Interposer with planar sidewall surface for optical coupling and methods of forming the same
A device structure includes: an interposer including metal wiring structures and optical waveguides that are embedded in interlayer dielectric layers, wherein the interposer includes a stepped outer sidewall including an outermost vertical surface segment, a laterally-recessed sidewall segment that is laterally recessed relative to the outermost vertical surface segment, and a connecting horizontal surface segment that connects the outermost vertical surface segment and the laterally-recessed vertical sidewall segment; and a fiber access unit having a first end that is optically coupled to a subset of the optical waveguides through at least one optical glue portion that is interposed between the fiber access unit and the laterally-recessed sidewall segment of the stepped outer sidewall.
1 . An assembly comprising:
a composite semiconductor package including an interposer and a semiconductor die that is attached to the interposer, wherein the interposer comprises metal wiring structures and optical waveguides that are embedded in dielectric layers and further comprises a stepped outer sidewall, wherein the stepped outer sidewall comprises a first outermost vertical surface segment located within a vertical plane, a second outermost vertical surface segment located within the vertical plane, a laterally-recessed sidewall segment that is laterally recessed inward relative to the vertical plane, a first connecting horizontal surface segment that connects an edge of the first outermost vertical surface segment to an edge of the laterally-recessed sidewall segment, and a second connecting horizontal surface segment that connects an edge of the second outermost vertical surface segment to another edge of the laterally-recessed sidewall segment;
a molding compound; and
a fiber access unit having a first end that is optically coupled to a subset of the optical waveguides through an optical glue portion that is interposed between the fiber access unit and a laterally-recessed sidewall segment of the stepped outer sidewall, wherein a sidewall of the optical glue portion is aligned with a sidewall of the molding compound.
2 . The assembly of claim 1 , wherein:
the composite semiconductor package comprises a silicon interposer including a silicon substrate and a plurality of through-substrate via structures that vertically extend through the silicon substrate;
the laterally-recessed sidewall segment comprise a sidewall surface segment of the silicon interposer; and
the second connecting horizontal surface segment comprises a horizontal surface segment of the silicon interposer.
3 . The assembly of claim 2 , wherein the optical glue portion contacts the laterally-recessed sidewall segment of the stepped outer sidewall and contacts the horizontal surface segment of the silicon interposer.
4 . The assembly of claim 1 , wherein the optical glue portion comprises:
a first optical glue portion contacting the laterally-recessed sidewall segment and having an outer sidewall within a vertical plane including the first outermost vertical surface segment; and
a second optical glue portion contacting the first end of the fiber access unit and having an inner sidewall that contacts the outer sidewall of the first optical glue portion.
5 . The assembly of claim 1 , wherein the optical glue portion comprises a first optical glue portion having an outer sidewall located within the vertical plane.
6 . The assembly of claim 5 , wherein the outer sidewall of the first optical glue portion is located within the vertical plane.
7 . The assembly of claim 5 , further comprising a second optical glue portion disposed between the first optical glue portion and the fiber access unit, wherein an interface between the second optical glue portion and the first optical glue portion is located entirely within the vertical plane.
8 . The assembly of claim 7 , wherein the second optical glue portion has a different material composition than the first optical glue portion, and contacts the first outermost vertical surface segment and the second outermost vertical surface segment.
9 . The assembly of claim 1 , wherein the molding compound laterally surrounds, and contacts, the semiconductor die.
10 . The assembly of claim 9 , wherein the first outermost vertical surface segment is a sidewall of the molding compound.
11 . The assembly of claim 1 , wherein the interposer comprises:
a silicon substrate; and
through-substrate via structures vertically extending through the silicon substrate and electrically connected to a respective one of the metal wiring structures.
12 . The assembly of claim 11 , wherein the second outermost vertical surface segment comprises a sidewall of the silicon substrate.
13 . The assembly of claim 11 , wherein the interposer comprises interposer-side bonding pads located on an opposite side of the metal wiring structures with respect to the silicon substrate and electrically connected to a respective one of the through-substrate via structures.
14 . The assembly of claim 1 , wherein:
the interposer comprises metallic bonding structures electrically connected to the metal wiring structures; and
the semiconductor die comprises on-die bonding structures that are bonded to the metallic bonding structures by metal-to-metal bonding.
15 . The assembly of claim 1 , wherein the first connecting horizontal surface segment is located within a horizontal plane including an interface between the interposer and the molding compound.
16 . The assembly of claim 1 , further comprising a packaging substrate that is bonded to the interposer, wherein the metal wiring structures are more proximal to the packaging substrate than the optical waveguides are to the packaging substrate.
17 . An assembly comprising:
a composite semiconductor package including an interposer and a semiconductor die that is attached to the interposer, wherein the interposer comprises metal wiring structures and optical waveguides that are embedded in dielectric layers and further comprises a stepped outer sidewall, wherein the stepped outer sidewall comprises a first outermost vertical surface segment located within a vertical plane, a second outermost vertical surface segment located within the vertical plane, a laterally-recessed sidewall segment that is laterally recessed inward relative to the vertical plane, a first connecting horizontal surface segment that connects an edge of the first outermost vertical surface segment to an edge of the laterally-recessed sidewall segment, and a second connecting horizontal surface segment that connects an edge of the second outermost vertical surface segment to another edge of the laterally-recessed sidewall segment;
a molding compound; and
a fiber access unit having a first end that is optically coupled to a subset of the optical waveguides through an optical glue portion that is interposed between the fiber access unit and a laterally-recessed sidewall segment of the stepped outer sidewall, wherein:
a sidewall of the optical glue portion is aligned with a sidewall of the molding compound; and
the first connecting horizontal surface segment comprises a horizontal surface segment of the molding compound.
18 . The assembly of claim 17 , wherein the sidewall of the optical glue portion is located within the vertical plane.
19 . An assembly comprising:
a composite semiconductor package including an interposer and a semiconductor die that is attached to the interposer, wherein the interposer comprises metal wiring structures and optical waveguides that are embedded in dielectric layers and further comprises a stepped outer sidewall, wherein the stepped outer sidewall comprises a first outermost vertical surface segment located within a vertical plane, a second outermost vertical surface segment located within the vertical plane, a laterally-recessed sidewall segment that is laterally recessed inward relative to the vertical plane, a first connecting horizontal surface segment that connects an edge of the first outermost vertical surface segment to an edge of the laterally-recessed sidewall segment, and a second connecting horizontal surface segment that connects an edge of the second outermost vertical surface segment to another edge of the laterally-recessed sidewall segment;
a molding compound;
a fiber access unit having a first end that is optically coupled to a subset of the optical waveguides through an optical glue portion that is interposed between the fiber access unit and a laterally-recessed sidewall segment of the stepped outer sidewall, wherein a sidewall of the optical glue portion is aligned with a sidewall of the molding compound; and
a packaging substrate bonded to the interposer, wherein the semiconductor die is more distal from the packaging substrate than the interposer is from the packaging substrate.
20 . The assembly of claim 19 , wherein the interposer comprises:
a silicon substrate;
through-substrate via structures vertically extending through the silicon substrate and electrically connected to a respective one of the metal wiring structures; and
interposer-side bonding pads electrically connected to the through-substrate via structures and bonded to substrate bonding pads of the packaging substrate.