Reliable single-phase micro-joints with high melting point for 3D TSV chip stacking

摘要

As micro solder-joints downsize to less than 10 um in 3-dimensional (3D) TSV (Through Silicon Via) chip stacking, rapidly fabricating reliable micro-joints without collapse in chip stacking is regarded as a critical issue. A practicable method with a suitable temperature gradient (TG) and Ni/Sn(10 mu m)/Ni interconnection structure was developed compared with conventional transient liquid phase (TLP) bonding. Using this method, the micro-joint fully composed of Ni3Sn4 intermetallic was fabricated within 17 min bonding time. It is nearly three times faster than that under conventional TLP bonding, which may overcome this technology limitation caused by longer bonding times. This fast TG-TLP method provided an asymmetry growth characteristic with thicker Ni3Sn4 at the cold end and thinner Ni3Sn4 at the hot end. The basic micro-joint formation mechanisms were suggested and experimentally verified. Furthermore, the properties of the fabricated Ni3Sn4 micro-joint were evaluated in this study. The results demonstrated its desirable features such as high melting temperature, stable single-phase constitution, stronger mechanical strength and low thermal resistance. Finally, the collapsed micro solder-joint issue was completely solved resulting in higher reliability. (C) 2020 Elsevier B.V. All rights reserved.