Bidirectional wafer-level light coupling
A semiconductor structure with bidirectional wafer-level light coupling is provided. In one embodiment, the semiconductor structure includes a bidirectional diffractive grating coupler, where the bidirectional diffractive grating coupler includes a first diffractive grating coupler, a planar waveguide, and a second diffractive grating coupler, a first optical through-silicon via cladding coupled to the first diffractive grating coupler, and a second optical through-silicon via cladding coupled to the first diffractive grating coupler.
1 . A semiconductor structure, comprising:
a bidirectional diffractive grating coupler, wherein the bidirectional diffractive grating coupler includes a first diffractive grating coupler, a planar waveguide, and a second diffractive grating coupler;
a first optical through-silicon via cladding coupled to the first diffractive grating coupler; and
a second optical through-silicon via cladding coupled to the first diffractive grating coupler, wherein the first diffractive grating coupler and the second diffractive grating coupler are connected to opposite ends of the planar waveguide, wherein the first diffractive grating coupler comprises u-shaped grooves facing downward, and wherein the second diffractive grating coupler comprises u-shaped grooves facing upward.
2 . The semiconductor structure of claim 1 , further comprising:
a single mode fiber coupled to at least one of: the first diffractive grating coupler or the second diffractive grating coupler;
wherein the first diffractive grating coupler, the second diffractive grating coupler, and the planar waveguide are disposed within in a monolithic oxide layer;
wherein a backside of the first diffractive grating coupler is void of the u-shaped grooves facing downward such that the backside of the first diffractive grating coupler is continuous with a side of the planar waveguide; and
wherein a backside of the second diffractive grating coupler is void of the u-shaped grooves facing upward such that the backside of the second diffractive grating coupler is continuous with an opposite side of the planar waveguide.
3 . The semiconductor structure of claim 1 , wherein the semiconductor structure includes:
a first layer that includes a backside layer;
a second layer comprising a device layer, wherein the second layer is disposed on the first layer; and
a third layer comprising a frontside layer, wherein the third layer is disposed on the second layer.
4 . The semiconductor structure of claim 3 , wherein the first layer includes SiO 2 ;
wherein the second layer includes a device wafer, a chip, chiplets, an interposer, Si, or glass; and
wherein the third layer includes SiO 2 .
5 . The semiconductor structure of claim 3 , wherein the first optical through-silicon via cladding extends from the first layer to the third layer;
wherein the second optical through-silicon via cladding extends from the first layer to the third layer; and
wherein an optical signal travels through a medium surrounded by the first optical through-silicon via cladding and the second optical through-silicon via cladding, wherein the medium includes a portion of the first layer, a portion of the second layer, and a portion of the third layer.
6 . The semiconductor structure of claim 3 , wherein the bidirectional diffractive grating coupler is disposed in one of: the first layer or the third layer, and wherein the bidirectional diffractive grating coupler includes one of: the first diffractive grating coupler and the second diffractive grating coupler disposed in a same layer of the semiconductor structure, or the first diffractive grating coupler and the second diffractive grating coupler disposed in different layers of the semiconductor structure.
7 . The semiconductor structure of claim 3 , wherein the semiconductor structure includes an optical integrated circuit, wherein the optical integrated circuit includes the bidirectional diffractive grating coupler, the first optical through-silicon via cladding, and the second optical through-silicon via cladding.
8 . The semiconductor structure of claim 7 , wherein the semiconductor structure includes an electrical integrated circuit connected to the optical integrated circuit, wherein the electrical integrated circuit includes a redistribution layer, electrical contacts, and an electrical through-silicon via.
9 . The semiconductor structure of claim 8 , wherein the redistribution layer is disposed in the third layer, and wherein the electrical contacts are disposed in the second layer.
10 . The semiconductor structure of claim 9 , wherein the electrical through-silicon via extends from the first layer to the third layer.
11 . A method comprising:
forming a first diffractive grating coupler on a first face of a top silicon layer of a first wafer, wherein the first wafer includes the top silicon layer disposed on a buried oxide layer, and wherein the buried oxide layer is disposed on a silicon substrate;
forming a first optical through-silicon via cladding and a second optical through-silicon via cladding in a device layer and a frontside layer of a second wafer;
bonding the first wafer to the second wafer, wherein the top silicon layer of the first wafer is bonded to the frontside layer of the second wafer;
removing the silicon substrate and a portion of the buried oxide layer to expose a second face of the top silicon layer; and
forming a second diffractive grating coupler on the second face of the top silicon layer, wherein the first diffractive grating coupler and the second diffractive grating coupler form a bidirectional diffractive grating coupler, wherein the first diffractive grating coupler and the second diffractive grating coupler are connected to opposite ends of the planar waveguide, wherein the first diffractive grating coupler comprises u-shaped grooves facing downward, and wherein the second diffractive grating coupler comprises u-shaped grooves facing upward.
12 . The method of claim 11 , wherein the first optical through-silicon via cladding and the second optical through-silicon via cladding are coupled to the first diffractive grating coupler.
13 . The method of claim 11 , wherein the frontside layer is disposed on the device layer of the second wafer.
14 . The method of claim 11 , wherein a redistribution layer is formed in the frontside layer, wherein the redistribution layer is coupled to electrical contacts, and wherein the electrical contacts are disposed in the device layer of the second wafer.
15 . The method of claim 14 , wherein the redistribution layer is connected to an electrical through-silicon via.
16 . The method of claim 11 , further comprising:
depositing silicon dioxide on the bidirectional diffractive grating coupler and the frontside layer.
17 . The method of claim 11 , further comprising:
removing a portion of the device layer; and
depositing silicon dioxide on a backside of the second wafer to form a backside layer of the second wafer.
18 . The method of claim 17 , wherein the first optical through-silicon via cladding, the second optical through-silicon via cladding, and an electrical through-silicon via extend from the backside layer to the frontside layer.
19 . The method of claim 17 , further comprising:
transferring an optical signal between the frontside layer and the backside layer through a medium surrounded by the first optical through-silicon via cladding and the second optical through-silicon via cladding, wherein the medium includes a portion of the frontside layer, a portion of the device layer, and a portion of the backside layer.
20 . The method of claim 17 , wherein the first optical through-silicon via cladding and the second optical through-silicon via cladding represent one of: sides of a single optical TSV, or separate cladding structures.