Optoelectronic device packaging with hermetically sealed cavity and integrated optical element

• US 6,998,691 B2
• Filed: 09/19/2003
• Issued: 02/14/2006
• Est. Priority Date: 09/19/2003
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Baugh, Brenton A., Snyder, Tanya J., Gallup, Kendra
• Primary Examiner(s): CLARK, SHEILA V
• Application Number:
  US10/666,091
• Publication Number:
  US 20050062056A1
• Time in Patent Office: 879 Days
• Field of Search: 257/431, 257/432, 257/433, 257/704, 257/81, 257/98, 372/43, 372/29, 372/33, 438/65, 438/69, 438/7, 438/16, 438/27, 438/29, 438/72
• US Class Current: 257/433
• 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 6/4248 Feed-through connections for the hermetical passage of fibres through a package wall see provisionally also G02B6/4428
• CPC Class Codes: G02B 6/4292 the light guide being disconnectable from the opto-electronic element, e.g. mutually self aligning arrangements
• CPC Class Codes: H01L 2224/05568 the whole external layer protruding from the surface
• CPC Class Codes: H01L 2224/05573 Single external layer
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/16 of an individual bump connector
• CPC Class Codes: H01L 2224/48091 Arched
• 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: H01S 5/0201 Separation of the wafer into individual elements, e.g. by dicing, cleaving, etching or directly during growth
• CPC Class Codes: H01S 5/02251 using optical fibres
• CPC Class Codes: H01S 5/02253 using lenses
• CPC Class Codes: H01S 5/02255 using beam deflecting elements
• CPC Class Codes: H01S 5/0237 by soldering
• CPC Class Codes: H01S 5/0683 by monitoring the optical output parameters
• CPC Class Codes: H01S 5/183 having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]

Abstract

A package for an optoelectronic device includes a hermetically sealed cavity into which a mirror or other optical element is integrated. For a side-emitting laser, an integrated mirror turns the light emitted from the laser inside the cavity so that the light exits through a top surface of the package. The packaging can be implemented for individual lasers or at the wafer level. A wafer level process fabricates sub-mounts in a first wafer, fabricates depressions with reflective areas in a second wafer, electrically connects optoelectronic devices to respective sub-mounts on the first wafer, and bonds a second wafer to the first wafer with the lasers hermetically sealed in cavities corresponding to the depressions in the second wafer. The reflective areas in the depressions act as turning mirrors for side emitting lasers.

Claims

1. A structure comprising:

an optoelectronic device;

a sub-mount containing electrical traces that are electrically connected to the optoelectronic device; and

a cap attached to the sub-mount so as to form a cavity enclosing the optoelectronic device, wherein the cap includes an optical element positioned to reflect an optical signal between a path extending to the optoelectronic device and a path extending out of the structure.

2. The structure of claim 1, wherein the optoelectronic device comprises a side-emitting laser that emits the optical signal.

3. The structure of claim 2, wherein the optical element comprises a reflector positioned to reflect the optical signal from an initial direction to an output path that is substantially perpendicular to the initial direction.

4. The structure of claim 3, wherein the output path is through the sub-mount.

5. The structure of claim 3, wherein the reflector comprises a portion of a wall of the cavity.

6. The structure of claim 1, wherein the sub-mount further comprises:

internal bonding pads that are within the cavity and connected to the optoelectronic device; and

external bonding pads that electrically connect to the internal bonding pads and are accessible outside the cavity.

7. The structure of claim 1, wherein the sub-mount further comprises active circuitry useful in operation of the optoelectronic device.

8. The structure of claim 1, wherein a bond of the cap to the sub-mount hermetically seals the cavity.

9. The structure of claim 8, wherein the optical element comprises a reflector on a portion of the walls of the cavity.

10. The structure of claim 1, wherein the cap comprises a silicon substrate including a depression that forms walls of the cavity.

11. The structure of claim 10, wherein the optical element comprises a portion of the walls that is along a <

111>

plane of the crystal structure of the silicon substrate.

12. A process comprising:

electrically connecting an optoelectronic device to a sub-mount;

fabricating a cap that includes an optical element; and

bonding the cap to the sub-mount, wherein the optoelectronic device is enclosed in a cavity between the sub-mount and the cap and an optical signal of the optoelectronic device is incident on the optical element and there reflected between a path extending to the optoelectronic device and a path extending out of the cavity.

13. The process of claim 12, wherein fabricating the cap comprises:

creating a depression in a substrate, the depression having walls that correspond to walls of the cavity; and

forming the optical element as a reflector corresponding to a reflective area on the walls of the depression.

14. The process of claim 13, wherein creating the depression comprises etching the substrate.

15. The process of claim 14, wherein the substrate comprises silicon, and the reflective area coincides with a <

111>

plane of a crystal structure of the silicon.

16. The process of claim 13, wherein forming the optical element comprises coating at least a portion of the walls of the depression with a reflective material.

17. A process comprising:

electrically connecting a plurality of lasers respectively to a plurality of sub-mount areas of a first wafer, wherein each laser emits an optical signal;

fabricating a plurality of caps, wherein each cap includes an optical element;

bonding the caps to the first wafer, wherein the lasers are enclosed in respective cavities between the first wafer and the respective caps, and for each of the lasers, the optical element in the corresponding cap is positioned to receive and reflect the optical signal from the laser onto an output path from the cavity; and

dividing the resulting structure to separate a plurality of packages containing the lasers.

18. The process of claim 17, wherein the caps comprise respective areas of a second wafer, and bonding the caps to the wafer comprises bonding the second wafer to the first wafer.

19. The process of claim 18, wherein fabricating the caps comprises:

creating a plurality of depressions in the second wafer, wherein each depression has walls that correspond to walls of a corresponding one of the cavities; and

forming the optical elements as reflectors corresponding to reflective areas on the walls of respective depressions.

20. The process of claim 19, wherein the second wafer comprises silicon, and each of the reflective areas coincides with a <

111>

plane of a crystal structure of the silicon.

21. A structure comprising:

an optoelectronic device;

a sub-mount containing electrical traces that are electrically connected to the optoelectronic device; and

a cap made of silicon that attached to the sub-mount to form a cavity enclosing the optoelectronic device, wherein the cap includes a reflector that is in a path of an optical signal of the optoelectronic device and on a cavity wall along a <

111>

plane of the crystal structure of the silicon.

22. The structure of claim 21, wherein a bond of the cap to the sub-mount hermetically seals the cavity.

23. The structure of claim 21, wherein the optoelectronic device comprises a side-emitting laser.

24. The structure of claim 21, wherein the reflector directs the optical signal out of the structure in a direction that is perpendicular to a direction for which the optical signal emerges from the optoelectronic device.

25. A process comprising:

electrically connecting an optoelectronic device to a sub-mount;

fabricating a cap by etching a silicon substrate to create a depression, and forming a reflective area on a wall of the depression that coincides with a <

111>

plane of a crystal structure of the silicon substrate; and

bonding the cap to the sub-mount, wherein the optoelectronic device is enclosed the depression and an optical signal of the optoelectronic device is incident on the reflective area.

26. The process of claim 25, wherein forming the reflective area comprises coating at least a portion of the wall of the depression with a reflective material.

27. The process of claim 25, further comprising:

electrically connecting a plurality of optoelectronic devices to the sub-mount, wherein each of the optoelectronic devices emits an optical signal; and

etching a plurality of depressions in the silicon substrate, wherein each depression includes a reflective area, wherein

bonding the cap to the sub-mount comprises bonding the silicon substrate to the sub-mount so that the optoelectronic devices are between the sub-mount and the silicon substrate and are respectively enclosed in the depressions, and for each of the optoelectronic devices, the reflective area in the corresponding depression is positioned in a path of the optical signal from the optoelectronic device.

28. The process of claim 27, further comprising dividing a structure including the sub-mount and the silicon substrate to separate a plurality of packages respectively containing the optoelectronic devices.