Wüest M. 51 Wykes M. 82 Yamaguchi M. 17 Ybarra G. 129 Yubero F ...

JUNE 26 MONDAY AFTERNOON
RIVA-TF-MoA-OR.13 BREAKDOWN VOLTAGE IN MAGNETRON DC GLOW DIS-
CHARGES. THE INFLUENCE OF THE MAGNETIC FIELD. Y. Nunes, A. Wemans, P. R.
Gordo and M. J. P. Maneira. Cefitec - Department of Physics, Faculty of Sciences and Technology,
New University of Lisbon, P-2829-516, Caparica, PORTUGAL.
In abnormal glow discharges with magnetic field, the electrons are confined in a trap near the cathode
allowing work at lower pressures and voltages. For thin film applications this can influence positively
the quality of the sputtered film and decreases the processing time.
d
Fig1. Cathode mounted in the system
and the copper discharge on argon.
Fig2. Magnetic circuit position inside
the cathode body
In this work breakdown voltages of the abnormal glow discharges of argon on copper with magnetron
assistance, are measured for different magnetic configurations.
To achieve this, a cathode, shown in Fig.1, was constructed with a magnetic circuit, based on permanent
NdFeB, which can be systematically moved allowing fine control of magnetic field distribution,
see Fig.2. This way the influence of the magnetic field in the plasma parameters and in particular the
influences in the breakdown voltage are studied.
The breakdown voltages are measured and presented as a function of pressure for different distances
of the magnetic circuit to the target. The study takes in account a range of pressures from 0.2 to 32
Pa and a range of the parallel component of the magnetic induction, from 0.3 T to 1.7 T at the target
surface.
The expression,
V ( P)
= C ⋅e
B
1
P
−
C2
+ C + C ⋅ P
3
4
fits the data of breakdown voltage dependence on the working pressure, with high correlation coefficient
and the constants depend on magnetic distribution
At each magnetic configuration the first exponential term accounts for low pressure range and the
linear term accounts for the higher pressure range. Minima similar to what happens in Paschen’s
Law, are observed which shifts to lower pressure with increase of the magnetic field. This behavior
is systematic and regular.
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