Effects of surface roughness and oxide layer on wafer bonding strength using transmission laser bonding technique

The reliability of wafer bonding techniques is highly dependent on the surface conditions of the two wafers to be bonded. In this paper, a wafer bonding technique called transmission laser bonding (TLB) focusing on the effects of surface roughness and interface oxidations on the bonding strength. The TLB is implemented for bonding Pyrex glass-to-silicon wafers, both with and without interface oxide layers, utilizing an ns-pulsed Nd:YAG laser. The tensile strengths of the TLB bonded specimens are comparable to existing major wafer bonding techniques. The surface roughness is quantified by atomic force microscopy (AFM). The bonded interfaces are analyzed by x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) to study the bonding mechanism by evaluating the migration and diffusion of different atoms among the glass wafer, silicon substrate, and oxide layer during the bonding process