Low-Temperature SLID-TSV Interconnects for 3-D (MEMS) Packaging

Abstract

Three-dimensional heterogeneous integration is becoming increasingly important in advanced packaging as device functionalities expand within smaller spaces. Three-dimensional interconnects such as through silicon via (TSV)-solid–liquid interdiffusion (SLID) interconnects offer a promising approach for achieving miniaturization, high integration, and reduced power consumption. However, well-known Cu–Sn SLID-TSVs require high bonding temperatures, leading to residual stress and cracks. This research focuses on developing 3-D interconnects by using Cu–Sn–In/Co SLID-TSVs, which decrease bonding temperatures and reduce these issues. Finite element (FE) simulations qualitatively compared stress states in both SLID-TSV systems, showing lower residual stress in the Cu–Sn–In/Co SLID system than in Cu–Sn SLID. The Cu–Sn–In/Co SLID-TSV underwent microstructural analysis and reliability tests, including high-temperature storage (HTS), thermal shock (TS), and tensile strength testing. Most samples were free of voids and cracks, with a few showing minor defects along the bond line after TS. No cracks were observed inside the Si and TSVs. This indicates that adopting the Cu–Sn–In/Co system and reducing the bonding temperature to 200 °C can effectively prevent crack formations across bond lines, Si, and TSVs. Furthermore, all the samples meet the tensile strength requirements according to MIL-STD-883 method 2027.2, with the highest value observed for HTS-tested samples. Hence, low-temperature 3-D SLID-TSV interconnects were successfully demonstrated, showing strong potential for 3-D MEMS-ICs.