Patent ID: 8293587

Claim:
A method of forming a copper interconnect pillar, the method comprising: forming a first copper layer; forming a first nickel barrier protective layer in direct contact on the first copper layer; forming a substantially planar first intermediate layer in direct contact with the first nickel barrier protective layer on the first copper layer, the first intermediate layer having a modulus of elasticity lower than the first copper layer, and the first intermediate layer being a single material comprising one of tin, bismuth and indium; forming a second nickel barrier protective layer in direct contact with the first intermediate layer, on a surface opposing the first nickel barrier protective layer; forming a second copper layer in direct contact with the second nickel barrier protective layer on an opposing side thereof to the first intermediate layer, the first intermediate layer having a modulus of elasticity lower than the second copper layer; and bonding a chip to the first copper layer and a substrate to the second copper layer.