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

Abstract

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, Cu 2 In and Cu 7 In 3 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 -cm 2 . 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. Index Terms-3-D integration, Cu/In bonding, interconnect.

Interfacial reaction and mechanical properties for Cu/Sn/Ag system low temperature transient liquid phase bonding

“…For the base metal, it is majorly focused on the Cu, Ag and Au series [9,[11][12][13][14][15][16][17][18][19], while researches on Ni, Pd and Pt have been also reported in recent years [20,21]. The primary criterion for selection of an interlayer is melting point and compatibility with base metal such as high solubility and high diffusivity.…”

“…Wherein, unitary system contains Sn (232°C) and In (156°C), and binary or ternary system includes In-Sn (120°C), In-Bi (89°C), Sn-Bi (139°C) and In-Sn-Bi (60°C) alloys [22]. In general, LTTLP bonding process is often conducted at temperatures higher than melting point of the interlayer by a range of 15-120°C, and bonding time mainly depends on the thickness of the interlayer [9,[15][16][17][18][19]. Most of studies concentrated on microstructure evolution [9,21,23], interfacial reaction [12,13,21], kinetics of the IMCs growth [12,13], thermal reliability [24,25], and electrical or mechanical behaviors of the joints [9,11,23] for above systems applied in electronic packaging and interconnects.…”