Browse Prior Art Database

Ion Beam-Induced Deposition of Low Resistivity Metal

IP.com Disclosure Number: IPCOM000106762D
Original Publication Date: 1993-Dec-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 4 page(s) / 268K

Publishing Venue

IBM

Related People

Blauner, PG: AUTHOR [+3]

Abstract

Focused Ion Beams (FIB) are now being used in failure analysis and chip repair to cut and rewire metal lines on partially or fully fabricated integrated circuits. In such applications, the FIB is used to open existing wires by sputter etching through them or to create new wires by FIB induced deposition of conducting material.

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Ion Beam-Induced Deposition of Low Resistivity Metal

      Focused Ion Beams  (FIB) are now being used in failure analysis
and chip repair to cut and rewire metal lines on partially or fully
fabricated integrated circuits.  In such applications, the FIB is
used to open existing wires by sputter etching through them or to
create new wires by FIB induced deposition of conducting material.

This "cut and paste" capability provided by a FIB system can be used
to great economic advantage by reducing the turn-around time for
engineering changes during product development.  Since logic changes
on a fully fabricated chip can takes weeks or months to realize, the
ability to implement such a change in less than a day using an FIB
system is extremely valuable.  However, the use of FIB in these
applications is currently limited by the poor conductivity of the
metal lines deposited and the slow speed at which they can be
written.  This invention describes two methods which greatly improve
the conductivity of ion beam deposited metals.  Fig. 1  SEM of a 2
micron wide gold/carbon line FIB deposited by the process disclosed
in [1].  This line (9 microns long) had a resistance of approximately
420 ohms.

      Several commercial systems are available which are designed
specifically for chip repair and failure analyses applications (Seiko
Instruments 8400 series, Micrion 908 and 9000 series, FEI 600 series,
Schlumberger IDS7000).  Although the FIB milling used to cut wiring
functions well in all of these systems, all produce far from ideal
conducting material for rewiring.  The deposition processes used
(tungsten from a tungsten carbonyl precursor or platinum from
(trimethyl)methylcyclopentadienylplatinum) are extremely slow (less
than 5 atoms deposited per incident ion) and produce high resistivity
material (typically 200-500 micro-ohm-cm) due to their large carbon
content.  Although this capability is adequate for some applications,
it is not suitable for many.  Recently there has been disclosed a
process and material which produces deposition rates 10 times greater
(i.e., 50 to 100 deposited atoms per ion) using gold acetylacetonate
as a precursor gas [1,2].  Although this higher deposition rate
greatly increases the speed at which conducting wires can be written,
the films have even higher resistivities (approximately 10,000
micro-ohm-cm).  Fig. 2  SEM of a line similar to that in Fig. 1, but
which has been annealed in air for 425 min at 250º  C.  This line
has a resistance of approximately 1 ohm.

      The first method of lowering the resistivity of FIB deposited
films involves the addition of a final process step.  This final step
consists simply of annealing the deposited film in an oxygen
containing atmosphere for a prescribed period of time.  This anneal
serves to volatilize the carbon in the film and to regrow the metal
into a continuous film with resistivity approaching that of bulk
materials.  Although this process...