Cu wire and beyond - Ag wire an alternative to Cu?
Gold (Au) and aluminum (Al) has been used for wire bonding interconnect for decades. Recently, copper (Cu) is used in high temperature applications and general cost down approaches. Cu induces a higher stress on the bond pad and underlying structure due to its inherent hardness value. In this paper, we will investigate silver (Ag) as fairly new alternative for bonding wire. An overlap in terms of application exists with all other wire materials, but the package and product requirements may justify the introduction of an additional material. To assess the impact of Ag as bonding wire we have investigated the bonding on chips with active area and compared the responses with Au and Cu wires. A robust Cu based bond pad with Nickel (Ni) and Palladium (Pd) layers as the pad stacks were used. Initial bonding responses show similar results for Ag and Au. Both Ag and Au show less impact on the bond pad than Cu. This encourages further investigation of Ag as a bonding wire alternative.