Planar and wafer level packaging of semiconductor lasers and photo detectors for transmitter optical sub-assemblies

• US 20040086011A1
• Filed: 10/30/2002
• Published: 05/06/2004
• Est. Priority Date: 10/30/2002
• Status: Active Grant

• Current Assignee: Kelton Capital LLC (Intellectual Ventures LLC)
• Original Assignee: Photodigm Incorporated
• Inventors: Bhandarkar, Sarvotham M.
• Granted Patent: US 6,970,491 B2
• Time in Patent Office: Days
• US Class Current: 372/43
• CPC Class Codes: G02B 6/4206 Optical features G02B6/4207, G02B6/421 take precedence
• CPC Class Codes: G02B 6/421 the intermediate optical component consisting of a short length of fibre, e.g. fibre stub
• 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: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73253 Bump and layer connectors
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/15192 Resurf arrangement of the internal vias
• CPC Class Codes: H01L 2924/16152 Cap comprising a cavity for hosting the device, e.g. U-shaped cap
• CPC Class Codes: H01L 2924/1815 Shape
• CPC Class Codes: H01S 5/02251 using optical fibres
• CPC Class Codes: H01S 5/02253 using lenses
• CPC Class Codes: H01S 5/02257 using windows, e.g. specially adapted for back-reflecting light to a detector inside the housing
• CPC Class Codes: H01S 5/02326 Arrangements for relative positioning of laser diodes and optical components, e.g. grooves in the mount to fix optical fibres or lenses
• CPC Class Codes: H01S 5/0237 by soldering
• CPC Class Codes: H01S 5/0683 by monitoring the optical output parameters
• CPC Class Codes: H01S 5/187 using Bragg reflection
• CPC Class Codes: H01S 5/42 Arrays of surface emitting lasers

Abstract

A planar wafer-level packaging method is provided for a laser and a monitor photo detector. The laser and photo detector are affixed to a planar substrate. The planar substrate provides electrical connections to the components. A lens cap with a microlens is formed and affixed to the substrate with a seal. The lens cap forms a hermetically sealed cavity enclosing the laser and photo detector. The inside surface of the lens cap has a reflective coating with a central opening over the emitting aperture of the laser. The central opening has an anti-reflective coating. Light from the laser is directed and shaped by the lens cap to couple into an external light guide. Residual light from the edge of the laser reflects off the inside surface of the lens cap and is incident upon the photo detector. In an alternate method, the laser may be packaged using flip-chip assembly.

Claims

1. A method for packaging a surface emitting laser, the method comprising:

attaching a laser to a first substrate, wherein the laser emits a laser beam from a surface of the laser;

attaching a photo detector to the first substrate, wherein the photo detector receives light from the laser; and

attaching a second substrate to the first substrate, wherein the first substrate and the 10 second substrate enclose the laser and the photo detector in a cavity,

wherein one of the first substrate and the second substrate includes at least one lens element, and

wherein the at least one lens element is constructed and positioned with respect to the laser to shape and direct the laser beam into a light guide.

2. The method of claim 1, wherein the step of attaching the photo detector to the substrate includes aligning the photo detector so that the photo detector receives light from an edge of the laser.

3. The method of claim 2, wherein the step of aligning the photo detector includes aligning the photo detector so that the photo detector receives light directly from the edge of the laser.

4. The method of claim 2, wherein the step of aligning the photo detector includes aligning the photo detector so that the photo detector receives light from the edge of the laser via reflection from an inside surface of the second substrate.

5. The method of claim 1, wherein the photo detector is integrated into the laser.

6. The method of claim 1, wherein the step of attaching the second substrate to the first substrate includes affixing the second substrate to the first substrate with a hermetic seal.

7. The method of claim 1, wherein the first substrate provides electrical connections from a portion of the first substrate inside the cavity to a portion of the first substrate outside the cavity.

8. A method for packaging a surface emitting laser, the method comprising:

attaching a laser to a first substrate, wherein the laser emits a laser beam from a first edge of the laser;

attaching a photo detector to the first substrate, wherein the photo detector receives light from the laser;

attaching an interposer to the first substrate; and

attaching a second substrate to the interposer, wherein the first substrate, the interposer, and the second substrate enclose the laser and the photo detector in a cavity,

wherein one of the first substrate and the second substrate includes at least one lens element, and

wherein the at least one lens element is constructed and positioned with respect to the laser to receive the laser beam from the first edge of the laser via reflection from an inside surface of the interposer and to shape and direct the laser beam into a light guide.

9. The method of claim 8, wherein the step of attaching the photo detector to the first substrate includes aligning the photo detector so that the photo detector receives light from a second edge of the laser.

10. The method of claim 9, wherein the step of aligning the photo detector includes aligning the photo detector so that the photo detector receives light directly from the second edge of the laser.

11. The method of claim 9, wherein the step of aligning the photo detector includes aligning the photo detector so that the photo detector receives light from the second edge of the laser via reflection from an inside surface of the interposer.

12. The method of claim 8, wherein the photo detector is integrated into the laser.

13. The method of claim 8, wherein the first substrate provides electrical connections from a portion of the first substrate inside the cavity to a portion of the first substrate outside the cavity.

14. A laser assembly, comprising:

a first substrate;

a second substrate; and

a laser attached to the second substrate, wherein the laser emits a laser beam,

wherein one of the first substrate and the second substrate has formed therein a lens element,

wherein the first substrate and the second substrate form a sealed cavity enclosing the laser, and

wherein the lens element directs and shapes the laser beam into a light guide.

15. The laser assembly of claim 14, wherein laser emits the laser beam through an aperture on a surface of the laser.

16. The laser assembly of claim 15, wherein the first substrate has formed therein the lens element on a top surface.

17. The laser assembly of claim 16, further comprising a photo detector attached to the second substrate, wherein the photo detector receives light from the laser.

18. The laser assembly of claim 17, wherein the photo detector is enclosed within the cavity.

19. The laser assembly of claim 17, wherein the first substrate has a reflective coating on a bottom surface.

20. The laser assembly of claim 19, wherein the photo detector receives light from an edge of the laser via reflection from the reflective coating.

21. The laser assembly of claim 19, wherein the reflective coating has an anti-reflective opening over the aperture.

22. The laser assembly of claim 17, wherein the first substrate has a partially reflective coating over the aperture and wherein the photo detector receives light from the surface of the laser via partial reflection of the laser beam.

23. The laser assembly of claim 17, wherein the photo detector receives light directly from an edge of the laser.

24. The laser assembly of claim 16, wherein the lens element is positioned above the aperture.

25. The laser assembly of claim 15, wherein the second substrate has formed therein the lens element on a top surface.

26. The laser assembly of claim 25, wherein the laser is attached to the second substrate on a bottom surface.

27. The laser assembly of claim 26, wherein a heatsink attach material is applied between the laser and the first substrate.

28. The laser assembly of claim 26, wherein the laser is attached using flip-chip.

29. The laser assembly of claim 26, further comprising a photo detector attached to the second substrate, wherein the photo detector receives light from the laser.

30. The laser assembly of claim 29, wherein the photo detector is enclosed within the cavity.

31. The laser assembly of claim 29, wherein the first substrate has a reflective coating on a top surface.

32. The laser assembly of claim 31, wherein the photo detector receives light from an edge of the laser via reflection from the reflective coating.

33. The laser assembly of claim 29, wherein the photo detector receives light directly from an edge of the laser.

34. The laser assembly of claim 14, wherein laser emits the laser beam through an edge of the laser.

35. The laser assembly of claim 34, wherein the first substrate has formed therein the lens element and wherein the lens element is positioned with respect to the laser to receive the laser beam from the edge of the laser via reflection from an inside surface of the first substrate and to shape and direct the laser beam into a light guide.

36. The laser assembly of claim 34, wherein the first substrate includes an interposer and wherein the interposer is attached to the second substrate to form the sealed cavity.

37. The laser assembly of claim 36, wherein the first substrate has formed therein the lens element and wherein the lens element is positioned with respect to the laser to receive the laser beam from the edge of the laser via reflection from an inside surface of the interposer and to shape and direct the laser beam into a light guide.

38. The laser assembly of claim 34, wherein the second substrate has formed therein the lens element and wherein the lens element is positioned with respect to the laser to receive the laser beam from the edge of the laser via reflection from an inside surface of the first substrate and to shape and direct the laser beam into a light guide.

39. The laser assembly of claim 14, wherein the second substrate provides electrical connections from a portion of the second substrate inside the sealed cavity to a portion of the second substrate outside the sealed cavity.

40. A laser assembly, comprising:

a substrate;

a laser attached to the substrate, wherein the laser emits at least one laser beam from a surface of the laser;

a photo detector attached to the substrate, wherein the photo detector receives light from an edge of the laser; and

a lens cap attached to the substrate, wherein the lens cap includes at least one lens element and wherein the substrate and the lens cap form a sealed cavity enclosing the laser and the photo detector,

wherein substrate provides electrical connections from a portion of the substrate inside the sealed cavity to a portion of the substrate outside the sealed cavity, and

wherein the at least one lens element is constructed and positioned with respect to the laser to shape and direct the at least one laser beam into at least one light guide.

41. A laser assembly, comprising:

a substrate;

a laser attached to a bottom surface of the substrate, wherein the laser emits at least one laser beam from a surface of the laser;

a photo detector attached to the bottom surface of the substrate, wherein the photo detector receives light from an edge of the laser; and

a cap attached to the substrate, wherein the substrate and the cap form a sealed cavity enclosing the laser and the photo detector,

wherein the substrate includes at least one lens element on a top surface of the substrate,

wherein substrate provides electrical connections from a portion of the substrate inside the sealed cavity to a portion of the substrate outside the sealed cavity, and

wherein the at least one lens element is constructed and positioned with respect to the laser to shape and direct the at least one laser beam into at least one light guide.