Browse Prior Art Database

Elimination of Excess Material during Focused Ion Beam Induced Deposition

IP.com Disclosure Number: IPCOM000117255D
Original Publication Date: 1996-Jan-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 208K

Publishing Venue

IBM

Related People

Blauner, PG: AUTHOR

Abstract

Focused Ion Beam (FIB) induced deposition is used to directly write thin films with submicron spatial resolution. A significant problem with the technique is that there is a small amount of material deposited in the region surrounding the film. For many applications, this material must be removed by time consuming additional processing. This disclosure describes a method of FIB induced deposition which eliminates the need for this additional processing.

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Elimination of Excess Material during Focused Ion Beam Induced Deposition

      Focused Ion Beam (FIB) induced deposition is used to directly
write thin films with submicron spatial resolution.  A significant
problem with the technique is that there is a small amount of
material deposited in the region surrounding the film.  For many
applications, this material must be removed by time consuming
additional processing.  This disclosure describes a method of FIB
induced deposition which eliminates the need for this additional
processing.

      FIB induced deposition is now used commercially for a large
range of applications (1).  It is widely used in photomask repair

(carbon or chromium deposition to fill in clear defects), x-ray mask
repair (gold, tantalum, or tungsten deposition to fill in clear
defects), circuit repair (to write metal lines to rewire integrated
circuits), test structure fabrication (to create probe pads etc.),
and in failure analysis (as a top coat for cross sections).  In all
of these applications, a precursor gas adsorbs on the sample and the
ion beam is scanned over the area to be written.  The ion beam causes
the gas to decompose only where it has irradiated the surface (2).
Because the ion beam current profile has a long tail which extends
well beyond the nominal beam diameter (3), material is also deposited
in a relatively large area surrounding the intended deposit.  This
peripheral film is a fraction of the thickness of the intended
deposit, but often must be removed.  This requires an extra step
which adds to the complexity and time required for the technique.

      The FIB deposition method disclosed here eliminates the
formation of excess material surrounding the deposit.  In it's
simplest form, the ion beam dose to be delivered is divided up into
many scans across the pattern to be written, each consisting of a
small fraction of the total dose.  By doing so, a very few atoms are
deposited outside the intended area during a single scan.  If large
delays are inserted in between successive scans of the beam, these
atoms will effectively diffuse away before enough of them accumulated
to form critical nuc...