Strengthening mechanisms and residual stress control in Pt and Au
P. Vinci, Seungmin Hyun, Richard Chromik, Ming-Tzer Lin, Terry
Delph, Walter Brown
Collaborators: Stanford University, Applied Materials, Inc., and
the US Army Research Laboratory
- Platinum and gold electrodes are often used in circumstances that
require high oxidation resistance. Platinum is particularly suited for
high temperature applications.
- One such application is platinum integrated with
high permittivity ceramic materials for capacitive storage devices such
as the DRAMs (Dynamic Random Access Memory chips), and for
piezoelectric actuators (with PZT - Lead Zirconium Titanate). The
processing conditions for the complex oxides typically involve elevated
temperatures and oxidizing conditions. Electrical leakage should be low
for low-term stability (reduced "memory" loss). Unfortunately, platinum
electrodes are susceptible to adhesion problems, hillock growth, and
high residual stresses, all of which are detrimental to electrode
performance and lifetime. These problems are ultimately related to the
mechanical behavior of the platinum films. Understanding and
controlling the mechanical properties of the metal films will allow
improvements in electrode behavior.
- Gold is highly susceptible to creep and stress relaxation,
even at moderately high temperatures. Methods for fabricating
creep-resistant gold electrodes are needed. This requires an
understanding of the deformation mechanisms acting in thin gold films.
an on-chip capacitor.
stress behavior of Pt on
- Develop new alloy systems to improve the performance and
reliability of metal electrodes integrated with high-K capacitor
- Gain understanding of plasticity mechanisms and strengthening
effects in this films at a variety of temperatures.
- A model for stress relaxation in Pt thin films has been
developed. It explains the role of grain structure and film thickness
in determining relaxation rate.
- A method for creating low-residual stress Pt metallization has
been developed. It is currently not suited for mass production, but
further development is under way.
- Solid solution strengthening effects were evaluated in Pt-Ru
alloys. It was found that the effect could be described by a bulk
strengthening theory, but that the grain size refinement associated
with the addition of the Ru solute dominated the total strengthening.
- Reduction in stress relaxation rate and extent in Au was
demonstrated at 200 and 400 C by alloying with V.
- S. Hyun, R. P. Vinci, K.P. Fahey, B.M. Clemens, Effect of grain
structure on the onset of diffusion-controlled relaxation in Pt thin
films, Appl. Phys. Lett., 83 (14), 2003, pp. 2769-71.
- S. Hyun, O. Kraft, and R.P. Vinci, Solid solution alloy effects
on microstructure and indentation hardness in Pt-Ru thin films, Mater.
Res. Soc. Proc., 673, 2001, pp. P3.2.1-P3.2.6.
- S. Hyun, O. Kraft, and R.P. Vinci, Mechanical behavior of Pt and
Pt-Ru solid solution alloy thin films, Acta Mat., 52(14), 2004, pp
- R.R. Chromik, T. Bannuru, and R.P. Vinci, Internal oxidation and
mechanical properties of Pt-IrO2 thin films, Proc. Mater. Res. Soc.
Symp., 2004, U8.13.1-6.
This is work has been supported by:
The views and
conclusions contained in this document are those of the authors and
should not be interpreted as representing the official policies, either
expressed or implied, of the Army Research Office, Army Research
Laboratory, or the U.S. Government.
- the National Science Foundation,
grant number DMR-0072134, Subcontract No. PY-0826
- the U.S. Army Research Office
and U.S. Army Research Laboratory,
Cooperative Agreement Number DAAD19-02-2-0030.
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Last updated: August 2, 2005