Glass-Silicon Hermetic Micro Packages for Implantable Biomedical Microsystems

摘要

This paper reports on micromachined glass-silicon packages and long-term accelerated test results in aqueous solutions. Using the accelerated data at 85 and 95 deg C in saline with an Arrhenius model we calculate an activation energy of 1.26eV and an expected lifetime of 177 years at 37 deg C in saline. After an analysis of the failed samples, we find that the main failure mechanism is the dissolution of the polysilicon layer at elevated temperatures in saline, which causes premature failure of the package. The average tensile strength of 5.9 MPa is obtained for the package. The glass-silicon package is IC compatible, batch producible and provides hermetic feedthroughs. Integration with sensors or circuits can be achieved with extra masking steps. The package is found to be biocompatible after animal tests for periods of up to a year.