The interfacial reaction and microstructure of Co/In/Cu sputtering target assembly after soldering

Large target is essential for the fabrication of semiconductor devices, and the reliability of sputtering target backplate assembly plays a key role on the quality of sputtered films in the devices. In this work, the interface of an 8-inch Co target soldered on Cu backplate by In alloy is studied and characterized systematically. At the Cu backplate side, there are many void defects, and only one kind of intermetallic compound (IMC), namely Cu11In9, was observed after soldering. This Cu11In9 layer consists of two sublayers, which were formed at different reaction stage during soldering. At the Co target side, the voids are small, and the formed IMC is Ni28In72 phase. There is a thin Ni(V) layer at the Co side, and the V element is concentrated and stable at the interface, while Co will diffuse into Ni(V) layer to form a solid solution. The interfacial reaction and IMC formation related mechanisms are discussed, which can provide guidance for the design and fabrication of large-scale sputtering target assembly in microelectronic industry.