Microstructural characterization of the Si/Cu/X/Cu/Si (X=In, In-48 at.% Sn) interconnections obtained in diffusion soldering process
The paper presents the potential of diffusion soldering process application to the production of thermally stable Si/Si joints designed for microelectronics devices. Pure copper was used for metallization while In and an In-48 at.% Sn alloy as solder interlayers (Fig. 1). The samples were annealed at 180 °C and 200 °C for In and the In-Sn interlayer, respectively. The investigation of interconnections was performed using transmission electron microscope equipped with an energy-dispersive X-ray spectrometer. The presence of two phases: eta(Cu2In) and ...(Cu7ln3) in the Cu/In/Cu joint was found (Fig. 2). The eta phase was also observed in the Cu/Sn-In/Cu samples. However, in the central part of the joint it was based on the Cu6(Sn,In)5 compound and with an increasing distance from the middle of the joint this phase was replaced by eta(Cu2(In,Sn)). In the region adjacent to the copper substrate two phases: ...(Cu10(Sn,In)3) and ...(Cu7In3) were detected (Fig. 3). The high melting point (~600 °C) of all the phases (eta, ...) guarantees the thermal stability of the resulting interconnections (Figs.4, 5).