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Surface & Coatings Technology

Plasma diagnostical comparison of the MSIP process of (Ti,Al)N with

pulsed and dc power supplies using energy-resolved mass spectroscopy

E. Lugscheider, K. Bobzin, N. Papenfug-Janzen*, M. Maes, D. Parkot

Materials Science Institute, RWTH Aachen University, Augustinerbach 4-22, 52062 Aachen, Germany

Available online 11 September 2004

Abstract

Plasma diagnostics by energy-resolved mass spectroscopy is a well-known method to understand and control rf plasmas, e.g. during

plasma etching, and PECVD processes. Only very few scientific work concentrates on the investigation of the magnetron sputter ion plating

(MSIP) process. This is the reason why, so far, this process is not very well understood. A technology that has been gaining increasing

importance within the last decade is the use of pulsed power supplies. On the one hand, this technology allows the sputtering of insulating

coatings with a significantly higher sputtering rate than with rf plasma. On the other hand, the degree of ionization is higher than in dc

processes. In this article, the ion energy distribution of aluminum and titanium as well as titanium nitride is observed by using a pulsed

cathode power supply and a dc power supply. The different behavior of the ion energy distributions depending on the power supplies is

shown. The cathode power and the nitrogen flow are the observed varying process parameters.

D 2004 Elsevier B.V. All rights reserved.

Keywords: MSIP process; dc process; Pulsed process

1. Introduction

The magnetron sputter ion plating (MSIP) process is a

common technology to apply thin hardcoatings against wear

and corrosion as well as optical coatings. Although the

technology is established for industrial applications, the

physical processes have not been investigated sufficiently,

yet. Therefore, MSIP is mainly based on experience.

Mass spectroscopy is well known for the diagnostics of rf

plasma processes, e.g. Refs. [1–6]. However, only a few

articles [7–10] on dc and pulsed sputtering of titanium- or

chromium-based coatings have been published, yet. A first

extensive investigation of all aspects of the MSIP process

has been gathered in Ref. [11].

In this article, the analysis of the plasma inside the MSIP

coating unit CC 800R/9 by CemeCon AG at the Materials

Science Institute of the RWTH Aachen University for a

0257-8972/$ - see front matter D 2004 Elsevier B.V. All rights reserved.

doi:10.1016/j.surfcoat.2004.08.011

* Corresponding author. Tel.: +49 241 8096512; fax: +49 241

8092264.

E-mail address: papenfuss@msiww.rwth-aachen.de

(N. Papenfug-Janzen).

(Ti,Al)N hardcoating process is presented. A mass spec-

trometer EQP 300 by HIDEN Analytical was used to

measure the ion energy distributions of titanium, aluminum

and titanium nitride. The cathode power and the nitrogen

flow are the variable process parameters. A dc power supply

MDX Pinnacle and a sinusoidal pulsed PEII, both by

Advanced Energy, were applied. The plasma characteristics

of these supplies were compared to find possible reasons for

the much better coating properties when using pulsed

plasma.

2. Experimental

For the presented work a HIDEN EQP 300 mass

spectrometer (Fig. 1) was used, which was described by

Budtz-Jbrgensen [12]. The HIDEN EQP 300 consists of five

main sections. The functions of those sections shall briefly

be explained. The extraction section consists of the extractor

and the lens 1. In this part, the ions and neutrals that pass the

orifice have to be directed towards the detector. The

ionization source is only needed when measurements in

188–189 (2004) 164–167

Fig. 1. Assembly of the HIDEN EQP 300 [12].

E. Lugscheider et al. / Surface & Coatings Technology 188–189 (2004) 164–167 165

the RGA mode are conducted. Then, neutral particles are

ionized by a dual-filament electron impact ionization source.

The deceleration section consists of the axis, the lens 2 and

the quadrupole lens. This section is needed to decelerate the

ions to an energy of about 40 eV. Only at this low kinetic

energy ions can pass the 458 bend to the analyzer. The

energy filter is a 458 sector field energy analyzer, where ionsare deflected by an electric field depending on their kinetic

energy when the particles enter the section field. The last

part of the HIDEN EQP 300 is the mass filter. This filter is a

quadrupole mass spectrometer consisting of four metal rods

with a superposed dc and rf voltage. Only particles with a

special mass-to-charge ratio can pass this filter and can be

detected, while the other m/q ratios are removed by the rf

field and the dc field, respectively.

Table 1

Process parameters to investigate the nitrogen influence

Ar flow

[mln/min]

N2 flow

[mln/min]

Kr flow

[mln/min]

Power per

cathode [W]

100 0 100 2000

100 75 100 2000

100 100 100 2000

100 127 100 2000

100 150 100 2000

100 175 100 2000

Table 2

Process parameters to investigate the cathode power influence

Ar flow

[mln/min]

N2 flow

[mln/min]

Kr flow

[mln/min]

Power per

cathode [W]

100 127 100 1000

100 127 100 1500

100 127 100 2000

100 127 100 2500

The measurements were carried out at the Materials

Science Institute at the RWTH Aachen University on an

MSIP coating unit of the type CemeCon CC 800R/9 with

four cathodes CK 588. The mass spectrometer was

positioned parallel to one cathode with a distance of about

80 mm for the presented experiments. The observed coating

material was (Ti,Al)N, produced by the magnetron sputter-

ing of two-component Ti–Al targets with nitrogen as a

reactive gas. Argon and krypton were used as process gases.

The pulsed plasma experiments were conducted by using

two sinusoidal pulsed power supplies of the type PE II by

Advanced Energy. Two cathodes got a sinusoidal negative

voltage, while the corresponding cathodes were discharged.

The output frequency was 40 kHz. First results concerning

the use of this technology on (Cr,Al) N coatings were

presented, recently [9,10].

The mass spectroscopy measurements were conducted in

the SIMS mode (Secondary Ion Mass Spectroscopy).

0 5 10 15 20 25 30

0 mln/min N2

75 mln/min N2

100 mln/min N2

127 mln/min N2

150 mln/min N2

175 mln/min N2

co

un

tin

g r

ate

[H

z]

energy [eV]

107

106

105

104

103

27 Al+

Fig. 2. Energy distribution of Al+ ions for different N2 flows in the dc

process.

0 5 10 15 20 25 30

N2 flow 0 mln/min

N2 flow 75 mln/min

N2 flow 100 mln/min

N2 flow 127 mln/min

N2 flow 150 mln/min

N2 flow 175 mln/min

co

un

tin

g r

ate

[H

z]

energy [eV]

107

106

105

104

103

27 Al+

Fig. 3. Energy distribution of Al+ ions for different N2 flows in the pulsed

process.

0 120 140 160 180 200

Pulsed

DC

2,0x107

1,5x107

1,0x107

5,0x106

0,020 40 60 80 100

po

we

r [e

V/s

]

N2-flow [mln/min]

48 Ti+

Fig. 5. N2 flow dependence of the integral of the energy distributions of Ti+

in the dc and the pulsed process.

E. Lugscheider et al. / Surface & Coatings Technology 188–189 (2004) 164–167166

Therefore, only ions were detected and no further ionization

of neutral particles was forced by high-energy electrons.

The orifice was electrically charged with a �5 V voltage.

In order to investigate the influence of the nitrogen flow,

the process parameters were chosen from Table 1, whereas

the parameters from Table 2 were used to observe the

influence of the cathode power. The process parameters

were unchanged for the dc and the pulsed processes,

respectively.

3. Results

First, the influence of the nitrogen flow was observed.

The energy distributions of Al+ ions are presented in Fig. 2

for the dc process and in Fig. 3 for the pulsed process. It can

be seen that the target poisoning in the dc process is much

more obvious than in the pulsed process. Due to the large

decrease of the maximum of the distribution, the poisoning

can be located below 75 mln/min. The shape of the energy

distribution in the pulsed process is broader than in the dc

0 100 120 140 160 180

27 Al+

48 Ti+

62 TiN+

po

wer

[eV

/s]

N2-flow [mln/min]

107

106

105

104

103

102

20 40 60 80

Fig. 4. N2 flow dependence of the integral of the energy distributions of

Al+, Ti+ and TiN+ in the dc process.

process. Moreover, the energy of the ions is about 5 eV

higher than in the dc process.

In Fig. 4, the number of detected ions by means of the

integrals of the distributions is shown for Al+, Ti+ and TiN+

in the dc process. It can be observed that the number of

detected metallic ions first decreases, then increases after

passing a minimum. The reason for this is that initially the

nitrogen is a reactive gas, but after the poisoning of the

targets it becomes a process gas supporting the sputtering.

The energy of the nitrogen has not been measured, because

its number of detected ions exceeds the permitted measuring

range. Therefore, the settings of the EQP would have been

changed. However, this would lead to incomparable data.

Contrary to Ref. [7], nitride ions could be observed in the

process with a content of about 1% of the metallic ions.

Although the aluminum fraction in a coating is lower than

the titanium fraction, the number of detected aluminum ions

is higher. This can be explained by the lower ionization

energy of aluminum. The distribution of AlN+ is not shown

here, because it could be proven that ArH+ is formed during

the process [11]. AlN+ and ArH+ have the same mass-to-

0 100 120 140 160 180 2000

Pulsed

DC

po

wer

[eV

/s]

N2-flow [mln/min]

4x105

3x105

2x105

1x105

20 40 60 80

62 TiN+

Fig. 6. N2 flow dependence of the integral of the energy distributions of

TiN+ in the dc and the pulsed process.

2500

DC

Pulsed

po

we

r [e

V/s

]

power/cathode [W]

5,0x106

4,5x106

4,0x106

3,5x106

3,0x106

2,5x106

2,0x106

1,5x106

1,0x106

1000 1500 2000

48 Ti+

Fig. 7. Dependence of the energy distribution of Ti+ on the power per

cathode in the dc and the pulsed process.

E. Lugscheider et al. / Surface & Coatings Technology 188–189 (2004) 164–167 167

charge ratio. Therefore, both ion species cannot be

distinguished by mass spectroscopy.

In Fig. 5, the dc and the pulsed processes are compared

for Ti+, while the comparison of TiN+ is shown in Fig. 6. It

can be observed that the number of detected Ti+ ions in

pulsed processes in the reactive mode is higher than in dc

processes. However, during metallic sputtering the dc

process has a higher ionization. Furthermore, the number

of nitride ions is higher in the dc process throughout all

nitrogen flows.

In Fig. 7, a comparison of the dc and the pulsed process

is shown for the different cathode power in the reactive

mode from Table 2. It can be seen that the pulsed process

has an ionization about 20% higher than the dc process.

Moreover, the pulsed process exhibits a nearly linear

dependence on the cathode flow, while the dc process

shows a nonlinear behavior.

4. Conclusion

In this article, the magnetron sputter ion plating process

with dc and pulsed power supplies was investigated. It was

shown that with constant extraction conditions the pulsed

process has a higher number of detected metallic ions in the

reactive mode, which is used for the application of nitride

hardcoatings. However, in the metallic mode a dc power

supply is more suitable. In contrast to Ref. [7], the forming

of nitride ions could be proved, even though AlN+ was not

distinguishable from ArH+ by mass spectroscopy. More-

over, the metallic-to-nitride ion ratio is about one order of

magnitude higher than in recent publications on rf sputtering

[13]. Although the fraction of aluminum in the hardcoatings

is much lower than the fraction of titanium, the content of

ions in the plasma is vice versa. Therefore, this has to be

caused by neutrals, which have not been investigated here,

or processes at the surface. Finally, it was shown that the

poisoning of the targets happens even at low nitrogen flows,

and it can be observed by mass spectroscopy.

Acknowledgements

The authors gratefully acknowledge the Deutsche For-

schungsgemeinschaft (DFG) for the financial support within

the collaborative research center SFB 442.

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