Low-Temperature Bonded Cu/In Interconnect With High Thermal Stability for 3-D Integration

Low-temperature (170°C) Cu/In wafer-level and chip-level bonding for good thermal budget has been successfully developed for 3-D integration applications. For the well-bonded interconnect, Cu₂In and Cu₇In₃ phases with high melting temperature of 388.3°C and 632.2°C can be formed, indicating high thermal stability. In addition, stable low specific contact resistance of bonded interfaces can be achieved with the values of approximately 0.3×10^-8 Ω-cm². In addition to exceptional electrical characteristics, the results of electrical reliability assessments including current stressing, temperature cycling, and unbiased HAST show excellent stability of Cu/In bonds without obvious deterioration. The low-temperature Cu/In bonding technology presents good bond quality and electrical performance, and possesses a great potential for future applications of 3-D interconnects.