Gas Assisted Focused Electron Beam Induced Deposition
Gas Assisted Focused Electron Beam Induced
Deposition of Thin Films
Another application where NanoMaker can be successfully used
is a controlled deposition of thin film coatings on substrates by decomposing
of metal-organic vapors induced by focused electron beam irradiation (so
called Gas Assisted EBL). Available NanoMaker functionality allows to form
coatings of a given shape and thickness with high spatial resolution in
a specified location on a substrate.
A series of experiments was carried out at the
University of Pennsylvania, USA, in order to assess the ability of the NanoMaker
to provide a direct deposition of gold and platinum films. Deposition was
accomplished on a FEI Quanta 600 FEG microscope equipped with several inlet
nozzles for supplying various metal-organic compounds from single-source
precursors, and including precursors containing gold and platinum. We are
grateful to Dr. L. Rotkina for the given photos.
Fig. 1. Platinum direct deposited film and fine pattern
Fig. 1. and Fig. 1a. show the results of deposition of thin platinum film
on a silicon substrate in a form of trapezoidal pads of different thickness,
as well as fine superscribe and three thin lines of width 30, 20 and 10
nm below it. Picture was taken a few minutes after deposition and closing
of the nozzle.
Fig. 1a. Fragment
of fine pattern with 30, 20 and 10 nm lines
Fig. 2 presents the results of gold film deposition in form of a wedge of
variable thickness in order to determine parameters of the deposition process.
A dose wedge, which is commonly used in electron-beam lithography for experimental
determination of a resist sensitivity, was selected as NanoMaker working
structure. The structure represents a long rectangle, consisting of a set
of narrow adjacent rectangles (total of 101 pieces) of equal area but differing
in exposure time).
Fig. 2. Set of deposited gold wedges
Fig. 2a. The wedge with exfoliated film
Exposure time of rectangles increases linearly from left to
right so that the time of the rightmost rectangle exceeds 10 times the exposure
time of the leftmost rectangle. Series of experiments were performed for
different deposition conditions. The photo clearly shows that the thickness
of the deposited wedges increases from top to bottom one, which affects
the brightness changes in the formed image. And at the very bottom wedge
even exfoliation the film occurred due to stresses encountered. Since the
microscope is not equipped with beam blanker, pillars of the deposited metal
are visible left below each of the structures. These pillars grow at a time
when beam settle in a park position during the exposure. Light haloes around
pillars are result of exposure by backscattered electrons so proximity parameters
can be acquired from the experiments.
Fig. 2b. Fragment of the wedge with exfoliated film