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FITEP: a Flexible Implantable Thin Electronic Package platform for long term implantation applications, based on polymer and ceramic ALD multilayers

Maaike Op de Beeck (UGent) , Rik Verplancke (UGent) , David Schaubroeck (UGent) , Changzheng Li (UGent) , Dieter Cuypers (UGent) , Maarten Cauwe (UGent) , Bjorn Vandecasteele (UGent) , Lothar Mader (UGent) , Celine Vanhaverbeke (UGent) , John O’Callaghan, et al.
(2019)
Author
Organization
Abstract
Within our internal FITEP technology platform (FITEP: Flexible Implantable Thin Electronic Package), a novel implantable packaging technology is under development in order to realize a very small, flexible, biomimetic package for electronic implants. This new platform enables a radical miniaturization of the final implanted device, which opens many new possibilities for the medical world, since it will be possible to insert electronic sensors in very small locations, such as arteries, nerves, glands,... The device encapsulation consists of a multilayer of biocompatible polymers and ultrathin ceramic diffusion barriers deposited using ALD techniques (ALD: atomic layer deposition) in order to fabricate a very thin and flexible but also highly hermetic device packaging. Concerning the selection of biocompatible polymers, polyimide can offer a profound mechanical support for the various device components, while Parylene with its excellent step coverage creates a highly conformal coating surrounding all components. Hermeticity can be realized by the use of ultrathin ceramic ALD layers such as Al2O3 and HfO2. An optimized ALD process will result in layers from very high quality with very good step coverage. As such, selected ALD layers of only a few tens of nm thick, can exhibit very low Water Vapor Transmission Rates (WVTR), making these ALD materials ideal as ultrathin diffusion barriers. The tested polyimide/ALD stack proved to be a very hermetic enclosure: copper patterns protected with the polyimide/ALD stack are still in perfect condition after more than 2 years of immersion in saline at 60 °C (test is still ongoing), while Cu patterns protected by the polyimide stack without ALD barriers showed first signs of damage already after 6 weeks exposure to saline. Platinum and gold are best suited for metallization of implanted electronics, but these noble metals do not adhere easily to polymers, hence dedicated measures to promote metal-polymer adhesion are essential. The FITEP platform is applied on a Si-probe for implantation in the peripheral nerves, consisting of a CMOS chip with recording and stimulation electrodes [Op de Beeck, M. 2017]. The chip is thinned down to 35um and packaged using polyimide and ALD multi-stacks, resulting in a 75um thin fully encapsulated chip, optimized to reduce the Foreign Body Reaction to obtain optimum electrode-nerve contact. Flexible interconnects are fabricated using gold and platinum sandwiched between polymers and ALD layers. For optimal charge injection, iridium oxide is used as electrode material. After this hermetic FITEP-based chip encapsulation, the CMOS chip is still fully functional, which was tested dry (in air) as well as during submersion in saline. First acute in vivo stimulation tests have shown good electrode stimulation capabilities. Mechanical bending tests on long 5um thick gold interconnects are performed, showing that even after up to 1.5 million bending cycles, no cracks occurred in the gold patterns (testing in air). Longer term immersion in saline and in-vivo testing showed some problems related to loss of adhesion and to galvanic effects of the metallization. These observations were leading to some improvements in the fabrication of the encapsulation. In a second packaging iteration of the CMOS chip, these improvements were realized and a new series of encapsulated devices is fabricated. First results are promising, showing improved metal adhesion. Longer term stability tests are on its way.
Keywords
miniaturized implantable chip package, hermeticity, flexible device encapsulation

Citation

Please use this url to cite or link to this publication:

MLA
Op de Beeck, Maaike et al. “FITEP: a Flexible Implantable Thin Electronic Package Platform for Long Term Implantation Applications, Based on Polymer and Ceramic ALD Multilayers.” 2019. Print.
APA
Op de Beeck, Maaike, Verplancke, R., Schaubroeck, D., Li, C., Cuypers, D., Cauwe, M., Vandecasteele, B., et al. (2019). FITEP: a Flexible Implantable Thin Electronic Package platform for long term implantation applications, based on polymer and ceramic ALD multilayers. Presented at the 2019 Advanced Technology Workshop on Advanced Packaging for Medical Microelectronics.
Chicago author-date
Op de Beeck, Maaike, Rik Verplancke, David Schaubroeck, Changzheng Li, Dieter Cuypers, Maarten Cauwe, Bjorn Vandecasteele, et al. 2019. “FITEP: a Flexible Implantable Thin Electronic Package Platform for Long Term Implantation Applications, Based on Polymer and Ceramic ALD Multilayers.” In .
Chicago author-date (all authors)
Op de Beeck, Maaike, Rik Verplancke, David Schaubroeck, Changzheng Li, Dieter Cuypers, Maarten Cauwe, Bjorn Vandecasteele, Lothar Mader, Celine Vanhaverbeke, John O’Callaghan, Dries Braeken, Alexandru Andrei, Andrea Firrincieli, Marco Ballini, Aritra  Kundu, Ahmed Fahmy, Erin Patrick, Nima Maghari, Rizwan Bashirullah, and Johan De Baets. 2019. “FITEP: a Flexible Implantable Thin Electronic Package Platform for Long Term Implantation Applications, Based on Polymer and Ceramic ALD Multilayers.” In .
Vancouver
1.
Op de Beeck M, Verplancke R, Schaubroeck D, Li C, Cuypers D, Cauwe M, et al. FITEP: a Flexible Implantable Thin Electronic Package platform for long term implantation applications, based on polymer and ceramic ALD multilayers. 2019.
IEEE
[1]
M. Op de Beeck et al., “FITEP: a Flexible Implantable Thin Electronic Package platform for long term implantation applications, based on polymer and ceramic ALD multilayers,” presented at the 2019 Advanced Technology Workshop on Advanced Packaging for Medical Microelectronics, San Diego, California, 2019.
@inproceedings{8628164,
  abstract     = {Within our internal FITEP technology platform (FITEP: Flexible Implantable Thin Electronic Package), a novel implantable packaging technology is under development in order to realize a very small, flexible, biomimetic package for electronic implants. This new platform enables a radical miniaturization of the final implanted device, which opens many new possibilities for the medical world, since it will be possible to insert electronic sensors in very small locations, such as arteries, nerves, glands,... The device encapsulation consists of a multilayer of biocompatible polymers and ultrathin ceramic diffusion barriers deposited using ALD techniques (ALD: atomic layer deposition) in order to fabricate a very thin and flexible but also highly hermetic device packaging. Concerning the selection of biocompatible polymers, polyimide can offer a profound mechanical support for the various device components, while Parylene with its excellent step coverage creates a highly conformal coating surrounding all components. Hermeticity can be realized by the use of ultrathin ceramic ALD layers such as Al2O3 and HfO2. An optimized ALD process will result in layers from very high quality with very good step coverage. As such, selected ALD layers of only a few tens of nm thick, can exhibit very low Water Vapor Transmission Rates (WVTR), making these ALD materials ideal as ultrathin diffusion barriers. The tested polyimide/ALD stack proved to be a very hermetic enclosure: copper patterns protected with the polyimide/ALD stack are still in perfect condition after more than 2 years of immersion in saline at 60 °C (test is still ongoing), while Cu patterns protected by the polyimide stack without ALD barriers showed first signs of damage already after 6 weeks exposure to saline. Platinum and gold are best suited for metallization of implanted electronics, but these noble metals do not adhere easily to polymers, hence dedicated measures to promote metal-polymer adhesion are essential. The FITEP platform is applied on a Si-probe for implantation in the peripheral nerves, consisting of a CMOS chip with recording and stimulation electrodes [Op de Beeck, M. 2017]. The chip is thinned down to 35um and packaged using polyimide and ALD multi-stacks, resulting in a 75um thin fully encapsulated chip, optimized to reduce the Foreign Body Reaction to obtain optimum electrode-nerve contact. Flexible interconnects are fabricated using gold and platinum sandwiched between polymers and ALD layers. For optimal charge injection, iridium oxide is used as electrode material. After this hermetic FITEP-based chip encapsulation, the CMOS chip is still fully functional, which was tested dry (in air) as well as during submersion in saline. First acute in vivo stimulation tests have shown good electrode stimulation capabilities. Mechanical bending tests on long 5um thick gold interconnects are performed, showing that even after up to 1.5 million bending cycles, no cracks occurred in the gold patterns (testing in air). Longer term immersion in saline and in-vivo testing showed some problems related to loss of adhesion and to galvanic effects of the metallization. These observations were leading to some improvements in the fabrication of the encapsulation. In a second packaging iteration of the CMOS chip, these improvements were realized and a new series of encapsulated devices is fabricated. First results are promising, showing improved metal adhesion. Longer term stability tests are on its way.},
  author       = {Op de Beeck, Maaike and Verplancke, Rik and Schaubroeck, David and Li, Changzheng and Cuypers, Dieter and Cauwe, Maarten and Vandecasteele, Bjorn and Mader, Lothar and Vanhaverbeke, Celine and O’Callaghan, John  and Braeken, Dries  and Andrei, Alexandru  and Firrincieli, Andrea  and Ballini, Marco  and Kundu, Aritra   and Fahmy, Ahmed  and Patrick, Erin and Maghari, Nima and Bashirullah, Rizwan  and De Baets, Johan},
  keywords     = {miniaturized implantable chip package,hermeticity,flexible device encapsulation},
  language     = {eng},
  location     = {San Diego, California},
  title        = {FITEP: a Flexible Implantable Thin Electronic Package platform for long term implantation applications, based on polymer and ceramic ALD multilayers},
  url          = {http://www.imaps.org/abstracts/system/new/abstract_preview.asp?abstract=2019medical008},
  year         = {2019},
}