integrated circuit (IC) chip, forming electrical connections between said optoelectronic devices and circuitry on said IC chip.

34. The method of claim 33, wherein said electrical connections are formed by a process selected from the group consisting of solder bonding, thermo-compression bonding, and application of conductive adhesive.

35. The method of claim 33, wherein said optoelectronic devices comprise Vertical Cavity Surface Emitting Lasers (VCSELs)

36. A method of forming an optoelectronic module, comprising:

forming a plurality of optoelectronic devices on a substrate;

removing at least a portion of the substrate;

mounting a substantially optically transmissive element at the location of the removed substrate to provide optical access to said optoelectronic devices; and

stabilizing the optoelectronic devices prior to mounting the optically transmissive element by affixing a temporary substrate to the optoelectronic devices.

37. The method of claim 36, wherein said optoelectronic devices comprise Vertical Cavity Surface Emitting Lasers (VCSELs).

38. The method of claim 37, wherein said VCSELs comprise a top DBR, a bottom DBR, and an active region therebetween, wherein the bottom DBR is formed on an upper surface of the substrate and is between about 97% to 99% reflective and said top DBR is formed to be about 100% reflective.

39. The method of claim 37, wherein a layer of the substrate is removed so that said substrate is less than about 150 μ

m thick.

40. The method of claim 37, wherein openings are etched through the thickness of the substrate for light from the VCSELs to pass.

41. The method of claim 40, wherein said optically transmissive element comprises a fiber optic faceplate which receives light from said etched openings.

42. The method of claim 37, wherein interstices between adjacent VCSELs are filled with a filler material and a temporary substrate is adhered to said filler material.

43. The method of claim 42, wherein said temporary substrate comprises glass.

44. The method of claim 43, wherein said filler material comprises wax and glue.

45. The method of claim 42, further comprising removing said temporary substrate after the optically transmissive element is mounted to the VCSELs.

46. The method of claim 37, wherein said optoelectronic devices comprise optical detectors.

47. The method of claim 46, wherein a layer of the substrate is removed so that said substrate is less than about 150 μ

m thick.

48. The method of claim 46, wherein openings are etched through thickness of the substrate for light to pass to said optical detectors.

49. The method of claim 48, wherein said optically transmissive element comprises a fiber faceplate that directs light into said etched openings.

50. The method of claim 46, wherein interstices between adjacent optical detectors are filled with a filler material and a temporary substrate is adhered to said filler material.

51. The method of claim 50, wherein said temporary substrate comprises glass.

52. The method of claim 50, wherein said filler material comprises wax and glue.

53. The method of claim 46, further comprising removing said temporary substrate after the optically transmissive element is mounted to the optical detectors.

54. A method of forming an optoelectronic module, comprising:

forming a Vertical Cavity Surface Emitting Laser (VCSEL) on at least one layer that is formed on a substrate;

removing said substrate;

mounting said at least one layer to an integrated circuit (IC) chip;

forming vias in said at least one layer to provide electrically conducting pathways from said VCSEL to said IC chip;

mounting a faceplate above said VCSEL to receive light from said VCSEL.

55. The method of claim 54, wherein said substrate comprises a semiconductor wafer.

56. The method of claim 55, wherein said at least one layer comprises an etch stop layer.

57. The method of claim 54, wherein said substrate is removed by chemical mechanical polishing (CMP).

58. The method of claim 54, wherein substantially all said substrate is removed.

59. The method of claim 54, wherein said faceplate comprises a fiberoptic faceplate.

60. The method of claim 59, wherein said fiber optic faceplate is optically coupled to a wedge-shaped fiber optic faceplate comprising a plurality of optical fibers aligned lengthwise parallel to each other, wherein said wedge-shaped fiber optic faceplate has a reflective surface oriented at an angle with respect to said lengthwise parallel optical fibers to couple light thereinto.

61. A method of forming an optoelectronic module, comprising:

forming a multiplicity of Vertical Cavity Surface Emitting Laser (VCSELs) on a wafer;

cutting the wafer into a plurality of pieces, each piece containing a plurality of VCSELs; and

mounting the pieces to respective IC chips and electrically connecting said VCSELs to said IC chips.

62. The method of claim 61, wherein prior to mounting said pieces to IC chips, said IC chips are cut from a wafer.

63. The method of claim 61, further comprising testing said VCSELs prior to mounting the pieces to said respective IC chips.

64. The method of claim 63, wherein said VCSELs are tested prior to cutting said VCSEL wafer into pieces.

65. The method of claim 63, wherein said VCSELs are tested after cutting said VCSEL wafer into pieces.

66. The method of claim 63, wherein optical output from said VCSELs is tested.

67. The method of claim 61, wherein said pieces are electrically connected to said respective IC chips by a process selected from the group consisting of solder bonding, thermo-compression bonding, and application of conductive adhesive.