Methods for characterization of wafer-level encapsulation applied on silicon to LTCC anodic bonding

This paper presents initial results on generic characterization methods for wafer-level encapsulation. The methods, developed specifically to evaluate anodic bonding of low-temperature cofired ceramics (LTCC) to Si, are generally applicable to wafer-level encapsulation. Different microelectromechanical system (MEMS) structures positioned over the whole wafer provide local information about the bond quality. The structures include (i) resonating cantilevers as pressure sensors for bond hermeticity, (ii) resonating bridges as stress sensors for measuring the stress induced by the bonding and (iii) frames/mesas for pull tests. These MEMS structures have been designed, fabricated and characterized indicating that local information can easily be obtained. Buried electrodes to enable localized bonding have been implemented and their effectiveness is indicated from first results of the novel Si to LTCC anodic bonding.