Acta Polytechnica Vol. 43 No. 112003

Measuring the Process Parameters of the
IBAD Method

M. Zoriy, F. iernf, D. Palamarchuk, S. Konvidkov|,l. Hiittel

Chromi,um nitride flms are knoun as good protective layrs for against both corrosi,on and wear. These coatings haae been studied in denil
during recent years. Their protectiae capabilitl strongly depends on the deposition conditions. A modern method for preparing chromium
nitride is the IBAD (Ion Beam Assisted Deposition) method.
The mrtin parameter deterrnining the compositi,on and properties of the f.lms prepared b1 the IBAD method is the arriaal ratio of impinging
nitrogen ions to chromiunT atoms.

In orfur to calibrate the ion beam XY-mechanical scanner uith a Faradal cup, a detector uas designed and consltucted. By mathematical
processing of the data, the flux of the nitrogen atorns was found. fo obtain the llux of the chromiuln atoms the RBS and Talystep methods

uere usea.

Nou, on the basis of this d,ata, arc can perfonn CrN, coutings uith controLled composition and propeflies.

Kelwords: IBAD, CrN, CrN2, calibration, eleclron beatn.

1 Introduction
In recent years the hard coatings have play a major role in

mechanical engineering. Hard coatings are used to increase

resistance against wear and fatigue.

Many kinds of hard coatings are now known. 'lhe most
widely used is titanium nitride, because of its high hardness

[]. Chromium nitride is used for the same pr<rpose [2].
In addition to high hardness it has a very goocl corrosion
resistance, especially under high temperatures in various
atmospheres. The hardness and friction properties of chrrcmi-

um nitride coatings depend on the structute and orientation
of the crystals in the film [3]. The corrosion properties also

depend on the porosity/densitv of the coatings [4]. The im-
portance of the deposition parameters is critical.

There are many methods for preparing these coatings,

which can be classified in various ways. Eflective modern
methods are based on plasma and ion beam processing tech-
nology. One of these is the IBAD method [5].

A schematic view of the experimental arrangement for
the IBAD method is shown in Fig l.

Rotary

Iy'anipulator

lon
Source

lon Beam Ni + N-

It involves deposition of a desired material using a vac-

uum electron beam evaporation technique and simultaneous
bombardment by an energetic ion beam.

Chromium nitride has nvo stoichiometric modifications -
CrN and CrrN [6]. Howeveq wewill be preparing a customary

composition CrN*, where x is in the range of [0+l], and we

will investigate the characteristics of the process in depend-
ence on the x ratio. To do this, we need to calibrate the depo-
sition subprocesses - the atomic fluxes of chromium and
nitrogen in IBAD equipment.

2 Calibration of an ion beam

A flow of nitrogen of high purity is fed into the ion source,

where ionization of the nitrogen takes place. The ion source

was developed from the Franks Jivin Anode design. It consists

of a graphite outer tubewith closed ends, mounted in an insu-

lator. Inside the tube there are two tungsten electrodes, closely

spaced about the centerline ofthe tube.

At a distance of 35 mm away, there is a corresponding
wider slit in the extractor electrode. During operation a high
tension of 90 keV is supplied to the ion source.

The large potential diflerence between the positive HT in
the ion source and the zero voltage of the extractor electrode
provides the force to accelerate the positive nitrogen ions to

a high velocity and form the ion beam. Once the ions pass

through the slit in the extraction electrode they continue at

constant velocity until they hit the work piece. The ion beam

is a mixture of molecular and atomic ions in proportion 3:1.

As a goal we need to know the quantity of nitrogen atoms

that the sample per unit area per unit time - the flux of the
nitrogen atoms. The TECVAC 221 Ion Implanter has no
suitable measuring instrument for this, so we made an appro-
priate device ourselves and used it to perform the calibration
of the ion beam.

c=-r
Evapomted Cr

l: Schematic view of experimental
IBAD method

Eleclron
Beam

Fig. arrangement for the

23



Acta Polytechnica Vol. 43 No. l/2003

This device is a mechanical XY-scanner that consists of
a Faraday cup detectoS nvo stepping-motors, a scrolling
mechanism and other accessories.

A program was written in C language to conrrol rwo
stepping-motors, which moved the detector into selected
points of cross-sections of the ion beam. An XY-scanner was
applied in ttre region of dimensions 200 x 200 mm with
a step of 2 mm. Another program estimated the value of ion
beam densiry and plotted the graph that illustrated the pro-
file of ion beam density. The resulting distribution of ion
beam density in the TECVAC Ion Implanter is shown in
Fig. 2. This is the profile of the ion beam current density,
but we need a profile of the flux of the nitrogen atoms.
We therefore need to perform a mathematical procedure to
transform ion beam density into atomic nitrogen flux. We
calculated the quantity of nitrogen atoms as follows:

So the fluxes of the atomic and molecular ions will be.
respectively:

^ P 6.2+2.tot3P* =i =14355'lol3 cm-2's-l;

P2N = P - Px = 5.742' l0l3 - 1.4355' l013=

=4.3065.1013 cm-2.iI
The flux of the atoms included in the atomic nitrogen ions
equals the flux of the nitrogen ions:

NN= PN = I.4355' i0r3 .--2',-';
The flux of the atoms included in the molecular nitrogen

ions equals flux of equal rwice the flux of the molecular nitro-
gen ions:
Nr*= t'Pr"= 8.613'10t3 cm-2's-';

So th. tot"ljq* of .tit-g.n utornr it

ln, =t"ll,rr =t.oou'rotn.--t ,i'l

- total flux of nitrogen atoms.

The Profile monitoring of the flux of aroms is shown in
Iig.3

0
50

X-axis [mm] o
-so -so Y-axis [mm]

Fig. 3: Profrle monitoring of total flux of nitrogen atoms

Another view of the same profile is presented in Frg. 4.
This figure shows that the profile of the flux has its maximum
in the ellipse region, extended along the X-axis.

-60 so to y_axis [mm]

Fig. 4: Profile monitoring of total flux of nitrogen atoms (another
view)

q.i- 
12

c

'b 10

=

B
50

50

Y-diE mmXdinm
.50 -50

Fig. 2: Profile monitoring of total flux of ions

Giaen dnta:

I =9.2 pNcm2 - example of value of ion beam density (mea-
sured by Faraday cup detector);

e = 1.6021892. l0-lsc - electron charge magnitude;

P1g - flux of atomic nitrogen ions;

P2^*' - flux of molecular nitrogen ions;

P - total flux of ions;

N1,'- flux of nitrogen atoms included in atomic nitrogen ions;

N2.iy - flux of nitrogen atoms included in molecular nitrogen
ions;

N - total flux of nitrogen atoms.

Pr o cedur e for S ohrti,on :

We know the ion beam density and charge of one ion.
From this data we are able to calculate the total flux of ions:

p =! =-g+rr =5.742' 1013 cm-2's-r - totul fl,,*e 1.60221892.10-r
of ions;

"'* =? - number of molecular ions: number of atomic ions:PNI

P=Px,*Porr=) P 
=l+3=4.

Py

24

Eo

a



Acta Polytechnica Vol. 43 No. 112003

;E
C(g

='fi'oE
I

=(5

E50
E

.9x
I.o

Fig. 5 shows a view fiom below of the profile monitoring of
the total flux of the nitrogen atoms, and gives more informa-
tion about the distribution the flux in the cross-section of the
ion beam. Using this figure we can select a zone approxi-
mately 50 mm long and 30 mm wide, where the flux of the
nitrogen will vary within a range of 15Vo.

-!o 30 o -30 -50

Y-axis [mm]

Fig. 5: Profile monitoring of total flux of nitrogen atoms, seen

from below

So if we locate our samples in this region we will achieve

satisfactory homogeneity and will be able to control the quan-
tity of the nitrogen atoms that arrive on a unit area Per one

second.

3 Calibration of the electron beam
evaPoration system
To check the composition of chromium nitride we also

need to calibrate the flux of the evaporated chromtum atoms.

In the TECVAC Ion Implanter the evaporation is sup-

plied by an electron beam grn. When the electron beam gun
is running, it produces a powerful beam ofelectrons that are

accelerated by negative high-tension up to -10 kV This elec-

tron beam melts and evaporates the chromium that deposits
on the sample.

Besides depositing chromium on the sample that is

mounted on the rotary manipulator, chromium is also depos-

ited on the quartz crystal microbalance. This crystal oscillates

with an original frequency, of 5 MHz, and the frequency of
oscillation decreases with the mass of deposited chromium.
In this way we can measure the thickness of the deposited
coatings.

To check the measured thickness of the coatings, the
Thlystep m€thod was used. In this method, a thin needle
moves along the surface and detects the step between the
surface ofthe substrate and the surface ofthe coating. Then
the value of this step is converted into an electrical signal

and the thickness of the coating is displayed.

To obtain the quantity of the chromium atoms in our

coatings, the RBS (Rutherford Backscattering SpectroscoPy)

method was used. Our samples were bombarded by alpha
particles with energy 2MeV. By measuring the energy of
the backscattered particles the exact quantity of chromium

atoms was determined. Examples of the energetic spectra

are shown in Fig. 6 and tig. 7.

k
i+

It
BSAC.

I.
II

Exp.7201(200 nm)

o

Si

f'\

)\

1 000

200 400 600 800 1000 1200 1400

Energy (keV)
r600

Fig 6: Sample 200 nm..2 MeV alpha particles. The quantity of Cr
atoms is 2.1 . I0"'cm-t.

Exp.7204 (300 nm)
Cr-tt\

\

I

E
(5

5b
C
A

n -t-
200 400 600 800 1000 1200 1400 1600

Energy (keV)

Fig. 7: Sample 300 nm, 2_MeV^alpha particles. The quantity of Cr
aroms is 5.05. I0''cm-'.

By comparing this data with the data measured by our
IBAD equipment we calibrated the electron beam evapora-
tion system.

For example, when the electron beam currentwas l00mA,

the flux of the chromium atoms was 2'1013 at'cm-2.

Conclusions
Our ultimate goal is to prePare coatings of chromium

nitride. To check the properties of these coatings we need to
calibrate the deposition subprocesses - the atomic fluxes of
chromium and nitrogen in the IBAD equipment. These cali-

brations have been done.

In order to calibrate the ion beam we designed and

constructed an XY-mechanical scanner with a Faraday cuP

detector. By mathematical processing of the data we found
the flux of the nitrogen atoms.

To obtain the flux of the chromium atoms we used the
RBS and Talystep methods.

25



Acta Polytechnica Vol. 43 No. 112003

Now, on the basis of this data, we can perform crN* coat- Doc. Ing. Frantisek ierny, csc.
ings with controlled composirion and properties. phone: 1420 224 zbz $;7

e-mail : cernyf@fsid.cvur.cz

Acknowledment
This research has been supported by GACR grant

No. 106/02/1194 and conducted within the fiamework of
research project No. J04l98 : 2 I 00000 I 2.

References
tll Galvanetto, E., Galliano, F. P., Fossati, A., Borgioli, F.:

Surf. Coat. Technol., Yol. 44,2002, p. 1593-lO0O.

I2l Mernagh, V. A, Kelly, T. C., Ahern, M., Kennedy, A. D.,
Adriansen, A P. M., Ramackers, P. P.J., McDonnel, L.,
Kockoek, R.: Surf. Coat. Technol., Vol. 49, 1991, p. a62.

t3l Smidt, F. A.: Int. Mater. Rev., Vol. 35, 1990, p. 61.

t4l Kumar, S., Rajul, V. S., Arunachalam, J., Khanna, A.,
Prasad, K.: Thin Solid Films, Vol. 388, 2001 , p. 195-200.

t5l Pakala, M., Lin, R. Y.: Surf. Coat. Technol., Vol. 81,
1996, p. 233-239.

t6l Cunha, L., Andritschky, M., Rebouta, L., Pischow, K.:
Surf'. Coat. Technol., Vol. I19, 1999, p. I152-l160.

Ing. Miroslav Zoriy
e-mail: mzorij@seznam.cz

Ing. Dmytro Palamarchuk

Department of Physics

Doc. Ing. Svatava Konviikovd, CSc.
phone: +420224 352 5ll
e-mail : konvicko@fsid.cvut.cz

Department of Mechanics

Czech Technical University in Prague
Faculty of Mechanical Engineering
Technickii 4.
166 07 Prague 6, Czech Republic

Doc. Ing. Ivan Htittel, CSc.
phone: +420 224 353 205
e-mail: huttel@vscht.cz

Institute of Chemical Technology
Technickd 3,
166 28 Prague 6, Czech Republic

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