POLYIMIDE-ALD-POLYIMIDE LAYERS AS HERMETIC ENCAPSULANT FOR IMPLANTS

Several requirements exist for medical devices for long term implantation. Firstly, the foreign body reaction and/or inflammation occurring upon implantation should remain mild and short in time. Moreover, the device needs to be biocompatible during the total implantation duration, hence not causing reactions which decrease the patient's health. Finally, the device needs to work properly and safe during the total period of implantation, not suffering from corrosion or chemical degradation. To meet these requirements, diffusion of body fluids into the package should be avoided as well as diffusion of toxic device materials into the body, hence a hermetic packaging method is an absolute necessity. Here, a flexible hermetic packaging is presented using alternating polyimide and atomic layer deposited (ALD) metal oxides. Good adhesion between the inorganic ALD layers and the polyimide is required to avoid the creation of lateral diffusion pads. To obtain this, surface modifications of both polyimide and ALD layers are optimized, as presented in this paper. The hermeticity is evaluated in terms of water vapor transmission rate measurements of the film stack.

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