Layer structures for making direct metal-to-metal bonds at low temperatures in microelectronics

A structure comprising:

• a first substrate with a bonding surface for bonding to a second substrate;
• a dielectric material;
• a conductive via serving as a bonding pad for direct hybrid bonding, the conductive via at least partially confined by the dielectric material, wherein the conductive via has a circular horizontal cross-section with a width of 5 μm or greater;
• and
• a buried metal directly and conductively connected to the conductive via, the buried metal having a width greater than a width of the conductive via and having a vertical thickness between approximately 0.5-1.5 μm.

A structure comprising:

• a first substrate with a first bonding surface configured for direct hybrid bonding the first bonding surface having a first dielectric material and a first bonding pad;
• and
• a second substrate with a second bonding surface having a second dielectric material and a second bonding pad, the second dielectric material contacting and directly bonded to the first dielectric material, the second bonding pad contacting and directly bonded to the first bonding pad without an adhesive, wherein the second substrate comprises:
• a conductive via serving as the second bonding pad and disposed within the dielectric material, an upper surface of the conductive via being part of the bonding surface for direct hybrid bonding, the conductive via having a vertical thickness between approximately 0.6-2.0 μm;
• and
• a buried metal directly and conductively connected to the conductive via and having a horizontal footprint greater than a horizontal footprint of the conductive via, at least part of the buried metal configured to direct thermal expansion of the conductive via vertically.

A method, comprising:

• applying a first dielectric structure to a first substrate;
• forming a first trench or via in the first dielectric structure;
• filling the first trench or via with one or more metals having a thickness above the substrate of approximately 0.5-1.5 μm;
• applying a second dielectric structure onto the first dielectric structure and onto the one or more metals;
• forming a second trench or via in the second dielectric structure with a smaller cross-section than the first trench or via;
• at least partly filling the second trench or via with a conductive material directly in contact with the one or more metals to form a first conductive via having a thickness above the first trench of approximately 0.6-2.0 μm;
• and
• planarizing at least the second dielectric structure and exposing the first conductive via to create a bonding surface for direct hybrid bonding to a second substrate.

An apparatus comprising:

• a first element having a first dielectric material and a first bonding pad;
• and
• a second element comprising:
• a semiconductor die;
• a second dielectric material above the semiconductor die with a bonding surface contacting and directly bonded to the first dielectric material;
• a conductive via within the dielectric material, the conductive via serving as a second bonding pad and forming part of the bonding surface for direct hybrid bonding and having a thickness of 0.6-2.0 μm, the second bonding pad contacting and directly bonded to the first bonding pad without an adhesive;
• and
• a buried metal between the semiconductor die and the conductive via conductively and directly connected to the conductive via and having a horizontal footprint greater than a horizontal footprint of the conductive via, at least part of the buried metal configured to direct thermal expansion of the conductive via vertically.

A structure comprising:

• a first substrate with a bonding surface configured for direct hybrid bonding to a second substrate;
• a dielectric material that forms a first portion of the bonding surface for direct hybrid bonding;
• a bonding pad that forms a second portion of the bonding surface for direct hybrid bonding, the bonding pad at least partially confined by the dielectric material;
• and
• a buried metal directly and conductively connected to the bonding pad,
• wherein at least the second portion of the bonding surface of the bonding pad comprises copper metal with lattice planes possessing mostly 111 Miller indices oriented for diffusion of copper atoms across a bond interface for direct metal-to-metal bonding.