Implantable device including a MEMS accelerometer and an ASIC chip encapsulated in a hermetic silicon box for measurement of cardiac physiological parameter

The objective of this paper is to present a new technology that integrates a Micro Electro-Mechanical Systems (MEMS) accelerometer and an Application-Specific Integrated Circuit (ASIC) chip encapsulated in a hermetic silicon box that could be embedded in a transvenous cardiac lead in order to sense the endocardial acceleration signal. The originality of the approach consists of using an interposer and a lid, both made of conductive doped silicon to connect the device. The MEMS and the ASIC are attached on the silicon interposer and the silicon lid is bonded using eutectic AuSi ring. The electrical interconnection to the two conductor wires is obtained through the interposer and the lid using the conductivity of doped silicon. The system integration was performed at the wafer level. A test vehicle which allows characterizing the required technologies was designed and manufactured. A technical focus on the most important process steps for the integration is presented and discussed in this paper. This includes interconnection on doped silicon, dies on wafer bonding and wafer to wafer bonding. The hermeticity and biocompatibility encapsulation of the device is also addressed and a prototype which has been designed is described.