Light emitting semiconductor device
View Patent ↗A fiber coupled semiconductor device and a method of manufacturing of such a device are disclosed. The method provides an improved stability of optical coupling during assembly of the device, whereby a higher optical power levels and higher overall efficiency of the fiber coupled device can be achieved. The improvement is achieved by attaching the optical fiber to a vertical mounting surface of a fiber mount. The platform holding the semiconductor chip and the optical fiber can be mounted onto a spacer mounted on a base. The spacer has an area smaller than the area of the platform, for mechanical decoupling of thermally induced deformation of the base from a deformation of the platform of the semiconductor device. Optionally, attaching the fiber mount to a submount of the semiconductor chip further improves thermal stability of the packaged device.
1. A method of assembly of a semiconductor device, comprising:
(a) providing a semiconductor device subassembly having a chip mounting surface and including a platform and a semiconductor chip mounted flat on the chip mounting surface and thermally coupled to the platform for removing heat from the semiconductor chip;
(b) attaching a fiber mount to the semiconductor device subassembly, the fiber mount having a planar fiber mounting surface;
(c) optically coupling an optical fiber to the semiconductor chip for receiving light therefrom, wherein the optical fiber extends lengthwise parallel to the fiber mounting surface and the chip mounting surface; and
(d) attaching a bare section of the optical fiber directly to the fiber mounting surface,
wherein the fiber mounting surface is disposed perpendicular to the chip mounting surface, whereby a change of the optical coupling upon attaching the optical fiber to the fiber mount is lessened.
2. The method of claim 1 , wherein step (d) includes epoxying the bare section of the optical fiber directly to the fiber mounting surface.
3. The method of claim 2 , wherein step (d) includes curing a UV curable epoxy with a UV light source.
4. The method of claim 3 , wherein the fiber mount is substantially transparent to UV light emitted by the UV light source.
5. The method of claim 3 , wherein in step (d) includes heating the UV curable epoxy to an elevated temperature higher than ambient temperature, for increasing a glass transition temperature of the UV curable epoxy.
6. The method of claim 5 , wherein the UV curable epoxy is heated to a temperature between 35° C. and 70° C.
7. The method of claim 5 , including matching a coefficient of thermal expansion of the fiber mount to a coefficient of thermal expansion of the semiconductor device subassembly to within 5 ppm/° C., for reducing a change of the optical coupling upon curing of the UV curable epoxy at the elevated temperature.
8. The method of claim 1 , wherein step (a) includes
(i) providing a submount including a top surface comprising the chip mounting surface, and a bottom surface disposed opposite the top surface, the bottom surface having a submount mounting area;
(ii) mounting the semiconductor chip directly on the chip mounting surface of the submount;
(iii) mounting the submount mounting area directly on the platform, for supporting the semiconductor chip and for thermally coupling the semiconductor chip to the platform;
wherein in step (b), the fiber mount is attached directly to the submount, whereby sensitivity of the optical coupling between the semiconductor chip and the optical fiber to deformation of the platform is lessened.
9. The method of claim 8 , wherein the platform has a bottom surface with a platform mounting area, the method further including
(e) providing a thermoelectric cooler and a spacer;
(f) mounting the spacer on a top surface of the thermoelectric cooler; and
(g) mounting the platform mounting area on the spacer, so that the platform mounting area is smaller than each of: a total area of the bottom surface of the platform; and a total area of the top surface of the thermoelectric cooler, whereby sensitivity of the optical coupling between the semiconductor chip and the optical fiber to deformation of the thermoelectric cooler is lessened.
10. The method of claim 9 , wherein in step (g), the platform mounting area and the bottom surface of the platform each have a length in a direction of a length of the optical fiber, wherein the length of the platform mounting area is between 30% and 80% of the length of the bottom surface of the platform.
11. The method of claim 1 , wherein step (d) includes glass soldering the bare section of the optical fiber directly to the fiber mounting surface.
12. An assembly comprising:
a semiconductor device subassembly having a chip mounting surface and including a platform and a semiconductor chip mounted flat on the chip mounting surface and thermally coupled to the platform for removing heat from the semiconductor chip;
a fiber mount attached to the semiconductor device subassembly, the fiber mount having a planar fiber mounting surface; and
an optical fiber having a bare fiber section attached directly to the fiber mounting surface and optically coupled to the semiconductor chip for receiving light therefrom, wherein the optical fiber extends lengthwise parallel to the fiber mounting surface and the chip mounting surface;
wherein the fiber mounting surface is disposed perpendicular to the chip mounting surface, whereby a dependence of the optical coupling between the semiconductor chip and the optical fiber on temperature of the assembly is lessened.
13. The assembly of claim 12 , wherein the bare fiber section of the optical fiber is attached directly to the fiber mounting surface with an epoxy.
14. The assembly of claim 13 , wherein the epoxy is a UV curable epoxy.
15. The assembly of claim 14 , wherein the fiber mount is substantially transparent to UV light for curing the UV curable epoxy.
16. The assembly of claim 15 , wherein a coefficient of thermal expansion of the fiber mount differs from a coefficient of thermal expansion of the semiconductor device subassembly by less than 5 ppm/° C.
17. The assembly of claim 12 , wherein the optical fiber is a lensed optical fiber having an anamorphic fiber lens having mutually orthogonal first and second optical planes parallel to the chip mounting surface and the fiber mounting surface, respectively.
18. The assembly of claim 12 , wherein the semiconductor device subassembly further includes a submount including opposed top and bottom surfaces, wherein the top surface includes the chip mounting surface on which the semiconductor chip is mounted, and wherein the bottom surface includes a submount mounting area for mounting the submount directly on the platform, for thermally coupling the semiconductor chip to the platform.
19. The assembly of claim 18 , wherein the fiber mount is attached directly to the submount, whereby a dependence of the optical coupling between the semiconductor chip and the optical fiber on temperature of the assembly is lessened.
20. The assembly of claim 19 , wherein the platform has a bottom surface with a platform mounting area, the assembly further including a thermoelectric cooler and a spacer mounted on a top surface thereof,
wherein the platform mounting area is mounted on the spacer; and
wherein the platform mounting area is smaller than each of: a total area of the bottom surface of the platform; and a total area of the top surface of the thermoelectric cooler, whereby sensitivity of the optical coupling between the semiconductor chip and the optical fiber to deformation of the thermoelectric cooler is lessened.
21. The assembly of claim 20 , wherein the platform mounting area and the bottom surface of the platform each have a length in a direction of a length of the optical fiber, wherein the length of the platform mounting area is between 30% and 80% of the length of the bottom surface of the platform.
22. The assembly of claim 21 , wherein the submount mounting area is disposed over the platform mounting area.
23. The assembly of claim 12 , wherein the semiconductor chip is a laser diode chip.
24. The assembly of claim 12 , wherein the bare fiber section of the optical fiber is attached directly to the fiber mounting surface with a glass solder.