Biocompatibility assessment of advanced wafer-level based chip encapsulation

Next generation implantable microsystem-based medical devices will have different packaging requirements than current implantable devices such as pace makers. While the packaging must remain biocompatible and provide a bi-directional diffusion barrier, it must also permit the biosensors, microelectrodes, etc to intimately interact with the extracellular environment. A CMOS compatible wafer level packaging strategy for die encapsulation has been developed and tested. TXRF measurements of 3T3 culture medium used in elution testing at physiological temperatures indicate the stack of PECVD diffusion barriers (SiC, SiN, SiO₂) are effective in limiting Cu from leaching from the device. Additionally live-dead cell assays on in vitro co-cultures with both 3T3 fibroblasts and neonatal rat cardiomyocytes demonstrate the effectiveness of the different diffusion barrier stacks in preventing cytotoxic conditions.