Alternate pad structures/passivation inegration schemes to reduce or eliminate IMC cracking in post wire bonded dies during Cu/Low-K BEOL processing
View Patent ↗Passivation integration schemes and pad structures to reduce the stress gradients and/or improve the contact surface existing between the Al in the pad and the gold wire bond. One of the pad structures provides a plurality of recessed pad areas which are formed in a single aluminum pad. An oxide mesa can be provided under the aluminum pad. Another pad structure provides a single recessed pad area which is formed in a single aluminum pad, and the aluminum pad is disposed above a copper pad and a plurality of trench/via pads. Still another pad structure provides a single recessed pad area which is formed in a single aluminum pad, and the aluminum pad is disposed above a portion of a copper pad, such that the aluminum pad and the copper pad are staggered relative to each other.
1. A pad structure comprising: at least one copper pad; an aluminum pad above the copper pad, and a plurality of recessed pad areas formed in the aluminum pad above one of said at least one copper pad, wherein the aluminum pad provides a plurality of slots each having a top surface and a plurality of islands each having a top surface, wherein the top surface of each of the slots extends deeper than the top surface of each of the islands, wherein the pad structure further comprises oxide blocks in the islands, each of said oxide blocks having a top surface, wherein the top surface of each of the slots extends deeper than the top surface of the oxide blocks in the islands, wherein said plurality of slots comprises a first slot and a second slot, wherein there are a plurality of slots and islands disposed between the first slot and the second slot, above one of said at least one copper pad; a first layer along an entire bottom surface of the aluminum pad and in contact with the top surface of each oxide block; and a second layer along an entire top surface of the at least one copper pad and in contact with both the oxide blocks and portions of the first layer.
2. A pad structure as recited in claim 1 , wherein the aluminum pad is above a single copper pad.
3. A pad structure as recited in claim 1 , wherein the second layer comprises a single nitride layer.