Capacitive coupling in a direct-bonded interface for microelectronic devices
Capacitive couplings in a direct-bonded interface for microelectronic devices are provided. In an implementation, a microelectronic device includes a first die and a second die direct-bonded together at a bonding interface, a conductive interconnect between the first die and the second die formed at the bonding interface by a metal-to-metal direct bond, and a capacitive interconnect between the first die and the second die formed at the bonding interface. A direct bonding process creates a direct bond between dielectric surfaces of two dies, a direct bond between respective conductive interconnects of the two dies, and a capacitive coupling between the two dies at the bonding interface. In an implementation, a capacitive coupling of each signal line at the bonding interface comprises a dielectric material forming a capacitor at the bonding interface for each signal line. The capacitive couplings result from the same direct bonding process that creates the conductive interconnects direct-bonded together at the same bonding interface.
1. A microelectronic device, comprising:
a dielectric-to-dielectric direct bond between a first die and a second die, the first die and the second die being direct-bonded together at a bonding interface;
a plurality of conductive interconnects configured to be electrically coupled to power or ground, each of the plurality of conductive interconnects comprising a metal-to-metal direct bond between a first metal pad of the first die and a first metal pad of the second die;
a plurality of capacitive interconnects forming signal-passing interfaces between the first die and the second die, each of the plurality of capacitive interconnects comprising a first layer of a first dielectric medium on a second metal pad of the first die, and a second layer of a second dielectric medium on a second metal pad of the second die wherein:
the first metal pads of the first and second dies have a greater width than a width of the second metal pad of the first or second die; and
the widths of the first and second metal pads are measured in a direction parallel to the bonding interface.
2. The microelectronic device of claim 1 , wherein each of the plurality of capacitive interconnects further comprises a polymer layer between the first layer and the second layer.
3. The microelectronic device of claim 2 , wherein the dielectric-to-dielectric direct bond between the first die and the second die creates a capacitive coupling of the plurality of capacitive interconnects.
4. The microelectronic device of claim 2 , wherein the first dielectric medium of the plurality of capacitive interconnects, the second dielectric medium of plurality of capacitive interconnects, and the polymer layer comprises asymmetrical thicknesses with respect to a horizontal plane of the bonding interface between the first die and the second die.
5. The microelectronic device of claim 2 , wherein a thickness and a dielectric constant of the polymer layer determines a capacitance of the plurality of capacitive interconnects.
6. The microelectronic device of claim 2 , wherein at least the first layer or the second layer is direct-bonded to the polymer layer.
7. The microelectronic device of claim 2 , wherein the second metal pads of the first die and the second metal pads of the second die comprise a single capacitive signal line across the bonding interface, and the first layer of the first dielectric medium, the second layer of the second dielectric medium, and the polymer layer are disposed at the bonding interface only between the second metal pads of the first die and the second metal pads of the second die.
8. The microelectronic device of claim 1 , wherein the first die and the second die are direct-bonded together at the bonding interface with a dielectric-to-dielectric direct bond between respective nonmetal surfaces of the first die and the second die.
9. The microelectronic device of claim 1 , wherein each of the second metal pads of the first die are recessed from the bonding interface and each of the second metal pads of the second die are flush with the bonding interface.
10. The microelectronic device of claim 1 , wherein each of the second metal pads of the first die are recessed from the bonding interface and each of the second metal pads of the second die are also recessed from the bonding interface.
11. The microelectronic device of claim 1 , wherein the first dielectric medium of the plurality of capacitive interconnects or the second dielectric medium of the plurality of capacitive interconnects comprises silicon dioxide, silicon nitride, air, or a high dielectric material.
12. The microelectronic device of claim 1 , wherein a spacing distance between the second metal pads in the first die and the second metal pads in the second die is selected to provide a capacitance value for the plurality of capacitive interconnects.
13. The microelectronic device of claim 1 , wherein each of the plurality of conductive interconnects comprises a direct-bonded power interconnect or a direct-bonded ground interconnect.
14. The microelectronic device of claim 1 , wherein each of the plurality of capacitive interconnects comprises a signal line between the first die and the second die.
15. The microelectronic device of claim 1 , further comprising a conductive through-via created by a via-last fabrication process penetrating at least part way into the first die or penetrating at least part way into both the first die and the second die.
16. A process, comprising:
creating a first direct bond between respective dielectric surfaces at a bonding interface of a first die and a second die;
creating a plurality of conductive interconnects electrically coupled to power or ground, each of the plurality of conductive interconnects comprising second direct bonds between first metal pads of the first die and first metal pads of the second die; and
creating a plurality of capacitive interconnects forming signal-passing interfaces between the first die and the second die, each of the plurality of capacitive interconnects comprising capacitive couplings between second metal pads of the first die and second metal pads of the second die at the bonding interface for a capacitive interconnect between the first and second dies, wherein:
the first metal pads of the first and second die have a greater width than a width of the second metal pads of the first or second die, wherein the widths of the first and second metal pads are measured in a direction parallel to the bonding interface for the capacitive interconnect between the first and second dies; and
the plurality of capacitive interconnects each comprises a first layer of a first dielectric medium on the second metal pad of the first die, and a second layer of a second dielectric medium on the second metal pad of the second die.
17. The process of claim 16 , wherein each of the plurality of capacitive interconnects further comprise a polymer layer between the first layer and the second layer.
18. The process of claim 16 , wherein:
the second direct bonds between the first metal pads of the first and second dies are at the bonding interface of a first and second die; and
the second direct bonds between the first metal pads of the first and second dies, and the capacitive couplings between the second metal pads of the first and second dies result from a same direct bonding process at a same bonding interface.
19. The process of claim 16 , wherein:
the first direct bond between the respective dielectric surfaces comprises an oxide-to-oxide direct bond; and
the second direct bonds of respective conductive interconnects comprises a metal-to-metal direct bond.