Devices and techniques including process steps make use of recesses in conductive interconnect structures to form reliable low temperature metallic bonds. A fill layer is deposited into the recesses prior to bonding. First conductive interconnect structures are bonded at ambient temperatures to second metallic interconnect structures using direct bonding techniques, with the fill layers in the recesses in one or both of the first and second interconnect structures.

A direct bond hybridization (DBH) method is provided. The DBH method includes preparing a first underlying layer, a first contact layer disposed on the first underlying layer and a first contact electrically communicative with the first underlying layer and protruding through the first contact layer, preparing a second underlying layer, a second contact electrically communicative with the second underlying layer and formed of softer material than the first contact and a second contact layer disposed on the second underlying layer and defining an aperture about the second contact and a moat at least partially surrounding the second contact and bonding the first and second contact layers whereby the first contact contacts the second contact such that the second contact deforms and expands into the moat.

A direct bond hybridization (DBH) method is provided. The DBH method includes preparing a first underlying layer, a first contact layer disposed on the first underlying layer and a first contact electrically communicative with the first underlying layer and protruding through the first contact layer, preparing a second underlying layer, a second contact electrically communicative with the second underlying layer and formed of softer material than the first contact and a second contact layer disposed on the second underlying layer and defining an aperture about the second contact and a moat at least partially surrounding the second contact and bonding the first and second contact layers whereby the first contact contacts the second contact such that the second contact deforms and expands into the moat.

A structure of a semiconductor package is disclosed. The structure includes a first substrate including a first interconnect structure. The structure includes a second substrate including a second interconnect structure, the second substrate bonded to the first substrate. The structure includes a connection pad interposed between the first interconnect structure and the second interconnect structure. The connection pad includes a material configured to switch between a high resistance state and a low resistance state. The material of the connection pad includes a phase change material.

A device package includes a first die directly bonded to a second die at an interface, wherein the interface comprises a conductor-to-conductor bond. The device package further includes an encapsulant surrounding the first die and the second die and a plurality of through vias extending through the encapsulant. The plurality of through vias are disposed adjacent the first die and the second die. The device package further includes a plurality of thermal vias extending through the encapsulant and a redistribution structure electrically connected to the first die, the second die, and the plurality of through vias. The plurality of thermal vias is disposed on a surface of the second die and adjacent the first die.

A device package includes a first die directly bonded to a second die at an interface, wherein the interface comprises a conductor-to-conductor bond. The device package further includes an encapsulant surrounding the first die and the second die and a plurality of through vias extending through the encapsulant. The plurality of through vias are disposed adjacent the first die and the second die. The device package further includes a plurality of thermal vias extending through the encapsulant and a redistribution structure electrically connected to the first die, the second die, and the plurality of through vias. The plurality of thermal vias is disposed on a surface of the second die and adjacent the first die.

First and second contacts are formed on first and second wafers from disparate first and second conductive materials, at least one of which is subject to surface oxidation when exposed to air. A layer of oxide-inhibiting material is disposed over a bonding surface of the first contact and the first and second wafers are positioned relative to one another such that a bonding surface of the second contact is in physical contact with the layer of oxide-inhibiting material. Thereafter, the first and second contacts and the layer of oxide-inhibiting material are heated to a temperature that renders the first and second contacts and the layer of oxide-inhibiting material to liquid phases such that at least the first and second contacts alloy into a eutectic bond.

A method of making an assembly can include juxtaposing a top surface of a first electrically conductive element at a first surface of a first substrate with a top surface of a second electrically conductive element at a major surface of a second substrate. One of: the top surface of the first conductive element can be recessed below the first surface, or the top surface of the second conductive element can be recessed below the major surface. Electrically conductive nanoparticles can be disposed between the top surfaces of the first and second conductive elements. The conductive nanoparticles can have long dimensions smaller than 100 nanometers. The method can also include elevating a temperature at least at interfaces of the juxtaposed first and second conductive elements to a joining temperature at which the conductive nanoparticles can cause metallurgical joints to form between the juxtaposed first and second conductive elements.

A method of making an assembly can include juxtaposing a top surface of a first electrically conductive element at a first surface of a first substrate with a top surface of a second electrically conductive element at a major surface of a second substrate. One of: the top surface of the first conductive element can be recessed below the first surface, or the top surface of the second conductive element can be recessed below the major surface. Electrically conductive nanoparticles can be disposed between the top surfaces of the first and second conductive elements. The conductive nanoparticles can have long dimensions smaller than 100 nanometers. The method can also include elevating a temperature at least at interfaces of the juxtaposed first and second conductive elements to a joining temperature at which the conductive nanoparticles can cause metallurgical joints to form between the juxtaposed first and second conductive elements.

A multi-chip unit suitable for chip-level packaging may include multiple IC chips that are interconnected through a metal redistribution structure, and that are directly bonded to an integrated heat spreader. Bonding of the integrated heat spreader to the multiple IC chips may be direct so that no thermal interface material (TIM) is needed, resulting in a reduced bond line thickness (BLT) and lower thermal resistance. The integrated heat spreader may further serve as a structural member of the multi-chip unit, allowing a second side of the redistribution structure to be further interconnected to a host by solder interconnects. The redistribution structure may be fabricated on a sacrificial interposer that may facilitate planarizing IC chips of differing thickness prior to bonding the heat spreader. The sacrificial interposer may be removed to expose the RDL for further interconnection to a substrate without the use of through-substrate vias.