Integrated 3D-Capacitors for Implantable Bradycardia Pacemakers: Dielectric Integrity and Local Electrical Characterizations using AFM
Résumé
A silicon 3D-array capacitor dedicated for an implantable bradycardia pacemaker is presented. The integrated 3D-shape of the capacitors are designed by fabricating a high ratio micropore array inside the silicon wafer. This special shape enhances the developed surface of the dielectric layer, leading to high capacitance densities, critical for the application in such a biomedical system. The process control, based on nano-characterizations performed on an Atomic Force Microscopy, is deployed for the three major critical fabrication steps: the dielectric conformity, the in-situ phosphorus-doped polycrystalline silicon pore filling and the uniformity of the doping of the electrodes of the SIS capacitor. After the chemical revelation of the deposited dielectric layer, the conformity of the layer and the effectiveness of the filling are proven by AFM topographies. Moreover, the delineation of the electrode doping is examined with the electrical Scanning Capacitance Mode by recording the spatial extension and the carrier concentration. Macroscopic characterisations of the dielectric properties show the stability of the 3D-patterning silicon capacitors concerning the applied voltage and the temperature. Finally, a high integration solution, where the 3D-capacitor are embedded and sandwiched into a multilayer printed circuit board, is exposed by employing thin epoxy laminates prepreg sheets.