Photonic semiconductor device and method

1. A method, comprising:

forming silicon waveguide sections in a first oxide layer over a substrate, the first oxide layer disposed on the substrate;

forming a routing structure over the first oxide layer, the routing structure comprising one or more insulating layers and one or more conductive features in the one or more insulating layers;

recessing regions of the routing structure;

forming nitride waveguide sections in the recessed regions of the routing structure, wherein the nitride waveguide sections extend over the silicon waveguide sections;

forming a second oxide layer over the nitride waveguide sections; and

attaching semiconductor dies to the routing structure, the dies electrically connected to the conductive features.

2. The method of claim 1 , further comprising patterning the first oxide layer and the second oxide layer to form a cladding structure surrounding the silicon waveguide sections and the nitride waveguide sections, the cladding structure having exposed sidewalls.

3. The method of claim 1 , wherein the nitride waveguide sections are straight.

4. The method of claim 1 , further comprising forming a photonic device over the first oxide layer, wherein the photonic device comprises silicon, and wherein the photonic device is optically coupled to at least one first waveguide section.

5. The method of claim 4 , wherein the photonic device comprises a modulator.

6. The method of claim 1 , further comprising forming vias extending through the substrate, wherein the conductive features are electrically coupled to the vias.

7. The method of claim 1 , wherein at least one semiconductor die is an integrated photonic die.

8. The method of claim 1 , wherein at least one nitride waveguide section extends over an end portion of a silicon waveguide, the end portion having a tapered shape.

9. The method of claim 1 , further comprising forming an edge coupler over the first oxide layer, the edge coupler comprising silicon nitride, wherein a portion of the edge coupler extends over one of the silicon waveguide sections.

10. A method, comprising:

forming a first photonic structure, comprising:

patterning a silicon layer on a first substrate to form a first set of waveguides, wherein the silicon layer is disposed on a first oxide layer;

forming conductive features over the first set of waveguides; and

removing the first substrate to expose the first oxide layer;

forming a second photonic structure, comprising:

depositing a silicon nitride layer on a second substrate;

patterning the silicon nitride layer to form a second set of waveguides; and

forming a second oxide layer over the second set of waveguides; and

bonding the first photonic structure to the second photonic structure, wherein the first oxide layer is bonded to the second oxide layer, wherein the first set of waveguides is laterally aligned to the second set of waveguides.

11. The method of claim 10 , further comprising connecting a semiconductor die to the conductive features.

12. The method of claim 10 , further comprising patterning the silicon nitride layer to form an edge coupler and recessing the second oxide layer to expose a sidewall of the edge coupler.

13. The method of claim 12 , further comprising etching a trench in the second substrate adjacent the edge coupler, wherein the trench is configured to align an optical fiber with the edge coupler.

14. The method of claim 10 , further comprising attaching the second photonic structure to an interconnect structure.

15. The method of claim 10 , comprising patterning the silicon layer to form photonic devices, the photonic devices optically coupled to the first set of waveguides.

16. The method of claim 10 , wherein the silicon nitride layer is deposited using a low-pressure chemical vapor deposition process comprising a process temperature of 700° C. to 850° C.

17. A photonic device, comprising:

an integrated photonic structure, comprising:

a plurality of oxide layers over a substrate;

a plurality of first waveguides and a plurality of second waveguides within the plurality of oxide layers, wherein the plurality of first waveguides is optically coupled to the plurality of second waveguides, wherein the plurality of first waveguides comprises silicon and the plurality of second waveguides comprises silicon nitride; and

a routing structure over at least a portion of a first waveguide of the plurality of first waveguides, the routing structure comprising a plurality of insulating layers and a plurality of conductive features in the plurality of insulating layers; and

a plurality of semiconductor dies attached to the routing structure, wherein the plurality of semiconductor dies are electrically coupled to the plurality of conductive features.

18. The photonic device of claim 17 , wherein the plurality of first waveguides is closer to the substrate than the plurality of second waveguides.

19. The photonic device of claim 17 , further comprising a photodetector within the plurality of oxide layers, the photodetector optically coupled to a first waveguide and electrically coupled to the plurality of conductive features.

20. The photonic device of claim 17 , further comprising a grating coupler within the plurality of oxide layers, the grating coupler optically coupled to a first waveguide, and further comprising a photodetector within a semiconductor die, the photodetector configured to receive optical signals from the grating coupler.