Low temperature bonded structures

A microelectronic assembly, comprising:

• a first substrate having a surface and a first conductive interconnect structure;
• a second substrate having a surface and a second conductive interconnect structure;
• the first substrate intimately bonded to the second substrate and the first conductive interconnect structure bonded to the second conductive interconnect structure;
• and
• an electrically conductive alloy region coupling the first conductive interconnect structure to the second conductive interconnect structure, wherein the conductive alloy region includes a first material and a second material, and wherein a composition of the first material or a composition of the second material is less than 10% of a composition of the first conductive interconnect structure and the second conductive interconnect structure combined.

A method, comprising:

• forming a bonding surface of a first substrate, the first substrate including a first metallic feature embedded into the bonding surface of the first substrate;
• forming a bonding surface of a second substrate, the second substrate including a second metallic feature embedded into the bonding surface of the second substrate;
• forming a discontinuous layer of a first metallic material onto a surface of the first and/or second metallic features, the first metallic material being different from a material of the first or second metallic features;
• and
• bonding the bonding surface of the second substrate to the bonding surface of the first substrate via direct bonding, and mechanically or electrically coupling the first metallic feature to the second metallic feature.