Silicon direct bonding for sensor applications: Characterization of the bond quality

Abstract The quality of wafer-to-wafer bonds is investigated with regard to sensor applications. The two-step bonding process is described and experiments with different wafer surfaces are presented. Direct observation of the room-temperature bonding with infrared transmission allows the non-bonding areas to be detected and therefore the bonding process can be optimized. Results obtained for preprocessed silicon wafers with etched grooves or structured surfaces are compared with fullwafer bonding. Samples treated under various annealing conditions have been investigated. Homogeneity and bond strength after thermal and vibrational stress treatments, sealing of bonded interfaces and the analysis of the remaining gas in closed cavities are presented. The results are discussed with regard to sensor applications.