24P001-O
Properties of high power pulsed magnetron sputtering plasmas
for deposition of diamond-like carbon films
DLC成膜向け高電力パルスマグネトロンスパッタリングプラズマの特性
Takashi Kimura, Ryotaro Nishimura and Masayasu Iida木村 高志, 西村 亮太郎，飯田 将康
Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan
名古屋工業大学 〒466-8555 名古屋市昭和区御器所町
Properties of pulsed magnetron sputtering plasmas and the relationship between the properties of depositedfilms and the operating conditions of the pulsed plasmas, such as Ar gas pressure and the magnitude ofpulsed current, have been experimentally investigated. The maximum of the hardness measured by ananoindenter increases with the magnitude of pulsed current and reaches 17 GPa at 20 A. On the otherhand, with increasing Ar pressure, the hardness of the films decreases from 15-17 GPa at 3mTorr to 9-10
GPa at 20mTorr.

1. Introduction
Physical vapor deposition (PVD) has been
widely used as a film deposition method in manyindustries. High power pulsed magnetron sputtering
technology has been attracted, because target
species sputtered by energetic ion bombardment arehighly ionized and the energy of the ions is highenough to modify the surface of the substrate. [1,2]The magnetron operates at a pressure of 1-20mTorr
with a magnetic field of 0.01-0.1T, and theinstantaneous power density in the vicinity of thetarget electrode is on the order of kW/cm2.
Diamond-like carbon (DLC) films have attracted
for material industries because they have uniqueproperties, such as high hardness, low friction,
chemical inertness, high wear resistance and opticaltransparency. Most DLCs have been conventionallydeposited by plasma enhanced chemical vapor
deposition (PECVD). It is well known that theenergetic ions can play a significant role on film
growth even in PECVD process.
In this study, the properties of pulsed magnetron
sputtering plasmas and the relationship between theproperties of deposited films and the operating
conditions of the pulsed plasmas, such as Ar gas
pressure and the magnitude of pulsed current, areexperimentally investigated.
2. Experiments
A schematic diagram of the experiment isshown in Fig.1. The distance between the target(80mm in diameter, carbon material ) and substrateis 45mm, and the strength of magnetic field isapproximately 0.04T in the vicinity of the target
surface. Pulse repetition frequency is about 40Hz
and the time-averaged dissipated power is about
40-50W. The film deposition on the silicon

substrate is performed for 2-3 hours, so that the film
thickness reaches 0.5-0.6 μm.
The electrical measurements are carried out by
simultaneously measuring the applied voltage
between the electrodes and the current across thedischarge. The voltage between the electrodes isdivided into 1/1000 using a voltage divider with abandwidth of 100 MHz, whereas the current ismeasured using a current transformer (CT) with abandwidth of 20 MHz. The optical emission
measurement system consists of a slit, a fiber
bundle, and a monochromator with acharge-coupled device (CCD) array detector. The
measured optical emission spectra is line-averaged
and time-averaged.
Digital oscilloscope

16μF

V0ＮSCTSＮ

Voltagedivider(1000:1)

NSC

Optical system

To vacuum system
PCVacuum chamberGas inlet

Fig 1 Experimental apparatus

Measurement of film hardness using ananoindenter is performed up to a depth ofapproximately 60 nm of the film thickness, wherethe maximum of the load is around 500 μN. For

20Hardness (GPa)

3. Results and Discussions
An example of the voltage-current waveforms isshown in Fig. 2. As shown in Fig.2, the discharge
is ignited with the time delay of 20-30μs after thevoltage is applied between the electrodes. Suchtime-delay was observed at any experimentalconditions. The duration of time-delay decreases
with the increase in both pressure and appliedvoltage. In our experiment, time-averaged
effective power is 40-50W, whereas the maximumof instantaneous power reaches 10-15 kW.

(graphite) and D (disorder) peaks, are clearlyobserved in the Raman spectra. Typical example ofRaman spectroscopy is shown in Fig.5.

010p (mTorr)20

Fig 3 Relationship between the hardness and p,
where the magnitude of current is 12A.
20100010600
400

10V(t) (V)800

20i(t) (A)10Hardness (GPa)each indentation, the load versus displacement
curve is recorded, and then the film hardness isdetermined from the curve. Raman spectroscopy isused to obtain the structural information of thedeposited films. The Raman spectra are acquired ina range between 1000 and 2000 cm-1 and fitted bytwo Gaussian peaks.

01020Magnitude of current (A)20000

100200

Fig 4 Relationship between the hardness andthe magnitude of current, where p=5mTorr.

Fig 2 Typical example of voltage-current
waveforms, where pressure is 5mTorr.

The optical emission intensities emitted from theexcited Ar are predominant. The intensities emittedfrom CI and CII state cannot be clearly observed at
any conditions, because the time-averaged densitiesof CI and CII state are not so high.
Fig.3 shows the relationship between thehardness and the Ar pressure p, whereas therelationship between the hardness and themagnitude of pulsed current is shown in Fig. 4. As
shown in Fig.3, with increasing Ar pressure, thehardness of the films decreases from 15-17 GPa at
3mTorr to 9-10 GPa at 20mTorr. On the other hand,
the maximum of the hardness measured by ananoindenter increases with the magnitude ofpulsed current and reaches 17 GPa at 20 A. The
film hardness deposited at 20A is about two times
higher than that deposited by DC magnetron
sputtering.
For any deposited films, two, very broad
overlapping bands, which are attributed to the G

Raman Intensity (arb.unit)t (µs)
0.4

G

D

0.3
0.2
0.1
0800

1000

1200

1400

1600

1800-1

Raman Shift (cm )Fig 5 Typical example of Raman spectroscopy,
where magnitude of current =17A and p=5mTorr.

Acknowledgments
This work is partially supported by Grant-in-Aidfrom the Japan Society for the Promotion ofScience.
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Helmersson and I. Petrov, Surf. Coat. Technol. 122,(1999) 290.
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Ehiasarian and J. T. Gudmundsson, Thin Solid Films
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