Method and structure providing a front-end-of-line and a back-end-of-line coupled waveguides
An integrated structure and method of formation provide a lower level waveguide having a core of a first material and a higher level waveguide having a core of a second material and a coupling region for coupling the two waveguides together. The different core materials provided different coupled waveguides having different light loss characteristics.
1. An integrated structure comprising:
a photonic structure comprising:
a first waveguide having a first core of a first material, the first waveguide having a first light propagation loss parameter; and
a second waveguide having a second core of a second material different from the first material, the second waveguide having a second light propagation loss parameter lower than the first light propagation loss parameter
the second waveguide being located above and evanescently coupled to the first waveguide; and
an electronic structure comprising transistors having gates, wherein the first core is at a level of integration corresponding to the same level of integration as the transistor gates.
2. The integrated structure as in claim 1 , wherein the first material comprises polysilicon.
3. The integrated structure as in claim 2 , wherein the second material comprises silicon nitride.
4. The integrated structure as in claim 2 , wherein a cladding surrounds the first material, at least a portion of the cladding comprises silicon nitride.
5. The integrated structure as in claim 4 , wherein another portion of the cladding comprises an oxide.
6. The integrated structure as in claim 1 , wherein at least one of the first and second waveguides comprises an inwardly tapering profile along at least a portion of its longitudinal extent to increase light coupling between the first and second waveguides.
7. The integrated structure as in claim 6 , wherein the first waveguide comprises the inwardly tapering profile.
8. The integrated structure as in claim 7 , wherein the first waveguide comprises a terraced inwardly tapering profile.
9. The integrated structure as in claim 6 , wherein both the first and second waveguides comprise inwardly tapering profiles at least where the second waveguide is located above the first waveguide.
10. The integrated structure as in claim 1 , wherein the first and second waveguide cores are separated by at least an oxide material.
11. The integrated structure as in claim 1 , wherein the first and second waveguide cores are separated by at least an intervening oxide material.
12. The integrated structure as in claim 1 , wherein the first waveguide core is integrated over a substrate on which electronic circuits are also integrated.
13. The integrated structure as in claim 12 , wherein the first waveguide core is formed of the same material as used to form the transistor gates.
14. The integrated structure as in claim 12 , wherein the second waveguide core is integrated over the substrate at a level of integration above transistors of the electronic circuits.
15. The integrated structure as in claim 14 , further comprising an oxide material over the gates of transistors, wherein the second waveguide core is formed above the oxide material.
16. The integrated structure as in claim 15 , wherein the second waveguide core is formed on the oxide material.
17. The integrated structure as in claim 1 , wherein the first and second waveguides are configured such that light passing through the first waveguide exits the first waveguide and passes through the second waveguide.
18. The integrated structure as in claim 1 , wherein the first and second waveguides are configured such that a first portion of light passing through the first waveguide exits the first waveguide and passes through the second waveguide and a second portion of light passing through the first waveguide continues to pass along the first waveguide.