Under-ball metallic layer

An under-ball metallic layer structure over a contact pad such that the contact interface between the under-ball metallic layer and the contact pad is made from a material containing copper, the structure comprising:

• an adhesion layer over the contact pad, wherein the adhesion layer is made from chromium;
• a barrier layer over the adhesion layer;
• and
• a wettable layer over the barrier layer.

A chip structure having bumps thereon, comprising:

• a silicon chip having an active surface with a passivation layer and a plurality of bonding pads thereon, wherein the passivation layer exposes the bonding pads and material forming the bonding pads contains copper;
• an adhesion layer over the bonding pads, wherein material forming the adhesion layer is titanium-tungsten alloy;
• a barrier layer over the adhesion layer, wherein material forming the barrier layer is nickel-vanadium alloy;
• a wettable layer over the barrier layer, wherein material forming the wettable layer includes copper;
• and
• a plurality of solder blocks over the wettable layer.

A chip structure having bumps thereon, comprising:

• a silicon chip having an active surface with a passivation layer and a plurality of bonding pads thereon, wherein the passivation layer exposes the bonding pads and material forming the bonding pads contains copper;
• an adhesion layer over the bonding pads, wherein material forming the adhesion layer is chromium;
• a barrier layer over the adhesion layer, wherein material forming the barrier layer is nickel-vanadium alloy;
• a wettable layer over the barrier layer, wherein material forming the wettable layer includes copper;
• and
• a plurality of solder blocks over the wettable layer.

A chip structure having bumps thereon, comprising:

• a silicon chip having an active surface with a passivation layer and a plurality of bonding pads thereon, wherein the passivation layer exposes the bonding pads and material forming the bonding pads contains copper;
• an adhesion layer over the bonding pads, wherein material forming the adhesion layer is titanium-tungsten alloy;
• a barrier layer over the adhesion layer;
• a wettable layer over the barrier layer;
• and
• a plurality of solder blocks over the wettable layer.

A chip structure having bumps thereon, comprising:

• a silicon chip having an active surface with a passivation layer and a plurality of bonding pads thereon, wherein the passivation layer exposes the bonding pads and material forming the bonding pads contains copper;
• an adhesion layer over the bonding pads, wherein material forming the adhesion layer is chromium;
• a barrier layer over the adhesion layer;
• a wettable layer over the barrier layer;
• and
• a plurality of solder blocks over the wettable layer.