Grating couplers with a silicide mirror
Structures for a grating coupler and methods of fabricating a structure for a grating coupler. A silicide layer is formed on a patterned section of a semiconductor layer. The grating structures of a grating coupler are formed over the silicide layer and the section of the semiconductor layer.
1. A structure comprising:
a semiconductor substrate;
a first dielectric layer on the semiconductor substrate;
a semiconductor layer including a section on the first dielectric layer, the semiconductor layer comprised of a single-crystal semiconductor material;
a silicide layer on the section of the semiconductor layer, the silicide layer in direct contact with the section of the semiconductor layer along an interface;
a second dielectric layer over the section of the semiconductor layer and the silicide layer, the second dielectric layer including a portion in contact with the silicide layer;
a grating coupler including a plurality of grating structures positioned on the second dielectric layer over the silicide layer and the section of the semiconductor layer; and
a waveguide positioned on the second dielectric layer, the waveguide coupled with the grating coupler.
2. The structure of claim 1 wherein the silicide layer is positioned between the grating coupler and the section of the semiconductor layer.
3. The structure of claim 1 wherein the section of the semiconductor layer includes a first portion having a first thickness and a second portion having a second thickness, and the silicide layer is disposed on the first portion of the section of the semiconductor layer and on the second portion of the section of the semiconductor layer.
4. The structure of claim 1 wherein the plurality of grating structures are comprised of silicon nitride.
5. The structure of claim 1 wherein the silicide layer and the section of the semiconductor layer provide a bilayer mirror.
6. The structure of claim 1 wherein the section of the semiconductor layer comprises a section of a device layer of a silicon-on-insulator wafer.
7. The structure of claim 1 wherein the silicide layer is positioned between the grating coupler and the section of the semiconductor layer, and the plurality of grating structures are positioned directly over the silicide layer.
8. The structure of claim 1 wherein the section of the semiconductor layer and the silicide layer have an outer boundary that is shared, and the plurality of grating structures are positioned inside the outer boundary.
9. The structure of claim 1 further comprising:
a back-end-of-line stack over the grating coupler; and
a third dielectric layer positioned over the back-end-of-line stack, the third dielectric layer comprised of silicon nitride.
10. The structure of claim 1 wherein the waveguide and the plurality of grating structures are coplanar.
11. The structure of claim 1 wherein the grating coupler includes a plurality of grooves that alternate with the plurality of grating structures, and the second dielectric layer includes portions that fill the plurality of grooves.
12. A method comprising:
patterning a semiconductor layer to form a section on a first dielectric layer that is positioned on a semiconductor substrate;
forming a silicide layer on the section of the semiconductor layer;
forming a second dielectric layer over the section of the semiconductor layer and the silicide layer;
forming a grating coupler including a plurality of grating structures positioned on the second dielectric layer over the silicide layer and the section of the semiconductor layer; and
forming a waveguide positioned on the second dielectric layer,
wherein the first dielectric layer includes a portion in contact with the silicide layer, the waveguide is coupled with the grating coupler, the semiconductor layer is comprised of a single-crystal semiconductor material, and the silicide layer is in direct contact with the section of the semiconductor layer along an interface.
13. The method of claim 12 wherein the silicide layer is positioned between the grating coupler and the section of the semiconductor layer.
14. The method of claim 12 wherein forming the grating coupler comprises:
depositing a third dielectric layer; and
patterning the third dielectric layer to form the plurality of grating structures directly over the silicide layer.
15. The method of claim 12 wherein the section of the semiconductor layer and the silicide layer have an outer boundary, and the plurality of grating structures are positioned inside the outer boundary.
16. The method of claim 12 wherein the section of the semiconductor layer includes a first portion having a first thickness and a second portion having a second thickness, and the silicide layer is disposed on the first portion of the section of the semiconductor layer and on the second portion of the section of the semiconductor layer.
17. The structure of claim 1 wherein the plurality of grating structures have a tapered arrangement as concentric arc shapes of different length, and the silicide layer is trapezoidal.
18. The structure of claim 17 wherein the silicide layer widens with increasing distance from the waveguide, and the plurality of grating structures lengthen with increasing distance from the waveguide.