Bonded electro-optic device with filled void and method of making thereof
A method of forming an electro-optic device includes forming at least one of an electro-optic layer or a waveguide over a first substrate, forming a cladding layer over the at least one of the electro-optic layer or the waveguide, bonding a second substrate over the cladding layer, such that a void is formed at a bonding interface, removing the first substrate such that a gap is formed over the void, and filling the gap with an insulating plug.
1 . A method of forming an electro-optic device, comprising:
forming at least one of an electro-optic layer or a waveguide over a first substrate;
forming a cladding layer over the at least one of the electro-optic layer or the waveguide;
bonding a second substrate over the cladding layer, such that a void is formed at a bonding interface;
removing at least a portion of the first substrate such that a gap is formed, wherein the gap is continuous with the void and extends through at least a portion of the cladding layer; and
filling the gap with an insulating plug.
2 . The method of claim 1 , wherein the step of forming the at least one of the electro-optic layer or the waveguide comprises forming a seed layer, the electro-optic layer, a first layer of cladding material, and a silicon nitride waveguide layer over the first substrate, followed by patterning the silicon nitride waveguide layer into a core of the waveguide.
3 . The method of claim 2 , wherein the first substrate comprises a silicon wafer, a buried oxide layer and a silicon on insulator layer.
4 . The method of claim 3 , wherein the electro-optic layer comprises barium titanate and the seed layer comprises strontium titanate.
5 . The method of claim 3 , wherein the step of forming the cladding layer over the at least one of the electro-optic layer or the waveguide comprises forming a second layer of cladding material over the core of the waveguide, wherein the second layer of cladding material comprises silicon oxide.
6 . The method of claim 5 , wherein the second substrate comprises a device substrate and a silicon oxide layer.
7 . The method of claim 6 , wherein the silicon oxide layer is bonded to the cladding layer such that the void is present at the bonding interface between the silicon oxide layer and the cladding layer.
8 . The method of claim 7 , wherein:
the step of removing at least a portion of the first substrate comprises removing the silicon wafer;
cracks are formed through portions of layers located between the void and the silicon wafer during the step of removing the silicon wafer; and
the gap is formed when the portions of the layers located between the void and the silicon wafer containing the cracks are peeled away to expose the void during or after the step of removing the silicon wafer.
9 . The method of claim 8 , wherein the step of forming the insulating plug comprises filling the gap with an insulating layer followed by planarizing the insulating layer.
10 . The method of claim 9 , further comprising removing the buried oxide layer after forming the insulating plug using the silicon on insulator layer as an etch stop.
11 . The method of claim 10 , wherein a top surface of the insulating plug is located below a top surface of the silicon on insulator layer after removing the buried oxide layer.
12 . The method of claim 11 , further comprising removing the silicon on insulator layer to expose the first cladding layer and the seed layer.
13 . The method of claim 12 , wherein the top surface of the insulating plug is located above a top surface of the first cladding layer and above a top surface of the seed layer.
14 . The method of claim 13 , further comprising forming electrodes in contact with the seed layer after removing the silicon on insulator layer.
15 . An electro-optic device, comprising:
a substrate;
a cladding layer located over the substrate, wherein a bonding interface is present in the cladding layer;
an insulating plug located in the cladding layer and laterally surrounded by the bonding interface; and
at least one of an electro-optic layer or a waveguide embedded in the cladding layer.
16 . The electro-optic device of claim 15 , further comprising a seed layer.
17 . The electro-optic device of claim 16 , wherein the at least one of the electro-optic layer or the waveguide comprises the electro-optic layer, and wherein the seed layer contacts the electro-optic layer.
18 . The electro-optic device of claim 16 , wherein the electro-optic layer comprises barium titanate and the seed layer comprises strontium titanate.
19 . The electro-optic device of claim 15 , wherein the at least one of the electro-optic layer or the waveguide comprises both the electro-optic layer and the waveguide.
20 . The electro-optic device of claim 19 , wherein:
a top surface of the insulating plug extends above a top surface of the cladding layer.