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Hybrid bonding enables the commercialization of ultra‐fine pitch high‐density 3D packages. Cu/SiO2 hybrid bonding is the standard packing interface recently introduced in the industry. Herein, the Cu/polymer hybrid bonding interface beyond Cu/SiO2 is proposed in order to have high compatibility for additional processes in the future. Ideally, polymers can provide excellent bonding strength and low permittivity, enabling high‐speed signal transmission with high reliability. To realize it, optimum polymer and additives selection and polymer bonding processing development are needed to get the desired packaging interface. Therefore, detailed materials and processing challenges are discussed to realize the successful Cu/polymer hybrid bonding. Then, the authors' preliminary results are suggested to supplement the feasibility of the emerging bonding technology. [ABSTRACT FROM AUTHOR]

Low-temperature Cu-Cu bonding technology plays a key role in high-density and high-performance 3D interconnects. Despite the advantages of good electrical and thermal conductivity and the potential for fine pitch patterns, Cu bonding is vulnerable to oxidation and the high temperature of the bonding process. In this study, chip-level Cu bonding using an Ag nanofilm at 150 °C and 180 °C was studied in air, and the effect of the Ag nanofilm was investigated. A 15-nm Ag nanofilm prevented Cu oxidation prior to the Cu bonding process in air. In the bonding process, Cu diffused rapidly to the bonding interface and pure Cu-Cu bonding occurred. However, some Ag was observed at the bonding interface due to the short bonding time of 30 min in the absence of annealing. The shear strength of the Cu/Ag-Ag/Cu bonding interface was measured to be about 23.27 MPa, with some Ag remaining at the interface. This study demonstrated the good bonding quality of Cu bonding using an Ag nanofilm at 150 °C. [ABSTRACT FROM AUTHOR]

In this article, low-temperature Cu–Cu bonding with the Ag passivation layer was accomplished at 180 °C for 3 min without a postannealing process. The Ag passivation layer effectively prevents Cu from oxidation and assists Cu diffusion to realize low-temperature bonding. The small grain size of the Ag passivation layer controlled by sputtering working pressure is observed to improve bonding quality. Different plasma treatment parameters and bonding conditions were executed to evaluate bonding quality. The diffusion behavior of passivation bonding is investigated, and the corresponding mechanism is discussed as well. In addition, reliability assessments, including thermal cycling, high-temperature storage, and unbiased highly accelerated stress test, indicate excellent stability of this bonding structure, showing the potential for low-temperature bonding technology in 3-D integration applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • This research thoroughly investigates the ultrathin nanoscale bonding structure using area-selective deposition. • The area-selective passivation bonding platform simplifies the complex conventional passivation process. • With the area-selective passivation bonding platform, chips can be bonded at temperatures below 200 ℃. • This research provides a detailed investigation of the bonding mechanism of the area-selective passivation bonding platform. The Cu-Cu bonding technology is an indispensable vehicle for achieving heterogeneous integration, providing architects and designers with a new solution to address the limitations of transistor miniaturization. In this study, a next-generation efficient-process passivation bonding technology has been developed and investigated. The area-selective passivation bonding platform enables chips to be bonded at ambient temperatures below 200 ℃, while mitigating potential patterning issues and simplifying the complex conventional passivation process. The surface exploration of the area-selective films and their bonding mechanism have been thoroughly investigated through the use of transmission electron microscope (TEM) analyses. The results demonstrate exceptional film quality and the bonded reliability of the area-selective films. Furthermore, devices bonded using an optimized process exhibit more reliable mechanical strength than those bonded using conventional passivation methods. [ABSTRACT FROM AUTHOR]

Thermal-compression bonding (TCB) is the key technology to ensure vertical chip (or wafer) stacking in three-dimensional (3D) integration with higher I/O density than conventional soldering technology. For different TCB approaches, copper (Cu) to Cu bonding has always been the preferred candidate due to the excellent electrical and thermal properties of Cu, high mechanical strength of bonding interface, as well as compatibility and cost consideration in the packaging fabrication. However, high thermal budget of the bonding process caused by oxidation of Cu leads to issue of wafer warpage, bonding misalignment, and compatibility with back-end-of-line process. Therefore, this review paper first presents an extensive survey on the advance of low temperature Cu-based bonding technologies. In addition, the feasibility of Cu Cu bonding in the fine pitch applications is challenged by coplanarity issue of Cu pillars and insufficient gaps for filling. Accordingly, based on the progress of low temperature Cu Cu bonding, low temperature Cu/SiO 2 hybrid bonding will be introduced as an emerging bonding technology to solve the coplanarity and filling issue, which can provide the great potential for 3D integration with ultra-high density of interconnection. [ABSTRACT FROM AUTHOR]