Study of low temperature and high heat-resistant fluxless bonding via nanoscale thin film control toward wafer-level multiple chip stacking for 3D LSI

The three dimensional system in package (3D-SiP) has been regarded as a promising solution to the scaling limit problem in the semiconductor industry. Practical realization of the 3D-SiP needs establishing a standard bonding technology for chip stacking. This research focuses on a low temperature and high heat-resistant fluxless bonding method, which can overcome the bump height variation problem in a chip/wafer, using high-boiling alcohol, an indium-tin (InSn) thin film and its transformation into high-melting intermetallic compound (IMC). Experimental studies showed high-rate deposition of InSn alloy and successive deposition of silver achieve successful bonding where the joint has high melting point (higher than 673K).