Reliability challenges of Cu wire deployment in flash memory packaging

Cu wirebonding become a great interest of industry in recent years due to its cost effectiveness and electrical and mechanical properties. However, several Cu wire bond reliability challenges are the key concerns in Cu wire deployment in semiconductor packaging. These include Cu wire oxidation and CuAl interface corrosion post HAST or UHAST reliability test. Bond reliability at a Cu wire bond under a humid environment is a major concern in replacing Au wires. Conventional bare Cu bonding wires, in general, are more susceptible to moisture corrosion compared to Au wire. This paper discusses the key reliability challenges Cu wire used in flash fineline BGA package. Cu wire IMD cracking induced by excessive ultrasonic bonding force, Cu wire oxidation due to long staging and Cu ball bond corrosion are discussed in this paper. Failure mechanisms and proposals for reliability improvement have been proposed and discussed in this paper.