Low-Bow Glass-Si Anodic Wafer Bonding at High Temperature by Means of CTE Engineering of Corning Novel Fusion Glass

In this study, a nearly bow-free anodic bond with high bond strength using SUSS MicroTec manual wafer bonder between Si and SG3.3+ fusion glass from Corning Inc. by means of CTE tailoring of the glass wafer is presented. In BF33 glass wafers used widely in the MEMS industry, due to the CTE mismatch with Si wafer, anodic bond temperature should be kept at < 300°C to minimize the unwanted bonded stack bow after the cool-down step. This could lead to a large decrease in bond strength and even resulting in some unbonded areas. In the new SG3.3+ glass type, owing to its novel manufacturing procedure, further heat-treatment (annealing) of the glass wafer after manufacturing and prior to bonding is possible. This will result in an excellent CTE match between this glass type and that of Si at ideal bonding temperature. Therefore, anodic bonding at high temperature of 350°C will result in a rather bowless bonded stack with very high bond strength. The details of the glass heat-treatment as well as the bonding parameters, CTE and bow values are presented in this paper.