Optical through silicon via
The present disclosure relates to semiconductor structures and, more particularly, to optical via connections in chip-to-chip transmission in a 3D chip stack structure using an optical via, and methods of manufacture. The structure has a first wafer, including a first waveguide coupled to an optical resonator in the first wafer, and a second wafer, including a second waveguide, located over the first wafer. The structure also includes an optical via extending between the optical resonator of the first wafer and the second waveguide of the second wafer to optically couple the first and second waveguides.
1. A structure, comprising:
a first wafer including a first waveguide coupled to an optical resonator in the first wafer;
a second wafer, including a second waveguide, located over the first wafer; and
an optical via extending between the optical resonator of the first wafer and the second waveguide of the second wafer to optically couple the first and second waveguides,
wherein the optical resonator and the optical via form a ring resonator,
the optical via includes silicon to optically couple the optical resonator of the first wafer to the second waveguide of the second wafer, and
the optical via is filled with a polysilicon film structure to tune a wavelength of optical signal passing through the optical via by thermal heating of the polysilicon film.
2. The structure of claim 1 , wherein the optical via is a cylindrical via and includes transparent layers and a transparent dielectric fill.
3. The structure of claim 2 , wherein the first and second waveguides are linear silicon waveguides.
4. The structure of claim 1 , wherein the optical via contacts an upper surface of the optical resonator which faces the second waveguide.
5. The structure of claim 4 , wherein the first waveguide is spaced apart from the optical resonator by 0.1-0.5 μm in the first wafer.
6. The structure of claim 1 , wherein the optical via includes at least one of a PN diode and a PIN diode structured to tune a wavelength of an optical signal passing through the optical via by biasing a junction of the diode.
7. The structure of claim 1 , wherein the optical via is filled with a conductive material to couple light from the optical resonator of the first wafer laterally to a sidewall of the second waveguide of the second wafer through a sidewall of the optical via.
8. The structure of claim 7 , wherein the sidewall of the optical via has a thickness of 0.1-0.5 μm at a location adjacent to the sidewall of the second waveguide.
9. The structure of claim 1 , wherein the optical via is filled with a conductive material which extends over an upper surface of the second waveguide to vertically couple light from the optical resonator to the upper surface of the second waveguide through an insulator formed over the upper surface of the second waveguide.
10. The structure of claim 9 , wherein the insulator has a thickness of 0.1-0.5 μm.
11. A system comprising:
a first wafer includes photonics, a first waveguide and an optical resonator;
a second wafer including a second waveguide; and
an optical via extending from the optical resonator of the first wafer and through an opening in the second wafer,
wherein the optical via is filled with an optically transmissive material and with a transparent electrically conductive material along a sidewall of the via, wherein the transparent electrically conductive material contacts an upper surface of the optical resonator and extends to a location adjacent a side surface of the second waveguide, and
the transparent electrically conductive material comprises a first polysilicon layer having a first conductivity type and a second polysilicon layer formed over the first polysilicon layer and having a second conductivity type.
12. The system of claim 11 , wherein the optical via further includes an insulating material formed on a sidewall of the via and separating the first and second polysilicon layers from the second waveguide, and the first and second polysilicon layers extend over an upper surface of the second waveguide.
13. The system of claim 12 , wherein the first and second polysilicon layers are configured to receive a bias voltage to control light flow through the via between the ring resonator first wafer and the second waveguide of the second wafer.
14. The system of claim 13 , further comprising a control system to control the bias voltage applied to the first and second polysilicon layers based on changes in thermal and/or ambient conditions.
15. A method comprising:
forming an optical via between a first wafer having an optical resonator and a second wafer having an optical waveguide to optically couple the optical resonator of the first wafer with the optical waveguide of the second wafer; and
forming an insulator over an upper surface of the optical waveguide,
wherein the optical via is filled with a conductive material which extends over the upper surface of the optical waveguide to vertically couple light from the optical resonator to the upper surface of the optical waveguide through the insulator formed over the upper surface of the optical waveguide.
16. The method of claim 15 , wherein the conductive material extends through the optical via to be adjacent to a sidewall of the optical waveguide of the second wafer.
17. The method of claim 16 , further comprising controlling a wavelength of an optical signal passing through the optical via by applying a bias voltage to the conductive material.