Metal bump joint structure

A device comprising:

• a first semiconductor chip comprising:
• a first semiconductor substrate;
• a first interconnect structure formed on the first semiconductor substrate;
• a first copper bump formed on the first interconnect structure;
• and
• a first barrier layer on a first planar surface of the first copper bump and not on a second surface of the first copper bump;
• a second semiconductor chip stacked on the first semiconductor chip, wherein the second semiconductor chip comprises:
• a second semiconductor substrate;
• a second interconnect structure formed on the second semiconductor substrate;
• a second copper bump formed on over the second interconnect structure;
• and
• a second barrier layer on a third planar surface of the second copper bump and not on a fourth surface of the second copper bump;
• and
• a solder joint structure electrically connecting the first copper bump and the second copper bump, wherein the solder joint structure comprises:
• an intermetallic compound region formed between the first barrier layer and the second barrier, wherein the intermetallic compound region has a vertical dimension from the first barrier layer to the second barrier layer;
• and
• a surrounding portion formed along exterior walls of the first copper bump and the second copper bump, wherein the surrounding portion a lateral dimension from a point aligned with at least one of walls of the first barrier layer and the second barrier layer to a nearest exterior surface of the surrounding portion, and wherein the lateral dimension is greater than the vertical dimension.

A structure comprising:

• a first package component having a first copper bump on a first surface of the first package component and a first barrier layer on the first copper bump disposed distally from the first surface, the first barrier layer comprising a first material different from copper;
• a second package component having a second copper bump on a second surface of the second package component and a second barrier layer on the second copper bump disposed distally from the second surface, the second barrier layer comprising a second material different from copper;
• a intermetallic compound region between the first barrier layer and the second barrier layer and comprising an intermetallic compound, the intermetallic compound region having a vertical dimension from the first barrier layer and the second barrier layer;
• and
• a surrounding portion along respective walls of the first copper bump, the first barrier layer, the second copper bump, and the second barrier layer, the surround portion comprising a solder material, the intermetallic compound comprising at least one element of the solder material and at least one element of the first material and/or the second material, the surrounding portion having a lateral dimension from a point aligned with at least one of the respective walls of the first barrier layer and the second barrier layer to a nearest exterior surface of the surrounding portion, the lateral dimension being greater than the vertical dimension.