Manufacturing optically accessible co-packaged optics
The present disclosure relates to circuit package implementations. The circuit package includes a PIC that allows for the transmission of data photonically between hardware coupled to the PIC. The circuit package further includes one or more spacers that are positioned above the PIC in a manner that allows light to pass through an optical path between the top surface of the circuit package and the PIC. Different spacers can be added to the package at different stages of the manufacturing process such that the optical path is maintained through the manufacturing of the circuit package. The circuit package having the optically accessible PIC may be implemented within the framework of a microelectronic package.
1. A method for manufacturing an integrated circuit (IC) package, comprising:
providing a base assembly comprising a photonic integrated circuit (PIC), the PIC comprising an active element, a coupling element at a surface of the PIC, and one or more waveguides providing an optical path through the PIC between the optical coupling element and the active element for light in an operative wavelength band of the PIC;
attaching a first spacer to a surface of the base assembly over a first portion of the PIC including the optical coupling element, the spacer being transparent for light in the operative wavelength band;
attaching a first electrical IC (EIC) to the surface of the base assembly overlapping a second portion of the PIC away from the optical coupling element;
depositing a first molding compound over the first spacer and the first EIC to form a layer of the first molding compound encapsulating the first EIC and the first spacer; and
removing a first portion of the first molding compound from the layer of the first molding compound to expose a surface of the first spacer opposite the PIC.
2. The method of claim 1 , further comprising, after removing the first portion, attaching an optical interface for an optical fiber to the layer of first molding compound at the exposed surface of the first spacer.
3. The method of claim 2 , wherein the optical interface comprises a fiber array unit (FAU).
4. The method of claim 1 , wherein providing the base assembly comprises attaching a second spacer to a surface of the PIC at the first portion of the PIC, the second spacer being transparent for light in the operative wavelength band;
depositing a second molding compound over the second spacer and the surface of the PIC to form a layer of the second molding compound encapsulating the PIC and the second spacer; and
removing a second portion of the second molding compound from the layer of the second molding compound to expose a surface of the second spacer facing away from the PIC,
wherein the first spacer is subsequently attached to the exposed surface of the second spacer.
5. The method of claim 4 , wherein the first molding compound is the same as the second molding compound.
6. The method of claim 4 , wherein the base carrier comprises electrical interconnects protruding from the surface of the PIC, removing the portion of the second molding compound exposes the electrical interconnects, and attaching the first EIC to the surface of the base assembly electrically connects the first EIC to the active element in the PIC via a first of the electrical interconnects.
7. The method of claim 6 , wherein each of the electrical interconnects comprises a copper pillar.
8. The method of claim 1 , wherein the EIC is a first EIC and the method further comprises, prior to depositing the first molding compound, attaching a second EIC to the surface of the base assembly at a location different from the first EIC.
9. The method of claim 8 , wherein the second EIC is attached overlapping a third portion of the EIC away from the optical coupling element and away from the second portion.
10. The method of claim 9 , wherein the third portion of the EIC is on an opposite side of the PIC from the second portion.
11. The method of claim 8 , wherein the first molding compound is deposited over the second EIC.
12. The method of claim 11 , wherein removing the portion of the first molding compound provides a coplanar surface over the first and second EICs and the first spacer, the coplanar surface being flush with the exposed surface of the first spacer.
13. The method of claim 1 , wherein the first spacer is attached to the surface of the base assembly using a transparent adhesive.
14. The method of claim 1 , wherein depositing the first molding compound comprises applying a flowable precursor over the first spacer and the EIC and curing the precursor.
15. The method of claim 1 , wherein the first molding compound is an epoxy molding compound.
16. The method of claim 1 , wherein removing the portion of first molding compound comprises grinding the first layer of the first molding compound.
17. The method of claim 1 , wherein the active element is an electro-absorption modulator (EAM) or a photodiode.
18. The method of claim 1 , wherein the base assembly comprises a first redistribution layer overlapping the surface of the PIC, the first redistribution layer defining an opening overlapping the optical coupling element.
19. The method of claim 18 , wherein the base assembly further comprises a second redistribution layer positioned on an opposite side of the PIC from the first redistribution layer, the base assembly comprising one or more vias electrically connecting the first redistribution layer with the second redistribution layer.
20. The method of claim 1 , wherein the optical interface comprises one or more focusing elements arranged to focus light from the optical fiber through the first spacer to the optical coupling element.