Monte Carlo Modeling of Thin Film Deposition: Factors that Influence 3D Islands Page: 5 of 5
PDF-file: 7 pages; size: 10.6 MbytesView a full description of this article.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
Figure 3. Scanning electron micrographs of Al
sputtered onto Ti substrates: nucleation and
coalescence of islands. (a) Average film thickness
of 140nm, T=400"C, (b) film thickness of 80nm,
T=300 C, (c) film thickness of 140nm, T=200 C. In
(a) the width of the picture is 15 m, and in (b) and
(c) it is 4 m. .
4 ENERGETIC PARTICLE
BOMBARDMENT
The control of energetic ions and neutrals has long
been recognized as an important method to influence the
film structure. Although these particles are in essential part
of sputtering, the kinetic energies of the particles as they
impinge on the substrate can be modified, most
conveniently by controlling the Ar pressure in the
sputtering chamber. The effect of energetic particles on the
shapes of the 3D islands is one mechanism for possible
improvement of film coverage. Re-sputtering of atoms
from the 3D islands causes some reduction of the height to
width ratio, and this effect will favor coalescence.
Our simulations show that the sputtered particles from
an Al target, with a 400eV potential on the target, have
rather low energies and only a small influence on the aspect
ratios of the 3D islands. This is true even at low Ar
pressures, where the mean free path of the sputtered
particles is longer than the target-substrate distance. Higher
energy Ar ions in the range of 50eV, for example, cause
significant flattening of the islands due to the downward
momentum of the ions, and increase the coalescence of
islands. Thus, a facility to accelerate Ar ions toward the
substrate should improve coverage. The energies of
reflected Ar atoms depends on the mass of the target atoms,
and since Al has a smaller mass than Ar, the energies are
low.
An example of sputtering of a target with large atomic
mass is shown in the MC simulations of Ta illustrated in
Fig. 4. A different growth mechanism from island-merger
operates in this system, since the extremely low mobility of
Ta surface atoms does not allow the material to rearrange in
such a way as to form 3D islands. In this case columnat
growth is observed, with low density films and void regions
traversing the film [5].
The influence of the particles coming from the target is
considerable in this case. The density of the film ismcrresed by the re-sputtering events, and the number of
dramatically reduced.
r ' AL(a)
(b)
(c)
Figure 4. MC simulations of sputtered Ta films
at T=30 C (a) Film deposited without energetic
particles. There is some energy imparted to the
impinging Ta atoms due to attractive interatomic
forces, and this amounts to about 6eV/atom. (b)
film formed with Ta atoms with an initial kinetic
energy that averages 10eV. (c) film produced with
both 10eV Ta atoms and 50eV reflected Ar atoms.
The energies for the Ta and Ar atoms were obtained
using TRIM simulations of the 400eV Ar ion
impinging on the Ta target. .
5 CONCLUSION
The MC simulations provide a method to assess
different techniques to improve film quality, and to select
deposition conditions and properties that are likely to have
a significant impact on the films. Our understanding of the
film deposition process is advanced by the ability to mdify
individual parameters or external conditions.
Acknowledgments
Part of this work was performed under the auspices of the
U.S. Department of Energy by the University of California,
Lawrence Livermore National Laboratory under Contract
No. W-7405-Eng-48.
REFERENCES
[1] F. Ercolessi and J. B. Adams, Europhys. Lett. 26,
583, 1994.
[2] R. Stumpf and M. Scheffler, Phys. Rev. B 53, 5958,
1996.
[3] H. Huang, G. H. Gilmer, and T. Diaz de la Rubia, J.
Apple. Phys. 84, 3636, 1998.
[4] F. H. Baumann, D. L. Chopp, T. Diaz de la Rubia,
G. H. Gilmer, J. E. Greene, H. Huang, S. Kodambaka, P.
O'Sullivan, and I. Petrov, MRS Bulletin, March 2001, p.
182.
[5] G. H. Gilmer, H. Huang, T. Dfaz de la Rubia, J.
Dalla Torre and F. H. Baumann, Thin Solid Films 365, 189
2000.
[6] A. Pimpinelli and J. Villain, in: "Physics of Crystal
Growth", (Cambridge, 1998).
Search Inside
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Gilmer, G H; Dalla Torre, J; Baumann, F H & Diaz de la Rubia, T. Monte Carlo Modeling of Thin Film Deposition: Factors that Influence 3D Islands, article, January 4, 2002; Livermore, California. (https://digital.library.unt.edu/ark:/67531/metadc1407354/m1/5/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.