Development of new TSV structure composing of intermetallic compounds

TSV was regarded as the core technology enabling 3D IC integration. For volume production, the requirement of low-cost TSV fabrication process was a big challenge. In order to find a fast filling method, new Cu plating solutions are desirable and some new filling method using solder, Cu cored solder ball were studied. A new TSV structure composed of intermetallic compounds (IMCs) was proposed in present paper and the manufacturing process was introduced. To form such a TSV structure, it needs to fill liquid solder into the vias and accelerate the inter-diffusion of solder and metal on the sidewall of the vias by annealing. The feasibility of the formation of IMC TSVs was studied using SnPb solder. The solder was filled into the vias in which partial annular Cu layer was plated. Successful voids free filling with thin protrusion of solder material on the top of the vias was achieved. Finite element analysis (FEA) of TSV filling with Cu, solder and Sn-based IMC were carried out and the results showed that the IMC filled TSVs can get comparable or even lower stress depending on the CTE of the IMCs. According to present results, it can be concluded that the IMC TSVs have the following merits: fast and low cost forming process, good high temperature stability and the lower stress.