The Evolution of Ion-Beam
Diamond-like-Carbon Technology
into Data Storage: Space Propulsion,
Sunglasses, Sliders, and now Disks
F RED M. K IMOCK , D AVID W. B ROWN , S TEVEN J. F INKE & E DWARD G. T HEAR , Diamonex, Inc., Allentown, PA, USA
ABSTRACT
TABLE 1.
P ROPERTIES
road-ion-beam technology is now well established in the data storage industry for processes
such as ion milling, reactive ion etching, and
deposition. Ion-beam deposition is a proven method for
the production of protective diamond-like-carbon
coatings in a variety of commercial applications ranging
from optics, such as sunglass lenses and laser bar-code
scanner windows, to sliders and is now being implemented for magnetic disks. Each of these applications
relies on the control of material properties, repeatability, uniformity, and cost-effectiveness afforded by the
ion-beam deposition process for diamond-like carbon.
B
EARLY BACKGROUND TO DIAMOND-LIKE-CARBON
MATERIALS
The discovery of diamond-like carbon (DLC) was made
by Aisenberg around 1970 as he was searching for an electrically insulating layer to use in conjunction with plasma
ion-beam-deposited silicon for early demonstration work
on thin-film transistors [1]. After finding difficulty with
stoichiometry control of silicon oxide and silicon nitride
films, Aisenberg switched the sputtering cathodes in his
plasma ion-beam source from silicon to carbon. The
resulting carbon films were amorphous, transparent,
electrically insulating, and harder than glass. He coined
the name “diamond-like carbon” for these films since they
had many properties resembling those of diamond but had
no long-range crystal order. For the next 15 years or more,
Aisenberg pioneered the evaluation of DLC coatings in
applications including electronics, laser windows, fibre
optics, jewellery, and razor blades [1]. Within a few
years of Aisenberg’s discovery, similar DLC films were
reported by Holland and Ohja using an RF plasma
discharge process [2]. Since then, many other methods
for the deposition of DLC materials have been reported
[3], but the most successful commercial processes remain
the ion-beam and RF plasma methods.
Today, DLC is the name used to describe a family of
amorphous carbon materials that may contain hydrogen
and whose properties resemble, but do not duplicate, those
of diamond. The chemical bonding within DLC materials
is often described as a random covalent network of
sp2-bonded “graphitic” carbon structures interconnected
AND
C HARACTERISTICS
OF I ON -B EAM
DLC C OATINGS
MECHANICAL
Nanohardness
10 to 40 GPa
Compressive stress
0.7 to 6 GPa
Friction coefficient
0.1 to 0.2 (humidity-dependent)
Surface roughness
~ 1 Å (same as substrate)
CHEMICAL
Chemical resistance
Inert to acids, bases, solvents; undoped
DLC burns at 350-400°C in air
Hydrogen concentration
~ 1 to 40 atomic %
Typical dopant elements
N, F, Si
OPTICAL (λ = 250 to 770 nm)
Refractive index
1.8 to 2.4
Extinction coefficient
0.02 to 0.7
Raman G-peak position
1510 to 1570 cm-1 (λ = 514 nm)
OTHER
Electrical resistivity
106 to 1012 Ω cm
Thermal conductivity
~ 0.5 W/m K
by sp3 “diamond-like” linkages, with no long-range
crystalline order. In addition to carbon and hydrogen, DLC
materials may be doped with other elements such as
nitrogen, fluorine, and silicon. Doping by these elements
at greater than a few atomic per cent can enhance
material properties such as wear resistance, adhesion,
electrical conductivity, hardness, stress, and oxidation resistance. Diamonex’s NILADTM is an example of a silicon-doped
hydrogenated DLC material that possesses improved
data tech
69
communications satellites equipped with Kaufmantype ion thrusters operated on xenon gas [6]. Extensive
work was also carried out on gridless ion thrusters,
primarily in the former Soviet Union. Since their development, Kaufman-type ion sources have been used for
a variety of materials-processing applications, including
ion-beam etching, ion-beam sputter deposition [7],
and deposition of DLC [4, 8-18].
EVOLUTION OF COMMERCIAL ION-BEAM TECHNOLOGY
FOR DLC
Early on, it was realized that in many applications for
DLC, the direct ion-beam deposition process had
significant advantages over plasma processes, such as
the RF, microwave, and electron cyclotron resonance
plasma-enhanced CVD (PECVD) processes. For applications that require
(i) coating of electrically insulating substrates
(ii) outstanding adhesion
(iii) tight control of optical properties
(iv) minimal thickness non-uniformity
Figure 1
History of commercial DLC
process development at
Diamonex
adhesion, lower stress, and improved oxidation resistance
relative to conventional DLC [4]. In keeping with the present
convention in the technical literature, the term DLC is
used herein to refer to amorphous non-hydrogenated hard
carbon, amorphous hydrogenated hard carbon, and
doped modifications of these two materials. A summary
of the properties and characteristics of DLC coatings that
are relevant for data storage applications is presented in
Table 1.
EARLY HISTORY OF BROAD ION BEAMS
Figure 2
Schematic of Kaufman-type
gridded ion source
Aisenberg’s ion beams were of small diameter and
difficult to scale up. This scale-up problem was essentially solved by the development of so-called “broad ion
beams” at NASA during the late 1970s. Workers at NASA
(and in the former Soviet Union) were seeking a lightweight, fuel-miserly thruster for steering satellites. The
most successful “ion thrusters” were the broad-beam
gridded ion sources developed by Kaufman which still
bear his name today [5]. In 1997, Hughes Space and
Communications Company launched two commercial
(v) a coating thickness of hundreds of angstroms or less,
the direct ion-beam process is clearly superior to
PECVD. A key advantage of the ion-beam deposition
process is the high degree of control over the DLC material
properties which results from the largely independent
and easy control of critical process parameters such as
gas flow rate, ion-beam energy, and ion-beam current.
In addition, the operating pressure used in ion-beam deposition is considerably lower than that used in PECVD, which
reduces the potential for film contamination.
Since 1990, twelve commercial manufacturing
processes based on DLC and related coatings have
been developed by Diamonex, as illustrated in Figure
1. Most of these products, including sunglass lenses [810], wear-resistant laser bar-code scanner windows
and photomasks [11-13], microphone diaphragms,
magnetic heads [4, 14], thermal print heads [15],
magnetic disks [16-19], and ophthalmic lenses [20] utilize
a direct ion-beam deposition process. All of the processes
have been developed with high-output ion sources
which are currently commercially available. This diverse
range of applications attests to the applicability of ionbeam technology to real-world manufacturing.
TYPES OF BROAD-BEAM ION SOURCE
Gridded ion-beam sources
Of all types of ion-beam source, the gridded Kaufmantype ion source provides the most independent control
over process parameters over a wide operating range [5].
In a Kaufman-type ion-beam source, illustrated in
Figure 2, a plasma is initiated by applying a voltage
(“discharge voltage”) between a filament cathode and
an anode, adding gas, and heating the filament cathode
until it emits thermionic electrons. As the electrons accelerate toward the positive anode, they ionize the gas, forming
a plasma. Magnetic confinement of the emitted electrons
aids in increasing plasma density (and ion-beam current)
and reduces the necessary operating pressure. Positive
ions are extracted from the plasma to form the beam by
applying a positive beam voltage to the anode and a
negative voltage to the accelerator grid. The extracted
ion beam is charge-neutralized by adding thermal
electrons from a hot filament, hollow cathode, or
plasma bridge downstream of the accelerator grid.
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data tech
The gas flow rate into the ion source and the
discharge voltage determine the ion species formed in
the plasma. The beam voltage controls the ion impact
energy at the substrate. The accelerator voltage can be
used to adjust the beam shape or the ion-beam current
density at the substrate.
Gridless ion-beam sources
Demands for improved ease of maintenance and
increased product throughput have driven the development
of less complex, gridless ion-beam sources capable of
higher beam currents. Gridless sources are simpler in
design and do not suffer the space-charge-limit effect which
imposes an upper limit on the ion-beam current for gridded
sources. Compact gridless sources such as the End
Hall ion source [21] and the Diamonex Hall-Current Closed
Drift (CD) ion source [22] are capable of beam currents
up to 5-10 A, compared to about 1 A for typical gridded
sources. Therefore, very high etch rates and deposition
rates (e.g. up to 100 Å/sec of DLC using the Hall-Current
CD source) are possible using these gridless sources. In
addition, the gridless ion sources can also be operated
without filaments, allowing the use of gases that are incompatible with hot filaments. Furthermore, the ability to
operate without grids or filaments increases overall
process throughput by eliminating maintenance associated with these components.
By comparison with gridded sources, the ion-beam
energy obtained from a gridless source is low (<150 eV).
In addition, the ion energy distribution is wide because
the same DC voltage used to maintain the plasma also
repels and accelerates the ions to form the ion beam. Since
the local voltage falls off with distance from the anode,
ions that form further from the anode are repelled by
a lower potential and thus achieve a lower energy. In
addition, the gridless sources have some interdependence
of the main source operating parameters, i.e. anode voltage,
beam current, magnetic field, and gas flow.
Diamonex has pioneered the use of gridless ion
sources for high-current, high-rate deposition of a
variety of hard coatings including DLC [18-20]. Early
evaluations of commercially available End Hall ion
sources using reactive gas chemistries to produce DLC
and related coatings yielded good material properties,
but the ability to operate for extended periods under stable
conditions of high beam current, high ion energy, and
reasonable deposition rates was insufficient. As a result,
Diamonex developed a Hall-Current CD gridless ion source
that eliminated these and other problems [22]. These
sources have been utilized and refined over several
years of production of DLC and related coatings.
Figure 3 is a sketch of a Hall-Current CD ion source
specifically designed for retrofit onto static disk-coating
equipment such as the Intevac MDP and Balzers
Circulus systems. Figure 4 shows a front view of the source
in operation. The source consists of
(1) an annular anode region
(2) a filamentless hollow-cathode electron source
(HCES) internally mounted along the axis of the ion
source
(3) a magnetic circuit for intensifying and confining the
plasma.
During operation the HCES supplies electrons which
are attracted to the positively biased anode. As the
electrons accelerate toward the positive anode, they ionize
the gas, forming a plasma. The plasma is supported by
DC power supplies. The magnetic field temporarily
traps the electrons, resulting in more ionization and
increased plasma density. The positive ions in the
Figure 3
Diamonex Hall-Current CD
ion source
Figure 4
Hall-Current CD ion source in
operation
plasma are repelled from the positively biased anode to
form an ion beam. Electrons from the HCES, in addition
to supporting the plasma, are also attracted into the beam,
producing a charge-neutralized beam capable of coating
both electrically conducting and insulating substrates.
ION-BEAM DEPOSITION OF DLC
Most commonly, ion beams for DLC deposition are generated by extracting positive ions from a hydrocarbon gas plasma
within the ion source. The ion energy of the beam is
controlled by adjustment of the plasma potential with respect
to ground (the “beam voltage”). The ion beam is space-charge
neutralized by addition of electrons downstream of the source
to eliminate any potential for charge build-up on insulating
substrates. The hydrocarbon ion beam is directed onto the
substrate to form a DLC coating at a rate that is proportional to the ion-beam current density.
The ion-beam energy is a key parameter affecting the
DLC material properties. Figure 5 shows the relationship between nanohardness, compressive stress, and
ion-beam energy for DLC deposited from a DC Kaufmantype ion source operating on methane gas. The peak
hardness of about 22 GPa at 150 eV beam energy
correlates with maxima in the fraction of sp3 carbon-carbon
bonds, the atomic packing density, and the compressive
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71
BROAD ION BEAMS IN DATA STORAGE APPLICATIONS
Ion milling and reactive ion-beam etching
Since the mid-1990s, ion-beam milling (etching) has been
developed and used extensively in the manufacture of
thin-film magnetic heads, because of the excellent etch
uniformity and control of etch feature geometries which
are obtained. Gridded Kaufman-type ion sources with
hot-filament cathodes have been the workhorse in ion
milling with inert gases such as argon. More recently,
gridded ion sources with RF inductively coupled plasma
chambers have been developed for use in reactive ion
etching with corrosive gases as a way to enhance the etch
selectivity for oxide materials versus metals [23].
Figure 5
Hardness and compressive stress
versus ion-beam energy for DLC
deposited using a gridded
Kaufman-type ion source operated on methane gas
Figure 6
Hardness versus compressive
stress for DLC deposited using a
Hall-Current CD source operated
on three different hydrocarbon
process gases
72
data tech
stress. (Recent variations of the ion-beam process have
resulted in hydrogenated DLC materials with hardness
approaching 40 GPa.) Other properties vary more
monotonically as a function of ion-beam energy. For
example, the hydrogen concentration and the electrical
resistivity decrease monotonically with increasing beam
energy. The optical refractive index (n) and the absorption coefficient (k) increase with increasing energy, i.e.
the DLC material becomes progressively darker in
colour. Relative to the DLC with peak hardness, the
material formed at lower ion energy is more polymeric
(less dense, softer, and more transparent) and the
material formed at higher ion energy is more graphitic
(darker, with higher electrical conductivity).
The type of hydrocarbon gas can influence the
properties of the resultant DLC material, but under the
correct plasma and ion-beam conditions, it is possible
to make hard DLC coatings from many hydrocarbon
precursors. Figure 6 presents data on nanohardness versus
compressive stress for DLC films deposited using the
gridless Hall-Current CD source operated on three
different hydrocarbon gases. These results show that this
gridless source can produce DLC coatings of a hardness
equivalent to that achieved by gridded sources, at
deposition rates up to 50 Å per second.
Sputter deposition of magnetic materials
Recently, it has been demonstrated that ion-beam
sputter deposition offers significant advantages in the
density, crystallinity, and grain size and thickness control
of magnetic-material layers compared to other methods.
These factors combine to make ion-beam sputter deposition the method of choice for formation of magnetic layer
structures in the demanding fabrication of giant-magnetoresistive (GMR) heads [24].
Benefits of ion-beam DLC overcoats for magnetic data
storage
The demand for increased areal recording density on
magnetic media requires reduction of the magnetic
spacing between the magnetic head and the medium. The
current carbon overcoats on both the slider and the harddisk medium are now a significant fraction of the
remaining magnetic spacing. Therefore, future generations of heads and disks will require carbon overcoats
in the thickness range of 50 Å or less. This requirement
for ultrathin carbon will eventually cause the elimination
of conventional magnetron-sputtered carbon overcoats.
The high impact energy attainable with ion beams
(typically 50 to 500 eV), relative to the low impact energy
of sputtered atoms (<10 eV) in a magnetron sputter deposition process, is responsible for the improved coating
adhesion and surface smoothness which occur in the direct
ion-beam deposition process. In the early stage of
deposition, adhesion is improved by shallow atomic mixing
and chemical reaction at the coating/substrate interface
due to ballistic effects of the ion impacts. The ion
impacts also effectively desorb surface contaminants such
as water that interfere with adhesion and adversely
affect coating properties.
In addition to improving adhesion, ion impacts promote
a very high “nucleation density” and a growth mechanism
with minimal dependence on surface diffusion. The ions
are essentially implanted into the first few atomic monolayers
near the surface, so that the coating thickness increases by
a process often referred to as “subplantation”. This situation is ideal for producing very thin coatings with excellent
surface coverage. Additionally, the ion impacts result in coating
material densification and extremely low surface roughness. For example, using atomic force microscopy (AFM)
measurements, Diamonex has found that ion-beam DLC
coatings such as NILAD [4] can exhibit surface roughness
values as low as 1 Å for coating thicknesses between 50
Å and 30,000 Å. These ultrasmooth DLC surfaces are
required for sub-50 Å thick overcoats on the next generation of sliders and disks.
The most important functions of the carbon overcoat
are corrosion and wear protection of the magnetic
alloys used in magnetoresistive heads and on media. As
the thickness of conventional magnetron-sputtered
carbon overcoats is reduced, the coating becomes less
continuous, leading to increased corrosion. Therefore,
C OMPARISON
OF I ON -B EAM
S OURCES
TABLE 2.
FOR S INGLE -D ISK C ARBON O VERCOAT S YSTEMS
Gridded ion source
End Hall ion source
CD ion source
Design style
Dual-grid Kaufman
End Hall
Closed Drift Hall
Plasma frequency
DC or RF
DC
DC
Electron source for
plasma
Hot filament or RF
discharge
Hot filament
(thick wire; on-axis)
Hollow cathode
(on-axis)
Plasma enhancement
Permanent-magnet array
Single permanent magnet
Electromagnet
Ion extraction
Electrostatic via grids
Hall effect
Hall effect
Electron source for
ion-beam neutralization
External-filament,
hollow-cathode, PBN,
or RF discharge sources
Same as electron
source for plasma
Same as electron
source for plasma
Deposition rate
2-10 Å/sec
~10 Å/sec
25-40 Å/sec
Hardness
Up to 40 GPa
Up to 25 GPa
Up to 35 GPa
Thickness uniformity
±5-10%
±5-10%
±3-4%
Reactive-gas operation
(-)
Difficult
(-)
Difficult owing to arcing
(+)
Excellent
Ion-beam power
(-)
High power not possible
owing to grids
(-)
Spurious arcing at high
power
(+)
Excellent performance
at high power
Contamination
(0)
Not an issue if non-filament
neutralizer is used
(-)
Contamination due to
filament and sputter-erosion
of reflector plate
(0)
Not an issue
Thermal loading of
substrate
(0)
Not an issue if non-filament
neutralizer is used
(-)
High thermal load to
substrate due to radiation
from anode and filament
(0)
Not an issue, owing to
source cooling and use
of hollow-cathode
electron source
Control (deposition rate no/
and film properties)
(+)
Excellent
(-)
Variability due to build-up
of insulating coatings
(+)
Excellent
Maintenance
(-)
Frequent and difficult
(0)
Frequent
(+)
Infrequent; easy
DESIGN
CHARACTERISTICS
MATERIAL PROPERTIES
OPERATING CHARACTERISTICS
ion-beam-deposited DLC overcoats are able to offer
improved corrosion protection, because the ion-beam
process produces better coverage for a given thickness.
Because wear protection is a function of material
properties such as hardness, surface roughness, and
coefficient of friction, ion-beam DLC coatings are
ideal in wear resistance applications.
Ion-beam DLC head overcoats
For the past five years, commercial, production-scale ionbeam systems have been operated around the world to deposit
DLC overcoats on magnetic heads. Tremendous improvements in the durability of the magnetic-head-disk interface
have resulted from the deposition of hard ion-beam DLC
coatings onto the rails of magnetic heads [4, 14].
data tech
73
50 Å and 100 Å. The hardest DLC material, near the peak
in Figure 5, apparently wears the slowest in contact-startstop (CSS) testing and so may be the best material as the
DLC thickness is reduced. The rates of DLC deposition,
adhesion layer deposition, and etching are the order of
1 Å/sec or less over areas of about 50-300 square
inches. While these processing rates may seem low, the
emphasis is on control, and, owing to the small size of
magnetic heads, up to 10,000 to 20,000 sliders per
hour can be coated in a single production machine.
Ion-beam DLC overcoats on magnetic heads perform
acceptably at thicknesses below 50 Å, but even thinner
coatings are needed for the next generation of magnetic
data storage applications. A recent process improvement
is the reduction of the total DLC overcoat thickness by
eliminating the adhesion layer. Ion-beam-deposited
silicon-doped DLC materials, such as NILAD, are
currently being evaluated without the sputter-deposited
adhesion layer. Initial CSS testing indicates that the performance of NILAD is similar to that of the standard
undoped DLC with an adhesion layer. NILAD is also
expected to have a lower wear rate due to its higher temperature stability relative to undoped DLC.
Another area of process advancement for DLC head
coating has been the introduction of RF gridded ion-beam
sources. Compared to filament-based gridded sources,
the RF sources have reduced and simplified maintenance
cycles. However, in the RF sources process conditions
such as gas flow rate and RF power can affect both the
ion-beam current and the ion species, and therefore the
properties of the deposited DLC material, making
process development more complicated and less intuitive.
Diamonex is currently investigating the use of gridless
Hall-Current CD sources for coating magnetic heads. The
simple, compact nature of these sources, combined
with the NILAD process, enables the design of small, highthroughput, load-locked head-coating systems.
Figure 7 (top)
Polarization resistance
comparison of disks overcoated
with ion-beam DLC (i-C:H), and
magnetron-sputtered carbon
(a-C), hydrogenated carbon
(a-C:H), and nitrogenated
carbon (a-C:N)
Figure 8 (above)
Scratch resistance comparison
of disks overcoated with
ion-beam DLC (i-C:H), and
magnetron-sputtered carbon
(a-C), hydrogenated carbon
(a-C:H), and nitrogenated
carbon (a-C:N)
Figure 9 (right)
Schematic of retrofit Hall-Current
CD source system for static disk
systems
Current production ion-beam DLC systems for
coating sliders employ gridded ion sources. One source
is used for ion sputter etching of the slider surfaces with
an inert-gas ion beam prior to coating, and for DLC deposition from methane gas. Between the etch and DLC
steps, a second source is used to ion-beam sputterdeposit a thin (~20 Å) silicon-containing adhesion layer
[4, 18]. The DLC coating thickness is typically between
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data tech
Ion-beam DLC disk overcoats
Interest in ion-beam deposition for coating disks is
growing rapidly and pushing the development of compact
high-rate ion-beam sources designed and optimized for
carbon overcoat deposition. Table 2 summarizes the types
of ion-beam source which are currently being evaluated
for carbon overcoats in single-disk sputtering systems.
Industry tests of ion-beam DLC coatings and equipment
supplied by Diamonex have shown that 50 Å thick ionbeam DLC coatings provide adequate corrosion protection,
wear resistance, and CSS lifetime performance. In
contrast, a sputtered-carbon overcoat thickness of 100
Å is often required to achieve similar results.
Figure 7 is a comparison of corrosion test results for
magnetic disks with ion-beam DLC (i-C:H) and industrystandard magnetron-sputtered carbon (a-C), hydrogenated
carbon (a-C:H), and nitrogenated carbon (a-C:N) overcoats
with thicknesses of 50 Å and 100 Å. For these tests, the
DLC overcoat was deposited using a gridded Kaufmantype ion source operated on methane gas. Higher
polarization resistance corresponds to better corrosion resistance. The ion-beam DLC shows superior corrosion
protection and little if any change in the protection as the
coating thickness is reduced from 100 Å to 50 Å [16].
Ion-beam DLC overcoats were evaluated by nanoscratch
tests using an atomic force microscope fitted with a
diamond tip. Figure 8 is a comparison of the scratch resistance (scratch depth) test results for magnetic disks with
ion-beam DLC and industry-standard overcoats prepared
in the same way as those in Figure 7. Under identical
loading conditions the ion-beam DLC overcoat outperformed the sputtered overcoats; the scratch depth in the
Figure 10
Automated ion-beam control
system hardware
ion-beam DLC coating was 20% of that of the bestperforming sputter overcoat [17].
Figure 9 is a schematic of a Diamonex retrofit HallCurrent CD source system specifically designed for
Intevac MDP single-disk sputtering systems. The assembly
consists of two opposing ion sources mounted onto a process
chamber, and a turbomolecular pump. Because of the very
high deposition rate of 25 Å per second or greater, this
one unit replaces three stations normally used to produce
magnetron-sputtered carbon overcoats. These sources,
on a single process station, have been shown to produce
functional DLC overcoats at 50 Å thickness with the desired
uniformity over days of continuous operation. In addition,
the process is highly automated and very flexible,
allowing for adjustment of source parameters to control
the DLC material properties and deposition rate over wide
ranges. A typical hardware control set-up for the gridless
Hall-Current CD sources is shown in Figure 10.
Excellent tribological and corrosion test results have
been achieved on magnetic disks with 50 Å DLC
overcoats deposited by a Hall-Current CD ion source in
an Intevac MDP system. In the corrosion tests, DLC-coated
disks were exposed to ambient (25ºC, 40% relative
humidity) or hot-wet (60ºC, 80% relative humidity) conditions for five days. It was found that ion-beam DLC films
having a thickness of 50 Å provided sufficient corrosion
protection to the underlying media, as evidenced by a
negligible increase in the surface concentration of Co2+
after exposure as measured by secondary-ion mass
spectrometry and ion chromatography [19].
Magnetron-sputtered and ion-beam-deposited carbon
overcoats having thickness of 50, 75, and 100 Å were
CSS tested up to 50,000 cycles with DLC-coated sliders
under both ambient and aggressive environmental
conditions. Significantly enhanced CSS performance of
ion-beam-deposited DLC compared to magnetronsputtered carbon was found. No DLC failures were found
at 7.5 nm thickness, and the failure rate at 5 nm thickness (6%) was 17 times less than the failure rate for
sputtered hydrogenated carbon (100%) and 12 times
less than for sputtered nitrogenated carbon (70%).
Diamonex is also qualifying a linear gridless ion
source for deposition of DLC overcoats within in-line
disk-coating systems. Figure 11 shows a photograph of
the 36-inch linear Hall-Current ion source in operation.
Figure 11
Linear Hall-Current ion
source in operation
PRESENT AND FUTURE COMMERCIAL APPLICATIONS
IN DATA STORAGE
The rigorous requirements for data storage materials and
products impose severe demands on manufacturing
process methods. Many different types of ion-beam
systems are now commercially available to meet these
demands. As illustrated in Table 3, each type of ion-beam
system has unique design attributes and operating
characteristics which can be readily matched to material
and process requirements.
SUMMARY
In the past decade, broad ion beams have demonstrated
their viability and importance in commercial applications
as diverse as sunglasses and eyeglasses, industrial optics,
semiconductors, data storage, and even satellite propulsion, for which they were initially designed. Each of the
applications in material processing (including deposition
of DLC) takes advantage of the control of material
properties, repeatability, uniformity, and cost-effectiveness afforded by commercial ion-beam systems.
There are several key reasons behind the establishment of commercial ion-beam processes in data storage
and other industries. In the past, ion-beam technology
was often disregarded for production since the processingrate capabilities were inadequate for cost-effective
manufacturing. Within the past five years, the processing
areas, ion-beam currents, and deposition rates attained
by gridless ion-beam sources have increased to 20-40 times
those of equivalent-size Kaufman-type gridded sources.
Further, the elimination of grids reduces maintenance and
contamination and increases operating efficiency.
Another major facet of advanced ion beams is the
capability of operating with reactive gases in sophisticated
processes (e.g. reactive-ion-etching DLC deposition)
with RF gridded and gridless sources. Advanced ion-beam
sources may now be used to perform multiple tasks
and operations along the manufacturing line including
cleaning, etching, ion milling, and deposition.
Simultaneously, the strong features inherent in gridded
ion-beam sources including excellent hardware control,
stable process conditions, and material property control
have not been compromised in the new source designs.
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75
TABLE 3.
M ATRIX FOR B ROAD -B EAM I ON S OURCES
D ATA S TORAGE A PPLICATIONS
Kaufman-type
gridded source
RF gridded
source
End Hall
source
Hall-Current
(CD) source
MATERIAL REMOVAL
Ion-beam etching
Reactive ion-beam
etching
Ion milling
(Surface modification
+
-
+
+
0
-
0
0
+
0
+
0
+
+
+
+
-
-
0
+
0
+
-
+
-
0
+
+
DEPOSITION
Sputter deposition of
magnetic materials
(Reactive ion-assisted
deposition
DLC head overcoat
DLC disk overcoat
Ion-beam systems are now readily automated and have robust
designs requiring minimal maintenance with high uptime.
The sources are reliable and controllable and provide
enhanced performance in many processes compared
with other competitive technologies.
The ion-beam process produces the ultrasmooth DLC
coatings with enhanced coverage properties required for the
ultrathin 50 Å carbon overcoats on next-generation magnetic
heads and disks. Compact, gridless, filamentless sources and
process technology to produce functional 50 Å DLC
overcoats on disks at high rates is available, and is being
optimized on production disk-manufacturing equipment.
REFERENCES
[10] T. Hughes and F. Kimock, “Ion beam deposited DLC
coatings: characteristics and commercial applications
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Conf. Proc. (1993), pp. 139-145.
[11] F. Kimock and B. Knapp, “Commercial applications
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Metallurgical Coatings, San Diego, CA (1992).
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films for optical applications”, Soc. Vacuum Coaters
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[13] F. Kimock, B. Knapp, and S. Finke, “Abrasion wear
resistant coated substrate product,” US Patents Nos.
5,268,217 (Dec. 7, 1993); 5,506,038 (Apr. 9,
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(June 3, 1997); 5,643,423 (July 1, 1997).
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[15] D. Brown, M. Baylog, R. Petrmichl, B. Knapp, F.
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[20] B. Knapp, F. Kimock, R. Petrmichl, and N. Galvin, “Ion
beam process for deposition of highly abrasion-resistant coatings,” US Patent No. 5,508,368 (Apr. 16, 1996).
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ABOUT THE AUTHORS
Dr Fred M. Kimock is Vice President,
Technology at Diamonex, Inc., where he
is responsible for process research and
applications development of CVD diamond products, and of DLC coatings
deposited by ion-beam and RF plasma
processes. Dr Kimock earned a PhD in chemistry from Pennsylvania
State University in 1985. He is co-author of more than 20 publications and presentations, and inventor on 23 patents and patents
pending covering processes and commercial applications for CVD
diamond, DLC, and related materials.
Dr Steven J. Finke is Vice President,
Engineering at Diamonex, where he is
responsible for the development of
process hardware for deposition of
CVD diamond and DLC for many
applications, including data storage.
Dr Finke received a PhD in chemical
engineering
from
Iowa
State
University in 1988. He is an inventor
on 10 patents related to deposition of DLC and related materials.
Dr David W. Brown is Senior
Research Associate, Data Storage at
Diamonex, where he is responsible
for process development of DLC and
related coatings for applications in
data storage. Dr Brown earned an MS
in applied physics and a PhD in materials science from the University of
California, Davis in 1990. He is an
inventor on five patents or patents pending related to ion-beam
processing of materials and deposition of DLC.
Edward G. Thear is Sales Manager,
Data Storage at Diamonex, where he is
responsible for sales and business
development of DLC technology for
the data storage industry. Mr Thear
earned a BA in physics and is currently completing an MBA degree at
Moravian College. He has been a key
figure in the commercialization of DLC
technology for over six years, and is an inventor on two patents
pending related to DLC coatings for application in data storage.
IF YOU HAVE ANY ENQUIRIES REGARDING THE
CONTENT OF THIS ARTICLE , PLEASE CONTACT:
Ed Thear
Diamonex, Incorporated
7331 William Avenue
Allentown
PA 18106
USA
Tel: +1 (610) 366-7100
Fax: +1 (610) 366-7144
E-mail: [email protected]
Web site: www.diamonex.com
data tech
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