Study On The Failure Mechanism And Reliability Of Heterogeneous Bonding In LSI

The connection between the internal chip and external pins of the semiconductor package and the connection between the chip play an important role in establishing the electrical connection between the chip and the outside to ensure the smooth input/output between the chip and the outside world.It is the key to the entire subsequent packaging process.Wire bonding occupies a dominant position in chip interconnection methods due to its advantages of simple process,low coat,and application of multiple packaging forms.At present,the most widely used chip interconnection material is the bonding alloy wire.The bonding alloy wire has excellent electrical conductivity,thermal conductivity,and oxidation resistance,and can be used in high-density,high-reliability packaging.During the service of the device,the bonding interface formed by the gold wire and the aluminum pad will be affected by continuous thermal stress.Due to the growth of the Au-Al compound,there are some hidden reliability problems in the bonding,which will affect the long-term reliability of the bonded device.Therefore,studying the bonding interface of gold wire,summarizing the evolution of interface compounds,and seeking ways to improve the reliability of the bonding interface is valuable.This paper show that the bonding interface compounds of high purity Au wires grow rapidly.Due to the formation of voids and the growth of brittle compounds,the long-term reliability of the bonding interface is seriously affected;the hardness of Au wires and increase the process widow.The doping of Al will increase the hardness of Au wire,greatly reduce the roundness of gold wire,and increase the difficulty of bonding process.Au-Pd alloy wire can effectively improve the strength of bonding wire,meanwhile,the accumulation of Pd can inhibit the growth of intermetallic compounds.Au-Al alloy wire can promote the balance of mutual diffusion rate of Au and Al atoms at the bonding interface,and effectively reduce the formation of Kirkendall voids.