Browse Prior Art Database

High Resolution Focused Ion Beam Induced Deposition

IP.com Disclosure Number: IPCOM000117190D
Original Publication Date: 1996-Jan-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 8 page(s) / 365K

Publishing Venue

IBM

Related People

Blauner, PG: AUTHOR [+2]

Abstract

Focused ion beam induced deposition of metals is used to repair lithographic masks by replacing missing absorber material. The resolution with which one can accomplish this so-called clear repair process is limited by the resolution of the beam induced deposition process itself. To date, the best resolution demonstrated has been approximately 0.15 um (1). The highest resolution masks currently fabricated are the 1-to-1 masks used in proximity x-ray printing. These masks are now being manufactured with critical dimensions down to 0.25 um. It is anticipated that dimensions reaching to 0.1 um will be required within the next decade. It is clear that significant improvements to the clear repair process will be required in order to repair masks at these dimensions.

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High Resolution Focused Ion Beam Induced Deposition

      Focused ion beam induced deposition of metals is used to repair
lithographic masks by replacing missing absorber material.  The
resolution with which one can accomplish this so-called clear repair
process is limited by the resolution of the beam induced deposition
process itself.  To date, the best resolution demonstrated has been
approximately 0.15 um (1).  The highest resolution masks currently
fabricated are the 1-to-1 masks used in proximity x-ray printing.
These masks are now being manufactured with critical dimensions down
to 0.25 um.  It is anticipated that dimensions reaching to 0.1 um
will be required within the next decade.  It is clear that
significant improvements to the clear repair process will be required
in order to repair masks at these dimensions.

      This invention describes a means of improving the resolution of
ion beam induced deposition processes by careful choice of the
incident ion's energy and mass.  It is generally accepted in the
field that improved resolution in FIB processes is achieved by
increasing the ion beam energy and/or decreasing the ion beam mass
(2).  In the case of focused ion beam induced deposition, the
opposite is true.  By lowering the ion energy and/or increasing the
ion mass the lateral straggle of the ion beam is decreased and a
higher resolution deposit is achieved.  The effectiveness of this
invention has been demonstrated for the focused ion beam induced gold
deposition process currently used for X-ray mask repair (1), but it
is clearly extendable to other deposition processes used in high
resolution patterning.

      Ion beam induced deposition is a process by which an energetic
beam of ions are used to decompose precursor molecules adsorbed on a
surface thereby building up a deposit in the irradiated region
(1,2,3,4).  Because material deposition occurs only in the region
irradiated by the beam, this process provides a means of depositing
material in a highly localized manner.  Its usefulness has been
demonstrated in applications such as lithographic mask repair,
integrated circuit repair and prototyping, and fabrication of novel
force microscopy tips.  However, it has been observed that the
resolution of high aspect ratio (feature height / feature width)
features written by this process is significantly worse than the
resolution of the ion beam used to write the features.  For example,
a 60 nm focused 100 keV Ga beam used in X-ray mask repair can deposit
features down to only 0.15 um (1).

      By varying the incident ion energy and mass, we have recently
demonstrated that the resolution of focused ion beam induced gold
deposits correlates with the lateral straggle (or spread) of the ions
in the deposit.  Using a mass separated 100 keV focused ion beam
column, gold features were deposited using 100 keV Au+, 100 keV Ga+,
and 200 keV Si++.  The diameters of these beams are estimated to vary
by less...