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Page 68
November 13-14, 2017 Paris, France
5th International Conference on
PLASMA CHEMISTRY AND
PLASMA PROCESSING
Journal of Biotechnology and Phytochemistry
Volume 1, Issue 2 Plasma Chemistry 2017
Dry cleaning of polymeric residues from
graphene with high density hydrogen plasma:
the issue of plasma purity
Hasan-al Mehedi
1LTM/CNRS, France
2Leti-Minatec, France
3CEA Centre de Grenoble, France
Graphene consists of two exposed sp2-hybridized
carbon surfaces and has no bulk. Therefore, graphene
surface contamination by adsorbed polymer residues have
a critical influence on its electrical properties and can
drastically hamper its widespread use in device fabrication.
Therefore, graphene-based technology requires “soft” and
selective surface cleaning process to suppress this surface
contamination. However, polymeric contamination is
resistant to cleaning due to p-stacking and is problematic
because it originates from typical technological processes
used to fabricate graphene devices. Since solvents are not
efficient to clean these residues, other strategies based on
reactive plasmas have been proposed. Here, we investigated
a high density H2 plasma cleaning process of graphene
monolayer in an industrial ICP plasma reactor designed to
etch 300mm diameter wafers. Firstly, we show that there is a
considerable issue associated with the use of H2 plasmas to
treat graphene and other 2Dmaterials: H atoms and H3+ ions
reduce the surface of all the materials exposed to the plasma,
which include the reactor walls and the substrate holder (i.e.
the 300-mm diameter wafer on which the graphene sample
is stuck). As a result, metallic and O atoms are released in
the H2 plasma, resulting respectively in graphene metallic
contamination and damages, Si stick on graphene while O
atoms etch it investigated various coating of
the reactor walls to prevent this phenomenon. We concluded
that the only solution to get rid of parasitic O is to use a wafer
holder made of Aluminum and to fully fluorinated the reactor
walls and the wafer with a F rich plasma prior the H2 process.
Under such controlled conditions, we show that H2 plasmas
can provide an infinite etching selectivity between sp2 and
sp3 hybridized form of carbon, i.e. H2 plasma can clean
polymer residues from graphene. The quality of the cleaning
is characterized by various surface diagnostic techniques,
including k-PEEM to measure its band structure. We show
that the cleaned graphene lattice remains undamaged by H2
high density ICP plasma. This dry-cleaning has the advantage
to be an industrially mature technology adapted to large area
substrates and to other 2D materials.
J Biot Phyt 2017