Low-temperature Atomic Layer Deposition (ALD) processes for hermetic encapsulation of medical implants

Since a few decades, the use of electronic devices as medical implants is gaining interest. Pacemakers, Deep Brain Stimulators, cochlear implants,.. they all exists some time already, and they are life-saving or improve greatly the quality of life of the patients. Recently many other future electronic implants are under investigation to help people suffering from a variety of medical issues: implants to stimulate certain areas of the brain or the peripheral nerves, retinal implants for people with vision problems, electronic hip or knee implants, etc.  The trend of miniaturization of electronics is obviously an important advantage for implants, but most electronic implants today are still packaged in a rigid and rather large Titanium case. Such a Titanium case is indeed a biocompatible and hermetic device encapsulation, but a much thinner and flexible encapsulation would offer important improvements since a much more ‘bio-mimetic’ device can be made resulting in less reaction of the body upon implantation. In addition, some novel applications would become realistic, such as miniaturized implants in a very narrow location in the body, where no room is available for a larger and rigid Titanium case.

At the CMST-department of imec in Ghent, we are developing alternative ultrathin and flexible encapsulations based om multistacks of polymers and ‘ALD-layers’. ALD-layers are ceramic layers deposited with extreme accuracy using the atomic layer deposition (ALD) technique. If optimised well, these polymers/ALD multistacks are biocompatible, biostable and they are excellent bi-directional diffusion barriers, hence they are ideal candidates for encapsulations of electronic implantable devices. At imec, we have experience in using polymer/ALD stacks deposited at ‘moderate’ process temperatures (120 °C and higher), but for certain applications lower process temperatures (below 100 °C) offer important advantages. Therefore, novel low temperature ALD processes should be developed, allowing ALD depositions at 80-100° C. Such low temperature ALD-layers are an excellent combination with Parylene,  a biocompatible polymer that can also be deposited at low temperature.

During this PhD study, the student will evaluate the low temperature ALD processes  from a (1) fundamental and (2) application point of view, supported by CMST colleagues: