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TECHNICAL
PUBLICATIONS
Synthesis Route to Garnet
and Perovskite Thin Films via Quad-Reactive
Co-Sputter Deposition of Amorphous Non-Equilibrium
Alloy Oxides and Subsequent Annealing
Abstract - The
low temperature reactive sputter deposition of
amorphous rare earth substituted Bismuth Iron
Garnet (BiDy)3(FeAl)5O12 using four simultaneous
targets via a biased target deposition (BTD)
system is reported for the first time. This method
provides control over the material composition in
a predictable way by controlling the individual
target bias. The resultant films deposited on
fused quartz substrates are highly uniform and on
post annealing form high quality poly-crystalline
garnet films.(click here for PDF)
Progress on Gallium Nitride
Semiconductor Growth by Plasma
Sputtering
Abstract - Plasma
sputtering based growth of Gallium Nitride (GaN)
is explored as a scalable and cost-effective
method for obtaining thin crystalline III-V
nitride films. Structural and optical
characterization of the first series of growths on
sapphire substrates indicates the growth of GaN,
albeit with poor structural and optical
properties. (click here for PDF)
Biased Target Ion Beam
Deposition of GMR Multiayers
Abstract
- Multilayers like those used in giant
magnetoresistive spin-valves can be improved if
better layer thickness uniformity, lower
contamination levels, reduced interfacial
roughness and less interlayer mixing can be
achieved. Atomistic simulations have revealed that
optimization of the energy of the depositing atoms
and the application of very low energy inert gas
ion assistance reduce both interfacial roughness
and interlayer mixing. Modulation of the energy of
these fluxes as each layer growth progresses has
been predicted to give even better quality
interfaces. Unfortunately, these concepts cannot
be implemented in conventional physical vapor
deposition (PVD) or ion beam deposition (IBD)
processes used to deposit these materials. A new
biased target ion beam deposition (BTIBD) system
that enables these conditions to be achieved has
recently been developed. Unlike conventional IBD,
it uses a low energy ion source. The higher ion
energy required for the sputtering is obtained by
applying a negative bias voltage to the metal
targets. This system enables low energy ion
assistance at the growth surface. By modulating
the bias voltage during each layer growth, it is
also possible to change the average energy of the
depositing atoms and therefore enable control of
the atomic assembly at interfaces. We have used
BTIBD to grow model Ta (40 Å)/Ni80Fe20 (40 Å)/Co
(15 Å)/Cu (tCu)/Co (45 Å)/FeMn (100 Å)/Cu (20 Å)
spin-valves that show improved GMR ratios and
coupling fields over traditional IBD grown
multilayers. (click here for PDF)
Biased Target Ion Beam
Deposition of Spin-valves
Abstract
- A further reduction of defect concentration
in spin-valve multilayers is difficult in today’s
growth processes. Multilayers with better layer
thickness uniformity, lower contamination and
reduced interfacial roughness and interlayer
mixing can have significantly improved properties.
Atomistic simulations revealed that a modulation
of the energy of depositing atoms during
deposition of each material layer or the
application of very low energy inert gas ion
assistance could reduce both interfacial roughness
and interlayer mixing. These concepts,
unfortunately, cannot be implemented in the
conventional physical vapor deposition (PVD) or
ion beam deposition (IBD) processes currently used
to deposit these materials. A new biased target
ion beam deposition (BTIBD) system that enables
these conditions to be achieved has recently been
developed. Unlike the conventional IBD, it uses
low energy ion source. The high ion energy
required for the sputtering is obtained by
applying a negative bias voltage to the metal
target. This system enables the low energy ion
assistance at the growth surface. By modulating
the bias voltage during each layer growth, it is
also possible to change the average energy of the
depositing atoms and therefore enables control of
the atomic assembly at interfaces. We have used
this approach to grow Ta (40 Å)/Ni80Fe20 (40 Å)/Co
(15 Å)/Cu (tCu)/Co (45 Å)/FeMn (100 Å)/Cu (20 Å)
spin-valves and show improved GMR ratio and
coupling field over traditional IBD grown
multilayers. (click here for PDF)
Low Energy Ion
Beam Etching
James R. Kahn and Harold
R. Kaufman
Abstract
- Etch-rate profiles have been obtained for
copper, tantalum, stainless steel and quartz using
a commercial end-Hall ion source. These profiles
can be used to predict uniformity and etch rates
in practical etching configurations. Compared to a
gridded ion source, the lower ion energy of an
end-Hall ion source is offset in etching rate by
its large ion-current capacity, while the lower
ion energy can be a significant advantage in
damage-sensitive etching applications. (click here for PDF)
Broad-Beam
Industrial Ion Sources
Staff of
Kaufman & Robinson,
Inc.
Introduction - A broad
ion beam is typically several centimeters or more
in diameter. The beam diameter is also much larger
than the Debye length, which is the typical
distance an electric field can penetrate into a
plasma. If a broad beam is to be kept near ground
potential, it must be neutralized (see Tech. Note
KRI-02). For neutralization, there must be
approximately equal numbers of electrons and
positively charged ions in each volume of the ion
beam. For a dielectric target, the electrons and
ions must arrive in equal numbers. The target can
be either a sputter target or a substrate. The ion
energy in a broad ion beam is 2000 eV or less. (A
singly charged ion “falling” through a potential
difference of 2000 V acquires an energy of 2000
eV.) To minimize damage, the energy is usually
1000 eV or less. High energy implanting-type
applications are not consider-ed here. Concern
about damage to processed surfaces has led to
decreased ion energies. There are two general
categories of broad-beam ion sources: gridded and
gridless. (click here
for PDF)
Ion-Beam
Neutralization
Staff of Kaufman &
Robinson, Inc.
Introduction
- As described in Technical Note KRI-01, an
ion beam from a broad-beam industrial source must
be neutralized. This is done by emitting electrons
from a neutralizer. A hot-filament, plasma-bridge,
or hollow-cathode type of neutralizer may be used.
The ion source in Fig. 1 could be either gridded
or gridless. For a gridless source, the
neutralizer is a called a cathode-neutralizer. The
target can be a sputter target or a substrate
being etched. (click
here for PDF)
Gas
Cleanliness
Staff of Kaufman &
Robinson, Inc.
Introduction
- Gas cleanliness is important to some
vacuum-process equipment and processes. For
example, contamination can decrease the lifetime
of hollow cathodes and plasma-bridge neutralizers
by a factor of ten or more. The techniques
required to assure gas cleanliness are reviewed
herein. (click here
for PDF)
Ion-Assist
Doses
Staff of Kaufman & Robinson,
Inc.
Introduction - Ion
assisted deposition has evolved from a collection
of individual “recipes,” to the use of ion energy
per deposited atom as a measure of this dose,[1,2]
to the variation of this dose with material
melting temperature.[3] The energy range of
interest for most applications has narrowed,
focusing at present on the low-energy range from
about 25 eV to about 100 eV.[3] Dense, low-defect
films are believed to be generated in this range
by lattice vibrations. Ion collision effects tend
to be confined to the surface below ~25 eV, while
damage is introduced into the film by the
excessive penetration of ions above ~100 eV. (click here for PDF)
In-Situ
Cleaning for Thin-Film
Deposition
Staff of Kaufman &
Robinson, Inc.
Introduction
- Thin films are deposited on substrates in a
variety of vacuum deposition processes. The
properties of such a deposited film depends on the
cleanliness of the substrate surface on which the
film is deposited. Contamination on this surface
can result in reduced adhesion of the film to the
substrate, more rapid degradation of the film
after deposition, greater contact resistance for
electrically conducting films, and poor optical
qualities for optical films. (click here for PDF)
Modular Linear Ion
Sources
H.R. Kaufman, J.R. Kahn, and
R.E. Nethery
Abstract - The
modular linear ion source described herein uses
cylindrical end-Hall modules in a linear array.
The modules are operated in parallel so that there
is a single gas flow to the ion source, a single
discharge power supply, and a single
hollow-cathode electron source, similar to a
non-modular design. The spacing between the
modules can be varied to obtain a wide range of
operating characteristics while keeping a high
degree of ion-dose uniformity along the length.
The ion beam is fully neutralized to provide
stable operation that is not dependent on
workpiece material.(click
here for
PDF) |
