Online proceedings - EDA Publishing Association

11-13
May 2011, Aix-en-Provence, France
Diamond-based technology dedicated to Micro
Electrode Arrays for Neuronal Prostheses
A. Bongrain 1 , A. Bendali 2 , G. Lissorgues 3 , Lionel Rousseau 3 , B. Yvert 4 , E. Scorsone 1 , P.Bergonzo 1 , S. Picaud 2
1 CEA, LIST, Diamond Sensor Laboratory, CEA/Saclay, Gif-sur-Yvette, France
2 Institut de la Vision, INSERM UMRS-968, UPMC, Paris, France
3 ESYCOM - ESIEE, University Paris-Est, 93162, Noisy le grand, France, lissorgg@esiee.fr
4 INCIA, University Bordeaux, France
I. INTRODUCTION
Recent advances in nanotechnology have opened new routes
for the fabrication of MicroElectrode Arrays (MEAs), offering
an elegant way to probe the neuronal activity distributed over
large populations of neurons either in vitro or in vivo.
Specific electrical stimulations can be delivered to neuronal
networks when using MEAs as stimulating electrodes.
Conversely, MEAs can provide a mean to record the activity
of many cells simultaneously over large neuronal networks [1
- 4]. These MEAs now are an increasingly common approach
for neurologic pathologies treatment strategies[5, 6]: they can
be used to build neural prostheses to balance function losses
due to lesions or degeneration of part of the Central Nervous
System (CNS) such as for Parkinson disease treatment, or for
cochlear or retinal implants.
The contact to the cells for such MEAs commonly uses gold,
platinum, black platinum or iridium oxide as the electrode
materials. Any non-optimal contact can induce reactive gliosis
(Muller cells) in the vicinity of the micro electrodes producing
an insulating surface between the MEA and the neuron.
This paper describes an alternative approach based on the use
of a non conventional material, namely Boron Doped
Diamond (B-NCD), to fabricate different kind of MEAs.
Indeed diamond is now considered as a promising material for
micromechanical or microelectronics device applications [7].
The challenge is then to build new electrodes that exhibit both
a high potential window with respect to water electrolysis, and
possess a high electrode reactivity which is important to obtain
high signal to noise ratios. We show that B-NCD, as fabricated
using nano-processing coupled with chemical vapour
deposition (CVD), leads to semiconducting electrode
properties with bio-inert capabilities adapted to efficient
neuronal stimulation and recording.
This paper is divided into three parts. We first present the
specific technology developed to fabricate diamond based
MEA, then second the fabrication of the MEAs and some
characterisation results. We finish introducing an application
of such MEAs to retinal implants.
II.
DIAMOND BASED TECHNOLOGY
We developed a novel technology enabling the fabrication of
diamond based microelectrode arrays either on silicon, glass
or soft substrates.
Today, the Microwave Plasma Chemical Vapour Deposition
(MPCVD) technique allows the growth of polycrystalline
diamond films over large areas (2 to 4 inches on a variety of
substrate materials, including silicon) but the innovation
remains to accurately pattern the diamond layers to define in
our case the electrodes of the MEAs. Various approaches to
pattern diamond layers have been investigated, the most
common approach being selective etching in oxygen/argon [8]
or oxygen/CF 4 [9, 10] plasma. However, the chemical
resilience of diamond renders the etching step time consuming
and often unsuitable for mass production. Another technique
relies on the patterning of a diamond nano powder layer from
which the diamond film is selectively grown [11].
As we are using Boron Doped Nanocrystalline Diamond
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