| This thesis deals with dedicated Microsystems for implanted devices. One goal of Polystim team is to implement an implant to study and stimulate the cerebral cortex. The team has already created a sixteen-microelectrodes array prototype in previous work. Meanwhile, design and realisation of integrated circuits (ICs) are implemented for data recording and transmission.; The objective of the work is to optimize the production process of the electrodes and to conceive a method to integrate the ICs with the electrodes array to create a compact implant. In the first part, the production steps are explored and improved. The second part covers the multichip platform creation for the implant integration.; The electrodes were first machined in a circular rod. This approach is useful for complex section shapes such as hexagonal electrodes. However, an important quantity of steel is lost. To get squared section electrodes, a square bar of BioDur 316 LS stainless steel is cut with electrical discharge machining (EDM). An increasing going up to 48% can be achieved in the efficiency of material use, while reducing the time of machining by 3 minutes per array. Moreover, the protection ring is cut directly in the bar, making the manipulation safer and protecting the electrodes.; The electrochemical steps are reworked to adapt to the modification made in the design and the increase in the number of electrodes. First, the density of the current required for the electropolish is modified to 0.067 mA/cm 2. Then, the acid oxalic attack is performed on the whole structure instead of the tips as is the platinum deposition. This adjustment is made to take into account the increase of electrodes.; To complete the electrodes array, first, epoxy poured on the base and which is then grinded. These two steps are ameliorated by the presence of the protection ring. In the case of epoxy, it creates a tension, which allows a better spread on the base. For the grinding, the ring offers a grip to reduce the preparation steps for the grinding and allows a visual follow up.; The integration steps are initiated after the creation of the arrays, The die-stacking method is chosen to place the ICs in the limited space available in the implant. To give access to the covered electrodes, an interface is created to reroute the contacts to the periphery of the array. Then, the ICs are glued to the base and the contacts are bonded. Finally, the electrodes are covered with Parylen C and the arrays with their ICs are cut.; To create the interface, metallic traces are created on the epoxy base of the array. The lift-off method is used. First, two layers of resists (LOR 5A and S1813) are laid. Then, after exposing and developing the resist, the metal is sprayed by sublimation of with an electrons beam (E-Beam). The final step is to strip the resist and remove the superfluous metal.; To start, the concept of die-stacking is tested on a silicon wafer with the pattern found on the arrays. The ICs are laid on the wafer, and the contacts are connected by wedge bonding. The process couldn't be experimented on the array of electrodes because the epoxy dissipated the ultrasonic vibration. This issue avoided the deformation and adherence of the wire with the contacts.; To complete the implant, the system must be cover with Parylen C while keeping the tips exposed. The tips are casted into glycerine at a depth of 100mum. Then, the whole system is covered with Parylen C. Finally, the arrays are separated from each other with the femtolaser. The laser cut through the epoxy while dissipating minimal energy and having a great precision without deteriorating the material.; Complete implants have been achieved and ready to undergo characterisation and permit to validate the ICs functionality. |
