Microscopic Mechanism of Glass Surface Activation, Annealing and Etching on Glass-Ti/Cu Interfacial Adhesion

Due to its excellent electrical and thermal performance, glass packaging demonstrates significant potential in heterogeneous integration of chiplets advanced packaging system, but limited by its poor interfacial adhesion strength between glass and metals. This article studies the mechanisms of glass-metal bonding interface at the microscale level, and the adhesion strength at the macroscale level. In detail, the changes of the adhesion strength after glass surface activation, annealing and micro-etching processes were characterized, and the correlation between the microscale mechanisms and the macroscale adhesion variations of each process was studied. X-ray photoelectron spectroscopy (XPS) results indicate that the increase in Si-OH bond is the key to glass surface activation. Fourier transform infrared spectroscopy (FTIR) was applied to quantitatively correlate the dynamic evolution of surface polar hydroxyl groups on glass substrates with the subsequent glass-metal interfacial bonding strength, and verified the conclusion above. The adhesion strength increased by 2.3 times after surface activation, and by 4.1 times after annealing, while it decreased slightly after etching. Furthermore, the glass-Ti seed layer interface was studied at the atomic level to better analyze the changes in macroscopic adhesion. XPS depth profiling confirmed the formation of Si-O-Ti bonds at the glass-Ti interface, which may contribute to the enhanced adhesion. After annealing, X-ray diffractometer (XRD) characterization revealed the great change in grain structure caused a reduction in residual stress within the plated layer.